Air Handling Units

Revision 8 · Aug 29, 2026 +2440 −1514

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)

Neutrality remake campaign: from-scratch field derivation per authoring cheatsheet; project parameters and derived dispositions

Showing changes from Rev 7 to Rev 8 in Air Handling Units.

−---

−title: Air Handling Units

−category: Mechanical / Air Distribution

−toc_depth: 3

−description: >

− When to use: Central station air handling units (AHUs) for commercial, institutional, and industrial buildings — both factory-built packaged units and field-erected built-up assemblies. Covers single-zone and multi-zone configurations, indoor and outdoor/weatherproof installations, constant-volume and variable-air-volume systems, and central-station units serving ductwork distribution. Applicable from small fan coil replacements through large mechanical room units.

− Not intended for: Unitary rooftop packaged units with integral refrigerant systems rated below 20 tons (see [[sync/packaged-rooftop-units]]); fan coil units and terminal units (see [[sync/fan-coil-units]]); dedicated outdoor air systems covered separately when paired with terminal sensible cooling; ductwork beyond the AHU connections ([[sync/hvac-ductwork]]); variable frequency drives for fan motors ([[sync/hvac-variable-frequency-drives]]); hydronic heating and cooling piping connected to coils ([[sync/hydronic-piping]]); testing, adjusting, and balancing after installation ([[sync/testing-adjusting-and-balancing]]); building automation system controls integration ([[sync/building-automation-system]]).

−---

−

−# Scope {toc}

−

−## This specification covers factory-assembled packaged and built-up central station air handling units (AHUs) for commercial, institutional, and industrial buildings. {note}

−## Equipment covered includes the casing, supply fan(s), return or relief fans where indicated, heating coils, cooling coils, energy recovery sections, filtration sections, mixing sections with outdoor/return/exhaust dampers, humidification provisions, access sections, drain pans, and vibration isolation systems. {note}

−## Both constant volume (CAV) and variable air volume (VAV) configurations are addressed. {note}

−

−## A central station AHU is distinguished from unitary terminal equipment by its dependence on a field-installed duct distribution system to deliver conditioned air to occupied zones. {note}

−## The unit is typically served by a central chilled water and hot water plant — see [[sync/hydronic-piping]] and [[sync/hvac-pumps]] for the associated piping and pump systems. {note}

−

−## Equipment shall comply with ANSI/AHRI 430 for performance rating of supply fans, AHRI 1350 for casing mechanical performance, AHRI 410 for coil performance ratings, ASHRAE 52.2 for filtration, ASHRAE 62.1 for outdoor air design, ASHRAE 90.1 for fan power and energy efficiency, NFPA 90A for fire and smoke safety, and UL 60335-2-40 (or UL 1995 where still accepted by the Authority Having Jurisdiction) for electrical safety listing.

−

−## The Contractor shall coordinate AHU installation with structural support design, hydronic and refrigerant piping connections, ductwork connections, electrical power and control wiring, drain piping, and vibration isolation requirements established in this standard.

−

−## Coordination with [[sync/building-automation-system]] is required for controls integration.

−

−## Fan speed regulation by variable frequency drives shall conform to [[sync/hvac-variable-frequency-drives]].

−

−# Referenced Standards {toc}

−

−## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.

−

−## Where conflicts exist between referenced standards, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.

−

−## Standards Table {toc}

−

−| Standard | Title |

−|----------|-------|

−| ANSI/AHRI 430 (I-P) | Performance Rating of Central Station Air-handling Unit Supply Fans |

−| ANSI/AHRI 1350 (I-P) | Mechanical Performance Rating of Central Station Air-handling Unit Casings |

−| ANSI/AHRI 410 | Performance Rating of Forced-Circulation Air-Cooling and Air-Heating Coils |

−| ANSI/ASHRAE 51 / AMCA 210 | Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating |

−| ANSI/AMCA 300 | Reverberation Room Methods of Sound Testing of Fans |

−| ANSI/AMCA 610 | Laboratory Methods of Testing Airflow Measurement Stations for Performance Rating |

−| ANSI/ASHRAE 52.2 | Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size |

−| ANSI/ASHRAE 62.1 | Ventilation and Acceptable Indoor Air Quality |

−| ANSI/ASHRAE/IES 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings |

−| NFPA 90A | Standard for the Installation of Air-Conditioning and Ventilating Systems |

−| UL 60335-2-40 | Safety of Household and Similar Electrical Appliances — Particular Requirements for Heat Pumps, Air-Conditioners, and Dehumidifiers |

−| UL 1995 | Heating and Cooling Equipment (where accepted by AHJ in lieu of UL 60335-2-40) |

−| IMC (International Mechanical Code) | International Mechanical Code, adopted edition |

−| SMACNA HVAC Duct Construction Standards | SMACNA HVAC Duct Construction Standards — Metal and Flexible |

−| ASHRAE Handbooks | HVAC Systems and Equipment, Fundamentals |

−

−# Submittals {toc}

−

−## Action Submittals {toc}

−

−### Contractor shall submit the following for review and acceptance prior to ordering equipment.

−

−- Manufacturer's product data sheets and catalog curves for each AHU, including unit model designation, configuration diagram, and component schedule

−- Fan performance curves plotted at the specified design point (CFM vs. static pressure) showing system resistance, fan curve, and operating point; curves shall include power consumption and efficiency at the design point and at minimum and maximum points if VAV

−- Fan sound power level data at the design operating point per AMCA 300, octave band sound power levels, and inlet and outlet radiation data where sound-critical spaces are adjacent

−- Motor data sheets including nameplate ratings, efficiency at 50%, 75%, and 100% load, power factor, and service factor

−- Coil selection data per AHRI 410 including entering and leaving conditions, face velocity, fin spacing, number of rows, tube diameter, and pressure drop on both airside and waterside

−- Filter section product data including MERV rating certification per ASHRAE 52.2, initial and final resistance, dust-holding capacity, and frame construction

−- Casing construction details showing panel construction, liner material and thickness, door gasket details, and access provisions; where AHRI 1350 certification is claimed, include certification documentation

−- Damper schedule showing blade type, frame dimensions, leakage class, actuator type, and close-off pressure differential rating

−- Drain pan drawings showing pan dimensions, slope, overflow provisions, material, and coating

−- Vibration isolation product data including static deflection, natural frequency, and isolation efficiency at the fan operating speed

−- Seismic restraint calculations and details where required by the applicable building code

−

−```datasheet

−label: Action Submittals Required

−type: checkbox

−options:

− - "Product data sheets and configuration diagrams"

− - "Fan performance curves at design point"

− - "Fan sound power levels (AMCA 300)"

− - "Motor data sheets with efficiency at multiple loads"

− - "Coil selection data (AHRI 410)"

− - "Filter MERV certification (ASHRAE 52.2)"

− - "Casing construction details"

− - "AHRI 1350 casing certification"

− - "Damper schedule with leakage class"

− - "Drain pan drawings"

− - "Vibration isolation product data"

− - "Seismic restraint calculations"

−default: "Product data sheets and configuration diagrams"

−```

−

−### Fabrication and procurement shall not proceed until action submittals have been reviewed and returned.

−

−## Closeout Submittals {toc}

−

−### Contractor shall provide the following at or before substantial completion:

−

−- Operation and maintenance manuals organized with table of contents, including manufacturer's installation, operation, and maintenance instructions for each AHU and all major components

−- As-built configuration drawings reflecting any field modifications to the submitted configuration

−- Factory test reports for each unit

−- Commissioning records from startup and functional testing

−- Belt and sheave selection data (for belt-driven fans) including design and installed sheave diameters and belt lengths

−- Filter media installed at time of substantial completion, including MERV certification and installation date tags

−- Warranty documentation from manufacturer and, where required, from filter and coil sub-suppliers

−

−```datasheet

−label: Required Closeout Submittals

−type: checkbox

−options:

− - "Operation and maintenance manuals"

− - "As-built configuration drawings"

− - "Factory test reports for each unit"

− - "Commissioning records from startup and functional testing"

− - "Belt and sheave selection data (belt-driven fans)"

− - "Installed filter media with MERV certification and date tags"

− - "Warranty documentation (manufacturer and sub-suppliers)"

−default: [Operation and maintenance manuals, As-built configuration drawings, Factory test reports for each unit, Commissioning records from startup and functional testing, Warranty documentation (manufacturer and sub-suppliers)]

−```

−

−# Quality Assurance {toc}

−

−## Manufacturer Qualifications {toc}

−

−### AHUs shall be manufactured by a company with a minimum of ten years of continuous experience designing and fabricating central station air handling equipment.

−

−### The manufacturer shall maintain an ISO 9001 certified quality management system.

−

−### The manufacturer shall be capable of providing replacement parts and service support for a minimum of fifteen years after the date of manufacture.

−

−## Single-Source Responsibility {toc}

−

−### For each air handling unit, the casing, fan(s), motor(s), coils, filters, dampers, and drain pan shall be provided by or through the air handling unit manufacturer as a coordinated factory assembly.

−

−### Mixing components from multiple independent suppliers into a field-erected assembly is not acceptable without Engineer approval.

−

−### Single-source supply ensures that structural, thermal, acoustical, and hydraulic interactions between components are resolved at the factory, not in the field. {note}

−

−## AHRI Certification {toc}

−

−```datasheet

−label: AHRI Certification Required

−type: checkbox

−options:

− - "Supply fan performance per AHRI 430"

− - "Coils per AHRI 410"

− - "Casing mechanical performance per AHRI 1350 (where manufacturer participates)"

−default: "Supply fan performance per AHRI 430"

−```

−

−### Supply fans in central station AHUs shall be rated under the AHRI Certification Program for Central Station Air-handling Unit Supply Fans per ANSI/AHRI 430.

−

−### Rated fan performance shall have been verified by an independent third-party laboratory contracted by AHRI.

−

−### Manufacturer's published fan curves and published performance data shall bear the AHRI certification mark.

−

−### Forced-circulation coils shall be rated under the AHRI Certification Program for Forced-Circulation Air-Cooling and Air-Heating Coils per ANSI/AHRI 410.

−

−### Published coil capacities, pressure drops, and selection data shall reflect AHRI-certified ratings.

−

−### Where the manufacturer participates in the AHRI Central Station Air-Handling Unit Casing Performance Certification Program (AHUC) under AHRI 1350, casing leakage, deflection, and thermal performance ratings shall be certified.

−

−### Certified casing ratings shall be documented in the submittal.

−

−## NRTL Listing {toc}

−

−### The complete AHU assembly, including all electrical components, shall be listed and labeled by a Nationally Recognized Testing Laboratory (NRTL) to UL 60335-2-40.

−

−### Where the AHJ continues to accept UL 1995 listings for equipment manufactured prior to the transition date, UL 1995-listed equipment is acceptable.

−

−### Electrical components not covered by the unit listing shall be individually listed to applicable UL or equivalent standards.

−

−## Pre-Installation Conference {toc}

−

−### A pre-installation conference shall be held before beginning AHU installation, attended by the Contractor, the mechanical sub-contractor, the controls sub-contractor, the Testing, Adjusting, and Balancing (TAB) agent, and the Owner's representative.

−

−### Conference agenda shall include unit rigging and setting sequence, utility connections, vibration isolation procedure, controls interface points, and the commissioning schedule.

−

−# Environmental and Service Conditions {toc}

−

−## AHUs shall be selected and rated for the anticipated operating conditions at the installation site.

−## The design conditions are [[drawing: as indicated on the mechanical schedules and psychrometric process diagrams]]. {note}

−

−## The equipment shall be capable of operating within the following envelope without damage, derating, or loss of function.

−

−## Ambient Conditions {toc}

−

−```datasheet

−label: Unit Installation Location

−type: select

−options:

− - "Indoor — conditioned mechanical room"

− - "Indoor — unconditioned mechanical room or penthouse"

− - "Outdoor — rooftop"

− - "Outdoor — grade-level with weatherproof casing"

− - "Built-up — field-erected in mechanical space"

−default: "Indoor — conditioned mechanical room"

−```

−

−### AHUs installed indoors in climate-controlled mechanical rooms shall be suitable for ambient temperatures from 40°F to 104°F (4°C to 40°C) and relative humidity from 10% to 95% non-condensing.

−

−### Outdoor and rooftop units shall be rated for the climate zone conditions applicable to the project location, including design winter ambient and design summer ambient as established by ASHRAE Fundamentals.

−

−### Outdoor units shall be provided with a factory-applied weatherproof casing meeting the requirements of this standard including pitched top panels or weather hoods over all openings, bird screens on air intakes and exhausts, drainable base rails, and all hardware in stainless steel or zinc-dichromate-treated steel.

−

−## Altitude Derating {toc}

−

−```datasheet

−label: Project Site Elevation

−type: range

−unit: ft above sea level

−options:

− min: 0

− max: 10000

− setpoints: [0, 1000, 2000, 3000, 4000, 5000, 6000, 8000, 10000]

−default: 0

−```

−

−### Where the project site is at an elevation above 3,000 ft (914 m), fan airflow, coil capacity, and filter resistance data shall be corrected for air density at the project altitude.

−

−### Altitude corrections shall be based on the project elevation and documented in the submittal.

−

−# Performance and Ratings {toc}

−

−## Design Airflow and Static Pressure {toc}

−

−```datasheet

−label: Supply Airflow

−type: range

−unit: CFM

−drawing_ref: true

−options:

− min: 1000

− max: 120000

− step: 500

−default: 10000

−```

−```datasheet

−label: Design External Static Pressure

−type: range

−unit: in. w.g.

−drawing_ref: true

−options:

− min: 0.5

− max: 8.0

− setpoints: [0.5, 0.75, 1.0, 1.25, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 8.0]

−default: 2.5

−```

−

−### Supply airflow, return airflow (where applicable), and design external static pressure (ESP) shall be [[drawing: as indicated on the mechanical schedules]].

−

−### Fan selection shall be made at the specified design point with a minimum 10% static pressure safety factor applied to the calculated system resistance unless the design documents specify otherwise.

−

−## Fan System Configuration {toc}

−

−### The fan system configuration determines how air is moved through the unit. {note}

−### Housed centrifugal fans with forward-curved, backward-curved, or airfoil blades are appropriate for ducted systems with moderate to high static pressure. {note}

−### Plenum fans (plug/plug-array) eliminate the fan scroll and discharge duct connection, providing a large plenum from which air distributes through the unit; plenum fans are commonly used in large central station AHUs where flexibility of downstream distribution is needed. {note}

−### Fan arrays (multiple smaller fans in parallel) provide redundancy and reduced sound levels compared to a single large fan. {note}

−

−### The supply fan configuration for each air handling unit shall be specified, weighing redundancy and sound level against a fan array where one is being considered.

−

−```datasheet

−label: Fan Configuration

−type: select

−options:

− - "Single housed centrifugal fan — direct drive"

− - "Single housed centrifugal fan — belt drive"

− - "Plenum fan (plug fan) — direct drive"

− - "Plenum fan (plug fan) — belt drive"

− - "Fan array (multiple plenum fans) — direct drive"

− - "Dual supply fans — parallel operation"

− - "Dual supply fans — standby redundancy"

−default: "Plenum fan (plug fan) — direct drive"

−```

−### Whether a return or relief fan is provided for each air handling unit, and its configuration, shall be specified.

−

−```datasheet

−label: Return/Relief Fan

−type: select

−options:

− - "None"

− - "Return fan — direct drive"

− - "Return fan — belt drive"

− - "Relief fan — direct drive"

− - "Relief fan — belt drive"

−default: "None"

−```

−

−### A return fan tracks supply fan airflow and is appropriate where building pressurization must be precisely controlled and where the return duct system has significant resistance. {note}

−

−### A relief fan exhausts air from the building when the economizer is in full free-cooling mode to maintain building pressure. {note}

−

−### In many commercial applications neither a return nor relief fan is required when the building is provided with transfer air paths and relief dampers. {note}

−

−## Fan Efficiency {toc}

−

−```datasheet

−label: ASHRAE 90.1 Fan Power Compliance Method

−type: radio

−options:

− - "Table 6.5.3.1-1 — Nameplate motor horsepower limit"

− - "Table 6.5.3.1-1 — Brake horsepower limit"

−default: "Table 6.5.3.1-1 — Brake horsepower limit"

−```

−```datasheet

−label: Fan Blade Type

−type: select

−options:

− - "Backward-curved airfoil (BC/AF) — highest efficiency, non-overloading"

− - "Backward-inclined (BI) — good efficiency, non-overloading"

− - "Forward-curved (FC) — compact, lower efficiency, overloading characteristic"

− - "Axial — inline applications"

−default: "Backward-curved airfoil (BC/AF) — highest efficiency, non-overloading"

−```

−

−### Fan efficiency shall comply with ASHRAE 90.1 Section 6.5.3.1.

−

−### Fan system brake horsepower at design conditions shall not exceed the allowable value from ASHRAE 90.1 Table 6.5.3.1-1 for the applicable fan system type and design flow rate.

−

−### All fan selections shall document compliance with the ASHRAE 90.1 fan power requirement in the submittal.

−

−### Fan static efficiency (FSE) at the design operating point shall be a minimum of 60% for housed airfoil and backward-inclined centrifugal fans, and a minimum of 55% for plenum fans.

−

−### Forward-curved fans are acceptable only for fan systems below 5,000 CFM where their lower efficiency is acceptable given reduced system size.

−

−### The efficiency requirement encourages backward-curved airfoil blade fans, which provide superior efficiency and non-overloading power characteristics compared to forward-curved wheels, and reduces the risk of motor overload as system resistance decreases with filter loading. {note}

−

−## Variable Air Volume Systems {toc}

−

−```datasheet

−label: Fan Volume Control

−type: select

−options:

− - "Constant volume — fixed speed"

− - "Variable air volume — variable frequency drive (VFD)"

− - "Variable air volume — inlet guide vanes (IGV)"

− - "Variable air volume — VFD and IGV combination"

−default: "Variable air volume — variable frequency drive (VFD)"

−```

−

−### For VAV systems, the fan shall be capable of stable operation from 100% design airflow down to the minimum required flow (typically 30–40% of design).

−

−### Variable frequency drives (VFDs) shall be provided for all fan motors 1 HP and larger on VAV systems per ASHRAE 90.1 Section 6.5.3.2.

−

−### Static pressure control strategy (duct static pressure reset, supply air temperature reset) shall be coordinated with the [[sync/building-automation-system]].

−

−### Inlet guide vanes are an older technology with higher installed cost and mechanical complexity compared to VFDs and should be used only where the Engineer has a specific technical justification.

−

−### VFDs provide superior energy performance at part-load conditions and are the standard selection for new construction. {note}

−

−# Casing Construction {toc}

−

−## Construction Type {toc}

−

−```datasheet

−label: Casing Panel Construction

−type: radio

−options:

− - "Double-wall — injected foam insulation between inner and outer skins"

− - "Double-wall — rigid board insulation with separate inner and outer skins"

− - "Double-wall — injected foam with metallic thermal break at panel edges"

− - "Single-wall — internally lined (heating service only)"

−default: "Double-wall — injected foam insulation between inner and outer skins"

−```

−

−### AHU casings shall be double-wall construction for all units with a cooling coil or in any application where the casing panels are subject to condensation on either side.

−

−### Single-wall construction is acceptable only for heating-only service in dry conditions.

−

−### Double-wall panels eliminate condensation on the exterior surface of the casing that would otherwise occur when supplying cooled or dehumidified air, and they prevent cold-bridging at panel edges and fasteners. {note}

−

−## Panel Material and Gauge {toc}

−

−```datasheet

−label: Interior Casing Liner Material

−type: select

−options:

− - "G90 galvanized steel with factory-applied coating"

− - "Type 304 stainless steel"

− - "Aluminum (painted)"

− - "Galvanized steel — heating sections only (no condensate)"

−default: "G90 galvanized steel with factory-applied coating"

−```

−```datasheet

−label: Panel Thermal Value (R-value)

−type: select

−unit: hr·ft²·°F/Btu

−options:

− - "R-3 (minimum, small units)"

− - "R-4 to R-5 (commercial standard)"

− - "R-6 to R-8 (energy-conscious and cold climate)"

− - "R-10 to R-13 (arctic or dedicated outdoor air)"

−default: "R-4 to R-5 (commercial standard)"

−```

−

−### Exterior panel skins shall be minimum 18-gauge (1.2 mm) galvanized steel meeting ASTM A653 with G90 zinc coating.

−

−### Interior panel skins that may be wetted by condensate in the cooling and cooling coil sections shall be stainless steel, galvanized steel with a factory-applied interior coating, or aluminum.

−

−### Galvanized steel interior skins shall not be used without a factory-applied coating resistant to the condensate pH range of 5 to 9.

−

−## Casing Leakage Class {toc}

−

−```datasheet

−label: Casing Air Leakage Class (AHRI 1350)

−type: select

−options:

− - "L1 — Tightest (less than 0.5% of design airflow at design pressure)"

− - "L2 — Standard commercial (less than 1.0% of design airflow)"

− - "L3 — General purpose (less than 2.0% of design airflow)"

−default: "L2 — Standard commercial (less than 1.0% of design airflow)"

−```

−

−### Casing air leakage rate shall comply with AHRI 1350.

−

−### Casing leakage class shall be selected based on operating pressure and energy classification.

−

−### Excessive casing leakage wastes energy in supply sections (conditioned supply air leaking to the mechanical room) and causes infiltration of unconditioned air into the return section (negating dehumidification accomplished in the cooling coil). {note}

−

−### For units operating above 4 in. w.g. internal static pressure, tighter leakage classes are required to prevent significant efficiency degradation.

−

−## Casing Deflection Class {toc}

−

−```datasheet

−label: Casing Panel Deflection Class (AHRI 1350)

−type: select

−options:

− - "D1 — Stiffest (less than L/400 at design pressure)"

− - "D2 — Standard (less than L/200 at design pressure)"

− - "D3 — General purpose (less than L/100 at design pressure)"

−default: "D2 — Standard (less than L/200 at design pressure)"

−```

−

−### Panel deflection under operating pressure shall comply with AHRI 1350.

−

−### Excessive panel deflection degrades seals, allows door gaps to open, and indicates inadequate structural stiffness that may cause panel-to-panel joint leakage over time. {note}

−

−## Access Doors and Sections {toc}

−

−```datasheet

−label: Access Door Hardware

−type: radio

−options:

− - "Hinged with cam-type quarter-turn latches, interior and exterior handles"

− - "Hinged with cam-type latches, interior handle only"

− - "Sliding panel (where space prevents door swing)"

−default: "Hinged with cam-type quarter-turn latches, interior and exterior handles"

−```

−

−### Access doors shall be provided at each major component section: fan section, filter sections, coil sections, mixing box, drain pan, and humidifier where provided.

−

−### Minimum door clear opening shall be 18 in. wide by 18 in. tall for maintenance access; where component replacement (coil pull, fan wheel replacement) is required through the door, the opening shall be sized accordingly.

−

−### Doors shall be hinged, gasketed, and equipped with cam-type latches that open with a standard tool.

−

−### Door hinges shall be stainless steel or zinc-plated steel.

−

−### Access doors within systems handling classified air (e.g., laboratory exhaust, healthcare critical spaces) shall include provisions for viewing the interior without entering the airstream by a gasketed glass port or a sealed transparent panel in the door.

−

−## Interior Liner Attachment {toc}

−

−### Interior panel liners shall be attached so that fasteners or standoffs penetrating the insulation layer do not create thermal bridges at the inner surface.

−

−### All exposed fasteners on interior surfaces that may contact the airstream shall be stainless steel.

−

−### The liner system shall be rated for the velocity and turbulence of the airstream so that individual liner panels or facing materials do not become dislodged during normal operation, including any transient high-velocity conditions during filter change or access door operation.

−

−## Exterior Finish {toc}

−

−```datasheet

−label: Exterior Finish Color

−type: text

−default: "Manufacturer's standard gray"

−```

−

−### Exterior panels of indoor units shall receive a manufacturer's standard electrostatically applied powder coat finish in a color as selected by the Owner.

−

−### Outdoor units shall receive a minimum two-coat system consisting of a corrosion-inhibiting epoxy primer and a UV-resistant polyester powder coat topcoat with a minimum total dry film thickness of 3 mils.

−

−### All cut edges, fasteners, and casing penetrations on outdoor units shall receive zinc-rich touch-up coating prior to final assembly.

−

−# Fans and Motors {toc}

−

−## Fan Section Construction {toc}

−

−```datasheet

−label: Fan Wheel Material

−type: select

−options:

− - "Steel — painted"

− - "Steel — galvanized"

− - "Steel — epoxy coated"

− - "Aluminum"

− - "Stainless steel (corrosive or high-moisture applications)"

−default: "Steel — painted"

−```

−

−### Fan sections shall be structurally isolated from the casing by flexible fan-section isolators or by mounting the fan assembly on internal spring isolators within the casing, so that fan vibration is not transmitted to the casing panels.

−

−### Fan wheel, housing, shaft, and bearings shall be factory assembled and dynamically balanced per AMCA standards before shipment.

−

−### Fans shall be tested and rated per ANSI/ASHRAE 51 / ANSI/AMCA 210.

−

−### Fan wheels shall be fabricated from steel or aluminum and shall be finish-coated to resist corrosion in the expected airstream conditions.

−

−### Where the airstream contains elevated moisture, corrosive gases, or particulates, fan wheel and housing materials and coating shall be appropriate for the specific conditions per the manufacturer's material selection guide.

−

−## Fan Bearings {toc}

−

−```datasheet

−label: Bearing Type and Access

−type: select

−options:

− - "Heavy-duty regreasable — extended lube fittings to casing exterior"

− - "Heavy-duty regreasable — accessible from within fan section"

− - "Sealed premium-life bearings — maintenance-free (direct drive only)"

−default: "Heavy-duty regreasable — extended lube fittings to casing exterior"

−```

−

−### Fan shaft bearings shall be heavy-duty ball or roller type, selected for a minimum L10 bearing life of 200,000 hours at design operating conditions per AFBMA standards.

−

−### Bearings shall be regreasable with grease fittings extended to the exterior of the fan section for accessibility without opening the casing during routine maintenance.

−

−### Sealed, non-regreasable bearings are acceptable only for direct-drive plenum fans with motors integral to the fan assembly where the motor bearings meet the L10 life requirement.

−

−## Belt Drive Systems {toc}

−

−```datasheet

−label: Belt Drive Configuration

−type: select

−options:

− - "V-belt — classical or narrow groove"

− - "Synchronous (cogged) belt — no slippage, suitable for precise speed"

− - "Direct drive — no belt (motor directly coupled to fan shaft or integral motor)"

−default: "Direct drive — no belt (motor directly coupled to fan shaft or integral motor)"

−```

−

−### Where belt-driven fans are specified, sheaves and belts shall be V-belt or synchronous belt type.

−

−### V-belt drive systems shall include an adjustable motor base for belt tensioning and sheave alignment.

−

−### Sheaves shall be sized for the design fan speed with capacity to reduce or increase speed by changing sheaves; the motor and fan sheave combination shall be indicated in the submittal and shall be verified to produce the specified fan speed within ±5% without exceeding the motor nameplate horsepower under any anticipated system operating condition.

−

−### Where variable speed is required on belt-driven fans, the combination of belt drive ratio and VFD frequency range shall be selected so that the fan operates at the required airflow range without exceeding the motor service factor or the fan manufacturer's maximum allowable speed.

−

−## Fan Motor {toc}

−

−```datasheet

−label: Motor Enclosure Type

−type: select

−options:

− - "Totally Enclosed Fan Cooled (TEFC)"

− - "Open Drip Proof (ODP) — indoor conditioned spaces only"

− - "Totally Enclosed Air Over (TEAO)"

− - "Explosion-proof (hazardous locations)"

−default: "Totally Enclosed Fan Cooled (TEFC)"

−```

−```datasheet

−label: Motor Efficiency Class

−type: radio

−options:

− - "Premium efficiency (NEMA Premium / IE3)"

− - "Standard efficiency (not recommended for new construction)"

−default: "Premium efficiency (NEMA Premium / IE3)"

−```

−```datasheet

−label: Motor Voltage

−type: select

−options:

− - "208V / 3-phase"

− - "460V / 3-phase"

− - "575V / 3-phase"

− - "120V / 1-phase (small units only)"

− - "208V / 1-phase (small units only)"

−default: "460V / 3-phase"

−```

−```datasheet

−label: Motor Horsepower (Supply Fan)

−type: range

−unit: HP

−drawing_ref: true

−options:

− min: 0.5

− max: 150

− setpoints: [0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 5.0, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150]

−default: 15

−```

−

−### Fan motors shall be premium efficiency, totally enclosed fan-cooled (TEFC) or open drip-proof (ODP) for indoor installations, inverter-duty rated for variable speed applications per NEMA MG1 Part 31.

−

−### Motor voltage and phase shall match the electrical service at the unit.

−

−### Inverter-duty motors are required for all VFD applications to withstand the voltage spikes and harmonic content of the inverter output; standard motors may fail prematurely when operated on VFD power.

−

−### Motor horsepower shall be [[drawing: as indicated on the mechanical schedules]].

−

−### Motor service factor shall be a minimum of 1.15 for belt-driven fans and 1.0 for direct-drive fans selected at or below the nameplate horsepower.

−

−### Motors shall be selected so that the nameplate horsepower is not exceeded at any point on the fan curve within the normal operating range.

−

−## Variable Frequency Drives {toc}

−

−### VFDs for AHU fan motors shall conform to [[sync/hvac-variable-frequency-drives]].

−

−### Where VFDs are factory-mounted in the AHU electrical control panel, the panel location shall be outside the airstream and accessible without interrupting unit operation.

−

−### VFD bypass capability (manual or automatic) shall be provided where indicated on the drawings.

−

−## Fan Sound Performance {toc}

−

−```datasheet

−label: Fan Sound Rating Method

−type: radio

−options:

− - "AMCA 300 octave band sound power levels — submitted with product data"

− - "AMCA certified sound power — included in AHRI certification"

−default: "AMCA 300 octave band sound power levels — submitted with product data"

−```

−

−### Fan sound power levels shall be documented at the design operating point per ANSI/AMCA 300 in each of the eight octave bands from 63 Hz to 8,000 Hz.

−

−### Inlet and outlet radiation levels shall be reported separately.

−

−### Where the AHU is adjacent to acoustically sensitive spaces, the design team shall perform a sound transmission analysis using the submitted octave band data, the duct attenuation path, and the room correction to confirm that the resulting room noise criterion (NC) complies with the project acoustic requirements.

−

−# Coils {toc}

−

−## General Coil Requirements {toc}

−

−```datasheet

−label: Coil Tube Material

−type: radio

−options:

− - "Copper tubes with aluminum fins (standard)"

− - "Copper tubes with copper fins (corrosive coastal environments)"

− - "Stainless steel tubes with aluminum fins (corrosive airstreams)"

− - "Copper tubes with phenolic-coated aluminum fins (coastal/chemical)"

−default: "Copper tubes with aluminum fins (standard)"

−```

−

−### Coils shall be factory-installed in the AHU casing with proper tube orientation (water supply and return connections at the same end of the unit for counterflow arrangement), adequate drain connections at the lowest point of each coil circuit, and vent connections at the highest point.

−

−### Coils shall be removable from the unit without cutting tubes or disassembling adjacent sections; coil pull-out clearance shall be shown on the submittal drawings.

−

−### All coils shall be rated and certified per ANSI/AHRI 410.

−

−### Published ratings shall reflect the actual installed conditions (face velocity, entering conditions, fluid flow rate) and not generic catalog selections.

−

−### The submittal shall include AHRI-certified coil selection data.

−

−### Fin material selection matters in coastal and chemically aggressive environments. Aluminum fins in salt-laden air corrode over time, reducing heat transfer and increasing airside pressure drop. Phenolic-coated aluminum fins or copper fins provide substantially longer service life at modest added cost and are recommended for installations within approximately 3 miles of a saltwater coast or in industrial air environments. {note}

−

−## Cooling Coils {toc}

−

−```datasheet

−label: Cooling Coil Type

−type: radio

−options:

− - "Chilled water (CHW) — hydronic"

− - "Direct expansion (DX) — refrigerant"

−default: "Chilled water (CHW) — hydronic"

−```

−```datasheet

−label: Chilled Water Entering/Leaving Temperature

−type: text

−drawing_ref: true

−default: "44°F EWT / 56°F LWT (typical; see mechanical schedules)"

−```

−```datasheet

−label: Cooling Coil Face Velocity

−type: range

−unit: FPM

−options:

− min: 300

− max: 550

− setpoints: [300, 350, 400, 450, 500, 550]

−default: 450

−```

−```datasheet

−label: Chilled Water Pressure Drop (Coil Waterside)

−type: range

−unit: ft w.g.

−options:

− min: 2

− max: 30

− step: 1

−default: 15

−```

−

−### Cooling coils shall be hydronic chilled water type unless the contract documents indicate a direct-expansion (DX) refrigerant coil.

−

−### Chilled water coils shall be designed for counterflow water circuit arrangement (water enters the leaving air end of the coil, exits the entering air end) to maximize log-mean temperature difference and minimize required coil surface.

−

−### Face velocity for cooling coils shall not exceed 550 FPM at design conditions to control moisture carryover.

−

−### A maximum face velocity of 500 FPM is recommended for standard applications; 450 FPM provides margin for moisture control and is appropriate where the unit handles high sensible loads with relatively little latent cooling.

−

−### Exceeding 550 FPM reliably causes water carryover downstream regardless of drain pan depth. {note}

−

−### Chilled water coils shall include a factory-installed manual air vent and drain valve at the coil header connections.

−

−### All chilled water coil connections shall exit the casing through properly gasketed, insulated penetrations to prevent casing sweating at the pipe stub-outs.

−

−### See [[sync/hydronic-piping]] for piping connection requirements.

−

−## Hot Water Heating Coils {toc}

−

−```datasheet

−label: Heating Coil Type

−type: select

−options:

− - "Hot water (HW) hydronic"

− - "Steam — distributing type (constant steam distribution at all loads)"

− - "Electric resistance — finned tubular"

− - "None — heating provided by VAV reheat at terminal units only"

−default: "Hot water (HW) hydronic"

−```

−```datasheet

−label: Heating Coil Hot Water Design Temperature

−type: text

−drawing_ref: true

−default: "180°F EWT / 160°F LWT (typical; see mechanical schedules)"

−```

−

−### Heating coils shall be hot water hydronic type unless the contract documents indicate electric or steam.

−

−### Hot water coils shall be single- or multi-row as required by the design conditions.

−

−### Where steam heating coils are used, they shall be the distributing (non-freeze) type with a steam trap and float-and-thermostatic condensate return on every circuit.

−

−### Non-distributing steam coils freeze and fail catastrophically when low steam pressure allows coil condensate to collect; distributing coils circulate steam to every tube regardless of load and are the only safe choice in freezing climates. {note}

−

−## Energy Recovery Coils {toc}

−

−```datasheet

−label: Energy Recovery Type

−type: select

−options:

− - "None"

− - "Runaround coil loop (glycol) — separate supply and exhaust coils"

− - "Sensible-only rotary heat wheel with purge sector"

− - "Total energy (enthalpy) rotary heat wheel"

− - "Fixed-plate heat exchanger — cross-flow or counter-flow"

−default: "None"

−```

−

−### Where heat recovery is indicated on the drawings, the AHU shall include a runaround coil loop (glycol coils in supply and exhaust airstreams connected by a pumped circuit) or a heat wheel (rotary energy recovery wheel).

−

−### Heat wheels shall be the aluminum-media or silica-gel-coated (total energy) type, selected for the project climate and application.

−

−### Where cross-contamination between exhaust and supply airstreams is a concern (healthcare, laboratory), heat wheels shall be the sensible-only type with a purge sector, or runaround coil loops shall be used instead.

−

−# Filtration {toc}

−

−## Filter Sections and MERV Ratings {toc}

−

−```datasheet

−label: Pre-filter MERV Rating

−type: select

−options:

− - "None (single-stage filtration only)"

− - "MERV 4 — fiberglass panel, minimal resistance"

− - "MERV 7 — synthetic media panel, standard pre-filter"

− - "MERV 8 — extended surface pleated media"

−default: "MERV 7 — synthetic media panel, standard pre-filter"

−```

−```datasheet

−label: Final Filter MERV Rating

−type: select

−options:

− - "MERV 8 — minimum for commercial occupied spaces"

− - "MERV 11 — good commercial, some healthcare support"

− - "MERV 13 — enhanced particulate removal, general healthcare, LEED EQ credits"

− - "MERV 14 — superior filtration, critical healthcare support spaces"

− - "MERV 16 — high efficiency, approaching HEPA performance"

− - "HEPA (H13/H14) — required for operating rooms, isolation, critical biocontainment"

−default: "MERV 13 — enhanced particulate removal, general healthcare, LEED EQ credits"

−```

−

−### Air filtration shall comply with ASHRAE 52.2.

−

−### At minimum, all supply air to occupied spaces shall pass through filtration with MERV 8 efficiency upstream of the cooling coil.

−

−### Filtration requirements are determined by the application, the occupancy type, and any energy code or green building certification requirements. Pre-filtration upstream of higher-efficiency final filters extends filter life by removing larger particles before they load the primary filter. {note}

−

−### MERV 13 is the current recommendation for general commercial and institutional buildings under ASHRAE 62.1 guidance for improved indoor air quality. MERV 13 filters capture the fine particulate range (PM2.5 aerosols and biological aerosols) that lower MERV filters pass. The increased airside pressure drop at MERV 13 compared to MERV 8 (typically 0.3 to 0.5 in. w.g. additional at final pressure) must be accounted for in fan selection and power calculations. {note}

−

−### HEPA filtration shall be provided with separate sealed filter housings with integral bag-in/bag-out change-out provisions in healthcare and laboratory applications to protect maintenance personnel from contaminants captured in the filter.

−

−### Standard slide-in filter frames are not acceptable for HEPA installations.

−

−## Filter Housing Construction {toc}

−

−```datasheet

−label: Filter Frame Seal Type

−type: select

−options:

− - "Positive seating with spring latches — no adhesive required"

− - "Fluid-gel or knife-edge seal — individual filter cells"

− - "Bag-in/bag-out — sealed housings for HEPA or hazardous applications"

−default: "Positive seating with spring latches — no adhesive required"

−```

−

−### Filter housings shall be formed from galvanized steel with continuous, rigid filter-holding frames that prevent air bypass around the filter media.

−

−### Frame-to-filter seal shall be achieved by positive contact pressure (spring-loaded or draw-bolt latch) and not by friction fit alone.

−

−### Air bypass around filter media is the most common filtration deficiency in installed systems and results in effective MERV ratings well below the nominal rating of the filter media. {note}

−

−## Filter Change Access {toc}

−

−```datasheet

−label: Filter Access Direction

−type: radio

−options:

− - "Side access — filter slides out laterally through access door"

− - "Front access — filter slides forward through front panel"

− - "Top access — filter lifts out through top panel (ground-level units)"

−default: "Side access — filter slides out laterally through access door"

−```

−

−### Filter housings shall permit filter change without tools.

−

−### Filters shall be accessible from the side of the unit without entering the unit or removing adjacent sections.

−

−### Where side access is not possible due to mechanical room constraints, access shall be from the front with full coil withdrawal clearance maintained.

−

−### Filter change frequency and disposal requirements shall be documented in the O&M manuals.

−

−## Filter Gauges and Monitoring {toc}

−

−```datasheet

−label: Filter Differential Pressure Indication

−type: select

−options:

− - "Magnahelic gauge — local indication only"

− - "Digital display gauge — local indication only"

− - "Differential pressure transmitter — BAS integration"

− - "Both local gauge and DP transmitter"

−default: "Both local gauge and DP transmitter"

−```

−

−### Magnahelic or digital differential pressure gauges shall be provided across each filter section.

−

−### Gauge ports shall be located upstream and downstream of the filter media.

−

−### The gauge shall be externally visible without opening the unit.

−

−### Where the BAS monitors filter differential pressure, pressure taps shall be provided for connection to a differential pressure transmitter.

−

−### Initial pressure drop and final (loaded) pressure drop (change-out pressure) for each filter section shall be submitted with the product data.

−

−### Each filter section shall be sized so that at the final pressure drop the total fan system static pressure does not exceed the fan curve at the minimum speed setpoint for VAV systems, or does not reduce airflow below design for CAV systems.

−

−# Dampers and Economizer {toc}

−

−## Mixing Section {toc}

−

−```datasheet

−label: Mixing Box Configuration

−type: select

−options:

− - "OA + RA + EA — full economizer capable mixing box"

− - "OA + RA only — no exhaust/relief (building relief through separate path)"

− - "Dedicated outdoor air — OA only, no return air mixing"

− - "None — no outdoor air through this unit"

−default: "OA + RA + EA — full economizer capable mixing box"

−```

−

−### AHUs serving outdoor air ventilation requirements shall include a mixing box section with a minimum of three dampers: outdoor air (OA) damper, return air (RA) damper, and exhaust air (EA) damper or relief air damper.

−

−### Damper blades shall be multi-blade, opposed-blade or parallel-blade type as appropriate for the control application.

−

−### Opposed-blade dampers provide more linear flow characteristics across the damper operating range and are preferred for modulating applications.

−

−## Outdoor Air Damper {toc}

−

−```datasheet

−label: Outdoor Air Minimum Control Method

−type: select

−options:

− - "Separate minimum OA damper (small, sized for minimum OA flow)"

− - "Modulating OA damper with minimum position stop"

− - "Airflow measurement station in OA duct — controlled for OA flow setpoint"

− - "CO2-based demand-controlled ventilation reset"

−default: "Airflow measurement station in OA duct — controlled for OA flow setpoint"

−```

−

−### The outdoor air damper shall be sized for the design maximum outdoor air quantity as required by ASHRAE 62.1 and shall be capable of modulating down to the design minimum outdoor air flow while maintaining proportional control.

−

−### A minimum position stop or a separate minimum outdoor air damper shall be provided for accurate minimum outdoor air control.

−

−### A minimum outdoor air damper sized only for the minimum required ventilation flow provides far better control authority at minimum position than a full-size OA damper modulated to a nearly closed position, because a large damper at a small opening has highly nonlinear and unstable flow characteristics. {note}

−

−### An airflow measurement station in the outdoor air duct provides direct measurement of outdoor air quantity, enabling accurate compliance with ASHRAE 62.1 ventilation requirements regardless of system pressure variations. Damper position minimum stops without airflow measurement rely on calibrated conditions that drift as systems age and are not recommended where accurate minimum OA control is required. {note}

−

−## Damper Performance {toc}

−

−```datasheet

−label: Outdoor Air Damper Leakage Class

−type: radio

−options:

− - "AMCA Class I — less than 2 CFM/ft² at 1 in. w.g. (tight shutoff, cold climates)"

− - "AMCA Class II — less than 4 CFM/ft² at 1 in. w.g. (standard)"

−default: "AMCA Class I — less than 2 CFM/ft² at 1 in. w.g. (tight shutoff, cold climates)"

−```

−

−### All dampers shall be low-leakage type, rated at no more than 4 CFM per square foot at 1 in. w.g. differential pressure (AMCA Class II or better).

−

−### For tight shut-off applications (outdoor air dampers in cold climates where freezing of standing water in the mixing box is a concern), AMCA Class I dampers (less than 2 CFM/ft² at 1 in. w.g.) shall be specified.

−

−### Damper blade seals shall be extruded vinyl or silicone rated for the expected temperature range; felt seals shall not be used.

−

−## Damper Actuators {toc}

−

−```datasheet

−label: Damper Actuator Type

−type: select

−options:

− - "Electronic modulating — 0-10V or 4-20mA signal"

− - "Electronic two-position (open/close)"

− - "Pneumatic modulating (existing pneumatic systems)"

−default: "Electronic modulating — 0-10V or 4-20mA signal"

−```

−

−### Damper actuators shall be direct-coupled, spring-return type for fail-safe operation.

−

−### OA dampers shall fail closed (spring-return to closed) on loss of control signal or power to protect the unit from freeze damage.

−

−### Return air dampers shall fail open to maintain airflow through the unit during the same failure condition.

−

−## Economizer {toc}

−

−```datasheet

−label: Economizer Changeover Control Strategy

−type: select

−options:

− - "Differential dry-bulb temperature — OA temp below RA temp"

− - "Fixed dry-bulb — OA below fixed setpoint (e.g., 65°F)"

− - "Differential enthalpy — OA enthalpy below RA enthalpy"

− - "Fixed enthalpy — OA enthalpy below fixed setpoint"

− - "No economizer"

−default: "Differential dry-bulb temperature — OA temp below RA temp"

−```

−

−### Where an economizer is required by ASHRAE 90.1 Section 6.5.1 or by the applicable energy code, the AHU shall be capable of modulating the OA damper to 100% outdoor air for free cooling when outdoor air conditions are favorable.

−

−### Economizer controls shall include a changeover control strategy (dry-bulb temperature, differential dry-bulb, enthalpy, or differential enthalpy) as specified.

−

−### Differential enthalpy control provides the widest range of economizer operation and the greatest energy savings in humid climates, but requires enthalpy sensors that require calibration and maintenance. Differential dry-bulb control is simpler and more reliable in dry climates. {note}

−

−### The design team shall select the changeover strategy appropriate for the climate zone and Owner's maintenance program.

−

−# Drain Pans and Condensate {toc}

−

−## Drain Pan Construction {toc}

−

−```datasheet

−label: Drain Pan Material

−type: radio

−options:

− - "Type 304 stainless steel — all condensing sections"

− - "Type 316 stainless steel — coastal or chemical environments"

− - "Coated carbon steel — heating sections only (no condensate)"

−default: "Type 304 stainless steel — all condensing sections"

−```

−

−### A drain pan shall be installed below every cooling coil section, humidifier section, and any other section where condensate may form.

−

−### The drain pan is one of the most common sources of Legionella growth in air handling equipment; a well-designed drain pan that fully drains after each operating cycle eliminates the stagnant water condition that promotes biological growth. {note}

−

−### Drain pans shall be stainless steel (Type 304 minimum) for the section directly below the cooling coil, where condensate is most active.

−

−### Painted or galvanized carbon steel pans are not acceptable below cooling coils because the coating is abraded by condensate drip impact and corrosion begins within a few years of service.

−

−## Drain Pan Sizing and Slope {toc}

−

−```datasheet

−label: Drain Pan Slope

−type: radio

−options:

− - "1/8 in./ft minimum toward single drain"

− - "1/4 in./ft toward single drain (preferred)"

− - "1/8 in./ft with multiple drain connections at each low point"

−default: "1/4 in./ft toward single drain (preferred)"

−```

−

−### The drain pan shall extend beyond the coil face on the downstream (leaving air) side by a minimum of 2 in. for every foot of coil height, but not less than 6 in.

−

−### The downstream extension captures condensate that is entrained in the airstream and blown past the coil before it falls. An undersized pan allows condensate to reach the fan section and downstream ductwork, promoting biological growth throughout the distribution system. {note}

−

−### Drain pan floors shall be sloped a minimum of 1/8 in. per foot toward the drain connection.

−

−### Where the unit configuration results in a drain pan with multiple low points, individual drain connections shall be provided at each low point.

−

−### Flat-bottomed drain pans that do not fully drain create the standing water conditions that promote biological contamination and are not acceptable.

−

−## Drain Connection and Trap {toc}

−

−```datasheet

−label: Condensate Trap Location

−type: radio

−options:

− - "Factory-installed trap integral to unit base"

− - "Field-installed trap — trap depth specified by Engineer on drawings"

−default: "Field-installed trap — trap depth specified by Engineer on drawings"

−```

−

−### The drain pan shall have a primary drain connection and a secondary overflow drain connection located 1 in. above the primary drain to indicate drain obstruction before overflow occurs.

−

−### Drain connections shall be a minimum of 1 in. IPS or as required to handle the design condensate rate, whichever is greater.

−

−### A condensate trap shall be provided on the drain line.

−

−### The trap seal depth shall be calculated based on the static pressure in the drain pan section.

−

−### A trap sized for gravity drainage but located in a negative-pressure section, if the trap seal is shallower than the negative pressure head, is emptied so that unconditioned air (or sewer gas if connected to a drain with a P-trap) is drawn directly into the unit. {note}

−

−### Minimum trap seal depth in inches shall equal the negative static pressure at the drain pan in inches w.g. plus 2 in.

−

−### For typical cooling coil sections operating at -1.0 to -2.0 in. w.g., the trap shall have a minimum seal depth of 3 to 4 in.

−

−# Vibration Isolation {toc}

−

−## Isolation Requirements {toc}

−

−```datasheet

−label: Vibration Isolation Type

−type: select

−options:

− - "Spring floor mounts — housed fans and base-mounted units"

− - "Spring hanger isolators — suspended units"

− - "Inertia base with spring mounts — high vibration applications or near sensitive spaces"

− - "Elastomeric (rubber) mounts — small units below 1 HP"

− - "None — direct-mount on isolated concrete pad only"

−default: "Spring floor mounts — housed fans and base-mounted units"

−```

−

−### Fan sections shall be isolated from the casing structure to prevent transmission of fan vibration into the building structure.

−

−### The isolation system shall be selected to achieve a minimum vibration isolation efficiency of 90% at the lowest fan operating speed for VAV systems, or at the fan design speed for CAV systems.

−

−### AHUs mounted on the ground floor slab shall be isolated from the slab by floor-mounted spring isolators.

−

−### AHUs suspended from structural members above shall use hanger spring isolators.

−

−### AHUs mounted on grade-level concrete pads do not require vibration isolation unless the pad is isolated from the building structure.

−

−## Static Deflection {toc}

−

−```datasheet

−label: Spring Isolator Static Deflection

−type: select

−unit: inches

−options:

− - "0.75 in. (fans above 1,800 RPM only)"

− - "1.0 in. (fans above 1,200 RPM)"

− - "1.5 in. (fans 900–1,200 RPM)"

− - "2.0 in. (fans 600–900 RPM)"

− - "3.0 in. (fans below 600 RPM, or near sensitive spaces)"

−default: "2.0 in. (fans 600–900 RPM)"

−```

−

−### Spring isolators shall be selected for the minimum static deflection required to achieve the specified isolation efficiency.

−

−### For fans operating at 600 to 1,200 RPM (typical belt-drive fan speed range), a minimum static deflection of 2 inches is required.

−

−### For fans operating above 1,200 RPM (typical direct-drive plenum fan speed), 1.5 inches deflection is generally sufficient.

−

−### Spring isolators shall be selected so that the installed operating load is within the load range for which the spring is rated; overloaded or underloaded springs may exhibit resonance or instability.

−

−## Flexible Connections {toc}

−

−```datasheet

−label: Flexible Duct Connection Material

−type: radio

−options:

− - "Double-ply neoprene-coated fabric"

− - "Single-ply treated canvas"

− - "Composite elastomeric — UL 181 Class 1 listed"

−default: "Double-ply neoprene-coated fabric"

−```

−

−### All connections to an isolated AHU — ductwork, piping, electrical conduit, and condensate drain — shall be made with flexible connections to prevent short-circuiting the isolation system.

−

−### A single rigid connection from the isolated unit frame to the building structure transmits vibration as effectively as no isolation at all, negating the investment in isolators. {note}

−

−### Supply and return ductwork shall connect to the AHU through flexible canvas or elastomeric connectors of minimum 6 in. clear length.

−

−### Hydronic piping shall connect through flexible pipe connectors with a minimum of two flexible connectors in different planes.

−

−### Electrical conduit shall use flexible conduit for a minimum of 18 in. at the unit.

−

−### The condensate drain shall use a flexible coupling at the unit connection.

−

−## Seismic Restraint {toc}

−

−```datasheet

−label: Seismic Restraint Required

−type: radio

−options:

− - "Yes — per ASCE 7 and applicable building code"

− - "No"

−default: "No"

−```

−

−### Where required by the applicable building code (IBC/ASCE 7) based on the seismic design category, AHUs shall be provided with seismic restraints.

−

−### Seismic restraints shall be designed to accommodate the required seismic forces while allowing the isolators to continue functioning in normal operation.

−

−# Controls Interface {toc}

−

−## Controls Integration {toc}

−

−```datasheet

−label: BAS Communication Protocol

−type: select

−options:

− - "BACnet MS/TP (RS-485)"

− - "BACnet IP (Ethernet)"

− - "Modbus RTU (RS-485)"

− - "Modbus TCP/IP (Ethernet)"

− - "LonWorks (FT-10)"

− - "Hardwired (analog and digital I/O only — no network)"

−default: "BACnet IP (Ethernet)"

−```

−

−### AHUs shall be provided with factory-installed controls wiring and terminal strips for all field control connections.

−

−### Factory wiring shall terminate at a central terminal block or junction box accessible without opening the main unit.

−

−### All control terminations shall be labeled to match the control sequence documentation.

−

−### The AHU controls interface shall be compatible with the project building automation system (BAS) per [[sync/building-automation-system]].

−

−### Contractor shall coordinate communications protocol and physical interface points with the BAS contractor prior to submittal.

−

−## Minimum Control Points {toc}

−

−### At minimum, the AHU controls interface shall include the following points, all accessible at the control terminal block.

−

−- Supply air temperature sensor (analog, 10 kΩ NTC thermistor or 1000 Ω RTD)

−- Return air temperature sensor (where return air mixing is provided)

−- Mixed air temperature sensor (upstream of cooling coil)

−- Chilled water coil valve control output (0-10V or 4-20mA)

−- Hot water coil valve control output (0-10V or 4-20mA)

−- OA damper actuator control output

−- RA damper actuator control output

−- EA or relief damper actuator control output

−- Supply fan VFD speed control output (0-10V)

−- Supply fan run/stop command (digital)

−- Supply fan status (proof of airflow via differential pressure switch or VFD feedback)

−- Filter differential pressure switch or transmitter (each filter bank)

−- Smoke detector in supply air plenum (per NFPA 90A)

−- Smoke detector in return air plenum (per NFPA 90A, where return air quantity exceeds threshold)

−- Low-temperature (freeze-stat) thermostat in mixed air section (digital alarm/shutdown)

−

−```datasheet

−label: Controls Points Package

−type: checkbox

−options:

− - "Supply air temperature (SAT) sensor"

− - "Return air temperature sensor"

− - "Mixed air temperature sensor"

− - "Outdoor air temperature sensor"

− - "Supply air humidity sensor"

− - "Return air humidity sensor"

− - "Chilled water valve control output"

− - "Hot water valve control output"

− - "OA/RA/EA damper actuator outputs"

− - "Supply fan VFD speed control"

− - "Supply fan start/stop and status"

− - "Return/relief fan VFD speed control"

− - "Filter DP switch or transmitter"

− - "Smoke detector(s) — supply and/or return"

− - "Low-limit (freeze-stat) thermostat"

− - "Drain pan high water level switch"

− - "Airflow measurement station"

− - "Coil leaving air temperature sensors (each coil)"

−default: "Supply air temperature (SAT) sensor"

−```

−

−## Smoke Detectors {toc}

−

−```datasheet

−label: Duct Smoke Detector Locations

−type: checkbox

−options:

− - "Supply air plenum — required by NFPA 90A Section 6.4"

− - "Return air plenum — required by NFPA 90A when return air exceeds 2,000 CFM"

− - "Return air plenum — all sizes (more conservative)"

−default: "Supply air plenum — required by NFPA 90A Section 6.4"

−```

−

−### Smoke detectors in the supply and return air plenums of the AHU shall be provided and installed per NFPA 90A.

−

−### Smoke detection shall initiate unit shutdown via the BAS or via a hardwired relay.

−

−### Smoke detectors shall be listed for use in air handling ducts (duct-type detector).

−

−### Detector sampling tubes shall be installed according to the detector manufacturer's instructions for the duct cross-section dimensions of the AHU plenum; an incorrectly sized sampling tube yields no meaningful sample and will not detect smoke.

−

−## Low-Limit Temperature Protection {toc}

−

−```datasheet

−label: Freeze Protection (Low-Limit Thermostat)

−type: radio

−options:

− - "Serpentine element averaging thermostat — full cross-section coverage"

− - "Single-point thermostat (not recommended — for heating-only or warm-climate units)"

− - "None (climate does not require freeze protection)"

−default: "Serpentine element averaging thermostat — full cross-section coverage"

−```

−

−### A low-limit (freeze-stat) thermostat shall be installed in the mixed air section of every AHU that supplies outdoor air in climates where outdoor air temperatures drop below 35°F.

−

−### The freeze-stat shall be a serpentine-element type covering the full cross-section of the mixed air plenum.

−

−### Single-point sensing thermostats are inadequate because cold outdoor air and warm return air stratify in the mixing section and a single point sensor may read the warm layer while the coil faces freezing temperatures. {note}

−

−### The freeze-stat shall be set to alarm at 38°F and shut down the unit at 35°F, close the outdoor air damper, and open the hot water coil valve to full heating.

−

−# Factory Testing {toc}

−

−## Standard Factory Tests {toc}

−

−### Every AHU shall undergo the following factory tests before shipment.

−

−- Fan performance test: Measure actual supply airflow (CFM) and static pressure at the design operating point using factory test instrumentation. Actual performance shall be within ±5% of specified values.

−- Motor ampere draw at design conditions, verified against nameplate values and service factor

−- Casing leakage test per AHRI 1350: Pressurize the assembled unit to design static pressure and measure leakage. Leakage shall be within the specified leakage class.

−- Drain pan tightness test: Fill drain pan with water and verify no leakage at pan seams, drain connection, or overflow connection after 15 minutes

−- Filter installation check: Verify filter media are seated with no bypass gaps; verify DP gauge or ports are functional

−- Damper stroke test: Verify each damper actuates from fully open to fully closed within the design stroke time; verify fail-safe position on loss of signal

−- Door gasket check: Verify all access door gaskets compress and seal with doors latched; check by holding a smoke pencil near each door edge with the unit pressurized

−- Electrical continuity and insulation test: Verify all factory wiring circuits for continuity and for absence of insulation breakdown between conductors and frame

−

−```datasheet

−label: Factory Acceptance Test (FAT)

−type: radio

−options:

− - "Witnessed by Owner's representative or Engineer — provide 10 days notice"

− - "Unwitnessed — certified factory test report submitted with shipment"

− - "Standard production tests only (minimum code-compliant)"

−default: "Unwitnessed — certified factory test report submitted with shipment"

−```

−

−### Test results shall be documented on a factory test report and submitted as a closeout submittal.

−

−### Units that fail any test shall be corrected and retested; no unit shall be shipped until all tests pass.

−

−### Where witnessed factory testing is specified, the Contractor shall coordinate the factory test schedule with the Owner's representative and the Engineer of Record.

−

−### Where witnessed factory testing is specified, the manufacturer shall provide a minimum of ten business days advance notice of test readiness and shall submit a proposed test procedure for review before scheduling the test.

−

−## Factory Run Test Duration {toc}

−

−```datasheet

−label: Factory Run Test Duration

−type: radio

−options:

− - "4 hours at design conditions (recommended for units over 20,000 CFM)"

− - "2 hours at design conditions"

− - "30 minutes functional check (small units under 5,000 CFM)"

−default: "2 hours at design conditions"

−```

−

−### For large central station AHUs (greater than 20,000 CFM), the factory run test shall operate the unit at design conditions for a minimum of four hours continuous operation, confirming bearing temperature rise, vibration levels at the fan section and casing, and motor ampere stability.

−

−### Elevated bearing temperatures or increasing vibration during the run test indicate a dynamic balance problem that shall be corrected before shipment.

−

−### Elevated bearing temperature is defined as a temperature rise greater than 40°F above ambient at any bearing housing. {note}

−

−# Installation and Startup {toc}

−

−## Delivery and Storage {toc}

−

−### AHUs shall be delivered to the site in the largest factory-assembled sections consistent with rigging access through the building.

−

−### All rigging paths (door openings, stairwells, mechanical room access) shall be verified before ordering.

−

−### Equipment shall be stored in a clean, dry, heated space.

−

−### Where indoor storage is not available, units shall remain in manufacturer's protective shipping packaging and condensation heaters in electrical compartments shall be energized.

−

−### Units stored outdoors for more than 30 days shall be inspected by the Contractor before installation for moisture intrusion, corrosion, and pest infestation, and a written inspection report shall be provided to the Owner.

−

−### Fan assemblies, bearings, and belt-drive components shall be protected from construction dust and moisture during storage.

−

−### Shaft openings shall be sealed.

−

−### Fan assemblies shall not be stored in a position that places the shaft horizontal without proper temporary bearing support, as improperly stored fans develop flat spots on bearings.

−

−## Rigging and Setting {toc}

−

−### AHUs shall be rigged and set in accordance with the manufacturer's installation instructions.

−

−### Rigging lugs, base spreader bars, or other manufacturer-furnished rigging hardware shall be used; chain or cable shall not wrap around casing panels.

−

−### After setting, the unit shall be verified level (±1/8 in. over the unit length) and the drain pans verified to slope to drain.

−

−### Vibration isolators shall be verified loaded to within the manufacturer's design load range.

−

−### All temporary shipping braces, shipping bolts, and transit restraints shall be removed after setting and before operating.

−

−### Shipping braces in fan assemblies, if not removed, will cause severe unbalance vibration and immediate bearing damage. {note}

−

−### Pre-Startup Checks {toc}

−

−#### After assembly and before energizing, the following pre-startup checks shall be conducted.

−

−- Verify no shipping restraints remain in place

−- Verify fan wheel rotates freely by hand with no contact with housing or scroll

−- Verify belt tension and sheave alignment on belt-driven fans (belt deflection at mid-span per manufacturer's specification)

−- Verify motor rotation direction matches arrow on fan housing before coupling to belt or direct-drive shaft

−- Verify all access doors are fully closed and latched

−- Verify condensate drain trap is installed and primed

−- Verify flexible duct and pipe connections are installed

−- Verify all penetrations through the casing (pipe, duct, conduit) are gasketed and sealed

−

−```datasheet

−label: Pre-Startup Inspection Checklist

−type: checkbox

−options:

− - "Shipping restraints removed"

− - "Fan wheel rotates freely — no contact"

− - "Belt tension and alignment verified"

− - "Motor rotation confirmed correct"

− - "Access doors closed and latched"

− - "Drain trap installed and primed"

− - "Flexible connections installed"

− - "Casing penetrations sealed"

− - "Filter media installed"

− - "All service clearances maintained"

−default: "Shipping restraints removed"

−```

−

−## Ductwork Connections {toc}

−

−```datasheet

−label: AHU-to-Duct Connection Type

−type: radio

−options:

− - "Factory-flanged connection with flexible connector"

− - "Factory-slip-fit connection with flexible connector"

− - "Factory sheet metal collar — flexible connector field-provided"

−default: "Factory-flanged connection with flexible connector"

−```

−

−### Supply and return ductwork shall connect to the AHU through flexible canvas or elastomeric connectors per NFPA 90A and SMACNA requirements.

−

−### Ductwork shall be independently supported so that duct weight is not transferred to the AHU casing.

−

−### Connecting ductwork shall be installed after the AHU is set and leveled on its final isolators; connecting ductwork before the unit is on its isolators will transmit the duct weight and stress into the connection flanges.

−

−## Piping Connections {toc}

−

−### Hydronic coil connections shall be made with flexible connectors and shutoff valves on supply and return lines at each coil.

−

−### Coil connections shall not bear the weight of the piping system; all connecting piping shall be independently supported within 12 in. of the coil connection.

−

−### After piping connections are made, coils shall be hydrostatically tested at 1.5 times the design working pressure (minimum 150 psig) for a minimum of four hours before the unit is operated.

−

−### See [[sync/hydronic-piping]] for additional coil connection requirements.

−

−### Condensate drain connections shall include a union to allow the trap to be disassembled for cleaning.

−

−### The drain line shall be run to the nearest floor drain with a slope of not less than 1/8 in. per foot; horizontal condensate drain runs shall not exceed 20 ft without a secondary trap or venting.

−

−## Initial Startup and Commissioning {toc}

−

−### Startup shall be performed by a factory-trained representative of the AHU manufacturer.

−

−### TAB shall be performed by an independent certified testing and balancing firm per [[sync/testing-adjusting-and-balancing]] after startup is complete.

−

−### Initial Startup Sequence {toc}

−

−#### The initial startup sequence shall include the following steps.

−

−- Check all coil and damper valve and actuator connections; stroke each valve and actuator through full range and verify correct position from the BAS

−- Energize unit with fan at minimum speed; check for unusual noises, bearing temperatures, and motor ampere draw; run for minimum 15 minutes before increasing to design speed

−- Increase fan to design speed; verify design CFM and static pressure within ±10% of design values

−- Verify drain pan drains completely during operation; observe condensate formation and flow at the drain pan

−- Verify freeze-stat trips the unit at the set point (test by introducing cold air across the element)

−- Verify smoke detector triggers unit shutdown (test per detector manufacturer's instructions)

−- Verify all BAS points report correctly and control sequences execute as designed

−- Verify filter gauges read within the initial resistance range for the installed filter MERV rating

−

−```datasheet

−label: Startup Commissioning Level

−type: select

−options:

− - "Manufacturer startup with TAB verification (standard)"

− - "Manufacturer startup, TAB, and functional performance testing (FPT) per commissioning agent"

− - "Manufacturer startup only — no TAB (not recommended)"

−default: "Manufacturer startup with TAB verification (standard)"

−```

−

−## Balancing and TAB {toc}

−

−### The TAB agent shall measure and report supply airflow, return airflow, and outdoor airflow at design and minimum operating conditions.

−

−### Airflow shall be within ±10% of design values after balancing.

−

−### Fan speed, sheave size, or VFD frequency shall be adjusted as necessary to achieve design airflow at design static pressure.

−

−### The final TAB report shall document as-built fan speed, airflow, static pressure, motor ampere draw, sheave sizes, and filter differential pressure at clean filter condition.

−

−# Warranty {toc}

−

−## Equipment Warranty {toc}

−

−```datasheet

−label: Equipment Warranty Period

−type: select

−options:

− - "1 year parts and labor"

− - "2 years parts and labor"

− - "5 years parts, 1 year labor"

− - "10 years parts (compressor/coil only), 1 year labor"

−default: "1 year parts and labor"

−```

−

−### The AHU manufacturer shall warrant the equipment against defects in materials and workmanship for the period selected below from the date of substantial completion.

−

−### Warranty shall cover the complete assembly including casing, fan, motor, coils, filters, dampers, and drain pans.

−

−### The manufacturer shall maintain service capability within the project region with factory-trained technicians available within 48 hours of notification during the warranty period.

−

−## Fan and Motor Warranty {toc}

−

−```datasheet

−label: Fan Assembly Extended Warranty

−type: radio

−options:

− - "Standard — 1 year same as equipment warranty"

− - "Extended — 2 years on fan assembly and bearings"

− - "Extended — 5 years on fan assembly and bearings"

−default: "Extended — 2 years on fan assembly and bearings"

−```

−

−### Fan assemblies and motors shall carry a separate warranty of not less than the period selected below.

−

−### The motor manufacturer's warranty shall be provided in addition to the AHU warranty and shall pass through to the Owner.

−

−## Coil Warranty {toc}

−

−```datasheet

−label: Coil Warranty Period

−type: select

−options:

− - "1 year (minimum)"

− - "5 years — coil tube and fin assembly"

− - "10 years — premium coil warranty program"

−default: "5 years — coil tube and fin assembly"

−```

−

−### Factory-installed coils shall be warranted against leakage and defects for a minimum of five years from substantial completion.

−

−### Coil warranty shall cover the coil tube and fin assembly; it does not cover damage from improper system water treatment, freeze damage resulting from improper system operation, or physical damage from tools or improper filter access.

−

−## Installation Warranty {toc}

−

−### The Contractor shall warrant the installation workmanship, including all field connections, sealing, vibration isolation, and associated items, for one year from the date of substantial completion.

−

−## Spare Parts {toc}

−

−### The following spare parts shall be provided at substantial completion as selected below.

−

−```datasheet

−label: Spare Parts at Substantial Completion

−type: checkbox

−options:

− - "One complete set of spare filters (each type and MERV)"

− - "One complete set of drive belts (belt-driven fans)"

− - "One spare sheave set (belt-driven fans)"

− - "One tube of bearing grease with grease gun"

− - "One set of door gaskets for each unit"

− - "Set of spare fuses for all fuse types installed"

−default: "One complete set of spare filters (each type and MERV)"

−```

−

−### Spare filters shall be stored in the mechanical room in sealed manufacturer's packaging labeled with the unit designation, filter MERV rating, and installation date of the installed set.

−

−### The O&M manual shall include a filter maintenance schedule and recommended change frequency based on the initial and final pressure drop values from the submittal.

−

−# Identification and Labeling {toc}

−

−## Unit Nameplate {toc}

−

−```datasheet

−label: Unit Identification Nameplate Material

−type: radio

−options:

− - "Laminated phenolic — indoor units"

− - "Stainless steel — outdoor or corrosive environments"

−default: "Laminated phenolic — indoor units"

−```

−

−### Each AHU shall be provided with a permanent identification nameplate on the outside of the casing.

−

−### The nameplate shall be stainless steel or laminated phenolic, permanently attached (not adhesive-only).

−

−### The nameplate shall include unit designation, manufacturer's model and serial number, design airflow (CFM), design external static pressure (in. w.g.), supply fan motor horsepower, electrical supply voltage and phase, and date of manufacture.

−

−## Access Door and Panel Labeling {toc}

−

−### All access doors shall be labeled to indicate the component section accessible through each door (e.g., "FILTER SECTION — MERV 13," "COOLING COIL," "FAN SECTION — ROTATION CHECK BEFORE OPENING").

−

−### Labels shall be applied to the exterior surface of each door in characters visible from 5 ft away.

−

−### Electrical panel doors and control terminal boxes shall include a single-line wiring diagram permanently mounted inside the door.

−

−### Control terminal strips shall be labeled to match the control sequence documentation.

−

−### Filter section doors shall include a filter installation date tag holder for recording the date of each filter change.

+---

+title: Air Handling Units

+category: Mechanical / Air Distribution

+description: >

+ When to use: Central station air handling units that condition air and deliver it through a field-installed duct distribution system, whether factory-assembled in shipping sections or field-erected from components. Covers indoor and outdoor units, constant-volume and variable-air-volume systems, single-zone and multiple-zone arrangements, mixed-air units and dedicated outdoor air units, and units serving commercial, institutional, industrial, healthcare, and laboratory occupancies.

+ Not intended for: Unitary packaged equipment with an integral refrigeration circuit; fan coil units, blower coil units, and air terminal units; ductwork and duct accessories beyond the unit connection; variable frequency drives; hydronic piping and plant equipment serving the coils; the building automation system and its sequences of operation; testing, adjusting, and balancing of the completed air distribution system.

+---

+# Scope {toc}

+## A central station air handling unit is an assembly of a casing, one or more fans, and the coil, filter, damper, and accessory sections needed to condition air, all of which depend on field-installed ductwork to carry that air to the spaces served. That dependence is what separates the equipment covered here from unitary and terminal equipment, which conditions air for the space it sits in or immediately adjacent to. {note}

+## The following sections and provisions are covered when they form part of the unit: {note}

+- Casing, structural base, and access provisions

+- Supply, return, relief, and exhaust fan sections

+- Chilled water, direct-expansion, hot water, steam, and electric heating coils

+- Air filtration sections

+- Mixing sections, outdoor air, return air, and relief air dampers, and the air-side economizer

+- Energy recovery sections

+- Humidifier sections

+- Drain pans, condensate connections, and traps

+- Vibration isolation, seismic restraint, and flexible connections

+- Unit-mounted controls, safety devices, and the physical interface to the building automation system

+## The following are outside this standard: {note}

+- Ductwork, duct accessories, and duct insulation beyond the unit connection, covered by [[sync/hvac-ductwork]]

+- Fan coil units, blower coil units, and air terminal units, covered by [[sync/fan-coil-units]]

+- Unitary packaged equipment with an integral refrigeration circuit, covered by [[sync/packaged-rooftop-units]]

+- Variable frequency drives, covered by [[sync/hvac-variable-frequency-drives]]

+- Hydronic piping, valves, and specialties serving the coils, covered by [[sync/hydronic-piping]]

+- Chilled water and heating water plant equipment, covered by [[sync/hvac-pumps]]

+- The building automation system, its sequences of operation, and control devices not mounted on the unit, covered by [[sync/building-automation-system]]

+- Testing, adjusting, and balancing of the completed air distribution system, covered by [[sync/testing-adjusting-and-balancing]]

+## Each air handling unit shall be furnished as a coordinated assembly by a single manufacturer, who shall be responsible for the aerodynamic, structural, thermal, acoustic, and hydraulic interaction of the sections furnished.

+## Where the Contract Documents direct that a unit be field-erected from separately procured sections, the Contractor shall identify in the submittal the party responsible for the coordinated performance of the assembly.

+## Where a requirement of this standard conflicts with a requirement of a standard that governs a component covered elsewhere, the Engineer of Record shall make the initial determination of which requirement governs.

+# Referenced Standards {toc}

+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.

+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.

+| Standard | Title |

+|----------|-------|

+| ANSI/AHRI 430 (I-P) | Performance Rating of Central Station Air-handling Unit Supply Fans |

+| ANSI/AHRI 410 | Performance Rating of Forced-Circulation Air-Cooling and Air-Heating Coils |

+| ANSI/AHRI 1350 (I-P) | Mechanical Performance Rating of Central Station Air-handling Unit Casings |

+| ANSI/AHRI 1060 | Performance Rating of Air-to-Air Exchangers for Energy Recovery Ventilation Equipment |

+| ANSI/AMCA 210 / ANSI/ASHRAE 51 | Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating |

+| ANSI/AMCA 208 | Calculation of the Fan Energy Index |

+| ANSI/AMCA 214 | Test Procedure for Calculating Fan Energy Index for Commercial and Industrial Fans and Blowers |

+| ANSI/AMCA 300 | Reverberant Room Method for Sound Testing of Fans |

+| ANSI/AMCA 301 | Methods for Calculating Fan Sound Ratings from Laboratory Test Data |

+| ANSI/AMCA 500-D | Laboratory Methods of Testing Dampers for Rating |

+| AMCA 511 | Certified Ratings Program - Product Rating Manual for Air Control Devices |

+| ANSI/AMCA 610 | Laboratory Methods of Testing Airflow Measurement Stations for Performance Rating |

+| ANSI/ASHRAE 52.2 | Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size |

+| ANSI/ASHRAE 62.1 | Ventilation and Acceptable Indoor Air Quality |

+| ANSI/ASHRAE 84 | Method of Testing Air-to-Air Heat/Energy Exchangers |

+| ANSI/ASHRAE 111 | Measurement, Testing, Adjusting, and Balancing of Building HVAC Systems |

+| ANSI/ASHRAE/IES 90.1 | Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings |

+| ANSI/ASHRAE 188 | Legionellosis: Risk Management for Building Water Systems |

+| NFPA 90A | Standard for the Installation of Air-Conditioning and Ventilating Systems |

+| NFPA 70 | National Electrical Code |

+| NFPA 72 | National Fire Alarm and Signaling Code |

+| UL 60335-2-40 | Household and Similar Electrical Appliances - Safety - Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers |

+| UL 1995 | Heating and Cooling Equipment |

+| UL 900 | Air Filter Units |

+| UL 508A | Industrial Control Panels |

+| UL 214 | Tests for Flame Propagation of Fabrics and Films |

+| NEMA MG 1 | Motors and Generators |

+| ASTM A653 | Steel Sheet, Zinc-Coated or Zinc-Iron Alloy-Coated by the Hot-Dip Process |

+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |

+| SMACNA HVAC Duct Construction Standards | HVAC Duct Construction Standards - Metal and Flexible |

+| ASHRAE Handbook | HVAC Systems and Equipment |

+# Submittals {toc}

+## Action Submittals {toc}

+### The Contractor shall submit the following for each air handling unit tag and shall not release any unit for fabrication until the submittal has been reviewed and returned:

+- Unit configuration drawing showing section order, overall dimensions, shipping splits, connection sizes and locations, operating and shipping weights, center of gravity, and required service clearances

+- Fan selection data showing the certified fan curve with the design operating point plotted against the calculated system resistance, and the shaft power, speed, and static efficiency at that point

+- Fan energy index at the highest design airflow rate, with the calculation basis identified

+- For variable-air-volume units, the fan operating point at minimum design airflow and the surge or stall boundary of the selected wheel

+- Fan sound power levels in each of the eight octave bands from 63 Hz through 8,000 Hz, reported separately for inlet, outlet, and casing radiated paths

+- Motor data including nameplate power, speed, voltage, phase, full-load amperes, efficiency at 100%, 75%, and 50% load, service factor, insulation system, enclosure, and inverter-duty rating

+- Coil selection data for each coil giving entering and leaving air and fluid conditions, face area, face velocity, rows, fin spacing, circuiting, capacity, and air-side and fluid-side pressure drop

+- Filter data for each stage giving efficiency rating, media construction, face area, face velocity, initial resistance, recommended final resistance, and dust-holding capacity

+- Casing construction details showing panel section, insulation type and thickness, thermal break arrangement, door and panel gasketing, and the fastening of interior liners

+- Casing performance ratings for air leakage, deflection, and thermal performance, with the rating basis identified

+- Damper schedule giving blade arrangement, frame and blade material, seal material, free area, leakage class, pressure rating, and actuator torque and fail position

+- Drain pan drawings showing material, gauge, extent relative to the coil face, slope directions, and the location and size of primary and secondary drain connections

+- Vibration isolation data giving isolator type, rated and operating load, static deflection at operating load, and the calculated isolation efficiency at the lowest operating fan speed

+- Seismic restraint details and calculations bearing the seal of an engineer licensed in the jurisdiction of the project, where seismic restraint is required

+- Electrical schematic and point-to-point wiring diagram showing factory wiring, field terminations, and the terminal designations used on the unit

+- Schedule of control devices furnished with the unit, identifying signal type, range, and terminal designation for each point

+```datasheet

+label: Action Submittals Required

+type: checkbox

+options:

+ - "Unit configuration drawing with weights and service clearances"

+ - "Certified fan curve with the design point plotted"

+ - "Fan energy index with calculation basis"

+ - "Variable-air-volume minimum-flow operating point"

+ - "Octave band fan sound power levels"

+ - "Motor data with efficiency and inverter-duty rating"

+ - "Coil selection data for each coil"

+ - "Filter data for each stage"

+ - "Casing construction details"

+ - "Casing leakage, deflection, and thermal ratings"

+ - "Damper schedule with leakage class and actuator data"

+ - "Drain pan drawings"

+ - "Vibration isolation data with static deflection"

+ - "Seismic restraint details and calculations"

+ - "Electrical schematic and wiring diagram"

+ - "Control device schedule with terminal designations"

+default: ["Unit configuration drawing with weights and service clearances", "Certified fan curve with the design point plotted", "Fan energy index with calculation basis", "Octave band fan sound power levels", "Motor data with efficiency and inverter-duty rating", "Coil selection data for each coil", "Filter data for each stage", "Casing construction details", "Damper schedule with leakage class and actuator data", "Drain pan drawings", "Vibration isolation data with static deflection", "Electrical schematic and wiring diagram", "Control device schedule with terminal designations"]

+```

+### The configuration drawing shall show the coil pull clearance, the filter withdrawal clearance, and the fan wheel and motor removal path for each section, dimensioned from the unit face.

+### A submittal that omits the service clearances is the single most expensive omission in this equipment class, because a unit that fits the mechanical room but cannot have its coils pulled is discovered only when the first coil fails, by which time the surrounding piping, ductwork, and often a wall are already in place. {note}

+## Closeout Submittals {toc}

+### The Contractor shall submit the following at or before substantial completion:

+- Operation and maintenance manuals for each unit, indexed by unit tag, containing installation, operation, maintenance, and troubleshooting instructions and a parts list for every furnished component

+- As-built configuration drawings recording every field modification to the reviewed configuration

+- Certified factory test report for each unit

+- Startup report for each unit signed by the person who performed the startup

+- Record of the as-installed drive components for belt-driven fans, giving sheave designations, bore, bushing, belt designation, and center distance

+- Record of the filter media installed at substantial completion, giving efficiency rating, media designation, quantity, size, and installation date

+- Air balance report for the units and their connected systems

+- Warranty documentation correlating each unit serial number to its installation date and warranty expiration date

+```datasheet

+label: Closeout Submittals Required

+type: checkbox

+options:

+ - "Operation and maintenance manuals indexed by unit tag"

+ - "As-built configuration drawings"

+ - "Certified factory test report for each unit"

+ - "Signed startup report for each unit"

+ - "As-installed drive component record"

+ - "Installed filter media record with installation dates"

+ - "Air balance report"

+ - "Warranty documentation correlated to serial numbers"

+default: ["Operation and maintenance manuals indexed by unit tag", "As-built configuration drawings", "Certified factory test report for each unit", "Signed startup report for each unit", "Installed filter media record with installation dates", "Air balance report", "Warranty documentation correlated to serial numbers"]

+```

+## Informational Submittals {toc}

+### The Contractor shall submit the following for information at the times indicated in each item:

+- Rigging and setting plan, submitted before the unit ships, showing the delivery route, lifting points, spreader arrangement, and the temporary loads imposed on the structure

+- Manufacturer's field service report for each site visit made during the warranty period

+- Certification that the coils have been hydrostatically tested after field piping connections, with the test pressure and duration recorded

+- Written record of the pre-existing condition of any surface or assembly the Contractor is required to restore

+```datasheet

+label: Informational Submittals Required

+type: checkbox

+options:

+ - "Rigging and setting plan before shipment"

+ - "Field service reports during the warranty period"

+ - "Field hydrostatic test certification for coils"

+ - "Pre-existing condition record for restored surfaces"

+default: ["Rigging and setting plan before shipment", "Field service reports during the warranty period", "Field hydrostatic test certification for coils"]

+```

+# Quality Assurance {toc}

+## Manufacturer Qualifications {toc}

+### The unit manufacturer shall have produced central station air handling units of the type furnished for not less than the number of years indicated in the datasheet.

+```datasheet

+label: Minimum Manufacturer Experience

+type: range

+unit: years

+options:

+ min: 0

+ max: 25

+ step: 1

+default: 5

+```

+### The manufacturer shall make replacement parts available for the units furnished for not less than ten years after the date of manufacture.

+### An experience requirement is a proxy for production maturity, not a measure of it, and it excludes new entrants along with unproven ones. A project that would accept a well-capitalized new manufacturer can set the requirement to zero and rely on the certification, testing, and warranty requirements instead. {note}

+## Certification of Rated Performance {toc}

+### Published performance ratings shall be certified under the programs indicated in the datasheet.

+```datasheet

+label: Certification Programs Required

+type: checkbox

+options:

+ - "Supply fan performance certified under AHRI 430"

+ - "Coil performance certified under AHRI 410"

+ - "Casing mechanical performance certified under AHRI 1350"

+ - "Energy recovery performance certified under AHRI 1060"

+ - "Fan aerodynamic performance licensed to bear the AMCA seal"

+ - "Fan sound performance licensed to bear the AMCA seal"

+ - "Damper leakage licensed to bear the AMCA seal"

+default: ["Supply fan performance certified under AHRI 430", "Coil performance certified under AHRI 410", "Fan aerodynamic performance licensed to bear the AMCA seal"]

+```

+### Ratings claimed as certified shall bear the certification mark of the applicable program on the published data submitted.

+### Where a selected component is outside the scope of the certification program named for it, the manufacturer shall state that fact in the submittal and shall furnish the test data on which the rating is based.

+### A certification program is a statement about how a rating was produced, not about how good the rating is. AHRI 430 certifies that the supply fan performance published for a central station unit was verified by an independent laboratory under a program AHRI administers, so two certified selections can be compared directly. Participation in the casing program under AHRI 1350 is narrower than participation in the fan program, so requiring it can restrict the bidder list. {note}

+## Electrical Safety Listing {toc}

+### The complete unit assembly, including all factory-installed electrical components, shall be listed and labeled by a Nationally Recognized Testing Laboratory.

+### Units listed to UL 1995 are acceptable where the Authority Having Jurisdiction accepts that listing for the equipment furnished.

+### Factory-wired control and power panels shall be listed to UL 508A and shall bear a label giving the short-circuit current rating of the panel.

+### Field-installed electrical components not covered by the unit listing shall be individually listed for the application.

+## Preinstallation Conference {toc}

+### A preinstallation conference shall be held before the first unit is delivered to the site, attended by the Contractor, the mechanical installer, the controls installer, the testing and balancing agent, the commissioning agent where one is engaged, and the Owner's representative.

+### The conference agenda shall cover the delivery and rigging sequence, the structural readiness of each equipment location, the utility connections and their sequence, the vibration isolation procedure, the controls interface and point responsibility, and the startup and commissioning schedule.

+# Service Conditions and Site Data {toc}

+## Installation Environment {toc}

+### The casing weather protection furnished shall be as indicated in the datasheet.

+```datasheet

+label: Casing Weather Protection

+type: select

+options:

+ - "Indoor casing with no weather protection"

+ - "Outdoor casing with sloped roof, weather hoods, and drainable base"

+ - "Outdoor casing with a walk-in weather enclosure over the service side"

+ - "Indoor casing within a field-erected weather enclosure by others"

+```

+### The unit locations and orientations are [[drawing: as indicated on the mechanical plans]].

+### Weather protection is a construction decision rather than a location, which is why it is a selection here even though the location that drives it is shown on the drawings. A unit set in a rooftop penthouse is indoors for the purpose of casing construction and outdoors for the purpose of the ambient temperature its motors and controls see. {note}

+### Outdoor units shall be furnished with bird screens on all outdoor air intakes and relief openings.

+### Exposed fasteners, hinges, latches, and hardware on outdoor units shall be stainless steel or a coated steel with equivalent corrosion resistance.

+## Site Elevation {toc}

+### Fan, coil, filter, and motor ratings shall be corrected for the air density at the site elevation indicated in the datasheet, and the corrected values shall be the values published in the submittal.

+```datasheet

+label: Site Elevation

+type: range

+unit: ft

+drawing_ref: "site elevation as indicated on the contract documents"

+options:

+ min: 0

+ max: 12000

+ step: 100

+default: deferred

+```

+### Air density falls roughly 3% per 1,000 ft of elevation. A fan selected from a sea-level catalog and installed in Denver moves the same volume of air but develops about 17% less static pressure and draws proportionally less power, so the unit makes its airflow only if the selection was corrected. The same thinning air also reduces the convective cooling of an open motor, which is why motor ratings carry their own altitude correction. {note}

+## Outdoor Design Conditions {toc}

+### Coil capacities and economizer operation shall be evaluated at the outdoor design conditions indicated in the datasheet.

+```datasheet

+label: Summer Outdoor Design Dry-Bulb Temperature

+type: range

+unit: °F

+drawing_ref: "design conditions as indicated on the mechanical schedules"

+options:

+ min: 70

+ max: 125

+ step: 1

+default: deferred

+```

+```datasheet

+label: Summer Outdoor Design Wet-Bulb Temperature

+type: range

+unit: °F

+drawing_ref: "design conditions as indicated on the mechanical schedules"

+options:

+ min: 50

+ max: 90

+ step: 1

+default: deferred

+```

+```datasheet

+label: Winter Outdoor Design Dry-Bulb Temperature

+type: range

+unit: °F

+drawing_ref: "design conditions as indicated on the mechanical schedules"

+options:

+ min: -40

+ max: 60

+ step: 1

+default: deferred

+```

+### Where the design conditions in the datasheet differ from the conditions used in the manufacturer's selection, the manufacturer shall reselect at the datasheet conditions before the unit is released for fabrication.

+# Airflow and Static Pressure {toc}

+## Design Airflow {toc}

+### Each fan shall deliver the airflow indicated in the datasheet at the design external static pressure, at the site elevation, and at the design entering air conditions.

+```datasheet

+label: Supply Airflow

+type: range

+unit: cfm

+drawing_ref: "airflow as indicated on the mechanical schedules"

+options:

+ min: 500

+ max: 150000

+ step: 100

+default: deferred

+```

+```datasheet

+label: Return or Relief Airflow

+type: range

+unit: cfm

+drawing_ref: "airflow as indicated on the mechanical schedules"

+options:

+ min: 0

+ max: 150000

+ step: 100

+default: deferred

+```

+```datasheet

+label: Minimum Outdoor Airflow

+type: range

+unit: cfm

+drawing_ref: "ventilation airflow as indicated on the mechanical schedules"

+options:

+ min: 0

+ max: 150000

+ step: 100

+default: deferred

+```

+### For variable-air-volume units, the fan shall operate stably and without surge, stall, or audible instability from design airflow down to the minimum airflow indicated in the datasheet.

+```datasheet

+label: Minimum Controlled Airflow as a Percentage of Design

+type: range

+unit: '%'

+drawing_ref: "turndown as indicated on the mechanical schedules and control sequences"

+options:

+ min: 5

+ max: 100

+ step: 5

+default: deferred

+```

+### Turndown is a property of the whole system rather than the fan alone. The fan sets a floor below which the wheel becomes unstable, the terminal units set a floor below which zones lose control authority, and the ventilation calculation sets a floor below which the outdoor air fraction can no longer be maintained. The binding one is usually not the fan. {note}

+## Static Pressure {toc}

+### The design external static pressure for each fan shall be as indicated in the datasheet.

+```datasheet

+label: Design External Static Pressure

+type: range

+unit: in. w.g.

+drawing_ref: "external static pressure as indicated on the mechanical schedules"

+options:

+ min: 0.1

+ max: 12

+ step: 0.05

+default: deferred

+```

+### The manufacturer shall state the internal static pressure loss of each furnished section at design airflow, with clean filters and dry coils, and shall add it to the external static pressure to establish the total static pressure at which the fan is selected.

+### The fan shall be selected at the total static pressure increased by the selection margin indicated in the datasheet.

+```datasheet

+label: Fan Selection Static Pressure Margin

+type: range

+unit: '%'

+options:

+ min: 0

+ max: 25

+ step: 5

+```

+### A selection margin buys insurance against an underestimated system resistance and pays for it in installed fan power, casing pressure class, and sound. A margin large enough to matter also moves the operating point far enough left on the curve that a constant-volume unit runs permanently throttled, so on variable-speed units the margin costs little and on constant-volume units it costs continuously. {note}

+### Where the datasheet margin is zero, the fan shall be selected at the calculated total static pressure without addition.

+### Internal static pressure losses shall be stated with dirty-filter resistance excluded from the fan selection point and reported separately, so that the fan curve reserve available at the filter change-out condition is visible in the submittal.

+# Fan Selection {toc}

+## Fan Arrangement {toc}

+### The supply fan arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Supply Fan Arrangement

+type: select

+options:

+ - "Single housed centrifugal fan"

+ - "Multiple housed centrifugal fans in parallel"

+ - "Single unhoused plenum fan"

+ - "Array of unhoused plenum fans"

+ - "Mixed-flow fan in a cylindrical housing"

+ - "Vaneaxial fan"

+```

+### A housed centrifugal fan discharges into a scroll and then into a duct connection, which concentrates the discharge into one opening and makes the unit longer where the discharge has to turn. An unhoused plenum fan discharges into the casing itself and lets the downstream section draw from a pressurized plenum, which shortens the unit and frees the discharge location. {note}

+### A fan array replaces one large wheel with several small ones sharing the same plenum. Sound power drops because the tip speed needed for a given pressure falls with wheel diameter, the array continues to operate at reduced capacity when one fan is out of service, and the individual assemblies are small enough to be carried through a door. The array adds motor count, drive count, and backdraft dampers to maintain. {note}

+### Each fan in an array shall be furnished with a backdraft damper or an equivalent means of preventing reverse flow through an idle fan.

+### The manufacturer shall state the fan energy index of an array in accordance with ANSI/AMCA 208 for the array as a whole rather than for an individual fan.

+## Fan Wheel Type {toc}

+### The supply fan wheel type shall be as indicated in the datasheet.

+```datasheet

+label: Supply Fan Wheel Type

+type: select

+options:

+ - "Airfoil centrifugal"

+ - "Backward-inclined flat blade centrifugal"

+ - "Backward-curved single-thickness centrifugal"

+ - "Forward-curved centrifugal"

+ - "Mixed flow"

+ - "Axial with adjustable-pitch blades"

+```

+### Airfoil and backward-inclined wheels reach their peak efficiency at higher specific speeds and have a power curve that peaks and then falls, so the motor is not overloaded if the system resistance turns out lower than calculated. Forward-curved wheels are quieter at low speed and physically smaller for a given airflow, and their power rises continuously with airflow, so a forward-curved selection carries a real risk of motor overload when the actual system resistance is below the design value. {note}

+### Where a forward-curved wheel is selected, the motor shall be sized for the power the fan draws at the point where the fan curve crosses a system curve representing the ductwork with clean filters and the dampers in their full-open position.

+### Fan wheels and shafts shall be dynamically balanced as an assembly before installation in the unit.

+### Balance quality shall be verified by measurement at the fan bearing housings during the factory run test, and the measured values shall be recorded in the factory test report.

+## Drive Arrangement {toc}

+### The fan drive arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Fan Drive Arrangement

+type: radio

+options:

+ - "Direct drive"

+ - "Belt drive"

+default: "Direct drive"

+```

+### Requirements in this article that address sheaves, belts, and drive alignment apply where a belt drive is selected in the datasheet.

+### Belt-driven fans shall be furnished with an adjustable motor base that permits belt tensioning and sheave alignment without removing the motor.

+### The furnished sheave combination shall produce the specified fan speed within ±5% and shall permit a speed change of at least ±10% by sheave replacement without changing the belt centerline distance beyond the adjustment range of the motor base.

+### Belt-driven fans operating at variable speed shall be selected so that the drive ratio and the frequency range together keep the fan below the maximum speed published by the fan manufacturer at every point in the operating range.

+### Belt guards shall be furnished on every belt drive accessible through a service door, and shall include an opening that permits a tachometer reading on the fan shaft without removing the guard.

+### A belt drive is a speed-matching device and a maintenance item at the same time. It lets one motor frame serve a range of fan speeds, which is why it survived so long, and it wears, sheds dust into the airstream, and loses a few percent of the shaft power to slip. Direct drive removes all of that and fixes the fan speed at the motor speed, so the speed matching has to come from somewhere else, which in practice means a variable frequency drive or an electronically commutated motor. {note}

+## Fan Capacity Control {toc}

+### The means of fan capacity control shall be as indicated in the datasheet.

+```datasheet

+label: Fan Capacity Control

+type: select

+options:

+ - "Variable speed by variable frequency drive"

+ - "Variable speed by electronically commutated motor"

+ - "Constant speed"

+ - "Inlet guide vanes with a constant-speed motor"

+ - "Discharge dampers with a constant-speed motor"

+ - "Fan staging within an array with constant-speed motors"

+default: "Variable speed by variable frequency drive"

+```

+### Variable frequency drives furnished for fan motors shall conform to [[sync/hvac-variable-frequency-drives]].

+### Where a drive is factory-mounted on the unit, it shall be mounted outside the airstream, shall be accessible without opening a section that is under pressure during operation, and shall be provided with the cooling airflow its manufacturer requires at the maximum ambient temperature at the unit location.

+### Reducing airflow by speed follows the fan laws, so power falls with roughly the cube of the speed. Reducing airflow by throttling moves the operating point up the fan curve instead, so power falls only a little and the difference is dissipated across the throttling device as heat and noise. Inlet guide vanes sit between the two because they pre-swirl the air and reshape the curve rather than simply adding resistance. {note}

+## Fan Efficiency {toc}

+### Each fan and fan array shall have a fan energy index at its highest design airflow rate not less than the value indicated in the datasheet, determined in accordance with ANSI/AMCA 208.

+```datasheet

+label: Minimum Fan Energy Index at Design Airflow

+type: range

+options:

+ min: 0.8

+ max: 1.5

+ step: 0.05

+default: 1

+```

+### Fan system power at design conditions shall not exceed the limit set by the energy code adopted for the project.

+### The submittal shall document the fan power compliance calculation, including every pressure credit claimed and the section that generates it.

+### The fan energy index compares the electrical power of the selected fan at its duty point against a reference fan at the same duty point, so a value of 1.00 means the selection is exactly as efficient as the reference and a value above 1.00 means it beats it. Because it is a ratio at a single duty point, it rewards selecting close to the peak of the fan curve and it does not reward oversizing. {note}

+### The fan energy index and the energy code fan power limit answer different questions. The index asks whether this fan is a good way to produce this duty point; the power limit asks whether the whole air system was allowed to be this resistive in the first place. A selection can pass one and fail the other. {note}

+## Fan Redundancy {toc}

+### The fan redundancy provided shall be as indicated in the datasheet.

+```datasheet

+label: Supply Fan Redundancy

+type: select

+options:

+ - "None"

+ - "Fan array sized to deliver design airflow with one fan out of service"

+ - "Dual fans operating in parallel, each sized for design airflow"

+ - "Dual fans with one fan on standby"

+default: "None"

+```

+### Where redundancy is provided, the unit controls shall be capable of transferring operation to the redundant capacity without manual intervention at the unit.

+### Where redundancy is provided, the casing shall permit isolation of an out-of-service fan from the airstream so that maintenance can be performed while the remaining capacity operates.

+## Return and Relief Fans {toc}

+### Where the datasheet indicates a return or relief fan, that fan shall be furnished as part of the unit and shall be selected at the airflow and static pressure indicated in the datasheet.

+```datasheet

+label: Return or Relief Fan

+type: select

+options:

+ - "None"

+ - "Return fan"

+ - "Relief fan"

+ - "Exhaust fan serving the energy recovery section"

+```

+### A return fan sits in the return path upstream of the mixing section and moves the full return airflow, so it can overcome return duct resistance and its speed can be tracked against the supply fan to hold a building pressure setpoint. A relief fan sits downstream of the mixing section and runs only when the economizer opens far enough that the building cannot relieve the excess air passively, so it moves less air, for fewer hours, at lower pressure. {note}

+### Where a return fan is furnished, the control sequence shall establish the airflow or pressure relationship the fan is to maintain relative to the supply fan, coordinated with [[sync/building-automation-system]].

+### Where the building can relieve economizer air through gravity relief dampers and transfer paths without exceeding the design building pressure, neither a return nor a relief fan is required.

+# Fan Motors {toc}

+## Motor Electrical Characteristics {toc}

+### Motor voltage and phase shall match the branch circuit serving the unit as shown on the electrical documents, and any discrepancy between the mechanical schedule and the electrical documents shall be resolved before the motor is released for fabrication.

+```datasheet

+label: Motor Supply Voltage

+type: range

+unit: V

+drawing_ref: "electrical drawings and panel schedules"

+options:

+ min: 115

+ max: 600

+ setpoints: [115, 208, 230, 460, 480, 575, 600]

+default: deferred

+```

+```datasheet

+label: Motor Supply Phase

+type: radio

+drawing_ref: "electrical drawings and panel schedules"

+options:

+ - "Single phase, 1Φ"

+ - "Three phase, 3Φ"

+default: deferred

+```

+```datasheet

+label: Supply Fan Motor Nameplate Power

+type: range

+unit: hp

+drawing_ref: "motor power as indicated on the mechanical schedules"

+options:

+ min: 0.25

+ max: 250

+ setpoints: [0.25, 0.5, 0.75, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200, 250]

+default: deferred

+```

+### Motor voltage is a fact about the building's electrical distribution rather than a property of the air handling unit, which is why it defers to the electrical documents. The recurring coordination failure is a mechanical schedule naming a nominal utilization voltage while the panel schedule serving the unit carries another, discovered when the motor arrives. {note}

+### Motors shall be selected so that the nameplate power is not exceeded at any operating point the fan can reach with clean filters, dry coils, and the system dampers in their full-open position.

+### Motor service factor shall be not less than 1.15 for belt-driven fans.

+### The service factor shall not be used as selection capacity, and the motor shall be capable of continuous operation at or below its nameplate power at every design operating point.

+## Motor Enclosure and Efficiency {toc}

+### The motor enclosure shall be as indicated in the datasheet.

+```datasheet

+label: Motor Enclosure

+type: select

+options:

+ - "Totally enclosed fan cooled, TEFC"

+ - "Totally enclosed air over, TEAO"

+ - "Totally enclosed nonventilated, TENV"

+ - "Totally enclosed blower cooled, TEBC"

+ - "Open drip proof, ODP"

+ - "Explosionproof"

+default: "Totally enclosed fan cooled, TEFC"

+```

+### The motor efficiency level shall be as indicated in the datasheet.

+```datasheet

+label: Motor Efficiency Level

+type: radio

+options:

+ - "NEMA Premium efficiency per NEMA MG 1"

+ - "NEMA energy efficient per NEMA MG 1"

+ - "Efficiency not specified"

+default: "NEMA Premium efficiency per NEMA MG 1"

+```

+### A motor mounted in the airstream is cooled by the air the fan is moving, which is why an air-over enclosure exists and why an open enclosure in that position sheds its winding heat directly into the supply air. On a variable-speed fan the airstream cooling falls with the airflow while the motor losses do not fall as fast, so the enclosure selection and the turndown range are linked. {note}

+### Motors mounted within the airstream shall be rated for continuous operation at the minimum airflow in the operating range without exceeding the temperature rise of the insulation system.

+## Inverter Duty Construction {toc}

+### Requirements in this article apply where the datasheet selects variable speed control by variable frequency drive.

+### Motors operated from a variable frequency drive shall be rated for inverter duty in accordance with NEMA MG 1 Part 31.

+### Motors 100 hp and larger operated from a variable frequency drive, and motors of any size where the drive is more than 100 ft from the motor, shall be furnished with a shaft grounding ring or an insulated bearing at the non-drive end.

+### The inverter output is a switched waveform rather than a sine wave. Its fast voltage transitions reflect off the impedance mismatch at the motor terminals and can arrive as a voltage roughly double the bus voltage, which is what the Part 31 insulation system is built to survive. The same switching puts a common-mode voltage on the rotor that discharges through the bearing lubricant film, and that discharge current is what shaft grounding and insulated bearings interrupt. {note}

+## Fan and Motor Bearings {toc}

+### Fan shaft bearings shall be selected for a rated life not less than the value indicated in the datasheet at the design operating speed and load.

+```datasheet

+label: Minimum Fan Bearing Rated Life

+type: range

+unit: hours

+options:

+ min: 40000

+ max: 200000

+ setpoints: [40000, 50000, 80000, 100000, 150000, 200000]

+default: 200000

+```

+### The bearing lubrication arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Fan Bearing Lubrication

+type: select

+options:

+ - "Regreasable with fittings extended to the exterior of the fan section"

+ - "Regreasable with fittings inside the fan section"

+ - "Sealed and lubricated for the rated life"

+default: "Regreasable with fittings extended to the exterior of the fan section"

+```

+### Where sealed bearings are selected, the bearing rated life requirement applies to the sealed bearing itself, and no bearing whose rated life is shorter than the requirement shall be furnished on the basis that it is not serviceable.

+### Extending grease fittings to the outside of the fan section converts a bearing service that requires opening a pressurized casing, entering the airstream, and reaching past a rotating wheel into one that takes a minute at a labeled fitting. On a unit that runs continuously, that difference is usually what decides whether the bearings actually get greased. {note}

+### Where grease fittings are extended, each line shall be labeled at the exterior with the bearing it serves and the grease type the manufacturer requires.

+# Fan Sound {toc}

+## Sound Data Basis {toc}

+### Fan sound power levels shall be determined from laboratory data taken in accordance with ANSI/AMCA 300 and calculated in accordance with ANSI/AMCA 301.

+### Sound power levels shall be reported in each of the eight octave bands from 63 Hz through 8,000 Hz.

+### Inlet, outlet, and casing radiated sound power shall be reported separately.

+### A single A-weighted number is not sufficient to evaluate an air handling unit. The blade passage frequency of a large slow wheel falls in the 63 Hz and 125 Hz bands, where A-weighting discounts it heavily and where duct linings, plenums, and building constructions all attenuate poorly. A unit that compares well on an A-weighted basis can still be the one occupants complain about. {note}

+### Where the unit serves or adjoins a space with a stated noise criterion, the design team shall perform an octave band analysis carrying the submitted sound power levels through the attenuation of the connected path to the receiving room, and shall confirm the result against the criterion stated in the Contract Documents.

+### Where the analysis shows the criterion is not met with the submitted selection, the Engineer of Record shall determine whether the remedy is a different fan selection, added attenuation, or a revised criterion.

+## In-Unit Sound Attenuation {toc}

+### Sound attenuation furnished within the unit shall be as indicated in the datasheet.

+```datasheet

+label: In-Unit Sound Attenuation

+type: select

+options:

+ - "None"

+ - "Acoustically lined discharge plenum section"

+ - "Packaged sound attenuator section within the unit"

+ - "Acoustically lined discharge plenum and inlet plenum sections"

+default: "None"

+```

+### Acoustic media exposed to the airstream shall be faced or encapsulated so that fibers are not eroded into the airstream at the maximum velocity the section sees.

+### Acoustic media shall not be installed downstream of a humidifier or in any section where condensation can occur.

+# Casing Construction {toc}

+## Panel Construction {toc}

+### The casing panel construction shall be as indicated in the datasheet.

+```datasheet

+label: Casing Panel Construction

+type: select

+options:

+ - "Double-wall insulated panel"

+ - "Double-wall insulated panel with a thermally broken frame"

+ - "Double-wall insulated panel with a perforated inner liner"

+ - "Single-wall panel with an applied interior liner"

+ - "Single-wall uninsulated panel"

+default: "Double-wall insulated panel"

+```

+```datasheet

+label: Casing Panel Insulation

+type: select

+options:

+ - "Injected polyurethane foam"

+ - "Rigid fiberglass board"

+ - "Mineral wool board"

+ - "Closed-cell elastomeric board"

+default: "Injected polyurethane foam"

+```

+### A double-wall panel puts a sheet metal skin on both faces of the insulation, so the insulation is never in the airstream, cleaning does not erode it, and the panel behaves as a structural sandwich. A single-wall panel with an applied liner leaves the liner facing exposed to the air, and the panel gets its stiffness from the frame instead of the sandwich. {note}

+### Any casing section in which the interior surface can fall below the dew point of the air on either side of the panel shall be insulated and shall be constructed so that no continuous metal path connects the interior skin to the exterior skin.

+### A thermal bridge is a continuous metal path from the inside skin to the outside skin, usually through a panel frame or a fastener. It carries heat around the insulation and drops the exterior surface temperature at that line, so the visible symptom is a grid of condensation tracing the panel joints on an otherwise dry casing. Thermal break framing interrupts that path with a low-conductivity section. {note}

+### Fasteners securing interior liners shall not penetrate to the exterior skin.

+## Panel Thermal Performance {toc}

+### The casing panel thermal resistance shall be not less than the value indicated in the datasheet.

+```datasheet

+label: Minimum Casing Panel Thermal Resistance

+type: range

+unit: hr·ft²·°F/Btu

+options:

+ min: 0

+ max: 20

+ step: 0.5

+```

+### Where the datasheet does not state a thermal resistance, the manufacturer shall state the thermal resistance of the panel furnished and the calculated exterior surface temperature at the design conditions, and shall confirm that the surface stays above the dew point of the air surrounding the unit.

+### Panel thermal resistance is selected against two separate criteria that usually give different answers. The energy criterion asks how much heat is lost or gained through the casing over a season, and it favors more insulation on outdoor units and on units carrying air far from the surrounding temperature. The condensation criterion asks whether the exterior surface stays above the dew point of the air around the unit, and it can require more insulation on a small indoor unit in a humid mechanical room than on a large rooftop unit in a dry climate. {note}

+## Casing Air Leakage {toc}

+### The casing air leakage class shall be as indicated in the datasheet.

+```datasheet

+label: Casing Air Leakage Class

+type: select

+options:

+ - "AHRI 1350 Class L1"

+ - "AHRI 1350 Class L2"

+ - "AHRI 1350 Class L3"

+ - "Leakage rate tested and reported without a certified class"

+```

+### The casing shall be leak tested at 1.5 times the design static pressure of the section under test, and the measured leakage shall be recorded in the factory test report.

+### Among the AHRI 1350 leakage classes, L1 is the tightest and L3 the loosest. {note}

+### Casing leakage costs differently on each side of the fan. Downstream of the fan the casing is above the surrounding pressure, so conditioned air leaks out of the unit and is paid for twice, once to condition it and once to move it. Upstream of the fan the casing is below the surrounding pressure, so mechanical room air is drawn in downstream of the filters, past the point where it would have been cleaned, and in a cooling unit it arrives after the coil has already dehumidified the air it mixes with. {note}

+### Penetrations through the casing for piping, conduit, drains, and control tubing shall be sealed with a gasketed or grommeted fitting that maintains the leakage class of the section.

+## Casing Deflection and Pressure Class {toc}

+### The casing deflection class shall be as indicated in the datasheet.

+```datasheet

+label: Casing Deflection Class

+type: select

+options:

+ - "AHRI 1350 Class D1"

+ - "AHRI 1350 Class D2"

+ - "AHRI 1350 Class D3"

+ - "Deflection tested and reported without a certified class"

+```

+### The casing pressure class shall be as indicated in the datasheet, and shall be not less than the maximum static pressure the fan can develop at shutoff with the unit dampers closed.

+```datasheet

+label: Casing Pressure Class

+type: range

+unit: in. w.g.

+options:

+ min: 2

+ max: 16

+ step: 1

+```

+### Among the AHRI 1350 deflection classes, D1 permits the least panel movement and D3 the most. {note}

+### Panel deflection matters because the panel is also half of every gasketed joint around it. A panel that bows under pressure opens the door gasket line and the panel-to-panel joint at the same time, so the leakage class measured on a stiff casing at low pressure is not the leakage the unit delivers once it is running at its real operating pressure. {note}

+### Sizing the casing for the fan's shutoff pressure rather than its operating pressure is what keeps a unit intact when a downstream damper fails closed or a smoke damper drops while the fan is running. {note}

+## Casing Sheet Materials {toc}

+### The interior liner material shall be as indicated in the datasheet.

+```datasheet

+label: Casing Interior Liner Material

+type: select

+options:

+ - "G90 galvanized steel"

+ - "G90 galvanized steel with a factory-applied coating"

+ - "Type 304 stainless steel"

+ - "Type 316 stainless steel"

+ - "Aluminum"

+default: "G90 galvanized steel"

+```

+### The exterior panel material shall be as indicated in the datasheet.

+```datasheet

+label: Casing Exterior Panel Material

+type: select

+options:

+ - "G90 galvanized steel, painted"

+ - "G90 galvanized steel, unpainted"

+ - "Type 304 stainless steel"

+ - "Aluminum"

+default: "G90 galvanized steel, painted"

+```

+### Galvanized steel sheet shall conform to ASTM A653 with a G90 coating designation as a minimum.

+### Interior surfaces that are wetted by condensate in normal operation shall be stainless steel, aluminum, or galvanized steel carrying a factory-applied coating rated for continuous exposure to condensate.

+### Uncoated galvanized steel is durable in a dry airstream and much less so under a continuous condensate film. The zinc layer is consumed rather than merely scratched, so the failure shows up as white corrosion product and then base metal perforation in the wettest part of the section, which is where the drain pan meets the coil. {note}

+### Exposed fasteners on interior surfaces in contact with the airstream shall be stainless steel.

+## Exterior Finish {toc}

+### The exterior finish system shall be as indicated in the datasheet.

+```datasheet

+label: Exterior Finish System

+type: select

+options:

+ - "Factory-applied powder coat over a treated substrate"

+ - "Factory-applied baked enamel over a treated substrate"

+ - "Corrosion-inhibiting epoxy primer with a polyester powder coat topcoat"

+ - "Unpainted galvanized or aluminum with no applied finish"

+default: manufacturer

+```

+### Where the datasheet leaves the finish system to the manufacturer, the manufacturer shall state in the submittal the system furnished and its dry film thickness.

+### Where the Contract Documents require a color selection, the color shall be selected by the Owner from the range the manufacturer offers for the finish system furnished, and the selection shall be made before the unit is released for fabrication.

+### Outdoor unit finishes shall have a total dry film thickness of not less than 3 mils.

+### Cut edges, field-drilled penetrations, and fasteners on outdoor units shall receive a zinc-rich touch-up coating before the unit is placed in service.

+## Access Doors {toc}

+### An access door shall be furnished at every section containing a component that requires periodic inspection, cleaning, adjustment, or replacement, including at minimum every fan section, filter section, coil section, mixing section, drain pan, humidifier section, and energy recovery section.

+### The access door construction shall be as indicated in the datasheet.

+```datasheet

+label: Access Door Construction

+type: select

+options:

+ - "Hinged insulated door with compression latches operable from both sides"

+ - "Hinged insulated door with compression latches operable from outside only"

+ - "Hinged insulated door with a sliding hardware set where the swing is obstructed"

+ - "Removable gasketed access panel"

+default: "Hinged insulated door with compression latches operable from both sides"

+```

+```datasheet

+label: Access Door Viewport

+type: radio

+options:

+ - "Sealed double-glazed viewport in each fan and coil section door"

+ - "Sealed double-glazed viewport in each fan section door"

+ - "No viewport"

+default: "No viewport"

+```

+```datasheet

+label: Interior Service Lighting

+type: radio

+options:

+ - "Factory-installed luminaires with an exterior switch and a marked disconnect in each accessible section"

+ - "Factory-installed luminaires with an exterior switch in each fan section"

+ - "No interior lighting"

+default: "No interior lighting"

+```

+### Access doors on sections a person can enter shall be openable from the inside without a tool whenever the latching hardware can be secured from the outside.

+### A door latch that can be secured from outside on a section large enough to enter is the mechanism behind entrapment in operating equipment. The inside release is what makes the section safe to work in, and it is the reason a double-sided latch set is not merely a convenience. {note}

+### Clear door opening dimensions shall be not less than 18 in. wide by 45 in. high for sections a person is expected to enter, and not less than 12 in. by 12 in. for sections served by reaching in.

+### Where a component is removed through a door, the clear door opening shall be large enough to pass that component.

+### Door gaskets shall be mechanically retained or bonded to the door and shall be replaceable without replacing the door.

+## Weather Protection for Outdoor Units {toc}

+### Requirements in this article apply where the datasheet selects an outdoor casing.

+### The unit roof shall be sloped to drain and shall extend beyond the casing wall at every edge.

+### Roof seams shall be located away from the low point of the slope and shall be sealed with a sealant rated for continuous exterior exposure and the design surface temperature range.

+### Outdoor air intakes and relief openings shall be furnished with weather hoods and moisture eliminators sized so that water is not carried into the unit at the design wind-driven rain condition.

+### Base rails shall be drainable and shall not create a standing water condition on the roof surface beneath the unit.

+### Doors on outdoor units shall be furnished with a rain lip or drip edge above the opening.

+### Electrical enclosures on outdoor units shall be rated for the exposure and shall be furnished with condensation heaters where the unit can be energized before the space it serves is conditioned.

+# Coils {toc}

+## Coil Rating and Certification {toc}

+### Coil performance shall be rated in accordance with ANSI/AHRI 410.

+### Published coil capacities shall be stated at the actual selected face velocity, entering conditions, fluid flow rate, and circuiting rather than at generic catalog conditions.

+### Coil selections shall be resubmitted where any of the entering conditions, the fluid temperatures, or the airflow change after the original selection.

+### An AHRI 410 rating certifies the heat transfer relationships of the coil, not the accuracy of the conditions someone typed into the selection program. The recurring failure is a certified selection made at an entering air temperature that the mixing section never produces, which is a coordination error the certification cannot catch. {note}

+## Coil Materials {toc}

+### Coil tube material shall be as indicated in the datasheet.

+```datasheet

+label: Coil Tube Material

+type: select

+options:

+ - "Copper"

+ - "Type 304 stainless steel"

+ - "Type 316 stainless steel"

+ - "Copper-nickel alloy"

+default: "Copper"

+```

+### Coil fin material and coating shall be as indicated in the datasheet.

+```datasheet

+label: Coil Fin Material and Coating

+type: select

+options:

+ - "Aluminum"

+ - "Aluminum with an applied epoxy coating"

+ - "Aluminum with an applied phenolic coating"

+ - "Aluminum with an electrodeposited coating"

+ - "Copper"

+ - "Copper with an applied epoxy coating"

+default: "Aluminum"

+```

+### Cooling coil casings and tube sheets shall be as indicated in the datasheet.

+```datasheet

+label: Cooling Coil Casing Material

+type: select

+options:

+ - "Type 304 stainless steel"

+ - "Type 316 stainless steel"

+ - "G90 galvanized steel"

+ - "Aluminum"

+default: "Type 304 stainless steel"

+```

+```datasheet

+label: Heating Coil Casing Material

+type: select

+options:

+ - "G90 galvanized steel"

+ - "Type 304 stainless steel"

+ - "Type 316 stainless steel"

+ - "Aluminum"

+default: "G90 galvanized steel"

+```

+### Aluminum fin stock in contact with copper tube forms a galvanic pair that stays benign while the fin surface is dry and becomes active once a persistent electrolyte film exists between them. Chloride from marine air and sulfur compounds from industrial and vehicular exhaust both supply that electrolyte, so the fin corrodes preferentially, the bond to the tube opens, and capacity falls while air-side pressure drop rises. Applied fin coatings and cupronickel construction both address the same mechanism at different cost. {note}

+### Where the datasheet selects a fin coating, the coating shall be applied after fin and tube assembly so that the tube-to-fin interface is coated.

+## Coil Pressure and Construction {toc}

+### Coils shall be rated for a working pressure not less than the value indicated in the datasheet and for a working temperature not less than the maximum fluid temperature the connected system can deliver.

+```datasheet

+label: Coil Working Pressure Rating

+type: range

+unit: psig

+options:

+ min: 150

+ max: 600

+ setpoints: [150, 200, 250, 300, 400, 600]

+default: 250

+```

+### The maximum cooling coil fin spacing shall be as indicated in the datasheet.

+```datasheet

+label: Maximum Cooling Coil Fin Spacing

+type: range

+unit: fins per inch

+options:

+ min: 4

+ max: 16

+ step: 1

+default: 12

+```

+### Coil headers shall be furnished with a manual air vent at the high point and a drain at the low point of each circuit.

+### Every coil shall be factory pressure tested and the test pressure shall be recorded on the coil.

+### Fin spacing trades heat transfer surface against cleanability and fouling tolerance. A tight fin pattern gets the same capacity from a smaller coil, and it also holds the condensate film longer, resists cleaning, and loses face area faster as it loads. On a coil that runs wet, the fin spacing effectively sets how often the coil has to be cleaned to keep its rated capacity. {note}

+## Cooling Coils {toc}

+### The cooling coil medium shall be as indicated in the datasheet.

+```datasheet

+label: Cooling Coil Medium

+type: radio

+options:

+ - "Chilled water"

+ - "Direct expansion refrigerant"

+ - "None"

+default: "Chilled water"

+```

+```datasheet

+label: Cooling Coil Entering Fluid Temperature

+type: range

+unit: °F

+drawing_ref: "design fluid temperatures as indicated on the mechanical schedules"

+options:

+ min: 30

+ max: 60

+ step: 1

+default: deferred

+```

+```datasheet

+label: Cooling Coil Leaving Fluid Temperature

+type: range

+unit: °F

+drawing_ref: "design fluid temperatures as indicated on the mechanical schedules"

+options:

+ min: 38

+ max: 80

+ step: 1

+default: deferred

+```

+```datasheet

+label: Maximum Cooling Coil Fluid-Side Pressure Drop

+type: range

+unit: ft w.g.

+options:

+ min: 2

+ max: 45

+ step: 1

+```

+### Hydronic cooling coils shall be circuited for counterflow, with the fluid entering at the leaving-air face of the coil.

+### Where the datasheet does not state a maximum fluid-side pressure drop, the manufacturer shall state the pressure drop of the selected coil, and the Engineer of Record shall confirm it against the pump head available.

+### Requirements in this article that address refrigerant circuiting apply where the datasheet selects a direct expansion coil.

+### Direct expansion coils shall be circuited with an interlaced or face-split arrangement matched to the capacity steps of the connected condensing unit, and the arrangement shall be shown in the submittal.

+### Direct expansion coils shall be furnished with a distributor sized for the design refrigerant flow, and the distributor and expansion device shall be selected together by the party responsible for the refrigeration circuit.

+### A direct expansion coil is part of a refrigeration circuit, so the coil, the distributor, the expansion device, and the compressor staging behave as one machine. A row-split arrangement lets an unloaded circuit sit in the airstream doing nothing but adding pressure drop; an interlaced arrangement keeps every part of the face active at every capacity step but needs matched distributors to avoid starving circuits at low load. {note}

+## Cooling Coil Face Velocity {toc}

+### The cooling coil face velocity at design airflow shall not exceed the value indicated in the datasheet.

+```datasheet

+label: Maximum Cooling Coil Face Velocity

+type: range

+unit: fpm

+options:

+ min: 200

+ max: 700

+ step: 10

+default: 500

+```

+### Where the selected face velocity exceeds 550 fpm, moisture eliminators shall be furnished downstream of the coil and the drain pan shall extend to the eliminator face.

+### Condensate on a cooling coil leaves the fin edge as droplets that the airstream then has to be slow enough not to carry away. The threshold is not sharp and it moves with fin spacing, fin surface treatment, and how wet the coil runs, but somewhere above roughly 500 to 550 fpm carryover starts and no amount of drain pan depth downstream will recover water that is already airborne and heading into the duct. {note}

+### Face velocity shall be calculated on the finned face area of the coil rather than on the casing cross-section.

+## Heating Coils {toc}

+### The heating coil medium shall be as indicated in the datasheet.

+```datasheet

+label: Heating Coil Medium

+type: select

+options:

+ - "Hot water"

+ - "Steam"

+ - "Electric resistance"

+ - "None"

+default: "Hot water"

+```

+```datasheet

+label: Heating Coil Entering Fluid Temperature

+type: range

+unit: °F

+drawing_ref: "design fluid temperatures as indicated on the mechanical schedules"

+options:

+ min: 90

+ max: 220

+ step: 5

+default: deferred

+```

+```datasheet

+label: Heating Coil Leaving Fluid Temperature

+type: range

+unit: °F

+drawing_ref: "design fluid temperatures as indicated on the mechanical schedules"

+options:

+ min: 70

+ max: 210

+ step: 5

+default: deferred

+```

+### Requirements in this article that address resistance elements apply where the datasheet selects an electric heating coil.

+### Electric heating coils shall be furnished with a primary automatic-reset thermal cutout and a secondary manual-reset thermal cutout, both listed for the application.

+### Electric heating coils shall be interlocked with the supply fan so that the elements cannot be energized without proven airflow, and the interlock shall be hardwired independently of the building automation system.

+### An airflow interlock that depends on the building automation system fails in the one scenario it exists for, which is the system being offline while the heater has power. The hardwired path is what makes the interlock a safety rather than a sequence. {note}

+## Steam Heating Coils {toc}

+### Requirements in this article apply where the datasheet selects a steam heating coil.

+### The steam coil type shall be as indicated in the datasheet.

+```datasheet

+label: Steam Coil Type

+type: radio

+options:

+ - "Distributing tube, non-freeze construction"

+ - "Standard single-tube construction"

+```

+### Where entering air below 40°F can reach the steam coil face, the coil shall be of distributing tube non-freeze construction.

+### Steam coils shall be pitched toward the return connection and shall be furnished with a condensate return connection at the low point of each coil.

+### Each steam coil shall be trapped separately, and coils shall not be manifolded into a shared trap.

+### Steam coils shall be controlled by modulating the steam supply pressure rather than by throttling the condensate return.

+### A steam coil freezes from the condensate side. When a control valve throttles the supply, the pressure inside the tube can fall below the pressure needed to push condensate through the trap, condensate stacks in the bottom tubes, and the first tube full of stationary water at sub-freezing entering air splits. A distributing tube carries steam the full length of the coil inside an inner tube and feeds it outward along the whole run, so every part of the outer tube stays hot at part load rather than only the end nearest the supply. {note}

+## Preheat Freeze Protection {toc}

+### The preheat freeze protection method shall be as indicated in the datasheet.

+```datasheet

+label: Preheat Coil Freeze Protection

+type: select

+options:

+ - "Constant coil flow with a modulating three-way valve"

+ - "Constant coil flow maintained by an injection pump"

+ - "Glycol solution in the preheat circuit"

+ - "Face and bypass dampers with a constant-capacity coil"

+ - "None"

+```

+### Where a hydronic preheat coil can see entering air below 35°F, the coil circuit shall maintain flow through every tube whenever the outdoor air damper is open.

+### A hydronic preheat coil with a two-way modulating valve is a freeze risk by construction, because the condition that calls for the least heat is the condition with the coldest air on the coil, and at low valve position the water in the tubes is nearly stationary. Every method in the field is a way of keeping water moving through the coil while still varying the heat it delivers, whether by recirculating around a three-way valve, injecting to hold flow, lowering the freezing point of the fluid, or moving the air around the coil instead of modulating the water. {note}

+### Glycol concentration and the resulting capacity correction shall be stated in the submittal where a glycol solution is selected.

+## Coil Access and Connections {toc}

+### Coils shall be removable from the unit without cutting tubes, disassembling adjacent sections, or removing the fan.

+### Coil connections shall pass through the casing in a gasketed, insulated penetration that maintains the leakage class of the section.

+### Coil connections shall be arranged so that the piping can be disconnected and the coil withdrawn from the service side of the unit.

+### Piping serving the coils shall conform to [[sync/hydronic-piping]].

+### Piping shall be independently supported within 12 in. of the coil connection, and no part of the connected piping weight or thermal movement shall be carried by the coil header.

+# Filtration {toc}

+## Filtration Stages {toc}

+### The number of filtration stages shall be as indicated in the datasheet.

+```datasheet

+label: Filtration Stages

+type: radio

+options:

+ - "Single stage"

+ - "Two stages, prefilter and final filter"

+ - "Three stages, prefilter, intermediate filter, and final filter"

+default: "Two stages, prefilter and final filter"

+```

+### Air delivered to an occupiable space shall pass through filtration of not less than MERV 8 upstream of every cooling coil and every other component with a wetted surface.

+### Where a final filter of MERV 13 or higher is furnished, a prefilter stage shall be furnished upstream of it.

+### A prefilter is an economic device rather than an air quality device. It removes the coarse fraction that would otherwise load the final filter, and because the coarse fraction is most of the mass and almost none of the health-relevant particle count, it extends the final filter's life at a fraction of the media cost. The stage count therefore follows from the final filter efficiency and the change-out economics, not from the cleanliness target. {note}

+### Filter media shall be listed to UL 900.

+## Filter Efficiency {toc}

+### Filter efficiency shall be rated in accordance with ANSI/ASHRAE 52.2 and shall be as indicated in the datasheet.

+```datasheet

+label: Prefilter Efficiency

+type: select

+options:

+ - "MERV 4"

+ - "MERV 6"

+ - "MERV 7"

+ - "MERV 8"

+ - "MERV 11"

+ - "No prefilter stage"

+default: "MERV 8"

+```

+```datasheet

+label: Final Filter Efficiency

+type: select

+options:

+ - "MERV 8"

+ - "MERV 11"

+ - "MERV 13"

+ - "MERV 14"

+ - "MERV 15"

+ - "MERV 16"

+ - "HEPA rated at 99.97% on 0.3 µm particles"

+ - "HEPA rated at 99.995% on the most penetrating particle size"

+default: "MERV 13"

+```

+### The fan selection shall accommodate the airside resistance of the selected filters at their change-out condition without falling below the design airflow.

+### The submittal shall state the initial resistance and the recommended change-out resistance of each filter stage at the design face velocity.

+### Filter efficiency and fan power are directly coupled. Moving from MERV 8 to MERV 13 typically adds a few tenths of an inch of water gauge across the filter bank at the change-out condition, and that increment is paid continuously by the fan for the life of the system. It is a real cost and a small one relative to the fan's total, but it has to be in the selection rather than discovered during balancing. {note}

+### Filter face velocity at design airflow shall not exceed the velocity at which the selected media is rated.

+## Filter Media and Frames {toc}

+### The final filter media configuration shall be as indicated in the datasheet.

+```datasheet

+label: Final Filter Media Configuration

+type: select

+options:

+ - "Pleated panel"

+ - "Rigid box with mini-pleat media"

+ - "Rigid box with deep-pleat media"

+ - "Extended surface pocket"

+ - "Cartridge"

+default: "Rigid box with mini-pleat media"

+```

+### The filter holding frame seal shall be as indicated in the datasheet.

+```datasheet

+label: Filter Holding Frame Seal

+type: select

+options:

+ - "Positive seating against a gasketed frame with spring clips"

+ - "Knife-edge frame against a gasketed filter"

+ - "Fluid-seal gel channel"

+ - "Clamped sealed housing with bag-in bag-out change provisions"

+default: "Positive seating against a gasketed frame with spring clips"

+```

+### Holding frames shall be continuous and rigid, and shall seal to the casing on all four sides so that no air path exists around the media.

+### Frame-to-filter sealing shall be achieved by mechanical contact pressure rather than by friction fit.

+### Bypass around the media is the dominant filtration defect in installed systems, and it is invisible at every point in the process except a measurement of what actually reaches the space. A bank of MERV 14 filters with a 1% leakage path around the frames delivers an in-place efficiency far below its media rating, because unfiltered air is a parallel path with almost no resistance while the media path has a great deal. {note}

+## Filter Access {toc}

+### The filter access arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Filter Access Arrangement

+type: radio

+options:

+ - "Side access through the casing"

+ - "Front access through the filter section face"

+ - "Side access from either side of the unit"

+ - "Walk-in access upstream of the filter bank"

+default: "Side access through the casing"

+```

+### Filters shall be removable and replaceable without tools.

+### The clear withdrawal space required to change filters shall be shown on the configuration drawing and shall be maintained clear of piping, conduit, and ductwork after installation.

+### Where the filter section is accessed by entering the unit, the walking surface shall be rated for the load of a person and shall not be the drain pan.

+## Filter Pressure Monitoring {toc}

+### Filter differential pressure monitoring shall be as indicated in the datasheet.

+```datasheet

+label: Filter Differential Pressure Monitoring

+type: select

+options:

+ - "Local differential pressure gauge at each stage"

+ - "Differential pressure transmitter at each stage reporting to the building automation system"

+ - "Local gauge and differential pressure transmitter at each stage"

+ - "Differential pressure switch with an adjustable setpoint at each stage"

+default: "Local differential pressure gauge at each stage"

+```

+### Pressure taps shall be installed upstream and downstream of each filter stage, in the plane of the media and clear of the frame.

+### Local indicating devices shall be readable from outside the unit without opening any door.

+### Each indicating device shall be labeled with the filter stage it serves and with the change-out resistance from the submittal.

+## High-Efficiency Particulate Air Filter Sections {toc}

+### Requirements in this article apply where the datasheet selects a HEPA final filter.

+### HEPA filters shall be installed in a sealed housing with a gasketed or fluid-seal frame, and shall not be installed in a slide-in track frame.

+### The housing shall include upstream and downstream test ports and an aerosol injection port permitting in-place leak testing of the installed filter and its seal.

+### Each installed HEPA filter and its housing seal shall be leak tested in place after installation, and the test report shall be a closeout submittal.

+### Where the airstream carries a hazard to maintenance personnel, the housing shall include bag-in bag-out change-out provisions.

+### A HEPA filter's rating is a property of the media measured at the factory, and the number that matters in a building is the in-place leak test of the installed assembly. That test is the only step that catches a pinhole in the media, a rolled gasket, or a frame that is not flat. {note}

+# Mixing Section and Dampers {toc}

+## Mixing Section Arrangement {toc}

+### The mixing section arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Mixing Section Arrangement

+type: select

+options:

+ - "Outdoor air, return air, and relief or exhaust air dampers"

+ - "Outdoor air and return air dampers"

+ - "Outdoor air damper only with no return air connection"

+ - "No outdoor air connection"

+default: "Outdoor air, return air, and relief or exhaust air dampers"

+```

+### Damper positions and the mixing section geometry shall be arranged so that the two airstreams are mixed before they reach the face of the first coil or the low-limit sensing element.

+### Where the mixing section geometry cannot achieve mixing before the coil face, an air blender shall be furnished.

+### Stratification in a mixing box is the source of several failures that look unrelated. The low-limit thermostat reads a warm layer while the coil face sees a cold one, so freeze protection does not trip until the coil has already split. The mixed air temperature sensor reads a single point in a plane that varies by tens of degrees, so the economizer control loop hunts. And the cold layer against a coil face produces localized condensation and frost on a coil that the average temperature says is safe. {note}

+## Damper Construction {toc}

+### The damper blade arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Damper Blade Arrangement

+type: radio

+options:

+ - "Opposed blade"

+ - "Parallel blade"

+```

+### Damper frames shall be galvanized steel, extruded aluminum, or stainless steel, and shall be rigid enough that the blades close against the seals without binding across the full frame width.

+### Damper blades shall be airfoil or double-skin construction, and single-skin flat blades shall not be furnished on dampers that modulate.

+### Blade edge seals shall be extruded synthetic elastomer, and jamb seals shall be flexible metal or elastomer.

+### Felt and fibrous seals shall not be furnished on any damper in the unit.

+### Opposed blades close toward each other, so the air leaving a partly open opposed-blade damper continues roughly straight and the flow-versus-position relationship stays closer to linear across the stroke. Parallel blades all rotate the same way, so a partly open parallel-blade damper throws the airstream to one side, which is unhelpful for control authority and useful for driving mixing in a mixing box. Where the damper is both the control device and the mixing device, those two effects point in opposite directions. {note}

+## Damper Leakage {toc}

+### Damper leakage shall be tested in accordance with ANSI/AMCA 500-D, and the leakage class shall be as indicated in the datasheet.

+```datasheet

+label: Outdoor and Relief Air Damper Leakage Class

+type: select

+options:

+ - "AMCA Class 1A"

+ - "AMCA Class 1"

+ - "AMCA Class 2"

+ - "AMCA Class 3"

+default: "AMCA Class 1A"

+```

+```datasheet

+label: Return Air Damper Leakage Class

+type: select

+options:

+ - "AMCA Class 1A"

+ - "AMCA Class 1"

+ - "AMCA Class 2"

+ - "AMCA Class 3"

+default: "AMCA Class 2"

+```

+### The AMCA leakage classes set the following maximum leakage at 1 in. w.g. differential pressure across the closed damper: {note}

+| Leakage class | Maximum leakage |

+|---------------|-----------------|

+| Class 1A | 3 cfm/ft² |

+| Class 1 | 4 cfm/ft² |

+| Class 2 | 10 cfm/ft² |

+| Class 3 | 40 cfm/ft² |

+### Damper leakage class shall be selected to meet or exceed the maximum leakage the energy code adopted for the project permits for the damper's service and the project climate zone.

+### Damper leakage is measured per square foot of damper face, so its consequence scales with the damper, and a large outdoor air damper on a unit that shuts down overnight in a cold climate is the case that matters. The leaked air arrives unconditioned, upstream of the coil, into a unit with no airflow, which is the exact condition a coil freezes in. {note}

+### Dampers shall be rated for a differential pressure not less than the casing pressure class and for a velocity not less than the design face velocity through the damper.

+## Damper Actuators {toc}

+### The damper actuator type shall be as indicated in the datasheet.

+```datasheet

+label: Damper Actuator Type

+type: select

+options:

+ - "Electronic modulating, spring return"

+ - "Electronic modulating, non-spring return"

+ - "Electronic two-position, spring return"

+ - "Electronic two-position, non-spring return"

+ - "Pneumatic modulating"

+default: "Electronic modulating, spring return"

+```

+### Actuators shall be direct-coupled to the damper shaft.

+### Actuators shall be sized for the torque required to seat the blades against the seals at the casing pressure class, with not less than 25% reserve torque.

+### Outdoor air and relief air dampers shall drive to the closed position on loss of control signal or loss of power.

+### Return air dampers shall drive to the open position on loss of control signal or loss of power.

+### The fail positions are chosen so that a unit that loses control still has a path for the fan to move air through and no path for outdoor air to reach an unheated coil. A unit that fails with the outdoor damper open and the return damper closed in January is the classic way to split a preheat coil during a power interruption. {note}

+### Actuators shall be mounted outside the airstream, or shall be rated for continuous operation in the airstream temperature and humidity range where mounting outside is not practical.

+## Minimum Outdoor Air Control {toc}

+### The minimum outdoor air control method shall be as indicated in the datasheet.

+```datasheet

+label: Minimum Outdoor Air Control Method

+type: select

+options:

+ - "Fixed minimum position stop on the outdoor air damper"

+ - "Separate minimum outdoor air damper sized for the minimum airflow"

+ - "Outdoor airflow measuring station with closed-loop damper control"

+ - "Demand-controlled ventilation using space carbon dioxide sensors"

+ - "Constant outdoor airflow maintained by a dedicated outdoor air unit upstream"

+```

+### Where an outdoor airflow measuring station is furnished, it shall be rated in accordance with ANSI/AMCA 610 and shall be accurate across the full range from the minimum to the maximum outdoor airflow indicated in the datasheet.

+### A large damper controlling a small flow is operating in the part of its stroke where a small position change produces a large flow change and where the flow also depends on the pressure across the damper. That is why a fixed minimum position holds the ventilation rate only under the conditions it was set at, and why a separate small damper or a measured closed loop are the two ways of getting a minimum outdoor airflow that survives a change in system pressure. {note}

+### Where the ventilation rate is set by a fixed minimum position, the position shall be established during balancing at the design supply airflow and recorded in the balance report.

+# Air-Side Economizer {toc}

+## Economizer Provision {toc}

+### The economizer provision shall be as indicated in the datasheet.

+```datasheet

+label: Air-Side Economizer

+type: radio

+options:

+ - "Air-side economizer with modulating outdoor, return, and relief dampers"

+ - "No air-side economizer"

+default: "Air-side economizer with modulating outdoor, return, and relief dampers"

+```

+### Where an economizer is furnished, the outdoor air damper, the return air damper, and the relief path shall be sized for 100% of the design supply airflow.

+### Where an economizer is furnished, the unit shall be capable of modulating from the minimum outdoor airflow to 100% outdoor air without exceeding the design fan power or the design building pressure.

+### An economizer is a sizing decision as much as a control decision. Dampers, relief path, and casing all have to pass the full supply airflow through the outdoor side, which is a different unit from one that only ever admits a ventilation fraction. Adding economizer capability to a unit after it is selected is usually not possible. {note}

+## High-Limit Shutoff Control {toc}

+### The economizer high-limit shutoff control type shall be as indicated in the datasheet.

+```datasheet

+label: Economizer High-Limit Shutoff Control

+type: select

+options:

+ - "Fixed dry-bulb"

+ - "Differential dry-bulb"

+ - "Fixed enthalpy with a fixed dry-bulb limit"

+ - "Differential enthalpy with a fixed dry-bulb limit"

+ - "Electronic enthalpy curve"

+```

+### The high-limit control type and its setpoints shall be permitted by the energy code adopted for the project for the project climate zone.

+```datasheet

+label: Fixed Dry-Bulb High-Limit Setpoint

+type: range

+unit: °F

+options:

+ min: 55

+ max: 80

+ step: 1

+```

+### Where the datasheet does not state a fixed dry-bulb setpoint, the setpoint shall be the value the adopted energy code prescribes for the project climate zone.

+### The high limit exists to stop the economizer before free cooling becomes an added cooling load. A dry-bulb limit compares only temperature, so in a humid climate it can admit outdoor air that is cooler than the return air and carries far more moisture, which the coil then has to remove. An enthalpy limit compares total heat and closes that gap, at the cost of a humidity sensor whose drift is harder to notice than a temperature sensor's. Which one is permitted, and at what setpoint, is set by the energy code for the climate zone rather than by preference. {note}

+### Economizer sensors shall be located where they read the condition being controlled, with the outdoor sensor shielded from solar gain and away from exhaust discharges.

+# Energy Recovery {toc}

+## Energy Recovery Device {toc}

+### The energy recovery device shall be as indicated in the datasheet.

+```datasheet

+label: Energy Recovery Device

+type: select

+options:

+ - "None"

+ - "Rotary wheel, sensible only"

+ - "Rotary wheel, total energy"

+ - "Fixed-plate sensible heat exchanger"

+ - "Fixed-plate membrane enthalpy exchanger"

+ - "Heat pipe"

+ - "Runaround coil loop with a pumped glycol circuit"

+```

+### Requirements in this article apply where the datasheet selects an energy recovery device.

+### Energy recovery performance shall be rated in accordance with ANSI/AHRI 1060 and tested in accordance with ANSI/ASHRAE 84.

+### The recovery effectiveness at design conditions shall be not less than the value indicated in the datasheet.

+```datasheet

+label: Minimum Energy Recovery Effectiveness

+type: range

+unit: '%'

+options:

+ min: 0

+ max: 85

+ step: 5

+default: 50

+```

+### The pressure drop the recovery device adds to both the supply and the exhaust airstreams shall be included in the fan selections and stated in the submittal.

+### A recovery device is a heat exchanger placed in series with two fans, so it collects its energy by spending fan power continuously. The recovery is worth more where the outdoor and exhaust conditions are far apart and the outdoor air fraction is high, and the fan penalty is the same either way, which is why the same device is a clear gain on a dedicated outdoor air unit and a marginal one on a mixed-air unit with a low ventilation fraction. {note}

+### A means of reducing or stopping recovery shall be furnished so that the device does not transfer heat into the supply airstream when the economizer is calling for free cooling.

+## Cross-Contamination Control {toc}

+### The exhaust air transfer ratio of the selected device shall be stated in the submittal.

+### Rotary wheels shall be furnished with a purge sector where the datasheet indicates one.

+```datasheet

+label: Rotary Wheel Purge Sector

+type: radio

+options:

+ - "Purge sector furnished"

+ - "No purge sector"

+default: "Purge sector furnished"

+```

+### Where the exhaust airstream carries a contaminant that is not acceptable in the supply airstream, the recovery device shall be of a type that provides no leakage path between the airstreams.

+### A rotary wheel carries a small volume of exhaust air trapped in its matrix across into the supply side on every revolution. A purge sector reduces that carryover by sweeping the matrix with outdoor air before it reaches the supply stream, but it does not eliminate it, which is why laboratory and isolation exhaust are usually recovered with a runaround loop or a plate exchanger instead of a wheel. {note}

+### The supply fan and the exhaust fan shall be arranged so that the supply side of the recovery device is at a higher static pressure than the exhaust side wherever leakage direction matters.

+## Frost Control {toc}

+### The frost control method shall be as indicated in the datasheet.

+```datasheet

+label: Energy Recovery Frost Control

+type: select

+options:

+ - "Wheel speed modulation"

+ - "Preheat coil upstream of the recovery device"

+ - "Outdoor air bypass around the recovery device"

+ - "Exhaust air bypass around the recovery device"

+ - "Timed defrost cycle"

+ - "None"

+```

+### The outdoor temperature at which frost control is initiated shall be established from the exhaust air condition and the effectiveness of the selected device, and shall be stated in the submittal.

+### Frost forms on the exhaust side of a recovery device when the exhaust air is cooled below its dew point and then below freezing on its way through the exchanger. The consequence is a rising exhaust pressure drop and eventually a blocked passage, and every control method works by raising the coldest surface temperature in the device, either by admitting less cold air, moving the matrix faster, or preheating. {note}

+# Humidifier Sections {toc}

+## Humidifier Provision {toc}

+### The humidifier section shall be as indicated in the datasheet.

+```datasheet

+label: Humidifier Section

+type: select

+options:

+ - "None"

+ - "Steam dispersion panel"

+ - "Steam dispersion tube manifold"

+ - "Evaporative media"

+ - "High-pressure water atomizing"

+ - "Ultrasonic"

+default: "None"

+```

+### Requirements in this article apply where the datasheet selects a humidifier section.

+### The humidifier section shall be furnished with a stainless steel liner and a stainless steel drain pan beneath the dispersion device.

+### The humidifier shall be interlocked with the supply fan so that it cannot operate without proven airflow.

+### A high-limit humidity sensor shall be installed in the supply duct downstream of the humidifier and shall stop humidification before the supply air reaches saturation.

+## Absorption and Drainage {toc}

+### The manufacturer shall state the absorption distance for the selected dispersion device at the design airflow and the design supply air condition.

+### No component, duct fitting, turning vane, sensor, or filter shall be located within the stated absorption distance downstream of the dispersion device.

+### The absorption distance is where the water is still liquid. Anything inside it gets wet, and in a duct that means a wetted surface downstream of the last filter, which is precisely the condition the filtration requirements exist to prevent. Steam dispersion panels exist because they shorten that distance to a fraction of a manifold's, which is what makes humidification possible in a short duct run. {note}

+### The section downstream of the humidifier shall drain to the humidifier drain pan, and that pan shall be piped and trapped independently of the cooling coil drain pan.

+# Drain Pans and Condensate {toc}

+## Drain Pan Construction {toc}

+### A drain pan shall be furnished beneath every cooling coil, every humidifier dispersion device, every energy recovery device that can condense, and every other section in which condensate can form.

+### The drain pan material shall be as indicated in the datasheet.

+```datasheet

+label: Drain Pan Material

+type: select

+options:

+ - "Type 304 stainless steel"

+ - "Type 316 stainless steel"

+ - "Galvanized steel with a factory-applied corrosion-resistant coating"

+ - "Aluminum"

+default: "Type 304 stainless steel"

+```

+### Drain pans shall be of welded or mechanically seamed construction with no fastener penetrating the wetted surface.

+### Drain pans shall be insulated on the underside where the surface beneath the pan can fall below the dew point of the surrounding air.

+### A drain pan that holds water between operating cycles is a warm, dark, nutrient-bearing reservoir in the supply airstream, which is the growth condition ANSI/ASHRAE 188 is written around. Every geometric requirement on the pan, the slope, the extent, and the connection height exists to make the pan empty rather than merely drain. {note}

+## Drain Pan Extent and Slope {toc}

+### The drain pan shall extend the full width of the coil section and shall extend beneath the coil headers, return bends, and any piping within the section.

+### The drain pan shall extend downstream of the leaving-air face of the coil by not less than one half of the coil height and not less than 6 in.

+### The drain pan shall be sloped in two planes toward the drain connection at not less than the slope indicated in the datasheet.

+```datasheet

+label: Minimum Drain Pan Slope

+type: range

+unit: in. per ft

+options:

+ min: 0.125

+ max: 0.5

+ setpoints: [0.125, 0.25, 0.375, 0.5]

+default: 0.125

+```

+### Where the section geometry produces more than one low point, a drain connection shall be furnished at each low point.

+### The pan shall be constructed so that no part of the wetted surface holds standing water when the unit is not operating.

+### The downstream extension catches condensate that leaves the fin edge into a moving airstream and lands some distance beyond the coil face. How far it travels depends on the face velocity, so a pan sized only to the coil footprint is adequate at a low face velocity and lets water past the pan lip at a high one, where it reaches the fan section, the duct, and the lining. {note}

+### The pan slope determines how fast the pan empties after the coil stops condensing, not whether it drains at all. A slope that clears the pan in minutes rather than hours is what closes the standing water window that biological growth needs, and steeper slopes cost only casing height. {note}

+## Drain Connections and Traps {toc}

+### The drain pan shall be furnished with a primary drain connection at the low point and a secondary overflow connection with its invert not less than 1 in. above the primary connection.

+### Drain connections shall be not smaller than 1 in. and shall be sized for the design condensate rate.

+### The condensate trap arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Condensate Trap

+type: radio

+options:

+ - "Factory-installed trap with a cleanout, integral to the unit base"

+ - "Field-installed trap by the installing contractor"

+default: "Field-installed trap by the installing contractor"

+```

+### The trap seal depth on a drain pan in a section below the surrounding pressure shall be not less than the maximum negative static pressure in that section, expressed in inches water gauge, plus 1 in.

+### The vertical distance between the pan outlet and the trap outlet on a drain pan in a section below the surrounding pressure shall be not less than twice the maximum negative static pressure in that section, expressed in inches water gauge.

+### A drain trap on a draw-through unit is holding water against the fan, not against a sewer. If the seal is shallower than the negative pressure in the section, the fan simply pulls the seal out, the pan stops draining, and the unit starts drawing unfiltered air backward through the drain line. The trap therefore has to be sized from the section's static pressure rather than from plumbing practice, and it is one of the few dimensions on the unit that changes if the fan selection changes. {note}

+### Traps shall be furnished with a cleanout or a union that permits disassembly for cleaning without cutting the drain line.

+### Traps shall be primed at startup and shall be provided with a means of priming that does not require entering the unit.

+### The condensate drain line shall be sloped not less than 1/8 in. per ft toward the point of disposal.

+# Vibration Isolation and Seismic Restraint {toc}

+## Isolation Arrangement {toc}

+### The vibration isolation arrangement shall be as indicated in the datasheet.

+```datasheet

+label: Vibration Isolation Arrangement

+type: select

+options:

+ - "Internal spring isolation of the fan assembly within the casing"

+ - "External spring floor isolators beneath the unit base"

+ - "External restrained spring floor isolators beneath the unit base"

+ - "External spring hanger isolators"

+ - "External elastomeric mounts"

+ - "Housekeeping pad with no isolators"

+default: "Internal spring isolation of the fan assembly within the casing"

+```

+### Where the fan assembly is internally isolated, the casing shall not be a load path between the isolated assembly and the unit base.

+### Isolating the fan inside the casing keeps the isolated mass small and the casing rigid, so the isolators are sized for the fan and motor rather than for the entire unit including its coils and water. Isolating the whole unit externally puts a much larger mass on the springs, which lowers the natural frequency for the same deflection but also means every duct, pipe, and conduit connection has to accommodate the movement of the entire unit. {note}

+## Isolator Selection {toc}

+### Isolators shall be selected for a static deflection at operating load not less than the value indicated in the datasheet.

+```datasheet

+label: Minimum Isolator Static Deflection

+type: range

+unit: in.

+options:

+ min: 0.25

+ max: 4

+ setpoints: [0.25, 0.35, 0.75, 1, 1.5, 2, 2.5, 3, 4]

+```

+### Isolators shall be selected so that the isolation system natural frequency is not more than one third of the lowest fan operating frequency in the control range.

+### Where the datasheet does not state a static deflection, the isolator selection shall be made from the natural frequency requirement, and the calculated natural frequency and isolation efficiency at the lowest operating speed shall be stated in the submittal.

+### Isolation depends on the ratio between the disturbing frequency and the natural frequency of the isolated system, and the natural frequency is set by the static deflection. A variable-speed fan changes the disturbing frequency continuously, so an isolator chosen for the design speed can be near resonance at the bottom of the turndown range. Selecting from the lowest operating speed rather than the design speed is what keeps the ratio above one across the whole range. {note}

+### Isolators shall operate within the load range for which they are rated at the installed load, and the installed operating height shall be verified after the unit is set and filled.

+### A structural engineer shall review the isolator selection where the unit is supported on a floor structure rather than on grade.

+## Flexible Connections {toc}

+### Every connection between an isolated assembly and the building structure, including ductwork, piping, conduit, and drain lines, shall be made through a flexible element.

+### The flexible duct connection material shall be as indicated in the datasheet.

+```datasheet

+label: Flexible Duct Connection Material

+type: select

+options:

+ - "Neoprene-coated woven glass fabric"

+ - "Silicone-coated woven glass fabric"

+ - "Vinyl-coated polyester fabric"

+ - "Elastomeric composite"

+default: "Neoprene-coated woven glass fabric"

+```

+### Flexible duct connection fabric shall be tested to UL 214 and shall be rated for the temperature and pressure of the airstream it serves.

+### Flexible duct connections shall have not less than 3 in. of clear fabric between the metal edges and shall be installed with the fabric slack in every operating condition.

+### Piping connections shall include not less than two flexible elements arranged in different planes.

+### Electrical conduit shall include not less than 18 in. of flexible conduit at the unit.

+### A single rigid connection to an isolated unit short-circuits the entire isolation system, and it does not matter which connection it is. A conduit run tight to the casing carries structure-borne vibration into the building exactly as effectively as a bolted duct flange, which is why the requirement covers every connection rather than only the ducts. {note}

+### Flexible connections shall not be used to correct misalignment between the unit and the connected service.

+## Seismic Restraint {toc}

+### Seismic restraint of the unit shall be designed for the project [[parameter: seismic-design-category]].

+### Where the applicable building code requires seismic restraint for the unit, restraints shall be designed in accordance with ASCE 7 for the component importance factor assigned to the unit.

+### Seismic restraints on isolated units shall permit the isolators to function through their normal operating range and shall engage only under seismic displacement.

+### Anchorage to the supporting structure shall be designed by an engineer licensed in the jurisdiction of the project, and the design shall state the forces delivered to the structure.

+### A snubber that touches the isolated unit in normal operation is a rigid connection, so a restraint installed without its design clearance quietly cancels the isolation it was installed alongside. The clearance is a set dimension rather than a tolerance, and it is worth verifying after the unit is filled and running. {note}

+# Controls Interface and Safeties {toc}

+## Control Configuration {toc}

+### The unit control configuration shall be as indicated in the datasheet.

+```datasheet

+label: Unit Control Configuration

+type: select

+options:

+ - "Factory-installed unit controller integrated with the building automation system"

+ - "Factory-installed unit controller operating stand-alone"

+ - "Factory-installed devices and wiring with control by the building automation system contractor"

+ - "Field-installed devices and control by the building automation system contractor"

+```

+### The party responsible for the sequence of operation shall be identified in the submittal, and the sequence shall be reviewed before any control device is released for fabrication.

+### A factory controller arrives tested with the equipment it controls and carries the manufacturer's own protective logic, and it also arrives with a fixed sequence and a proprietary tool for changing it. Field-engineered controls put the sequence in one place with the rest of the building and put the responsibility for protecting the equipment on the party that did not build it. The division matters most for the safeties, which have to work regardless of who wrote the sequence. {note}

+## Building Automation System Interface {toc}

+### The communication interface to the building automation system shall be as indicated in the datasheet.

+```datasheet

+label: Building Automation System Interface

+type: select

+options:

+ - "BACnet MS/TP"

+ - "BACnet/IP"

+ - "Modbus RTU"

+ - "Modbus TCP"

+ - "LonWorks FT-10"

+ - "Hardwired point-to-point interface with no network connection"

+```

+### The interface shall conform to [[sync/building-automation-system]].

+### The manufacturer shall furnish a complete point list for the interface, giving the object name, object type, engineering units, and read or write access for every exposed point.

+### Field control connections shall terminate on a labeled terminal block in an enclosure accessible without opening a section that is pressurized during operation.

+### Terminal designations on the unit shall match the designations in the submitted wiring diagram and in the point list.

+## Control Points {toc}

+### The control devices furnished with the unit shall be as indicated in the datasheet.

+```datasheet

+label: Control Devices Furnished with the Unit

+type: checkbox

+options:

+ - "Supply air temperature sensor"

+ - "Return air temperature sensor"

+ - "Mixed air temperature sensor"

+ - "Outdoor air temperature sensor"

+ - "Supply air humidity sensor"

+ - "Return air humidity sensor"

+ - "Outdoor air humidity sensor"

+ - "Supply duct static pressure sensor"

+ - "Coil leaving air temperature sensor at each coil"

+ - "Outdoor airflow measuring station"

+ - "Supply fan airflow measuring station"

+ - "Filter differential pressure device at each stage"

+ - "Fan status by differential pressure switch"

+ - "Fan status by drive feedback"

+ - "Drain pan high water level switch"

+ - "Low-limit temperature device"

+ - "Duct high static pressure switch"

+default: ["Supply air temperature sensor", "Return air temperature sensor", "Mixed air temperature sensor", "Filter differential pressure device at each stage", "Fan status by differential pressure switch", "Low-limit temperature device", "Duct high static pressure switch"]

+```

+### Every furnished device shall be accessible for calibration and replacement from a service position, and no device shall require entering an operating section to reach.

+### Sensors installed in an airstream that varies across the duct section shall be averaging elements rather than single-point elements.

+## Duct Smoke Detection {toc}

+### Duct smoke detection shall be furnished at the locations indicated in the datasheet and shall be installed in accordance with NFPA 90A and NFPA 72.

+```datasheet

+label: Duct Smoke Detector Locations

+type: checkbox

+options:

+ - "Supply air, downstream of the filters and the supply fan"

+ - "Return air, upstream of any outdoor air connection"

+ - "Return air at each story connection to a common return"

+ - "No duct smoke detection furnished with the unit"

+default: ["Supply air, downstream of the filters and the supply fan"]

+```

+### The responsibility for furnishing and installing duct smoke detectors shall be as indicated in the datasheet.

+```datasheet

+label: Duct Smoke Detector Responsibility

+type: select

+options:

+ - "Furnished and installed by the fire alarm contractor"

+ - "Furnished by the fire alarm contractor and installed by the mechanical contractor"

+ - "Furnished and installed by the mechanical contractor"

+ - "Factory-installed by the unit manufacturer"

+```

+### Detector sampling tubes shall span the duct or plenum cross-section and shall be oriented and sized in accordance with the detector manufacturer's instructions for that cross-section.

+### A sampling tube that is short for the duct it is in produces a reading from one part of the section, and a tube installed with its inlet holes facing the wrong way produces almost no sample at all. Either way the detector tests as functional on a puff of aerosol at the tube and does not detect a fire, which is why the tube dimension is an installation requirement rather than a detail. {note}

+### Smoke detection shall shut down the supply fan through a hardwired interlock that does not depend on the building automation system.

+## Freeze Protection {toc}

+### A low-limit temperature device shall be furnished downstream of the mixing section and upstream of the first heating or cooling coil on every unit that admits outdoor air.

+### The low-limit device type shall be as indicated in the datasheet.

+```datasheet

+label: Low-Limit Temperature Device

+type: select

+options:

+ - "Averaging element thermostat, manual reset"

+ - "Averaging element thermostat, automatic reset"

+ - "Temperature sensor array reporting to the building automation system"

+ - "None"

+default: "Averaging element thermostat, manual reset"

+```

+### Where an averaging element device is furnished, the element shall be arranged so that not less than 1 lin ft of element covers each 1 ft² of coil face area, distributed across the full face.

+### The low-limit device shall respond to the coldest portion of its sensing element rather than to the average of the element.

+### The low-limit device shall stop the supply fan, drive the outdoor air damper closed, and drive the heating coil control valve open when it trips.

+### The trip setpoint and any alarm setpoint shall be recorded in the startup report.

+### A single-point temperature device in a mixing section reports the temperature at one point in a plane that can vary by tens of degrees across its area, so its reading depends on where the installer happened to put it. An averaging element spread across the coil face does not average away a cold streak if the device responds to the coldest part of the element, and that response characteristic is what makes the device useful for freeze protection rather than for temperature control. {note}

+## Static Pressure Safety {toc}

+### A high static pressure safety device shall be furnished in the supply air section of every unit whose fan can develop a pressure exceeding the pressure class of the connected ductwork.

+### The high static pressure device shall stop the supply fan through a hardwired interlock and shall require manual reset.

+### A low static pressure safety device shall be furnished in the return or suction section of every unit whose fan can collapse the connected ductwork or the casing when a return path closes.

+### The setpoints of the static pressure safety devices shall be established from the pressure class of the connected ductwork and the casing pressure class, and shall be recorded in the startup report.

+# Factory Testing {toc}

+## Production Tests {toc}

+### Each unit shall receive the factory tests indicated in the datasheet before shipment.

+```datasheet

+label: Factory Tests Required

+type: checkbox

+options:

+ - "Fan airflow and static pressure at the design operating point"

+ - "Motor current at the design operating point"

+ - "Vibration measurement at the fan and motor bearings"

+ - "Casing leakage test at 1.5 times design static pressure"

+ - "Casing deflection measurement at design static pressure"

+ - "Drain pan water hold test"

+ - "Damper stroke and fail-position test"

+ - "Door and panel gasket seal verification under pressure"

+ - "Coil pressure test"

+ - "Electrical continuity and insulation resistance test"

+ - "Controls point-to-point verification"

+default: ["Fan airflow and static pressure at the design operating point", "Motor current at the design operating point", "Vibration measurement at the fan and motor bearings", "Drain pan water hold test", "Damper stroke and fail-position test", "Coil pressure test", "Electrical continuity and insulation resistance test"]

+```

+### Measured airflow and static pressure shall be within ±5% of the values published in the reviewed submittal.

+### The drain pan water hold test shall fill the pan to the overflow connection and shall show no leakage at any seam, connection, or penetration after 15 minutes.

+### A unit that fails any required test shall be corrected and retested, and the cost of the correction and of every retest shall be borne by the manufacturer.

+### No unit shall be shipped until every required test has been passed and the results recorded.

+## Run Test {toc}

+### Each unit shall be operated at design conditions for not less than the duration indicated in the datasheet.

+```datasheet

+label: Factory Run Test Duration

+type: range

+unit: hours

+options:

+ min: 0.25

+ max: 8

+ setpoints: [0.25, 0.5, 1, 2, 4, 8]

+```

+### Where the datasheet does not state a duration, the run test shall continue until bearing temperatures and motor current have been stable for 30 minutes.

+### Bearing housing temperature rise above ambient and vibration at each bearing shall be recorded at the start and at the end of the run test.

+### A bearing housing temperature rise exceeding 40°F above ambient, or a vibration reading that increases during the run, shall be corrected before shipment.

+### The run test is the only opportunity to find a balance or alignment defect while the unit is still on the factory floor with a crane over it. A bearing that heats or a vibration reading that climbs during the run is the signature of a defect that will not improve in service, and it is much cheaper to find there than after the unit is set, piped, and ducted. {note}

+## Test Witnessing {toc}

+### Factory test witnessing shall be as indicated in the datasheet.

+```datasheet

+label: Factory Test Witnessing

+type: radio

+options:

+ - "Unwitnessed, with a certified test report submitted"

+ - "Witnessed at the factory by the Owner's representative"

+ - "Witnessed remotely by live video with the instrumentation in view"

+default: "Unwitnessed, with a certified test report submitted"

+```

+### Where witnessed testing is selected, the manufacturer shall give not less than ten business days notice of test readiness and shall submit the test procedure for review before the test is scheduled.

+### Where witnessed testing is selected and the unit fails, the cost of the witness attending each retest shall be borne by the manufacturer.

+# Delivery, Storage, and Handling {toc}

+## Shipping Configuration {toc}

+### The shipping configuration shall be as indicated in the datasheet.

+```datasheet

+label: Shipping Configuration

+type: select

+options:

+ - "Single assembled piece"

+ - "Shipping sections with factory-applied joint gaskets and field-bolted flanges"

+ - "Shipping sections with field-applied joint sealant"

+ - "Knocked down for field assembly"

+```

+### The Contractor shall verify the rigging path from the point of delivery to the final location, including every door, corridor, stair, elevator, and structural opening, before the unit is released for fabrication.

+### Where the verified rigging path cannot pass the configuration selected in the datasheet, the Contractor shall notify the Engineer of Record before fabrication and shall propose a shipping split that the path can pass.

+### Field joints between shipping sections shall be made with the gasket and hardware the manufacturer furnishes for that joint, and shall be sealed to the leakage class specified for the section.

+### The shipping split is the one dimension on the unit that is set by the building rather than by the equipment, and it is the constraint most often confirmed after the order is placed. A unit that cannot reach its room is a total loss on the schedule, not a rework item. {note}

+## Protection in Transit and Storage {toc}

+### The protective packaging furnished for shipment shall be as indicated in the datasheet.

+```datasheet

+label: Shipping Protection

+type: select

+options:

+ - "Weather-resistant wrap on every section"

+ - "Palletized with corner protection and stretch wrap"

+ - "Crated"

+ - "Interior sections wrapped and openings sealed"

+default: manufacturer

+```

+### Openings in shipped sections shall be covered and sealed against water and debris until the connecting work is made.

+### Units shall be stored in a clean, dry, and heated space until they are set.

+### Where indoor storage is not available, units shall remain in their protective packaging, shall be supported clear of standing water, and shall have condensation heaters in electrical compartments energized.

+### Units stored outdoors for more than 30 days shall be inspected by the Contractor before installation for water intrusion, corrosion, and pest intrusion, and the inspection findings shall be reported in writing to the Owner.

+### Fan assemblies stored more than 30 days shall have the shaft rotated by hand through several revolutions at intervals not exceeding 30 days.

+### A bearing under a stationary load for months develops a wear mark at the loaded contact point because the lubricant film is squeezed out and does not re-form without motion. Rotating the shaft periodically moves the contact and is the difference between a fan that is quiet at startup and one that has to be rebuilt before it is ever commissioned. {note}

+# Installation {toc}

+## Rigging and Setting {toc}

+### Units shall be rigged using the lifting points, spreader arrangement, and rigging hardware the manufacturer designates.

+### Slings or chains shall not bear against casing panels, coil connections, or drain connections.

+### Units shall be set level within 1/8 in. over the unit length and within 1/8 in. across the unit width, and the drain pans shall be verified to slope to their connections after setting.

+### Shipping braces, shipping bolts, and transit restraints shall be removed after the unit is set and before the fan is operated.

+### The Contractor shall confirm in the startup report that every shipping restraint has been removed.

+### A shipping brace left in a fan assembly holds the isolated mass rigid against the casing, so the first start delivers the full unbalance force into the structure and into bearings that are not free to move. This is a same-day failure rather than a slow one. {note}

+## Service Clearances {toc}

+### The service clearances shown on the reviewed configuration drawing shall be maintained clear of piping, conduit, ductwork, and stored material after installation.

+### The coil pull clearance, the filter withdrawal clearance, and the fan and motor removal path shall remain unobstructed for the life of the installation.

+### Where a service clearance conflicts with other work, the conflict shall be resolved before either is installed, and the Engineer of Record shall make the initial determination of which work relocates.

+## Duct Connections {toc}

+### The unit-to-duct connection type shall be as indicated in the datasheet.

+```datasheet

+label: Unit-to-Duct Connection

+type: select

+options:

+ - "Factory flanged connection with a flexible connector"

+ - "Factory sheet metal collar with a flexible connector"

+ - "Field-fabricated transition with a flexible connector"

+default: "Factory flanged connection with a flexible connector"

+```

+### Connecting ductwork shall be independently supported so that no duct weight is carried by the unit casing.

+### Connecting ductwork shall be installed after the unit is set on its final supports or isolators.

+### Duct transitions at the unit shall conform to the SMACNA HVAC Duct Construction Standards and shall not exceed the transition angle at which the fan outlet loss published in the submittal remains valid.

+### A duct that leaves the fan discharge into an abrupt transition or an immediate elbow does not develop the velocity profile the fan was rated with, and the resulting system effect can consume a meaningful fraction of the fan's rated pressure. It shows up during balancing as a unit that will not make its airflow at a fan speed the curve says should be ample. {note}

+## Piping and Electrical Connections {toc}

+### Hydronic connections shall include a shutoff valve on the supply and the return at each coil so that the coil can be isolated without draining the system.

+### Coils shall be hydrostatically tested at 1.5 times the design working pressure, and not less than 150 psig, for not less than 2 hours after field piping connections are complete and before the unit is placed in service.

+### The condensate drain connection shall include a union or a cleanout that permits the trap to be disassembled without cutting the line.

+### Electrical connections shall be made in accordance with NFPA 70, and the unit disconnecting means shall be located within sight of the unit it serves.

+### Penetrations made in the field through the casing shall be sealed and touched up so that the leakage class and the corrosion protection of the section are maintained.

+# Startup, Commissioning, and Balancing {toc}

+## Startup Service {toc}

+### The startup service shall be as indicated in the datasheet.

+```datasheet

+label: Startup Service

+type: select

+options:

+ - "Startup performed by a factory-authorized service representative"

+ - "Startup performed by the installing contractor with factory technical support"

+ - "Startup performed by the installing contractor"

+default: "Startup performed by a factory-authorized service representative"

+```

+### Before the fan is energized, the Contractor shall verify that shipping restraints are removed, that the fan wheel turns freely without contact, that belt tension and sheave alignment are correct on belt drives, that motor rotation matches the direction marked on the fan, that access doors are closed and latched, that the drain trap is installed and primed, that flexible connections are installed, and that casing penetrations are sealed.

+### The fan shall be started at its lowest speed and shall be run for not less than 15 minutes while bearing temperature, motor current, and sound are observed before the speed is increased.

+### The startup report shall record the measured airflow, external static pressure, fan speed, motor current at each measured condition, bearing temperatures, and the setpoints of every safety device.

+## Functional Testing {toc}

+### The commissioning scope shall be as indicated in the datasheet.

+```datasheet

+label: Commissioning Scope

+type: checkbox

+options:

+ - "Manufacturer startup with a signed report"

+ - "Point-to-point verification of every control device"

+ - "Functional performance testing of the control sequences"

+ - "Verified trip of every safety device at its setpoint"

+ - "Economizer changeover verification across the high-limit setpoint"

+ - "Verification of drain pan drainage during operation"

+ - "Integrated testing with the fire alarm system"

+ - "Trend review over a seasonal period"

+default: ["Manufacturer startup with a signed report", "Point-to-point verification of every control device", "Functional performance testing of the control sequences", "Verified trip of every safety device at its setpoint", "Verification of drain pan drainage during operation", "Integrated testing with the fire alarm system"]

+```

+### Each safety device shall be tested by driving the condition it senses to its setpoint rather than by simulating the device output.

+### Testing a freeze protection device by shorting its contacts proves the wiring and nothing else. The failure modes that matter are an element installed in the wrong plane, a setpoint that drifted, and a device that responds to its average rather than its coldest point, none of which a contact closure test can find. {note}

+### Drain pan drainage shall be verified during operation, with the coil condensing and the fan at design speed, by observing continuous flow at the drain and no accumulation in the pan.

+## Air Balancing {toc}

+### Testing, adjusting, and balancing shall be performed in accordance with [[sync/testing-adjusting-and-balancing]] after startup is complete and after the control sequences have been verified.

+### Measured airflow after balancing shall be within the tolerance indicated in the datasheet of the design value.

+```datasheet

+label: Airflow Balancing Tolerance

+type: range

+unit: '%'

+options:

+ min: 0

+ max: 15

+ step: 1

+default: 10

+```

+### Where the design airflow cannot be achieved within the tolerance, the balancing agent shall report the measured fan speed, static pressure, and motor current, and the Engineer of Record shall determine the remedy.

+### Filters shall be clean and the filter differential pressure shall be recorded at the time of the final balance.

+### The balance report shall record the as-left fan speed, drive component designations for belt drives, airflow, static pressure at the unit inlet and discharge, motor current, and the outdoor air damper minimum position.

+# Identification and Labeling {toc}

+## Unit Nameplate {toc}

+### Each unit shall be furnished with a permanent nameplate on the exterior of the casing, mechanically fastened rather than adhered.

+```datasheet

+label: Unit Nameplate Material

+type: select

+options:

+ - "Laminated phenolic"

+ - "Stainless steel"

+ - "Anodized aluminum"

+default: "Laminated phenolic"

+```

+### The nameplate shall state the unit tag, the manufacturer, the model and serial number, the design supply airflow, the design external static pressure, the supply fan motor nameplate power, the electrical characteristics, and the date of manufacture.

+### The unit tag on the nameplate shall match the tag used in the Contract Documents and in the operation and maintenance manuals.

+## Section and Component Labeling {toc}

+### Each access door shall be labeled on its exterior with the section it opens.

+### Labels shall be legible from 5 ft.

+### Filter section doors shall be labeled with the filter efficiency and filter sizes the section holds, and shall be furnished with a holder for recording the date of each filter change.

+### Fan section doors shall be labeled with a warning that the section contains a rotating assembly.

+### Electrical enclosure doors shall contain a permanently mounted copy of the unit wiring diagram.

+### Control terminal strips shall be labeled to match the designations in the submitted point list and wiring diagram.

+# Warranty {toc}

+## Warranty Term {toc}

+### The manufacturer shall warrant each unit against defects in materials and workmanship for the terms indicated in the datasheet.

+```datasheet

+label: Equipment Parts Warranty Term

+type: range

+unit: years

+options:

+ min: 1

+ max: 10

+ setpoints: [1, 2, 3, 5, 10]

+default: 1

+```

+```datasheet

+label: Equipment Labor Warranty Term

+type: range

+unit: years

+options:

+ min: 0

+ max: 5

+ setpoints: [0, 1, 2, 3, 5]

+default: 1

+```

+```datasheet

+label: Warranty Start Milestone

+type: radio

+options:

+ - "Date of substantial completion"

+ - "Date the Owner takes beneficial use of the system"

+ - "Date of shipment"

+default: "Date of substantial completion"

+```

+### Parts and labor are separate commitments and they are commonly sold at different terms, which is why they are stated separately here. A parts-only extension transfers the cost of the component and leaves the Owner paying for the technician, the crane, and the downtime, so the two terms have to be read together to know what the coverage is actually worth. {note}

+### A component repaired or replaced under warranty shall carry a warranty for a full term from the date of the repair or for the remainder of the original term, whichever ends later.

+## Component Warranties {toc}

+### Coils shall be warranted against leakage and against defects in materials and workmanship for the term indicated in the datasheet.

+```datasheet

+label: Coil Warranty Term

+type: range

+unit: years

+options:

+ min: 1

+ max: 10

+ setpoints: [1, 2, 3, 5, 10]

+default: 1

+```

+```datasheet

+label: Fan and Motor Warranty Term

+type: range

+unit: years

+options:

+ min: 1

+ max: 10

+ setpoints: [1, 2, 3, 5, 10]

+default: 1

+```

+### The coil warranty shall not cover damage caused by water chemistry outside the range the manufacturer publishes, by freezing that results from system operation outside the design conditions, or by physical damage from tools or from filter service.

+### Where the coil manufacturer conditions its warranty on water chemistry, the party responsible for water treatment shall furnish the water quality records the warranty requires, and the responsible party shall be identified in the submittal.

+### Motor and drive manufacturers' warranties shall pass through to the Owner in addition to the unit warranty.

+### A coil warranty conditioned on water chemistry is only as good as the party that keeps the records. When nobody is named, the records do not exist, and the first coil failure turns into an argument the Owner loses on evidence rather than on merit. {note}

+## Warranty Service {toc}

+### The manufacturer shall maintain factory-trained service capability for the units furnished within the region of the project for the duration of the warranty term.

+### The manufacturer shall respond to a warranty notification within 2 business days.

+### Where a warranty repair requires removal or modification of adjacent work, the cost of removing and restoring that work shall be borne by the party responsible for the defect.

+### Restoration of adjacent work disturbed by a warranty repair shall match the pre-existing condition recorded in the informational submittal, and where no record was submitted, the Engineer of Record shall make the initial determination of the pre-existing condition.

+# Spare Parts {toc}

+## Spare Parts Furnished {toc}

+### The Contractor shall furnish the spare parts indicated in the datasheet at substantial completion.

+```datasheet

+label: Spare Parts Furnished

+type: checkbox

+options:

+ - "One complete set of filters of every type and size installed"

+ - "Two complete sets of filters of every type and size installed"

+ - "One complete set of drive belts for every belt-driven fan"

+ - "One spare sheave set for every belt-driven fan"

+ - "One set of door and panel gaskets for each unit"

+ - "One set of damper blade and jamb seals for each unit"

+ - "One spare fan bearing of each type installed"

+ - "One tube of the specified bearing grease with a grease gun"

+ - "One set of every fuse type installed"

+ - "One spare control sensor of each type installed"

+default: ["One complete set of filters of every type and size installed", "One complete set of drive belts for every belt-driven fan", "One set of every fuse type installed"]

+```

+### Spare parts shall be delivered in the manufacturer's packaging, labeled with the unit tag they serve and with the manufacturer's part designation.

+## Spare Parts Storage {toc}

+### Spare filters shall be stored in sealed packaging in a clean, dry location the Owner designates.

+### The Contractor shall furnish a written inventory of the spare parts delivered, correlating each item to the unit it serves and the location where it was stored.

+### The operation and maintenance manual shall include a filter change schedule derived from the initial and change-out resistances stated in the submittal.

View current revision