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Computer Room Air Conditioning Units

Written and maintained by SynC.

Rev5
IssuedOct 19, 2026
LicenseCC BY 4.0
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1 Scope

NOTE A computer room air conditioning unit is a cooling unit selected for a room full of heat rather than a room full of people: the load is almost entirely sensible, it runs every hour of the year, and the air it delivers goes to equipment intakes whose tolerance is written by the equipment maker. What separates it from a comfort unit is the sensible heat ratio it is built for, the control of humidity in both directions, the unit-to-unit coordination that keeps a room of units from fighting, and a rating standard that reports net sensible capacity rather than total. The industry calls the direct-expansion unit a CRAC and the chilled water unit a CRAH; this standard covers both under one set of decisions. (1.1)
NOTE The following are covered when they form part of the unit or are furnished with it: (1.2)
  • Cabinet, panels, liner, floor stand, and turning plenum
  • Cooling coil, and the control valve of a chilled water unit
  • Compressors, refrigerant circuit, expansion device, and refrigerant detection and mitigation provisions of a direct-expansion unit
  • Remote air-cooled condenser, water-cooled condenser, or glycol drycooler and pump package matched to the unit
  • Fans, motors, and airflow control
  • Humidifier, dehumidification mode, and reheat
  • Economizer section and its changeover controls
  • Filters and filter access
  • Drain pan, condensate connection, and condensate pump where furnished
  • Leak detection under and around the unit
  • Unit controller, sensing point, unit-to-unit teamwork, and the interface to the monitoring system
  • Factory testing, delivery, installation, startup, commissioning, identification, warranty, and spare parts
NOTE The following are outside this standard: (1.3)
  • Comfort cooling equipment for occupied space, covered by Split System Air ConditionersSplit-System Air Conditioners and Heat PumpsResolves to the current adopted revision.sync/split-system-air-conditioners, Packaged Rooftop UnitsPackaged Rooftop UnitsResolves to the current adopted revision.sync/packaged-rooftop-units, and Fan Coil UnitsFan-Coil UnitsResolves to the current adopted revision.sync/fan-coil-units
  • The chilled water plant, covered by ChillersChillersResolves to the current adopted revision.sync/chillers, and the cooling tower that serves a water-cooled unit, covered by Cooling TowersCooling TowersResolves to the current adopted revision.sync/cooling-towers
  • Chilled water, condenser water, and glycol piping from the plant or the drycooler to the unit connection, covered by Hydronic PipingHydronic PipingResolves to the current adopted revision.sync/hydronic-piping, the general-duty valves in it, covered by HVAC Piping ValvesGeneral-Duty Valves for HVAC PipingResolves to the current adopted revision.sync/hvac-piping-valves, and the balancing valves and strainers in it, covered by Hydronic SpecialtiesHydronic SpecialtiesResolves to the current adopted revision.sync/hydronic-specialties
  • Field-installed refrigerant piping between the unit and its remote condenser or drycooler, covered by Refrigerant PipingRefrigerant PipingResolves to the current adopted revision.sync/refrigerant-piping
  • Loop chemistry and the initial glycol charge, covered by HVAC Water TreatmentHVAC Water TreatmentResolves to the current adopted revision.sync/hvac-water-treatment and Hydronic Cleaning And FlushingHydronic System Cleaning and FlushingResolves to the current adopted revision.sync/hydronic-cleaning-and-flushing
  • Condensate drain piping, traps, and lift pumps beyond the pan outlet, covered by Condensate Drainage PipingHVAC Condensate Drainage PipingResolves to the current adopted revision.sync/condensate-drainage-piping
  • The raised access floor system and its airflow panels, covered by Raised Access FlooringRaised Access FlooringResolves to the current adopted revision.sync/raised-access-flooring
  • The room, its construction, and the environmental criteria it states, covered by Telecommunications Rooms And PathwaysTelecommunications Rooms and PathwaysResolves to the current adopted revision.sync/telecommunications-rooms-and-pathways and Electrical RoomsElectrical RoomsResolves to the current adopted revision.sync/electrical-rooms
  • The building automation system, its network, graphics, alarming, and sequences beyond the unit controller, covered by Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system, and control devices procured separately from the unit, covered by HVAC Controls InstrumentationHVAC Instrumentation and Control DevicesResolves to the current adopted revision.sync/hvac-controls-instrumentation
  • Variable frequency drives procured as separate assemblies, covered by HVAC Variable Frequency DrivesHVAC Variable Frequency DrivesResolves to the current adopted revision.sync/hvac-variable-frequency-drives
  • Vibration isolators and seismic restraint devices, covered by Vibration Isolation And Seismic RestraintVibration Isolation and Seismic RestraintResolves to the current adopted revision.sync/vibration-isolation-and-seismic-restraint
  • Field-applied insulation of piping, covered by Mechanical InsulationMechanical InsulationResolves to the current adopted revision.sync/mechanical-insulation
  • The fire alarm system that signals the unit, covered by Fire Alarm SystemsFire Alarm SystemsResolves to the current adopted revision.sync/fire-alarm-systems, and the clean agent system that protects the room, covered by Clean Agent Fire SuppressionClean Agent Fire Suppression SystemsResolves to the current adopted revision.sync/clean-agent-fire-suppression
  • Walk-in, reach-in, and display refrigeration, covered by Refrigeration EquipmentCommercial Refrigeration EquipmentResolves to the current adopted revision.sync/refrigeration-equipment
  • Testing, adjusting, and balancing of the completed systems, covered by Testing Adjusting And BalancingTesting, Adjusting, and Balancing for HVACResolves to the current adopted revision.sync/testing-adjusting-and-balancing
  • Hot-aisle and cold-aisle containment, rear-door heat exchangers mounted on equipment racks, and direct-to-chip and immersion liquid cooling, which are not covered by any standard in this library
NOTE A computer room unit conditions recirculated room air and delivers no outdoor air. Where the room is occupied often enough to need ventilation, or is to be held at a positive pressure, that air comes from other equipment, and nothing in this standard satisfies a ventilation requirement on its own. (1.4)
1.5 Each unit, together with the remote condenser or drycooler and pump package matched to it, shall be furnished by a single manufacturer, who shall be responsible for the refrigeration, air-side, humidity, and control performance of the assembly as a whole.
NOTE Per-tag quantities are scheduled and project-wide policy is selected in the datasheet. Capacities, airflows, static pressures, entering conditions, water temperatures, and electrical characteristics vary with every unit on the project and live on the mechanical equipment schedule; the configuration, construction, control, and warranty decisions that apply to every unit on the project are made once here. (1.6)
1.7 Where a requirement of this standard conflicts with a requirement of a standard that governs a connected system, the Engineer of Record shall make the initial determination of which requirement governs.

2 Referenced Standards

2.1 Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
ANSI/AHRI 1360 (I-P) Performance Rating of Computer and Data Processing Room Air Conditioners
ANSI/ASHRAE 127 Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners
ANSI/AHRI 410 Performance Rating of Forced-Circulation Air-Cooling and Air-Heating Coils
ANSI/ASHRAE/IES 90.4 Energy Standard for Data Centers
ANSI/ASHRAE/IES 90.1 Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings
ASHRAE TC 9.9 Thermal Guidelines for Data Processing Environments
ANSI/ASHRAE 62.1 Ventilation and Acceptable Indoor Air Quality
ANSI/ASHRAE 15 Safety Standard for Refrigeration Systems
ANSI/ASHRAE 34 Designation and Safety Classification of Refrigerants
ANSI/ASHRAE 52.2 Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size
ANSI/ASHRAE 202 Commissioning Process for Buildings and Systems
ANSI/AMCA 210 / ANSI/ASHRAE 51 Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating
ANSI/AMCA 300 Reverberant Room Method for Sound Testing of Fans
NFPA 70 National Electrical Code
NFPA 72 National Fire Alarm and Signaling Code
NFPA 75 Standard for the Fire Protection of Information Technology Equipment
NFPA 90A Standard for the Installation of Air-Conditioning and Ventilating Systems
UL 60335-2-40 Household and Similar Electrical Appliances, Safety, Part 2-40: Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers
UL 1995 Heating and Cooling Equipment
UL 998 Humidifiers
UL 508A Industrial Control Panels
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
NEMA MG 1 Motors and Generators
ASTM A653 Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process
ASTM A240 Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip
ASTM B75 Standard Specification for Seamless Copper Tube
ASTM B117 Standard Practice for Operating Salt Spray (Fog) Apparatus
ASCE/SEI 7 Minimum Design Loads and Associated Criteria for Buildings and Other Structures
10 CFR Part 431 Energy Efficiency Program for Certain Commercial and Industrial Equipment
40 CFR Part 82 Subpart F Recycling and Emissions Reduction
40 CFR Part 84 Phasedown of Hydrofluorocarbons, Technology Transition

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for the Engineer of Record's review and return, and shall not release any unit for fabrication until the submittal covering it has been reviewed and returned:
  • Unit schedule keyed to the mechanical drawings, listing for each tag the cooling type, airflow arrangement, net sensible and total cooling capacity, airflow, external static pressure, entering air condition, entering fluid or condensing condition, fan and compressor data, humidifier and reheat capacity where furnished, electrical characteristics, and operating weight
  • Certified performance data for each unit configuration under AHRI 1360, giving net sensible cooling capacity, net total cooling capacity, airflow, and sensible coefficient of performance at the rating conditions, with the certification program identified
  • Capacity selection data correcting the certified rating to the scheduled entering air condition, the scheduled entering water or glycol temperature or the design condensing condition, and the scheduled airflow, with the coil rows, fin spacing, and air-side and water-side pressure drop at that selection
  • Fan data giving fan type, quantity, motor type and nameplate power, the fan input power at the design operating point, and the airflow control range, derived from testing in accordance with ANSI/AMCA 210
  • Sound power data in octave bands at the design operating point, derived from testing in accordance with ANSI/AMCA 300
  • Compressor data for direct-expansion units giving type, quantity, capacity control method, and the minimum capacity step or modulation range
  • Refrigerant designation, safety group, and factory charge by circuit, and where a refrigerant detection system is furnished, the sensor locations, the mitigation sequence, and the charge limit the listing establishes
  • Remote condenser, water-cooled condenser, or drycooler and pump package data giving capacity at the design ambient or entering fluid temperature, fan or pump data, head pressure control provisions, glycol concentration, and the refrigerant or glycol charge
  • Economizer section data giving the economizer type, its capacity at the changeover condition, the changeover sequence, and the hours of economizer operation claimed in the energy compliance documentation
  • Humidifier data giving type, capacity, water quality requirement, supply and drain connection sizes, and electrical load, and reheat data giving source, capacity, and stages
  • Filter data giving efficiency rating, depth, quantity and size per unit, initial resistance, and recommended change-out resistance
  • Drain pan and condensate data giving pan material, slope, connection size, and the condensate pump where furnished
  • Leak detection data giving the detector type, the sensed area, the alarm contacts, and any automatic valve closure
  • Unit controller data giving the control configuration, the sensing point, the teamwork group arrangement, the communication interface, and a complete point list with object names, types, units, and read or write access
  • Electrical data giving minimum circuit ampacity, maximum overcurrent protective device, short-circuit current rating of the control panel, dual power input arrangement where furnished, and the wiring diagram with field termination points
  • Energy compliance documentation showing how the unit selection satisfies Adopted Energy CodeAdopted Energy CodeParameterEach project supplies its own value.adopted-energy-code for the computer room, including any economizer exception relied on
  • Seismic restraint calculations for the unit and the remote heat rejection equipment, bearing the seal of an engineer licensed in the jurisdiction of the project, where restraint is required
  • Shop drawings showing each unit and its remote heat rejection equipment in plan and section with every field connection point dimensioned, the floor stand height and plenum cutout, the required service clearances, and the access panel locations
Action Submittals Requiredcheckbox
☑ Unit schedule keyed to the mechanical drawings
☑ Certified performance data under AHRI 1360
☑ Capacity selection data at the scheduled conditions
☑ Fan data with fan input power
☑ Sound power data
☑ Compressor and capacity control data
☑ Refrigerant, charge, and detection system data
☑ Remote condenser, water-cooled condenser, or drycooler and pump package data
☑ Economizer section data
☑ Humidifier and reheat data
☑ Filter data
☑ Drain pan and condensate data
☑ Leak detection data
☑ Unit controller data and point list
☑ Electrical data and wiring diagram
☑ Energy compliance documentation
☐ Seismic restraint calculations
☑ Shop drawings with clearances and field connections
3.1.2 Where the Contractor proposes a unit from a manufacturer other than the one on which the design was based, the submittal shall include a side-by-side comparison of net sensible capacity at the scheduled conditions, airflow at the scheduled external static pressure, fan input power, sound power, refrigerant and charge, and the cabinet dimensions, floor stand, and connection locations of the proposed and the scheduled unit.
3.1.3 Where a proposed substitution changes the cabinet dimensions, the connection locations, the plenum cutout, or the required service clearance of any unit, the submittal shall identify every floor, piping, electrical, and rack layout coordination item affected.

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following for information at the times indicated in each item:
  • Refrigerant handling certification under 40 CFR Part 82 Subpart F, submitted before any refrigerant circuit is opened, for every individual who will open, evacuate, charge, or recover a circuit on the project
  • Evidence of training in mildly flammable refrigerant handling, submitted before any such circuit is opened, for every individual who will work on a unit carrying a refrigerant in a flammable safety group
  • Rigging plan for any unit or remote heat rejection equipment that cannot be moved to its position by hand or pallet jack, submitted before the unit ships
  • Manufacturer's field service report for each site visit made during the warranty period
Informational Submittals Requiredcheckbox
☑ Refrigerant handling certifications
☐ Flammable refrigerant training records
☐ Rigging plan before shipment
☑ Field service reports during the warranty period

3.3 Closeout Submittals

3.3.1 Before the date of Substantial Completion, the Contractor shall submit the following:
  • Operation and maintenance manuals for each unit, indexed by unit tag, containing installation, operation, maintenance, and troubleshooting instructions, a parts list for every furnished component, the controller programming reference, and the maintenance schedule for filters, humidifier consumables, condensate system, leak detection, and refrigerant detection sensors
  • As-built unit schedule recording every field substitution and every field modification to the submitted configuration, together with the review documentation for each
  • As-built wiring diagrams and the monitoring system point list with the terminal designations used on the unit
  • Certified factory test report for each unit
  • Startup report for each unit signed by the person who performed the startup, recording the refrigerant charge by circuit, operating pressures and temperatures, glycol concentration where applicable, fan speeds, motor currents, and the setpoint of every safety device
  • Commissioning record demonstrating the control sequence, teamwork operation, redundancy failover, economizer changeover, humidity control, leak detection, fire protection interlock, and refrigerant detection and mitigation where furnished
  • Record of the filter media installed at Substantial Completion, giving efficiency rating, quantity, size, and installation date
  • Warranty documentation correlating each unit serial number to its installation date and to the expiration date of the unit, compressor, and installation warranties
  • Signed receipt from the Owner for the spare parts delivered
Closeout Submittals Requiredcheckbox
☑ Operation and maintenance manuals indexed by unit tag
☑ As-built unit schedule with field modifications
☑ As-built wiring diagrams and point list
☑ Certified factory test report for each unit
☑ Signed startup report for each unit
☑ Commissioning record
☑ Installed filter media record
☑ Warranty documentation correlated to serial numbers
☑ Spare parts receipt

4 Quality Assurance

4.1 Manufacturer Qualifications

4.1.1 Units shall be produced by a manufacturer that has continuously produced precision cooling units for data processing and telecommunications rooms for not less than the number of years indicated in the datasheet.
Manufacturer Experiencerange
Not less than
years
025
Default: 5 years
4.1.2 The manufacturer shall make replacement fans, compressors, coils, control valves, humidifier components, controllers, sensors, and filters available for the units furnished for not less than ten years after the date of manufacture.
4.1.3 All units on the project, together with their remote heat rejection equipment, shall be furnished by a single manufacturer so that the controller, the teamwork network, the service access pattern, and the spare parts inventory are common across the installation.
4.1.4 Where the Contract Documents divide the project into separately bid phases or buildings, the single-manufacturer requirement applies within each phase or building rather than across the project.
NOTE 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 prepared to accept a well-capitalized new manufacturer can set the requirement to zero and rely on the certification, testing, and warranty requirements instead. (4.1.5)

4.2 Basis of Published Performance Data

4.2.1 The basis on which the performance of each unit configuration is established shall be as indicated in the datasheet.
Basis of Certified Performance Ratingsradio
● AHRI 1360 certified ratings for every unit configuration furnished
○ AHRI 1360 certified ratings, with independent laboratory test data by the ASHRAE 127 method accepted for a configuration outside the certified range
○ Independent laboratory test data by the ASHRAE 127 method for every unit configuration furnished
4.2.2 Net sensible cooling capacity, net total cooling capacity, airflow, and sensible coefficient of performance cited for any unit shall be established by the selected basis at the standard rating conditions of ANSI/AHRI 1360 and corrected to the scheduled conditions by the manufacturer's published selection method.
4.2.3 The certification mark or the independent laboratory test report reference, as applicable to the basis selected, shall appear on the product data submitted for each unit configuration.
4.2.4 Each unit shall meet or exceed the minimum sensible coefficient of performance 10 CFR Part 431 requires for a computer room air conditioner of its net sensible capacity, cooling type, and airflow arrangement.
NOTE The rating standard for this equipment was written because a comfort rating does not describe it: a comfort rating reports total capacity at a wet entering condition and a seasonal efficiency, while a computer room unit is bought for sensible capacity at a dry entering condition, net of its own fan heat, running at full load every hour. The certification program covers a defined range of sizes and configurations, and a manufacturer in the program can still catalog a large chilled water unit, an in-row unit, or a dual-source unit outside that range. Ratings inside the range are verified by a third party on a sampling basis, while ratings outside it rest on the manufacturer's own test data, which is the difference the engineer is buying when the basis is selected. (4.2.5)
4.2.6 Where the parties disagree whether a proposed unit configuration falls within the certified range, the Engineer of Record shall make the initial determination.

4.3 Product Listing and Labeling

4.3.1 The complete unit, including every factory-installed electrical and refrigerant-system component, shall be listed and labeled by a Nationally Recognized Testing Laboratory under the standard indicated in the datasheet.
Unit Safety Listing Standardradio
○ UL 60335-2-40
○ UL 1995
4.3.2 A unit charged with a refrigerant in a flammable safety group shall be listed under UL 60335-2-40.
4.3.3 Units listed to UL 1995 are acceptable only where the refrigerant is in a nonflammable safety group and the Authority Having Jurisdiction accepts that listing for the equipment furnished.
NOTE UL 60335-2-40 is the listing standard that contains the charge limits, the refrigerant detection requirements, and the mitigation logic for mildly flammable refrigerants, which is why a flammable-refrigerant unit cannot be listed under the older standard. For a nonflammable refrigerant or a chilled water unit, both listings cover the same hazards and the choice follows the manufacturer's certification history and what the Authority Having Jurisdiction has seen before. (4.3.4)
4.3.5 Humidifiers furnished within the unit shall be listed under UL 998 or as part of the unit listing.
4.3.6 Factory-wired control panels shall be listed to UL 508A, and each panel shall bear a label giving its short-circuit current rating.
4.3.7 The listing label shall be affixed to the cabinet exterior in a location that remains visible after installation.

4.4 Refrigerant Handling Qualification

4.4.1 Refrigerant circuits shall be opened, evacuated, charged, and recovered only by an individual certified under 40 CFR Part 82 Subpart F.
4.4.2 Where the unit carries a refrigerant in a flammable safety group under ASHRAE 34, the individuals working on the circuit shall have completed training covering the handling, storage, leak response, and tool requirements that apply to that refrigerant.
4.4.3 Recovery machines, vacuum pumps, manifolds, leak detectors, and charging equipment used on a circuit carrying a refrigerant in a flammable safety group shall be rated by their makers for that service.

4.5 Pre-Installation Conference

4.5.1 Before installation of the units begins, the Contractor shall convene a pre-installation conference attended by the mechanical, piping, controls, electrical, and raised floor subcontractors, the fire protection installer, the testing and balancing agent, the commissioning authority where one is engaged, and the Owner's data center operations representative.
4.5.2 The pre-installation conference agenda shall include the floor cutout and floor stand coordination at each unit, the service clearances against the rack layout, the piping route and the leak detection along it, the remote condenser and drycooler setting and the refrigerant and glycol piping route, the controls interface and point responsibility, the fire protection interlock, the power source assignment of each unit, and the startup and commissioning schedule.
NOTE A computer room is laid out to the inch, and the unit, its floor cutout, its piping, and the racks it serves all compete for the same floor. The conference is where a unit that cannot be pulled out past a rack row, a floor cutout that lands on a pedestal, and a leak detection cable that was never routed are found once rather than discovered under a live load. (4.5.3)

5 Service Conditions and Design Basis

5.1 Room Environmental Envelope

5.1.1 The envelope the units shall hold at the equipment air intakes shall be as indicated in the datasheet, defined by the environmental class the ASHRAE TC 9.9 Thermal Guidelines publish for the installed equipment.
Controlled Environmental Enveloperadio
● Recommended envelope of the ASHRAE TC 9.9 Thermal Guidelines
○ Allowable envelope for the environmental class of the installed equipment
5.1.2 The environmental class of the installed equipment, the room setpoints, and the alarm limits shall be as indicated on the sequence of operation.
5.1.4 The supply air temperature setpoint shall be as indicated in the datasheet.
Supply Air Temperature Setpointrange
°F
5595
5.1.5 The supply air temperature setpoint shall lie within the envelope selected in the datasheet after allowing for the temperature rise between the unit discharge and the farthest equipment intake it serves.
5.1.6 Where the datasheet does not state a supply air temperature setpoint, the setpoint shall be as indicated in the sequence of operation.
NOTE Every degree the supply temperature is raised raises the chilled water or evaporating temperature the coil can run at, which raises plant efficiency and adds economizer hours, and every degree is also a degree closer to the top of the envelope at the intake farthest from the unit. The setpoint is selected against the measured or modeled rise across the room, not against the unit discharge alone. (5.1.7)

5.2 Entering Conditions and Site Data

5.2.1 The entering air dry-bulb temperature and humidity, the entering chilled water or glycol temperature and flow where applicable, and the design condensing condition of each unit shall be as indicated on the mechanical equipment schedule.
5.2.2 Each remote air-cooled condenser and each glycol drycooler shall deliver the heat rejection the matched unit needs at its scheduled net sensible capacity at Site Ambient Temperature MaximumSite Ambient Temperature MaximumParameterEach project supplies its own value.site-ambient-temperature-maximum with the coil clean.
5.2.3 Each remote air-cooled condenser shall be furnished with head pressure control that holds the matched unit in stable operation down to Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum.
5.2.4 Cooling, airflow, fan, condenser, drycooler, and motor ratings shall be corrected for AltitudeAltitudeParameterEach project supplies its own value.altitude in accordance with the manufacturer's published correction factors, and the corrected ratings shall be the values published in the submittal.
NOTE The outdoor equipment of a computer room unit runs on the hottest afternoon and the coldest night of the year, because the room's load does not follow the weather. Air-cooled condensing capacity falls as the outdoor temperature rises, and a condenser without head pressure control floods the circuit on a cold night and trips the unit on low pressure when the room needs it exactly as much as in July. (5.2.5)

5.3 Installation Environment

5.3.1 Units are indoor equipment and shall not be installed outdoors or in any location exposed to precipitation, wind-driven moisture, or freezing temperatures.
5.3.2 The control enclosure rating of the unit shall be as indicated in the datasheet.
Control Enclosure Ratingselect
NEMA Type 1
NEMA Type 12
NEMA Type 4X
5.3.3 Control enclosures on units installed in a space subject to dripping from piping or structure above shall be rated NEMA Type 12 or higher.
5.3.4 Control enclosures on units installed in a space subject to a corrosive atmosphere, including a battery room or a space open to an industrial process, shall be rated NEMA Type 4X.
5.3.5 The electrical enclosure of each remote air-cooled condenser and glycol drycooler shall be rated NEMA Type 3R or higher.
NOTE A computer room unit sits in a clean, conditioned room, and the general-purpose enclosure inside the cabinet is the right answer for nearly every one of them. The dust-tight enclosure keeps a drip from a sweating chilled water main above the unit off the terminal strip, and the corrosion-resistant enclosure keeps a battery room or process atmosphere off the contacts, at the cost of an enclosure that is harder to open for service. (5.3.6)

6 Unit Configuration

NOTE The products in the market are combinations of a small number of independent decisions: how the unit rejects its heat, which way the air moves through it and where it stands, how much of the room's load a single failure removes, and whether the units act as a group. Selecting each decision separately keeps every combination the catalogs offer available and keeps each decision queryable on its own. (6.1)

6.2 Cooling Type

6.2.1 The cooling type shall be as indicated in the datasheet.
Cooling Typeselect
Direct expansion, air-cooled, with a remote air-cooled condenser
Direct expansion, water-cooled, with a water-cooled condenser in the unit on a condenser water loop
Direct expansion, glycol-cooled, with a fluid-cooled condenser in the unit served by a remote drycooler
Chilled water, with a chilled water coil served by a central plant
Dual cooling source, with a chilled water coil and a direct-expansion circuit in one unit
NOTE An air-cooled direct-expansion unit needs nothing from the building but power and a place to stand a condenser, which is why it serves the room with no plant and the telecommunications room in a building whose plant is not allowed to carry it; its capacity falls on the hottest day, and every unit is its own refrigeration machine to be serviced. A water-cooled unit holds capacity in any weather and puts its heat into a condenser water loop, and it brings a cooling tower, condenser water pumps, and water treatment with it. A glycol-cooled unit replaces the tower with a drycooler that freezes safely and uses no water, and it pays for that with a pump package, a glycol loop, and a fluid temperature that follows the dry bulb. A chilled water unit carries no compressor, which removes the most failure-prone and energy-consuming component from the room and puts it in a plant that can be optimized centrally, and it makes the room's cooling only as reliable as the plant. A dual-source unit runs on chilled water and falls back to its own compressor when the plant is lost, which is bought with the cost and the cabinet of both. (6.2.2)
6.2.3 Requirements in the articles of this standard that address compressors, the refrigerant circuit, refrigerant detection, and the remote condenser or drycooler apply where a cooling type with a direct-expansion circuit is selected in the datasheet.
6.2.4 Requirements in the articles of this standard that address the chilled water coil and its control valve apply where a chilled water or dual cooling source type is selected in the datasheet.

6.3 Airflow Arrangement

6.3.1 The airflow arrangement shall be as indicated in the datasheet.
Airflow Arrangementselect
Downflow, discharging into a raised floor plenum and returning at the top of the unit
Upflow, discharging at the top of the unit into the room or a ducted plenum and returning at the front or bottom
Horizontal displacement, discharging at low level across the floor and returning at high level
In-row, standing in the rack row and discharging into the cold aisle
Ceiling-mounted, suspended above the equipment and discharging into the room or an overhead plenum
NOTE The downflow unit pressurizes a raised floor plenum, which carries the air anywhere a perforated tile is placed and is the arrangement every raised floor room was built around; it depends on the plenum being sealed and the tiles being placed where the load is, and it is as good as the floor under it. An upflow unit serves a room without a raised floor from the perimeter and depends on the room to carry the air to the racks, which the first rows get and the far rows do not, unless the discharge is ducted overhead to the cold aisles. A horizontal displacement unit floods the floor with cool air at low velocity and lets the racks draw it up, which suits a small room or a long narrow one. An in-row unit stands among the racks it cools, so the air path is a few feet, the capacity is placed where the density is, and the row can be contained, and it takes a rack position for every unit and brings water or refrigerant into the row. A ceiling-mounted unit takes no floor at all, puts every service point overhead, and returns the hottest air in the room, which is where it is. (6.3.2)
6.3.3 A downflow unit shall be furnished with a floor stand of the height indicated on the shop drawings and a turning plenum or discharge arrangement that delivers the air into the raised floor plenum without a free fall onto the slab.
6.3.4 A ceiling-mounted unit shall be furnished with hanging points rated for the operating weight and a drain pan under the full coil and connection extent.
6.3.5 An in-row unit shall be furnished in a cabinet whose footprint, height, and front-to-back depth match the equipment racks it stands among, with the air discharge and return on the rack faces.

6.4 Cooling Redundancy

6.4.1 The redundancy of the units serving each room shall be as indicated in the datasheet, with the number and capacity of units that satisfies it as indicated on the mechanical equipment schedule.
Cooling Redundancyselect
N, with no redundant unit
N+1, with one redundant unit per room or teamwork group
N+2, with two redundant units per room or teamwork group
2N, with two complete sets of units, each able to carry the room
NOTE Redundancy is bought in units, floor area, and the power to feed them, and it is the only thing that lets a unit be serviced while the room runs. One redundant unit covers a single failure or a single unit out for maintenance, and it leaves the room exposed during the hours one is down and a second fails. Two redundant units cover a failure during maintenance. A doubled installation survives the loss of an entire distribution path, which is the condition the highest availability tiers are written to, and it doubles everything, including the number of units that have to be rotated so that none of them sits idle. (6.4.2)
6.4.3 The redundant units shall be identical in capacity and configuration to the units they back up within the same room or teamwork group.
6.4.4 Where a cooling redundancy other than N is selected, the loss of any one unit shall leave the remaining units able to hold the room within the selected envelope at the scheduled load.

7 Capacity and Airflow Ratings

7.1 Net Sensible Cooling Capacity

7.1.1 The net sensible cooling capacity of each unit at the scheduled entering conditions shall be as indicated in the datasheet.
Net Sensible Cooling Capacityrange
Not less than
kW
3400
Per drawings — net sensible capacity as indicated on the mechanical equipment schedule (deferred by default)
7.1.2 Net sensible capacity shall be stated after deduction of the heat of the unit's own fans at the design operating point and, where the fans are located in the raised floor plenum, including the fans there.
7.1.3 The unit shall be selected on its net sensible capacity at the scheduled entering air condition, and the net total capacity and the sensible heat ratio at that selection shall be stated beside it.
NOTE A unit selected on total capacity meets the scheduled tonnage with a share of latent cooling the room does not have, which means a coil that is larger than it needs to be, a supply air temperature lower than the setpoint asks for, and a humidifier running to put back the moisture the coil removed. The rating standard reports net sensible capacity for exactly this reason, and it reports it net of fan heat because the fans of a unit that moves this much air are a measurable part of the load it is cooling. (7.1.4)

7.2 Airflow and External Static Pressure

7.2.1 The airflow of each unit at the design operating point shall be as indicated in the datasheet.
Airflow at the Design Operating Pointrange
cfm
50060000
Per drawings — airflow as indicated on the mechanical equipment schedule (deferred by default)
7.2.2 The external static pressure at the design airflow shall be as indicated in the datasheet.
External Static Pressure at the Design Airflowrange
in. w.g.
02
Per drawings — external static pressure as indicated on the mechanical equipment schedule (deferred by default)
7.2.3 Each unit shall deliver the scheduled airflow at the scheduled external static pressure with the scheduled filter installed and clean, at a fan speed not higher than the design fan speed.
NOTE A downflow unit does not discharge freely; it discharges into a plenum whose pressure is set by the depth of the floor, the open area of the tiles, and everything under the floor in the way. A unit selected at its free-discharge airflow delivers a fraction of it against a shallow or congested plenum, and the room develops hot spots at the far tiles while the unit reports that it is running. The plenum pressure the fans are selected against is the one the floor will actually present. (7.2.4)

7.3 Sound Power

7.3.1 The sound power level of each unit at the design operating point shall not exceed the value indicated in the datasheet in any octave band from 125 Hz through 8000 Hz.
Sound Power Level Limit per Octave Bandrange
Not more than
dB
60100
7.3.2 Where the datasheet does not state a sound power limit, the manufacturer shall state the sound power level of each unit in the submittal.
NOTE A computer room is rarely a quiet space, and the limit exists for the rooms that are: the network room beside an office, the telecommunications room in a hospital corridor, and the room an operator sits in. The fans dominate the unit's sound, and a unit that modulates its fans is quietest at the hours the load is lowest. (7.3.3)

8 Fans

8.1 Fan Type

8.1.1 The fan type shall be as indicated in the datasheet.
Fan Typeselect
Backward-curved plug fans driven by electronically commutated motors
Direct-drive centrifugal fans driven by induction motors on integral variable frequency drives
Belt-driven forward-curved centrifugal fans
NOTE A plug fan with an electronically commutated motor discharges straight into the plenum with no housing, accepts a speed command directly, and runs at a fraction of the input power of the alternatives at every reduced speed, which is why it is the fan nearly every unit in the market now carries and the fan the energy code's fan power limits were written around. A direct-drive centrifugal fan on an integral drive reaches the same speed range with an induction motor and a drive that service staff already know. A belt-driven fan is the construction of the installed base, and it is the selection that matches a replacement unit to its neighbors; it is bought with belts to tension and replace, belt dust in the airstream, and a fixed speed unless a drive is added. (8.1.2)
8.1.3 Fan motors shall comply with the fan motor efficiency provisions of Adopted Energy CodeAdopted Energy CodeParameterEach project supplies its own value.adopted-energy-code and with NEMA MG 1.
8.1.4 Fans shall be statically and dynamically balanced and mounted so that fan vibration is not transmitted to the cabinet.
8.1.5 Each fan and motor assembly shall be removable through the service access without disconnecting the coil, the refrigerant, or the condensate connections.
8.1.6 The fan input power at the design operating point shall not exceed the value indicated in the datasheet.
Fan Input Power at the Design Operating Pointrange
Not more than
W/cfm
0.10.150.20.250.30.350.40.50.751
8.1.7 Where the datasheet does not state a fan input power limit, the manufacturer shall state the fan input power at the design operating point for each unit in the action submittal.
8.1.8 The fan input power stated for each unit shall be the total input power to the motors and their integral electronics at the scheduled airflow and external static pressure, derived from testing in accordance with ANSI/AMCA 210.

8.2 Fan Location

8.2.1 Requirements in this article apply where a downflow airflow arrangement is selected in the datasheet.
8.2.2 The fan location shall be as indicated in the datasheet.
Downflow Fan Locationradio
○ Fans within the unit cabinet above the floor stand
○ Fans extended below the cabinet into the raised floor plenum
NOTE A fan that sits in the plenum discharges into it with no turning loss, pressurizes it more evenly, and draws less power for the same airflow; it also needs a floor deep enough to hold it, a cutout large enough to lower it through, and a plenum clear of piping and cable where it sits. A fan in the cabinet needs none of that and pays the turn into the floor at every hour. (8.2.3)
8.2.4 Where fans are extended into the raised floor plenum, the fan assembly shall be removable upward through the cabinet without lifting the unit.

8.3 Airflow Control

8.3.1 The airflow control method shall be as indicated in the datasheet.
Airflow Control Methodselect
Constant airflow set at startup
Modulated to hold the raised floor plenum static pressure setpoint
Modulated to hold the supply air temperature setpoint with the cooling source at its limit
Modulated to hold the differential pressure between the cold aisle and the hot aisle
Modulated to the remote equipment intake temperature sensors
NOTE Fan power varies roughly with the cube of airflow, so a unit that runs at seventy percent airflow for a room at seventy percent load draws about a third of its full-load fan power, and the control method is the choice of what the fans follow. Constant airflow is the behavior of the installed base and the one that needs no sensor outside the unit. Plenum pressure holds the supply the tiles see steady as units stage on and off, and it needs a pressure sensor under the floor and a plenum tight enough to hold a reading. Supply temperature lets the fans fall as the load falls once the coil has nothing left to give, which is the simplest sequence on a unit that controls supply air. Aisle differential pressure holds the containment at the point where neither aisle leaks into the other, and it needs a contained room. Remote intake sensors put the control point where the envelope is written, at the equipment, and they need sensors mounted on the racks and a network to bring the readings back. (8.3.2)
8.3.3 Where a modulated airflow control method is selected, the controller shall not reduce airflow below the minimum the manufacturer requires for coil performance, for the humidifier, or for the reheat where furnished.
8.3.4 Where a modulated airflow control method is selected, the sensors the fans follow shall be furnished with the unit or identified in the submittal as furnished under Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system.

9 Chilled Water Coil and Control Valve

9.1 Chilled Water Coil

9.1.1 Requirements in this section apply where a chilled water or dual cooling source type is selected in the datasheet.
9.1.2 The chilled water coil shall be constructed of seamless copper tube to ASTM B75 mechanically expanded into aluminum plate fins to form a continuous metal-to-metal bond over the full finned length.
9.1.3 The row count and fin spacing of the coil shall be the manufacturer's selection to deliver the scheduled net sensible capacity at the scheduled entering air condition, the scheduled entering water temperature, and the scheduled airflow, and shall be stated in the capacity selection data.
NOTE Row count is where the plant's water temperature meets the room. A plant run warm for efficiency and economizer hours needs more coil surface to reach the same supply air temperature, and a unit selected at a cold plant temperature falls short of its capacity the day the plant is raised; the count follows the scheduled water temperature rather than a catalog reference. (9.1.4)
9.1.5 The chilled water entering temperature shall be as indicated in the datasheet.
Chilled Water Entering Temperaturerange
°F
4075
Per drawings — chilled water temperatures as indicated on the mechanical equipment schedule (deferred by default)
9.1.6 The chilled water leaving temperature and the flow for each coil shall be as indicated on the mechanical equipment schedule.
9.1.7 The coil working pressure rating shall be as indicated in the datasheet.
Chilled Water Coil Working Pressure Ratingrange
Not less than
psig
150200250300400
9.1.8 Coils shall be leak tested at the factory at not less than 1.5 times the specified working pressure rating with air under water or by an equivalent method, and the test shall be recorded in the factory test report.
9.1.9 Coils shall be furnished with a manual air vent at the high point and a drain connection at the low point, each accessible with the unit installed.
9.1.10 Coil connections shall extend beyond the cabinet or terminate at a connection within the cabinet reachable through the service access, and the connection type, size, and location shall be stated on the shop drawings.

9.2 Chilled Water Control Valve

9.2.1 Each chilled water coil shall be furnished with a factory-installed control valve of the type indicated in the datasheet.
Chilled Water Control Valve Typeselect
Two-way modulating valve
Pressure-independent control valve
Three-way modulating valve
NOTE A two-way valve throttles the coil flow and returns the water the coil did not use to the plant as flow it no longer has to pump, which is the valve of a variable-flow plant, and it depends on a plant that can hold its differential pressure as valves close. A pressure-independent valve adds a regulator that holds the coil flow at its setting whatever the loop pressure does, so the coil gets its scheduled flow with no balancing valve and the plant sees a steady differential, at a higher cost per valve and a strainer the regulator needs. A three-way valve bypasses the coil rather than throttling the loop, which holds the loop flow constant and is the valve of a constant-flow plant, and it returns water the coil did not cool, which lowers the plant's return temperature and its efficiency. (9.2.2)
9.2.3 The control valve shall be sized for the scheduled coil flow at the differential pressure available at the unit connection, and the valve size and its pressure drop at scheduled flow shall be stated in the submittal.
9.2.4 The control valve actuator shall be modulating, shall accept the control signal of the unit controller, and shall drive to the position the sequence of operation designates on loss of signal.
9.2.5 Where a pressure-independent control valve is selected, the valve shall include measurement ports at which the flow can be verified.

10 Direct-Expansion Refrigeration Circuit

10.1 Compressors

10.1.1 Requirements in this section apply where a cooling type with a direct-expansion circuit is selected in the datasheet.
10.1.2 The compressor type shall be as indicated in the datasheet.
Compressor Typeselect
Fixed-capacity hermetic scroll
Tandem or multiple fixed-capacity hermetic scroll compressors on one circuit
Digital scroll with unloading modulation
Variable-speed hermetic scroll on an integral inverter drive
NOTE A computer room unit runs at every hour of the year against a load that is rarely the design load, and the compressor decides how the unit behaves at every other load. A fixed-capacity scroll cycles, which means the supply temperature swings and the compressor starts the number of times a year a comfort compressor starts in a decade. Tandem compressors give a part-load step and a half-capacity fallback when one fails. A digital scroll modulates by unloading, which holds a steady supply temperature across its range at a modest premium and loses efficiency at the bottom of the range, where it is unloading most of the time. A variable-speed scroll follows the load with its speed, holds the supply temperature with the least swing, and draws the least power at part load, which is where the unit spends its life, at the cost of a drive that has to be cooled and whose harmonics the branch circuit tolerates. (10.1.3)
10.1.4 Each compressor shall be mounted on vibration isolators within the cabinet, with suction and discharge connections arranged so that compressor vibration is not transmitted into the coil tubing.
10.1.5 Each compressor shall be furnished with a crankcase heater, a high-pressure cutout, a low-pressure cutout or loss-of-charge protection, and a motor overload, each of which shall stop the compressor independently of the unit controller.
10.1.6 The compressor shall be furnished with suction and discharge service valves and with service access ports on the high and low sides of each circuit.
10.1.7 The expansion device on each circuit shall be an electronic expansion valve where a digital scroll or variable-speed compressor is selected, and shall be a thermostatic or electronic expansion valve where a fixed-capacity compressor is selected.
10.1.8 Each circuit shall be furnished with a liquid line filter-drier, a sight glass with moisture indicator, and a liquid line solenoid valve where the manufacturer's design requires one for pump-down.

10.2 Refrigerant and Safety Group

10.2.1 The refrigerant shall be as indicated in the datasheet.
Refrigerant Designation (ASHRAE 34)select
R-454B
R-32
R-410A
Manufacturer's standard (by default)
10.2.2 Where the datasheet leaves the refrigerant to the manufacturer, the manufacturer shall state in the submittal the refrigerant the unit is charged with and its safety group.
10.2.3 The refrigerant shall be one that 40 CFR Part 84 permits in equipment of the unit's class on the unit's date of manufacture.
10.2.4 Where a unit is furnished as a replacement that retains an existing remote condenser or existing refrigerant piping, the refrigerant selected in the datasheet shall be compatible with the retained components, and the Contractor shall confirm the refrigerant present in the retained circuit before any new component is connected to it.
10.2.5 The refrigerant safety group shall be as indicated in the datasheet.
Refrigerant Safety Group (ASHRAE 34)select
A1
A2L
Derived — the safety classification ASHRAE 34 publishes for the refrigerant the unit is charged with (by default)
NOTE Under the technology transition rule at 40 CFR Part 84, computer room units manufactured after the compliance date for their class are limited to refrigerants below a stated global warming potential, and the refrigerants that meet that limit at the pressures this equipment runs at are classified A2L. The refrigerant is therefore a property of the product line rather than a specification choice for new equipment, and the datasheet asserts one only where a project has a reason to, such as matching a retained condenser. The safety group follows from the refrigerant and is the switch that turns the detection, mitigation, marking, and training requirements of this standard on or off. (10.2.6)

10.3 Refrigerant Detection and Mitigation

10.3.1 The refrigerant detection provision shall be as indicated in the datasheet.
Refrigerant Detection Systemradio
○ Factory-installed refrigerant detection system with mitigation
○ No refrigerant detection system
Derived — the refrigerant safety group and the charge per circuit, compared against the releasable charge limit UL 60335-2-40 establishes for the unit and the room it serves (by default)
10.3.2 Where a refrigerant detection system is furnished, the sensors, their locations, and the mitigation sequence shall be as covered by the unit listing, and the Contractor shall not relocate a sensor or alter the sequence in the field.
10.3.3 On detection, the mitigation sequence shall run the unit fans to dilute the released refrigerant, shall de-energize the ignition sources the listing identifies, and shall continue until the measured concentration has fallen below the reset threshold.
10.3.4 Where a refrigerant detection system is furnished, its alarm shall be exposed to the monitoring system as a discrete point regardless of the control points selected in the datasheet.
10.3.5 Detection sensors shall be installed with the date of installation recorded on the device, and the end of the published service life of each sensor shall be recorded in the closeout documents.
10.3.6 Where a unit with a direct-expansion circuit serves a room whose charge limit under ANSI/ASHRAE 15 is lower than the circuit charge, the Engineer of Record shall determine the ventilation, detection, or charge reduction that brings the room into compliance before the unit is released for fabrication.
NOTE A refrigerant in the A2L group burns only within a narrow concentration band and only with a strong ignition source, so the listing manages the hazard by keeping the concentration in any space below a fraction of the lower flammability limit. A computer room is often small and tightly closed, with a large charge in the unit standing in it, which is exactly the case the charge limit was written for; the mitigation runs the fans the unit already has, through a room that is already a mixing volume. Whether a given unit needs it is a calculation on the charge and the room, which is why it is derived rather than chosen. (10.3.7)

11 Heat Rejection Equipment

11.1 Remote Air-Cooled Condenser

11.1.1 Requirements in this article apply where an air-cooled direct-expansion cooling type is selected in the datasheet.
11.1.2 Each unit shall be furnished with a remote air-cooled condenser matched to it by the manufacturer, selected to reject the full heat of the matched unit at the design condensing temperature with the entering air at the site maximum stated in the service conditions of this standard.
11.1.3 Condenser fans shall be direct-drive propeller fans driven by electronically commutated motors or by induction motors on a speed control, modulated by the head pressure control to hold the condensing pressure setpoint across the full outdoor temperature range.
11.1.4 The condenser coil corrosion protection shall be as indicated in the datasheet.
Condenser Coil Corrosion Protectionselect
Uncoated aluminum fin on copper tube
Aluminum fin on copper tube with an electrodeposited epoxy coating
Aluminum fin on copper tube with an applied phenolic coating
Microchannel aluminum coil with an electrodeposited coating
Copper fin on copper tube
11.1.5 Where a coil coating is selected, the coating shall be applied after fin and tube assembly so that the tube-to-fin interface is coated, and the manufacturer shall state in the submittal the salt spray exposure to ASTM B117 the coated coil has been tested to.
NOTE Aluminum fin on copper tube is a galvanic pair that stays benign while the fin surface is dry and becomes active once a persistent electrolyte film forms 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 heat rejection falls while discharge pressure rises. An electrodeposited coating is applied by immersing the finished coil and curing a uniform film onto every surface, so it protects the fin-to-tube joint where a sprayed coating cannot reach, at a small thermal penalty the submittal reports; a copper fin removes the couple entirely at the highest cost and weight. The condition that selects any of them is the atmosphere the condenser stands in. (11.1.6)
11.1.7 The condenser shall be furnished with a weatherproof electrical enclosure, a factory-wired fan control panel, and a disconnecting means or provisions for one as Adopted Electrical CodeAdopted Electrical CodeParameterEach project supplies its own value.adopted-electrical-code requires.
11.1.8 Where the refrigerant piping between the unit and the condenser exceeds the length or lift the manufacturer publishes for the matched pair, the manufacturer shall state in the submittal the capacity correction, the additional charge, and the oil management provisions that apply.

11.2 Water-Cooled Condenser

11.2.1 Requirements in this article apply where a water-cooled direct-expansion cooling type is selected in the datasheet.
11.2.2 The water-cooled condenser within the unit shall be of the construction indicated in the datasheet.
Water-Cooled Condenser Constructionselect
Brazed plate heat exchanger
Coaxial tube-in-tube
Shell-and-tube with cleanable tubes
NOTE A brazed plate condenser is the most compact and the most efficient for its size, and it cannot be opened, so it is cleaned chemically and it fouls fastest on a loop whose water is not kept clean. A coaxial condenser is a tube inside a tube, tolerant of fouling and cleaned chemically. A shell-and-tube condenser can be rodded, which is the construction for a loop fed by a tower whose water carries whatever the air brought in. The condition that selects among them is the water: a closed, treated loop lets the compact exchangers run for years, and an open tower loop is the case for tubes that can be cleaned. (11.2.3)
11.2.4 The condenser shall be rated for the condenser water working pressure of the loop and for the scheduled entering water temperature, and the water-side pressure drop at scheduled flow shall be stated in the submittal.
11.2.5 The condenser water entering temperature shall be as indicated in the datasheet.
Condenser Water Entering Temperaturerange
°F
45110
Per drawings — condenser water temperatures as indicated on the mechanical equipment schedule (deferred by default)
11.2.6 Each water-cooled condenser shall be furnished with a head pressure control valve that holds the condensing pressure setpoint by regulating condenser water flow, arranged to fail to the position the sequence of operation designates.
11.2.7 The cooling tower that serves the condenser water loop, and the loop's pumps and treatment, are furnished under Cooling TowersCooling TowersResolves to the current adopted revision.sync/cooling-towers, HVAC PumpsHVAC PumpsResolves to the current adopted revision.sync/hvac-pumps, and HVAC Water TreatmentHVAC Water TreatmentResolves to the current adopted revision.sync/hvac-water-treatment.

11.3 Glycol Drycooler and Pump Package

11.3.1 Requirements in this article apply where a glycol-cooled direct-expansion cooling type is selected in the datasheet, or where a fluid economizer coil served by a drycooler is selected.
11.3.2 Each unit or group of units shall be furnished with a remote drycooler and a glycol pump package matched to it by the manufacturer, selected to reject the full heat of the matched units at the design entering fluid temperature with the entering air at the site maximum stated in the service conditions of this standard.
11.3.3 Drycooler fans shall be direct-drive propeller fans driven by electronically commutated motors or by induction motors on a speed control, modulated to hold the fluid temperature setpoint across the full outdoor temperature range.
11.3.4 The glycol concentration shall be as indicated in the datasheet.
Glycol Concentration by Volumerange
Not less than
%
060
Derived — the freeze protection the drycooler loop needs at Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum, per the glycol manufacturer's published freeze point table, plus the burst protection margin the drycooler manufacturer publishes (by default)
11.3.5 The glycol shall be an inhibited ethylene glycol or inhibited propylene glycol solution as HVAC Water TreatmentHVAC Water TreatmentResolves to the current adopted revision.sync/hvac-water-treatment establishes for the project, and the capacity and pressure drop corrections for the solution at the selected concentration shall appear in the capacity selection data.
11.3.6 The glycol pump arrangement shall be as indicated in the datasheet.
Glycol Pump Arrangementradio
○ Single pump
○ Duplex pumps with automatic changeover on pump failure
NOTE The drycooler loop is the heat rejection path for every unit on it, and a single pump is a single point of failure that takes every one of them down together. A duplex package costs a second pump, a changeover controller, and the space for both, and it is the arrangement a room with cooling redundancy depends on to make that redundancy real. (11.3.7)
11.3.8 The pump package shall be furnished with isolation valves, a strainer, a pressure gauge on each side of each pump, an expansion tank, an air separator, and a fill connection, factory-piped and wired in a weatherproof enclosure where the package stands outdoors.
11.3.9 The initial glycol charge, the flushing of the loop before it, and the field verification of the concentration are performed under Hydronic Cleaning And FlushingHydronic System Cleaning and FlushingResolves to the current adopted revision.sync/hydronic-cleaning-and-flushing.
11.3.10 The drycooler coil corrosion protection shall be the same as the condenser coil corrosion protection selected in the datasheet.

12 Economizer

12.1 Economizer Type

12.1.1 The economizer provision shall be as indicated in the datasheet.
Economizer Typeselect
None
Fluid economizer coil in the unit served by the drycooler or condenser water loop
Pumped refrigerant economizer bypassing the compressor at low outdoor temperature
Integrated air-side economizer section admitting filtered outdoor air
12.1.2 Where Adopted Energy CodeAdopted Energy CodeParameterEach project supplies its own value.adopted-energy-code requires an economizer for a computer room of the project's load in Climate ZoneClimate ZoneParameterEach project supplies its own value.climate-zone, the economizer selected in the datasheet shall satisfy that requirement, or the exception relied on shall be identified in the energy compliance documentation.
NOTE A computer room's load is there on the coldest night of the year, which is the hour a comfort system has none, so the hours an economizer runs in this service are the hours the compressor or the plant would otherwise run at full load in the cold. A fluid economizer coil puts the drycooler's or the tower's cold fluid through a second coil ahead of the cooling coil, which carries the whole load when the fluid is cold enough and part of it for the months in between, and it needs a glycol or condenser water loop and a second coil the air has to cross at every hour. A pumped refrigerant economizer stops the compressor and pumps liquid refrigerant through the same coil when the condenser is cold enough to condense without it, which needs no second coil or loop and works only on an air-cooled unit with a matched condenser. An air-side economizer brings the outside in, which is the largest saving and the only one that brings outdoor humidity, particulates, and gaseous contaminants to the equipment intakes with it, so it carries filtration, humidity limits, and a room that tolerates them. For a chilled water unit the economizer is at the plant, under the chiller standard, and the unit's part is a coil selected for the warmer water the plant then supplies. (12.1.3)
12.1.4 Where an economizer is furnished, the unit controller shall sequence economizer, partial economizer with mechanical cooling, and full mechanical cooling without a step in the supply air temperature at each transition.
12.1.5 Where a fluid economizer coil is furnished, it shall be located upstream of the cooling coil in the direction of airflow, and its air-side pressure drop shall be included in the fan selection.
12.1.6 Where an air-side economizer section is furnished, it shall include filtration of the outdoor air to not less than the filter efficiency selected in the datasheet, a humidity high limit that closes the outdoor air damper when the outdoor dew point exceeds the room's envelope, and dampers that drive closed on loss of power.
12.1.7 The hours of economizer operation claimed for each unit shall be stated in the energy compliance documentation with the changeover conditions on which they are based.

13 Humidity Control

13.1 Humidifier

13.1.1 The humidifier furnished within the unit shall be as indicated in the datasheet.
Humidifier Typeselect
None
Infrared steam humidifier
Electrode steam humidifier
Ultrasonic humidifier
Wetted-media evaporative humidifier
13.1.3 Where a humidifier is furnished, its capacity shall be as indicated in the datasheet.
Humidifier Capacityrange
Not less than
lb/h
160
Per drawings — humidification capacity as indicated on the mechanical equipment schedule (deferred by default)
13.1.4 Where a humidifier is furnished, the humidifier supply water quality shall meet the manufacturer's requirement for the selected type, and that requirement shall be stated in the submittal for coordination with the water treatment furnished under HVAC Water TreatmentHVAC Water TreatmentResolves to the current adopted revision.sync/hvac-water-treatment.
13.1.5 Where a humidifier is furnished, it shall be furnished with an automatic fill valve, a drain or flush cycle, a high-water cutout, and a drain connection extended beyond the cabinet for a field connection.

13.2 Dehumidification and Reheat

13.2.1 The dehumidification mode shall be as indicated in the datasheet.
Dehumidification Moderadio
○ Not furnished, with the unit controlling temperature only
○ Furnished, with the cooling coil driven below the sensible setpoint on a humidity call
NOTE Dehumidification on a computer room unit is the coil run colder than the room's temperature asks for, which overcools the air it dries, so it is paired with reheat or with a reduced airflow that lets the coil dry more and cool less; a room that never reaches the upper humidity limit never calls for it, and a room with an air-side economizer or a door to a humid corridor does. (13.2.2)
13.2.3 The reheat source shall be as indicated in the datasheet.
Reheat Sourceselect
None
Electric resistance reheat
Hot gas reheat from the direct-expansion circuit
Hot water reheat coil
NOTE Electric reheat is available on any unit and adds the full reheat load to the room's electrical service and to its cooling load. Hot gas reheat recovers the heat the condenser would otherwise reject, costs nothing to run, and is available only on a unit with a direct-expansion circuit. A hot water coil runs on heat the building already has, which is the arrangement where a heating plant serves the building and the one that brings heating water into the room. (13.2.4)
13.2.5 Where a reheat source other than none is selected, the reheat shall be staged or modulated by the unit controller and shall be energized only while the unit is in dehumidification mode.
13.2.6 Where electric resistance reheat is selected, the elements shall be furnished with a primary automatic-reset thermal cutout, a secondary manual-reset thermal cutout, and an airflow proving interlock wired in series with the reheat control circuit independently of the unit controller.
13.2.7 Simultaneous heating and cooling for humidity control shall comply with the limits Adopted Energy CodeAdopted Energy CodeParameterEach project supplies its own value.adopted-energy-code places on it for the computer room.

13.3 Humidity Control Basis

13.3.1 Where a humidifier or a dehumidification mode is furnished, the controlled humidity variable shall be as indicated in the datasheet.
Controlled Humidity Variableradio
○ Dew point temperature
○ Relative humidity at the control sensor
NOTE Relative humidity at a sensor is a function of the temperature at that sensor, so two units in one room reading the same air at different temperatures read different humidities and one humidifies while its neighbor dehumidifies. Dew point is the same number everywhere in the room, which is why the thermal guidelines write the humidity envelope in it and why a room of units controlled on it does not fight. Relative humidity remains the variable on the installed base and on a single unit in a single room, where there is nothing to fight with. (13.3.2)
13.3.3 Where more than one unit serves a room, the humidity setpoint and the sensed value the units act on shall be common across the teamwork group so that no unit humidifies while another dehumidifies.

14 Filtration

14.1 Filter Efficiency and Access

14.1.1 Each unit shall be furnished with filters located so that all air entering the coil passes through them, rated in accordance with ANSI/ASHRAE 52.2 at not less than the efficiency indicated in the datasheet.
Filter Efficiencyrange
Not less than
MERV
46810111314
14.1.2 The filter depth shall be as indicated in the datasheet.
Filter Depthrange
in.
124
14.1.3 Each unit shall be furnished with a filter differential pressure switch or transmitter that reports a change-filter condition to the unit controller.
14.1.4 Filters shall be of a standard nominal size available from more than one filter manufacturer, replaceable from the service face of the unit without tools other than those needed to open the access panel and without stopping the fans of an adjacent unit.
NOTE A computer room is a closed room with a sealed floor and no outdoor air, and its particulate load is what the staff and the cardboard bring in; the filter protects the coil and the equipment intakes rather than meeting a ventilation standard. The efficiency the room needs is set by the equipment makers' cleanliness guidance, and the pressure drop of a higher efficiency is paid at every hour by fans that never stop, which is why the limit is set at the efficiency the room actually needs. A deeper filter holds more dust at a lower resistance and is changed less often, which in a room that cannot be shut down is the argument for it. (14.1.6)

15 Cabinet, Drain Pan, and Condensate

15.1 Cabinet Construction

15.1.1 The cabinet shall be constructed of galvanized steel sheet to ASTM A653 on a welded or bolted structural frame, with removable or hinged panels on the service faces and a finish on the exposed faces of a baked powder or enamel coating.
15.1.2 Cabinet panels shall be insulated with a fiber or foam insulation faced or sealed against erosion into the airstream and shall have a flame spread index and smoke developed index meeting NFPA 90A.
15.1.3 Service access to the fans, coil, filters, compressors, humidifier, control valve, and controls shall be from the front of the unit, or from the front and one side, so that the unit can stand against a wall and against an adjacent unit on the other side.
15.1.4 The cabinet shall be arranged so that no routine service item requires the unit to be moved, lifted, or disconnected from its piping.
NOTE A computer room unit stands shoulder to shoulder with its neighbors on a wall, and any service point on its sides or back is a service point no one can reach. Front access is the construction the whole market builds to, and the exception that needs side access needs the floor space to give it. (15.1.5)

15.2 Drain Pan and Condensate

15.2.1 Each unit with a cooling coil shall be furnished with a primary drain pan of Type 304 stainless steel to ASTM A240 beneath the full length and width of the coil and beneath the coil headers, return bends, and the humidifier where furnished.
15.2.2 The drain pan shall be sloped in two planes to its drain connection so that it holds no standing water when the fans are off, and shall be furnished with a drain connection not smaller than 3/4 in. at its low point extended beyond the cabinet for a field connection.
15.2.3 The condensate removal method shall be as indicated in the datasheet.
Condensate Removal Methodradio
○ Gravity drain from the pan connection
○ Condensate pump furnished within the unit with a high-level cutout
NOTE A gravity drain has nothing to fail and needs a drain below the pan within reach of a slope, which a raised floor usually gives and a slab floor often does not. A condensate pump lifts the water to a drain anywhere, and it is a pump with a float in a pan of water that runs for the life of the unit, so its cutout is what keeps a stuck float from becoming a flooded floor. (15.2.4)
15.2.5 Where a condensate pump is furnished, its high-level cutout shall stop the cooling and the humidifier and shall report to the unit controller.
15.2.6 Condensate and humidifier drain piping beyond the unit connection is furnished under Condensate Drainage PipingHVAC Condensate Drainage PipingResolves to the current adopted revision.sync/condensate-drainage-piping.

16 Leak Detection

16.1 Leak Detection at the Unit

16.1.1 Each unit shall be furnished with the leak detection provisions indicated in the datasheet.
Leak Detection Provisionscheckbox
☑ Spot leak detector under each unit in the pan or floor area beneath its connections
☐ Leak detection cable around each unit and along its piping route under the raised floor
☐ Automatic closure of the chilled water, condenser water, or glycol isolation valves at the unit on detection
☑ Leak detection alarm exposed to the monitoring system as a discrete point
NOTE A unit carrying water or glycol stands over the power and data cabling that runs under the floor, and the first sign of a leaking coil, a sweating valve, or a cracked humidifier drain is water in the plenum. A spot detector under the unit finds the leak at its source; a cable along the piping finds the one that runs along the pipe to somewhere else; and an automatic valve stops the water while the alarm is being answered, at the cost of a unit that shuts down on a wet sensor. (16.1.2)
16.1.3 Leak detectors shall be furnished with the unit or identified in the submittal as furnished under Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system, and shall be located as shown on the shop drawings.
16.1.4 Where automatic valve closure is selected, the isolation valves shall be motorized, shall be furnished with the unit or identified in the submittal as furnished under HVAC Piping ValvesGeneral-Duty Valves for HVAC PipingResolves to the current adopted revision.sync/hvac-piping-valves, and shall close only on a confirmed detection at the unit they isolate.
16.1.5 Where automatic valve closure is selected on a unit with cooling redundancy, the closure of one unit's valves shall not isolate any other unit.

17 Controls

17.1 Unit Controller and Sensing Point

17.1.1 Each unit shall be furnished with a factory-installed microprocessor controller with a local display that controls the fans, the cooling source, the economizer, the humidifier, the dehumidification mode, and the reheat, carries the manufacturer's compressor protection logic, and holds its setpoints and alarm history through a loss of power.
17.1.2 The controller shall carry the manufacturer's compressor protection logic, including minimum run and off times and anti-short-cycle timing, regardless of which party controls the setpoints.
17.1.3 The temperature control sensing point shall be as indicated in the datasheet.
Temperature Control Sensing Pointselect
Supply air at the unit discharge
Return air at the unit inlet
Remote sensors at the equipment intakes
NOTE Return air control holds the temperature of the air leaving the room and lets the supply drift with the load, so the air the equipment breathes is a number the controller never reads; it is the control of the installed base and of a unit that has no other sensor. Supply air control holds the temperature the unit delivers, which is the quantity the envelope is written against once the rise across the room is known, and it lets the supply temperature be raised for efficiency without guessing. Remote intake sensors control the quantity the envelope actually names, at the equipment, which is the most direct control and the one that needs sensors on the racks and a network to carry them. (17.1.4)
17.1.5 The controller shall be furnished with the sensors its control sensing point requires, and where remote intake sensors are selected, with not fewer than the number of sensors per unit the manufacturer requires, located as shown on the shop drawings.
17.1.6 The controller shall alarm on high and low supply or return air temperature, high and low humidity, loss of airflow, filter change, high and low refrigerant pressure, compressor overload, high water level in the pan or the humidifier, leak detection, and loss of communication with the teamwork group where furnished.
17.1.7 The controller shall restart the unit automatically, in the sequence the manufacturer designates, after a loss and restoration of power.

17.2 Unit-to-Unit Teamwork

17.2.1 The teamwork arrangement of the units serving each room shall be as indicated in the datasheet.
Unit-to-Unit Teamworkradio
○ Stand-alone, with each unit controlling to its own sensors
○ Teamwork group, with the units in a room networked and controlled as a group
NOTE A room of stand-alone units is a room of controllers that each see their own corner of it, and the result is one unit cooling while its neighbor's fans idle, one humidifying while another dehumidifies, and a redundant unit that never runs. A teamwork group shares the sensors, the setpoints, the staging, and the runtime, brings the standby unit online when one fails, and rotates the lead so that every unit is proven; it needs a network between the units and a controller that is the group's single point of configuration. A single unit in a single room has nothing to team with. (17.2.2)
17.2.3 Where a teamwork group is selected, the group shall stage units, share airflow and cooling, coordinate humidity control on the common basis stated in the humidity control section of this standard, rotate the lead unit at the interval the sequence of operation states, and start a standby unit on the failure or alarm of any running unit.
17.2.4 Where a teamwork group is selected, the standby units shall be rotated into service rather than held idle, so that every unit in the group accumulates runtime and is proven before it is needed.
17.2.5 Where a teamwork group is selected, the loss of the group network shall leave each unit operating stand-alone on its own sensors at its last setpoints.

17.3 Monitoring System Interface

17.3.1 The communication interface to the monitoring system shall be as indicated in the datasheet.
Monitoring System Interfaceselect
BACnet/IP
BACnet MS/TP
Modbus TCP
Modbus RTU
SNMP
Hardwired point-to-point interface with no network connection
NOTE The interface follows the system that will watch the unit. A building automation system speaks BACnet, over the building's Ethernet where the unit can reach it and over a twisted-pair bus where it cannot. Modbus is the interface of a power monitoring or industrial system and of many unit controllers natively, in the same two forms. SNMP is the protocol of the network management and data center infrastructure management systems the IT staff already run, and a room watched by the IT staff rather than the facilities staff is the case for it. A hardwired interface carries a handful of contacts and no values, and it is the interface of a unit in a room with no network to join. (17.3.2)
17.3.3 The interface shall conform to Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system where the unit is integrated with the building automation system.
17.3.4 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.
17.3.5 The points exposed to the monitoring system shall include those indicated in the datasheet.
Control Points Exposed to the Monitoring Systemcheckbox
☑ Supply air temperature
☑ Return air temperature and humidity
☐ Remote intake temperatures where furnished
☑ Fan command, speed, and status
☑ Cooling capacity command and status, by compressor or control valve position
☐ Economizer status and mode
☑ Humidifier and dehumidification command and status
☐ Reheat command and status
☑ Filter change alarm
☑ Leak detection alarm
☐ Refrigerant detection alarm
☐ Water level and condensate pump alarm
☐ Teamwork group status and lead unit
☑ General alarm and alarm history
☑ Temperature and humidity setpoints
☑ Unit enable and disable command
17.3.6 Field control connections shall terminate on a labeled terminal block in a compartment accessible without opening a section that is pressurized during operation, and the terminal designations shall match the submitted wiring diagram and point list.

17.4 Fire Protection Interlock

17.4.1 Each unit shall be furnished with a dry contact input that stops the fans and the cooling source on a signal from the fire alarm system, arranged as Fire Alarm SystemsFire Alarm SystemsResolves to the current adopted revision.sync/fire-alarm-systems and NFPA 75 require for the room.
17.4.2 Where the room is protected by a clean agent system, the unit shutdown shall be initiated on the agent release signal before discharge, so that the unit does not dilute the agent concentration, as coordinated with Clean Agent Fire SuppressionClean Agent Fire Suppression SystemsResolves to the current adopted revision.sync/clean-agent-fire-suppression.
17.4.3 Where NFPA 70 Article 645 is applied to the room, the unit shall be stopped by the disconnecting means that article requires at the room exits, and the remote stop shall be hardwired independently of the unit controller and the monitoring system.
17.4.4 Restart after a fire alarm shutdown shall require a manual reset at the unit or at the location the sequence of operation designates.
NOTE A clean agent holds its concentration only in a room whose air is not being churned and exhausted, and a unit that keeps running during discharge pushes agent out through every leak in the room and draws air in to replace it. The unit stops before the agent goes, and it stays stopped until someone has looked. (17.4.5)

18 Electrical Provisions

18.1 Power Connection

18.1.1 The unit supply voltage shall be as indicated in the datasheet.
Unit Supply Voltagerange
V
208230380400415460480575600
Per drawings — electrical drawings and panel schedules (deferred by default)
18.1.2 The unit supply phase shall be as indicated in the datasheet.
Unit Supply Phaseradio
○ Single phase, 1Φ
○ Three phase, 3Φ
Per drawings — electrical drawings and panel schedules (deferred by default)
18.1.3 The electrical characteristics shown on the mechanical equipment schedule and those shown on the electrical documents shall be reconciled before any unit is released for fabrication, and any discrepancy shall be resolved by the Engineer of Record.
18.1.4 Each unit shall be furnished with a single-point power connection for the unit, the humidifier, and the reheat, unless the datasheet or the electrical drawings designate a separate connection for the reheat or the humidifier.
18.1.5 The unit nameplate shall state the minimum circuit ampacity and the maximum overcurrent protective device rating for the unit as furnished, including the humidifier and the reheat where furnished.
18.1.6 The branch circuit, its overcurrent protection, and the disconnecting means for each unit and each remote condenser or drycooler shall comply with Adopted Electrical CodeAdopted Electrical CodeParameterEach project supplies its own value.adopted-electrical-code.
18.1.7 Each unit shall be furnished with a factory-mounted disconnecting means, or with provisions for one as indicated on the electrical drawings, within sight of the unit.

18.2 Dual Power Input

18.2.1 The power input arrangement shall be as indicated in the datasheet.
Power Input Arrangementradio
○ Single power input
○ Dual power inputs with an automatic transfer switch within the unit
NOTE A room whose cooling has to survive the loss of a distribution path feeds each unit from two paths, and the question is where the transfer happens. A transfer switch in the unit lets one unit ride through the loss of either feeder, which is the arrangement that keeps every unit running on a 2N power system; it costs a switch in every unit and a second feeder to each one. A single input depends on the redundancy being carried by alternate units on alternate feeders, which is the arrangement a 2N cooling system can afford and an N+1 system cannot. (18.2.2)
18.2.3 Where dual power inputs are selected, the transfer switch shall transfer on loss of the preferred source without stopping the fans for longer than the controller's ride-through, and shall report the active source and a transfer alarm to the monitoring system.
18.2.4 The assignment of each unit to its normal and alternate power sources shall be as indicated on the electrical drawings.

19 Factory Testing

19.1 Production Run Test

19.1.1 Every unit shall be run-tested at the factory before shipment, and the factory tests performed on each unit shall include those indicated in the datasheet.
Factory Tests Requiredcheckbox
☑ Refrigerant circuit evacuation, charge, and leak test
☑ Chilled water coil leak test at the test pressure
☑ Compressor operation on each stage or across the modulation range
☑ Refrigerant operating pressures and temperatures recorded on each circuit
☑ Fan operation at the design speed with motor current recorded
☑ Humidifier fill, steam or mist production, and drain cycle
☐ Reheat energized on each stage
☑ Control valve stroke and fail position
☑ Safety device trip verification
☐ Refrigerant detection system function test
☐ Leak detector function test
☑ Controls point-to-point verification
19.1.2 A unit that fails any required test shall be corrected and retested at the manufacturer's expense, and no unit shall be shipped until every required test has been passed and the results recorded on a report that identifies the unit by serial number.
19.1.3 The test record shall mark as not applicable the refrigerant items on a chilled water unit and the chilled water items on a direct-expansion unit, rather than omitting them.

19.2 Test Witnessing

19.2.1 Factory test witnessing shall be as indicated in the datasheet.
Factory Test Witnessingradio
● 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
NOTE A witnessed test buys the Owner's own eyes on the unit before it ships, which on a unit bound for a room that cannot be shut down is the last look anyone gets before the load is on it; it costs the travel, the schedule, and a test that waits for the witness. A remote witness buys most of that at the cost of the travel only, and an unwitnessed certified test is what the market furnishes by default. (19.2.2)
19.2.3 Where witnessed testing is selected, the manufacturer shall give not less than ten business days notice of test readiness, shall submit the test procedure for review before the test is scheduled, and shall bear the cost of the witness attending each retest where the unit fails.

20 Delivery, Storage, and Handling

20.1 Units shall be shipped fully assembled, charged where direct-expansion, with the coil connections capped, the openings covered, and the fans and compressors restrained for transit.
20.2 Units shall be stored indoors on a level surface in their protective packaging, with the openings sealed, in a space not subject to freezing, roof leaks, or construction dust, until they are set.
20.3 Chilled water units stored where the temperature can fall below 35 °F shall have their coils drained, blown out, and tagged as drained, and the tag shall be removed only when the coil has been refilled and vented at startup.
20.4 Direct-expansion units stored for more than 30 days before setting shall have the crankcase heaters energized where the manufacturer requires it.
20.5 Remote condensers and drycoolers shall be stored upright, with their coils protected from impact and their electrical enclosures closed.
20.6 Units damaged in transit, in storage, or in handling shall be repaired or replaced as the Engineer of Record directs in writing, and a unit whose refrigerant circuit has been opened by damage shall be evacuated and recharged at the factory or by the manufacturer's representative.

21 Installation

21.1 Service Clearances and Coordination

21.1.1 Unit locations, tags, and orientations are as indicated on the mechanical plans.
21.1.2 The service clearances shown on the reviewed shop drawings shall be maintained clear of racks, cable tray, piping, conduit, and other equipment after installation.
21.1.3 The filter withdrawal path, the fan removal path, the coil and compressor access, and the humidifier access shall remain unobstructed for the life of the installation.
21.1.4 Where a service clearance conflicts with the rack layout or 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.

21.2 Floor Stand and Plenum Interface

21.2.1 A downflow unit shall be set on its floor stand on the structural slab, level within the tolerance the manufacturer publishes so that the drain pan slopes to its connection, with the floor stand height matching the finished raised floor height.
21.2.2 The raised floor cutout at each downflow unit shall be as shown on the reviewed shop drawings, and the cutout edges shall be supported and sealed so that supply air is not lost into any cavity other than the plenum.
21.2.3 The floor stand and turning plenum shall be sealed to the raised floor so that supply air enters the plenum only, and the plenum under the unit shall be clear of cable, piping, and debris for the extent the manufacturer requires for the discharge.
21.2.4 Where the fans are extended into the raised floor plenum, the plenum depth at the unit shall be not less than the depth the manufacturer requires, and the fan assembly shall not bear on the slab.
21.2.5 The raised floor system, its pedestals and stringers at the cutout, its airflow panels, and the sealing of cable cutouts elsewhere in the plenum are furnished under Raised Access FlooringRaised Access FlooringResolves to the current adopted revision.sync/raised-access-flooring.
NOTE The plenum is the duct, and a plenum that leaks at cable cutouts, at the wall, or around the unit itself starves the tiles farthest from the unit first. The cutout under the unit is the one leak the unit installer owns. (21.2.6)

21.3 Support and Restraint

21.3.1 Units shall be anchored to the slab or the floor stand, and the floor stand to the slab, with the anchors the manufacturer and the restraint calculations designate.
21.3.2 Ceiling-mounted units shall be hung from the structure on hangers rated for the operating weight, with the hangers and isolators furnished under Hangers And SupportsHangers and Supports for Mechanical Piping and EquipmentResolves to the current adopted revision.sync/hangers-and-supports and Vibration Isolation And Seismic RestraintVibration Isolation and Seismic RestraintResolves to the current adopted revision.sync/vibration-isolation-and-seismic-restraint.
21.3.3 Seismic restraint shall be furnished for the units and the remote heat rejection equipment as indicated in the datasheet.
Seismic Restraint Requiredradio
○ Seismic restraint required
○ Seismic restraint not required
Derived — Seismic Design CategorySeismic Design CategoryParameterEach project supplies its own value.seismic-design-category and the component importance factor ASCE/SEI 7 assigns to the equipment (by default)
21.3.4 Where seismic restraint is required, the restraint devices and their attachments shall be furnished under Vibration Isolation And Seismic RestraintVibration Isolation and Seismic RestraintResolves to the current adopted revision.sync/vibration-isolation-and-seismic-restraint in accordance with the sealed calculations submitted, and the unit anchorage shall be compatible with the vibration isolation furnished.
21.3.5 Remote condensers and drycoolers shall be set on a level support, anchored for the wind and seismic forces ASCE/SEI 7 assigns to the site, and located so that the discharge of one is not drawn into the intake of another or into any outdoor air intake.
21.3.6 Remote condensers and drycoolers shall be located so that the refrigerant or glycol piping between them and the units does not exceed the length and lift the manufacturer publishes for the matched pair without the corrections stated in the submittal.

21.4 Piping Connections

21.4.1 Chilled water, condenser water, and glycol piping to the unit connections shall be installed under Hydronic PipingHydronic PipingResolves to the current adopted revision.sync/hydronic-piping, with the isolation valves furnished under HVAC Piping ValvesGeneral-Duty Valves for HVAC PipingResolves to the current adopted revision.sync/hvac-piping-valves and the balancing valve, strainer, and pressure and temperature test ports furnished under Hydronic SpecialtiesHydronic SpecialtiesResolves to the current adopted revision.sync/hydronic-specialties at each unit.
21.4.2 Refrigerant piping between a direct-expansion unit and its remote condenser or drycooler shall be installed, pressure tested, evacuated, and charged under Refrigerant PipingRefrigerant PipingResolves to the current adopted revision.sync/refrigerant-piping, in the sizes and with the specialties the unit manufacturer designates for the matched pair.
21.4.3 Piping within the room shall be routed under the raised floor or overhead as shown on the drawings, shall be supported independently of the unit so that coil and valve removal does not require dismantling the connected piping, and shall be insulated with a continuous vapor-tight insulation under Mechanical InsulationMechanical InsulationResolves to the current adopted revision.sync/mechanical-insulation so that no surface sweats over the equipment below.
21.4.4 Where piping is routed overhead in a room, it shall not pass directly over equipment racks or over the electrical distribution unless drip protection is furnished beneath it.
21.4.5 Humidifier supply water piping shall be installed with a backflow preventer, an isolation valve, and a strainer at the unit connection, and shall deliver water of the quality the humidifier requires.
NOTE A leak in a computer room is a leak over the one thing in the building that cannot get wet, and every pipe route in the room is drawn around that fact. The piping goes where a leak drains harmlessly and a detector sees it first. (21.4.6)

21.5 Condensate Connections

21.5.1 The condensate drain shall be trapped at the unit with a trap sized for the pan static pressure, sloped continuously to the point of disposal, and primed before the unit is started in cooling.
21.5.2 Where a condensate pump is furnished, its discharge shall be connected with a check valve and routed so that the discharge line does not drain back into the pan.
21.5.3 Humidifier drain water, where the humidifier type produces drain water above the temperature the drain piping is rated for, shall be tempered or run in piping rated for the temperature before it enters the condensate system.

21.6 Electrical and Control Wiring

21.6.1 Electrical connections shall be made in accordance with Adopted Electrical CodeAdopted Electrical CodeParameterEach project supplies its own value.adopted-electrical-code, with flexible conduit at the unit where the unit is on vibration isolation.
21.6.2 Control and teamwork network wiring shall be run in the raceway the unit manufacturer designates, segregated from power wiring, and terminated on the labeled terminals shown on the submitted wiring diagram.
21.6.3 The fire alarm shutdown input and the remote stop required by NFPA 70 Article 645 where that article is applied shall be wired and tested before the unit is started.
21.6.4 Remote intake sensors and leak detectors furnished with the unit shall be installed at the locations shown on the reviewed shop drawings and their wiring protected from the cable management of the racks they are mounted on.

21.7 Pre-Startup Inspection

21.7.1 Before any unit is energized, the Contractor shall complete and record the inspection items indicated in the datasheet.
Pre-Startup Inspection Itemscheckbox
☑ Unit level and drain pan sloping to its connection
☑ Floor stand sealed to the raised floor and plenum under the unit clear
☑ Shipping restraints removed and fans and compressors free to move
☑ Piping connections complete, flushed, and leak tested
☐ Refrigerant piping tested, evacuated, and charged
☐ Glycol concentration verified
☑ Condensate trap installed and primed
☐ Humidifier water supply connected and drain complete
☑ Electrical connections complete and phase rotation verified
☑ Disconnecting means operable
☑ Control, teamwork, and monitoring wiring terminated
☑ Fire alarm shutdown and remote stop wired
☑ Leak detectors and remote intake sensors installed
☑ Filters installed
☑ Service clearances verified clear
☐ Refrigerant detection sensors in place and dated
21.7.2 The inspection record shall mark as not applicable the items that do not apply to the unit's cooling type and options, rather than omitting them.
21.7.3 Units shall not be operated to provide temporary cooling during construction unless the Engineer of Record accepts the temporary use in writing and the Contractor replaces every filter and cleans every coil, pan, and cabinet so operated before Substantial Completion.

22 Startup and Commissioning

22.1 Startup Service

22.1.1 The startup service shall be as indicated in the datasheet.
Startup Serviceselect
Startup performed by a factory-authorized service representative
Startup performed by the installing contractor with factory technical support
Startup performed by the installing contractor
NOTE A factory representative starts a unit with the manufacturer's tools, the manufacturer's configuration software, and the warranty's terms in hand, which on equipment whose controller and teamwork network are proprietary is the only party that can configure the group; the installing contractor can start the unit itself, and a project with staff who know the product line and a warranty that does not require the factory start can save the service call. (22.1.2)
22.1.3 Startup shall verify the refrigerant charge on each circuit against the nameplate and the published subcooling or superheat target, the operation of each compressor across its stages or range, the fan speeds and airflow at the design operating point, the control valve stroke, the humidifier and reheat operation, the economizer changeover, the trip of every safety device at its setpoint, the leak detectors, the fire alarm shutdown, and the refrigerant detection and mitigation sequence where a detection system is furnished.
22.1.4 Each safety device shall be tested by driving the condition it senses to its setpoint rather than by simulating the device output.
22.1.5 The startup report shall record the measured airflow, external static pressure, fan speeds, motor currents, refrigerant operating pressures and temperatures by circuit, glycol concentration, water flows, and the setpoint of every safety device.

22.2 Airflow and Water Flow Verification

22.2.1 The testing and balancing agent shall verify the airflow at each unit at the design operating point and the raised floor plenum static pressure at the locations the sequence of operation states, in accordance with Testing Adjusting And BalancingTesting, Adjusting, and Balancing for HVACResolves to the current adopted revision.sync/testing-adjusting-and-balancing.
22.2.2 The testing and balancing agent shall set and verify the water or glycol flow through each coil and condenser at the scheduled flow, in accordance with Testing Adjusting And BalancingTesting, Adjusting, and Balancing for HVACResolves to the current adopted revision.sync/testing-adjusting-and-balancing, using the balancing device or the pressure-independent valve furnished.
22.2.3 Where a unit cannot be brought to the scheduled airflow at the design fan speed or to the scheduled flow, the testing and balancing agent shall report the condition to the Engineer of Record rather than raising the fan speed or the valve setting to match the schedule.

22.3 Functional Performance Testing

22.3.1 The commissioning scope shall be as indicated in the datasheet.
Commissioning Scopecheckbox
☑ Manufacturer startup with a signed report
☑ Point-to-point verification of every control device
☑ Functional performance testing of the control sequence on every unit
☑ Teamwork group staging, lead rotation, and standby start on a simulated unit failure
☑ Redundancy failover with the room held in its envelope at the available load
☐ Economizer changeover across the changeover condition
☐ Humidity control coordination across units
☑ Leak detection alarm and automatic valve closure by wetted sensor
☑ Fire alarm shutdown and remote stop by initiated signal
☐ Refrigerant detection and mitigation by introduced signal
☐ Capacity verification at the design envelope under a load bank or the installed load
☐ Trend review over a seasonal period
22.3.2 Commissioning shall be performed in accordance with ANSI/ASHRAE 202 and CommissioningTotal Building CommissioningResolves to the current adopted revision.sync/commissioning.
22.3.3 Redundancy failover shall be demonstrated by taking each unit in turn out of service with the room at the available load, and the remaining units shall hold the room within the selected envelope for not less than one hour.
22.3.4 Where a functional performance test fails, the Contractor shall correct the deficiency and shall bear the cost of retesting that unit.
NOTE A computer room unit is commissioned before the load it was bought for exists, and the sequence that will matter most, the one that runs when a unit fails at full load in a heat wave, is the one no one sees unless it is forced. A load bank in the room is the only way to see the units at their design condition before the equipment does. (22.3.5)

23 Identification

23.1 Each unit shall be furnished with a permanent nameplate on the exterior of the cabinet, mechanically fastened rather than adhered, stating the unit tag, the manufacturer, the model and serial number, the net sensible cooling capacity, the airflow, the refrigerant designation and factory charge by circuit where applicable, the electrical characteristics including minimum circuit ampacity and maximum overcurrent protective device, and the date of manufacture.
23.2 The unit tag on the nameplate shall match the tag used in the Contract Documents, on the monitoring system, and in the operation and maintenance manuals.
23.3 Each remote condenser and drycooler shall bear a nameplate stating the tag of the unit or units it serves, in addition to the manufacturer's data.
23.4 Units charged with a refrigerant in a flammable safety group shall bear the flammable refrigerant marking UL 60335-2-40 and ANSI/ASHRAE 15 require, applied at the location the listing designates.
23.5 The filter access panel shall be labeled with the filter efficiency and sizes the unit holds, and the electrical compartment shall contain a permanently mounted copy of the unit wiring diagram.
23.6 Equipment identification shall otherwise conform to Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling.

24 Warranty

24.1 Unit Warranty

24.1.1 The manufacturer shall warrant each unit and its remote heat rejection equipment against defects in materials and workmanship for the terms indicated in the datasheet.
Unit Parts Warranty Termrange
Not less than
years
123510
Unit Labor Warranty Termrange
Not less than
years
1235
Warranty Start Milestoneradio
● Date of Substantial Completion
○ Date the Owner takes beneficial use of the room
○ Date of shipment
NOTE Parts and labor are separate commitments 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 and the refrigerant, so the two terms have to be read together to know what the coverage is worth on a unit that runs every hour. The start milestone matters on a room that is built long before it is loaded; a warranty that starts at shipment can be half spent before the first server arrives. (24.1.2)
24.1.3 The unit warranty shall cover the cabinet, the coils, the fans and motors, the compressors, the control valve, the humidifier, the reheat, the drain pan, the controller and sensors, the leak detectors, and every component of the remote condenser, drycooler, and pump package furnished by the unit manufacturer.
24.1.4 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.

24.2 Compressor Warranty

24.2.1 Requirements in this article apply where a cooling type with a direct-expansion circuit is selected in the datasheet.
24.2.2 Each compressor shall be warranted against defects in materials and workmanship for the term indicated in the datasheet, in addition to the unit warranty.
Compressor Warranty Termrange
Not less than
years
123510
24.2.3 The compressor warranty shall not be conditioned on service by the manufacturer's own organization where the service is performed by a technician certified under 40 CFR Part 82 Subpart F and, for a flammable refrigerant, trained for that refrigerant.

24.3 Warranty Service

24.3.1 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, and shall respond to a warranty notification within 1 business day.
24.3.2 The Contractor shall warrant the installation, including the floor stand and plenum sealing, anchorage and restraint, piping and refrigerant connections, condensate connections, electrical connections, control and network wiring, leak detector and sensor placement, and identification, for the term indicated in the datasheet.
Installation Warranty Termrange
Not less than
years
1235
24.3.3 A defect attributable to the installation shall be corrected at the Contractor's expense, and where a warranty repair requires removal of raised floor panels, racks, or other adjacent work, the cost of removing and restoring that work shall be borne by the party responsible for the defect.
24.3.4 The Contractor shall keep every installed unit accessible during the warranty period by keeping access panels, floor panels at the unit, and adjacent construction clear of permanent obstruction.
24.3.5 The manufacturer's warranty shall not be voided by a filter change, a humidifier cylinder or media change, a refrigerant charge adjustment, a detection sensor replacement, or a fan speed adjustment performed in accordance with the operation and maintenance manual by a qualified technician.

25 Spare Parts

25.1 The Contractor shall furnish the spare parts indicated in the datasheet at Substantial Completion.
Spare Parts Furnishedcheckbox
☑ One complete set of filters of every size and rating installed
☐ Two complete sets of filters of every size and rating installed
☑ One fan and motor assembly of each size and type installed
☐ One set of drive belts for every belt-driven fan
☑ One humidifier cylinder, lamp set, transducer, or media of each type installed
☐ One control valve actuator for each actuator model installed
☐ One unit controller for each controller model installed
☑ One leak detector of each type installed
☐ One remote intake sensor of each type installed
☐ One refrigerant detection sensor for each unit on which a detection system is furnished
☐ One condensate pump of each model installed
☑ One set of every fuse type installed
NOTE The fan is the spare that keeps a room in its envelope while a failed fan is on order, and on a unit whose fans can be changed one at a time while the others run, it is the part that turns a failure into a maintenance item. The humidifier consumable is the part that is otherwise ordered the week it runs out. (25.2)
25.3 Spare parts shall be delivered in the manufacturer's original packaging, each tagged with the model number, the unit tags it serves, and the date of delivery, at a storage location the Owner designates, and the transfer shall be documented in the closeout submittal.
25.4 The operation and maintenance manual shall include a spare parts inventory listing the manufacturer part number and reorder information for every component of the units furnished, a filter change schedule derived from the initial and change-out resistances stated in the submittal, and, where a detection system is furnished, the replacement date of each refrigerant detection sensor.

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"Computer Room Air Conditioning Units," SynC Standards, revision 5. Licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://synergyinconstruction.com/standards/general/computer-room-air-conditioning. Reference material only; not professional engineering advice and provided without warranty. Verify against governing codes and have a licensed professional review before use.