+---
+title: Unit Heaters
+category: Mechanical / Air Distribution
+toc_depth: 3
+description: >
+ When to use: self-contained, fan-driven space heaters serving unconditioned or
+ intermittently occupied spaces (garages, warehouses, loading docks, mechanical
+ rooms, vestibules, hangars). Covers propeller-fan and cabinet/blower unit heaters
+ with hot-water, steam, gas-fired (natural gas or propane), or electric heating
+ elements, including selection, mounting, discharge orientation, controls, clearances
+ to combustibles, and venting/combustion-air provisions for gas-fired units.
+ Not intended for: fin-tube radiation, convectors, and panel radiators (use
+ sync/terminal-heating-units); architectural cabinet units with cooling coils or
+ full-perimeter enclosures (sync/fan-coil-units); duct-mounted or inline heating
+ coils without integral fans (the air-handling/ductwork scope, sync/hvac-fans);
+ infrared radiant tube heaters and radiant ceiling panels (a separate radiant product
+ class, not addressed here); upstream hydronic supply/return piping
+ (sync/hydronic-piping); gas branch piping and connections (sync/natural-gas-piping);
+ and central air-handling units serving multiple zones through ductwork
+ (sync/hvac-fans).
+---
+
+# Scope {toc}
+
+## This standard covers self-contained, fan-driven unit heaters that deliver heat directly into a space by forced convection, including propeller-fan suspended and cabinet types served by hot water, steam, gas combustion, or electric resistance. {note}
+
+## Unit heaters are used to maintain space temperature in unconditioned or semi-conditioned, unoccupied or intermittently occupied areas where ducted comfort conditioning is neither warranted nor economical. {note}
+
+## Typical applications include parking and repair garages, warehouses and distribution centers, loading docks and overhead-door bays, mechanical and electrical rooms, entry vestibules, aircraft hangars, fabrication shops, and similar spaces. The heater discharges directly into the occupied volume; no supply ductwork distributes the air except where a high-static blower type is specifically selected for a short duct connection. {note}
+
+## The standard addresses heating-capacity selection, heating-medium selection, fan and discharge configuration, mounting, controls integration, clearances to combustibles, and the venting and combustion-air provisions required for gas-fired units. {note}
+
+## It applies to both new construction and retrofit on commercial, industrial, and institutional projects. {note}
+
+## Equipment furnished under this standard shall be a factory-assembled, factory-tested unit heater listed and labeled for its heating medium and intended application. {toc}
+
+### Each unit heater shall be a complete factory-assembled package comprising the heating element or heat exchanger, fan and motor, casing, and integral controls as scheduled.
+
+### Each unit heater shall be listed and labeled by a nationally recognized testing laboratory for the heating medium and the service conditions in which it is installed.
+
+### Field-assembled combinations of separately furnished heating coils, fans, and casings shall not be substituted for a listed unit heater.
+
+## Exclusions {toc}
+
+### Fin-tube radiation, convectors, panel radiators, and radiant floor or ceiling panels are terminal heating devices covered by sync/terminal-heating-units and are excluded here. {note}
+
+### Architectural cabinet units with integral cooling coils or full-perimeter finished enclosures are covered by sync/fan-coil-units and are excluded here. {note}
+
+### Duct-mounted heating coils and inline duct heaters without an integral fan belong to the air-handling and ductwork scope and are excluded here. {note}
+
+### Infrared radiant tube heaters and radiant ceiling panels, which heat by radiation rather than forced convection, are a separate product class not addressed in this standard. {note}
+
+### Hydronic supply and return piping upstream of the unit-heater connection is covered by sync/hydronic-piping and is excluded here. {note}
+
+### Natural-gas branch piping and the gas connection to the heater are covered by sync/natural-gas-piping and are excluded here. {note}
+
+### Central air-handling units serving multiple zones through ductwork are covered by sync/hvac-fans and are excluded here. {note}
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| ANSI Z83.8 / CSA 2.6 | Gas Unit Heaters, Gas Packaged Heaters, Gas Utility Heaters, and Gas-Fired Duct Furnaces |
+| UL 2021 | Fixed and Location-Dedicated Electric Room Heaters |
+| NFPA 54 | National Fuel Gas Code |
+| NFPA 70 | National Electrical Code (NEC) |
+| NFPA 88A | Standard for Parking Structures |
+| ASHRAE Handbook | HVAC Systems and Equipment, Chapter 28 (Unit Ventilators, Unit Heaters, and Makeup Air Units) |
+| ASHRAE 90.1 | Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings |
+| IMC | International Mechanical Code |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following action submittals for each unit heater type and tag before fabrication or ordering:
+
+- Product data with rated heating capacity, fan airflow, motor data, and electrical characteristics for each tagged unit.
+- Manufacturer's certified capacity data at the scheduled entering medium conditions (entering water temperature and flow, or steam pressure, or gas input, or electric kW).
+- Dimensioned drawings showing casing size, discharge arrangement, mounting provisions, and connection locations.
+- Wiring diagrams showing integral controls, motor protection, and field control terminations.
+- Listing and labeling documentation identifying the heating medium and any hazardous-location rating.
+- For gas-fired units, vent category, vent connection size and material, and combustion-air requirement.
+
+```datasheet
+label: Action submittals
+type: checkbox
+options:
+ - Product data with rated capacity and electrical data
+ - Certified capacity at scheduled entering conditions
+ - Dimensioned unit drawings with connection locations
+ - Control and power wiring diagrams
+ - Listing/labeling documentation
+ - Gas vent category, size, material, and combustion-air data
+```
+
+## Closeout Submittals {toc}
+
+### The Contractor shall submit the following closeout submittals before Substantial Completion:
+
+- Operation and maintenance manuals for each unit heater type.
+- As-installed wiring diagrams reflecting field control terminations.
+- Startup and combustion-test reports for gas-fired units, signed by the startup technician.
+- Air-balance report entries for each unit heater, coordinated with sync/testing-adjusting-and-balancing.
+- Executed warranty documents.
+
+```datasheet
+label: Closeout submittals
+type: checkbox
+options:
+ - Operation and maintenance manuals
+ - As-installed wiring diagrams
+ - Gas-fired startup and combustion-test reports
+ - Air-balance report entries
+ - Executed warranty documents
+```
+
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following informational submittals for review:
+
+- Heat-loss calculation summary supporting the scheduled heating capacity for each space served.
+- Combustion-air calculation for each gas-fired unit, demonstrating compliance with NFPA 54.
+- Hanger and seismic-restraint details for suspended units.
+
+```datasheet
+label: Informational submittals
+type: checkbox
+options:
+ - Heat-loss calculation summary
+ - Combustion-air calculation per NFPA 54
+ - Hanger and seismic-restraint details
+```
+
+# Quality Assurance {toc}
+
+## Listing-and-labeling enforcement is the load-bearing quality control for unit heaters because a field substitution of an unlisted assembly defeats the combustion-safety and electrical-safety basis of the design. {note}
+
+### Gas-fired unit heaters shall be listed and labeled in accordance with ANSI Z83.8 / CSA 2.6.
+
+### Electric unit heaters intended for permanent installation shall be listed and labeled in accordance with UL 2021.
+
+### The manufacturer shall have produced unit heaters of the specified type and capacity range for not less than five years.
+
+### Capacity ratings shall be established by test in accordance with the applicable listing standard and shall not be derived solely by interpolation outside the tested range.
+
+## Manufacturer-agnostic procurement {note}
+
+### Substitutions shall match the scheduled heating capacity, airflow, discharge arrangement, electrical characteristics, and physical envelope without requiring modification of structure, piping, venting, or electrical service.
+
+# Environmental and Service Conditions {toc}
+
+## Because unit heaters serve unconditioned spaces, the service environment, not the comfort design point, governs many selections: combustion air availability, freeze exposure, airborne contaminants, and door-open infiltration all drive the equipment choice. {note}
+
+## Infiltration is the most commonly underestimated load. {note}
+
+## Loading-dock and overhead-door bays lose large quantities of heat whenever a door is open, and a heater sized only to the steady-state envelope loss will not recover the space. The heating-capacity selection shall account for the door-open infiltration load for the design door-open condition, not the closed-envelope load alone. {note}
+
+### The heating-capacity selection shall include the infiltration and door-open heat loss for spaces served by overhead or large vehicular doors.
+
+### Where a space is exposed to outdoor air through frequently opened doors, the design entering-air temperature for capacity rating shall be the space design temperature, not a warmer assumed mixed-air temperature.
+
+## Freeze protection {note}
+
+## Hydronic and steam units installed in vestibules, loading docks, and other spaces that can fall below freezing when unoccupied are exposed to coil freeze damage, especially when served from a system without antifreeze. The design shall provide a freeze-protection strategy for any wet-coil unit in a freeze-exposed location. {note}
+
+### Hydronic unit heaters in freeze-exposed locations shall be provided with a freeze-protection means: a glycol-rated coil on a glycol system, a low-limit aquastat that maintains minimum coil temperature, or a coil drain provision, as scheduled.
+
+### A hydronic unit heater shall not be specified for a freeze-exposed location on a non-glycol system without one of the freeze-protection means above.
+
+## Airborne contaminants and hazardous locations {note}
+
+### Cabinet (blower-type) unit heaters installed in spaces with suspended dust, sawdust, or metal filings shall be furnished with totally enclosed fan-cooled (TEFC) motors.
+
+### Unit heaters installed in classified hazardous locations shall be listed for the applicable class and division, and shall not be field-modified to achieve that rating.
+
+```datasheet
+label: Service environment
+type: radio
+options:
+ - Heated, weather-protected (mechanical room, interior bay)
+ - Freeze-exposed (vestibule, loading dock)
+ - Door-open infiltration (overhead-door bay, dock)
+ - Contaminant-laden (shop, fabrication area)
+ - Classified hazardous location
+default: Heated, weather-protected (mechanical room, interior bay)
+```
+
+```datasheet
+label: Hazardous-location classification
+type: radio
+options:
+ - None (general purpose)
+ - Class I, Division 2
+ - Class I, Division 1
+ - Class II, Division 2
+default: None (general purpose)
+```
+
+# Heating Medium and Capacity {toc}
+
+## The heating medium is the first selection and it cascades into nearly every other decision: capacity rating basis, control method, venting, clearances, and electrical or piping service. {note}
+
+## The four media in common use are hot water (hydronic), steam, gas-fired combustion (natural gas or propane), and electric resistance. Hydronic and electric units are the most common in new commercial construction; gas-fired units are common where a central heating plant is absent; steam units are now rare in new work but frequent in older industrial renovations and shall be supported where an existing steam distribution system is the available medium. {note}
+
+### The unit-heater heating medium shall be selected from the available building distribution system or fuel source and coordinated with the Engineer of Record.
+
+```datasheet
+label: Heating medium
+type: radio
+options:
+ - Hot water (hydronic)
+ - Steam
+ - Gas-fired, natural gas
+ - Gas-fired, propane (LP)
+ - Electric resistance
+default: Hot water (hydronic)
+```
+
+## Heating capacity {note}
+
+## Heating capacity shall be established by a heat-loss calculation for the served space at the design conditions, including the infiltration provisions above. Capacity is expressed in MBH (thousands of Btu/h) for hydronic, steam, and gas units, and in kW for electric units. {note}
+
+### The scheduled heating capacity shall be derived from a heat-loss calculation for the served space and shall not be assigned by floor area alone.
+
+### The rated capacity shall be certified at the scheduled entering medium condition, not at a nominal catalog condition more favorable than the design.
+
+```datasheet
+label: Heating capacity (hydronic, steam, gas-fired)
+type: range
+unit: MBH
+min: 10
+max: 400
+step: 5
+drawing_ref: true
+```
+
+```datasheet
+label: Heating capacity (electric)
+type: range
+unit: kW
+min: 3
+max: 50
+step: 0.5
+drawing_ref: true
+```
+
+## Hydronic entering conditions {note}
+
+## For hot-water units the rated output depends on entering water temperature and flow; the design shall pin both so the certified rating matches the served load. {note}
+
+### The rated output of a hydronic unit heater shall be certified at the scheduled entering water temperature and design water flow.
+
+### The hydronic coil shall be selected for the system entering water temperature; a unit selected for a higher temperature than the system delivers shall not be substituted.
+
+```datasheet
+label: Hydronic entering water temperature
+type: range
+unit: °C
+min: 49
+max: 93
+step: 1
+setpoints: [60, 71, 82]
+default: 82
+```
+
+```datasheet
+label: Hydronic design water flow
+type: range
+unit: L/s
+min: 0.1
+max: 3.0
+step: 0.05
+drawing_ref: true
+```
+
+## Steam conditions {note}
+
+### A steam unit heater shall be selected and certified at the scheduled steam supply pressure.
+
+### Where the steam system is high pressure, the steam pressure used for capacity rating shall match the pressure delivered at the unit, accounting for distribution losses.
+
+```datasheet
+label: Steam supply pressure class
+type: radio
+options:
+ - Low pressure (≤ 103 kPa / 15 psig)
+ - Medium pressure (103-862 kPa)
+ - High pressure (> 862 kPa)
+default: Low pressure (≤ 103 kPa / 15 psig)
+```
+
+# Fan and Discharge Configuration {toc}
+
+## The fan type and discharge orientation determine where the heater can be applied and how the warm air is distributed; a propeller unit and a cabinet/blower unit are not interchangeable. {note}
+
+## Propeller-fan unit heaters move large airflow against low static pressure and are intended for open, unfinished spaces with direct discharge into the volume. Cabinet (centrifugal/blower) units develop higher static pressure, accept short duct connections or filter sections, and suit finished or semi-finished spaces. Calling out only "unit heater" without distinguishing the two routinely generates submittal rejections, because a propeller unit cannot serve a ducted or finished application. {note}
+
+### The fan type shall be specified as propeller-fan or cabinet (centrifugal/blower); a unit heater shall not be scheduled without this distinction.
+
+### A propeller-fan unit heater shall not be connected to supply ductwork.
+
+### A cabinet (blower-type) unit shall be specified where a short duct connection, filter section, or finished casing is required.
+
+```datasheet
+label: Fan type
+type: radio
+options:
+ - Propeller fan (open, unfinished spaces)
+ - Cabinet / centrifugal blower (finished or ducted)
+default: Propeller fan (open, unfinished spaces)
+```
+
+## Discharge orientation {note}
+
+## Horizontal-discharge units throw warm air across the space and suit lower mounting heights and wider coverage; vertical-discharge (downblow) units project heat to the floor from high mounting and suit tall spaces. Multi-position units can be field-set to either. The discharge orientation shall be coordinated with mounting height and the space geometry shown on the drawings. {note}
+
+### The discharge orientation shall be specified as horizontal, vertical (downward), or multi-position, coordinated with mounting height.
+
+### Vertical-discharge units serving tall spaces shall be furnished with an air-deflection or anti-stratification means where scheduled to drive warm air to the occupied level.
+
+```datasheet
+label: Discharge orientation
+type: radio
+options:
+ - Horizontal discharge
+ - Vertical (downward) discharge
+ - Multi-position (field-adjustable)
+default: Horizontal discharge
+```
+
+# Mounting and Clearances {toc}
+
+## Mounting configuration and clearance-to-combustibles requirements are safety and serviceability provisions, not aesthetics, and the gas-fired and high-pressure-steam cases carry code-mandated minimums. {note}
+
+### The mounting configuration shall be specified as ceiling-suspended, wall-mounted, or floor-standing, coordinated with the structural support shown on the drawings.
+
+### Suspended units shall be supported from building structure by hangers rated for the unit operating weight, not from ductwork, piping, or ceiling systems.
+
+```datasheet
+label: Mounting configuration
+type: radio
+options:
+ - Ceiling-suspended
+ - Wall-mounted
+ - Floor-standing
+default: Ceiling-suspended
+```
+
+## Mounting height for steam and high-temperature units {note}
+
+## High-pressure steam and high-temperature hot-water units discharging into occupied or parking areas can present a burn hazard at low mounting heights; NFPA 88A and ASHRAE establish a minimum discharge height above the floor in those areas. {note}
+
+### High-pressure steam unit heaters discharging into occupied or parking areas shall be mounted with the discharge not less than 4 m (13 ft) above the finished floor.
+
+### The mounting height of each suspended unit shall be coordinated with the discharge orientation so the throw reaches the occupied level without creating an objectionable draft.
+
+```datasheet
+label: Mounting height above finished floor
+type: range
+unit: m
+min: 2.4
+max: 9.0
+step: 0.1
+drawing_ref: true
+```
+
+## Clearances to combustibles {note}
+
+### Gas-fired and high-temperature units shall be installed with the clearances to combustible construction marked on the listing label and required by NFPA 54 and the IMC.
+
+### Service access clearance shall be maintained at the burner, control, and fan-motor side of each unit for inspection and component replacement.
+
+### Clearance reductions using listed protective assemblies shall be applied only as permitted by the listing and the adopted mechanical code.
+
+# Gas-Fired Units {toc}
+
+## Gas-fired unit heaters add combustion safety to the design: venting category, combustion-air supply, ignition type, and gas connection must all be coordinated, and each is a common source of field RFIs and AHJ rejections when omitted. {note}
+
+## Venting category and vent material {note}
+
+## The vent category determines the vent material. Category I natural-draft appliances vent into a conventional vent under negative static pressure; Category IV positive-pressure (condensing) appliances require a sealed, corrosion-resistant vent rated for positive pressure and condensate, such as stainless steel or a listed special vent. Specifying a standard single-wall or Type B vent on a Category IV appliance is a rejection, as is the reverse mismatch. {note}
+
+### The vent category of each gas-fired unit shall be specified, and the vent material shall match that category.
+
+### Category IV positive-pressure units shall be vented with a vent system listed for positive pressure and condensate (stainless steel or listed special vent); standard Type B vent shall not be used.
+
+### Separated-combustion (sealed-combustion) units serving tightly insulated spaces shall be furnished with the manufacturer's listed intake and exhaust terminations.
+
+```datasheet
+label: Gas-fired vent category
+type: radio
+options:
+ - Category I (natural draft, Type B vent)
+ - Category III (positive pressure, non-condensing)
+ - Category IV (positive pressure, condensing)
+ - Separated combustion (sealed, direct vent)
+ - Unvented (only where code-permitted)
+default: Category I (natural draft, Type B vent)
+```
+
+```datasheet
+label: Vent material
+type: radio
+options:
+ - Type B double-wall (Category I)
+ - Single-wall metal (where permitted)
+ - AL29-4C / stainless special vent (Category III/IV)
+ - PVC/CPVC sealed (separated combustion, where listed)
+default: Type B double-wall (Category I)
+```
+
+## Combustion air {note}
+
+## NFPA 54 requires a verified volume of combustion air for fuel-burning appliances in confined spaces. Omitting the combustion-air calculation for units in tight mechanical rooms is a frequent cause of field RFIs and plan-review rejections. The design shall demonstrate adequate combustion air by room volume or provide a dedicated combustion-air opening or duct. {note}
+
+### Each gas-fired unit heater shall be provided with combustion air verified in accordance with NFPA 54.
+
+### Where the room volume is insufficient under NFPA 54, a combustion-air opening or duct sized per the code shall be provided and shown on the drawings.
+
+### A combustion-air calculation shall be submitted for each gas-fired unit demonstrating compliance.
+
+## Ignition {note}
+
+## Standing-pilot ignition wastes fuel and is increasingly disallowed; ASHRAE 90.1 and many jurisdictions require an intermittent or direct-spark ignition (DSI) system for commercial gas appliances. Specifying a standing pilot without a code check frequently fails plan review. {note}
+
+### Gas-fired unit heaters shall be furnished with intermittent or direct-spark ignition (DSI); standing-pilot ignition shall not be used unless specifically permitted by the adopted code and the Engineer of Record.
+
+```datasheet
+label: Gas ignition type
+type: radio
+options:
+ - Direct spark ignition (DSI)
+ - Intermittent (hot-surface) ignition
+ - Standing pilot (only where code-permitted)
+default: Direct spark ignition (DSI)
+```
+
+## Fuel and gas connection {note}
+
+### The fuel type shall be specified as natural gas or propane and the unit shall be furnished or factory-converted for that fuel.
+
+### The gas connection shall terminate at a manual shutoff and union ahead of the unit for service isolation, coordinated with sync/natural-gas-piping.
+
+```datasheet
+label: Fuel type
+type: radio
+options:
+ - Natural gas
+ - Propane (LP)
+default: Natural gas
+```
+
+# Electric Units {toc}
+
+## Electric unit heaters avoid combustion and venting entirely and suit spaces where no fuel or central plant is available; their constraints are electrical service capacity and element staging rather than combustion safety. {note}
+
+### Electric unit heaters shall be furnished with the heating elements, contactors, and integral high-limit protection required for the scheduled kW and voltage.
+
+### Electric elements shall be staged where scheduled to limit inrush and to permit modulating control of output.
+
+### Electric units in classified hazardous locations shall be of the listed explosion-proof type for the applicable class and division.
+
+```datasheet
+label: Electric element staging
+type: radio
+options:
+ - Single stage
+ - Two stage
+ - Multi-stage / step controller
+default: Single stage
+```
+
+# Electrical and Motor {toc}
+
+## Motor voltage and phase must be coordinated with the building electrical distribution, and the NEC imposes disconnect and overload-protection requirements that are frequently missed on suspended units. {note}
+
+### The motor voltage and phase shall be coordinated with the electrical distribution serving the space and scheduled on the drawings.
+
+### A disconnecting means shall be provided within sight of and readily accessible to each unit-heater motor in accordance with NEC Article 430.
+
+### Motor overload protection shall be provided as required by NEC Article 430.
+
+### The fan motor shall be of the enclosure type suited to the service environment (TEFC where dust or contaminants are present).
+
+```datasheet
+label: Motor voltage and phase
+type: radio
+options:
+ - 120 V, 1Φ
+ - 208 V, 1Φ
+ - 208 V, 3Φ
+ - 240 V, 1Φ
+ - 277 V, 1Φ
+ - 480 V, 3Φ
+default: 208 V, 1Φ
+```
+
+```datasheet
+label: Motor enclosure type
+type: radio
+options:
+ - Open drip-proof (ODP)
+ - Totally enclosed fan-cooled (TEFC)
+ - Explosion-proof (hazardous location)
+default: Open drip-proof (ODP)
+```
+
+# Controls {toc}
+
+## Controls integration is where the unit heater is most often left in a coordination gap, because the thermostat wiring falls between the mechanical and electrical drawings and the BAS scope. {note}
+
+## The control method ranges from a unit-mounted thermostat, through a remote wall thermostat, to full DDC control by the building automation system with a modulating valve on hydronic units or staged elements on electric units. The control method and the responsibility for control wiring shall be defined so the wiring does not fall into a scope gap. {note}
+
+### The control method shall be specified as unit-mounted thermostat, remote wall thermostat, or BAS/DDC control.
+
+### Control wiring responsibility shall be assigned on the drawings so unit-heater thermostat wiring appears on either the mechanical or electrical documents, not neither.
+
+### Hydronic units under BAS/DDC control shall be furnished or paired with a modulating control valve coordinated with sync/hydronic-piping.
+
+### A fan time-delay or fan-thermostat interlock shall be provided on hydronic and steam units to prevent the fan from blowing cold air before the coil is warm and to purge residual heat after a call ends.
+
+```datasheet
+label: Control method
+type: radio
+options:
+ - Unit-mounted thermostat
+ - Remote wall thermostat
+ - BAS / DDC control
+default: Remote wall thermostat
+```
+
+```datasheet
+label: Fan control interlock (wet-coil units)
+type: radio
+options:
+ - Fan thermostat (coil-temperature sensing)
+ - Fan time-delay relay
+ - Continuous fan (no interlock)
+default: Fan thermostat (coil-temperature sensing)
+```
+
+```datasheet
+label: Space heating setpoint
+type: range
+unit: °C
+min: 4
+max: 21
+step: 0.5
+default: 13
+```
+
+# Coil, Casing, and Construction {toc}
+
+## Construction requirements protect the heat-transfer surface and the casing from the harsh, often corrosive environments unit heaters serve. {note}
+
+### Hydronic and steam coils shall be copper-tube with aluminum or copper fins, factory leak-tested at not less than the rated working pressure.
+
+### The casing shall be steel with a factory-applied corrosion-resistant finish suitable for the service environment.
+
+### Adjustable discharge louvers or a diffuser shall be furnished to direct the air pattern as required by the application.
+
+### Steam coils shall be of the non-freeze (steam-distributing tube) type where the unit is exposed to entering air below freezing.
+
+```datasheet
+label: Coil construction (wet-coil units)
+type: radio
+options:
+ - Copper tube, aluminum fin
+ - Copper tube, copper fin
+ - Non-freeze steam-distributing coil
+default: Copper tube, aluminum fin
+```
+
+```datasheet
+label: Casing finish
+type: radio
+options:
+ - Standard baked enamel
+ - Epoxy / corrosion-resistant coating
+ - Galvanized
+default: Standard baked enamel
+```
+
+# Testing {toc}
+
+## Field testing confirms that the installed unit operates safely and delivers its rated output, and that gas-fired combustion is within the manufacturer's setup. {note}
+
+### Each unit heater shall be started and functionally tested for heating output, fan operation, and control response.
+
+### Gas-fired units shall be combustion-tested at startup and the results recorded on a signed startup report.
+
+### Each unit heater airflow shall be verified and recorded as part of the project air balance under sync/testing-adjusting-and-balancing.
+
+### Freeze-protection devices on wet-coil units shall be tested to confirm they activate at the scheduled setpoint.
+
+# Installation {toc}
+
+## Installation provisions ensure the unit is supported, connected, vented, and accessible per its listing and the mechanical code. {note}
+
+### Each unit heater shall be installed level and supported in accordance with the manufacturer's instructions and the mounting details on the drawings.
+
+### Suspended units in seismic regions shall be restrained in accordance with the project seismic-restraint requirements.
+
+### Hydronic and steam connections shall include isolation valves and unions at the unit for service removal, coordinated with sync/hydronic-piping.
+
+### Gas-fired units shall be vented and provided with combustion air as required by NFPA 54 and the IMC before being placed in operation.
+
+### Piping connected to wet-coil units shall be insulated where required by sync/mechanical-insulation.
+
+### Routing of piping, gas, vent, and electrical connections to each unit shall follow the arrangement shown on the drawings. [[drawing: unit connection routing]]
+
+# Delivery, Storage, and Handling {toc}
+
+## Unit heaters shall be delivered in the manufacturer's packaging with the listing label intact.
+
+## Units shall be stored indoors, protected from weather and construction dust, until installation.
+
+## Units shall be handled by their designated lifting points and shall not be lifted by the coil connections, vent collar, or discharge louvers.
+
+# Warranty {toc}
+
+## The manufacturer shall warrant each unit heater against defects in materials and workmanship for not less than one year from Substantial Completion.
+
+## Gas-fired heat exchangers shall carry an extended warranty of not less than ten years where scheduled.
+
+```datasheet
+label: Heat-exchanger warranty (gas-fired)
+type: radio
+options:
+ - 5 years
+ - 10 years
+ - 15 years
+default: 10 years
+```
+
+# Spare Parts {toc}
+
+## The Contractor shall furnish one complete set of spare ignition components for each gas-fired unit-heater type.
+
+## The Contractor shall furnish spare fan-motor capacitors and one spare fan motor for each electric and propeller-fan unit-heater type where scheduled.
+
+```datasheet
+label: Spare parts to furnish
+type: checkbox
+options:
+ - Spare ignition components (per gas-fired type)
+ - Spare fan-motor capacitors
+ - One spare fan motor per type
+```
+
+## --- {note}
+
+## This SynC standard is licensed under CC BY-SA 4.0. It was independently authored from public consensus standards, building codes, and general professional engineering knowledge. {note}