Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Gas-Fired Radiant and Infrared Heaters
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## Heaters covered here deliver heat primarily by infrared radiation to surfaces and occupants rather than by warming and circulating room air. {note}
−## The 80% case for an industrial project is a vented low-intensity straight-tube or U-tube heater, 100,000 to 150,000 BTU/hr, natural gas, two-stage or modulating, mounted at 16 to 24 ft above finished floor in a warehouse or manufacturing bay. {note}
+## The typical industrial installation is a vented low-intensity straight-tube or U-tube heater, 100,000 to 150,000 BTU/hr, natural gas, two-stage or modulating, mounted at 16 to 24 ft above finished floor in a warehouse or manufacturing bay. {note}
## The following are not within this scope: {note}
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## Tube material shall be selected for the corrosivity of the served environment.
−### Aluminized steel tube is the standard selection for dry, non-corrosive interior environments. {note}
−
−### Stainless steel tube shall be specified for combustion chambers and for installations exposed to washdown, salt, or chemical atmospheres.
−
−### Aluminized steel corrodes prematurely in washdown, salt, or chemical environments; stainless steel is required in those conditions. {note}
−
−### Titanium combustion-chamber tube may be specified for the most aggressive corrosive service where extended tube life justifies the cost. {note}
−
```datasheet
label: Tube material (low-intensity heaters)
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```
+### Aluminized steel tube is the standard selection for dry, non-corrosive interior environments. {note}
+
+### Stainless steel tube shall be specified for combustion chambers and for installations exposed to washdown, salt, or chemical atmospheres.
+
+### Aluminized steel corrodes prematurely in washdown, salt, or chemical environments; stainless steel is required in those conditions. {note}
+
+### Titanium combustion-chamber tube may be specified for the most aggressive corrosive service where extended tube life justifies the cost. {note}
+
## In Seismic Design Category C and above, heater supports and bracing shall be designed in accordance with IBC Table 1613 seismic provisions.
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## Each heater's input capacity shall be selected from the heat-loss calculation for the zone it serves.
−## Input capacity for a typical industrial low-intensity tube heater falls between 80,000 and 150,000 BTU/hr; the full covered range for the equipment family is 20,000 to 250,000 BTU/hr per unit. {note}
−
```datasheet
label: Rated input per heater
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```
+## Input capacity for a typical industrial low-intensity tube heater falls between 80,000 and 150,000 BTU/hr; the full covered range for the equipment family is 20,000 to 250,000 BTU/hr per unit. {note}
+
## High-intensity luminous heaters shall have a net radiant efficiency of not less than 55%.
## Low-intensity radiant tube heaters shall have a net radiant efficiency of not less than 45%.
−## Net radiant efficiency is the fraction of fuel input emitted as usable infrared radiation toward the occupied zone; the minimum thresholds reflect the AHRI 1330 / NECB basis and are the floor below which a heater is not considered an efficient radiant emitter. {note}
−
```datasheet
label: Minimum net radiant efficiency
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```
+## Net radiant efficiency is the fraction of fuel input emitted as usable infrared radiation toward the occupied zone; the minimum thresholds reflect the AHRI 1330 / NECB basis and are the floor below which a heater is not considered an efficient radiant emitter. {note}
+
## Steady-state thermal efficiency of the heater shall be not less than the minimum required by ASHRAE 90.1 where the project pursues energy code compliance.
−## Steady-state thermal efficiency for tube heaters typically ranges from 77% to 93% on a higher-heating-value basis; a standard tube heater is approximately 80% to 85%. {note}
−
```datasheet
label: Minimum steady-state thermal efficiency (HHV)
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```
+## Steady-state thermal efficiency for tube heaters typically ranges from 77% to 93% on a higher-heating-value basis; a standard tube heater is approximately 80% to 85%. {note}
+
# Heater Construction and Configuration {toc}
## Low-intensity heater tube geometry shall be selected for the coverage pattern and the available run length of the zone.
−### Straight single-pass tube provides a linear coverage pattern along the run and suits long aisles and perimeter runs. {note}
−
−### U-tube geometry folds the run to fit a shorter footprint while retaining tube length, and suits bays where a straight run will not fit. {note}
−
−### Multi-burner continuous-tube systems provide a single continuous radiating run served by multiple burners for very long coverage, and suit large open floors. {note}
−
```datasheet
label: Tube geometry (low-intensity)
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```
−## Tube length shall be coordinated with mounting height per the manufacturer's layout guide so that the coverage pattern is uniform over the occupied zone.
+### Straight single-pass tube provides a linear coverage pattern along the run and suits long aisles and perimeter runs. {note}
−## A long tube hung at a low mounting height concentrates heat unevenly along the run; the tube-length-to-mounting-height ratio shall be evaluated against the manufacturer's layout guide rather than chosen by tube length alone. {note}
+### U-tube geometry folds the run to fit a shorter footprint while retaining tube length, and suits bays where a straight run will not fit. {note}
−## The 80% case is a 40 ft straight or U-tube heater; the practical range is 20 to 80 ft for single-burner straight tubes, with U-tubes giving an equivalent effective length of roughly 30 to 60 ft. {note}
+### Multi-burner continuous-tube systems provide a single continuous radiating run served by multiple burners for very long coverage, and suit large open floors. {note}
+## Tube length shall be coordinated with mounting height per the manufacturer's layout guide so that the coverage pattern is uniform over the occupied zone.
+
```datasheet
label: Tube length (low-intensity)
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```
+## A long tube hung at a low mounting height concentrates heat unevenly along the run; the tube-length-to-mounting-height ratio shall be evaluated against the manufacturer's layout guide rather than chosen by tube length alone.
+
+## The most common length is a 40 ft straight or U-tube heater; the practical range is 20 to 80 ft for single-burner straight tubes, with U-tubes giving an equivalent effective length of roughly 30 to 60 ft. {note}
+
## Tube diameter shall be 4 in. for standard industrial capacity ranges and may be 3 in. for lower-capacity units.
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## Reflectors shall be provided over the full radiating length to direct radiant output downward toward the occupied zone.
−### Reflector finish shall be specified for the application; polished aluminum and polished stainless steel are the common finishes. {note}
+### Reflector finish shall be specified for the application; polished aluminum and polished stainless steel are the common finishes.
−### A higher-reflectance, durable finish increases the fraction of radiant output directed to the floor and resists tarnishing in dusty or humid spaces. {note}
−
```datasheet
label: Reflector material and finish
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```
+### A higher-reflectance, durable finish increases the fraction of radiant output directed to the floor and resists tarnishing in dusty or humid spaces. {note}
+
## Reflector assemblies shall include the manufacturer's expansion provision to accommodate thermal movement of the tube.
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## Each heater shall be mounted at the height and tilt angle shown on the heater layout plan [[drawing: heater mounting schedule]].
−## Mounting height for low-intensity tube heaters typically ranges from 10 to 35 ft, and for high-intensity luminous heaters from 8 to 20 ft; the 80% warehouse case mounts low-intensity heaters at 16 to 24 ft above finished floor. {note}
−
```datasheet
label: Mounting configuration
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```
+## Mounting height for low-intensity tube heaters typically ranges from 10 to 35 ft, and for high-intensity luminous heaters from 8 to 20 ft; most warehouses mount low-intensity heaters at 16 to 24 ft above finished floor. {note}
+
+## Clearances to combustibles shall comply with the listing label and the manufacturer's IOM for the specific model and mounting configuration.
+
+## Listed clearances for tube heaters are typically on the order of 48 to 84 in. above and 36 in. to the sides, but the listing label and IOM are the governing values for the supplied model and shall always be used in place of any generalized figure. {note}
+
+## The minimum mounting height and the maximum permitted combustible stacking height below each heater shall be shown on the layout plan and posted at the heaters.
+
```datasheet
label: Mounting height above finished floor
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```
−## Clearances to combustibles shall comply with the listing label and the manufacturer's IOM for the specific model and mounting configuration.
−
−## Listed clearances for tube heaters are typically on the order of 48 to 84 in. above and 36 in. to the sides, but the listing label and IOM are the governing values for the supplied model and shall always be used in place of any generalized figure. {note}
−
−## The minimum mounting height and the maximum permitted combustible stacking height below each heater shall be shown on the layout plan and posted at the heaters.
−
## NFPA 54 and NFPA 1 require posted signage for combustible clearances below radiant heaters; a specification that omits the minimum mounting height and maximum stacking height generates RFIs and fails code inspection. {note}
## The heater layout shall account for line-of-sight obstructions such as high racking, overhead cranes, and mezzanines so that no occupied area is shadowed.
−## Radiant heat travels in straight lines, so tall racking can shadow lower zones; where obstructions block coverage, supplemental lower-mount or spot heaters shall be added to the layout rather than relying on the overhead heaters alone. {note}
+## Radiant heat travels in straight lines, so tall racking can shadow lower zones; where obstructions block coverage, supplemental lower-mount or spot heaters shall be added to the layout rather than relying on the overhead heaters alone.
# Gas, Combustion Air, and Venting {toc}
## Each heater's required gas inlet pressure shall be verified against the available supply pressure at the heater connection.
−## Natural gas heaters typically require 6 to 14 in. W.C. inlet pressure and propane heaters typically require 11 to 14 in. W.C.; these requirements shall be coordinated with the building regulator and meter set, because a low-pressure distribution system can fail to deliver the heater's minimum inlet pressure. {note}
+## Natural gas heaters typically require 6 to 14 in. W.C. inlet pressure and propane heaters typically require 11 to 14 in. W.C.; these requirements shall be coordinated with the building regulator and meter set, because a low-pressure distribution system can fail to deliver the heater's minimum inlet pressure.
```datasheet
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## Unvented high-intensity heaters shall be installed only where mechanical ventilation provides at least 4 ft³/min per 1,000 BTU/hr of connected input, in accordance with NFPA 54.
−## Unvented luminous heaters shall not be specified in spaces with inadequate ventilation or with combustible storage directly below.
−
−## Unvented luminous heaters discharge combustion products into the space; specifying them where ventilation is inadequate or combustible storage is directly below creates both a fire code violation and a carbon monoxide hazard. {note}
−
```datasheet
label: Unvented ventilation rate (if unvented)
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```
+## Unvented luminous heaters shall not be specified in spaces with inadequate ventilation or with combustible storage directly below.
+
+## Unvented luminous heaters discharge combustion products into the space; specifying them where ventilation is inadequate or combustible storage is directly below creates both a fire code violation and a carbon monoxide hazard. {note}
+
# Electrical {toc}
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## The heater control strategy shall be selected for the zoning and turndown the space requires.
−### A single-stage thermostat zone is the simplest control and suits small or uniformly loaded spaces. {note}
−
−### Two-stage firing (typically 65% and 100%) reduces cycling and improves comfort in larger zones. {note}
−
−### Modulating control (typically 40% to 100% turndown) gives the smoothest output and the best part-load efficiency for large or variable loads. {note}
−
```datasheet
label: Control strategy
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```
+### A single-stage thermostat zone is the simplest control and suits small or uniformly loaded spaces. {note}
+
+### Two-stage firing (typically 65% and 100%) reduces cycling and improves comfort in larger zones. {note}
+
+### Modulating control (typically 40% to 100% turndown) gives the smoothest output and the best part-load efficiency for large or variable loads. {note}
+
## Where modulating or staged heaters are integrated with a building automation system, the interface protocol shall be confirmed with the BAS engineer before procurement.
−## Specifying modulating or staged controls without confirming the integration protocol with the building automation system results in standalone thermostats that cannot participate in demand-controlled heating; the protocol shall be coordinated with [[sync/building-automation-system]] before the heaters are released. {note}
+## Specifying modulating or staged controls without confirming the integration protocol with the building automation system results in standalone thermostats that cannot participate in demand-controlled heating; the protocol shall be coordinated with [[sync/building-automation-system]] before the heaters are released.
```datasheet
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- Flame-sense / safety control (per model)
```