Frequently Asked Questions


Do Space-Ray infrared radiant gas heaters have UL certification?

Because our infrared gas heaters are gas appliances, it is not necessary that they be listed by UL (a nationally recognized testing laboratory – NRTL); however, all of the electrical component parts are UL listed (e.g., the draft inducer motors, which are equipped with CSA and UL approved thermal protectors). Our heaters are certified by C.S.A. (a nationally recognized testing laboratory – NRTL) and carry the C.S.A. seal. All heaters are tested and meet or exceed all safety requirements set forth in American National Standard Z83.20 for infrared heaters.

Do Space-Ray infrared radiant gas heaters have FM certification?

Generally, Factory Mutual certification (a nationally recognized testing laboratory – NRTL) is applicable to products that cannot be certified at the manufacturer’s facility according to American National Standard and, therefore, need to be certified at the installation site. Our heaters are certified by C.S.A.(a nationally recognized testing laboratory – NRTL) and carry the CSA seal. All heaters are tested and meet or exceed all safety requirements set forth in American National Standard Z83.20. Factory Mutual recognizes C.S.A. certification.


Is this the heater that heats people but not the air?

This is inaccurate for complete building heating. Infrared heaters heat people, the floor slab and machinery first, but since infrared uses all methods of heat transfer (radiation, re-radiation, conduction and convection), the air is heated secondarily as it passes over the warm concrete. Therefore, the heaters can be controlled by air temperature sensing thermostats.


How long has Space-Ray been manufacturing infrared radiant gas heaters?

Space-Ray infrared gas heaters are manufactured by Gas-Fired Products, Inc., which was founded in 1949 and has been manufacturing infrared heaters since 1958. Our heaters are certified by C.S.A (a nationally recognized testing laboratory – NRTL) and carry the CSA seal. All heaters are tested and meet or exceed all safety requirements set forth in American National Standard Z83.20.


Why is a Space-Ray infrared radiant gas heater more efficient than unit heaters?

The major difference between a gas-fired infrared heating system and a forced hot air heating system is the method used to create a comfortable temperature. Infrared heats the floor slab, the machinery and the people first and then the air by using all three methods of heat transfer: radiation, conduction and convection. The storage of the heat in the slab floor creates a low temperature emitter and a faster recovery time when large overhead doors are opened and closed.

With a forced air system, the hot air rises to the ceiling and stratifies, gradually working its way down to thermostat level so that the floor slab never becomes warm enough to be comfortable. It literally acts as a heat sink, draining heat from the air and from personnel standing on the floor. The ceiling area of a high bay building using a forced air system can be easily 30° to 40° warmer than the floor area.

In the same type building heated with an infrared system, the temperature is much more uniform and the loft or roof area commonly will be at a slightly lower temperature than the floor level . . . a good condition for minimizing heat loss. Comfort can be maintained with a lower air temperature that will reduce infiltration and heat loss through the walls and roof.

In addition, instead of adding Btu/hr capacity to a computed building heat loss based on the thermal efficiency of a forced air system, the capacity is normally reduced by as much as 20%, based on the mounting height of the infrared system.

An added plus is that an infrared system has minimal power requirements, needing electricity only for burner ignition, the gas valve and the draft inducer (where applicable).

It is, therefore, easy to see that infrared commonly will save 30% to 50% in energy costs over unit heaters, frequently even more.

What is the efficiency?

First of all, there is a distinct difference between combustion efficiency and thermal efficiency. Combustion efficiency is determined by the percentage of fuel converted to usable energy given sufficient combustion air. In our tube heaters, we provide sufficient excess air to achieve complete combustion; therefore, 99.9% of all combustible constituents of fuel is converted to carbon dioxide and/or water vapor, and nitrogen (excluding trace compounds).

Thermal efficiency directly measures the flue losses based on CO2% in flue gas and flue gas temperature. For example, the LTU Series’ CO2% is 7-8.9% and the flue temperatures are below 350°F, which complies with the American National Standard. Given these two facts, the thermal efficiency of our tube heaters is 75 to 83%, depending on the model.

We feel that while thermal efficiency is a good measure for forced air heating systems, it is not the best measure for a radiant heating system. We think the best measure for a radiant system is its overall radiant efficiency. The amount of radiation received on the floor, not convective heat transfer, will determine whether it is a good radiant heater or not. The radiant efficiency of any gas infrared heater can be calculated with the following equation:

Radiant Efficiency = Radiant Output/Heat Input

Radiant Output is determined by: R=SEA (T4 – Ta4)

S= Stefan-Boltzmann Constant
E= Emissivity of Radiating Surface
A= Surface Area
T= Emitter Surface Temperature
Ta= Ambient Temperature

Our aluminized steel emitter tubes are calorized and the emissivity of these emitter tube is around 0.80 – 0.83. The emitter tube temperatures average 750°F to 800°F. With these given values, the calculated radiant coefficient (input/radiant output) of our tube heaters is around 65.2%.

How do you size infrared when replacing existing forced air unit heaters?

An infrared heating system is always sized at a lower input capacity when compared to forced air(convection) heating. This is due to different modes of heat transfer (radiation vs. convection), thermal mass and minimal stratification between ceiling and floor temperatures. For retrofit purposes, provided the unit heaters are maintaining the desired inside design temperature at ASHRAE design conditions, the following reduction can be utilized when recommending an infrared heating system.

Thermal Efficiency
% Reduction in System Sizing
High Efficiency Unit Heater
Convectional Unit Heater

Assuming that the ASHRAE heat loss for a building is 100,000 Btu/hr, then the heater selection for this building would be as follows:

Infrared Heater
Unit Heater
Building Heat Loss:
100,000 Btu/hr
100,000 Btu/hr
Infrared Compensation Factor1:
(for radiant heating)

Thermal Efficiency2:
(for convection heating)

Heater Input Required:
85,000 Btu/hr
(100,000 x 0.85)
125,000 Btu/hr
(100,000 / 0.80)

1. Infrared heat loss compensation factor based on 26′ AFF mounting height (see section C).
2. High Efficiency Unit Heater for comparison purposes.

How many square feet does a Space-Ray infrared radiant gas heater cover?

The heater model and capacity are not necessarily a function of the square footage of the area needing to be heated. The model generally is chosen after the Btu/hr heat loss for the building or spot area to be heated has been determined, which is a function of not only the size of the area, but geographic location, building materials, building usage and other factors. Area coverage could be as little as 500 sq. ft. or as much as 10,000 sq. ft.

Are there applications for which Space-Ray infrared radiant gas heaters are NOT suitable?

You may not use gas-fired infrared heaters inside paint booths or in buildings where explosion-proof lights are required. Although infrared is not ideal as an air curtain, it is very effective in spot-heating work areas inside of doorways, in dock areas and on outdoor docks.

How low can I hang my Space-Ray infrared radiant gas heaters?

Space-Ray infrared heaters have been mounted as low as 8′ above the finished floor (in home garages and workshops) to as high as 70′ (in high bay aircraft hangars). The mounting height depends on the Btu/hr capacity and model of the heater. Please refer to the heater’s specification sheet for minimum recommended mounting height and required clearances to combustible materials.

What extra items are needed for installation?

Depending on your particular application, you will want to consider the following six accessories for all series of Space-Ray infrared tube heaters:

1. Thermostat
2. Manual Cutoff Valve
3. Flexible Gas Connector
4. Second Stage Regulator if supply pressure is over 14″ W.C.
5. Vent Cap
6. Chain Kit with S hooks for hanging heater
For the ETS Series, also consider including a seventh accessory:
7. End Reflector Kit (optional, but recommended).

For the ETU Series, also consider including two additional accessories:

8. Two End Reflector Kits per heater (optional, but recommended)
9. U-Bend reflector (optional, but recommended)

For the RSCA and DK ceramic heaters, you will not need a vent cap.

How are Space-Ray infrared radiant gas heaters controlled?

Primarily, the heater is controlled by a line voltage thermostat. Alternatively, you may use a 24-volt thermostat with a relay kit or an on/off switch.

What is calorization?

Calorization is a heat-treating process used on our aluminized steel tubes that produces an alloy that can withstand higher operating temperatures than other conventional tube materials and is very absorptive of the flame on the inside of the tube and very emissive on the outside, increasing the heating efficiency. The process provides unsurpassed corrosion resistance to ferrous metal by providing a self-forming, self-healing coating of practically infusible alumina which is impervious to oxygen, carbon, sulfur and the products of combustion of natural and liquified propane gas and is, therefore, extremely corrosion resistant.


Wouldn't it be more efficient to use unvented heaters so heat wouldn't be lost out the flue?

No. The National Fuel Gas Code (NFPA54) and local codes require a minimum ventilation flow of 4 CFM per 1000 Btu/hr of heater input by either mechanical or gravity ventilation if the heaters themselves are not vented to the outside. This additional ventilation requirement increases the building heat loss and the fuel cost as indicated in this example:

Temperature Differential
(inside temp less outside design temp):
65° F
Building Heat Loss:
125,000 Btu/hr
Infrared Compensation Factor
(based on 16′ mounting height)
Infrared Heat Required:
100,000 Btu/hr

100,000 Btu/hr
100,000 Btu/hr
Additional Ventilation Required:
4 CFM per 1000 Btu/hr input = 400 CFM
Heat Loss Due to Ventilation:
0 Btu/hr

Q = CFM x 60 min/hr x TD x 0.018

400 x 60 x 65° x 0.018 = 28,080 Btu/hr

Total Input Required:
100,000 Btu/hr
128,080 Btu/hr

CONCLUSION: It will require a 28% larger capacity unvented infrared heating system to satisfy the building heat loss and comply with codes. In addition, the fuel cost of the unvented infrared heating system can be as high as 28% more than the vented infrared heating system.


What are the emission levels of Space-Ray infrared radiant gas heaters?

Air-free CO emission levels are 0.0010 – 0.0020%, or 20 to 40 times lower than the maximum acceptable level as indicated in American National Standard Z83.20. Space-Ray utilizes burners that are made of heavy duty cast iron and are designed to enhance maximum primary and secondary air flow around the venturi assembly. The high velocity of the flame and the delayed flame-quench period minimize the products of combustion which include aldehyde, formic acid, N2O, and carbon monoxide.

California Proposition 65 Warning

WARNING: This equipment, its related accessories and by-products of operation contain chemicals known to the State of California to cause cancer, birth defects and other reproductive harm.