The Basics of Gas-Fired Infrared Heating

When one thinks about building heat, the first consideration may be of the forced air variety. You know, the big unit suspended from the ceiling blowing hot air with the force of a jet engine. While that might work for some, independent reports suggest that gas-fired infrared heating can save 20% to 50% in fuel consumption over forced air heating.

By Consulting Specifying Engineer Staff August 6, 2007

By Detroit Radiant Products, Warren, Mich.

When one thinks about building heat, the first consideration may be of the forced air variety. You know, the big unit suspended from the ceiling blowing hot air with the force of a jet engine. While that might work for some, independent reports suggest that gas-fired infrared heating can save 20% to 50% in fuel consumption over forced air heating.

Low intensity gas-fired infrared heating systems emulate the true efficiency of the sun by generating radiant heat energy. They consist of three main components: a burner control box, black-coated radiant emitter tubes and a highly polished reflector assembly. The heaters are typically suspended from the ceiling by chains and controlled by a thermostat. They can be installed either vented or unvented, may use outside air for combustion if necessary and may be installed in different configurations depending on the heating requirements.

Two types of infrared heating The two types of infrared heating are high intensity and low intensity. High intensity heaters have been around since the 1950s. These heaters require high mounting heights due to an open flame that covers a ceramic surface. High intensity heaters also have a reflector to help direct the heat where it needs to go. These are used to spot heat areas with few workers and are typically unvented.

Low intensity heaters have an enclosed flame.flectors. This energy is absorbed by objects in its path, such as the floor, machinery and people. These objects, in turn, re-radiate the heat to create a comfort zone at the floor level. This method of heating, as opposed to filling a room with warm air, allows the source of heat to begin at the floor level and not the ceiling.

With a forced air system, heat escapes as doors are opened. When the doors close, the system will have to reheat the air as if from a cold start up. However, with infrared heat the floor acts as a reservoir. When doors are opened, the slab loses very little of its heat, and when the doors close, this mass acts as a huge heat sink to warm the surrounding air. This creates the most efficient and effective heating method under the diverse conditions present in commercial and industrial applications.

Positives of infrared Radiant heaters offer several operational and design benefits not available with conventional heating units. For example:

Can save up to 50% fuel savings over forced air units.

Does not blow dust and debris around like heaters that rely on blowers for heat distribution. This makes for a much cleaner and quieter environment.

Zoned capability allows a group of units to function together or independently.

Capable of mounting heights up to 60 feet depending on which heater is chosen for that application.

Spot heat to certain areas where workers are few.

Directional. It is capable of being installed along a sidewall and the reflectors can be rotated to direct heat where it is most needed.

Can use outside air for combustion.

Low intensity heaters can be vented together to reduce the number of roof or wall penetrations.

Design is flexible. Heater placement can be in the middle of the shop or perhaps even in a “U” or “L” shaped configuration around a workstation where the heat is needed most.

Negatives of infrared There are a few important things to consider when using radiant heat. While they are easy to live with, care needs to be taken when laying out the system to maintain clearances to combustibles. Infrared radiant heaters require higher clearances than forced air units. Therefore, a mounting height of 10 ft. or higher is recommended depending on the application and the model.

Very little maintenance is required especially when bringing in outside air for combustion. This is recommended when dust or contamination that is present inside the building. Periodic dusting of the reflectors is beneficial; not only for safety, but for the overall efficiency of the heater. This is easily done by vacuuming the surfaces of the unit occasionally or blowing it off with an air-compressor hose.

Safety considerations A critical safety factor to consider before installing an infra-red heating system is clearances to combustibles. Clearance to combustibles is defined as the minimum distance that must be maintained between the radiant tube heater surface and the combustible item. Considerations must also be made for moving objects around the infra-red heater and materials that have lower temperature ratings, such as plastics.

It is important to provide warnings to alert individuals to potential hazards and safety actions. Signs must be posted to specify maximum stacking heights in order to maintain clearances to combustibles, especially in storage areas.

Additional examples of combustibles include; lights, overhead doors, gas and electrical lines, parked vehicles, cranes, and any other obstructions or hazards.

Unless otherwise indicated, infrared heaters are not certified for residential use or where flammable gasses or vapors are present, such as spray booths.

In addition, observing recommended mounting heights will optimize comfort conditions in the space. If infrared heaters are mounted too high or too low, they may result in a lack of heat or discomfort.

New technology An advanced feature of low intensity infrared tube heaters is the use of two stage controls. A two-stage infrared heater is characterized by its ability to operate in pre-set “high” and “low” fire 35% (100% input in high fire and 65% input in low fire). Field reports as well as studies performed by RDM Engineering of Ontario, Canada have proven a minimum fuel savings of 12% and a reduction of on/off cycles up to 30% with the majority of heater operation in low fire. A two stage heater allows application design flexibility based upon the possible worse case changes in the environment.

In addition to fuel savings, reduced on/off cycles and design flexibility, additional benefits of two-stage heaters include faster heat recovery, higher downstream tube temperatures, longer flame and longer equipment life.

Vacuum style Multiple burner, low intensity, vacuum infrared heating systems have been a part of the main stream product offering in infrared heating systems for many years. In fact, the technology is over 40 years old. As the infrared heating industry has evolved through the development of unitary heaters featuring equal or superior energy efficiency, multiple burner low intensity vacuum infrared heating systems have often been seen as old technology.em offers some application benefits not found with other types of infra-red equipment.

Vacuum style infrared heaters may have up to six burners common vented by a single vacuum pump. Fewer roof or sidewall penetrations are the resulting application benefit. The vacuum style may be installed as a condensing or non-condensing system. A condensing system allows for longer system lengths and higher system thermal efficiency. A non-condensing system more efficiently utilizes the highly emissive black coating on the radiant tubes at a more reasonable equipment cost over the condensing system.

If you are one to count pennies you might want to stay with the forced air method. But, if you can live with a small investment, radiant heating might be a wise choice.for itself over a short period of time due to the energy saving benefits of radiant heaters. Interested in even more fuel savings? Install a system that incorporates two stage technology can offer an additional 12% fuel savings over a standard single stage radiant heater. 

Although the installation may be fairly easy, system design and layout can be more difficult. It is critical that the equipment is installed properly to assure a safe and effective heating system. Most manufacturers sell product via local manufacturer’s representatives.