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 When we think about building heat, our 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 reveal that gas fired infrared heating can save 20 to 50
percent 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 (3) 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 1950’s. These
types of 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.
The other type of
infrared heating is called Low Intensity. These heaters have an enclosed flame. When heat is required, the burner control box ignites a gas/air mixture
and hot gases are pushed through steel radiant tubing by an internal fan. As these gases pass through the assembly, the
tubing is heated and emits infrared energy, which is then directed toward the
floor by highly polished reflectors. This energy is absorbed by objects in its path, such as the floor,
machinery and people. Objects in the
path of the infrared energy in turn re-radiate this 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 looses 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 most commercial and industrial applications.
The positives of infrared heating
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.
The negatives of infrared heating
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’ 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 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 infrared
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 infrared heater and materials that have lower temperature
ratings, such as plastics. Shielding of
these items may be necessary.
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. However, certain
applications such as freeze protection, outdoor patio heating, or spot heating
may require the heaters to be mounted at other than the traditional recommended
mounting heights.
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 modes. Since infrared
heating systems are typically designed around “worse case scenarios” (which
only occur 10-20 percent of the time) a single stage system becomes oversized
on milder days creating more on/off cycles (heat/no heat). With two stage technology, input (fuel usage)
is reduced by 35 percent (100 percent input in high fire and 65 percent 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 percent and a
reduction of on/off cycles up to 30 percent 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. More importantly, a two
stage heater will provide a softer and more comfortable heat source for
occupants when compared to a single stage heater which is either operating at
full output (sometimes too much heat) or cycles off (not enough heat).
Vacuum style of infrared heating
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. The
main difference between a vacuum style heater and a positive pressure tube
heater is that now the burner box is under a negative pressure instead of a
positive pressure. There is a pump
located at the end of the system which pulls the gases down the tube. This type of infrared heating system offers
some application benefits not found with other types of infrared equipment.
Benefits of vacuum style infrared heating
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.
The price of staying warm
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. Gas line connections must be considered and hanging the unit is at least
a two-person job. The initial cost of a
standard, unitary tube heater of forty feet long will run approximately
$1100. Therefore, upfront costs are
higher than traditional heating methods. However, this investment will pay 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.
Distribution
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. This allows a professional to review the
desired needs and select the proper equipment for a specific application. A local representative may also provide
guidance in suggesting a contractor familiar with installing infra-red heating
systems.
Possible applications
Here are some typical applications where
infrared heating works well.
· Harsh Environments
· Fire Stations
· Aircraft Hangars
· Wood Shops or Pole Barns
· Car Washes
· Auto Shops
· Restaurants
· Agricultural Buildings
· Driving Ranges
· Warehouses
· Home Garages
· Manufacturing Buildings
Summary
In the end, it comes down to whether you wish
to provide a good heat source in your application. Gas fired infrared heaters offer the option
of placing heat where and when it is needed. This ability coupled with excellent operating costs, gives a clear
advantage to infrared heaters. And if
you want to get the most for your money go with heaters equipped with two stage
technology. You can rest assured that
providing a comfortable environment within your application will be well
received by both you and other building occupants.
Source: Detroit Radiant Products Company |
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