phvac Dec 2006.qxd - Plumbing & HVAC

Heating
Going green with infrared
Energy savings potential largely overlooked
By Simon Blake
Like the late comedian Rodney
Dangerfield, the infrared heating
industry can’t get any respect.
Despite offering equipment touted to
achieve significant energy savings in
warehouse and industrial heating applications,
it has been largely overlooked
in the move to “green” heating
technologies.
“There has been an oversight, particularly
in LEED projects and just generally…
That’s something manufacturers
are trying to address,” says Bob Alcott,
product and marketing manager for
Schwank Ltd., Mississauga, Ont. “We’re
doing everything we can in our marketing
and promotional efforts to inform
people that infrared is an energy use
reduction product...” Rebate programs,
with the exception of a few gas utility
initiatives, tend to ignore infrared
heating too.
And yet some research has put the
energy savings with natural gas-fired
infrared heaters over unit heaters at
about 30 percent for a typical warehouse
or industrial building, allowing
the infrared heater to be sized for considerably
less input than the equivalent
unit heater.
In retrofit applications, the difference
can be as much as 50 percent versus
older unit heaters, says Bob Genisol,
vice president of sales and marketing
for Space-Ray, Charlotte, N.C.
“When comparing heating appliances
that use different modes of heat transfer
to heat a space, it ultimately boils down
to the comfort of the occupants and how
much energy (fuel and electricity) it takes
to reach that comfort level,” remarked
Patrick Stone, director of North Ameri -
can sales for Roberts-Gordon, located in
Buffalo, N.Y. “In many commercial and
industrial buildings, infrared heating can
achieve equal or better comfort levels
while using much less fuel and electricity
than (forced) air heating.”
Difficult to rate
But there’s a problem – infrared is a
combination of radiant and convective
heat. “When you do a building analysis,
you don’t break the two apart,” says
Dave Mackenzie, vice president of Brant
Radiant Heaters Ltd. in Paris, Ont. This
makes it difficult to come up with a
number that makes sense from an energy
efficiency standpoint like the AFUE
number used to rate forced air systems.
“There’s really no standard to qualify
its radiant output and, if there was,
“There are people out there
that will lead you to believe that
all 40-foot tube heaters are the
same, and they really are not.”
This truck repair facility is a good example of the type of application where tube-type infrared heaters make a lot of sense.
there’s not a lot of information out
there that relates the radiant output (of
the appliance) to the heating of the
building.”
In fact manufacturers like Brant
Radiant, which manufactures the Re-
Verber-Ray line, end up doing their own
research and providing their own
figures.
“The only way that made sense for us
to do research was in real world buildings,”
he says. That involved heating the
space with unit heaters and then removing
them and installing infrared and
then comparing the results. The tests
primarily looked at fuel utilization for
the entire building, as opposed to that
for each individual heater.
Not the same
Tube-type infrared heaters come in a
number of configurations and are constructed
of different materials. Getting
these factors right is key in achieving the
best long-term efficiency and comfort.
“(Contractors) should do their
home work,” says McKenzie. “They
should look at what the units are made
of, what they are getting, make sure they
get information. There are people out
there that will lead you to believe that
all 40-foot tube heaters are the same,
and they really are not.”
Unitary infrared heaters consist of
single burners with a single length of
tube and reflector, in straight, L or U
designs. A U-tube configuration can
result in a more uniform heat distribution,
particularly when only one heater
is installed.
Multi-burner infrared systems
typically consist of multiple unitary
heaters connected to an exhaust manifold,
allowing a common combustion
blower or vacuum pump and a single
common vent.
Burners-in-series infrared systems
use multiple infrared heaters in a custom-shaped
system. The burners are
arranged with one after another in a
row to fire into a common tube and
reflector system. “These systems are able
to maintain radiant tube temperatures
along a long length, allowing for the
most even heating,” said Stone.
Typically, burners-in-series systems
are designed to condense as temperatures
are lower. Less usable heat is wasted
through the exhaust vent, thus higher
combustion efficiency is achieved. All
burners in the system share a common
vacuum pump for combustion air supply
and venting. Burners can be singlestage,
dual stage or modulating.
The type of construction of an
infrared heater makes a significant difference
in long-term efficiency.
There are a number of different
materials used to make the heat
exchangers in tube-type infrared heat -
ers. The most common construction is
cold rolled steel. Its emissivity, or heat
transfer efficiency, is about 66 percent.
On the other hand, aluminized heattreated
steel emitters have a heat transfer
efficiency of 80 to 86 percent. There
are also stainless steel and even titanium
tubes. The difference may not be that
great when the heaters are new. But a
common steel tube rusts inside and the
efficiency drops off while a stainless
14 Plumbing & HVAC Product News – April 2009 www.plumbingandhvac.ca