by Claudia Lawrence
InterNACHI contributing author
Executive Director, TWI Systems
Only about 30% of a home's heating system is reviewed by the local gas provider
if they are called out for a seasonal start-up. This leaves 70% of the review
of the heating system to the homeowner or possibly to untrained personnel.
Heater venting systems are a major concern every winter in every part of the
country. During earthquakes, like the ones in Southern California, vent systems
can become separated, especially the horizontal connector pipes associated with
floor furnaces, allowing the potential for fire, or fumes to escape in unwanted
areas possibly resulting in illness, fire or even death.
Floor furnaces can be dirty, prohibiting combustion air needed to allow for proper
flame causing soot and the potential for aldehydes and allowing CO into the home.
If the property you are considering has a floor furnace be sure to ask the home
inspector to fully review the vent system under the house.
Forced air heating units atop roofs may have loose or leaking gas lines A homeowner
may not realize there is a problem even though there may be higher gas bills.
Roof mounted units may have damaged supports or other related problems.
Forced air heating units mounted in closets can be another potential for problems.
Units today are required to be secured and mounted over the return air hole and
tightly sealed. If not properly placed and caulked this will interfere with the
flow of natural combustion air affecting the flame and cause venting gases, or
carbon monoxide, to flow into the home via the ducts. Some closets furnaces were
found to have shifted up to four inches off the return air hole after the Southern
California earthquakes. Heater compartment (or closet) doors need to be sealed
and should latch tightly if the return air register is within 10 feet of the door.
Upper and lower combustion air openings located inside the closet should be clear
of debris and obstructions, allowing combustion air to flow. Obstructions such
as insulation can inhibit proper air flow causing the heater to burn improperly.
Missing fire blocks below the lower combustion air vents can allow the venting
process to reverse causing , again, the heater to burn improperly and vent gases
and aldehydes into the home through the ducting system.
Wall furnaces have a high potential for cracks in the heat exchangers. Ask your
home inspector to review closely with a mirror and flashlight. The home inspector
cannot always see a crack in a heat exchanger but may be able to locate those
that are visible or suspect. The unit may need to be cleaned before lighting the
pilot. You may also wish to ask the home inspector to review carefully the venting
system in the attic crawl spaces when the inspector checks this area.
Watch out for the home which has been occupied by the same owner for years. The
heating system may not meet today's safety standards and would typically, after
and inspection by the gas supplier, be "red-tagged" until replaced or repaired.
This could be uncomfortable for a new homeowner if the weather is extremely cold
and the repair cost is out-of-pocket.
The Gas Company or provider usually offer a no-charge safety inspection to their
customers. It is highly recommended to have this performed regardless if you had
the home inspected. A diligent inspection of the heating system, venting system,
and a careful review of heat exchangers can possibly save a life or prevent loss
by fire.
