Lennox SL280UHNV - Combustion, Dilution & Ventilation Air

Page 6
Combustion, Dilution & Ventilation Air
In the past, there was no problem in bringing in su󰀩cient
outdoor air for combustion. Inltration provided all the air
that was needed. In today’s homes, tight construction
practices make it necessary to bring in air from outside for
combustion. Take into account that exhaust fans, appli-
ance vents, chimneys, and replaces force additional air
that could be used for combustion out of the house. Un-
less outside air is brought into the house for combustion,
negative pressure (outside pressure is greater than inside
pressure) will build to the point that a downdraft can oc-
cur in the furnace vent pipe or chimney. As a result, com-
bustion gases enter the living space creating a potentially
dangerous situation.
In the absence of local codes concerning air for combus-
tion and ventilation, use the guidelines and procedures in
this section to install SL280UHNV furnaces to ensure ef-
cient and safe operation. You must consider combustion
air needs and requirements for exhaust vents and gas
piping. A portion of this information has been reprinted
with permission from the National Fuel Gas Code (AN-
SI-Z223.1). This reprinted material is not the complete
and o󰀩cial position of the ANSI on the referenced subject,
which is represented only by the standard in its entirety.
CAUTION
Insu󰀩cient combustion air can cause headaches,
nausea, dizziness or asphyxiation. It will also cause
excess water in the heat exchanger resulting in rusting
and premature heat exchanger failure. Excessive
exposure to contaminated combustion air will result
in safety and performance related problems. Avoid
exposure to the following substances in the combustion
air supply:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine base swimming pool chemicals
Water softening chemicals
De-icing salts or chemicals
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
CAUTION
Do not install the furnace in a corrosive or contaminated
atmosphere. Meet all combustion and ventilation air
requirements, as well as all local codes.
All gas-red appliances require air for the combustion
process. If su󰀩cient combustion air is not available, the
furnace or other appliances will operate ine󰀩ciently and
unsafely. Enough air must be provided to meet the needs
of all fuel-burning appliances and appliances such as ex-
haust fans which force air out of the house. When replac-
es, exhaust fans, or clothes dryers are used at the same
time as the furnace, much more air is necessary to ensure
proper combustion and to prevent a downdraft. Insu󰀩cient
air causes incomplete combustion which can result in car-
bon monoxide.
In addition to providing combustion air, fresh outdoor air
dilutes contaminants in the indoor air. These contaminants
may include bleaches, adhesives, detergents, solvents
and other contaminants which can corrode furnace com-
ponents.
The requirements for providing air for combustion and
ventilation depend largely on whether the furnace is in-
stalled in an unconned or a conned space.