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•
Do not install the furnace where drafts might blow
directly into it. This could cause improper combus-
tion and unsafe operation.
•
Do not block the furnace combustion air openings
with clothing, boxes, doors, etc. Air is needed for
proper combustion and safe unit operation.
•
When the furnace is installed in an attic or other
insulated space, keep insulation away from the fur-
nace.
NOTE - The Commonwealth of Massachusetts
stipulates these additional requirements:
•
Gas furnaces shall be installed by a licensed
plumber or fitter only.
•
The gas cock must be "T handle" type.
•
When a furnace is installed in an attic, the pas-
sageway to and service area surrounding the
equipment shall be floored.
Combustion, Dilution & Ventilation Air
In the past, there was no problem in bringing in sufficient
outdoor air for combustion. Infiltration 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 fireplaces 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 ML180UHE furnaces to ensure effi-
cient and safe operation. You must consider combustion
air needs and requirements for exhaust vents. A portion of
this information has been reprinted with permission from
the National Fuel Gas Code (ANSI-Z223.1). This reprint-
ed material is not the complete and official position of the
ANSI on the referenced subject, which is represented only
by the standard in its entirety.
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.
Insufficient 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
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
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 unconfined or a confined space
Unconfined Space
An unconfined space is an area such as a basement or
large equipment room with a volume greater than 50 cubic
feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the com-
bined input rating of all appliances installed in that space.
This space also includes adjacent rooms which are not
separated by a door. Though an area may appear to be
unconfined, it might be necessary to bring in outdoor air
for combustion if the structure does not provide enough air
by infiltration. If the furnace is located in a building of tight
construction with weather stripping and caulking around
the windows and doors, follow the procedures in the air
from outside section.
Page 5
CAUTION
exposure
to
the
following
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