Installation guide
INSTALLATION INSTRUCTIONS Gas Furnace: (F/G)9MXT, (F/G)9MXE
10 440 01 4005 05
Specifications subject to change without notice.
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death and/or property damage.
Do not install the furnace on its back or hang furnace with con-
trol compartment facing downward. Safety control operation will
be adversely affected. Never connect return−air ducts to the
back of the furnace. (See Figure 5)
Figure 5 Prohibit Installations
BACK POSITIONED
DOWNWARD
AIR
RETURN
CUT IN
BACK
BACK POSITIONED
UPWARD
L12F011
Location Relative to Cooling
Equipment
The cooling coil must be installed parallel with, or on the
downstream side of the unit to avoid condensation in the heat
exchangers. When installed parallel with the furnace, dampers
or other flow control must prevent chilled air from entering the
furnace. If the dampers are manually operated, they must be
equipped with means to prevent operation of either unit unless
the damper is in the full−heat or full−cool position.
Air for Combustion and
Ventilation
Introduction
Direct Vent (2−pipe) Applications
When the furnace is installed as a direct vent (2-pipe) furnace,
no special provisions for air for combustion are required.
However, other gas appliances installed in the space with the
furnace may require outside air for combustion. Follow the
guidelines below to insure that other gas appliances have
sufficient air for combustion.
Non−Direct Vent (1−pipe) Applications
When the furnace is installed as a non-direct vent (1-pipe)
furnace, it will be necessary to insure there is adequate air for
combustion. Other gas appliances installed with the furnace
may also require air for combustion and ventilation in addition
to the amount of combustion air and ventilation air required for
the furnace. Follow the guidelines below to insure that the
furnace and other gas appliances have sufficient air for
combustion.
Ventilated Combustion Air Applications
When the furnace is installed using the ventilated combustion
air option, the attic or crawlspace must freely communicate with
the outdoor to provide sufficient air for combustion. The
combustion air pipe cannot be terminated in attics or
crawlspaces that use ventilation fans designed to operate
during the heating season. If ventilation fans are present in
these areas, the combustion air pipe must terminate outdoors
as a Direct Vent/ 2-Pipe system.
All air for combustion is piped directly to the furnace from a
space that is well ventilated with outdoor air (such as an attic,
crawlspace, or equipment closet) and the space is well isolated
from the living space or garage. In addition, other gas
appliances installed in the space with the furnace may require
outside air for combustion. Follow the guidelines below to
insure that the roof or crawlspace walls have sufficient free
area to provide sufficient air for combustion and ventilation for
the furnaces. The guidelines below can be used to insure that
other gas appliances have sufficient air for combustion.
Provisions for adequate combustion, ventilation, and dilution air
must be provided in accordance with:
U.S. Installations: Current edition of Section 9.3 of the
NFPA 54/ANSI Z223.1, Air for Combustion and Ventilation
and applicable provisions of the local building codes.
Canadian Installations: Current edition of Part 8 of
CAN/CSA−B149.1, Venting Systems and Air Supply for
Appliances and all authorities having jurisdiction.
CAUTION
!
FURNACE CORROSION HAZARD
Failure to follow this caution may result in furnace damage.
Air for combustion must not be contaminated by halogen
compounds, which include fluoride, chloride, bromide, and
iodide. These elements can corrode heat exchangers and
shorten furnace life. Air contaminants are found in aerosol
sprays, detergents, bleaches, cleaning solvents, salts, air
fresheners, and other household products.
WARNING
!
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal injury or
death.
The operation of exhaust fans, kitchen ventilation fans,
clothes dryers, attic exhaust fans or fireplaces could create a
NEGATIVE PRESSURE CONDITION at the furnace.
Make−up air MUST be provided for the ventilation devices, in
addition to that required by the furnace. Refer to the Carbon
Monoxide Poisoning Hazard warning in the venting section of
these instructions to determine if an adequate amount of
make−up air is available.
The requirements for combustion and ventilation air depend
upon whether or not the furnace is located in a space having a
volume of at least 50 cubic feet per 1,000 Btuh (4.8 cubic
meters per kW) input rating for all gas appliances installed in
the space.
Spaces having less than 50 cubic feet per 1,000 Btuh (4.8
cubic meters per kW) require the OUTDOOR
COMBUSTION AIR METHOD.
Spaces having at least 50 cubic feet per 1,000 Btuh (4.8
cubic meters per kW) may use the INDOOR
COMBUSTION AIR, STANDARD or KNOWN AIR
INFILTRATION METHOD.