Page 9
Furnaces may be installed in either an attic or a crawlspace.
See figure 10 for furnace installations on a platform.
NOTE - When the furnace is installed on a platform in a
crawlspace, it must be elevated enough to avoid water
damage and to allow the air conditioning coil to drain.
Horizontal Application
Unit Installed on Platform
GAS
ENTRY
VENT
PIPE
NOTE - Line contact is permissible. See the unit rating plate for clearances
NON-COMBUSTIBLE
WORKING PLATFORM
NON-COMBUSTIBLE
UNIT PLATFORM
FIGURE 10
Anyone of the following methods may be used to suspend
the furnace from roof rafters or floor joists:
1 - Using Lennox hanging bracket kit catalog number
46J66 -
Install as indicated in the installation instructions
provided with the hanging bracket kit.
2 - Using angle iron with at least 1/4 in. diameter rods -
Install as shown in figure 11.
Note - Rods must not interfere with plenum or exĆ
haust piping;
cooling coils and supply and return
air plenums must be supported separately.
Horizontal Application
Unit Suspended in Attic or Crawlspace
Using Angle Iron and Rods
1/4 in. ROD
ANGLE
IRON
SUPPORT TIES -
INSTALL TO PREVENT
SPREADING
Leave sufficient clearance between rod and unit to
remove access panels.
Level unit - side to side and end to end.
Secure the angle iron to the unit with sheetmetal screws:
maximum screw length - 3/4 in. and minimum screw size - # 10.
FIGURE 11
WARNING
Improper installation of unit can result in personal
injury or death. Flue gases must never be allowed
to enter the return air system or the living space.
Sheet metal screws and sealing tape should be
used to seal ducting to the furnace. In platform
installations, return air must always be ducted to
the unit. A unit must never be installed so that it
draws return air from the furnace chamber, attic or
underfloor space. The furnace platform must be
level with no sagging, cracks or gaps.
Furnaces must always be isolated from other heatĆ
ing appliances to prevent fire, explosion, and carĆ
bon monoxide poisoning. Personal injury and/or
property damage could result..
Duct System
Use industryĆapproved standards to size and install the
supply and return air duct system. This will result in a quiet
and lowĆstatic system that has uniform air distribution.
SUPPLY AIR PLENUM
Furnaces installed without a cooling coil require the installaĆ
tion of a removable access panel in the supply air duct. The
access panel should be large enough to permit inspection
(either by smoke or reflected light) of the heat exchanger for
leaks after installation . The furnace access panel must alĆ
ways be in place when the furnace is operating and it must
not allow leaks into the supply air duct system.
RETURN AIR PLENUM
Return air must not be drawn from a room where
this furnace, or any other gas appliance (ie., a water
heater), is installed.
When return air is drawn from a
room, a negative pressure is created in the room. If a
gas appliance is operating in a room with negative presĆ
sure, the flue products can be pulled back down the vent
pipe and into the room. This reverse flow of the flue gas
may result in incomplete combustion and the formation
of carbon monoxide gas. This toxic gas might then be
distributed throughout the house by the furnace duct
system.
In upflow applications, return air can be brought in
through the bottom or either side of the furnace. If a furĆ
nace with bottom return air is installed on a platform,
make an airtight seal between the bottom of the furnace
and the platform to ensure proper and safe operation.
Use fiberglass sealing strips between the plenum and the
furnace cabinet to ensure a tight seal. If a filter is installed,
size the return air duct to fit the filter frame.
