Page 12
Duct
Use industry-approved standards (such as those pub-
lished by Air Conditioning Contractors of America or Amer-
ican Society of Heating, Refrigerating and Air Condition-
ing Engineers) to size and install the supply and return
air duct system. This will result in a quiet and low-static
system that has uniform air distribution.
NOTE - Do not operate the furnace in the heating mode
with an external static pressure that exceeds 0.5 inches
w.c. Higher external static pressures may cause erratic
limit operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a remov-
able access panel must be installed in the supply air duct.
The access panel should be large enough to permit in-
spection (either by smoke or reected light) of the heat
exchanger for leaks after the furnace is installed. The
furnace access panel must always be in place when the
furnace is operating and it must not allow leaks into the
supply air duct system.
Return Air Plenum
NOTE - Return air must not be drawn from a roomwhere
this furnace, or any other gas-fueled appliance (i.e., water
heater), or carbon monoxide producing device (i.e., wood
replace) 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 pressure, the ue products can be
pulled back down the vent pipe and into the room. This
reverse ow of the ue gas may result in incomplete com-
bustion and the formation of carbon monoxide gas. This
toxic gas might then be distributed throughout the house
by the furnace duct system.
In upow applications, the return air can be brought in
through the bottom or either side of the furnace. If a fur-
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 that the unit operates properly and
safely. Use berglass sealing strips, caulking, or equiva-
lent sealing method between the plenum and the furnace
cabinet to ensure a tight seal. If a lter is installed, size the
return air duct to t the lter frame.
To Next Page
Loading...
