Lennox EL180UHE - Venting Basics

Page 12
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 upow 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.
Venting
A 4-inch diameter ue transition is factory-installed on
the combustion air inducer outlet of all models. Figure 15
shows the combustion air inducer as shipped from the fac-
tory.
Mounting Screws Location
Mounting Screws
Flue Transition
Figure 14
UPFLOW POSITION
Top Vent Discharge
FLOW
AIR
Collector Box
Vent Pipe
Flue
Transition
Pressure
Switch
Make-Up
Box
Figure 15
IMPORTANT
The unit will not vent properly with the ue transition
pointed down in the 6 o’clock position. The
combustion air inducer may be rotated clockwise or
counterclockwise by 90° to allow for top or side vent
discharge in all applications. When the unit is installed,
the ue transition must be in the 9 o’clock, 12 o’clock or
3 o’clock position.
If necessary, reposition the combustion air inducer, pres-
sure switch and/or make-up box as needed per the follow-
ing steps. See gures 16 through 20.
1 - Remove the four mounting screws (gure 14) which
secure the combustion air inducer / pressure switch
assembly to the orice plate. Lift the assembly and
rotate it 90 degrees clockwise or counterclockwise
to either the 3 o’clock position or to 9 o’clock
position. Resecure with four screws. Gasket should
be left in place.
2 - Use tin snips to cut preferred opening on the
cabinet for repositioning the ue outlet. Use the cut-
out piece as a cover plate to patch unused opening
on cabinet.