Venting - Lennox ML180UHA Installation Instructions Manual

Venting

The ML180UHA is a fan assisted furnace equipped with an
integral mechanical means to either draw or force products
of combustion through the combustion chamber and/or
heat exchanger. When installed in the vertical position and
vented vertically, the furnace operates with a non-positive
vent stack pressure. When installed in the horizontal posi­
tion and vented vertically, the furnace operates with a posi­
tive stack pressure.
IMPORTANT
The ML180UH is certified for horizontal installation
but DO NOT vent flue horizontally. The ML180UH fur­
nace is not certified for horizontal venting. See figure
21.
General Venting Requirements
A 102 mm (4 in.) diameter flue transition is factory‐installed
on the combustion air inducer outlet of all models. Figure
14 shows the combustion air inducer as shipped from
the factory. Refer to the current edition of the Australian
Gas Installation Code (AS/NZS5601) and instructions in
this manual for proper sizing an installation of the venting
system
When flues are terminated vertically, an AGA approved
cowl must be used.
Mounting Screws Location
Flue Transition
FIGURE 13
If necessary, reposition the combustion air inducer, pres­
sure switch and/or make-up box as needed per the follow­
ing steps. See figures 14 through 20.
1 - Remove the four mounting screws (figure 13) which
secure the combustion air inducer / pressure switch
assembly to the orifice plate. Lift the inducer assembly
and rotate it 90 degrees clockwise or counterclockwise
to either the 3 o'clock position or to 9 o'clock position.
Re-secure with four screws. Gasket should be left in
place.
Mounting Screws
Page 12
2 - Use tin snips to cut preferred opening on the cabinet
for repositioning the flue outlet. Use the cut-out piece
as a cover plate to patch unused opening on cabinet.
Upflow Position
UPFLOW POSITION
Top Vent Discharge
Flue
Transition
Pressure
Switch
AIR
FIGURE 14
IMPORTANT
The unit will not vent properly with the flue transition
pointed down in the 6 o'clock position.
The combustion air inducer may be rotated clock­
wise or counterclockwise by 90° to allow for top or
side vent discharge in all applications. When the unit
is installed, the flue transition must be in the 9
o'clock, 12 o'clock or 3 o'clock position.
UPFLOW POSITION
Left Side Vent Discharge
Pressure
Switch
Vent Pipe
Flue
Transition
AIR
D Gas supply piping must be brought into the unit from the right
side in order to accommodate the flue pipe.
D Cut combustion air inducer tubing from 229 mm (9") to 203 mm
(8") to avoid interference with inducer motor
FIGURE 15
Vent Pipe
Collector Box
FLOW
Collector Box
FLOW