Filter Assembly And Filters; Duct System; Exhaust, Intake & Condensate Piping - Lennox G21Q Series Installation Instructions Manual

Bottom Return Air Opening
1 - - Cut opening in floor or platform.
2 - - Flange return air plenum and lower into opening.
3 - - Place glass fiber insulation strips around opening.
Position isolation mounting pads at corners of insu-
lation. Insulation should not overlap the mounting
pads. Trim away any excess insulation from strips.
4 - - Set unit. Make sure unit is sitting on isolation pads.
NOTE - - Be careful not to damage insulation. Check
for tight seal.

FILTER ASSEMBLY AND FILTERS

G21 series units are equipped with a reusable foam fil-
ter. Filter must be in place any time unit is in operation.
For bottom return air opening applications, install filter
mounting clips provided and secure with sheet metal
screws.
For side return air openings, use U- -channel on blower
deck and supplied filter rack to install filter. To install fil-
ter rack, remove two screws from side of cabinet. Place
flange of filter rack inside bottom panel and side panel.
Secure with previously removed cabinet/base bottom
screws. See figure 4.
FILTER RACK FOR G21Q
(Used on side return only)
U- -CHANNELS
FIGURE 4

DUCT SYSTEM

1 - - Install flexible canvas boots or equivalent on both
supply and return air plenums. Boots should be
placed as close as possible to unit.
2 - - Insulate supply air plenum and duct system at least
through the first elbow. Use 1- -1/2 to 3 lb. (24 to 48
kg) density, matt face, 1” (25mm) thick insulation.
Provisions must be made to keep insulation in place
and to protect edges from airflow deterioration.
3 - - Size and install supply and return system using in-
dustry- -approved standards that result in a quiet
and low- -static system with uniform distribution.
Installation of units not equipped with a cooling coil re-
quire a removable access panel in the supply air duct.
SIDE
PANEL
FILTER
FILTER
RACK
BOTTOM
BASE
The access panel should be large enough to permit in-
spection of heat exchanger for leaks after installation
(either by smoke or reflected light). The access panel
must not allow leaks in the supply air duct system.
The return air must not be drawn from a room where
another gas appliance (i.e., a water heater) is installed.
Even though this furnace draws its combustion air
from outside of the structure, other gas appliances that
share a utility room may not. 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 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 combus-
tion and the formation of carbon monoxide gas. This
toxic gas might then be distributed through the house
by the furnace duct system.
EXHAUST, INTAKE & CONDENSATE PIPING
A - - Exhaust and Intake Piping Requirements
For U.S. installation, venting requirements must comply
with the current AGA/GAMA standards. For Canadian
installation, the venting system must comply with cur-
rent ULC standard for type BH gas vents No. S636. Fur-
nace shall not be connected to any type B, BW or L vent
or vent connector and shall not be connected to any
portion of a factory built or masonry chimney.
Two mufflers (one each in the exhaust and intake piping)
are required and furnished for use with the G21- -80/100
units. See table 2 for optional usage of mufflers with G21
units. Mufflers should be located and installed as di-
rected in instructions packaged with muffler kit.
Exhaust piping muffler(s) installed horizontally in
unconditioned spaces must be protected by self- -
regulating heating cable and insulation.
MODEL NO. EXHAUST MUFFLER
G21Q- -40/60
G21Q- -80/100
2(additional option)
All PVC pipe, fittings, primer and solvent cement must
conform with American National Standard Institute and
the American Society for Testing and Materials (ANSI/
ASTM) standards. Refer to table 3 for approved piping
and fitting materials. The solvent shall be free flowing
and contain no lumps, undissolved particles or any for-
eign matter that adversely affects the joint strength or
chemical resistance of the cement. The cement shall
show no gelation, stratification, or separation that can-
not be removed by stirring.
3DJH 
IMPORTANT
TABLE 2
INTAKE MUFFLER
1(optional) 1(optional)
1(required) 1(required)
2(additional option)