Lennox G26 series Installation Instructions Manual page 7

Useindustry-approved standards to sizeandinstall t he
supply andreturn airductsystem. Thiswillresult i na quiet
and
low-static system that has uniform air distribution.
Supply Air Plenum
Furnaces installed without a cooling coil require the installa-
tion of a removable access panel in the supply air duct. The
access panel should be large enough to permit inspection (ei-
ther by smoke or reflected light) of the heat exchanger for
leaks after installation. The furnace access panel must al-
ways be in place when the furnace is operating and it must
not allow leaks into the supply air duct system.
Return Air Plenum
See dimension illustration on page 2 for proper return air
duct size.
NOTE - For bottom return air, return air duct should be se-
cured to the unit using rivets or S-locks. For side return air,
secure return air duct to filter rack using screws. When us-
ing screws, take care to avoid interference with the filter
which may cause improper filtration.
The return air must not be drawn from a room where
another gas appliance (ie., 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 ap-
pliance 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 combustion and the formation of carbon mon-
oxide gas. This toxic gas might then be distributedthrough
the house by the furnace duct system.
I A CAUTION I
All pipe, fittings, primer and solvent cement must con-
form with American National Standard Institute and the
American Society for Testing and Materials (ANSI/
ASTM) standards. The solvent shall be free flowing and
contain no lumps, undissolved particles or any foreign
matter that adversely affects the joint strength or chemi-
cal resistance of the cement. The cement shall show no
gelation, stratification, or separation that cannot be re-
moved by stirring. Refer to the table 2 below for approved
piping and fitting materials.
TABLE 2
PIPING AND FITTINGS SPECIFICATIONS
PIPE & FITTING MATERIAL
Schedule 40 PVC (Pipe)
Schedule 40 PVC (Cellular Core Pipe)
Schedule 40 PVC (Fittings)
Schedule 40 CPVC (Pipe)
Schedule 40 CPVC (Fittings)
SDR-21 PVC (Pipe) or SDR-26 PVC (Pipe)
SDR-21 CPVC (Pipe) or SDR-26 CPVC (Pipe)
Schedule 40 ABS (Pipe)
Schedule 40 ABS (Fittings)
ABS-DWV (Drain Waste & Vent)
(Pipe & Fittings)
PVC-DWV (Drain Waste & Vent -
Pipe & Fittings)
ASTM
SPECIFICATION
D1785
F891
D2466
F441
F438
D2241
F442
D1527
D2468
D2661
D2665
NOTE - When a W-I'KX termination kit (30G79) is installed
as part of the intake and exhaust piping, add twelve feet to
the equivalent length of the pipe (the two 2 inch diameter
90 ° elbows and the 27 inch pipe in the kit).
Primers and solvents must meet ASTM specifications.PVC
primer is specified in ASTM F 656. Use PVC solvent cement
as specified in ASTM D 2564 and ABS solvent cement as
specified in ASTM D 2235. Low temperature solvent cement
is recommended. Metal or plastic strapping may be used for
vent pipe hangers.
Table 3 lists the available exhaust termination kits. All Len-
nox vent terminations are PVC.
Lennox Pad No.
60G77
33K97
15F75
22G44
15F74
44J41
44J40
30G28
30G79
TABLE 3
TERMINATION KITS
Kit LB# Description-Inches (mm)
2" (50,8) Concentric
LB-49107CE _rmin_tion Kit
LB-87942 2" (50.8) Low Pressure Drop
Con_-_ntricTerm. Kit
2" 50.8) Roof
LB-4gl07CC Tgf nination Kit
LB-49107CD 2" (50.8) Wall
Assembly Termination Kit
LB-49107CB 2" (50.8) Wall Ring Kit
3" 76.2) Roof
LB-65678A Termination K t
LB-65701A 3" (7S.2) Wall
/L_rnhlv Terminatinn Kit
WTK •2" (50.8) Wall
Termination Extended Vent
2" (50.8) Wall
WTKX Termination Extension Riser
When making ABS joints, pieces can be prepared with a
cleaner. When joining ABS to PVC matedals, use PVC sol-
vent cement. Refer to this procedure as specified in ASTM
D3138.
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