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Duct System
Use industry-approved standards 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
− Operation of this furnace in heating mode (indoor
blower operating at selected heating speed) with an exter-
nal static pressure which exceeds 0.8 inches w.c. may re-
sult in erratic limit operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a removable
access panel should be installed in the supply air duct. The
access panel should be large enough to permit inspection
(by reflected light) of the heat exchanger for leaks after the
furnace is installed. If present, this 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
Return air must not be drawn from a room where this
furnace, or any other gas−fueled appliance (i.e., water
heater), or carbon monoxide−producing device (i.e.,
wood fireplace) 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 pres-
sure, 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 monoxide gas. This toxic gas might then be dis-
tributed throughout the house by the furnace duct sys-
tem.
Return air can be brought in through the bottom or either
side of the furnace (return air brought in through either side
of the furnace allowed in upflow applications only). 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 safe-
ly. Use fiberglass sealing strips, caulking, or equivalent
sealing method between the plenum and the furnace cabi-
net to ensure a tight seal. If a filter is installed, size the re-
turn air duct to fit the filter frame.
Pipe & Fittings Specifications
All pipe, fittings, primer and solvent cement must conform
with American National Standard Institute and the Ameri-
can Society for Testing and Materials (ANSI/ASTM) stan-
dards. The solvent shall be free−flowing and contain no
lumps, undissolved particles or any foreign matter that ad-
versely affects the joint strength or chemical resistance of
the cement. The cement shall show no gelation, stratifica-
tion, or separation that cannot be removed by stirring. Re-
fer to table 2 for approved piping and fitting materials.
TABLE 2
PIPING AND FITTINGS SPECIFICATIONS
Schedule 40 PVC (Pipe)
D1785
Schedule 40 PVC (Cellular Core Pipe)
F891
Schedule 40 PVC (Fittings)
D2466
Schedule 40 CPVC (Pipe)
F441
Schedule 40 CPVC (Fittings)
F438
SDR−21 PVC or SDR−26 PVC (Pipe)
D2241
SDR−21 CPVC or SDR−26 CPVC (Pipe)
F442
Schedule 40 ABS Cellular Core DWV (Pipe)
F628
Schedule 40 ABS (Pipe)
D1527
Schedule 40 ABS (Fittings)
D2468
ABS−DWV (Drain Waste & Vent)
(Pipe & Fittings)
D2661
PVC−DWV (Drain Waste & Vent)
Pipe & Fittings)
D2665
PRIMER & SOLVENT CEMENT
ASTM
SPECIFICATION
PVC & CPVC Primer
F656
PVC Solvent Cement
D2564
CPVC Solvent Cement
F493
ABS Solvent Cement
D2235
PVC/CPVC/ABS All Purpose Cement For
Fittings & Pipe of the same material
D2564, D2235, F493
ABS to PVC or CPVC Transition Solvent
Cement
D3138
CANADA PIPE & FITTING & SOLVENT
CEMENT
MARKING
PVC & CPVC Pipe and Fittings
ULCS636
PVC & CPVC Solvent Cement
ABS to PVC or CPVC Transition Cement
CAUTION
Solvent cements for plastic pipe are flammable liq-
uids and should be kept away from all sources of
ignition. Do not use excessive amounts of solvent
cement when making joints. Good ventilation should
be maintained to reduce fire hazard and to minimize
breathing of solvent vapors. Avoid contact of cement
with skin and eyes.
IMPORTANT
SLP98UHV exhaust and intake connections are
made of PVC. Use PVC primer and solvent cement
when using PVC vent pipe. When using ABS vent
pipe, use transitional solvent cement to make con-
nections to the PVC fittings in the unit.
Use PVC primer and solvent cement or ABS solvent cement
meeting ASTM specifications, refer to Table 2. As an alter-
nate, use all purpose cement, to bond ABS, PVC, or CPVC
pipe when using fittings and pipe made of the same materi-
als. Use transition solvent cement when bonding ABS to ei-
ther PVC or CPVC.
Low temperature solvent cement is recommended. Metal or
plastic strapping may be used for vent pipe hangers. Uni-
formly apply a liberal coat of PVC primer for PVC
