FIRE AND EXPLOSION HAZARD
Failure to follow this warning could result in fire, property
damage, personal injury, or death.
Solvent cements are combustible. Keep away from heat,
sparks, and open flame. Use only in well-ventilated areas.
Avoid breathing in vapor or allowing contact with skin or
eyes.
In Canada, construct all combustion-air and vent pipes for this unit
of CSA or ULC listed schedule-40 PVC, PVC-DWV or ABS-
DWV pipe and pipe cement. SDR pipe is NOT approved in
Canada.
In direct vent (2-pipe) systems, combustion air and vent pipes must
terminate together in same atmospheric pressure zone, either
through roof or sidewall (roof termination preferred), using acces-
sory termination kit. See Table 8 for required clearances.
In non-direct vent (1-pipe) system, vent pipe termination must be
installed with adequate clearances to building openings and
equipment to comply with national and local codes. See Table 9
for required clearances.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in property
damage, personal injury, or death.
All combustion-air and vent pipes must be airtight and
watertight. Pipes must also terminate exactly as shown in Fig.
44 for direct vent (2-pipe) system and Fig. 45 for non-direct
vent (1-pipe) system.
An abandoned masonry chimney may be used as a raceway for
properly insulated and supported combustion-air (when appli-
cable) and vent pipes. Each furnace must have its own set of
combustion-air and vent pipes and be terminated individually, as
shown in Fig. 44 for Direct Vent (2-Pipe) system and Fig. 45 for
Non-Direct Vent (1-Pipe) system.
A furnace shall not be connected to a chimney flue serving a
separate appliance designed to burn solid fuel.
Other gas appliances with their own venting system may also use
the abandoned chimney as a raceway providing it is permitted by
local code, the current edition of the National Fuel Gas Code and
the vent or liner manufacturer’s installation instructions. Care must
be taken to prevent the exhaust gases from one appliance from
contaminating the combustion air of other gas appliances.
UNIT MAY NOT OPERATE
Failure to follow this caution may result in intermittent unit
operation.
When vent pipe is exposed to temperatures below freezing,
such as when it passes through an unheated space or when a
chimney is used as a raceway, pipe must be insulated as
shown in Table 10 with Armaflex-type insulation.
Furnace combustion air and vent pipe connections are sized for
2-in. pipe. Any pipe size change should be made outside furnace
casing in vertical pipe. The transition has to be made as close to the
furnace as reasonably possible.
COMBUSTION AIR PIPE
General
Furnace combustion-air connection must be attached as shown in
Fig. 38. Combustion-air intake housing plug may need to be
relocated in some applications.
For Non-Direct Vent (1-Pipe) system, combustion-air must termi-
nate outside of furnace casing with 1 elbow. Orient elbow so that
its opening faces down for upflow or downflow applications.
Orient elbow so that its opening faces sideways (left or right) for
horizontal left or horizontal right applicationS. Maintain a 3-in
minimum clearance between the opening of the combustion-air
inlet pipe and any object.
Table 7—Approved Combustion-Air and Vent Pipe, Fitting and Cement Materials
ASTM SPECIFICATION
(MARKED ON MATERIAL)
MATERIAL PIPE FITTINGS SOLVENT CEMENT AND PRIMERS DESCRIPTION
D1527 ABS Pipe — — Schedule-40
D1785 PVC Pipe — — Schedule-40
D2235 For ABS — —
Solvent
Cement
For ABS
D2241 PVC Pipe — — SDR-21 & SDR-26
D2466 PVC — Fittings — Schedule-40
D2468 ABS — Fittings — Schedule-40
D2564 For PVC — —
Solvent
Cement
For PVC
D2661 ABS Pipe Fittings — DWV at Schedule-40 IPS sizes
D2665 PVC Pipe Fittings — DWV
F438 CPVC — Fittings — Schedule-40
F441 CPVC Pipe — — Schedule-40
F442 CPVC Pipe — — SDR
F493 For CPVC — —
Solvent
Cement
For CPVC
F628 ABS Pipe — — Cellular Core DWV at Schedule-40 IPS sizes
F656 For PVC — — Primer For PVC
F891 PVC Pipe — — Cellular Core Schedule-40 & DWV
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