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Specifications subject to change without notice.
Size the Vent and Combustion Air Pipes
General
OPTIONAL CONFIGURATION FOR COMBUSTION
AIR INLET PIPE
In applications where there is a risk of excessive moisture
entering the combustion air inlet pipe, a moisture trap may be
added to the inlet pipe to help prevent moisture from entering
the furnace from the combustion air inlet pipe. See Fig. 51.
When sizing venting systems, the equivalent length of the
optional moisture trap (15 feet/5 M) must be taken into
account.
NOTICE
Furnace combustion air and vent pipe connections are sized for
2-in. (50 mm ND) PVC/ABS DWV pipe. The combustion air and
vent pipe connections also accommodate 60 mm polypropylene
venting systems with outside diameters of approximately 60 mm
(2--3/8 inches). Any pipe diameter change should be made outside
furnace casing in vertical pipe. Any change in diameter to the pipe
must be made as close to the furnace as reasonably possible. See
Fig. 48.
FURNACE
PIPE DIAMETER
TRANSITION IN
VERTICAL SECTION
NOT IN
HORIZONTAL
SECTION
A93034
Fig. 48 -- Combustion Air and Vent Pipe Diameter Transition
Location and Elbow Configuration
The Maximum Vent Length for the vent and combustion air pipe
(when used) is determined from the Maximum Equivalent Vent
Length in Table 13 minus the number of fittings multiplied by the
deduction for each type of fitting used from Table 14.
OPTIONAL TERMINATION
BRACKET FOR 2-PIPE
TERMINATIONS
12-IN. (305 MM)
ABOVE ANTICIPATED
SNOW LEVEL
12 IN. (305 MM) MIN.
SEPARATION BETWEEN
BOTTOM OF COMBUSTION
AIR AND BOTTOM OF VENT.
12 IN. (305 MM) MIN. SEPARATION
BETWEEN BOTTOM OF
COMBUSTION AIR AND
BOTTOM OF VENT.
MAINTAIN 12 IN. (305 MM)
CLEARANCE ABOVE
HIGHEST ANTICIPATED
SNOW LEVEL OR GRADE,
WHICHEVER IS GREATER.
COMBUSTION-AIR
(ELBOW PARALLEL TO WALL)
OPTIONAL
BRACKET
COUPLING
OVERHANG
12 IN. (305 MM) MIN. GROUND
LEVEL OR ANTICIPATED SNOW LEVEL
EXHAUST
CLEARANCE TO OVERHANG PER CODE
A13078
Fig. 49 -- Alberta and Saskatchewan Vent Termination