Combustion Air And Vent Pipe - Dunkirk Q90-50 Installation, Operation & Maintenance Manual

Connections And Termination
Provisions for combustion and ventilation air must be
in accordance with section, Air For Combustion and
Ventilation, of the National Fuel Gas Code,ANSI 2223.1/
NFPA54, or Sections 8.2, 8.3 or 8.4 of National Gas and
Propane Installation Code, CAN/CGA-B 149.1, or applicable
provisions of the local building code.
Boilers require dedicated direct vent system. All air for
combustion is taken directly from outdoors through
combustion air intake pipe. All fl ue products are discharged
to outdoors through vent pipe.
1. See Figure 12 thru Figure 14, Pages 24 and 25
for combustion air and vent pipe roof and sidewall
termination. Roof termination is preferred. Combustion
air and vent pipes must terminate together in same
atmospheric pressure zone as shown.
2.
Construction through which vent and air intake pipes
may be installed is maximum 24 inches, minimum ¼"
thickness.
3.
Combustion air and vent pipe fi ttings must conform
to American National Standards Institute (ANSI)
standards and American Society for Testing and
Materials (ASTM) standards D1784 (schedule-40
CPVC), D1785 (schedule-40 PVC), D2665 (PVC-DWV),
D2241 (SDR-21 and SDR-26 PVC), D2661 (ABS-DWV),
or F628 (schedule-40 ABS). Pipe cement and primer
must conform to ASTM standards D2564 (PVC) or
D2235 (ABS).
4.
Canada construct all combustion air and vent pipes
for this unit of ULC S636 listed schedule-40 CPVC,
schedule-40 PVC, PVC-DWV or ABS-DWV pipe and pipe
cement. SDR pipe is not approved in Canada.
• First 3 feet (900mm) of venting must be readily
available for visual inspection.
• Specifi ed primers and glues of certifi ed vent
system must be from single manufacturer, and not
intermixed with other manufacturer's vent system
parts.
• Components of the certifi ed system must not be
interchanged with other vent systems, or unlisted
pipe and/or fi ttings.
NOTICE
Transition from 2" pipe to 3" pipe must be made in
vertical run.
5.
Boiler combustion air and vent piping connections are
sized for 2" pipe. Any pipe size change (to 3") must be
made outside of boiler casing in vertical run of pipe to
allow for proper drainage of vent condensate. Due to
potential for fl ue gas temperatures over 155°F, fi rst
fi ve (5) feet of vent pipe must be CPVC, the remain-
ing vent pipe can be PVC. If any elbows are employed
within the fi rst 5 feet of vent, they must be CPVC too.
Two (2) - 30" pieces of 2" CPVC pipe. 2½" piece of 2"
CPVC pipe, a 2" CPVC elbow and 2" CPVC pipe coupling
are furnished with the boiler.

COMBUSTION AIR AND VENT PIPE

22
6.
Combustion air and vent piping lengths. Table 5,
Page 23 . First 5 ft. of vent piping run must be 2"
CPVC:
Length of pipe is counted from boiler jacket (air
intake pipe) or from vent pipe connector(vent pipe).
Termination is not counted toward the "Total Equivalent
Length".
For elbows, reduce maximum vent length as shown:
• 2" 90° elbow -1 ½ ft. per elbow.
• 3" 90° elbow - 3 ft. per elbow.
To add two (2) 90° elbows to a 3" pipe for a 75 boiler.
Each elbow is 3 ft. per 90 ° elbow for a total of 6 ft..
(1 elbow @ 3 ft. + 1 elbow @ 3 ft. = 6 equivalent ft. of
pipe)
Total additional pipe is then subtracted from maximum
allowable pipe length to give new maximum length of
106 ft. with two (2), 90° elbows.
"TOTAL EQUIVALENT LENGTH":
Original 112 ft. max. - 6 equivalent ft. for 2 elbows =
new 106 ft. maximum length.
7. Pitch combustion air and vent piping back to boiler at
minimum ¼" per ft. (21 mm/m) from intake and vent
terminals so all moisture in combustion air and vent
piping drains to boiler. Pitch pipes continuously with no
sags or low spots where moisture can accumulate and
block fl ow of air or fl ue gas. Combustion air and vent
pipes must be airtight and watertight.
8.
Consider following when determining appropriate
location for termination of combustion air and vent
piping.
• Position termination where vent vapors will not damage
plants/shrubs or air conditioning equipment.
• Position termination as to not be effected by wind eddy,
air born leaves, snow, or recirculated fl ue gases.
• Position termination where it will not be subjected to
potential damage by foreign objects, such as stones,
balls, etc..
• Position termination should where vent vapors are not
objectionable.
• Place vent on wall away from prevailing wind. Locate or
guard vent to prevent accidental contact with people or
pets.
• Terminate vent above normal snowline. Avoid locations
where snow may drift and block vent. Ice or snow may
cause boiler to shut down if vent becomes obstructed.
Example: