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Maximum Allowable Vent Pipe Length
Winter Design Temperatures
ºF (ºC)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
1
Poly-Propylene vent pipe (PP) by Duravent and Centrotherm
2
Vent length in table is equivalent length. Each elbow is equivalent to 5ft of straight pipe and should be included when measuring
3
total length.
NOTE - Concentric terminations are the equivalent of 5' and should be considered when measuring pipe length.
NOTE - Maximum uninsulated vent lengths listed may include the termination (vent pipe exterior to the structure ) and cannot exceed
5 linear feet or the maximum allowable intake or exhaust vent length listed in Table 8 or Table 7A through Table 7B.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closed to the furnace.
General Guidelines for Vent Terminations
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the outdoors.
This gas furnace is classified as a direct vent, Category IV
gas furnace.
In Direct Vent applications, the vent termination is limited
by local building codes. In the absence of local codes,
refer to the current National Fuel Gas Code ANSI Z223-1/
NFPA 54 in U.S.A., and current CSA-B149 Natural Gas
and Propane Installation Codes in Canada for details.
Position termination according to location given in
Figure 23. In addition, position termination so it is free
from any obstructions and 12" above the average snow
accumulation.
At vent termination, care must be taken to maintain
protective coatings over building materials (prolonged
exposure to exhaust condensate can destroy protective
coatings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of a condensing unit because
the condensate can damage the painted coating.
NOTE: See Table 8 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32°F (O°C). If required,
exhaust pipe should be insulated with 1/2" (13mm)
507029-05
without Insulation in Unconditioned Space for Winter Design
3
Temperatures Modulating High Efficiency Furnace
1
Vent Pipe Diameter
1-1/2 in.
2 in.
2-1/2 in.
3 in.
1-1/2 in.
2 in.
2-1/2 in.
3 in.
1-1/2 in.
2 in.
2-1/2 in.
3 in.
070
PVC
PP
PVC
2
N/A
N/A
N/A
11
9
7
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table 8.
ArmaFlex
or equivalent. In extreme cold climate areas,
®
3/4" (19mm) ArmaFlex
Insulation on outside runs of exhaust pipe must be painted
or wrapped to protect insulation from deterioration. Exhaust
pipe insulation may not be necessary in some specific
applications.
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and may
block the terminations.
FOR CANADIAN INSTALLATIONS ONLY:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet of
other appliances shall not be less than 12 inches (305
mm).
Issue 2241
090
PP
PVC
2
N/A
N/A
14
12
18
10
N/A
12
6
6
8
N/A
N/A
6
4
8
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
or equivalent may be necessary.
®
IMPORTANT
IMPORTANT
110
PP
2
N/A
15
N/A
8
N/A
6
N/A
N/A
N/A
N/A
N/A
N/A
Page 21 of 73
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