507405-05Page 22 of 72 Issue 1621
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and may
block the terminations.
IMPORTANT
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).
IMPORTANT
NOTE: See Table 8 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32° F (0° C). If required,
exhaust pipe should be insulated with 1/2” (13 mm), Armaex
or equivalent when run through an unconditioned area. In
extremely cold climate areas with temperature below 20° F
(6.7° C) it is recommended that 3/4” (19 mm) Armaex or
equivalent be used. Insulation on outside runs of exhaust
pipe should be painted or wrapped to protect insulation
from deterioration in accordance with the insulation
manufacturers recommendation. Exhaust pipe insulation
may not be necessary in some specic applications.
NOTE: During extremely cold temperatures, below
approximately 20° F (6° C), units with long runs of vent
pipe through unconditioned space, even when insulated,
may form ice in the exhaust termination that prevents the
unit from operating properly. Longer run times of at least 5
minutes will alleviate most icing problems. Also, a heating
cable may be installed on exhaust piping and termination
to prevent freeze-ups. Heating cable installation kits are
available, see unit specication sheets for part numbers.
Table 8
Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation
In Unconditioned Space For Winter Design Temperatures
Winter Design Temperatures
1
ºF (ºC)
Vent Pipe
Diameter
Unit Input Size
045 070 090 110
32 to 21
(0 to -6)
PVC
2
PP PVC
2
PP PVC
2
PP PVC
2
PP
2 in. 21 18 33 30 46 42 30 30
2-1/2 in. 16 N/A 26 N/A 37 N/A 36 N/A
3 in. 12 12 21 21 30 30 29 29
20 to 1
(-7 to -17)
2 in. 11 9 19 17 28 25 27 24
2-1/2 in. 7 N/A 14 N/A 21 N/A 20 N/A
3 in. N/A N/A 9 9 16 16 14 14
0 to -20
(-18 to -29)
2 in. 6 4 12 10 19 16 18 15
2-1/2 in. N/A N/A 7 N/A 13 N/A 12 N/A
3 in. N/A N/A N/A N/A 8 8 7 7
1
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2
Poly-Propylene vent pipe (PP) by Duravent and Centrotherm
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 5 or 6.
NOTE - If insulation is required an unconditioned space, it must be located on the pipe closed to the furnace.
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