Allied A96US2V - Maximum Allowable Exhaust Vent Pipe Length Without Insulation

507404-02Page 26 of 80 Issue 1448
Table 6
Position termination according to location given in Figures 31
and 32. 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 (1.8 m) of a condensing unit because the
condensate can damage the painted coating.
NOTE: See Table 6 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperature below 32° F (0° C). If required,
exhaust pipe should be insulated with 1/2” (13 mm), Armaex
or equivalent when run through an unconditional area. In
extremely cold climate areas with temperature below 20° F
(6.7° C) it is recommended that, 3/4” (19 mm) Armaex 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 specic applications.
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
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and may
block the terminations.
IMPORTANT
NOTE: During extremely cold temperatures, below
approximately 20° F (6.7° 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 specication sheets for part numbers.
Maximum Allowable Exhaust Vent Pipe Length Without Insulation
In Unconditioned Space For Winter Design Temperatures
Winter Design Temperatures
1
ºF (ºC)
Vent Pipe Diameter
Unit Input Size
045 070 090 110 135
32 to 21
(0 to -6)
2 in. 20 30 40 24 n/a
2-1/2 in. 15 22 30 40 n/a
3 in. 12 18 25 32 32
20 to 1
(-7 to -17)
2 in. 12 20 25 24 n/a
2-1/2 in. 10 14 20 24 n/a
3 in. 6 10 15 20 20
0 to -20
(-18 to -29)
2 in. 8 12 18 22 n/a
2-1/2 in. 6 8 12 16 n/a
3 in. 2 6 10 12 12
1
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE
Fundamentals Handbook.
NOTE- Maximum uninsulated vent lengths listed cannot exceed the maximum allowable intake or
exhaust vent length listed in table 5 or 6.