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TABLE 7
Maximum Allowable Exhaust Vent Pipe Length Without Insulation
In Unconditioned Space For Winter Design Temperatures
Winter Design
Temperatures
1
°F (°C)
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 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 which ever is less.
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