User Guide
507716-01Page 26 of 58 Issue 1717
Table 6.
Maximum Allowable Exhaust Vent Pipe Length (in ft.) without Insulation in Unconditioned Space For Winter Design
Temperatures Single - Stage High Efciency Furnace
Winter Design Temperatures
1
ºF (ºC)
Vent Pipe
Diameter
Unit Input Size
045 070 090 110 135
32 to 21
(0 to -6)
PVC
2
PP PVC
2
PP PVC
2
PP PVC
2
PP PVC
2
PP
2 in. 18 16 31 28 50 48 30 30 N/A N/A
2-1/2 in. 13 N/A 24 N/A 42 N/A 56 N/A N/A N/A
3 in. 9 9 18 18 35 35 47 47 52 52
20 to 1
(-7 to -17)
2 in. 9 8 18 16 32 29 30 30 N/A N/A
2-1/2 in. 5 N/A 13 N/A 24 N/A 34 N/A N/A N/A
3 in. N/A N/A 8 8 19 19 26 26 30 30
0 to -20
(-18 to -29)
2 in. 5 3 12 10 22 19 30 27 N/A N/A
2-1/2 in. N/A N/A 7 N/A 15 N/A 22 N/A N/A N/A
3 in. N/A N/A N/A N/A 10 10 16 16 18 18
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- 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 5A through Table 5C or Table 6.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See Figure 33.
NOTE - Concentric terminations are the equivalent of 5’ and should be considered when measuring pipe length.
Conditioned
Space
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 33. Insulating Exhaust Pipe in an Unconditioned Space