40
Table 6 – Maximum Allowable Exposed Vent Pipe Length with Insulation in
Winter Design Temperature Ambient*
UNIT SIZE
WINTER DESIGN
TEMPERATURE
MAXIMUM PIPE
DIAMETER IN.
(MM)
INSULATION THICKNESS†
0
3/8
1/2
3/4
1
060
20° F / ---7° C
2 (51)
28 (8.5)
50 (15.2)
56 (17.1)
66 (20.1)
70 (21.3)
0° F / ---18° C
2 (51)
11 (3.4)
25 (7.6)
29 (8.8)
35 (10.7)
41 (12.5)
---20° F / ---29° C
2 (51)
4 (1.2)
15 (4.6)
18 (5.5)
23 (7.0)
27 (8.2)
080
20° F / ---7° C
2 (51)
36 (11.0)
65 (19.8)
70 (21.3)
70 (21.3)
70 (21.3)
0° F / ---18° C
2 (51)
16 (4.9)
34 (10.4)
39 (11.9)
47 (14.3)
55 (16.8)
---20° F / ---29° C
2 (51)
8 (2.4)
21 (6.4)
25 (7.6)
31 (9.4)
37 (11.3)
100
20° F / ---7° C
2---1/2 (64)
42 (12.8)
70 (21.3)
70 (21.3)
70 (21.3)
70 (21.3)
0° F / ---18° C
2---1/2 (64)
18 (5.5)
38 (11.6)
43 (13.1)
53 (16.2)
61 (18.6)
---20° F / ---29° C
2---1/2 (64)
9 (2.7)
23 (7.0)
27 (8.2)
34 (10.4)
41 (12.5)
120
20° F / ---7° C
3 (76)
44 (13.4)
70 (21.3)
70 (21.3)
70 (21.3)
70 (21.3)
0° F / ---18° C
3 (76)
18 (5.5)
38 (11.6)
44 (13.4)
54 (16.5)
63 (19.2)
---20° F / ---29° C
3 (76)
8 (2.4)
23 (7.0)
27 (8.2)
35 (10.7)
41 (12.5)
* Pipe length (ft/m) specified for maximum pipe lengths located in unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable
pipe length as specified in Table 7.
†
Insulation thickness based on R value of 3.5 per in.
355C
A
V