42
Table 7 — Maximum Allowable Pipe Length -- Ft (M) (Continued)
ALTITUDE
UNIT SIZE
(BTUH)
Direct Vent (2--Pipe Only)
NUMBER OF 90
_
ELBOWS
Termination
Type
Pipe Dia
In. (mm)*
1
2
3
4
5
6
6001 to 7000
(1829 to 2134)‡
60,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
35 (10.7)
30 (9.1)
25 (7.6)
20 (6.1)
15 (4.6)
10 (3.0)
2 (51)
70 (21.3)
70 (21.3)
68 (20.7)
67 (20.4)
66 (20.1)
64 (19.5)
80,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
20 (6.1)
15 (4.6)
10 (3.0)
5 (1.5)
NA
NA
2 (51)
70 (21.3)
70 (21.3)
68 (20.7)
67 (20.4)
62
(18.9)
57 (17.4)
100,000
2 Pipe or 2---In. (51)
Concentric
2 (51)
31 (9.4)
26 (7.9)
21 (6.4)
16 (4.9)
11 (3.4)
6 (1.8)
2---1/2 (64)
70 (21.3)
70 (21.3)
68 (20.7)
67 (20.4)
66 (20.1)
64 (19.5)
120,000
2 Pipe or 3---In. (76)
Concentric
3 (76) one disk†
49 (14.9)
48 (14.6)
47 (14.3)
45 (13.7)
44 (13.4)
43 (13.1)
ALTITUDE
UNIT SIZE
(BTUH)
Termination
Type
Pipe Dia
In. (mm)*
NUMBER OF 90
_
ELBOWS
1
2
3
4
5
6
7001 to 8000
(2134 to 2438)‡
60,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
32 (9.8)
27 (8.2)
22 (6.7)
17 (5.2)
12 (3.7)
7 (2.1)
2 (51)
66 (20.1)
65 (19.8)
63 (19.2)
62 (18.9)
60 (18.3)
59 (18.0)
80,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
18 (5.5)
13 (4.0)
8 (2.4)
NA
NA
NA
2 (51)
66 (20.1)
65 (19.8)
63 (19.2)
62 (18.9)
57 (17.4)
52 (15.8)
100,000
2 Pipe or 2---In. (51)
Concentric
2 (51)
29 (8.8)
24 (7.3)
19 (5.8)
14 (4.3)
9 (2.7)
NA
2---1/2 (64)
66 (20.1)
65 (19.8)
63 (19.2)
62 (18.9)
60 (18.3)
59 (18.0)
120,000
2 Pipe or 3---In. (76)
Concentric
3 (76) one disk†
46 (14.0)
44 (13.4)
43 (13.1)
41 (12.5)
40 (12.2)
38 (11.6)
ALTITUDE
UNIT SIZE
(BTUH)
Termination
Type
Pipe Dia
In. (mm)*
NUMBER OF 90
_
ELBOWS
1
2
3
4
5
6
8001 to 9000
(2438 to 2743)‡
60,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
30 (9.1)
25 (7.6)
20 (6.1)
15 (4.6)
10 (3.0)
5 (1.5)
2 (51)
62 (18.9)
60 (17.8)
58 (17.7)
56 (17.1)
55 (16.8)
53 (16.2)
80,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
17 (5.2)
12 (3.1)
7 (2.1)
NA
NA
NA
2 (51)
62 (18.9)
60 (18.3)
58 (17.7)
56 (17.1)
51 (15.5)
46 (14.0)
100,000
2 Pipe or 2---In. (51)
Concentric
2 (51)
27 (8.2)
22 (6.7)
17 (5.2)
12 (3.7)
7 (2.1)
NA
2---1/2 (64)
62 (18.9)
60 (18.3)
58 (17.7)
56 (17.1)
55 (16.8)
53 (16.2)
120,000
2 Pipe or 3---In. (76)
Concentric
3 (76) one disk†
43 (13.1)
41 (12.5)
39 /11.9)
37 (11.3)
35 (10.7)
34 (10.4)
ALTITUDE
UNIT SIZE
(BTUH)
Termination
Type
Pipe Dia
In. (mm)*
NUMBER OF 90
_
ELBOWS
1
2
3
4
5
6
9001 to 10000
(2743 to 3048)‡
60,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
27 (8.2)
22 (6.7)
17 (5.2)
12 (3.7)
7 (2.1)
NA
2 (51)
57 (17.4)
55 (16.8)
53 (16.2)
51 (15.5)
49 (14.9)
47 (14.3)
80,000
2 Pipe or 2---In. (51)
Concentric
1---1/2 (38)
15 (4.6)
10 (3.0)
5 (1.5)
NA
NA
NA
2 (51)
57 (17.4)
55 (16.8)
53 (16.2)
51 (15.5)
46 (14.0)
41 (12.5)
100,000
2 Pipe or 2---In. (51)
Concentric
2 (51)
24 (7.3)
19 (5.8)
14 (4.3)
9 (2.7)
NA
NA
2---1/2 (64)
57 (17.4
55 (16.8)
53 (16.2)
51 (15.5)
49 (14.9)
47 (14.3)
120,000
2 Pipe or 3---In. (76)
Concentric
3 (76) one disk†
39 (11.9)
37 (11.3)
35 (10.7)
33 (10.1)
31 (9.5)
29 (8.8)
* Disk usage---Unless otherwise stated, use perforated disk assembly (factory---supplied in loose parts bag).
{
Wide radius elbow.
}
Vent sizing for Canadian installations over 4500 ft. (1370M) above sea level are subject to acceptance by the local authorities having jurisdiction.
NA---Not Allowed; pressure switch will not make.
NOTES:
1. Do not use pipe size greater than those specified in table or incomplete combustion, flame disturbance, or flame sense lockout may occur.
2. Size both the combustion---air and vent pipe independently, determine the smallest diameter allowed by the table for each pipe, then use the larger diameter for both pipes.
3. Assume two 45
_
elbows equal one 90
_
elbow. Long radius elbows are desirable and may be required in some cases.
4. Elbows and pipe sections within the furnace casing and at the vent termination should not be included in vent length or elbow count.
5. The minimum pipe length is 5 ft. (1.5M) for all applications.
355C
A
V
