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ALTITUDE
UNIT SIZE
042040
042060
042080
6001 to 7000‡
→060080
060100
→060120**
042040
042060
042080
7001 to 8000‡
→060080
060100
→060120**
042040
042060
042080
8001 to 9000‡
→060080
060100
→060120**
042040
042060
042080
9001 to 10000‡
→060080
060100
→060120**
* 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.
** Tentative data.
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, 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 for all applications.
d. Install pipe support (factory-supplied in loose parts bag)
into selected furnace casing combustion-air pipe hole.
Pipe support should be positioned to bottom of casing
hole.
e. Insert 2-in. diameter pipe into intake housing.
NOTE: A 2-in. diameter pipe must be used within the furnace
casing. Make all pipe diameter transitions outside furnace casing.
f. Drill a 1/8-in. hole in 2-in. combustion-air pipe using
hole in intake housing as a guide.
g. Install a field-supplied No. 6 or No. 8 sheet metal screw
into combustion-air pipe.
NOTE: DO NOT OVERTIGHTEN SCREW. Breakage to intake
housing or fitting may cause air leakage to occur.
TABLE 5—MAXIMUM ALLOWABLE PIPE LENGTH (FT) Continued
TERMINATION
TYPE
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 3-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 3-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 3-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 2-In.
Concentric
2 Pipe or 3-In.
Concentric
PIPE
DIAMETER
1
2
(IN.)*
1-1/2
35
30
2
70
70
1-1/2
35
30
2
70
70
1-1/2
20
15
2
70
70
2
31
26
2-1/2
70
70
3† one disk
24
22
3† no disk
49
48
1-1/2
32
27
2
66
65
1-1/2
32
27
2
66
65
1-1/2
18
13
2
66
65
2
29
24
2-1/2
66
65
3† one disk
22
20
3† no disk
46
44
1-1/2
30
25
2
62
60
1-1/2
30
25
2
62
60
1-1/2
17
12
2
62
60
2
27
22
2-1/2
62
60
3† one disk
20
18
3† no disk
43
41
1-1/2
27
22
2
57
55
1-1/2
27
22
2
57
55
1-1/2
15
10
2
57
55
2
24
19
2-1/2
57
55
3† one disk
18
16
3† no disk
39
37
NOTE: Do not attach combustion-air intake pipe permanently to
combustion-air intake housing since it may be necessary to remove
pipe for service of ignitor or flame sensor.
COMBUSTION-AIR INTAKE HOUSING PLUG
FITTING
The combustion-air intake plug fitting must be installed in
unused combustion-air intake housing. This fitting must be
attached by using RTV sealant, or by drilling a 1/8-in. hole
in fitting, using hole in intake housing as a guide. Install a
field-supplied No. 6 or No. 8 sheet metal screw.
NOTE: DO NOT OVERTIGHTEN SCREW. Breakage to intake
housing or fitting may cause air leakage to occur.
—24—
NUMBER OF 90° ELBOWS
3
4
5
25
20
15
68
67
66
25
20
15
68
67
66
10
5
NA
68
67
62
21
16
11
68
67
66
21
16
15
47
45
44
22
17
12
63
62
60
22
17
12
63
62
60
8
NA
NA
63
62
57
19
14
9
63
62
60
19
14
12
43
41
40
20
15
10
58
56
55
20
15
10
58
56
55
7
NA
NA
58
56
51
17
12
7
58
56
55
17
12
10
39
37
35
17
12
7
53
51
49
17
12
7
53
51
49
5
NA
NA
53
51
46
14
9
NA
53
51
49
14
9
7
35
33
31
6
10
64
10
64
NA
57
6
64
13
43
7
59
7
59
NA
52
NA
59
11
38
5
53
5
53
NA
46
NA
53
8
34
NA
47
NA
47
NA
41
NA
47
5
29
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