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TABLE 7—MAXIMUM ALLOWABLE PIPE LENGTH (FT) Continued
ALTITUDE
UNIT
SIZE
TERMINATION
TYPE
PIPE DIAMETER
(IN.)*
NUMBER OF 90° ELBOWS
123456
6001 to 7000‡
042040
2 Pipe or 2-In.
Concentric
1-1/2 35 30 25 20 15 10
2 70706867 66 64
042060
2 Pipe or 2-In.
Concentric
1-1/2 35 30 25 20 15 10
2 70706867 66 64
042080
060080
2 Pipe or 2-In.
Concentric
1-1/2 20 15 10 5 NA NA
2 70706867 62 57
060100
2 Pipe or 2-In.
Concentric
2 31262116 11 6
2-1/2 70 70 68 67 66 64
060120
2 Pipe or 3-In.
Concentric
3† 49 48 47 45 44 43
Altitude
Unit
Size
Termination
Type
Pipe Diameter
(In.)*
Number of 90° Elbows
123456
7001 to 8000‡
042040
2 Pipe or 2-In.
Concentric
1-1/2 32 27 22 17 12 7
2 66656362 60 59
042060
2 Pipe or 2-In.
Concentric
1-1/2 32 27 22 17 12 7
2 66656362 60 59
042080
060080
2 Pipe or 2-In.
Concentric
1-1/2 18 13 8 NA NA NA
2 66656362 57 52
060100
2 Pipe or 2-In.
Concentric
2 29241914 9 NA
2-1/2 66 65 63 62 60 59
060120
2 Pipe or 3-In.
Concentric
3† 46 44 43 41 40 38
Altitude
Unit
Size
Termination
Type
Pipe Diameter
(In.)*
Number of 90° Elbows
123456
8001 to 9000‡
042040
2 Pipe or 2-In.
Concentric
1-1/2 30 25 20 15 10 5
2 62605856 55 53
042060
2 Pipe or 2-In.
Concentric
1-1/2 30 25 20 15 10 5
2 62605856 55 53
042080
060080
2 Pipe or 2-In.
Concentric
1-1/2 17 12 7 NA NA NA
2 62605856 51 46
060100
2 Pipe or 2-In.
Concentric
2 27221712 7 NA
2-1/2 62 60 58 56 55 53
060120
2 Pipe or 3-In.
Concentric
3† 43 41 39 37 35 34
Altitude
Unit
Size
Termination
Type
Pipe Diameter
(In.)*
Number of 90° Elbows
123456
9001 to 10000‡
042040
2 Pipe or 2-In.
Concentric
1-1/2 27 22 17 12 7 NA
2 57555351 49 47
042060
2 Pipe or 2-In.
Concentric
1-1/2 27 22 17 12 7 NA
2 57555351 49 47
042080
060080
2 Pipe or 2-In.
Concentric
1-1/2 15 10 5 NA NA NA
2 57555351 46 41
060100
2 Pipe or 2-In.
Concentric
2 241914 9 NANA
2-1/2 57 55 53 51 49 47
060120
2 Pipe or 3-In.
Concentric
3† 39 37 35 33 31 29
* 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 for all applications.
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