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—5—
COMBUSTION-AIR AND VENT PIPING
MAXIMUM ALLOWABLE PIPE LENGTH (FT)
*
Disk usage—Unless otherwise specified, use perforated disk assembly (factory-supplied in loose parts bag).
† 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, 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.
MAXIMUM ALLOWABLE EXPOSED VENT PIPE LENGTH (FT) WITH AND WITHOUT INSULATION
IN WINTER DESIGN TEMPERATURE AMBIENT
*
*
Pipe length (ft) specified for maximum vent pipe lengths located in unconditioned spaces. Vent pipes located in unconditioned space cannot exceed the
total allowable pipe length as specified in Maximum Allowable Pipe Length table.
† Insulation thickness based on R value of 3.5 per in.
ALTITUDE
ABOVE SEA
LEVEL (FT) UNIT SIZE TERMINATION TYPE
PIPE DIA
(IN.)
*
NUMBER OF 90° ELBOWS
123456
0 to 2000
036080
048080
060080
2 Pipe or 2-In. Concentric
1-1/2 10 NA NA NA NA NA
2 555035303020
2-1/2 70 70 70 70 70 70
2001 to 3000
036080
048080
060080
2 Pipe or 2-In. Concentric
2 494430252515
2-1/2 70 70 70 70 70 70
3001 to 4000
036080
048080
060080
2 Pipe or 2-In. Concentric
2 464128232213
2-/12 70 70 70 70 70 70
4001 to 5000†
036080
048080
060080
2 Pipe or 2-in Concentric
2 443926212011
2-1/2 70 70 70 70 70 70
5001 to 6000†
036080
048080
060080
2 Pipe or 2-In. Concentric
2 4136231817 8
2-1/2 70 70 70 70 70 70
6001 to 7000†
036080
048080
060080
2 Pipe or 2-In. Concentric
2 3833211615 6
2-1/2 70 70 68 67 66 64
7001 to 8000†
036080
048080
060080
2 Pipe or 2-In. Concentric
2 3631191412NA
2-1/2 66 65 63 62 60 59
8001 to 9000†
036080
048080
060080
2 Pipe or 2-In. Concentric
2 3328171210NA
2-1/2 62 60 58 56 55 53
9001 to
10,000†
036080
048080
060080
2 Pipe or 2-In. Concentric
2 302514 9 7NA
2-1/2 57 55 53 51 49 47
UNIT SIZE
WINTER DESIGN
TEMPERATURE
(°F)
MAX PIPE
DIAMETER
(IN.)
WITHOUT
INSULATION
WITH 3/8-IN. OR
THICKER INSULATION†
036080
048080
060080
20 2-1/2 70 70
0 2-1/2 47 70
–20 2-1/2 28 70