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.
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.
TABLE 5—MAXIMUM ALLOWABLE PIPE LENGTH (FT) Continued
ALTITUDE UNIT SIZE
TERMINATION
TYPE
PIPE
DIAMETER
(IN.)*
NUMBER OF 90° ELBOWS
1234 5 6
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† one disk 24 22 21 16 15 13
3† no disk 49 48 47 45 44 43
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† one disk 22 20 19 14 12 11
3† no disk 46 44 43 41 40 38
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† one disk 20 18 17 12 10 8
3† no disk 43 41 39 37 35 34
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† one disk 18 16 14 9 7 5
3† no disk 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.
** 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.
—24—
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