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105561-UIM-B-0605
TABLE 9: Combustion Air Supply and Vent Piping
Models Input
BTUH (kW)
40,000 (11.7)
40,000 (11.7)
60,000 (17.6)
60,000 (17.6)
60,000 (17.6)
80,000 (23.4)
80,000 (23.4)
80,000 (23.4)
100,000 (29.3)
100,000 (29.3)
120,000 (35.1)
135,000 (39.6)
Three elbows (two in vent pipe and one in the air intake pipe) are already accounted for and need not be included in the elbow count from the Table above.
NOTE: If installing furnace at altitudes between 2000 - 4500 ft.(609.6 - 1371.6m), intake and vent pipe length must be reduced by 10 ft. (3.05 m). If the installation requires the
maximum allowable intake and vent pipe length, the furnace must be converted for high altitude operation. Refer to the proper high altitude application instruction for details.
Example: An 80,000 BTUH (23.5 kW) unit requires 35 ft (10.7 m) of
vent with five elbows. In Table 10, look at the three rows with 80,000
(23.5 kW) in the "Models" column. then look to the right in those rows to
the five elbows column. It shows N/A in the 1-1/2" (3.8 cm) row, so 1-1/
2" (5.1 cm) pipe cannot be used. the 2" (5.1 cm) pipe row shows 40 ft
(12.2 m), so up to 40 ft (12.2 m) of 2" (5.1 cm) pipe can be used with
five elbows. The 3" pipe row shows 65 ft (19.8 m), so up to 65 ft (19.8
m) of 3" (7.62 cm) pipe can be used. Therefore, in this example, either
2" (5.1 cm) or 3" (7.62 cm) pipe can be used.
COMBUSTION AIR AND VENT PIPING ASSEMBLY
The final assembly procedure for the combustion air and vent piping is
as follows:
1.
Cut piping to the proper length beginning at the furnace.
2.
Deburr the piping inside and outside.
3.
Chamfer (bevel) the outer edges of the piping.
4.
Dry-fit the vent piping assembly from the furnace to the outside ter-
mination checking for proper fit support and slope.
5.
Dry-fit the combustion air piping assembly checking for proper fit,
support and slope on the following systems:
A.
Sealed combustion air systems from the furnace to the out-
side termination.
12
MAXIMUM ELBOWS AND VENT LENGTHS
Pipe Size
Inches (cm)
1
1-1/2 (3.8)
30
2 (5.1)
70
1-1/2 (3.8)
30
2 (5.1)
60
3 (7.6)
85
1-1/2 (3.8)
20
2 (5.1)
60
3 (7.6)
85
2 (5.1)
25
3 (7.6)
85
3 (7.6)
75
3 (7.6)
75
Maximum Number of Elbows*
2
3
4
25
20
10
N/A
65
60
55
50
25
20
10
N/A
55
50
45
40
80
75
70
65
15
N/A
N/A
N/A
55
50
45
40
80
75
70
65
20
15
N/A
N/A
80
75
70
65
70
65
60
55
70
65
60
55
B.
Ventilated combustion air systems from the furnace to the
attic or crawl space termination.
Solvent cements are flammable and must be used in well-ventilated
areas only. Keep them away from heat, sparks and open flames.
Do not breathe vapors and avoid contact with skin and eyes.
6.
Disassemble the combustion air and vent piping, apply cement
primer and the cement per the manufactures instructions. Primer
and cement must conform to ASTM D2564 for PVC, or ASTM
D2235 for ABS piping.
7.
All joints must provide a permanent airtight and watertight seal.
8.
Support the combustion air and vent piping such that it is angled a
minimum of 1/4" per foot (21 mm/m) so that condensate will flow
back towards the furnace. Piping should be supported with pipe
hangers to prevent sagging.
9.
Seal around the openings where the combustion air and / or vent
piping pass through the roof or sidewalls.
COMBUSTION AIR / VENT CLEARANCES
IMPORTANT: The vent must be installed with the following minimum
clearances, and must comply with local codes and requirements, as
shown in Figure 12.
5
6
7
8
N/A
N/A
N/A
45
35
25
N/A
N/A
N/A
30
20
10
60
50
40
N/A
N/A
N/A
30
20
10
60
50
40
N/A
N/A
N/A
60
50
40
45
35
25
45
35
25
Unitary Products Group
Minimum
Length
5
5
5
5
20
5
5
20
5
20
5
5
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