106633-UIM-A-0205
10
Unitary Products Group
COMBUSTION AIR/VENT PIPE SIZING
Select the correct size from Table 8. The size will be determined by a
combination of furnace model, total length of run, and the number of
elbows required. The following rules must also be observed.
1.
Long radius (sweep) elbows are required for all units.
2.
Elbows are assumed to be 90 degrees. Two 45-degree elbows
count as one 90-degree elbow.
3.
Elbow count refers to combustion air piping and vent piping sepa-
rately. For example, if the table allows for 5 elbows, this will allow a
maximum of 5 elbows in the combustion air piping and a maximum
of 5 elbows in the vent piping.
4.
Three vent terminal elbows (two for vent pipe and one for air
intake pipe) are already accounted for as vent termination.
5.
Combustion air and vent piping must be of the same diameter.
6.
All combustion air/vent pipe and fittings must conform to American
National Standards Institute (ANSI) standards and American Soci-
ety for Testing and Materials (ASTM) standards D1785 (Schedule
40 PVC), D2665 (PVC-DWV), F891 (PVC-DWV Cellular Core).
D2241 (SDR-21 and SDR-26 PVC), D2261 (ABS-DWV), or F628
(Schedule 40 ABS. Pipe cement and primer must conform to
ASTM Standards D2564 (PVC) or D2235 (ABS).
7.
The use of flexible connectors or no hub connectors in the vent
system is not allowed. This type connection is allowed in the com-
bustion air pipe near the furnace for air conditioning coil accessibil-
ity.
8.
Sidewall horizontal vent terminals and roof mounted vertical termi-
nals may be field fabricated. Standard PVC/SRD fittings may be
used. Terminal configuration must comply as detailed in this sec-
tion.
IMPORTANT:
Accessory concentric vent / intake termination kits
1CT0302 and 1CT0303 are available and approved for use with these
furnaces. Horizontal sidewall vent terminations kit 1HT0901 is also
approved for use with these furnaces.
IMPORTANT:
Intake and vent pipe connections are sized as shown in
Table 7. However, most models require larger vents and some installa-
tions will require larger intake piping. Use Table 8 for the sizes of the
pipe that can be used with each model.
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 the Table above, 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.
B.
Ventilated combustion air systems from the furnace to the
attic or crawl space termination.
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.
TABLE 7:
Combustion Air Intake and Vent Connection Size at Furnace
(All Models)
FURNACE VENT CONNECTION SIZES
Furnace Input
60 - 100 MBH
(17.6-29.3 kW)
120 MBH
(35.2 kW)
Intake Pipe Size
2” (51 mm)
3" (76 mm)
Vent Pipe Size
2” (51 mm)
2" (51 mm)
TABLE 8:
Combustion Air Supply and Vent Piping
MAXIMUM ELBOWS AND VENT LENGTHS
Models Input
BTUH (kW)
Pipe Size
Inches (cm)
Maximum Number of Elbows*
Minimum
Length
1 2 3 4 5 6 7 8
40,000 (11.7)
1-1/2 (3.8)
30
25
20
10
N/A
N/A
N/A
N/A
5
40,000 (11.7)
2 (5.1)
70
65
60
55
50
45
35
25
5
60,000
(17.6)
1-1/2
(3.8)
30 25 20 10 N/A
N/A
N/A
N/A
5
60,000
(17.6)
2
(5.1)
60 55 50 45 40 30 20 10
5
60,000
(17.6)
3
(7.6)
85 80 75 70 65 60 50 40
20
80,000
(23.4)
1-1/2
(3.8)
20 15 N/A N/A N/A N/A N/A N/A
5
80,000
(23.4)
2
(5.1)
60 55 50 45 40 30 20 10
5
80,000
(23.4)
3
(7.6)
85 80 75 70 65 60 50 40
20
100,000
(29.3)
2
(5.1)
25 20 15 N/A N/A N/A N/A N/A
5
100,000
(29.3)
3
(7.6)
85 80 75 70 65 60 50 40
20
120,000
(35.1)
3
(7.6)
75 70 65 60 55 45 35 25
5
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.