5715184-BIM-A-0519
Johnson Controls Ducted Systems
19
Dimensions are those required in Standard ASTM D-3311.
Example:
An 80,000 BTUH furnace requires 32 ft of pipe and five 90º elbows.
Using 2 in. pipe and standard elbows, the total equivalent length is:
This exceeds the 65 ft maximum equivalent length of 2 in. pipe allowed
for that model and is thus not acceptable.
By using sweep elbows, the total equivalent length is:
This is less than the 65 ft maximum equivalent length of 2 in. pipe
allowed for that model and is thus acceptable.
Alternatively, using 3 in. pipe and standard elbows, the total equivalent
length is:
This is less than the 90 ft maximum equivalent length of 3 in. pipe
allowed for that model and is thus acceptable.
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 manufacturer’s 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.
Install the combustion air and vent piping such that it has a 1/4 in.
per foot (21 mm/m) grade so that condensate flows back toward the
furnace. Piping must 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/VENTING
FIGURE 21:
Elbow Dimensions
TABLE 8:
Elbow Dimensions
Elbow
A Dimension (Illustrated in Figure 21)
2 in. Standard
2-5/16 in.
3 in. Standard
3-1/16 in.
2 in. Sweep
3-1/4 in.
3 in. Sweep
4-1/16 in.
TABLE 9:
Equivalent Length of Fittings
Fitting
Equivalent Length
2 in. 90° sweep elbow
5 ft of 2 in. pipe
2 in. 45° sweep elbow
2-1/2 ft of 2 in. pipe
2 in. 90° standard elbow
7 ft of 2 in. pipe
2 in. 45° standard elbow
3-1/2 ft of 2 in. pipe
3 in. 90° sweep elbow
5 ft of 3 in. pipe
3 in. 45° sweep elbow
2-1/2 ft of 3 in. pipe
3 in. 90° standard elbow
7 ft of 3 in. pipe
3 in. 45° standard elbow
3-1/2 ft of 3 in. pipe
4 in. 90° elbow (sweep or standard)
5 ft of 4 in. pipe
4 in. 45° elbow (sweep or standard)
2-1/2 ft of 4 in. pipe
2 in. corrugated connector
10 ft of 2 in. pipe
3 in. corrugated connector
10 ft of 3 in. pipe
4 in. corrugated connector
10 ft of 4 in. pipe
32 ft of 2 in. pipe =
32 equivalent ft
5 - 90º standard 2 in. elbows = (5 x 7) =
35 equivalent ft
Total =
67 equivalent ft of 2 in. pipe
32 ft of 2 in. pipe =
32 equivalent ft
5 - 90º sweep 2 in. elbows = (5 x 5) =
25 equivalent ft
Total =
57 equivalent ft of 2 in. pipe
32 ft of 3 in. pipe =
32 equivalent ft
5 - 90º standard 3 in. elbows = (5 x 7) =
35 equivalent ft
Total =
67 equivalent ft of 3 in. pipe
$
$
$
$
67$1'$5'(/%2:
/21*6:((3(/%2:
$
TABLE 10:
Combustion Air Intake and Vent Connection Size at Furnace
(All Models)
FURNACE VENT CONNECTION SIZES
Furnace Input
All
Intake Pipe Size
2 in. (5.1 cm)
Vent Pipe Size
2 in. (5.1 cm)
IMPORTANT:
Furnace vent pipe connections are sized for 2 in.
(5.1 cm). pipe. Any pipe size change must be made outside the fur-
nace casing in a vertical pipe section to allow proper drainage of
condensate. An offset using two 45º (degree) elbows is required for
plenum clearance when the vent is increased to 3 in. (7.6 cm).
IMPORTANT:
Accessory concentric vent/intake termination kits
1CT0302 and 1CT0303, and for Canadian applications 1CT0302-
636 and 1CT0303-636 are available and approved for use with
these furnaces. Horizontal sidewall vent terminations kits 1HT0901
and 1HT0902 are also approved for use with these furnaces.
CAUTION
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.
IMPORTANT:
The vent must be installed with the minimum
required clearances, and must comply with local codes and require-
ments.
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