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D. EXHAUST VENT AND INTAKE AIR VENT SIZING
1.
The exhaust and intake vent size is 2" for the HE100
and HE130 and 3" for the HE199.
2.
The total combined equivalent length of exhaust vent
and intake air pipe should not exceed 85 feet.
a. The equivalent length of elbows, tees, and other
fittings are listed in the Friction Loss Table 3-5.
Table 3-5
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING
90 DEGREE ELBOW*
45 DEGREE ELBOW
COUPLING
AIR INLET TEE
STRAIGHT PIPE
CONCENTRIC VENT KIT SP12161
V1100 3" VENT KIT SP12162
-
*Friction loss for long radius elbow is 1 foot less
b. For example: If the exhaust vent has two 90°
elbows and 10 feet of PVC pipe we will calculate:
Exhaust Vent Pipe Equivalent Length = (2×5)+10=20 feet
Further, if the intake air vent pipe has two 90°
elbows, one 45° elbow and 10 feet of PVC pipe,
the following calculation applies:
Intake Air Vent Pipe Equivalent Length = (2×5)+3+10=23 feet
Finally, if a concentric vent kit is used we find:
Total Combined Equivalent Length = 20+23+3=46 feet
Therefore, the total combined equivalent length
is 46 feet which is well below the maximum of 85
feet.
c. The intake air vent pipe and the exhaust vent are
intended to penetrate the same wall or roof of the
building.
d. Effort should be made to keep a minimum
difference in equivalent length between the
intake air vent pipe and the exhaust vent.
3.
The minimum combined equivalent length is 16
equivalent feet.
EQUIVALENT FEET
2" (5 cm)
3" (7.6 cm) 4" (10 cm)
5' (1.5 m)
5' (1.5 m)
3' (.92 m)
3' (.92 m)
3' (.92 m)
1' (.31 m)
0'
0'
0'
0'
0'
0'
1' (.31 m)
1' (.31 m)
1' (.31 m)
N/A
3' (.92 m)
N/A
N/A
1' (.31m)
N/A
(.61m×1.5m)+3m=6.1m
(.61m×1.5m)+.92m+3m=7m
.61m+7m+.92m=14m
E. LONGER VENT RUNS
1.
The maximum combined equivalent length can be
extended by increasing the diameter of both exhaust
vent and intake air vent pipe equally. However, the
transitions should begin a minimum of 15 equivalent
feet from the water heater.
a. The maximum equivalent length for the
increased diameter vent pipes is 125 feet.
b. Transitions should always be made in vertical
sections of pipe to prevent the condensate from
pooling in the vent pipe.
Table 3-6: Vent Run Transition
Vent
Connection
2" (5 cm)
3" × 2" (7.6 cm × 5 cm)
3" (7.6 cm)
4" × 3" (10 cm × 7.6 cm)
c. If the transition occurs at a distance greater than
15 equivalent feet from the water heater, the
maximum equivalent length will be reduced. See
Table 3-7.
Table 3-7: Vent Termination Kits
Transition
TEL of
Point
Standard
(ft from
2" Vent
water heater)
Pipe (ft)
15 (4.58 m)
30 (9.1 m)
20 (6 m)
40 (12.2 m) 77-1/2 (23.6 m) 117-1/2 (35.9 m)
25 (7.6 m)
50 (15.2 m) 60-1/2 (18.4 m) 110-1/2 (33.7 m)
30 (9.1 m)
60 (18.2 m)
35 (10.7 m)
70 (21.3 m)
40 (12.2 m)
80 (24.3 m)
None
85 (27 m)
TEL = Total Equivalent Length
F. EXHAUST VENT AND INTAKE AIR PIPE
INSTALLATION
1.
Use only solid PVC or CPVC for exhaust vent pipe.
FOAM CORE PIPING, as well as PVC and CPVC,
can be used for the intake vent pipe. Refer to chart
Section 3B, Page 11.
2.
Remove all burrs and debris from joints and fittings.
3.
All joints must be properly cleaned, primed, and
cemented. Use only cement and primer approved
for use with the pipe material. Cement must conform
to ASTM D2564 for PVC and ASTM F493 for CPVC
pipe.
n
All joints of positive pressure vent systems must be
sealed completely to prevent leakage of flue products
into the living space.
14
Reducing
Coupling
Transition
3" (7.6 cm)
4" (10 cm)
TEL of
Maximum TEL
Oversized
2", 3" or 4"
Vent Pipe (ft)
Vent Pipe (ft)
95 (29 m)
125 (38 m)
43 (13.1 m)
103 (31.4 m)
26 (7.92 m)
96 (29.2 m)
8-1/2 (2.6 m)
88-1/2 (27 m)
0
85 (26 m)
WARNING
Vent
of all
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