E. exhaust vent and intake pipe sizing, G. longer vent runs – HTP 399M User Manual
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E. EXHAUST VENT AND INTAKE PIPE SIZING
1. The exhaust vent and intake pipe size is 2"
for the T50/80, 3” for the 80/140/199M, and 4” for the 399M.
2. The total equivalent length of exhaust vent and intake pipe should
not exceed 85’.
a. The equivalent length of elbows, tees, and other fittings are listed in the Friction Loss Table below:
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING
EQUIVALENT FEET
2”
3”
4”
6”
90 DEGREE ELBOW*
5’
5’
3’
3’
45 DEGREE ELBOW
3’
3’
1’
1’
COUPLING
0’
0’
0’
0’
AIR INLET TEE
0’
0’
0’
0’
STRAIGHT PIPE
1’
1’
1’
1’
CONCENTRIC VENT KIT
3’
3’
N/A
N/A
V500 2” VENT KIT
1’
N/A
N/A
N/A
V1000 3” VENT KIT
N/A
1’
1’
1’
V2000 4” VENT KIT
N/A
1’
1’
1’
Table 5 - *Friction loss for long radius elbow is 1 foot less. NOTE: Consult Polypropylene venting instructions for friction loss and pressure
drop equivalents.
b. For example: If the exhaust vent has two 90° elbows and 10 feet of PVC pipe we will calculate:
Exhaust Vent Equivalent Length = (2 x 5) + 10 = 20 feet.
Further, if the intake pipe has two 90° elbows, one 45° elbow and 10 feet of PVC pipe, the following calculation applies:
Intake Pipe Equivalent Length = (2 x 5) + 3 + 10 = 23 feet.
Finally, if a concentric vent kit is used we find:
Total Equivalent Length = 20 + 23 + 3 = 46 feet.
The total equivalent length is 46 feet, which is well below the maximum of 85 feet.
c. The exhaust vent and intake pipe 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 exhaust vent and intake pipe.
3. The minimum total equivalent length is 32 equivalent feet.
G. LONGER VENT RUNS
The maximum total equivalent length can be extended by increasing the diameter of both exhaust vent and intake pipe equally.
However, the transitions should begin a minimum of 15 equivalent feet from the boiler.
a. Transitions should always be made in vertical sections of pipe to prevent the condensate from pooling in the vent pipe.
b. The maximum equivalent length for increased diameter vent pipes is 125 feet.
VENT CONNECTION
REDUCING COUPLING
VENT TRANSITION
2”
3” X 2”
3”
3”
4” X 3”
4”
4”
6” X 4”
6”
Table 6
– Reducing Couplings
c. If the transition occurs at a distance greater than 15 equivalent feet from the boiler, the maximum equivalent length will be
reduced. See
. The standard ven
t pipe is 2”.
TRANSITION POINT (FT.
FROM BOILER)
TEL
OF STANDARD 2”
VENT PIPE (FT.)
TEL
OF OVERSIZED 2”, 3”, OR
4” VENT PIPE (FT.)
MAXIMUM TEL OF ALL VENT
PIPE (FT.)
15
30
95
125
20
40
77-1/2
117-1/2
25
50
60-1/2
110-1/2
30
60
43
103
35
70
26
96
40
80
8-1/2
88-1/2
NONE
85
0
85
Table 7