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D. EXHAUST VENT AND INTAKE AIR PIPE
SIZING
1. For the 399VWH the exhaust vent and air
intake pipes should be 4" and 3" for the
199VWH.
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 4.1.
Table 4.1
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING
90 DEGREE ELBOW
45 DEGREE ELBOW
COUPLING
AIR INLET TEE
STRAIGHT PIPE
V1000 4" VENT KIT
V2000 4" VENT KIT
CONCENTRIC VENT KIT
*Friction loss for long elbow is 1 foot less.
b. For example: If the exhaust vent has two 90°
elbows and 10 feet of PVC pipe we will cal-
culate:
Exhaust Vent Pipe Equivalent Length = (2x5)+10=20 feet
Further, if the intake air pipe has two 90°
elbows, one 45° elbow and 10 feet of PVC
pipe, the following calculation applies:
Air Intake Pipe Equivalent Length = (2x5)+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 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
air intake pipe and the exhaust vent.
4. The minimum combined equivalent length is
16 equivalent feet.
5. The maximum combined equivalent length
can be extended by increasing the diameter
of the vent pipe. However, the transitions
should begin a minimum of 15 equivalent feet
from the boiler.
a. Transitions should always be made in verti-
cal sections of pipe to prevent the conden-
sate from pooling in the vent pipe.
EQUIVALENT FEET
3"
4"
6"
5'
3'
1'
3'
1'
1'
0'
0'
0'
0'
0'
0'
1'
1'
0.5'
1'
1'
N/A
N/A
1'
1'
3'
N/A
N/A
b. Use a 6" x 4" reducing coupling to transition
from the 399VWH boiler connections to 6"
vent.
c. The maximum equivalent length for the
increased diameter vent pipes is 125 feet.
d. If the transition occurs at a distance greater
than 15 equivalent feet from the boiler, the
maximum equivalent length will be reduced.
See Table 4.2. Standard Vent Pipe is 4" and
Oversized Vent Pipe is 6" for the 399VWH.
Table 4.2: Vent Termination Kits
Transition
TEL of
Point
Standard
(ft from
3" Vent
boiler)
Pipe (ft)
15
30
20
40
25
50
30
60
35
70
40
80
None
85
TEL = Total Equivalent Length
E. EXHAUST VENT AND AIR INTAKE PIPE
INSTALLATION
1. On the 399VWH Boiler the 4" exhaust vent
connection is located at the rear of the boiler
and the air intake is higher and toward the left
side when the boiler is viewed from the front.
The air intake connection is intended for a slip
fit. No sealant or adhesive is required.
2. See Approved Venting Materials, page 11.
n
WARNING
All joints of positive pressure vent systems must be
sealed completely to prevent leakage of flue
products into the living space.
3. Horizontal lengths of exhaust vent must slope
back towards the boiler not less than ¼" per
foot to allow condensate to drain from the
vent pipe. If the vent pipe must be piped
around an obstacle that causes a low point in
the pipe, a drain pipe must be connected to
allow condensate to drain.
4. All piping must be fully supported. Use pipe
hangers at a minimum of 4 foot intervals to
prevent sagging of the pipe where conden-
sate may form.
5. Do not use the boiler to support any piping.
6. A screened straight coupling is provided with
the boiler for use as an outside exhaust termi-
nation.
VENTING
TEL of
Maximum
Oversized 3"
TEL of all
or 4" Vent
Vent Pipe (ft)
Pipe (ft)
95
125
77-1/2
117-1/2
60-1/2
110-1/2
43
103
26
96
8-1/2
88-1/2
0
85
15
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