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E. Exhaust Vent and Intake Pipe Sizing
1. The exhaust vent and intake pipe size is 3" for 220 models and 4" for
299 - 399 models.
2. The maximum total equivalent length of exhaust vent and intake
pipe should not exceed 200 feet.
a. The equivalent length of elbows, tees, and other fittings are
listed in the Friction Loss Table.
Friction Loss Equivalent in Piping and Fittings
Fittings or Piping
90 Degree Elbow*
45 Degree Elbow
Coupling
Air Inlet Tee
Straight Pipe
Concentric Kit
V Series Vent Kit
AL20 4c Vent Terminal
Table 16 - *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 is 3" in diameter, has two 90
elbows, and 10 feet of PVC pipe we will calculate:
Exhaust Vent Equivalent Length = (2x5) + 10 = 20 feet.
Further, if the 3" intake pipe has two 90
and 10 feet of PVC pipe, the following calculation applies:
Intake Pipe Equivalent Length = (2x5) + 3 + 10 = 23 feet.
The total equivalent length is 43 feet, well below the maximum of
200 feet.
c. 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 16 feet.
Do not exceed the maximum lengths for vent pipes. Excessive length
could result in boiler shutdown and property damage.
Failure to provide a minimum total vent length of 16 equivalent feet
could result in property damage and improper product operation.
F. Longer Vent Runs
The maximum total equivalent length can be extended by increasing
the diameter of both the exhaust vent and intake pipes equally.
However, the transitions should begin a minimum of 16 equivalent
feet from the boiler. Transitions should always be made in vertical
sections of pipe to prevent the condensate from pooling in the vent
pipe.
The maximum equivalent length for increased diameter vent pipes is
275 ft, which includes 16 ft from with boiler with a transition total of
259 ft upsize piping for longer vent runs.
Figure 12 - Extended Vent Runs
WHL-053 Rev. 00 Rel. 003 Date 7.21.17
Equivalent Feet
3"
4"
6"
5'
3'
3'
3'
3'
2'
0'
0'
0'
0'
0'
0'
1'
1'
1'
3'
N/A
N/A
1'
1'
1'
1'
1'
1'
o
o
elbows, one 45
elbow,
Standard
Vent Connection and
Maximum Total
Equivalent Length
3" (200')
4" (200')
6" (200')
Table 17 - Vent Run Transition
Total maximum equivalent length of increased diameter exhaust
vent and intake pipe must not exceed the lengths defined in this
manual. Failure to keep the total equivalent length below the
maximum lengths determined in this manual will result in faulty
boiler operation, substantial property damage, serious personal
injury, or death.
G. Exhaust Vent and Intake Pipe Installation
All joints of positive pressure vent systems must be sealed
completely to prevent leakage of flue products into the living
space. Failure to do so could result in property damage, serious
injury, or death.
o
1. Use only solid PVC, CPVC, or stainless steel pipe or a Polypropylene
vent system approved for use with Category IV appliances.
FOAM CORE PIPING IS NOT APPROVED FOR EXHAUST VENT
APPLICATIONS. Foam core piping may be used on air inlet piping
only.
2. Remove all burrs and debris from joints and fittings.
3. When using PVC or CPVC pipe, 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. NOTE: DO NOT CEMENT
POLYPROPYLENE PIPE.
4. Ensure the vent is located where it will not be exposed to
prevailing winds.
5. In all roof venting applications, exhaust discharge must point
away from the pitch of the roof.
6. If the exhaust vent is to be terminated in a walled off area (such
as a roof with a parapet wall), ensure the exhaust vent terminates
a minimum of 10' from nearest wall and extends level with or
above the top of the wall. This will ensure flue gas does does not
get trapped and possibly recirculated into the intake air pipe, which
could contaminate the combustion air.
7. To prevent water leakage, install adequate roof flashing where the
pipe enters the roof.
8. Do not locate vent over public walkways, driveways, or parking
lots. Condensate could drip and freeze, resulting in a slip hazard or
damage to vehicles and machinery.
9. Due to potential moisture build-up, sidewall venting may not
be the preferred venting option. To save time and cost, carefully
consider venting installation and location.
10. 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.
11. The exhaust vent must terminate where vapors cannot make
accidental contact with people or pets, or damage shrubs or plants.
12. In vacant chimney applications, install and seal a rain cap over
existing chimney openings.
13. All piping must be fully supported. Use pipe hangers at a
minimum of 4 foot intervals to prevent sagging of the pipe where
condensate may form.
14. Do not use the boiler to support any piping.
Increased Vent Size
Reducing
and Maximum Total
Coupling
Equivalent Length
4" x 3"
4" (275')
6" x 4"
6" (275')
8" x 6"
8" (275')
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