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WHL-038 Rev. 1.29.16
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Friction Loss Equivalent in Piping and Fittings
Fittings or Piping
Equivalent Feet
6” 8”
90 Degree Elbow* 3’ 3’
45 Degree Elbow 1’ 1’
Coupling 0’ 0’
Air Inlet Tee 0’ 0’
Straight Pipe 1’ 1’
V Series Vent Kit 1’ 1’
AL29 4c Vent Terminal 1’ 1’
Table 9 - *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 6” in diameter, has two
90
o
elbows, and 10 feet of PVC pipe we will calculate:
Exhaust Vent Equivalent Length = (2x3) + 10 = 16 feet.
Further, if the 6” intake pipe has two 90
o
elbows, one 45
o
elbow, and 10 feet of PVC pipe, the following calculation
applies:
Intake Pipe Equivalent Length = (2x3) + 1 + 10 = 17 feet.
The total equivalent length is 33 feet, well below the
maximum of 140 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.
F. 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.
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
Failure to provide a minimum total vent length of 16 equivalent
feet could result in property damage and improper product
operation.
E. Exhaust Vent and Intake Pipe Sizing
1. The exhaust vent and intake pipe size is 6”.
2. The maximum total equivalent length of exhaust vent and
intake pipe
should not exceed 140 feet .
a. The equivalent length of elbows, tees, and other fittings
are listed in the Friction Loss Table.
Total maximum equivalent length of 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.
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 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.
15. Ensure the outdoor exhaust vent termination is screened
to prevent blockage caused by debris or birds.
16. Ensure the outdoor intake pipe termination is screened to
prevent blockage caused by debris or birds.
G. Applications
1. Direct Vent Installation of Exhaust and Intake
If installing a direct vent option, combustion air must be
drawn from the outdoors directly into the boiler intake, and
exhaust must terminate outside. There are three basic direct
vent options detailed in this manual: 1. Side Wall Venting, 2.
Roof Venting, and 3. Unbalanced Venting.
Be sure to locate the boiler such that the exhaust vent and
intake pipe can be routed through the building and properly
terminated. Different vent terminals can be used to simplify
and eliminate multiple penetrations in the building structure
(see Optional Equipment in Venting Section). The exhaust
vent and intake pipe lengths, routing and termination
methods must all comply with the methods and limits given
in the Venting section of this manual.
When installing a combustion air intake from outdoors, care
must be taken to utilize uncontaminated combustion air.
NOTE: To prevent combustion air contamination, see Table 1.