lp-445-r4 Rev. 006 Rel. 027 Date 7.21.20
24
Friction Loss Equivalent in Piping and Fittings
Fittings or Piping
Equivalent Feet
4”
6”
8”
90 Degree Elbow*
3’
3’
3’
45 Degree Elbow
1’
1’
1’
Coupling
0’
0’
0’
Air Inlet Tee
0’
0’
0’
Straight Pipe
1’
1’
1’
V Series Vent Kit
1’
1’
1’
AL20 4c Vent Terminal
1’
1’
1’
Table 11 - *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 4” 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 4” 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.
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.
Standard
Vent Connection and
Maximum Total
Equivalent Length
Reducing
Coupling
Increased Vent Size
and Maximum Total
Equivalent Length
4” (200’)
6” x 4”
6” (275’)
6” (200’)
8” x 6”
8” (275’)
Table 12 - Vent Run Transition
Do not exceed the maximum lengths for vent pipes. Excessive
length could result in boiler shutdown and property damage.
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.
1. Use only solid PVC, CPVC, or stainless steel pipe or a Polypropylene
vent system approved for use with Category IV appliances.
ABS pipe material may be used on air intake 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.
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.
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 4” for the 500 model and
6” for the 700/850 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.
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.
Figure 11 - Extended Vent Runs
