LP-314 Rev. 012 Rel. 003 Date 9.27.19
23
Friction Loss Equivalent in Piping and Fittings
Fittings or Piping
Equivalent Feet
2”
3”
4”
90 Degree Elbow*
5’
5’
3’
45 Degree Elbow
3’
3’
1’
Coupling
0’
0’
0’
Air Inlet Tee
0’
0’
0’
Straight Pipe
1’
1’
1’
Concentric Kit
3’
3’
N/A
V500 2” Kit
1’
N/A
N/A
V1000 3” Kit
N/A
1’
1’
V2000 4” Kit
N/A
1’
1’
Table 6 - *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
o
elbows and 10 feet
of PVC pipe we will calculate:
Exhaust Vent Equivalent Length = (2x5) + 10 = 20 feet.
Further, if the 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 = (2x5) + 3 + 10 = 23 feet.
Finally, if a concentric kit is used we find:
Total Equivalent Length = 20 + 23 + 3 = 46 feet.
The total equivalent length is 46 feet, well below the maximum of
85 feet for 2” pipe.
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 15 equivalent
feet from the appliance.
a. The maximum total equivalent length for increased diameter
vent pipes is 125 feet for 2” transitioning to 3” pipe (this length
includes the minimum 15 total equivalent feet necessary for
transition).
NOTE:
3” vent pipe can be increased in diameter, but total
equivalent length cannot be increased beyond 200 feet.
b. Transitions should always be made in vertical sections of pipe to
prevent the condensate from pooling in the vent pipe.
Standard
Vent Connection and
Maximum Total
Equivalent Length
Reducing
Coupling
Increased Vent Size
and Maximum Total
Equivalent Length
2” (85’)
3” x 2”
3” (125’)
3” (200’)
4”x 3”
4” (200’)
Table 7 - Vent Run Transition
c. If transition occurs at a distance greater than 15 equivalent
feet from the appliance, the maximum equivalent length will be
reduced.
Do not exceed the maximum lengths for vent pipes. Excessive length
could result in appliance 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 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
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 2” for 130kBTU models and
3” for 199kBTU models.
2. The maximum total equivalent length of 2” exhaust vent and intake
pipe
should not exceed 85 feet
. The maximum total equivalent
length of 3” 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. 125 maximum total equivalent feet for 2” increased to 3”
vent pipe; 200 maximum total equivalent feet for any increase to
3” vent pipe diameter. Failure to keep the total equivalent length
below the maximum lengths determined in this manual will
result in faulty appliance operation, substantial property damage,
serious personal injury, or death.
Transition
Point (Ft. from
Appliance)
TEL of Oversized
Vent Pipe (Ft.)*
Maximum TEL of
all Vent Pipe (Ft.)
15
95
125
20
77 1/2
117 1/2
25
60 1/2
110 1/2
30
43
103
35
26
96
40
8 1/2
88 1/2
NONE
0
85
Table 8 - TEL = Total Equivalent Length *Oversized vent pipe diameter is
1” or greater than factory supplied connection.
