Table of Contents
Advertisement
GAS-FIRED BOILER
PART 7: VENTING, COMBUSTION AIR & CONDENSATE REMOVAL
E. EXHAUST VENT AND INTAKE AIR VENT
SIZING
1. The exhaust vent and intake air vent pipes
should be 2" for the T50/T80, 3" for the
80M/140M/199M and 4" for the 399M.
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 7.6.
Table 7.6
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING
90 DEGREE ELBOW*
45 DEGREE ELBOW
COUPLING
AIR INLET TEE
STRAIGHT PIPE
CONCENTRIC VENT KIT
V500 2" VENT KIT
V1000 3" VENT KIT
V2000 4" VENT KIT
*Friction loss for long radius elbow is 1 foot less.
b. For example: If the exhaust vent has two
90° elbows and 10 feet of PVC pipe we
will calculate:
Exhaust Vent Pipe Equivalent Length = (2x5)+10=20 feet
Further, if the intake air vent pipe has two
90° elbows, one 45° elbow and 10 feet of
PVC pipe, the following calculation
applies:
Intake Air Vent 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 vent pipe and the exhaust
vent are intended to penetrate the same
wall or roof of the building.
41
EQUIVALENT FEET
6"
2"
3"
4"
3'
5'
5'
3'
1'
3'
3'
1'
0'
0'
0'
0'
0'
0'
0'
0'
1'
1'
1'
1'
N/A
3'
3'
N/A
N/A
1'
N/A
N/A
1'
N/A
1'
1'
N/A
1'
1'
1'
d. Effort should be made to keep a
minimum difference in equivalent length
between the intake air vent pipe and the
exhaust vent.
3. The minimum combined equivalent length is
16 equivalent feet.
F. LONGER VENT RUNS
1. The maximum combined equivalent length
can be extended by increasing the diameter
of both exhaust vent and intake air vent pipe
equally. However, the transitions should
begin a minimum of 15 equivalent feet from
the boiler.
a. The maximum equivalent length for the
increased diameter vent pipes is 125 feet.
b. Transitions should always be made in
vertical sections of pipe to prevent the
condensate from pooling in the vent
pipe.
Table 7.7: Vent Run Transition
Vent
Reducing
Connection
Coupling
2"
3"
4"
c. If the transition occurs at a distance
greater than 15 equivalent feet from the
boiler, the maximum equivalent length
will be reduced. See Table 7.8.
Table 7.8: Vent Termination Kits
Transition
TEL of
Point
Standard
(ft from
2" Vent
boiler)
Pipe (ft)
15
30
20
40
25
50
30
60
35
70
40
80
None
85
TEL = Total Equivalent Length
G. EXHAUST VENT AND INTAKE AIR PIPE
INSTALLATION
1. Remove all burrs and debris from joints and
fittings.
Boiler Manual
(CONTINUED)
Vent
Transition
3" x 2"
3"
4" x 3"
4"
6" x 4"
6"
TEL of
Maximum
Oversized
TEL of all
2", 3" or 4"
Vent Pipe (ft)
Vent 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
Hide quick links:
Advertisement
Table of Contents
