Munchkin 399M - Manual (Page 13)

13
D. EXHAUST VENT AND INTAKE AIR PIPE
SIZING
1. For the 399M the exhaust vent and air intake
pipes should be 4" Schedule 40 or 80.
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 4.1.
b. For example: If the exhaust vent has two 90°
elbows and 10 feet of PVC pipe we will cal-
culate:
Exhaust Vent Pipe Equivalent Length = (2x5)+10=20 feet
Further, if the intake air pipe has two 90°
elbows, one 45° elbow and 10 feet of PVC
pipe, the following calculation applies:
Air Intake 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 pipe and the exhaust vent are
intended to penetrate the same wall or roof
of the building.
d. Effort should be made to keep a minimum
difference in equivalent length between the
air intake pipe and the exhaust vent.
4. The minimum combined equivalent length is
16 equivalent feet.
5. The maximum combined equivalent length
can be extended by increasing the diameter
of the vent pipe. However, the transitions
should begin a minimum of 15 equivalent feet
from the boiler.
a. Transitions should always be made in verti-
cal sections of pipe to prevent the conden-
sate from pooling in the vent pipe.
b. Use a 6” x 4” reducing coupling to transition
from the 399M boiler connections to 6”
vent.
c. The maximum equivalent length for the
increased diameter vent pipes is 125 feet.
d. If the transition occurs at a distance greater
than 15 equivalent feet from the boiler, the
maximum equivalent length will be reduced.
See Table 4.2. Standard Vent Pipe is 4" and
Oversized Vent Pipe is 6" for the 399M.
E. EXHAUST VENT AND AIR INTAKE PIPE
INSTALLATION
1. On the 399M Boiler the 4" exhaust vent con-
nection is located at the rear of the boiler and
the air intake is higher and toward the left side
when the boiler is viewed from the front. The
air intake connection is intended for a slip fit.
No sealant or adhesive is required.
2. Use only solid PVC, CPVC, or ABS schedule
40 or 80 pipe. FOAM CORE PIPING IS NOT
APPROVED.
3. Remove all burrs and debris from joints and
fittings.
4. 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 or CPVC pipe and ASTM D2235 for ABS
pipe.
VENTING
Transition
Point
(ft from
boiler
TEL of
Standard 2"
or 3" Vent
Pipe (ft)
TEL of
Oversized 3"
or 4" Vent
Pipe (ft)
Maximum
TEL of all
Vent Pipe (ft)
15 30 95 125
20 40 77-1/2 117-1/2
25 50 60-1/2 110-1/2
30 60 43 103
35 70 26 96
40 80 8-1/2 88-1/2
None 85 0 85
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING EQUIVALENT FEET
4" 6"
90 DEGREE ELBOW* 3' 1'
45 DEGREE ELBOW 1' 1'
COUPLING 0' 0'
AIR INLET TEE 0' 0'
STRAIGHT PIPE 1' 0.5'
V2000 4" VENT KIT 1' N/A
Table 4.2: Vent Termination Kits
Table 4.1
TEL = Total Equivalent Length
*Friction loss for long radius elbow is 1 foot less