HTP MC120 - Manual (Page 45)

45
LP-171 Rev. 4.10.14
2. Inspect the area where the white flue adapter mates to the black plastic heat exchanger. You will notice two red wires and a plastic
hose connected to the flue adapter. These will limit the rotation range of the flue adapter.
3. Grasp the entire white PVC flue adapter and rotate it in the direction that will cause the least strain on the hose and red wires until
the air inlet is in the desired orientation. After rotation is complete, push downward on the flue adapter to be sure it is completely seated
in the black plastic module.
4. Check again to make sure the red wires and clear plastic hose connected to the flue adapter are properly connected and routed.
F. EXHAUST VENT AND INTAKE PIPE SIZING
1. The exhaust vent and intake pipe size is 2" or greater.
2. The total equivalent length of exhaust vent and intake pipe should
not exceed 85’ for 2” and 125’ for 3”.
a. The equivalent length of elbows, tees, and other fittings are listed in the Friction Loss Table below:
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING
EQUIVALENT FEET
2” 3”
90 DEGREE ELBOW* 5’ 5’
45 DEGREE ELBOW 3’ 3’
COUPLING 0’ 0’
AIR INLET TEE 0’ 0’
STRAIGHT PIPE 1’ 1’
CONCENTRIC VENT KIT 3’ 3’
V500 2’ VENT KIT 1’ N/A
V1000 3’ VENT KIT N/A 1’
Table 5 - *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° elbows and 10 feet of PVC pipe we will calculate:
Exhaust Vent Equivalent Length = (2 x 5) + 10 = 20 feet.
Further, if the intake pipe has two 90° elbows, one 45° elbow and 10 feet of PVC pipe, the following calculation applies:
Intake Pipe Equivalent Length = (2 x 5) + 3 + 10 = 23 feet.
Finally, if a concentric vent kit is used we find:
Total Equivalent Length = 20 + 23 + 3 = 46 feet.
Therefore, the total equivalent length is 46 feet which is well below the maximum of 85 feet.
c. The exhaust vent and intake pipe 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 exhaust vent and intake pipe.
3. The minimum total equivalent length is 32 equivalent feet.
G. LONGER VENT RUNS
The maximum total equivalent length can be extended by increasing the diameter of both exhaust vent and intake pipe equally.
However, the transitions should begin a minimum of 15 equivalent feet from the heater.
a. Transitions should always be made in vertical sections of pipe to prevent the condensate from pooling in the vent pipe.
b. Use a 3” x 2” reducing coupling to transition from the 2” connections to a 3” 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 heater, the maximum equivalent length will be
reduced. See Table 6
. The standard vent pipe is 2”.
TRANSITION POINT (FT.
FROM HEATER)
TEL OF STANDARD 2”
VENT PIPE (FT.)
TEL OF OVERSIZED 2”, 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
Table 6