Boiler Manual |
PART 7: VENTING, COMBUSTION AIR & CONDENSATE REMOVAL (CONTINUED)
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 7.5.
Table 7.5
FRICTION LOSS EQUIVALENT IN PIPING AND FITTINGS
FITTINGS OR PIPING |
| EQUIVALENT FEET |
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| 2" |
| 3" | 4" |
| 6" |
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90 DEGREE ELBOW* | 5' |
| 5' | 3' |
| 3' |
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45 DEGREE ELBOW | 3' |
| 3' | 1' |
| 1' |
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COUPLING | 0' |
| 0' | 0' |
| 0' |
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AIR INLET TEE | 0' |
| 0' | 0' |
| 0' |
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STRAIGHT PIPE | 1' |
| 1' | 1' |
| 1' |
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CONCENTRIC VENT KIT | 3' |
| 3' | N/A |
| N/A |
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V500 2" VENT KIT | 1' |
| N/A | N/A |
| N/A |
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V1000 3" VENT KIT | N/A |
| 1' | 1' |
| 1' |
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V2000 4" VENT KIT | N/A |
| 1' | 1' |
| 1' |
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*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.
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 7.6: Vent Run Transition
Vent | Reducing | Vent |
Connection | Coupling | Transition |
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2" | 3" x 2" | 3" |
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3" | 4" x 3" | 4" |
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4" | 6" x 4" | 6" |
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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 7.7.
Table 7.7: Vent Termination Kits
Transition | TEL of | TEL of | Maximum | |
Point | Standard | Oversized | ||
TEL of all | ||||
(ft from | 2" Vent | 2", 3" or 4" | ||
Vent Pipe (ft) | ||||
boiler) | Pipe (ft) | Vent Pipe (ft) | ||
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15 | 30 | 95 | 125 | |
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20 | 40 | |||
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25 | 50 | |||
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30 | 60 | 43 | 103 | |
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35 | 70 | 26 | 96 | |
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40 | 80 | |||
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None | 85 | 0 | 85 | |
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TEL = Total Equivalent Length
G. EXHAUST VENT AND INTAKE AIR PIPE
INSTALLATION
1. Use only solid PVC, CPVC, or ABS schedule
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