load. Consult available guides for proper sizing of the manifold and the chimney. At no time should the area of the common vent be less than the area of the largest heater exhaust outlet.
WARNING: Vent connectors serving appliances vented by natural draft shall not be connected into any portion of mechanical draft systems operating under a positive pressure.
CAUTION: Vent connectors for natural draft venting systems must be Type B or better.
Common venting systems may be too large once an existing unit is removed. At the time of removal of an existing appliance, the following steps must be fol- lowed with each appliance remaining connected to the common venting system placed in operation, while the other appliances remaining connected to the common venting system are not in operation.
1.Seal any unused opening in the common venting system.
2.Visually inspect the venting system for proper size and horizontal pitch and verify there is no block- age, restriction, leakage, corrosion or other unsafe condition.
3.Insofar as is practical, close all building doors and windows and all doors between the space in which the appliances remaining connected to the com- mon venting system are located and other spaces of the building. Turn on clothes dryers and any ap- pliance not connected to the common vent system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, at maximum
| Certified |
| Vertical Venting | Combustion |
| Air Inlet Max. Length** |
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Model | Vent | Height* | Air |
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Venting |
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No. | Size |
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| Intake Pipe |
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Material | Min. | Max. | 6” |
| 8” | 10” |
| 12” | |||
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| Material |
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399B |
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| 100’ |
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| 6” |
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499B |
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| 75’ |
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| |
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649B |
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| 100’ |
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749B |
| 8” |
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| 40’ |
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| |
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899B |
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| Category I |
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| Galvanized |
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989B | 10” |
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| Steel, |
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| (Type B |
| 5’ | 25’ |
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1259B |
| PVC, ABS, |
|
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| 75’ |
| 100’ | |||
Equivalent) |
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| CPVC |
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| 12” |
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1529B |
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1799B |
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1999B |
| 14” |
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| 40’ |
| 75’ |
2069B |
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| |
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2339B |
| 16” |
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*Vent lengths are based on a lateral length of 2 ft. Refer to the latest edition of the NFGC for further details. When vertical height exceeds 25 ft, consult factory prior to installation.
** Subtract 10 ft per elbow. Max. 3 elbows.
Maximum combustion air duct length terminated at 100 equivalent ft.
Table L: Category I Vertical Venting
29
