Termination
The vent terminal should be vertical and should termi- nate outside the building at least 2 ft above the highest point of the roof that is within 10 ft. The vent cap should have a minimum clearance of 4 ft horizontally from and in no case above or below (unless a 4 ft hori- zontal distance is maintained) electric meters, gas meters, regulators and relief equipment. The distance of the vent terminal from adjacent public walkways, adjacent buildings, open windows and building open- ings must be consistent with the NFGC (U.S.) or B149 (Canada). Gas vents supported only by flashing and extended above the roof more than 5 ft should be se- curely guyed or braced to withstand snow and wind loads.
CAUTION: A listed vent cap terminal, adequately sized, must be used to evacuate the flue products from the heaters.
Common Venting System
Manifolds that connect more than one heater to a com- mon chimney must be sized to handle the combined 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 | Air Inlet | |||
Model | Venting | Vent Size | Height* | Intake Pipe | Max. Length** | |||
| Material |
| Min. | Max. | Material |
| 6” | 8” |
|
|
|
|
| ||||
|
|
|
|
|
|
|
|
|
302B |
| 5” |
|
|
|
| 100’ | N/A |
|
|
|
|
|
|
| ||
402B |
| 6” |
|
| Galvanized Steel, |
| ||
|
|
|
|
|
| |||
| Cat. I |
|
|
|
|
| ||
502B |
|
|
| 75’ |
| |||
|
|
| PVC, |
|
| |||
(Type B |
| 5’ | 25’ |
|
| |||
652B |
| ABS, |
|
|
| |||
Equivalent) |
|
|
|
|
|
| ||
|
|
| CPVC |
|
| 100’ | ||
752B |
| 8” |
|
|
| 40’ | ||
|
|
|
|
|
| |||
|
|
|
|
|
|
|
|
|
902B |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
*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 N: Category I Vertical Venting
29
