Combustion Air | Exhaust | Venting Category | Certified | Combustion Air |
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Supply | Configuration | Appliance Material | Inlet Material |
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| Vertical Natural |
| Type B or and |
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| I | Category I Venting |
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| Draft Venting |
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From Inside |
| System* |
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Building |
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Horizontal |
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Venting) |
| Stainless Steel |
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| III |
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| (Gas Tight) |
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| Venting |
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| Type B or and |
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| Vertical Venting | I | Category I Venting | Galvanized Steel |
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From Outside |
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| System* |
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| PVC |
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Building (Direct |
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Horizontal |
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| ABS |
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Venting) |
| Stainless Steel |
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| CPVC |
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III |
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| Venting |
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*As defined in the latest edition of the NFGC, or in Canada, the B149. |
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| Table H: Venting Category Requirements |
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Barometric Damper
A barometric damper may be required when vent heights exceed 25 feet or when the draft is greater than
The damper should be installed NO CLOSER than 18 in. from the discharge of the unit and no closer than 18 in. from a combustible ceiling. The damper can be installed in horizontal or vertical runs of vent pipe as necessary. Installation in a
The weights on the damper should be adjusted per the damper manufacturer’s instructions for proper opera- tion.
Support of Vent Stack
The weight of the vent stack or chimney must not rest on the heater vent connection. Support must be pro- vided in compliance with applicable codes. The vent should also be supported to maintain proper clear- ances from combustible materials.
Use insulated vent pipe spacers where the vent pass- es through combustible roofs and walls.
Vent Terminal Location
NOTE: During winter months check the vent cap and make sure no blockage occurs from build up of snow. Condensate can freeze on the vent cap. Frozen condensate on the vent cap can result in a blocked flue condition.
General
Give special attention to the location of the vent termi- nation to avoid possibility of property damage or personal injury.
a)Gases may form a white vapor plume in winter. The plume could obstruct a window view if the ter- mination is installed in close proximity to windows.
b)Prevailing winds could cause freezing of conden- sate and water/ice
c)The bottom of the vent terminal and the air intake shall be located at least 12 in. above grade.
d)
e)
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