8.11 Outside Combustion Air Supply
IMPORTANT: If the building has a slight negative pressure or corrosive contaminants, such as haloge- nated hydrocarbons, are present in the air, an outside combustion air supply to the heater is required. Seal all combustion air pipe joints.
Use of optional outside combustion air is not recom-
mended with unvented heaters.
The air supply duct may have to be insulated to pre- vent condensation on the outer surface. The outside air terminal must not be more than 1' (31 cm) above the vent terminal.
8.11.1 Length Requirements
Follow the constraints listed on Page 35, Section 8.6.
8.11.2 Vertical Outside Air Supply for Single Heater Installation
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| Description | Part Number |
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| Vent Cap 4" (10 cm) | 90502300 |
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8.11.3 Horizontal Outside Air Supply for Single Heater Installation
Vent Cap
| 4" (10 cm) |
Wall | Single Wall Pipe |
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| Flex Hose |
| (Recommended) |
| Burner |
| Band Clamp |
| (Recommended) |
Description | Part Number |
Vent Cap 4" (10 cm) | 90502300 |
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