8.2 Maximum Allowed Remote Combustion Air Inlet Length (Equivalent Length)
A vertical or horizontal remote air inlet system can be connected to this appliance without modification. The maximum length of field supplied single wall pipe, such as galvanized ventilation pipe, is shown in the chart below titled Maximum Air Inlet Duct Equivalent Length. Use metal tape or RTV sealant to seal each pipe joint.
Maximum Air Inlet Duct Equivalent Length
Duct Size | 6” Duct | 7” Duct | 8” Duct | 9” Duct |
Max Equivalent Length | 100 feet | 130 feet | 250 feet | 450 feet |
To determine the maximum straight length of duct allowed, use the Duct Fitting Equivalent Length chart below to find the total equivalent length for all duct fittings in your combustion air system. Then subtract this number of feet from the total equivalent length allowed in Maximum Air Inlet Duct Equivalent Length chart above. The sum of this calculation is the maximum length of straight duct allowed. If a longer length is required, repeat the calculation using a larger duct size. No additional deduction is required for the addition of the duct system terminal.
Duct Fitting Equivalent Length
| Duct Pipe: | 6” Duct | 7” Duct | 8” Duct | 9” Duct |
90º | Elbow | 8 feet | 9 feet | 10 feet | 11 feet |
90º | Long Radius Elbow | 5 feet | 5 feet | 5 feet | 6 feet |
45º | Elbow | 5 feet | 5 feet | 5 feet | 5 feet |
The following remote air duct information is provided for use in design calculations, if needed.
Remote Air Duct Specifications
Input MBtu | Required Air (SCFM) |
399 | 87 |
500 | 108 |
750 | 163 |
900 | 195 |
1000 | 217 |
8.3Remote Combustion Air Cap
A UL Listed air intake vent termination cap MUST be attached to the remote combustion air vent termination to adequately protect the combustion air inlet from wind and weather. A UL Listed air intake termination cap is available from PVI Industries and may have shipped with the water heater as a purchased option.
8.4Vertical or Horizontal Remote Air Duct Termination
∙Air inlet and exhaust vents should terminate in the same wind pressure area whenever possible.
∙Air inlet must be located no less than 3 feet (0.91m) below the exhaust terminal if they are within 10 feet (3.05 m) of each other.
∙If terminating through the roof, the air inlet must terminate at least 12 inches (0.3 m) above roof level and at least 12 inches (0.3 m) above snow levels.
∙If terminating through a sidewall, the air inlet must terminate at least 12 inches (0.3 m) above grade and/or at least 12 inches (0.3 m) above normal snow levels.
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