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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.
Air Duct Specifications
Boiler Input Mbtu
Required Air (SCFM)
399 87
500 108
650 141
750 163
850 184
900 195
1000 217
6.3 Remote 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 Riverside Hydronics and may have shipped with the boiler as a purchased option.
6.4 Vertical 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.
Vertical Remote Air (recommended)
Horizontal Remote Air (allowed)
6.5
Remote Air Consideration for Combined Remote Air Ducting
Each boiler MUST have separate intake piping. Consult factory for common air intake assistance.
