Rinnai RH180 Installation Fundamentals page 26

Vent Guidelines: Combustion air
Using Indoor Air For Combustion:
When using air from other room(s) in the building, the total volume of the room(s) must be of
adequate volume (Greater than 50 cubic feet per 1,000 Btu/hr.). Each combustion air opening
must have at least one square inch of free area for each 1,000 Btu/hr, but not less than 100 square
inches each.
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