Rinnai RH180 Installation Fundamentals page 24

Vent Guidelines: Combustion air
Confined and Unconfined space examples:
25 x 25 x 8 = 5000 cubic feet
5000 cubic feet
100 x 1000 = 100,000 Btu
Unconfined space with a 91,300 Btu water
heater.
24
50 = 100
25 x 25 x 8 = 5000 cubic feet
5000 cubic feet
100 x 1000 = 100,000 Btu
Confined space with 91,300 Btu water
heater and a 100,000 btu furnace. Total =
191,300 Btu.
50 = 100