Max Appliance Input from Room Volume

Largest appliance BTU input a confined space supports by the standard volume method.

Run the calculator

Example

You enter

Room volume (ft³) 4000

You get

Max appliance input (by volume) 80000
Max kbtu input 80

Details, formula, and sources

Before combustion-air openings are required (the inverse of Combustion Air).

Standard volume method solved for input (inverse of combustion-air): max appliance BTU/hr = (room_volume_ft3 / 50) * 1000, since IFGC 2021 §304.5 treats a space as adequate at 50 ft^3 per 1000 BTU/hr.

IFGC 2021 (International Fuel Gas Code) / NFPA 54. §304.

Free read-only access at codes.iccsafe.org.

Estimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.

Field names used by the API: room_volume_ft3, max_btu_input, max_kbtu_input

Standard method IFGC §304.5 volume rule; above the returned input the space is confined and needs openings, or use the known-air-infiltration method §304.6IFGC 2021