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Combustion calculation?

volute1 Member Posts: 2
I need help finding the calculations for combustion air to properly size a louver. We have one 399,000 btu gas water heater and one gas boiler at 1137 mbh. The boiler room is completely enclosed except for a door to the building hallway and one to outside with 4 or 5 1 inch holes drilled through it.


  • captainco
    captainco Member Posts: 768
    The door to the hallway will take air from the room.
    Based on somewhat guess work codes, you need 1 sq.in. of opening directly to the outside per 4000 btu. If ducted it is 1 sq.in. per 2000 btu. Unfortunately these openings can be as detrimental as they can be helpful.
  • Tim McElwain
    Tim McElwain Member Posts: 4,597
    Are you a professional trained to work on commercial equipment? If so you may want to look at a mechanical means of providing air. What size is the room in which this equipment is located?
  • volute1
    volute1 Member Posts: 2
    It looks like it will be a 32.4” x32.4” louver to supply enough fresh air for both water heater and boiler for the proper amount of combustion air. Thanks
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,386
    32.4" X 32.4" louver doesn't have 32.4" x32.4" of free space.
    EBEBRATT-Ed Member Posts: 14,560
    Louvers are around .75 free opening I beleive