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Combustion Air

MR_Cosna
MR_Cosna Member Posts: 1
in THE MAIN WALL
I have a basement that my architect says needs 100sq inches of fresh air. My contractor wants to get the air through the 2 feet by 6inch window next to my furnace.  The architect wants to go through the joist.  

I am so confused. 

Comments

  • kcopp
    kcopp Member Posts: 4,462
    how many btu is the FHA furnace?
  • MR_Cosna
    MR_Cosna Member Posts: 1
    kcopp said:
    how many btu is the FHA furnace?
    Good question. I have no idea. Does that make a difference? 
  • kcopp
    kcopp Member Posts: 4,462
    Makes all the difference.
    A furnace, water heater that uses more BTU needs more air for combustion to happen safely.
    Are there other fuel burning appliances in the mechanical room?
  • MR_Cosna
    MR_Cosna Member Posts: 1
    kcopp said:
    Makes all the difference. A furnace, water heater that uses more BTU needs more air for combustion to happen safely. Are there other fuel burning appliances in the mechanical room?
    No just the furnace and hot water tank.  I just know that based on square footage and btu of the furnace I need 100 sq inches of combustion air 
  • kcopp
    kcopp Member Posts: 4,462
    Your mechanical room must be pretty small
    Simple fix would be to either add a couple ( 1 up and 1 down) openings to allow fresh air to come in or use a fan- in- a - can that draws in air when the furnace turns on.

  • MR_Cosna
    MR_Cosna Member Posts: 1
    kcopp said:
    Your mechanical room must be pretty small Simple fix would be to either add a couple ( 1 up and 1 down) openings to allow fresh air to come in or use a fan- in- a - can that draws in air when the furnace turns on.
    Don’t think I have enough space for that 
  • Jamie Hall
    Jamie Hall Member Posts: 24,491
    Whether you have the space is not a valid question. You have to have the space, or the appliances will not be safe to use. Your contractor's size window (144 square inches) is technically big enough, but will have to be open at all times when either appliance is running.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • HomerJSmith
    HomerJSmith Member Posts: 2,585
    edited April 2021
    First of all, you have a boiler not a furnace.

    There is a name plate on the inside of the boiler door on the right or left side where the fire tubes and gas valve are. The tag will state the input BTUs. Same with the name plate on the water heater.

    If you have a clothes dryer in the same place, that makes a difference, too.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,248
    The architect has already sized the opening, why ask about ratings?

    @MR_Cosna

    When he say 100 square inches of opening that means 100 sq inches of free area. So if a louver or screen is installed over the opening the area the louver or screen material takes up must be allowed for.

    If you need 100 free area you will need an opening 25%-50% larger depending on the louver.

    To keep from freezing pipes you need a dampers system or a "fan in a can" that will only bring in air when the boiler or water heater are actually firing. Doing this requires someone that is farmalier with this. And the damper or fan must be interlocked with those two appliances so they cannot run without combustion air
  • kcopp
    kcopp Member Posts: 4,462
    https://www.fieldcontrols.com/fan-in-a-can-cas-4-combustion-air-system/#:~:text=The Fan-in-a-Can, Jr., model CAS-4Jr. is designed for,with the addition of control kit CK-20 FV/FG.
    Zman

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