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Thread: Combustion Air

  1. #1
    Join Date
    Dec 2010
    Location
    Illinois
    Posts
    64

    Default Combustion Air

    Had one today that had a 2004 Amana 92000 btu high eff. furnace. It was in a 3 foot deep by 4 foot wide closet off of the utility room. Had solid doors and was just vented to that closet only. Is there a certain size closet that this would be ok in or is it always wrong with solid doors? Thanks!

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    E.D.S
    Home Inspections
    Lic.#450.010534

  2. #2
    Join Date
    Jan 2011
    Location
    Guelph,Ontario
    Posts
    169

    Default Re: Combustion Air

    Was there combustion air brought in from outdoors,and what did the rating tag say?


  3. #3
    Join Date
    Dec 2010
    Location
    Illinois
    Posts
    64

    Default Re: Combustion Air

    No air of any kind brought to the closet or furnace.

    E.D.S
    Home Inspections
    Lic.#450.010534

  4. #4
    Join Date
    Mar 2007
    Location
    Chicago, IL
    Posts
    2,797

    Default Re: Combustion Air

    Assuming no other source of combustion air, 92,000 BTU requires 4,600 cu/ft of confined space.

    For an 8' ceiling that's 575sq/ft floor space, or 25x23'

    If there were louvered doors opening to a similarly sized confined space they would need to supply 92sq/in of net free opening, which would translate (for typical restriction factors) to 123 sq/in of metal louvers or 368sq/in of wood louvers.

    For a 12' wide wood louver, that would be around 30" in height.

    For comparison, a 4x4x8' closet supplies 128 cu/ft, which will support a 5,560BTU appliance.

    Also, keep in mind that you have to count all the gas appliances in the space, for example a gas clothes dryers (each needs around 200 cu/ft for combustion in addition to make-up air) and water heaters.

    I have a spread-sheet I set up to calculate these requierments, if you let me know the BTU's of all appliances, I can give you the total requirements.

    Last edited by Michael Thomas; 03-05-2012 at 08:05 PM.
    Michael Thomas
    Paragon Property Services Inc., Chicago IL
    http://paragoninspects.com

  5. #5
    Join Date
    Dec 2010
    Location
    Illinois
    Posts
    64

    Default Re: Combustion Air

    Thanks a lot.

    E.D.S
    Home Inspections
    Lic.#450.010534

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