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  1. #1
    Join Date
    Nov 2011
    Location
    Sedona, Arizona
    Posts
    20

    Default Forced draft water & only one combustion vent?

    I inspected a home that had an induced draft water heater, installed in a closet next to the garage, with a single combustion air vent in the wall opening into the garage, about two and 1/2 feet up off the floor. I called it as inadequate/improper combustion air supply in the report and the builder has stated to the buyers agent that this is ok?
    I know that two vents are required to avoid air stratification and that in the event of carbon monoxide production, the forced fan draft would vent it to the outside (no danger of gas spillage from the vent like an atmospheric unit). I still don't like combustion air being taken from the garage (which has no combustion air vents to the exterior). Any thoughts?
    Thanks
    JP

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  2. #2
    Join Date
    Mar 2007
    Location
    Plano, Texas
    Posts
    4,170

    Default Re: Forced draft water & only one combustion vent?

    No problem with combustion air being taken from the garage as long as the heater is 18" off the floor and the vent does not violate the separation wall between the garage and house. But yes the vents should be no more than 12" from the floor and 12" from the ceiling unless the alternate one opening method is used.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  3. #3
    Join Date
    Nov 2011
    Location
    Sedona, Arizona
    Posts
    20

    Default Re: Forced draft water & only one combustion vent?

    Jim
    well the vent opening is a breach in the firewall since it opens from the garage to the water heater closet, which is inside the home on the other side of the fire door to the garage. What is the alternate one vent opening method?
    JP


  4. #4
    Join Date
    Nov 2011
    Location
    Sedona, Arizona
    Posts
    20

    Default Re: Forced draft water & only one combustion vent?

    Never mind on the one opening method-just looked it up in "code check" and had forgotten about it -It has to be within 12 inches of the enclosure ceiling-not down below like this one was.
    JP


  5. #5
    Join Date
    Mar 2007
    Location
    Plano, Texas
    Posts
    4,170

    Default Re: Forced draft water & only one combustion vent?

    If there is continuous gypsum on the interior of the w/h closet walls and ceiling then the vent may not violate the separation.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  6. #6
    Join Date
    Jul 2008
    Location
    Utah
    Posts
    389

    Default Re: Forced draft water & only one combustion vent?

    Quote Originally Posted by JP Lomeo View Post
    It has to be within 12 inches of the enclosure ceiling-not down below like this one was.
    JP

    And . . . sized at 1 square inch per 3,000 BTU's.

    If you are using a power vent you can size the combustion air intake according to the recommendation of the vent manufacturer. Assuming it is a UL listed appliance. Often times much less that the 1/3,000 rule.


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