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Thread: Oxygen to Sealed Combustion Hot Water Tank

  1. #1
    DIY Senior Member molo's Avatar
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    Sep 2006
    cold new york

    Default Oxygen to Sealed Combustion Hot Water Tank

    I'm have to replace an old water tank. It is in a small utility closet along side a furnace. Are there measures that need to be taken to ensure adequate combustion?

    Last edited by molo; 10-11-2007 at 01:11 PM.
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  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
    New England


    Absolutely. You mentioned closed combustion, though, and that provides both combustion air and exhaust through the piping. If the intake is inside of the room, then again, absolutely. The installation instructions will list the vent size required - this is normally X-sq inches per 1KBTU, and requires actually two openings, one near the top of the wall/door and a second one near the bottom.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    If by sealed combustion you mean an modern FVIR wh, with conventional draft hood on top, then the supply of combustion air is even more important than with an older unit. Although the actual requirements have not changed, you might have got by with less than optimum on an old one, and it will be trouble on a new one.

    The installation manual, and the National Fuel Gas Code spell it out. Depending on where the closet is, you will need a certain number of suqare inches of ventilation. You need TWO of these inlets, one in the top 14 inches from the ceiling, and one within 14 inches or so from the floor.


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