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Thread: Fresh air for furnace

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  1. #1

    Default Fresh air for furnace

    I know this isn't strictly speaking a plumbing question, but thought you might be able to help anyway... My friends just bought a new loft style apartment in NYC where each apartment has its own gas fired boiler to supply hot water for the radiators. Unfortunately, their boiler (furnace?) is in a closet off of their bedroom, approximately 3 feet from their bed. It seems to be one of the newer kind with horizontal flue venting out a side wall. It also has a 4" fresh air supply duct that draws air from outside for combustion. This furnace, the hot water tank and an expansion tank are all housed in a 4' by 3' closet.

    Ok, so here's the question: currently the door to this closet has a louvered grate on it. They would like to replace with a solid door to help reduce the noise (since its so close to their bed). Is this a problem? Since there is a fresh air supply coming from outside, seems like the louver in the door might not be necessary? Who could they ask for info? Manufacturer of heater? Or is this generally just a bad idea?

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    Double check the installation manual - if they didn't leave it, you may be able to find it on the web. If the thing has outside air and is vented to the outside, I don't think it needs the louvered door. Is the hot water tank an indirect one (i.e., it gets heated by the boiler)? If there is no other combustion device in there, it should be okay. Note I'm not a pro. For a device that draws air from the dwelling, you need about 1 sq in per 1000btu from what I read both at the bottom of the door, and at the top.
    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
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    Combustion air is not an amateur topic, because there can be serious including fatal consequences. In general, a gas fired appliance is not usually allowed adjacent to a bedroom unless it is direct vented. Hence the louvered door seems strange. However, I would not change anything without consulting a local HVAC professional and the manufacturer of the unit.

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default venting

    The only purpose for the louvered door might be in the event of a gas leak, it could escape rather than accumulate to a dangerous concentration. In addition, you would probably smell it faster than if it were in a sealed or closed off room. If you can get vents to the outside air to replace the louvers, then you might be able to replace the door.

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