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Safe temps for 0" clearance?

Post in 'It's a Gas!' started by pcampbell, Jan 22, 2009.

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  1. pcampbell

    pcampbell Member

    Joined:
    Jan 3, 2008
    Messages:
    102
    Loc:
    Vermont
    I have a DV wall furnace that is listed as 0" clearance to combustibles. I measured the pipe temps today with my infrared gun and found the hottest temps to be around 240F. I am just wondering what is considered the maximum safe range for clearance to framing wood, drywall, etc.

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  2. R&D Guy

    R&D Guy New Member

    Joined:
    Apr 25, 2007
    Messages:
    375
    Zero clearance is likely just for the unit, not the pipe. Pipe almost always has clearance required. The install manual should specify this. If its 240° F and touches wood/combustibles then I'm sure its too hot. If it's 240° and there is an air gap then you need to measure the surface temp of the surrounding combustibles.

    ANSI Z21.88a-2007 is the standard fireplaces are certified to today, your furnace is likely a variation of that standard, but Z21.88 says any combustible surface not exposed to the room (not seen e.g. inside the wall) has a maximum temperature limit of 90° F above ambient temperature. So if your house is 70° inside, the combustible cannot exceed 160°. That temperature measurement is taken when the system is at equilibrium (hottest).

    If you are concerned then I don't think there is any reason you can't add extra clearance. I've been guilty of that before.
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