Safe temps for 0" clearance?

pcampbell Posted By pcampbell, Jan 22, 2009 at 1:31 AM

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  1. pcampbell

    Member 2.

    Jan 3, 2008
    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.
  2. R&D Guy

    R&D Guy
    New Member 2.

    Apr 25, 2007
    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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