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  1. #1
    Join Date
    Dec 2019
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    Vent-less gas log set with doors closed.

    I want to install vent-less gas logs in my see-thru masonry fireplace.

    I am wondering if I can run the logs with the doors closed. I know the manual states to always have door open. In the past before I knew much about gas fireplaces I moved into a home with vent-less gas insert that we ran with doors closed quite often. The flame would go out after a while and come back on but I assumed it was just oxygen was low in the closed insert.

    We want to run with doors closed because of kids among other reasons.

    The doors will be on masonry, are not air tight doors and there will be lots of gaps between fireplace faces and masonry in mortar joints and due to not perfectly flat or smooth masonry. So there will be some ventilation but it may get hot. In my insert I think the controls were further away and better insulated than what the gas log set will be.

    Will the heat damage the controls? Is there a real danger from running with doors closed?

    I know it is advised against but is there anyone who runs their ventless logs like this and is it really something to worry about?

    My equipment:

  2. #2
    Join Date
    Jul 2010
    US of A
    Post Likes
    Your bio says you are an HVACR engineer and you ask these questions?

    They are bad enough if you follow the instructions let alone not follow the instructions.

    Don't install it and if you do follow the instructions. I am sure the instructions say to read all of it too.
    Signature removed Violated rule #15

  3. #3
    Join Date
    Aug 2002
    Southold, NY
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    WHY would anyone install Vent less?

  4. #4
    Join Date
    Aug 2002
    Cincinnati, Ohio
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    Combustion produces CO2. CO2 displaces O2. If the doors are closed the CO2 will not freely escape and the O2 will drop causing Carbon monoxide to be produced. The Oxygen depletion switch will not shut it off before the CO levels become deadly.
    captain CO

  5. #5
    Join Date
    Aug 2004
    S.E. Pa
    Post Likes
    The gas valve is rated 225F. Burning in a mason's jar will probably overheat it.

    Combustion needs oxygen. Burning in a mason's jar will probably use up the oxygen faster than it can entrain through the gaps as you noted before.

    Complete combustion results in CO2 as Jim noted. Where is this going to go? Do you have an ash dump that could 'drain' it away? Otherwise, it will displace the O2 and snuff out.

    The glass is typically tempered which is rated for 500F. You run the risk of shattering the glass. When tempered glass fails, it explodes into 40,000 Chicklets of glass shrapnel. Do you want your kids shredded?

    Kids should never be left unsupervised around fireplaces, cars, ovens, or anything else that could hurt or kill them.

    Masonry fireplaces were designed for vented operation. When you close the damper the mass of masonry absorbs tons of energy, The clearances to combustibles go out the window. Now, close the glass doors and you have a crucible.

    The incomplete combustion will probably result in tons of soot production, which will trash your home.

    Get some freestanding screens and rig them to act as crash guards to keep your kids away then open the doors.

    Get a low level unlisted CO monitor to protect your family.

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