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  1. #1
    Join Date
    Mar 2019
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    How long for thermopile to close main gas valve on propane fireplace

    I have several direct vent propane fireplaces in the building that I manage. One of them recently exploded (shattered glass and destroyed direct vent). as someone was lighting it. It sounds like the pilot flame blew out but the main gas valve stayed open for some time after the pilot blew out. During this time the owner tried to relight it and the fireplace exploded. By good fortune, no one was injured.

    I ran the following test on the other fireplaces. With the fireplace running, I shut the manual gas valve. Both the main flame and the pilot flame went out immediately. The pilot valve closed one second later but the main gas valve stayed open for 51 to 77 seconds before it closed. These gas fireplaces were manufactured by Osburn and are about 20 years old. The thermopile in all of the fireplaces I tested was clean and positioned in the pilot flame. Otherwise, the fireplaces work fine.

    51 to 77 seconds for the main gas valve to stay open after loss of pilot flame seams far too long, and is dangerous in my opinion. Gas fireplaces in Canada must comply with ANSI Z21.88/CSA 2.33. I have to think there is a clause in this regulation that specifies how soon the main gas valve must close after loss of pilot flame. But I am unable to download a copy of this regulation.

    Can someone please comment on what the regulation is for closing gas valve on loss of pilot flame? If someone has a copy of ANSI Z21.88 that you can share that would be much appreciated.

  2. #2
    Join Date
    Aug 2004
    Location
    S.E. Pa
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    It's about $1K for a copy of Z21.88. Since it came out in 1995, glass enclosed fireboxes must dropout within 30 seconds of pilot flame extinguishment. You'll see them referred to as "quick dropout" because ordinary gas logs can take up to 180 seconds.
    There should be a fire investigation into the incident and that will determine the cause. I've investigated hundreds of incidents involving fireplaces and there are so many factors to consider.

  3. #3
    Join Date
    Mar 2019
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    Thread Starter
    Thanks for the response @hearthman. I'm surprised the code allows for up to 30 seconds. 30 seconds is still a lot of fuel for a small firebox. in my mind, there is still a chance of explosion if fuel is allowed to accumulate for 30 seconds.

  4. #4
    Join Date
    Sep 2015
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    Ontari-ari-ari-o
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    No reason to be playing detective as a building manager you should be calling in a pro to take a look at it. When were these fireplaces last cleaned and inspected?

  5. #5
    Join Date
    Mar 2019
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    Thread Starter
    Quote Originally Posted by Sooty View Post
    No reason to be playing detective as a building manager you should be calling in a pro to take a look at it. When were these fireplaces last cleaned and inspected?
    We did call in a pro. He couldn't explain what happened. I'm already much further ahead than he is...

    Fireplaces are inspected yearly. The lighting instructions in owner's manual say to wait 5 minutes with the control knob in "OFF" before attempting to light the fireplace. I suspect this was not done.

  6. #6
    Join Date
    Aug 2004
    Location
    S.E. Pa
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    Check the manual again. Some brands have put instructions to remove the glass before attempting to ignite the pilot with LP gas.

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