Desa Direct Vent shutting off

scooter4336 Posted By scooter4336, Dec 3, 2017 at 2:59 PM

  1. scooter4336

    scooter4336
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    Dec 3, 2017
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    Hello - newbie to the forum but looking for an answer. I have a Desa VC36N Series direct vent fireplace. The pilot will light and the burner will turn on but then after about 5 minutes I hear a click which is the valve shutting off. I can relight the pilot in a matter of minutes and light the burner and it shuts off again in 5 minutes. I have already replaced the entire pilot assembly which did not solve the problem. The vent is clear. Is my next step to replace the valve? It is part # 14389 which comes up in a search as VALVE KIT 820 NOVA MILLIVOLT GAS VALVE. This fireplace is about 12 years old and always worked fine until about a year ago when it started doing this. Thank you for any help!
     
  2. DAKSY

    DAKSY
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    Have you watched the flames while it's burning? What does it do? Does it "lift" of the burner?
    What are the milliVolts doing when you read the thermopile?
     
  3. scooter4336

    scooter4336
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    Dec 3, 2017
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    Thank you for the reply. I don't really notice the "lift" from the flames. I did however notice after burning about 5 minutes the pilot flame became "less full" and the thermopile wasn't fully engulfed. The milliVolts when I lit the burner was 187 and it slowly dropped and finally was at 129 when the valve shut off.
     
  4. DAKSY

    DAKSY
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    Sounds like the thermocouple is bad. Do you know how to test it?
     
  5. scooter4336

    scooter4336
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    Dec 3, 2017
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    I know to check it for continuity..........however, when I replaced the pilot assembly it included a new thermocouple and thermopile........this was just about a month ago. Also the pilot light will stay lit indefinitely until I light the burner.........then the valve shuts off.
     
  6. DAKSY

    DAKSY
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    Have you tried burning it for a short time with the glass off? Does it go out?
     
  7. scooter4336

    scooter4336
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    Dec 3, 2017
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    I have not tried that. I'll give a shot and see what happens.
     
  8. scooter4336

    scooter4336
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    Dec 3, 2017
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    I opened the glass door and it did not go out after 10 minutes. So I'm guessing this a sign of a blocked vent?
     
  9. DAKSY

    DAKSY
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    Maybe. Maybe not. The sections of DV pipe between the stove & the cap may have been improperly connected.
    If exhaust is allowed to leak into the combustion air, the unit will go out from lack of O2.
    I WOULD check for a blockage...Bird's nest or a Beehive.
     
  10. scooter4336

    scooter4336
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    Dec 3, 2017
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    Great........thanks for the help! The fireplace did work fine for about 9 years so I don't think it is a connection issue. I did see wasps flying out of the termination cap over the summer so could be a nest! Again thanks for the advice!
     
  11. scooter4336

    scooter4336
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    Dec 3, 2017
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    So I waited until the coldest and snowiest day to remove the termination cap and check for a blockage. Sure enough there were two smaller wasp nests.......don't know if they were large enough though to limit the intake air. I'll find out soon!

    [UPDATE] 10 minutes after writing this the fireplace shut off...........back to square one.
     
  12. DAKSY

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    Where were the nests?
    Intake or exhaust?
    Did you check BOTH sides?
     
  13. scooter4336

    scooter4336
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    Dec 3, 2017
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    They were on the intake. I only checked outside after taking off the termination cap and looked as far as I could down the vent......didn't see anything else. Didn't think of checking closer to the fireplace.......that will be my next step.
     
  14. Millbilly

    Millbilly
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    Dec 13, 2015
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    I am having the same problem with the 42" version. Pilot looks great with the glass off. Put the glass back on and the pilot slowly pulls off. Is yours vented vertically? I found the installation manual online and it looks like a restrictor is supposed to be installed in the exhaust on all vertical vent setups. The one I am trying to fix is about 20ish feet up with no restrictor installed.
     
  15. scooter4336

    scooter4336
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    Dec 3, 2017
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    Mine only rises about 3 feet on an angle and then about 3 feet horizontally outside. Strange thing though......while we were going through the recent cold spell (single digits and below zero) the fireplace was working perfectly.........for about 3 weeks since before Christmas! Two days ago it warmed up to the 40's-50's and it started shutting off again. Don't know if it's related or just a coincidence. Getting cold again starting tomorrow so I'll see if it starts working again.
     
  16. DAKSY

    DAKSY
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    If the pilot flame is SEVERELY agitated by the incoming intake air, that would be the reason for the restrictor. Does the unit BURN with the glass off? If so, when you put the glass on, do the burner flames lift & ghost? If they do, that's a venting issue.
     
  17. DAKSY

    DAKSY
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    Can you post a pic of your DV cap?
     
  18. Millbilly

    Millbilly
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    The Flame is not ghosting. The pilot does not appear to be agitated. It performs perfectly with the burner off. Per the manual I believe it is missing an exhaust restrictor, not intake. Once the burner is on the pilot slowly begins to reach high until it eventual shuts down the unit. My thinking is that the lack of the exhaust restrictor could be causing this. Have you installed any of these? It looks to me per the manual that the exhaust restrictor is to be installed on the top of the firebox, which is problematic if that is the case.
     
  19. DAKSY

    DAKSY
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    You SHOULD be able to access the location where the exhaust exits the firebox & fabricate something to act as a restrictor.
    BEFORE you get that deep into your unit, have you taken a milliVolt reading on the thermocouple?
     
  20. Millbilly

    Millbilly
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    Dec 13, 2015
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    Tc is 23mv. This is not a tc issue. I am watching the pilot pull up off the tc after the burner is running. I am specifically asking if anyone here has experience installing these desas and knows about the flue restrictor
     
  21. DAKSY

    DAKSY
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    TC should be >28mV
     
  22. Millbilly

    Millbilly
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    I don't believe that to be an accurate figure.
     
  23. DAKSY

    DAKSY
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    OK. Believe what you want. Your problem to solve. I will leave the conversation.
     
  24. Millbilly

    Millbilly
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    Dec 13, 2015
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    Yes thank you Daksy. I know it is my problem to fix as I am the one asking if there is anyone on here that has experience in installing these fireplaces and specifically the need for the exhaust restrictor with vertical vent configuration. I am not a fan of fabricating parts for anything. Thank you for your input but the minimum tc millivoltage is certainly lower than >28 on a sit 820 valve.
     

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