Failing Gas Fire Thermocouple

Discussion in 'Plumbers' Talk' started by Mosaix, Mar 12, 2018.

  1. Mosaix

    Mosaix Member

    Hi Guys

    I've got a gas fire that fails to light four out of five times. Pilot lights up, I wait the recommended time (5 to 10 seconds) release the control and out goes the pilot. Makes no difference how long I wait - it usually fails.

    Both gas fitting companies in my small Shropshire town aren't interested in attending.

    Any ideas?

    Thanks in anticipation.
  2. The Teach

    The Teach Well-Known Member

    Which gas fire is it ?
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  3. Mosaix

    Mosaix Member

    It's a Flavel Caress HE.
  4. The Teach

    The Teach Well-Known Member

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  5. Mosaix

    Mosaix Member

    Thanks Teach.

    I've checked and the pilot looks fine and healthy. I vacuumed around it just to make sure. Thanks for the link - will see what I can find.

    Edit: Wow, never realised there were so many in my area. Thanks again.
  6. seneca

    seneca Screwfix Select

    It sounds like the thermocouple has failed.
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  7. The Teach

    The Teach Well-Known Member

    Use the 'choose appliance and find fire in the list,you probably already have.

    Instead of phoning you can usually email the gas technicians your needs ;)
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  8. chippie244

    chippie244 Well-Known Member

    I changed the thermocouple on my old gas cooker a couple of times and it was a simple swap out, are gas fires different?
  9. The Teach

    The Teach Well-Known Member

    The newer fires use an oxygen depletion sensing pilot assembly and the thermocouple is not a separate part any more :(

    typical oxy sensing thermocouple assembly. Around £30 :mad:
    the pilot filter can block up easily :(
    pilot assy.jpg
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  10. Mosaix

    Mosaix Member

    That looks exactly like the one on my fire, Teach. But, I tell you what, the thermocouple sensor on mine looks like only the tip is in the pilot flame. In that picture much more of it will be receiving heat. Could that be the problem and is it adjustable?
  11. kiaora

    kiaora Well-Known Member

    This type of pilot assembly, has a calibrated hole to allow the tip of the flame cone to envelop the t.couple tip.
    It works on a very clever idea.
    As we all know the air we breath is 20.9 % oxygen, the gas needs 2 volumes of oxygen to 1 volume of gas.

    If for any reason the oxygen level is less than 20.9% the shape of the flame cone, changes, and not enough heat reaches the tip, and it locks out!

    So it’s actually a very good piece of engineering and one must not ‘adjust’ one.
    So as has been mentioned by the teach, debris, fluff etc can cause problems.

    But let’s not forget! You may have low O2 levels in the room, !

    Lesson over

    Hope that helps

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  12. Mosaix

    Mosaix Member

    Hi Peter

    Thanks for the advice. Will try and light it with doors windows open etc.

    The assembly looks very clean, dust free no fluff etc. The flame itself burns steadily and is not mis-shapen or flickering.

    Just going back to Teach's picture. In the picture the entire length of the thin end of the thermocouple would appear to be enveloped by the pilot flame. On mine only the very tip will is in the flame. I'm coming round to thinking it's either failed or a or was faulty in the first place. Either way a new one would seem to be the solution.
  13. kiaora

    kiaora Well-Known Member

    Just be careful, the thermocouple is in fact a safety device, it may well be faulty, but don’t just assume,

    You know what they say about assume? As in it makes an *** of u and me!

    Good luck
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  14. Dave does Gas

    Dave does Gas Well-Known Member

    Have you had the fire serviced at all since its instalation. I often find that lack of servicing can be the issue, May just take a gas safe with a proper knowledge of the appliance to fix rather than a scoot round with a hoover. This will also ascertain if your flue is performing to the correct standard and the ASD is doing its job correctly. One other tip it would pay you to buy and fit a carbon monoxide alarm as you have an open flued appliance.
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