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Help with (relatively) new natural gas log set, unvented, mains will not light

Post in 'It's a Gas!' started by lewist57, Oct 20, 2008.

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  1. lewist57

    lewist57 New Member

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    Purchased and installed a nice set of unvented natural gas logs last year. Fired right up, worked just fine all last winter. Cut off pilot last spring. Tried to fire it up this past weekend, pilot lights and stays lit, but main burners will not come on. Took it out of fireplace twice, cleaned all thermocouple surfaces, sprayed compressed air into main burner tubes, checked wiring for loose connections, but main burners will not come on. Manufacturer help line difficult/impossible to get through to, and manual with gas logs not much help. I can't believe that it is anything all that complicated, but if anyone can suggest other items to check, it would be appreciated.

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  2. R&D Guy

    R&D Guy New Member

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    Sounds like the thermopile is out. That's the larger of the 2 probes your pilot heats up. You could always try taping your valve with the handle of the screw driver. Sometimes a valve sticks when it hasn't been used in a long time, but I'm willing to bet your thermopile is the problem. This is a common problem in the fall.

    Here is a pretty good guide to how your pilot works and troubleshooting your issue:

    http://www.hearth.com/econtent/index.php/articles/how_gas_works
  3. lewist57

    lewist57 New Member

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    Thermopile out after just one heating season? And the gas logs were used on average 1 - 2 hours per week, and are not the main source of heat for the hosue. Perhaps, but I think I'll get the volt meter out and try to check it, after tapping on the gas valve, and cleaning out the ODS pilot assembly.
  4. R&D Guy

    R&D Guy New Member

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    Well at say 2 hours a week for 24 weeks (6 months), I'd say after 48 hours of operation nothing should be wrong with your unit, but that answer doesn't help you. Does your pilot stay on all season, or are you lighting it each time you light the appliance? As I said you could always try taping on the valve, but if it's sticking the problem will slowly get worse until you replace the valve. I agree, its quick for anything to break down in one season, but that is still what it sounds like from your description.
  5. lewist57

    lewist57 New Member

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    The pilot was on continuously from late last fall until mid spring. I did tap on the valve this week, and no change. I am going to put the unit on my workbench this weekend and test the output of the thermopile, and then try to put voltage to the gas valve to see if it will move. In the event that either the thermopile or gas valve is bad, is there an recommended aftermarket supplier of replacement parts? From what I have found so far, it would appear to be cheaper to buy a new set than the replacement valve assembly.

    FYI, I am a professional mechanical engineer, so I believe I can fix the logs safely, or at least know when it is time to throw in the towel and buy a new set. By the way, cool CFD graphic R&D;Guy.
  6. lewist57

    lewist57 New Member

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    just out of warranty, no recall according to manufacturer.
  7. webbie

    webbie Seasoned Moderator Staff Member

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    Yeah, does sound like a defective valve....and, in general, vent frees are not designed to work on (either you or the factory), but it seems like you will know when to stop.

    In such a case - I would think that the manufacturer or dealer might be able to help in some way - perhaps a new valve or a heavy discount on a replacement set - no way that it should have failed this early.....it is also remotely possible that the valve has a separate and longer warranty than the set.

    Some cajoling to the maker might be in order - after all, they don't want you placing bad reviews and experiences on the net and elsewhere. As a former manufacturer myself, I would certainly want a unit which I sold to last more that a few weeks out of warranty!
  8. R&D Guy

    R&D Guy New Member

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    Well sorry man. Glad to see another M.E. on here though. Get your hands on a multi meter and check the milli-volts from the thermopile, and do a continuity check on the on/off switch with the leads attached if your unit has one.

    I'm sure you know this, but if you do end up changing out the pilot assembly be very careful to find the exact same model and part number or an alternative spec'd by the mfg. I'm not up on vent-free fireplaces, but from the ones I've seen the pilot is designed to turn the unit off when the O2 gets too low, and the CO gets too high (for people) in the room. Common pilots spec'd for vented gas appliances could put your family in great danger.

    Glad you like my avatar, I'm guessing you play with CFD software too. Amazing software huh? I send some of the cooler looking graphics to marketing and I keep telling them we need to show off the fact that like Boeing we also "Fly the plane before we build it," but nothing yet. Guess its just something an engineer finds cool.
  9. lewist57

    lewist57 New Member

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    Well, while at home today, found the thermopile was putting out volts, and the gas valve was clicking on the bench, but it just won't fire up installed. I can hear the gas valve click closed after killing the gas. The implication is that either the valve is not allowing gas to flow (ie - clicking does not equal valve open), or there is a blockage in the gas lines for the set. House gas pressure is fine, all other gas applicances working well. Pilot works great, therompile is making volts, valve is clicking, but no main flames. Perhaps its time to visit Lowes or Home Depot. Sigh.

    Yup, I have played with CFD sofware before, my expertise is more on piping network simulation programs, but did recognize the graphics. I think the public would find it cool if you could make a video of it, such that the average buyer would look at it and say "wow, computer generated flames!".


    Thanks for everyone's input, but it would seem quicker just to purchase a new set (and keep better track of the darned warranty paperwork).
  10. lewist57

    lewist57 New Member

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    END OF STORY: $199 at Lowes got me a new vent free set that works fine, thanks again.
  11. R&D Guy

    R&D Guy New Member

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    Well good for you. At least now you don't have to come home from a long day at work and start fussing with your old fireplace.
  12. lewist57

    lewist57 New Member

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    Yup, and even if I fixed it, how long would it last before it needed attention again? The new set has a 3 year warranty, so I guess this was the path of least resistance.
  13. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    My bet is that damn spider nest behind the burner orifice. If you're hearing the valve magnets clicking, the valve is working properly, but the spider has blocked the gas flow with her little nest...Seen it before & we'll see it again...
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