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Old 12-11-2009, 10:39 AM   #1
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Gas log unit stuts off


I have a Martin gas log unit (10 years old). I've owned the house for 7 years, but hardly ever used it. It has seemed to have the same problems all along, but I just figure it's time time to fix it...mainly because my new bride thinks it's romantic.

First off, I have cleaned it out, and it's free of dust.

The pilot lights fine and stays lit on it's own if you never light up the unit. It's nice and steady, a little over an inch long.

The unit lights up good, and burns nice and even. The problem is just that it suddenly shuts off after a while. The pilot will stay lit if it's been on low, but it's been on high for a while, it goes out too.

The knob is low-high, and I would think that would control the size of the flame, not the length of burn time. It controls the length of burn. On high, it burns for 5-7 minutes before it all shuts off.

Is it a bad thermocouple? There aren't many parts, so there can't be many suspects. Ideas?

Thanks.

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Old 12-11-2009, 12:21 PM   #2
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Gas log unit stuts off


What little knowledge I have of gas fired "anythings" is with industrial ovens, but-it does sound as if you're thermocouple is not working properly, if at all. I do know that the thermocouple has to get to a certain temp on each application in order to make the capillary unit keep the gas valve open for the appliance to work. IF this thermocouple does not work properly, it should not effect the pilot light. Is this one of the type gas valves you have to hold "IN" for a few seconds as the gas logs start up? Then, a few seconds after releasing the gas valve the flames go out? IF so, this would indicate a thermocouple problem to me. Good Luck, David

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Old 12-11-2009, 01:02 PM   #3
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Gas log unit stuts off


After the pilot lights, you have to hold the knob in about 30 seconds for it to stay on. After that, you just turn the knob, and it fires right up.

Is the tremocouple the only part that could shut off the gas so abruptly? After it shuts off on it's own, there is no smell of gas at all. When I shut it off manually, it goes out slowly, and there's a hint of gas smell.
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Old 12-11-2009, 01:07 PM   #4
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Gas log unit stuts off


Based on your description I would bet on an insufficient gas supply. It sounds as if opening the flow of gas to the main burner drains all the gas out of the supply line, which results in the flame extinguishing.

Somewhere upstream of the fireplace is a gas cock that is either only partially opened, or shut and leaking by.

Just an idea........
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Old 03-07-2010, 10:49 PM   #5
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Gas log unit stuts off


What is the model number? If you haven't gotten it fixed yet.
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Old 03-09-2010, 01:06 PM   #6
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Gas log unit stuts off


well in my years of working on logs, this is happening for one of 3 major reasons:

1. bad thermocouple - low voltage, or intermittent voltage drop
2. up draft causes pilot flame to not hit thermocouple
3. lack of draft (closed glass doors = don't ever do) causes the oxygen starved flame to burn erratically and miss thermocouple.
4. Dirty pilot - dusty, debris, spider/webs interfeering with gas flow. The pilot flame should be blue with only a yellow tip. An all yellow flame is weak, and usually the culprit of a dirty pilot.

Based on how and what you described, I bet it's number 2. you turn on logs --> causing normal log flame appearance. --->now watch the pilot flame if possible, it may lift and pull away from the tip of the thermocouple. after 1-3 minutes this can turn the logs off (gas valve is shut off as a safety due to insufficient heating of thermocouple).

to fix: In the past I have positioned bent pieces of metal just under/around pilot to lessen the drafting effect. Or even some conveniently placed rockwool can help keep the pilot flame strait and true. This is a trial and error type thing, may and probably will take several tries.



It could also be to insufficient gas pressure or less then the required pressure to operate correctly both the log burner and the pilot assembly. This is certainly a possibility. In my experience, the least likely scenario, yet still possible.

Just to be clear, this is all based on assuming this is a "Vented" log set, as opposed to a "vent-free" type of log. This is important and you should know which type you are dealing with. "Vented" require an open flue, where "vent-free" do not require an open flue.

report you findings.
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Old 03-09-2010, 04:38 PM   #7
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Gas log unit stuts off


I have that same unit and had the exact same problem. Finally I fixed it by cleaning the inside of the pilot orfice with a small brush and cleaning the pilot flame sensor (little rod that sit in the pilot flame) with some fine steel wool.
After cleaning it out, vacuum the pilot area real good. My gas flames would stay light almost exactly six minutes before everything shut down. Now it works perfectly.
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Old 03-16-2010, 09:12 AM   #8
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Gas log unit stuts off


The thermocouple is part of what's called the pilot safety shutoff system. It senses if you have a safe pilot. If it is a vent free, there is also an oxygen depletion sensor as well that detects the amount of available oxygen. These sensors and others as well will shut off the unit if it detects an unsafe condition. It may just need cleaning, or there may be an unsafe condition. Call a pro, your family's safety is worth it isn't it?

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