Why would a 50-gallon propane water heater just stop working?

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On 2016-08-03 6:51 AM, trader_4 wrote:

Read again, the thermal fuse is self-resetting, you cannot reset it. When the thermal fuse triggers all gas stops including the pilot light, when it cools down I simply lit the pilot again, the burner fires up, however the lack of airflow caused the chamber to heat to the point of once again triggering the thermal fuse. Once I cleaned the base of the tank all is good again.
The link below might explain better

https://www.youtube.com/watch?v=KHXRwLGJFhc

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On Wednesday, August 3, 2016 at 7:37:52 PM UTC-4, Idlehands wrote:

Well, that makes debugging it harder, that's for sure. I guess he could try setting the temp to the lowest possible and see what happens. If it;s this thermal safety, then you would think at the lower temp it probably wouldn't trip, unless the main thermostat is kaput and it is really overheating. But if that were happening, we'd probably have heard something about unusually hot water by now.

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On Thu, 4 Aug 2016 05:37:38 -0700 (PDT), trader_4 wrote:

I am still at a loss for debug.
Here is a picture taken just now:
http://i.cubeupload.com/CYmIjq.jpg
1. The flames are on top 2. The pilot candle is actually above the thermocouple 3. The thermocouple is below the pilot candle
I don't think the thermocouple is the problem only because when I'm watching, the pilot light stays lit, the burner stays lit, and everything works fine.
It's only over the period of a day that the pilot light goes out.
I do understand that the thermocouple could be intermittent bad and that they're cheap. But I generally try to debug bad parts by understanding them.
I tried to remove the old thermocouple from the older disconnected water heater but it broke when I removed it, so, I'm a little afraid of removing the thermocouple on the intermittent heater which is connected.
One test I need to run is to check the millivolts on the thermocouple, which I will try soon (but I don't want to break the thermocouple just testing it).
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Do you have any draft where heater is located ???
"Tatsuki Takahashi" wrote in message ---
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On Thu, 4 Aug 2016 22:22:03 -0700, Tony944 wrote:

The water heater is on a pedestal and is in a closet where there can't be a draft. I looked to see if it was dirty inside, but it looks pretty clean also.
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There must be some source of fresh air for combustion in the closet, which implies that a draft is not impossible.
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On 08/08/2016 10:56 AM, Scott Lurndal wrote:

It's also possible for the exit flue to have excessive draw and blow out a pilot, particularly if the wind blows strongly. This is quite dependent upon individual installations and the design/configuration of the specific water heater--some are much more susceptible than others.
I've a little space heater in the wellhouse to keep from freezing; have to check it if there's a "big blow" as it occurs for it on a moderately frequent basis. Of course, this is an area where wind is the norm...and we think 20-25 mph is just a gentle breeze... :)
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On Thursday, August 4, 2016 at 10:58:18 PM UTC-4, Tatsuki Takahashi wrote:

Hard to tell for sure, but the end of that TC looks like it may have crud on it, ie the glowing, uneven bright spots? Have you had the burner out to look at it?

I don't know what else may or not be involved in your unit, but in the WHs I've worked with, it could only be:
Thermocouple Gas Valve Something blowing the pilot out
TC is cheap.
Idlehands says his has a self-resetting thermal over temp cuttoff built into the gas valve. At least part of it is in the gas valve, not sure if there is more to it than that, probably not. Gas valve is more expensive and less likely. If yours has one, did you try turning the temp all the way down and see if it stays lit? Even if it doesn't have that safety, turning the gas valve off over night, but leaving the pilot lit might be an interesting test, to see if it still goes out.
Something blowing the pilot out every day doesn't sound likely.

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On 2016-08-04 8:57 PM, Tatsuki Takahashi wrote:

In thirty years of working in electronics I have never "debugged" a device. I have "debugged" software and used "troubleshooting" skills on devices. Okay now that is off my chest....
Did you try cleaning out the bottom of your tank? This simple task solved the exact same issue with my tank. My symptoms were not hot water, light pilot, tank would heat up, then cool down again. Vacuum the bottom of the tank, light pilot, stays lit.
I have had to do this twice this year
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On Friday, August 5, 2016 at 8:43:41 AM UTC-4, Idlehands wrote:

That sure sounds unusual. I have never heard of anyone having to vacuum the underside of a WH *twice a year* in order to keep it lit.
What kind of environment is this WH in?
Is this your couch? ;-)
http://www.ohiobasementsystems.com/core/images/mold/07lg-moldy-basement-furniture.jpg
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On Friday, August 5, 2016 at 9:27:05 AM UTC-4, DerbyDad03 wrote:

I agree. I have decades of experience with gas WHs too. I had one thermocouple go bad, never had to clean one. I recently helped a friend who has a power vent one though, where his would not ignite because some rust had dropped down on the igniter. That one was about 6 years old and needed some vacuuming to get it working again. I agree that it;s possible something is fouling the TC, that pic seems like there could be some rust on it, where it's glowing differently. And just to be clear, what we're all talking about is cleaning the burner area, not the bottom of the tank, at least I am. I couldn't even see the bottom of my tanks.
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On 2016-08-05 7:27 AM, DerbyDad03 wrote:

It's in the laundry room next to the furnace, laugh all you want but instead of chasing a phantom thermocouple issue this solves quickly and neatly.
Oh and no my couch does not match your home pictures.
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On Saturday, August 6, 2016 at 11:32:23 AM UTC-4, Idlehands wrote:

Nobody is laughing. We're asking a serious question.
It makes no sense *to us* that the underside of a WH should need to be vacuumed every 6 months in order to prevent the thermal fuse from opening. Again, it makes no sense *to us*. That is why I asked.
Your situation is highly unusual - based on our experience - and in the spirit of a.h.r. we would like to understand the situation.
How much debris do you actually end up cleaning out every 6 months?
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On Saturday, August 6, 2016 at 12:23:40 PM UTC-4, DerbyDad03 wrote:

better to use compressed air to clean stuff. vacuuming doesnt get out all the crud compressed air does.
many years ago i had my old furnace cleaned. after the tech vacuumned every thing out.
i had him blow out the remaining dust with my stationary compressor.
amazing how much dirt came out.
the tech was very concerned the dust would make me mad. i said its my house and dust
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On 2016-08-06 10:23 AM, DerbyDad03 wrote:

It's not a an "every six month" issue but it's cropped up twice now, I am not vacuuming up a lot of dust or material, at least you don't hear tons of material rattling through the shop vac.
The first time it happened that the pilot wouldn't stay lit I found out that you have to change the entire burner assembly, not just a thermal couple, welcome to progress. I searched for solutions and found about about the vacuum idea. It worked and lasted over a year. Just recently I woke up to no hot water again. Vacuumed it again and now it's running again.
This video describes the issue with the same model, although I did not replace the burner assembly.

https://www.youtube.com/watch?v=6M_NNby9cDk

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that doesn't sound right to me
the flame from the pilot should be heating the thermocouple. m
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On Thursday, August 4, 2016 at 10:58:18 PM UTC-4, Tatsuki Takahashi wrote:

i repair office equiptement for a living .... its best to just replace cheap parts that are possibly bad......
so you check the thermocouple with a meter.....
do you really want to sit there all day monitoring it all day.???. its output may drop over time. grand waste of time
just replace the thermocouple and move on to the next thing that needs attention
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