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Old 12-26-2004, 11:04 PM   #1
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A strange H2O heater question for ya

<This may be a duplicate post, since I've had a few failed attempts to post this. I apologize if it is.>

Went to my '75 Sovereign today to putter around and found I had no hot water. The water heater's pilot has been on for the last few months since I'm out there so much, and there has always been hot water.

Here are the facts:

* There is plenty of gas in both cylinders, all other gas operated appliances work great.
* The pilot will light and stay lit for as long as I want it to without shutting off.
* The furnace will light off as soon as I turn the valve to 'on'. The flame looks and sounds good as long as the door is open and everything is open to the elements.
* Within a minute or less of closing the door, I can hear the flame start to flutter for a few seconds, then the flame and pilot go out.
* If I open the door when the fluttering starts, the flame goes back to normal and stays that way as long as the door is left open.
* If I adjust the airflow on the inlet tube, by sliding the sleeve wide open, it makes the same fluttering noise as it does when the door is closed.
* The heater has made that same fluttering noise when it's heating the water, since I first lit it a few months ago, but I didn't know what it was until now. The heater has lit off whenever it needed to for the last few months without a problem.

So, it sounds like there is too much air coming in somewhere, but why would it do it with the door closed, when airflow is restricted, and not when the door is wide open? Any suggestions or ideas would be appreciated. The heater was replaced before I bought the trailer, probably within the last two years. I have the gas and the pilot shut off to the heater until I figure this out.

Thanks!
John
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Old 12-27-2004, 03:28 AM   #2
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Quote:
Originally Posted by krowsea
* The furnace will light off as soon as I turn the valve to 'on'. The flame...
You mean water heater, right?
Take a good look at your thermocouple wiring/connection. I wonder if, when the door is shut, the TC's connection to the control unit is being disturbed making the control unit think the pilot has gone out.

Without actually seeing your setup, I'm having a hard time envisioning a way you could be starving the unit for air. But if the TC's connection is bad, it will effectively starve the flame of gas.

Tom
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Old 12-27-2004, 06:58 AM   #3
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Critters

Check the flue or your exhaust. It is filled with Mud dobbers nest or some other debris.

Also, check the venturi sleeve. It may have been repositioned and it is near close.

Sounds like air is good during opened door but restricted when closed.

Smily
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Old 12-27-2004, 08:41 AM   #4
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Quote:
Originally Posted by TomW
You mean water heater, right?
Tom
Uhhh, yeah, actually, that's what I meant. Thanks Tom


Quote:
Originally Posted by smily
Check the flue or your exhaust. It is filled with Mud dobbers nest or some other debris.
I'll check that. I did put an angled cover over the exhaust vent to keep rain out, but the vent is still open. Could that be it?

Quote:
Originally Posted by smily
Also, check the venturi sleeve. It may have been repositioned and it is near close.
The sleeve doesn't close all the way. With the sleeve closed as much as it can, leaving approximately 1/8 in holes all the way around (and the door open), it runs pretty well. If I open the sleeve up, it flutters like it does with the door open. Thanks Smily

John
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Old 12-27-2004, 08:46 AM   #5
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john

check for a spider nest in the venturi, a soft bristled brush works well.

i have to clean mine out semi annualy.

john
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Old 12-27-2004, 10:13 AM   #6
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I had a problem on mine somewhat similar. It occured to me that there might be a bit of debris in the gas orifice, so I started to screw it out. It nearly fell out in my hand! I have no idea how it came to be so loose, but that is where it was sucking air and why I could not get any decent air/fuel mix with the shutter.

That said, your symptoms do sound more like a restricted flue; at least to this non-expert.

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Old 12-27-2004, 10:31 AM   #7
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It could be....

Quote:
Originally Posted by krowsea
....Within a minute or less of closing the door, I can hear the flame start to flutter for a few seconds, then the flame and pilot go out.

...that the door closing is diverting the flame just enough to cause an "undertemp" (on the "pilot *on*" expansion bulb/Thermo-couple) or an "overtemp" on the high temp sensor....(see TomW's post above).


On some of the gas burners I have worked on the main burner flame will actually "lift" the pilot flame just enough to permit the "pilot light off" sensor (bulb) to loose enough temp to shut everything down...I do not remember a situation where the main flame was diverted enough to the "high temp sensor" to shut the flame down, but, depending on design, I supose it could happen.

I think the first thing I would do is get a good manometer and measure the gas pressure before and after the Water Heater gas regulator.

Luck.
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Old 12-27-2004, 11:58 AM   #8
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Quote:
Originally Posted by john hd
john

check for a spider nest in the venturi, a soft bristled brush works well.

i have to clean mine out semi annualy.

john
Thanks everyone for your sugestions. I'll try them out and post the results. John, quick question. The venturi in question, is that the long tube the flame shoots down? I didn't see anyplace it narrowed down, but I couldn't get a direct look into it.

John
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Old 12-27-2004, 01:05 PM   #9
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it should be a detachable L shaped tube that goes from the gas valve into the burner area. spiders seem to make a home in the furthest reaches of it. removing it is the only way to make certain it is not obstructed.

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Old 12-27-2004, 01:21 PM   #10
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this might help

john

attached is a pic with annotations it should explain better what part to remove and inspect/clean.

mind you, mine has electronic ignition so it looks a little different than yours. however, the spiders don't care and will still build nests in the very end of it!

if this doesn't remedy the situation checking your gas pressure would be in order as suggested above.

good luck

john
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Old 12-27-2004, 01:43 PM   #11
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Wonderful suggestions, (and great pic John!). That helps quite a bit. I should be able to figure it out with all this info! I'll keep you all posted.

Thanks!
John
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Old 12-27-2004, 06:42 PM   #12
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Quote:
Originally Posted by krowsea
Wonderful suggestions, (and great pic John!). That helps quite a bit. I should be able to figure it out with all this info! I'll keep you all posted.

Thanks!
John
The operation of a flue is to properly vent the exhaust gases and allow fresh air back in to the combustion chamber. It is possible, if you can't find anything else, that the cover for the flue that you installed is causing an exhaust restriction. It is not getting too much air, it is choking on its own exhaust. This is just a thought, and can be tried if all else fails.
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Old 01-03-2005, 10:10 PM   #13
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Here's an update on the water heater.

Well, I finally got a chance to try a few of the suggestions this weekend, in an attempt to get the water heater to function correctly. I didn't fix it, but it's band-aided enough it appears to work OK for now. Here's the latest;

I took it apart, and checked the gas nozzle, venturi and exhaust vent for damage or obstructions. Everything appeared fine, but I cleaned everything with a gentle brush, and ran a rag or brush through each of the tubes. I did not check the gas nozzle for plugged orifices, as I just now thought about it, and I don't know if there's one hole or mutiple, and if they need cleaning. I'll check that next time.

I reassembled everything, adjusted the air vent slide to get a good (quiet) blue flame. Closed the access door, and within 30 seconds, the flame started to get noisy and flutter again, getting ready to go out. It fluttered and made noise less when the air vent was closed as much as possible. I elongated the adjustment hole in the vent/slider to try closing it even more. With the slider closed completely, turning the flame mostly yellow instead of blue, the heater made much less noise when the door was closed, and actually stayed lit.

Also thinking that the vent cover (rain cover actually) might be restricting the exhaust, I opened the door to expose the exhaust opening, which is a long narrow slit about 1" tall by 6" wide. I completely covered the opening with a large piece of metal, effectively blocking the exhaust, with no change in the flame noise, color or ability to stay lit.

Suggestions, ideas? I would really like the heater to have a nice quiet steady blue flame, 'and' work when the door is closed. I'm not sure how the yellow flame (hotter, colder?) is affecting the heater output, and although the fluttering has been minimized and the flame appears to stay lit, I can't imagine this is the way it's supposed to be.

Thanks for all the wonderful assistance and ideas!
John
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Old 02-10-2005, 02:15 PM   #14
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Anything new on this? I've got an Atwood GH6-4E water heater which will work for maybe 5 mins or so and then just go out. I can ususally turn it off and back on and the flame will work for another few minutes, though shorter. I tried replacing both temp sensers (under the black cover in John's pic) and the igniter senser. Still same, although it did stay lit long enough once for a couple of quick showers.
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