Water heater won't shut off at set temperature

[Bruce and Jenna]

I have a ten gallon Atwood propane/electric water heater GE16EXT in my 2007 Excel fifth wheel. Recently I have noticed that the water heater does not shut off as expected, rather keeps running and creaking. I have only noticed this in electric mode, as I seldom run it with propane.

I read the manual, as I know NOTHING about water heaters. I see a part called Thermal Cut-off. That's what I need!

Before I call a repair guy or Atwood, anybody have any ideas on a cause here? Any test I can perform? My water heater wiring does not look like the picture in the manual, so I can't poke the Therma Cut-off even if I want to.

Thanks much.

[Flagelpater]

On my unit the temp sensors are located in the front, 2 wires each, behind a black rubber foam pad. Is your thermal relief valve releasing water? Do you know what the temperature of the water is at the kitchen faucet?

[Bruce and Jenna]

OP here,

Just tested this in propane mode - same problem with gas too.

[Bruce and Jenna]

Quote:

Originally Posted by Flagelpater On my unit the temp sensors are located in the front, 2 wires each, behind a black rubber foam pad. Is your thermal relief valve releasing water? Do you know what the temperature of the water is at the kitchen faucet?

"Front" meaning the access panel on the outside of the trailer?

TPV does not release water. Which I guess means it shuts off sometime, eh?

But water is much hotter than usta be.

[Flagelpater]

Yes, outside, the door where the exhaust comes out. Replacing the temp sensors is an easy job. You can get replacements at most RV dealers. Check your actual temperature at the kitchen faucet first. I would not leave the unit powered ON unless you are using hot water.

[Roadking]

Bruce -- I believe from the model number you listed you have the new Attwood HWH that uses a new electronic control module that uses a single Thermostat and ECO (emergency cut off) to control both the propane and the 110VAC heater. This model HWH no longer has the separate ECO with the manual reset button that was located in the back of the old style HWH's.

The part called a "thermal cut off" (TCO) is a device that looks like a diode and is wired in series with the T-stat and the ECO. THe TCO is a safety device, a temperature FUSE. The TCO opens if the temp behind the cover exceeds the TCO rating, which I believe is 190 degrees F. If the TCO open it will not reset, it must be replaced. If the TCO opens you will have no heat in either propane or AC.

The T-stat and the ECO are bi-metal disc devices that open at temperature and automatically close when the temperature drops. These devices are not adjustable. The TSTAT should open at 140 degrees (plus or minus about 5) and will close at 110 degrees (plus or minus about 5). The ECO should open at 180 degree (F) and reset at about 150. These bi-metal discs usuallly fail in an open mode, and hence, with your unit you would have no heat in either propane or Ac mode.

Pulling the lever on the TPV should release water. Normally there is an air pocket at the top of the tank, but eventually water should come out. I know it's a dumb question, but are you sure there is water in the HWH?

You state the HWH does not shut off as expected. What is "expected"?? With cold water it is possible the heater may run 30 to 60 minutes, or more, before it reaches temperature. 140 degrees is really hot and most likely hotter than what most home hot water heaters are set at. Let it run awhile longer... much longer than "expected".

[Gary RVRoamer]

The regular thermostat controls the base on/off cycle, so that is more likely your problem rather than the thermal cutoff. The thermal cutoff is there in case the t-stat fails - an "heat fuse", as Roadking says.

[Bruce and Jenna]

I think you're right on target here. A friend with the same trailer and water heater told me yesterday that he had the same problem. He replaced the circuit board, which you described as containing the thermostat. He also replaced the (much cheaper) sensors but said it wasn't necessary. He also showed me that both parts are easy to replace.

As for other questions, yes I have water in the HWH. I'm living in the trailer, so use the heater all day. Thus I also notice how often it is running. As in most of the time; as in all night long, when we're not using the water; as in the morning when I first get up.

I'llfind a thermometer to double check the water temperature from the kitch faucet before spending $100+ for a new board. Pretty sure something ain't workin' like it usta.

Thanks to all three of you for your help, particularly Roadking for the lengthy comprehensive answer. I plan to save that info for future reference.

[Roadking]

Bruce: II'll try to be brief, but I believe this is a simple test for the T-stat adn ECO. Look a the wiring diagram on the water heater. You should notice 12 Volt DC Power comes from the on/off switches to the controller board via a series circuit consisting of the TCO, ECO, and T-stat. If you believe the water is up to temperature, i.e. above 140 degrees F, then with a DC meter you should be able to check the voltage as it progresses thru each of these devices. The T-stat should be open, meaning you would have 12VDC on one leg and nothing on the other. If the T-stat remains closed, then this would be your problem. If the T-stat is open and the heater is still producing heat, then the controller is most likely bad. Hopefully this is brief and will help you.

[Bruce and Jenna]

Thank you very much Mr. King. I will pursue this method with a knowledgeable assistant. I'm not so handy with my tester that I want to risk burning out my controller. :> Of course, then I would feel certain about replacing it!

[Ray,IN]

The most common cause is the thermostats come loose from the tank. (TURN IT OFF FIRST) Remove the access panel, locate the small panel covering the thermostat and remove it. Gently move aside the insulation allowing you to see the thermostats. Feel them to see if they are loose or pulled away from the tank. If they are, replace them/it firmly against the tank, replace everything and try it again.

[Bruce and Jenna]

Quote:

Originally Posted by Ray,IN The most common cause is the thermostats come loose from the tank. (TURN IT OFF FIRST) Remove the access panel, locate the small panel covering the thermostat and remove it. Gently move aside the insulation allowing you to see the thermostats. Feel them to see if they are loose or pulled away from the tank. If they are, replace them/it firmly against the tank, replace everything and try it again.

Kewl. An easy first step. Thanks!