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Kenmore 80 gallon water heater problems  Rating:  Rating
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 Posted: Mon Feb 27th, 2012 03:22 am
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Keith Hansen
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My Kenmore Power Miser 12 has started acting up.  First it kept overheating and popping the red reset button for the contact thermostat.  We replaced both heating elements and that fixed it for about a month.  Then the outlet pipe sprung a leak from a bad washer and water covered the top of the water heater and leaked into the connections, shorting them out and throwing the circuit breaker.  I replaced both the hoses just to be thorough, and fixed the green ground wire which had burned through when everything shorted out.  This got it going again, but only briefly.  The bottom element then burned out, probably because I hadn't cleaned out the lime in the bottom when I replaced it and it wasn't getting enough water circulated around it to cool (I think).  So I cleaned out a bunch of lime then put in a new bottom element.  I also replaced the top thermostat with a generic one from Lowe's in case the old one had been damaged by the water.  It started working again, but then it started overheating again and it is again popping the reset button on the thermostat. 

I would think "bad elements" but they are both very new.  The bottom one is brand new, the top one about a month old.  In any case, I checked the resistance on top and bottom thermostats.  The top is a 3800 watt element and showed 13 ohms resistance.  The bottom is a 5500 watt element and it showed 10.4 ohms of resistance.  Anybody have any idea what the resistance readings should be?  Any idea what could be causing this problem now?

Keith

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 Posted: Mon Feb 27th, 2012 07:21 am
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eleent
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Hello:  Check both elements for any current leak to ground.  Use the ohms times 1000 setting.  If there is a leak, that element is not fully shutting off.

Yours,  Larry

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 Posted: Mon Feb 27th, 2012 12:42 pm
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energyexpert
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Keith,

3800 watts = 15.16 ohms
4500 watts = 12.8 ohms
5500 watts = 10.47 ohms

Thermostats must be mounted so as to be tight against the tank so the thermostats "see" tank temperature; any gap at all means tank has to get a lot hotter before the thermostat cycles off.

As you said, an element embedded hard water deposits cannot be adequately cooled. Rewiring from 240 to 120 volts reduces output to 25% of nameplate, which gives time for the heat to dissipate without overheating the element. But you may have to setup for simultaneous operations to reduce recovery time.

David

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 Posted: Tue Feb 28th, 2012 01:26 am
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Geno_3245
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Check wire gauge inside water heater.
The problem could be 5500 watt lower element connected to 12 gauge wire.
5500 watt element will overheat 12 gauge wire and cause ECO reset button to trip.

To check wire size, check wire connections at top of heater. If circuit breaker is 30 amp, then wire from breaker is probably 10 gauge. If circuit breaker is 20 amp, then wire from breaker is probably smaller 12 gauge. Compare wire from breaker with water heater wires at top of heater.

Electric water heaters manufacturers today use smaller 12 gauge wire on some heaters to cut cost vrs using larger 10 gauge wire.
12 gauge is ok for short lengths and with 4500 watt elements, but water heater circuit should have 10 gauge wire and 30 amp breaker for any wattage over 3800.

The upper thermostat ECO will trip if it senses high heat on the wire, or if loose wire or loose connection causes heat.
This is one reason instruction manuals say to use same wattage element that shows on nameplate.

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 Posted: Tue Feb 28th, 2012 11:02 am
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Keith Hansen
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Energyexpert: could the 13 ohms on the 3800 watt element indicate a problem?

Geno-3245: the water heater is factory stock--the bottom element has always been 5500 watts and shows that on the nameplate, so I imagine the wiring is correct for it. The heater is 6 or 7 years old, so it's not of recent manufacture either. It has popped the reset button before, and it was a bad element. I could drain it again (for the 3rd time in as many weeks) to check the elements, but I was hoping to be able to tell with the resistance check.

eleent: How do I check for a current leak to ground?

UPDATE: I turned the heat down and it stopped popping the reset button. But the water temp is 112 degrees, which isn't very hot...

In any case, thanks for all the input. With your help I hope to get this issue solved. I figure as long as the tank is good (no leaks) it makes more sense to repair than replace.

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 Posted: Tue Feb 28th, 2012 12:30 pm
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Geno_3245
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If tank rating is 5500 watts, the wire gauge is not the problem.
I thought you replaced 3800 watt element with 5500, but didn't notice that you have 80 gallon water heater.

The new element could still be heating:
Disconnect wires from elements.
Use ohm tester.
Test each element screw to bare metal part of tank.
If meter reads ohms, then there is a short through the element that is grounding to the metal tank. This will cause element to keep heating even if thermostat turns OFF.
That's because the thermostat only turns off 1 leg in the 240V circuit.
The other leg is hot to element at all times.
In the case that element is shorted to tank, and short if far enough along in the element that it doesn't trip the circuit breaker, then that completes 120v circuit through the metal tank and then to the ground wire, and the element will keep heating.
This causes runaway heating that will trip ECO.
Why would it do that with a new element. I don't know.

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 Posted: Tue Feb 28th, 2012 12:47 pm
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energyexpert
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Keith,
In the US we have come to expect that something is as advertised or specified. I guess that in manufacturing a separate process stamps the wattage on the end of the element. Could 12.8 ohm batch of elements been labeled as 3800 watts vs. 4500? I cannot think of any situation where the resistance would decrease over time.

David

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 Posted: Tue Feb 28th, 2012 01:09 pm
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Geno_3245
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After writing the answer above...
I was looking at your post/ your water temperature is 112 degrees yet ECO is tripping.

That implies that you do not have run-away heating from shorted element.
Run-away heating would cause tank to heat to 150-180 degrees, and then ECO would trip.
But that is not happening.

So it goes back to overheated wire -or- bad upper thermostat.

For example if you had a water leak that shorted parts in tank, that event can partially melt a wire.
The wire is not able to handle the full amp load without getting hot > the ECO detects heat and trips.

You can replace wires fairly easily inside old water heaters that have fiberglass insulation.
Also check that all wires are very tight under the screw plate, and check that two different gauge wires are not under same screw plate, and that no wire-insulation is under the screw plate.

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