A Water Heater Mystery

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fraxinus

Feeling the Heat
Aug 3, 2007
341
coastal Maine
The electric water heater in question was installed 7 years ago. At the time, the factory setting on the thermostat seemed to be too low, so I turned it up a bit until the water was at 120 degrees. All was fine until three days ago. Suddenly the water temp was much higher - between 135 and 140 degrees. I turned the thermostat down to the original factory setting and the water has remained at 120 since. I am at a total loss to explain this. Anybody?
 
it functioned "normally" for 7 years? then suddenly got hotter?

if so... probably corrosion products someplace(s). thermocouple (or whatever is reading storage/output temp) may have some buildup that if affecting it, or had a buildup which came off, and is just letting it react differently. Similar for the element itself - could be starting to go, and giving an odd response to the controller.
 
I'd guess bad thermostat. I've had some stick closed before and overheat the water so that water blew past the bypass valve. The thermostats are cheap, available at most hardware stores, and easy to replace. Just remember to turn that breaker off first.
 
Most electric water heaters have two separate elements and two separate thermostats. One thing that can happen is that an element will corrode to the point the electricity can short circuit through the water uncontrolled.
 
Thanks for the replies. Yes, "normal" function for 7 years, then sudden increase in temperature. It was not as if the thermostat had completely stuck, either. Watched water temp with a thermometer for a couple days because I was concerned things would just get hotter and hotter - the temperature held at just below 140. The really odd thing was that the original factory setting was supposed to have produced 120 degree water; it was 10 to 15 degrees below that. Thinking the calibration was off, I turned it up to the point where the owner's manual said temp should be 140. This produced 120 for 7 years then suddenly started producing 140. Back to the original factory setting now producing the 120 it was supposed to from the beginning. I'm sure corrosion, failing element, etc. could produce all of this, but little mysteries like this one do tend to drive a bit crazy.
 
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