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Rick, HVAC Supervisor
Category: HVAC
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Experience:  40+ yrs. experience as a licensed oil & gas technician.
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My electric A.O. 80 gallon heater keeps turning off. It was

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My electric A.O. Smith 80 gallon heater keeps turning off. It was working fine, then suddenly stopped producing hot water last week. Plumber has been out twice, replaced heating elements and put in new upper thermostat. They checked amperage and power. After working for a day, it stopped again.
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: Yesterday they checked and reset upper and lower settings. I don't know about filters, where are they?
JA: Do you plan on doing the work yourself?
Customer: No, the parts were under warranty and they didn't charge me. We've used them for years. I haven't called them back yet about latest. I could try and punch the red button on upper thermostat again. Seems like something weird is going on, though.
JA: Anything else we should know to help you best?
Customer: Just what different kind of things could cause this. I read up on troubleshooting. It seems like something is causing the thermostat to trip.

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continue our conversation.

Did the plumber replace the lower themostat?

Customer: replied 1 month ago.
I am not sure. He did say something like "every thing in it is new now," I know for sure he replaced at least one thermostat.
Customer: replied 1 month ago.
the heating elements are new

If the heater is turning off via the overtemp reset button then he probably didn't replace the lower thermostat. If you get it going again by hitting that reset (on the upper thermostat) then one of the 2 thermostats is malfunctioning. It's pretty common for the plumber to assume only the upper stat is bad if the reset keeps tripping but the lower can make the water too hot just like the upper.

Customer: replied 1 month ago.
I will ask if they replaced lower. If they did, do you know of any other factors that might cause this to happen. I thought of electric power surges, but nothing else in the house has been effected; tv, ac, microwave all working normally.

If you get it going by hitting the reset then it's a thermostat problem. Is that how you get it to work? Anything else would be much more difficult to correct. There's a slight chance you have a bad breaker but that would tend to be a more permanent failure.

Customer: replied 1 month ago.
OK, one last question. If I want to punch the reset button myself ( I know where it is) do I need to turn breaker off, or can I just punch button?

Just push the reset. Do not turn off the breaker. If the reset is tripped it will click when you push it. If it doesn't click it either wasn't tripped or the new thermostat is faulty. Be careful to not touch any wires but the newer units have plastic gaurds to cover the wiring so touching the wires isn't likely.

Customer: replied 1 month ago.
Will do, thanks. This is helpful. It sounds like if it turns out not to be the thermostats, it might be cheaper to buy a new water heater. Right now its not costing me anything.

You're welcome. I'd have an electrican check out the breaker and the wiring before buying a new unit. For the price of a minimum call (should only take him 1/2 or less) you can be sure the wiring or the breaker is not the problem.

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