water heater pops circuit breaker


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Old 08-28-14, 01:10 PM
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water heater pops circuit breaker

I think I know what's wrong but I would like some confirmation. I followed the time honored troubleshooting technique I used in the USN when we had a circuit breaker popping in an aircraft. I started disconnecting and reconnecting stuff until the breaker no longer popped. In a nutshell here is what I found. If I disconnect the leads to the bottom heating element the breaker no longer pops. I metered both elements for resistance. The upper reads about 17 ohms. The bottom element reads infinity. Both also read infinity to ground. So would I be safe in assuming the bottom heating element needs replaced? It's a bit puzzling to me because I expected the bottom element to be shorted to ground but it wasn't. Feedback welcome. Thanks in advance.
 
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Old 08-28-14, 01:28 PM
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Yes, replacing the elements is the next step in troubleshooting. If nothing else just to rule them out before replacing more expensive parts.
 
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Old 08-28-14, 02:27 PM
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Thanks for your quick response. The heater element costs $15 so it will get replaced. Thanks again.
 
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Old 08-28-14, 03:30 PM
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The bottom element only kicks in after the top element is satisfied so you won't get an ohm meter reading until this element kicks in.

Is the water very hot after the breaker trips? If so its the t stat and not the element.

You said you disconnected a wire from each element and did a continuity test on each?
 
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Old 08-28-14, 03:45 PM
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The circuit breaker pops immediately. The water never gets hot. The top heater element has a small resistance. The bottom element has infinite resistance. Both have infinite resistance to ground. That's with both wires disconnected from the heater elements.
 
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Old 08-28-14, 05:46 PM
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Like Mike mentioned..... the top heating element is active first

The top heating element stays active until the temperature set on the top thermostat is reached and then that thermostat turns off the top element and activates the bottom thermostat and element.

An open element will not cause a short.

You should be using a high resistance setting or the auto setting on your meter. You would have to have resistance to ground to trip the breaker. Did you try turning power back on with both wires off the lower element ?

If ok now..... the lower element is shorting thru the water to ground.
 
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Old 08-28-14, 08:12 PM
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Infinite resistance to ground proves that neither element is shorted to ground. Infinite resistance between the terminals of an element proves the element is open (no good). I think you have a wiring fault.
 
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Old 08-29-14, 03:18 AM
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Yes, I turned power on with both wires disconnected from the bottom element and the breaker doesn't pop. IIRC, I think I used various meter resistance settings. If I see an infinite reading I usually automatically switch to a higher resistance range however I'm not certain. Once I verified that the breaker no longer popped with the wires disconnected from the bottom heater element I figured I had found the problem. Unfortunately the tank is a 40 mile round trip from where I am now. It's in a house I'm trying to get moved into.
 
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Old 08-29-14, 08:14 AM
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Since you powered up with both wires disconnected you pretty much confirmed a defective element. A diagram just fyi.

Name:  Water heater wiring.jpg
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Old 08-29-14, 11:07 AM
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Thanks PJmax. I looked over a website for water heater repair guide that had some photos. I still find it puzzling that the breaker pops but the lower element is open instead of shorted to ground. In any event I have a new element and wrench so I'll try to get back out there next week. Thanks again for the diagram.
 
 

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