Heating element runs continuously

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  #1  
Old 02-09-09, 12:46 PM
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Unhappy Heating element runs continuously

First sign of trouble was the limit switch activating. I reset and checked out the elements. Both around 17 Ohms which looks good. Upper thermostat checked out, so I replaced the lower thermostat. Everything seemed to work okay, but I could hear that an element wouldn't turn off. At this time I measured the following: 0 volts across upper element (good). 120 volts across the lower element, and 120 volts across the lower thermostat. Not so good. Obviously the thermostat is working (opening once the water is hot) but the element is still forming a circuit. Could this be a partial short somewhere in the element? How can there be a 120V drop across the element with the thermostat open? Another measurement: resistance from black to ground on the upper element is 26 Ohms. Same measure on lower element is 9.6 Ohms. Resistance from red to ground is 7.4 Ohms for both.
Thanks for your help.
 

Last edited by bassman99; 02-09-09 at 02:27 PM. Reason: clarification
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Old 02-11-09, 04:16 PM
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Replace the upper thermostat.

You have to understand how an electric WH works. From dead cold, the upper thermostat kicks on the upper element. Once that has heated to its set temp, the upper 'stat kicks off the upper element and kicks on the lower. If you can hear it continuously running, the upper 'stat isn't kickin' off the upper element and kicking on the lower.
 
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Old 02-15-09, 07:25 PM
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Smile

Thanks for your response. I have managed to fix the heater and it has been working well for three days. The problem was a short between the lower element innards and the copper casing which permitted current to flow through part of the element to ground. that's why there was a 120 voltage drop across BOTH the element AND the thermostat when the thermostat was open. Replacing the lower element fixed the problem.
 
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