water heater problem


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Old 01-26-18, 07:22 PM
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water heater problem

I have a hot water heater that is blowing fuses. I checked the elements with an ohmeter and can't find anything there. I was wondering about the thermostat. would that cause a circuit to blow a fuse? there is no water out of the relief valve. If I plug in the fuses it will start the water heater and heat the water, but the disconnect in the fuse box gets so hot you can't touch it. any thoughts? am I looking in the wrong place? let me know. thanks
 
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Old 01-26-18, 07:28 PM
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Did you try using your ohmeter from each side of each heating element to ground? I.e. hold one end to a metal part of the water heater, and the other end to one side of the heating element, then repeat for each side of each heating element. If there's a path to ground anywhere then that's the issue.
 
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Old 01-27-18, 03:05 AM
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I tried testing the elements with an ohmeter, got continuity through the elements. I will check this morning between the elements and the tank. what is the reason to check both screws on both elements?
 
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Old 01-27-18, 04:32 AM
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Ordinarily both elements are never on at the same time. If the top thermostat goes bad and allows both elements to heat at the same time you will trip the breaker or blow a fuse.

The element has a metal wire in the center surrounded by insulation and all inside a metal tube. Each end of the wire is connected to one of the wire attachment screws. The outer tube is grounded via it's metal to metal contact with the water heater. When an element burns out it usually is a complete burn out and it will show completely open on an ohm meter when testing on either screw. There is a remote chance that the element wire breaks and touches or welds itself to the outer steel tube. In that case checking one screw to ground would show open (no continuity) while the other screw when tested to ground or the element body (big mounting hex) will show les resistance than the element should because there is less heating wire to resist the flow of electricity. It's not a full shorting out but the element can draw much more current than it should.
 
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Old 01-27-18, 03:07 PM
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For this measurement, label and unhook all wires from both element terminals before wielding the meter probes.

Also check and tighten up all the small and medium sized screws and set screws in the panel. An experienced person should do the big screws that hold the main feeder wires. If a screw seems already tight, then loosen it a quarter turn and retighten. (Do not use tremendous or stupendous force, which will strip the threads.)

A very hot breaker that does not trip suggests a loose connection near or at that location as opposed to an overload. For a disconnect consisting of a pull out block that holds cartridge fuses, the prongs and matching slots could be too loose and if so you will need to upgrade and replace immediately.

Most all-electric water heaters take 30 amp fuses.
 
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Old 01-28-18, 04:47 AM
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it turns out it was the top thermostat. I went back and rechecked the elements and they were all right, so I changed the upper thermostat and everything worked fine. thanks for the help.
 
 

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