ELECTRIC WATER HEATER, burnt wire at upper thermostat?


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Old 02-14-13, 02:47 PM
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ELECTRIC WATER HEATER, burnt wire at upper thermostat?

This morning, NO HOT WATER. Went to breaker, it was RED-OFF. I reset, it returned to RED-OFF.

I removed both heater covers, and noticed at the upper thermostat that two wires had burnt insulation, and were shorting out against each other. I moved the wires away from each other, and both wires had some bare copper exposed. Nothing that was near broken.

I reset the breaker, and it stayed on. I waited an hour, and hot water is available.

I flipped the breaker to OFF, and wrapped the two wires with electrical tape. I took a light tester and touched the two screws going into the elements, and I didn't get a red light. Should I get a reading if the water is hot, and the thermostat isn't supplying current to the elements? Is that how it works?

Thank You for hearing me out. Your comments are most welcome,

Dale in Indy
 
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Old 02-14-13, 03:15 PM
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What gauge wire is it? Should be at least 10 GA. Anything smaller like 12 or god forbid 14 GA could cause the wire to overheat and melt the insulation.
 
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Old 02-14-13, 04:02 PM
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Thank You,

What about my other question concerning current to the elements? Are they dead when water in tank is HOT?

I will remove the burnt wires, and check Ga when I replace them.

Thank You,

Dale in Indy
 
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Old 02-14-13, 04:26 PM
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On the upper thermostat, the 2 terminals that your incoming wires are connected to should always read 240v between them. I believe the other 2 terminals on the upper thermostat will only read 240v when the water in the top of the tank has reached the set point.

From that second set of terminals you should have wires running to the lower thermostat. With the upper stat off and power now being sent to the lower stat, if the water in the bottom of the tank cools below the set point, the lower element begins to heat the incoming cold water.

Only 1 element is ever "on" at a time.

Which wires were burnt? The incoming power or the ones between the thermostats?
 
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Old 02-14-13, 04:38 PM
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My explanation may have been a bit too simplified. The diagram here under A-6 is probably similar to what you have if it is a standard residential hwh,

http://www.hotwater.com/lit/wiring/315267-000.pdf
 
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Old 02-14-13, 07:05 PM
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It's the A-6 thermostat. The wires that made contact are the UPPER HI-TEMP LIMIT SWITCH BLACK WIRE, and it burnt through the RED line to the right.

It appears to me that the Black wire got hot first, and laying up against the Red, it started to burn through it, it melted a 1/8" hole in the Red insulation, and then threw the breaker, IMO.

The Black wire looks to me to be 12 Ga at most.

Thanks,

Dale in Indy
 
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Old 02-14-13, 07:19 PM
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It may be # 12 wire and if it is.......it's wrong.

If your water heater is on a two pole 30 amp breaker then the wire needs to be # 10.
# 12 will run hot.....as you have found out.

I see # 12 all the time on water heaters......I don't know what people are thinking when they do that. Maybe cost... ...... certainly not safety.
 
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Old 02-14-13, 08:18 PM
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It is a two-pole 30 Amp. breaker. I will replace the wires with 10 Ga. in the morning.

Thanks,

Dale in Indy
 
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Old 02-14-13, 10:41 PM
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IF this #12 wire to which you refer is part of the original water heater wiring from the factory it IS the proper size. The wiring used inside an appliance is NOT required to follow the same NEC rules for premises wiring.
 
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Old 02-15-13, 06:31 PM
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Furd is right. The original factory installed wiring probably has a higher temperature rated insulation than premises wiring would have as well. If you are replacing the original wiring with type THHN, yes, I would use #10 too.
 
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Old 02-17-13, 09:37 AM
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Ok, I replaced the two short wires, and all seemed GOOD.....

Now I notice that when I turn on the COLD water, it is WARM, not HOT, and it takes forever to return to COLD.

Could one of the thermostats gone BAD? I am assuming the hot water is backing up into the cold inlet side????? I will go check to see how the inlet line feels, temp wise.

Dale in Indy

P. S. I just checked, COLD inlet line is very warm. I pulled the service plate for the upper element & thermostat, and the wires seem ok. I noticed the temp was set on the lowest stetting which is 110 degrees. I am now wondering if this has caused my electric bill to be higher than in the past.

Help! Thanks, P.S. It is a 52 gallon unit, so I threw the breaker until I hear info, or need more hot water.
 

Last edited by Smith Brother; 02-17-13 at 10:04 AM.
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Old 02-17-13, 10:16 AM
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110 degrees is pretty low for a HW tank.
The EPA recommended temperature is 120 degrees.

As water in the tank heats up it expands and as it expands it forces its way back up the cold water inlet tube. A pretty common event.

Now by code an expansion tank is installed on the cold water side to alleviate this problem.
 
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Old 02-17-13, 10:56 AM
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Ok, but we have lived in this home for 35 years, and the cold water has always been cold when called for.

I am wondering if maybe the upper thermostat isn't shutting down current to the element?

We have plenty of hot water with it being set at 110 degrees, I will check the setting on lower one now too.

Something has changed to cause this, NEVER BEFORE has cold been hot.

Thank You,

Dale in Indy
 
 

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