Wire insulation melting off

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  #1  
Old 09-07-13, 11:29 AM
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Wire insulation melting off

Today while running some wire for a new closet light, I noticed the insulation is being slowly melted on a 14-2 wire that was laid over the wire that leads to the hot water tank.

The Romex is dry and feels a little brittle where it was touching the old cloth wiring. Fortunately there is enough room on that line I can cut out the bad section and reconnect the the line without much work.

Is this a general cloth wire issue or is a "one off" scenario?

The hot water line is up for replacement next rainy cold weekend when I am indoors all weekend (not many nice days left before the snow comes). I have 3 lines in the house that are still cloth.
 
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Old 09-07-13, 11:33 AM
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That may be the tar from the old cloth wiring. See if it can be rubbed off.

If the insulation is brittle it needs to be repaired or replaced.
 
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Old 09-07-13, 11:34 AM
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Are you saying that the Romex was melted or scorched from touching that cloth covered wire that feeds the water heater ?

If I have that correct..... you have a problem.
The wiring from the water heater should not be getting that hot.
 
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Old 09-07-13, 12:00 PM
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PJmax
Are you saying that the Romex was melted or scorched from touching that cloth covered wire that feeds the water heater ?
Exactly.

The wire is slightly melted on one side and lightly blistered on the other side.

I have slowly labeled all the lines and breakers in the house as I discover how things were done here and did not notice this until I moved the wires apart today as the Romex was just draped over the older wire. For the moment the wires are postitioned in a way so they can no longer touch.

Replacing the hot water wire is on my soon to do list, but I am thinking it just got bumped way up the priority ladder after seeing this.

The underlying question is, is the cloth just bad wire, is it too small for the job, or is it a sign of other issues?

The hot water tank has dual 20 amp fuses at the tank and a 20 amp breaker at the main panel which have not blown in the 2 months or so since I have been in the house.
 
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Old 09-07-13, 12:24 PM
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It may be a small water heater as most use a 30amp circuit.

The water heater supply wiring should not be that hot. It has nothing to do with cloth covered or plastic covered.... wiring should not run hot. Warm......ok. That wire may be small for the job. It is protected properly but I have a feeling it's approaching the continuous use limit of the circuit which is 80%.

A 20amp 240v circuit can deliver 4800 watts. The maximum continous load that should be connected to that circuit is 3850 watts. Look at the size of your water heater elements and you'll know whether the proper sized wire was run.

I'm in a house built in 1958..... still has some original cloth covered cable. Still looks fine. I'm not going to replace it.
 
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Old 09-07-13, 05:24 PM
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The hot water line is up for replacement next rainy cold weekend when I am indoors all weekend
What is the wire size on the water heater circuit? What is the wattage of the water heater, most are 4500 watts and require a 30 amp circuit with #10 AWG wire as was already mentioned.
 
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Old 09-07-13, 05:33 PM
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It is hard for me to tell the actual size of the older wire, it appears to be about the same size as the 12-2 "whip" (it is just basic 12-2 Romex) that connects the disconnect to the tank.

I have attached a picture of the tank label.
It says 3000 per element, and total 3000. So I assume only one element can have full power at any one time and it generally operates at a lower mix of the 2 elements not exceeding 3000 watts if all is running well?
 
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Old 09-07-13, 05:58 PM
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I cannot think of a single reason why #12 wire and 20 amp breaker shouldn't be sufficient for 3000 watts, is it possible the elements have been changed to a higher wattage. I still would suggest that your new circuit be installed with 10-2 NM B cable even if you stay with the 20 amp breaker. If you check around, I think you'll find that most new water heaters are 4500 watts and the old one won't last forever.
 
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Old 10-13-13, 07:28 AM
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Just a quick follow up, and a thanks for the replies.

I replaced the line 2 weekends ago, and changed my daughter's hot water tank wiring this weekend as she had the same old wiring to her tank upstairs.

It turns out the old wire was 14g on a 20 amp line.

I replaced it with 10g in case I ever move to a larger 60 gallon tank.
 
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