Overheated Melted Connection

mikezusaSeptember 24, 2013

Smelled burning at old dishwasher.Killed power and removed box (very hot to touch) and found neutral connection burned, wire nut melted almost to nothing. Hot connection was not effected at all.

Visually checked the only junction box on that circuit and saw no evidence of overheating. Looked inside panel and saw no evidence of overheating at the breaker either.

I assume it was just a bad wirenut connection or maybe the appliance malfunctioned?? So I snipped off about 4 inches and remade the connection with a new dishwasher (i needed an excuse to buy a new one!).

Do you think I should have replaced the whip/wiring between the dishwasher and the junction box too? Would the wiring have been jeopordized by overheating?

I assume this was a progressive thing until it completely failed. Thanks for any replies, Im still a little freaked out by the burned connection.

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mikezusa

One other thing, dishwasher had aluminum stranded wire.
The new one has the same.

Could that have caused the high resistance?

    Bookmark   September 24, 2013 at 10:04PM
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saltcedar

Tinned copper is what you are seeing. Stranded Aluminum is only AWG 8 and larger I believe.

    Bookmark   September 24, 2013 at 10:22PM
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Ron Natalie

A loose wirenut can heat up like that. Despite the fact that the wires are still twisted together, the twist provides little efficacy to the connection. It's the nut itself that does.

Either it wasn't installed properly, it was the wrong one for the conductors in use, or it got mechanically loosened by vibration over time.

This is why connections need to be made in boxes.

    Bookmark   September 25, 2013 at 7:48AM
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mikezusa

Do you think I should have replaced the whip going to the appliance or was just cutting off the damaged end sufficient?

"Tinned copper is what you are seeing"
Yes the stranded connection was already twisted. I think its probably #18 or 16. I assume the tin it to keep it wrapped like that.

The installation instructions specifically say to not pretwist the wires. So I didnt trim any off the dishwasher side and connected without twisting with a yellow ideal wirenut.

"This is why connections need to be made in boxes."

Most certainly. There was some black contained within the box. When I went to remove the plate, it was very hot to the touch too. A scary lesson for sure.

    Bookmark   September 25, 2013 at 8:02AM
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mikezusa

No visual signs of damage that wasnt already snipped off wire.

Do you think the thermal expansion or heat has weakened the wiring?

Should I have replaced the whip instead of just snipping off the burned portion?

    Bookmark   September 26, 2013 at 1:22PM
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Ron Natalie

No, as long as you have undamaged insulation (and you replace the burned wirenut) you should be OK

    Bookmark   September 26, 2013 at 2:47PM
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