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Dishwasher melted wire

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  • Oct 14th, 2017 9:08 am
[OP]
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May 31, 2005
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Dishwasher melted wire

While operating my dishwasher, it suddenly turned off, no power at all. Checked the breaker box and the breaker wasn't tripped, I turned the breaker off anyways.

Checked the connection inside the junction box and the wire looks like it overheated and burned through the orange wire connector. Is it worth it to fix the connection and try the dishwasher again?
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12 replies
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Dec 12, 2006
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Looks like some of the black wire is chared.

I would strip back the wires past the chared parts, twist wires together with plyers and use a new connector, ( you could use some electrical tape around connector and wires - not required and overkill )

At same time I would redo the white connection with new connector as well.

This could had been caused by a loose connection arching, but I would monitor for a while.
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Oct 14, 2010
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It seems clear that the source of the heat was entirely within the Marrette connector. The wires did not overheat, except near the heat source. This is almost 100% likely to be caused by a loose connection, since heat is caused by current travelling through a resistance P=I*I*R.

Like "theguyz" said, you should cut of the burnt section of wire in order to access some nice shiny copper (i.e. low resistance) and make a new connection. Assume the white wire was connected the same way (poorly) and redo that connection as well.

Edit:

Just wanted to explain the theory a little better.

You probably have a 20 amp breaker protecting the dishwaher circuit. Normally ther is 15 amps of current flowing through this connection (the 2 black wires, and the 2 white wires) so the breaker never trips.

The resistance between the 2 black wires should be 0 ohms when it is properly done. So the formula for Watts (P=I*I*R) is 15*15*0 or zero Watts.

If your connection had just 2 ohms of resistance (which is relatively small) the Watts= 15*15*2 or 450 watts of heat will be produced. If you have ever touched a 450 watt light bulb you have an idea of how hot that is.

So this type of damage can occur without tripping the breaker and without any fault in the dishwasher.
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Feb 11, 2007
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GTA
+1 for a poor connection. Redo the marrettes properly and you should be OK.
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Can this happen with a loose connection when wiring up ceiling lights?

A lot of times the wires provided are pretty thin and it's difficult to pre-twist before marretting them.
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[OP]
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May 31, 2005
94 posts
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Thanks for all the kind advice so far. I'm glad that I can give re-doing the marrettes a shot to avoid having to shell out for a new dishwasher.

The dishwasher had been running for 5 years prior (installed by previous owner) so I'm surprised it took so long for the loose connection to surface.
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Oct 14, 2010
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RCGA wrote:
Oct 8th, 2017 4:22 pm
Can this happen with a loose connection when wiring up ceiling lights?

A lot of times the wires provided are pretty thin and it's difficult to pre-twist before marretting them.
Heat is produced every time electric current flows through an electrical resistance. That is the principle behind kettles and toasters. So yes, it can happen in a ceiling light connection.

When wiring up ceiling lights I normally just wrap the thin stranded wire from the lamp, around the solid copper wire in a spiral fashion. I don't try to twist the solid wire. I then take the proper sized Marrette, (which is smaller than you normally see inside a switch box) and twist it on until it is quite tight. The Marrette packages normally have a chart which shows what combination of different sized wires can be used with each size of Marrette.
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dimsumboi wrote:
Oct 8th, 2017 6:37 pm
The dishwasher had been running for 5 years prior (installed by previous owner) so I'm surprised it took so long for the loose connection to surface.
In the case of a dishwasher, there are a couple of things working against maintaining a good connection.

The first is the constant vibration which may have shaken the Marrette loose. The second is the proximity to moisture which may have caused some corrosion inside the connection which created the higher resistance.

I have never wrapped a Marrette with electrical tape, because I have never seen the need for it. However this may be a case where wrapping with tape might be recommended. The tape should help stop the Marrette from unwinding , and reduce the amount of moisture that gets into the connection. Perhaps even a coating of No-Ox would be beneficial.

Despite having said that, I haven't heard of dishwasher connections having a higher failure rate than any other type of connection, so probably the previous owner just did a poor job.
[OP]
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May 31, 2005
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Just wanted to update, I re-did the connections as suggested and the dishwasher works again. I replaced the orange connectors with yellow ones since the connecting wires are 1x 14 gauge and 1x12 gauge, which may have been too much for orange connectors only rated for 3x 14 gauge.

I do have a 15 amp breaker protecting the circuit. I'm surprised at the symptom when the Marrette melted was that the dishwasher no longer worked, but the breaker didn't trip. Or based on Rick007's calculations, the Marrette didn't get hot enough to trip the breaker?
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dimsumboi wrote:
Oct 12th, 2017 10:46 pm
Just wanted to update, I re-did the connections as suggested and the dishwasher works again. I replaced the orange connectors with yellow ones since the connecting wires are 1x 14 gauge and 1x12 gauge, which may have been too much for orange connectors only rated for 3x 14 gauge.

I do have a 15 amp breaker protecting the circuit. I'm surprised at the symptom when the Marrette melted was that the dishwasher no longer worked, but the breaker didn't trip. Or based on Rick007's calculations, the Marrette didn't get hot enough to trip the breaker?
A breaker trips when too much current is drawn. The bad connection wasn't drawing enough extra current to trip the breaker.
An energy star dishwasher should be under 10A draw.
That leaves 4A that could go to heating the bad connection, which could be 100 ohms, so 4*4*100=1600 watts of heat being dissipated at the marette.
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dimsumboi wrote:
Oct 12th, 2017 10:46 pm
Just wanted to update, I re-did the connections as suggested and the dishwasher works again. I replaced the orange connectors with yellow ones since the connecting wires are 1x 14 gauge and 1x12 gauge, which may have been too much for orange connectors only rated for 3x 14 gauge.

I do have a 15 amp breaker protecting the circuit. I'm surprised at the symptom when the Marrette melted was that the dishwasher no longer worked, but the breaker didn't trip. Or based on Rick007's calculations, the Marrette didn't get hot enough to trip the breaker?
Melting is due to heat. Heat doesn't take a lot of amperage -- e.g. a hobby soldering iron is only about 40W enough to melt "metal" and certainly plastic.

Just a loose connection in the wire nut meaning whatever current draw there was (normal dishwasher draw, not enough to trip breaker) was going through a very small cross section of conductor due to poor contact. So lots of heat generated, due to the physics of electrical conduction, sort of like the very tiny filament in an old-style light bulb.
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Aug 30, 2012
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Langley
Had a similar situation, one day my Bosch DW stopped working. Long story short the installers from "The Brick" should not be hard wiring appliances if there not trained electricians....

https://imgur.com/a/TKexU

Mains wire from the house had its jacket stripped way back and loose conductors popped through the hole terminated without any sort of cable clamp or relief....

I mean f***s sake i'm not a electrician and the Bosch tech said my solution was perfectly fine but he installed a new unit anyways....

Had some trouble getting out of warranty service from Bosch until i found that outlet box (Bosch supplied proprietary power connector) and sent it them, after they saw that I had a tech at my door next business day LOL....
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Oct 2, 2013
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Montreal
Would a AFCI breaker prevent this ?

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