Dishwasher wiring all of a sudden overheats and melts

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rmgolob

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I'm very fortunate I believe.
A couple of years ago we re-ran the water line to dishwasher with some new braided hose.
Never got around to replacing the kick plate and I believe that was fortunate procrastination.

Recently while running dishwasher my wife noticed red glow and smoke at the wiring. Shut it down and found the below pictures.

No clue what happened although we can speculate that the wiring was "disturbed" by routine broom sweeping or mopping.

No, it was not appropriately in a "box" and it will be once fixed.

The breaks in the jacketing was not the cause, but rather a result. The black was "fused" to the white where the breaks are.

ANY clue as to what did / could have happened?

Semi-Sidebar question. It looks like the green was wired in with the whites. That may or may not have been. I'm not sure from the pictures. Should it be?

Thanks in advance,
Rob

Dishwasher wiring 1.JPG
Dishwasher wiring 2.JPG
Dishwasher wiring 3.JPG
 

Stuff

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The green should not be with the whites. Should be somehow electrically attached to the cable sheath and isolated from white neutral. Blue wire is unusual. Does that cable just come out of the wall or is there a box? Should verify that the sheath is grounded.

Looks like a problem with a loose wire nut. People don't screw them on tight and then think that electrical tape will keep it together.

Might have been aggravated by a failing dishwasher. I've heard that there are issues with older units leaking current to the chassis ground. Maybe the green was loose but didn't matter until the motor insulation started to deteriorate. Supposedly part of the justification for GFCI protection of dishwashers in newer electrical codes.
 

JRC3

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Yep, too often people do not get wire nuts nearly tight enough. Pull the burnt wire nut and insert off and the wires should be twisted together. If they are basically parallel to one another then the nut was not tight enough. Just curious, are the blue and white wires in the flex conduit are solid or stranded.

I would cut out the bad and reconnect. That conduit connector needs bolted to the box. Probable gonna need a 90 degree type conduit connector too.
 
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rmgolob

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The green should not be with the whites. Should be somehow electrically attached to the cable sheath and isolated from white neutral.
I looked again at the green wire and I'm quite sure it was wired with the Whites. It is charred just like the others. I will attach it to the sheath. I assume I can screw it onto the elbow connector screws in the picture below?

Blue wire is unusual. Does that cable just come out of the wall or is there a box? Should verify that the sheath is grounded.
The cable comes through the floor but I believe it is properly configured. The whole house is hard conduit. There is a dedicated 20 Amp Dishwasher breaker and from the source it is conduited to a box on the basement ceiling and from there the cable sheath goes to the main floor with the Blue and White wires.
(The kitchen ceiling fan has a Yellow hot. House was high end will built in 1976.)
Pictures below.
Conduit Elbow.JPG
Wire Box.JPG
Wire Sheath.JPG

Looks like a problem with a loose wire nut. People don't screw them on tight and then think that electrical tape will keep it together.
I will make sure connection is tight to the best of my ability. Is there a "best quality" wire nut?
Might have been aggravated by a failing dishwasher. I've heard that there are issues with older units leaking current to the chassis ground. Maybe the green was loose but didn't matter until the motor insulation started to deteriorate. Supposedly part of the justification for GFCI protection of dishwashers in newer electrical codes.
How can I determine if the unit is "leaking current?" Is that a safety must?
 

rmgolob

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Yep, too often people do not get wire nuts nearly tight enough. Pull the burnt wire nut and insert off and the wires should be twisted together. If they are basically parallel to one another then the nut was not tight enough. Just curious, are the blue and white wires in the flex conduit are solid or stranded.

I would cut out the bad and reconnect. That conduit connector needs bolted to the box. Probable gonna need a 90 degree type conduit connector too.
Thanks JRC3.
I don't remember if they were parallel or not.

I will make sure they are tight. I think I asked above, but are there better quality wire nuts?

The Blue and White in the conduit are solid and the Black, White, Green from the dishwater are stranded.

I have added a 90 deg (Picture in previous post) and will insert it into the hole in the "box" attached to the dishwasher.
Thanks!
 

hj

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The white wire is a "neutral" connection and as such it does NOT, nor can it "short out" to any metal surface. Therefore, for it to get that hot the connection must have been loose creating a high resistance which overheated it.
 

Stuff

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The best thing to do would be to pull a new ground wire through the flex and conduit. If not an option then the flex can serve as a ground if local rules allow. Then the right angle connector you added connecting to the box would count as part of the grounding path with the locknut secured to the box. The green/yellow wire would not be needed. As mentioned, strip the wires back and use new wire nuts.


I'm in the south hills of Pittsburgh - Century III area. I was just at the Oakdale Diner a week ago.
 

WorthFlorida

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Yes, it does seem the wire nuts were not properly twisted as every one stated but the electrical tape probably trapped moisture which aggravated it. I would pull the wires back to the juncture box and run new wires to the dishwasher but that is your option. If you have enough wire after cutting the burned ends and the copper looks clean then you can use it but I like to be safe. If not, at least open the juncture box to see if there are any wire nuts. Normally stranded wire is not run all the way back to the breaker let alone blue color wire.

A dishwasher doesn't use much power until the heated drying cycle or when it is heating the water. To be sure that the dishwasher is good and not taking excess current, get your self a clamp meter. Lowe's and HD have basic units for the DIYer, so they are only about $40. After you reconnect everything put the clamp around the black wire and run the dishwasher. When the heating elements are on it may be around 15 amps. The electrical rating plate will list the power or current needs. I wouldn't know what it should read when only the motor is running but I would guess it be around 4 to 5 amps. With the model number you maybe able to find it on the manufactures web site. It is possible that the heating elements are on all the time due a bad timer or relay.

54940d24-8467-46f1-a208-d393c6210e85_145.jpg
 
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WorthFlorida

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I just realized that the wire is solid (Blue and Wht). This type of burn is usually not "all of a sudden", it's being going on for a long time. You happen to be there just at the final failure.
 

JRC3

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This type of burn is usually not "all of a sudden", it's being going on for a long time.
Yep, and good bump with a broom may have made the bad connection even worse causing the final failure. Not good for the appliance either.
 

JRC3

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I had to add this and resurrect this thread...

OK, I bought this foreclosure to live in and have done tons, and still needs tons of work. Moved in last Labor Day and have done without a dishwasher since. So I installed an OK LG dishwasher today and found this in the crawlspace feeding the old dishwasher. I knew it was suspect but the breaker has been off and the old unit has been gone for months...

Sorry the first pic is out of focus. No wire nuts; Only twisted and taped. :eek:
 

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WorthFlorida

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That's unreal. I would sure look around the rest of the home for other hacks.

So where did the blue wire start?
 
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