20A GFCI outlets keep melting the Neutral on the faceplate?

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PGates

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United States
Buffet line in commercial kitchen. There are (2) commercial grade 20 amp GFCI's which share a neutral tied to a 2 pole 20A breaker, fed by 12 awg thhn wire in EMT conduit. The kitchen plugs in the food warmers at meal times. They draw less than 20 amps, the breaker never trips. Over time, the neutral on the faceplate of the GFCI's keeps melting. I have replaced the GFCI's more than once. The wires are undamaged but the faceplate where the N plug goes in melts. What is going on?
 

Sierrasparky

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Location
USA
Occupation
Electrician ,contractor
Buffet line in commercial kitchen. There are (2) commercial grade 20 amp GFCI's which share a neutral tied to a 2 pole 20A breaker, fed by 12 awg thhn wire in EMT conduit. The kitchen plugs in the food warmers at meal times. They draw less than 20 amps, the breaker never trips. Over time, the neutral on the faceplate of the GFCI's keeps melting. I have replaced the GFCI's more than once. The wires are undamaged but the faceplate where the N plug goes in melts. What is going on?

Poor cord cap connection.
Also could be a problem with a loose neutral also since it is a MWBC and there is a splice or more in the circuit.

Let us know what you find.
 

charlie b

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. . . the neutral on the faceplate of the GFCI's keeps melting.
I don't quite understand what this means. I think when you say "faceplate," you are not talking about the cover that goes over the receptacle and hides the outlet box from view. What is melting? Is the front face of GFCI receptacle melting in the vicinity of where the neutral pin on the cord cap is inserted? Is it happening to both GFCI receptacles? When you say the items draw less than 20 amps, do you mean each food warmer or the two of them together? Is one food warmer plugged into each receptacle, or are both plugged into the same receptacle?
 
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GoldDigger

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Location
Placerville, CA, USA
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Is it possible its not a MWBC and both hots are on the same leg?

That would possibly do it if the receptacle was used for a neutral feed through.
No indication that the equipment (individual cords) is anything but 120V, so double neutral current in the cord is less likely.
 

fmtjfw

Senior Member
That would possibly do it if the receptacle was used for a neutral feed through.
No indication that the equipment (individual cords) is anything but 120V, so double neutral current in the cord is less likely.

We saw a fair number of warmers melting down 20A 125V receptacles. We replaced the receptacles and plugs with 20A 125V locking (which is much beefier than the straight blade versions), and the problem never reoccurred.

The warmer cords typically go to the bottom of the rack and provide a lot of pull that tends to pull the plugs down and partially out of the receptacle. Also they are usually run for hours.

This would mean you would have to move the GFCI protection up stream of the receptacles.
 

Electric-Light

Senior Member
You didn't say how often they get unplugged/plugged.

There was the same exact problem with some 120v plug-in electric vehicle chargers too. They're meant to utilize the maximum draw allowed on 120v receptacles.

Unlike golf cart or forklift chargers, 120v receptacles are apparently not designed for heavy load that gets unplugged every single day.

A high quality solid pinned plug end and screw terminal mount helps good thermal bond to the wires which help spread the heat throughout the length of cord and wires in behind the receptacle to limit temperature rise. Good internal connection within the receptacle helps reduce heat generation as well as help conducting it away.

Get receps/plugs rated F(UL)S (Federal Specifications grade) like those sold as industrial or hopsital grade.
 

PGates

Member
Location
United States
mystery solved, bad cord cap

mystery solved, bad cord cap

Took apart the GFCI receptacles. Definitely melting from the outside in. Kitchen was using a homemade extension cord and plugging it in and unplugging it to clean multiple times a day, apparently a bad connection in the cord cap. No one knew where the cord went. It turns out the fireman took it as an example of what not to do. Thank you for your help and suggestions! :)
 
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Electric-Light

Senior Member
Took apart the GFCI receptacles. Definitely melting from the outside in. Kitchen was using a homemade extension cord and plugging it in and unplugging it to clean multiple times a day, apparently a bad connection in the cord cap. No one knew where the cord went. It turns out the fireman took it as an example of what not to do. Thank you for your help and suggestions! :)

Even factory made extension cords are using crappy materials these days. Molded cord ends are usually crummy made. You'll know when you see they're folded in half over the tip instead of single piece machined brass. A quality plug will cost $10-15 a piece.

So, industrial grade receptacle + plug should do the trick, but even these are not rated for using the cord as the pull chain.
 
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