[Broccoli1]

What causes a Plug to melt?

Got a company telling me that the Voltage was too high on one leg:dizzy:
(Single phase 120v fed from 3 phase 120/208)

 

[aevald]

Hello Ed, not that I am an expert by any means. I have been told from various individuals with some knowledge that that sort of thing can occur when a 3 phase panel has become unbalanced by running too many unbalanced loads from it(operating single phase equipment without alternating the loads on each of the legs). If you happen to be shy of single phase plugs in a particular shop you may simply not connect one of the legs of the 3 phase plug to run your equipment. If this is done too many times and the averages of which leg may have been dropped stack-up to leave a particular leg of the panel highly out of balance you might end up with an elevated voltage on one of those legs, although that in itself doesn't necessarily explain the melting of your plug.
A lot of the time though a plug will melt like that from having one of the terminals loosen up over time and cause a poor connection and excessive heat to be built up causing the melting. I'm sure more knowledgable folks will likely reply and I look forward to their input along with you. Good luck and best regards, Allan

 

[Broccoli1]

I told the guy it was probably a loose terminal but they want to charge me 20 bux to repair it:angry:

This is Photo equipment on set at Sony studios, Union electrician= no unbalanced loads at least not to the extent that it would pose a problem.

39 other pieces of equipment running just fine, this particular brand smoked the plug, no big deal, loose plugs happen ( Rental equipment= bunch of dudes yankin' cords out by the cord and not the Plug) but to come back at me and tell me it was High Voltage

Anyhoo:drinkup::drinkup:

 

[Oldiron2]

I'd guess a loose contact under the plug's screw too.
I can't see details in your picture too well but am wondering if the melting point of that plastic is a bit too low for safety.

A bad contact between the plug's blade and the contacts in the socket can sometimes transmit a fair amount of heat to the plug; I've seen the inner contacts get softened from overheating due to prolonged near-overload currents and later cause problems with different equipment having lower loads.

 

[welds4d]

Too high of an amp load can melt a plug as well, if it's plugged in to a circuit with too big of a breaker, or the breaker is bad and won't trip.

 

[Broccoli1]

These types of Plugs always come loose at some point with the amount of use/abuse they see:laugh:

I replace a few throughout the year- just wear and tear- I don't charge my clients- it is just regular use and maintenance.

 

[Birdwell4]

X2 on an overamp condition most likely caused by a loose connection in the plug.
also 20 to repair? you could get that plug at home depot for 8 bucks tops and it would take all of 3.5 minutes to fix it.

 

[Fat Bastard]

Heat is what I have found to be the cause of melting.

 

[Broccoli1]

Heat is what I have found to be the cause of melting.

:drinkup:

 

[Sandy]

Loose lug/screw.

 

[tkanzler]

Are you sure it wasn't tapped off the wild/high leg of the 208V system?

 

[bigb]

Something was loose. could be a lug screw, a loose, worn out receptacle, a loose receptacle screw, a backstab coming loose, or it could be not enough strands remaining after the wire was stripped to install the cap. The recep should be pulled out of the wall and checked/replaced, and the cord cap replaced.

There's an old electrician saying "loose wires start fires"

 

[Billdacat]

I would also agree on a loose coneciton...BUT... I noticed the cable to be a Euro-cable/cord. I can't remember the Euro color code for hot and netural; it might be worth checking into.
Thinking out loud; the device and cord may have been rated for 220V...110 will double the amperage and may overload the plug body. (15 amp plug on 20 amp circuit)

 

[duaneb55]

Heat is what I have found to be the cause of melting.

:laugh:
. . . unless you're the Wicked Witch of the West in which case it's water.

 

[rlitman]

I would also agree on a loose coneciton...BUT... I noticed the cable to be a Euro-cable/cord. I can't remember the Euro color code for hot and netural; it might be worth checking into.
Thinking out loud; the device and cord may have been rated for 220V...110 will double the amperage and may overload the plug body. (15 amp plug on 20 amp circuit)

That plug was NOT original to that cord.
The cord appears to be from an IEC computer cord. The type with one end that plugs into the back of a computer with an IEC C13 connector (the computer would have a C14), and a NEMA 5-15 connector MOLDED onto the other end.
That's a replacement plug.

The International wiring ICC color code states that blue is neutral, and brown is line, and green with a yellow stripe is ground, SO, that plug has it's polarity reversed.

That's not the cause of the melted body though. That's caused by a loose connection. That plug is easily capable of handling a sustained 20A load, whereas that wire appears to be only 16 gauge, so if the voltage (and therefore current) were too high, the wire would surely have melted first.

 

[Broccoli1]

The wiring looks correct since the Brown wire terminates on the Brass Screw.

No Hi leg 3-Phase

This is the item

 

[Broccoli1]

This where/what we use on stage for the equipment that requires a "standard" household receptacle

 

[rlitman]

The wiring looks correct since the Brown wire terminates on the Brass Screw.

Then someone messed with that plug. Assuming that is a NEMA 5-15 (I can't see all three prongs to be sure), and the ground is on top, the prong closest to the camera is the neutral.

 

[Broccoli1]

Then someone messed with that plug. Assuming that is a NEMA 5-15 (I can't see all three prongs to be sure), and the ground is on top, the prong closest to the camera is the neutral.

Thanks for pointing that out- I think the Silver screw Looks brown since it is picking up the color of the bench- this is their photo they sent me.

 

[Fat Bastard]

Heat in electrical circuits is caused by resistance. Resistance if from pushing more energy through than the device is able to handle?

So the wires were too small, the connections were too small or lose?