Burnt gfci

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gunpowder

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Glen Rock, Pa
Checking out new job yesterday and gc was handing this around for inspection. Pool outlet& pump plug. First noticed tripped receptacle and burnt connection at bottom. Reset gfi & plugged back into top. Two days later, tripped branch breaker and burnt top receptacle. Replaced plug & outlet - so far everything is running fine.

Floor full of commercial electricians were shrugging shoulders, so i told him I'd put it on the forum to see if y'all could figure it out.
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Gonna take a stab and say that the wire inside the added (not factory) plug had cracked/broken strands, creating a hot spot, tho I've seen several PTACs with factory cords burn the same right-side pin on a 6-20R. Carrier and Amana both have recalls on PTACS for power cords that catch fire. If you think the termination was correct, I'm going with mfg defect in the plug.
 
170816-0905 EDT

gunpowder:

Since you show a 20 A plug and socket this would imply a high current load.

Clearly the problem relates to the hot side.

On the first occurrence why wasn't either or both the plug and socket replaced?

After second occurrence what was seen inside the plug? From the photo the plug was opened, or at least the screws were backed off.

Did you open up the GFCI to see what was burned up inside?

My guess is the fault was inside the GFCI from poor contact pressure.

See my photograph P5 at http://beta-a2.com/GFCI.html for the inside of a Leviton GFCI showing the hot side contacts. Poor spring force could easily cause a high resistance connection and possibly arcing.

Since you see exterior burning of the GFCI I suspect there was an internal problem.

When the plug was opened did you see any burning or arcing where the hot wire terminated to the plug pin?

.
 
you can clearly see the melted hole in the side of the cord cap. I'd say poor connection at the cord cap.
 
I agree with the loose connection theory either in the plug or the GFCI. Loose connections cause arcing and that's what cause's the burning. If it were just an overload that would have tripped the breaker IMHO.
 
What is real crazy is that in the first claim a worker saw the burnt outlet and did nothing but remove the cord from the burnt slot and placed the same cooked cord into a fresh spot.

Let this be a lesson that these type of issues NEVER correct themselves. This instance was very poor practice.

"floor full of Electricians" did this floor full of electricians know the backstory you just told us?
If so I would want to have a training session with those guys. I would be concerned as to their attention to detail and workmanship. "aah it will be ok" or " looks good from my place"

This is fine example of the careless troubleshooting.
 
Sierrasparky said:
you can clearly see the melted hole in the side of the cord cap. I'd say poor connection at the cord cap.
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+1


One side of a connecting device overheats the other side is likely compromised. Both receptacle and cord cap should have been replaced the first time.
 
Sierrasparky said:
... these type of issues NEVER correct themselves. ...
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+1

So many times, something like this happens and it's very difficult to determine what went wrong first, but it's almost never just ONE THING that's bad, especially AFTER an event like this. I think like ptonsparky that it was a bad connection in the cord cap, but maybe it was the receptacle that was bad at first. Doesn't really matter now though. That would have definitely damaged the cord cap anyway so you're right, BOTH sides should have been replaced, never re-used.
 
That is the usual high resistance damage. Sometimes caused by corrosion, but usually a very bad/loose connection. It has noting to do with the GFCI unless it is the GFCI hot side/plug problem of corrosion or internal GFCI loose connection prongs.

When first seen the plug and damaged GFCI ought to have been replaced, and cleaning wire or cutting it back should be done at same time. I have seen this in GFCI's before, and many times in regular receptacles. The same damage happens anywhere there is a very high resistance connection, such as circuit breakers, including the mains, in junction box connections, switches, anywhere for whatever reason there is a very high resistance connection. Evan in underground cables where an electrical leak through the insulation to and adjacent wire eventually creates enough heat to fry the cable and melt the wires. And do it without tripping the CB.

There is no valid excuse for not completely checking out any high resistance damage and replacing/cleaning all that is damaged.
 
I have worked with that exact replacement plug just in the last few days. First time I terminated it, I had stripped wires coming from the back, so I redid it to eliminate that error. When I opened the plug again, I found one hot wire loose already - clearly an installer (me) issue. I reterminated the 6-20 plug and double checked it by pulling on the conductors. You'd think tightening 7 screws (3 on the conductors, 2 on the plug to body connection, and 2 more on the strain relief) would be virtually foolproof, but things happen. Perhaps one wire went in over (instead of in between) the pressure plates.
 
// Floor full of electricians....couldn't figure it out //
:blink: one of those can't be true.

Considering the add-on plug, my bet is installer, one or more of these: wire strands cut off or damaged when stripping cord conductors, terminal screw simply not tightened enough, terminal screw overtightened and stripped the threads, not all the strands were under the pressure plate.

Sometimes those plug terminals are so small and fragile that it's nearly impossible to get the connection right.

I'd much rather install a whole cord which has a factory plug on it
 
James L said:
// Floor full of electricians....couldn't figure it out //
:blink: one of those can't be true.

Considering the add-on plug, my bet is installer, one or more of these: wire strands cut off or damaged when stripping cord conductors, terminal screw simply not tightened enough, terminal screw overtightened and stripped the threads, not all the strands were under the pressure plate.

Sometimes those plug terminals are so small and fragile that it's nearly impossible to get the connection right.

I'd much rather install a whole cord which has a factory plug on it
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I think most of us figured out there was a poor connection, the difficult part of this is figuring out exactly which connection was the first one to fail as the heat from that was conducted to adjacent items.
 
Dinasaur said:
That is the usual high resistance damage. Sometimes caused by corrosion, but usually a very bad/loose connection. It has noting to do with the GFCI unless it is the GFCI hot side/plug problem of corrosion or internal GFCI loose connection prongs.

When first seen the plug and damaged GFCI ought to have been replaced, and cleaning wire or cutting it back should be done at same time. I have seen this in GFCI's before, and many times in regular receptacles. The same damage happens anywhere there is a very high resistance connection, such as circuit breakers, including the mains, in junction box connections, switches, anywhere for whatever reason there is a very high resistance connection. Evan in underground cables where an electrical leak through the insulation to and adjacent wire eventually creates enough heat to fry the cable and melt the wires. And do it without tripping the CB.

There is no valid excuse for not completely checking out any high resistance damage and replacing/cleaning all that is damaged.
Click to expand...

Don't take that "high resistance" thing the wrong way, as the resistance isn't really all that high, if it were the intended load wouldn't work correctly or even not work at all. It is a high resistance in one spot in what is otherwise normally a very low resistance conductive material.

Say one has a 1500 watt at 120 volt load. Then say you have a weak connection in that circuit that is producing 5 watts of heat. 5 watts don't seem like much, but when concentrated in a very small area can still get pretty hot - there are soldering irons that only draw 7 watts.

The resistance of this poor connection is only .032 ohms, the voltage drop across it is only .4 volts if we have 120 volts applied and the intended load is drawing 12.5 amps.
 
kwired said:
I think most of us figured out there was a poor connection, the difficult part of this is figuring out exactly which connection was the first one to fail as the heat from that was conducted to adjacent items.
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For sure. Impossible to determine because we're limited to one picture and a brief description.
 
James L said:
For sure. Impossible to determine because we're limited to one picture and a brief description.
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Speaking for myself, the photo clearly shows the cause and damage both to/of the GFCI and the plug. It shows where the problem was and how it affected the GFCI........ Twice.

The hole burnt through the bottom of the plug at the connection point between cord wire and the plug --- the screw, clearly indicates that the problem was there. Whether it was improperly installed or had been pulled back from pulling on the cord pulling the wire loose or the screw simply had not been tightened correctly to start with, or it had been tightened correctly but the twisted cord wires loosened from heat from use caused the material to contract enough to make the connection loose......... regardless of reason, that is where the problem emanated from. The heat at that point traveled through the neutral pole of the plug into the neutral of the GFCI, burning the GFCI neutral the first time, and melting off the plug neutral the second time, probably assisted by arcing from neutral to neutral due to corrosion on the neutral plug prong.

That happens at non-GFCI receptacles the same as the GFCI ones.

As for the post above giving the ohms of resistance between the contacts........ :lol:

You can give what the ohms ought to have been, but that does not mean squat as to what they were, let alone what the load was. Many of the ones I have repaired were not from high loads at all, but rather low loads over a long period of time. The longer it goes, the more corrosion, or damage from heat happens over time until finally the high resistance is enough to cause the damage or lose the connection completely, or both.

I seldom bother with what the cause was on these past the point of what is necessary to effect corrections necessary to repair.
 
Dinasaur said:
As for the post above giving the ohms of resistance between the contacts........ :lol:
Click to expand...

If you are picking on my post - read it, my point was it doesn't take much resistance to create quite a bit of heat when it is concentrated in a small area.
 
Dinasaur said:
Speaking for myself, the photo clearly shows the cause and damage both to/of the GFCI and the plug. It shows where the problem was and how it affected the GFCI........ Twice.

The hole burnt through the bottom of the plug at the connection point between cord wire and the plug --- the screw, clearly indicates that the problem was there. Whether it was improperly installed or had been pulled back from pulling on the cord pulling the wire loose or the screw simply had not been tightened correctly to start with, or it had been tightened correctly but the twisted cord wires loosened from heat from use caused the material to contract enough to make the connection loose......... regardless of reason, that is where the problem emanated from. The heat at that point traveled through the neutral pole of the plug into the neutral of the GFCI, burning the GFCI neutral the first time, and melting off the plug neutral the second time, probably assisted by arcing from neutral to neutral due to corrosion on the neutral plug prong.

That happens at non-GFCI receptacles the same as the GFCI ones.
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I don't think the gfci would have been any part of the cause, precisely because the damage looks the same on top and bottom

I seldom bother with what the cause was on these past the point of what is necessary to effect corrections necessary to repair.
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Somebody ought to bother with a tutorial for guys who are scratching their heads over something reasonably simple
 
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