Pictures of melted 14-50r - A reminder to be careful!

[eprosenx]

A friend of mine called me last night for advice on some electrical issues with charging his two EV’s (Honda Clarity and M3). He had his NEMA 14-50r melt down that his Leviton 32 amp EVSE was plugged into (which he uses for both cars). He then changed over to charge both cars off garage 5-15 receptacles (thinking they were on two circuits) and they stopped working but without an obviously tripped breaker.

This is about as close as you come to a house fire without the actual fire.

He lives on the far opposite side of town from me and so I did not have a chance to do the failure analysis myself, but from what he saw he thinks the insulation was shoved too far into the receptacle terminal and so was reducing the contact with the receptacle.

This is the second case of this we have seen on the forums here in the last couple of months. Both installations were done by licensed electricians.

Please treat this as a reminder of how important quality proper electrical installations are. We are dealing with high amperage draws for long periods of time. I don’t want this to scare potential EV owners (gasoline is probably far more dangerous), but we all need to be aware just like we are with gasoline.

Note that had my friend been using his UMC Gen 2 it likely would have detected the overheated receptacle long ago and either backed off the charge rate or killed it altogether. This type of incident really makes me a fan of having the thermal sensor in the ends of the UMC Gen 2 adapters.

For those curious, this is 8 gauge copper NM cable on a 40a breaker. The Leviton EVSE is only rated to 32a. Absolutely a code compliant install (just terminated wrong). (though now I am wondering if that single gang box meets wire fill requirements)

He was able to cut the wires back shorter and install a new receptacle and charge OK last night (used the UMC for the M3 for added safety).

On the 5-15 issue when he tried his backup charging method: He did not have any tripped breakers, but he could not figure out which circuit it was. We were able to determine that a GFCI receptacle near the breaker panel in the garage was non functional, but the test/reset buttons worked (only when the breaker was powered on).

Replacing that faulty GFCI receptacle solved that issue.

P.S. Also another reason I love my hardwired Wall Connector!

 

[gfunkdave]

So, in other words, the outlet installer didn't strip enough insulation away before connecting to the 14-50, which reduced available contact area for the conductor and heated the wire up enough to melt the insulation (and probably start a fire, if your friend were marginally less lucky)?

 

[Vines]

Close call there! Another reason why the temp sensors are important and extension cords are bad.

If the insulation was that melted I'd be tempted to replace all of the wire myself. Its likely that conductors still in the sheath had the insulation melted slightly.

Was this a industrial 14-50 outlet, or the home depot special?

 

[adaptabl]

These type of incidents will become more common as EV adoption increases.

 

[Nocturnal]

Lazy electrician using the back stab instead of using the damn screws. IDK why that is allowed per code. So much more risk of the connection coming loose or having excess insulation.

 

[mongo]

So, in other words, the outlet installer didn't strip enough insulation away before connecting to the 14-50, which reduced available contact area for the conductor and heated the wire up enough to melt the insulation (and probably start a fire, if your friend were marginally less lucky)?

I think the OP is saying the insulation was under the terminal reducing clamping and contact area from copper to terminal.

Lazy electrician using the back stab instead of using the damn screws.

Not for this outlet. The wire only inserts from the back, the screw then clamps into the wire. It's not a spring loaded back stab duplex setup. Note the lack of exposed terminal metal where the screw head would press a wire.

 

[Nocturnal]

I think the OP is saying the insulation was under the terminal reducing clamping and contact area from copper to terminal.



Not for this outlet. The wire only inserts from the back, the screw then clamps into the wire. It's not a spring loaded back stab duplex setup. Note the lack of exposed terminal metal where the screw head would press a wire.

Ah, thanks for the correction.

 

[eprosenx]

So, in other words, the outlet installer didn't strip enough insulation away before connecting to the 14-50, which reduced available contact area for the conductor and heated the wire up enough to melt the insulation (and probably start a fire, if your friend were marginally less lucky)?

Correct. Based on the pictures and information he passed to me on the phone last night our belief is that one or both of the hots did not have enough insulation stripped off them and so it got caught in the terminal clamp. Heat from this poor connection over time melted the receptacle and insulation on the wire.

I don't know what kind of receptacle it was, but my guess it was some cheepie provided by the electrician. My friend had already purchased a replacement at Home Depot (probably Leviton) before I got a chance to get him on the phone. He needed it working last night so he installed what he had (he has a long commute and was low on juice). As long as he stripped it properly and torqued the terminals properly I doubt he will have further issues.

Btw, I think the failure mode was that eventually enough insulation melted off that the hots touched (or hit ground) and blew the breaker. Scary.

 

[StellarRat]

The electrician isn't going to test the circuit with a full load. They'll just use a volt meter to make sure all the voltages are right. I guess that just goes to show that nothing is perfect.

The one my brother and I installed was from Home Depot and I know for a fact that there is no insulation near the terminal ends since I was there when we stripped the cable and attached it to the plug.

 

[MorrisonHiker]

So he just reused the existing wires? When should the wires be replaced (if ever) after some of the insulation is melted?

 

[eprosenx]

So he just reused the existing wires? When should the wires be replaced (if ever) after some of the insulation is melted?

He cut as much of the damaged part of the wire off as he could (limited slack available). You really want to replace all the wire that could have been overheated...

He just messaged me that he contacted the electricians that did it and he is discussing them come back out and replace the entire run to his breaker panel and at the same time upsize it to #6 AWG and a 50a breaker just for good measure.

 

[Vines]

So he just reused the existing wires? When should the wires be replaced (if ever) after some of the insulation is melted?

Copper is VERY conductive, so if any of it is burned through the jacket I wouldn't trust any of it. All it takes is a stress point and that portion of the insulation will be thinner as it got gooey when the wire overheated. If there was pressure on the wire at that location the pressure would cause the gooey insulation to deform and get thinner.

 

[eprosenx]

Copper is VERY conductive, so if any of it is burned through the jacket I wouldn't trust any of it. All it takes is a stress point and that portion of the insulation will be thinner as it got gooey when the wire overheated. If there was pressure on the wire at that location the pressure would cause the gooey insulation to deform and get thinner.

I totally agree.

I will call out though: This overheating was caused by a bad terminal connection, NOT overload to the wire itself. So the damaged section should be limited to the distance that heat would have conducted down the wire. (but yeah, that could include up into the wall)

 

[Vines]

I totally agree.

I will call out though: This overheating was caused by a bad terminal connection, NOT overload to the wire itself. So the damaged section should be limited to the distance that heat would have conducted down the wire. (but yeah, that could include up into the wall)

Agree, if there is any damage, its likely within the first few feet of the wire. If the wire experienced thermal runaway that is a different scenario, and most likely the breaker would have popped first.

 

[eprosenx]

Here is a photo of the wires removed from the melted connector.

It is extremely clear that the neutral and one of the hot wires was clamped into the insulation and not just bare copper.

 

[ai4px]

Lazy electrician using the back stab instead of using the damn screws. IDK why that is allowed per code. So much more risk of the connection coming loose or having excess insulation.

I’ve never seen a 14-50 that used stabs.... there are slots in the back and the screws pinch the wires.

 

[roblab]

This is why I like to do my own simple electrical work. I have lots of time, not trying to make $400 and hour, can test and wiggle and test again. Most electricians don't care NEAR as much as I do about how the wiring works. I have seen this for 55 years. Not slamming electricians, but I know pressures can work against taking time.

 

[StellarRat]

Here is a photo of the wires removed from the melted connector.

It is extremely clear that the neutral and one of the hot wires was clamped into the insulation and not just bare copper.

View attachment 353332

Sure is. A partial connection with high power going through = HEAT! Ohms Law and all that bit.