Charging cable overheats

[stopcrazypp]

I have charged on Leviton and other non-industrial but UL listed NEMA 14-50 outlets at 40A consistently over 5+ years without heat or current reduction issues. One key thing that could make a difference is how often you plug and unplug from the outlet. I rarely unplug.

That does make a difference (given 14-50 is not designed to be frequently plugged/unplugged; even the industrial ones don't have a cycle rating), but having half size contacts probably lowers the margin for error (both in terms of plugging, and also in terms of if the screw terminals in the back are not tight enough), which is likely why the Leviton outlet seems to disproportionately fail.

Note for other non-industrial outlets, most of them have full size contacts, even the $10 ones.

 

[3sr+buyer]

Most 14-50 receptacles, including the Leviton 279-S00 with half size contacts, claim to be "industrial grade" (for example, see https://www.leviton.com/en/products/279-s00 ). So please don't use "industrial grade" to describe which receptacles are good.

 

[WVhybrid]

Only if it's installed with wiring connections tightened properly.

I think the Hubbell specifies the required torque on the side of the socket. I bought a torque screwdriver to make sure the connections were correctly tightened. It took a big effort to tighten enough to reach the "click" set point on the screwdriver. The extra cost of a Hubbell socket falls into the "don't burn your house down" bucket.

 

[cali8484]

I think the Hubbell specifies the required torque on the side of the socket. I bought a torque screwdriver to make sure the connections were correctly tightened. It took a big effort to tighten enough to reach the "click" set point on the screwdriver. The extra cost of a Hubbell socket falls into the "don't burn your house down" bucket.

No doubt Hubbell is a better outlet design but other UL listed outlets can also work safely with proper wiring and connection. Certainly outlets with larger contact area will be more tolerant to inadequate wiring and connection but that's not really a valid substitute proper wiring and connection. All UL listed NEMA 14-50 outlets certified to UL 498 must pass stringent testing including 30C rise limit at rated/continuous current (i.e. 50A), 150% current overload, 7 hours in 70C environment without degradation and accelerated aging tests. So, unless there is an UL or NEC warning for a particular brand/model, all UL listed NEMA 14-50 outlets with proper wiring and connection should be able to handle EV charging at 40A without problems. Even the NEMA 14-50 outlet with short contacts have more than adequate surface area and thickness to handle 40A but only with proper wiring and connection. Having said that, it can be more difficult to make proper wiring and connection on some UL listed outlets including Leviton due to their design but that does not mean such outlets are inherently unsafe. People who have experienced failure of an UL listed outlet and believe it's an inherent problem then they should certainly report it to UL for investigation.

 

[3sr+buyer]

Having said that, it can be more difficult to make proper wiring and connection on some UL listed outlets including Leviton due to their design but that does not mean such outlets are inherently unsafe.

Leviton 279-S00 outlets have half size contacts to the plug blades, which can result in overheating at the front of the outlet (rather than the back if the wire connections are not done properly). Regardless of how careful the installation is, the half size contacts to the plug blades will be less conductive, giving more resistance and heat. They may also be more prone to misalignment when a plug is inserted or removed, compared to full size contacts.

 

[Mull031496]

There are many cases of vehicles and devices that perform well in the strict confines of a controlled testing environment and then behave quite differently when placed into service in the real world. These poor performing receptacles may be one example of that.

 

[ahostmadsen]

My conclusion: I will have an electrician (either the one who installed the outlet, or someone else) check the wiring, and if it's OK I will ask them to install a higher quality outlet.

 

[Sti-g]

1) it’s not designed for sustained max load for hours like what an EV demands. Other 240V equipment might spike high load for short periods but generally run much lower.

2) it’s not designed to have things repeated plugged and unplugged like you might do for an EV charger. Typically 240V equipment gets plugged in and never moved again. Plugging and unplugging wears down the contacts and causes arcing.

Exactly. Things like ovens and cloth dryers take max amps for 10-20 minutes or less and once they reach desired temperature, they draw much less current. EV charging is max current for hours…
When I got my TWC installed, electrician wanted to use 6AWG wire but I insisted on 4AWG due to this fact.

 

[ahostmadsen]

I did not get around to fixing the outlet, and this is the result... Definitely the outlet problem. Now I will get an electrician to install the Hubbell recommended by Tesla. Thanks to Tesla for having the overheat protection, otherwise this could have resulted in serious consequences.

 

[stopcrazypp]

View attachment 1023927
I did not get around to fixing the outlet, and this is the result... Definitely the outlet problem. Now I will get an electrician to install the Hubbell recommended by Tesla. Thanks to Tesla for having the overheat protection, otherwise this could have resulted in serious consequences.

Yep, very clearly overheating from the outlet from that picture. If you look at the outlet, I would expect there is also some melting of the plastic there. This is what half sized prongs on the Leviton outlet can result in, as I and others warned you about.

Note you don't necessarily have to get the Hubbell, the Bryant is pretty much the same thing, just rebranded, so you can get that also if it's less expensive.

Note the diameter of the circle is bigger, but it seems your outlet cover can accommodate that by snapping off the plastic ring.

 

[ahostmadsen]

Yep, very clearly overheating from the outlet from that picture. If you look at the outlet, I would expect there is also some melting of the plastic there. This is what half sized prongs on the Leviton outlet can result in, as I and others warned you about.

Note you don't necessarily have to get the Hubbell, the Bryant is pretty much the same thing, just rebranded, so you can get that also if it's less expensive.

Note the diameter of the circle is bigger, but it seems your outlet cover can accommodate that by snapping off the plastic ring.

I guess I will also have to buy a new Tesla 14-50 cable. They are not cheap, and Tesla seems very slow with shipping. Meanwhile have to trickle charge.

 

[stopcrazypp]

I guess I will also have to buy a new Tesla 14-50 cable. They are not cheap, and Tesla seems very slow with shipping. Meanwhile have to trickle charge.

You may be able to clean off the carbon (may need to scrape off with knife or even use some mild abrasive) and still use it for now, although it may be safer to replace it if possible.

 

[ahostmadsen]

Perhaps to beat a dead horse, but this is how the outlet looks inside. The point is: when Tesla warns of overheating, it should be taken seriously. And: how can an outlet rated for 50A burn like this when use at 32A? Now I replaced it with the Hubbell that Tesla recommends, and hopefully no more overheating.

 

[MP3Mike]

And: how can an outlet rated for 50A burn like this when use at 32A?

It most likely was not installed correctly. (That the terminal was not properly tightened. You really have to tighten it, wiggle it, loosen it, and then tighten it to the specified torque. Otherwise, the normal heating cycles causes the strands to shift a little and loosen, which causes more heat, lather, rinse, repeat, fire.)

 

[3sr+buyer]

View attachment 1030372
Perhaps to beat a dead horse, but this is how the outlet looks inside. The point is: when Tesla warns of overheating, it should be taken seriously. And: how can an outlet rated for 50A burn like this when use at 32A? Now I replaced it with the Hubbell that Tesla recommends, and hopefully no more overheating.

That looks a lot like a Leviton 279-S00 with half size contacts to the plug blades. These lesser contacts increase resistance and heat, regardless of how carefully they are installed.

A Hubbell 9450A or just about any other receptacle will have full size contacts. The Hubbell 9450A and a few others* also have a pressure clamp mechanism to hold the wires that makes them easier to install properly than the common screw down connections.

*Bryant 9450FR and Leviton 1450R.

 

[ucmndd]

That looks a lot like a Leviton 279-S00 with half size contacts to the plug blades. These lesser contacts increase resistance and heat, regardless of how carefully they are installed.

All true, but that looks like the heat/arcing source was clearly at the conductor lug, not the plug blades.

Not torqued to spec, insulation pinched in the lug, or other installation error seems to be the obvious culprit in this case.

 

[PianoAl]

View attachment 1023927
I did not get around to fixing the outlet, and this is the result... Definitely the outlet problem. Now I will get an electrician to install the Hubbell recommended by Tesla. Thanks to Tesla for having the overheat protection, otherwise this could have resulted in serious consequences.

Interesting thread. Thanks for updating, Madsen.

Can someone explain why that plug needs to be replaced rather than just cleaned up.

 

[Cosmacelf]

Interesting thread. Thanks for updating, Madsen.

Can someone explain why that plug needs to be replaced rather than just cleaned up.

Because it is melted? I don’t really understand the question. It is a product manufactured to specific safety tolerances. If part of it is melted, you can’t have any confidence it will continue to work correctly.

 

[PianoAl]

Because it is melted? I don’t really understand the question. It is a product manufactured to specific safety tolerances. If part of it is melted, you can’t have any confidence it will continue to work correctly.

I don't see any melting. The plug not the outlet. Sorry if I wasn't clear.

 

[Cosmacelf]

I don't see any melting. The plug not the outlet. Sorry if I wasn't clear.

Sorry, I can’t read apparently. Yeah, I agree, looks like it could be cleaned up.