My charge adapter melted. Has anyone else had this problem recently?

The cause at this point doesn't matter. The outlet is damaged and should be replaced. I was going to suggest this is a simple DIY but it appears that the outlet setup is something custom made and may not be as simple of buying the receptacle and screwing it in (of course turning the power off first).

Frank Mucus said:

I axed them if the...

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You axed them, did you?

Hard to tell from those pictures, although it does look like the heat was a bit more concentrated inside the adapter. However, it could be due to a loose wire at the back of the receptacle (heating coming forward from receptacle to the adapter), or due to the adapter being loose. Can you take a picture of the rear of the adapter and of the pins in the head of the UMC as well? You might want to shut the breaker off, pull the outlet out, and take a picture of the back of it as well. (Seems like they may have taken the adapter back already, so maybe you can't take a photo of the back... but perhaps the head pins of your UMC?)

And yes - the receptacle will need to be replaced in addition to the UMC.

(If your "licensed electrician" says that everything's fine because the breaker didn't trip, you need to ask him if he got his license from a Cracker Jack box... a loose wire on the back of the receptacle can cause that type of heating through the receptacle and into the adapter without tripping the OCPD. If he never pulled the receptacle to check the torque on the wiring, then he cannot say that for sure.)

I have seen many receptacles that have failed just like that one and much worse.
Personally, I have not seen a UMC failure but if you do a web search they are there.
However, I have seen many failures when the receptacles are used at the upper limits of its current rating.
I was an AHJ in a large research lab where receptacles were used and abused constantly.
I have seen everything from plugs welded into the receptacle to a plug failure that caused a $1M lab fire.
Typically the failures occur with high current resistive element ovens, hot plates, heaters, vacuum pumps and other lab/shop equipment that draws current for extended periods at the upper limits of the receptacles capacity, both 120 & 240Vac.

That I observed the typical failure mechanism is the receptacle fails to make good contact with the plug blade on both sides (only one side is good), causing the one receptacle contact to overheat and loose contact pressure on the plug blade. Once the receptacle is overheated it will not recover and continued use will result as you observed, lots of heat and melted plastic.
Also, the last user of the receptacle could have weakened/damaged the receptacle contacts with a corroded/bad plug but at a less-than destructive amperage and then you insert your UMC and charge at 40 amps so things get real hot. If a blade tension test tool is inserted into the receptacle the blade tension will be very low as the contact tension was annealed by the excess heat. Should the plug insertion ever feel easy/weak when you insert your UMC adapter you may want to think twice before you charge full current or at all.

So why does the receptacle only make contact on one side of the plug blade?
I can only surmise most often it is the plug blade that is corroded or dirty as this can occur on almost newly installed receptacles. The plug blades are unprotected and constantly exposed to abuse, contamination and corrosion when not inserted into a receptacle, hence the corrosion and contamination can easily build up when exposed to the environment.

Is there a solution? well, if the plug blades show corrosion/contamination use a fine scotch bright pad to shine up the plug blades and if you don't need to charge at 40 amps with the UMC, don't. Select something less that will provide the desired charge level over the time you will be plugged in. This practice may not prevent every adapter/receptacle/UMC failure however it will lessen the opportunity for failure as the failure is most often associated with the higher current levels.

m6bigdog said:

I have seen many receptacles that have failed just like that one and much worse.
Personally, I have not seen a UMC failure but if you do a web search they are there.

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Note that the majority of those failures are before the change to the new style adapter. There is still the problem of loosening wires in the receptacle box.

jerry33 said:

Note that the majority of those failures are before the change to the new style adapter. There is still the problem of loosening wires in the receptacle box.

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Yes, yes, without a doubt, having a thermal fuse in the adapter, actively monitoring the supply voltage fluctuation and cutting the charge current back most likely reduces the incidence of catastrophic failures that include the surrounding incidental property and structure.
I anticipate the internal thermal fuse opened on this adapter?

However, 100% is an elusive number as you can see, even with the latest adapter and software the adapter/receptacle contacts can overheat and become damaged during normal use.

We can all hope the EVSE industry, equipment standards and code makers will continue to develop solutions to further reduce the risks of branch circuit and charging equipment failures.

The bottom line is, as long as the only damage is to the electrical devices and no other incidental property or structure was involved; it is as good as it gets as in the big scheme of things.

Unless your consulting electrician took the receptacle apart and examined the wiring behind it, he can't say anything for sure. And if you were to take the receptacle off, you would replace it since it obviously can't be continued to be used.

What Tesla said is correct. The fault could very well lie with the receptacle. A new receptacle costs $10. Reinstalling one takes 20 minutes. Tesla has given you a new free adapter, which is very nice of them.

I'm pretty sure even the new Tesla adapters do not have a thermal fuse, BTW.

I posted this in another thread, but I was speaking with an owner who had his car in for its "annual" and Tesla proactively replaced his UMC's NEMA 14-50 adapter with a new (3rd generation) one. The interesting thing here is he claims this new adapter limits the car to 32 amps when charging. He says Tesla told him that 40 amps is "too much" for the UMC or something like that. And yes, I'm talking about the 14-50 adapter and not the discontinued 14-30 or 10-30 adapters.

Another tidbit is that I was considering a second UMC so I could leave one in the car, but with the price drop (a while ago) I decided to get a HPWC. When I picked it up at my Service Center last Tuesday, I happened to mention my UMC vs. HPWC quandary and they told me the UMC is no longer being offered for sale.

mknox said:

Another tidbit is that I was considering a second UMC so I could leave one in the car, but with the price drop (a while ago) I decided to get a HPWC. When I picked it up at my Service Center last Tuesday, I happened to mention my UMC vs. HPWC quandary and they told me the UMC is no longer being offered for sale.

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It's still available on the US website. There are rumors of a new model coming out when the X in unveiled. Maybe Tesla in Canada is already out of the old model and they will have the new model available once it is released?

MorrisonHiker said:

It's still available on the US website. There are rumors of a new model coming out when the X in unveiled. Maybe Tesla in Canada is already out of the old model and they will have the new model available once it is released?

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I pointed that out to them. When you go to the web site there is this little caveat:



Same deal with the HPWC (have to order and pick up at a Service Center). I could be, as you say, that they're out in Canada and the mothership isn't sending any more of the current style to us.

EDIT: No, I was mistaken. The HPWC can be shipped anywhere in North America. It's only the UMC that is limited to the US.

Very interesting. I know Hong Kong has a special HPWC which is actually a 10kW version. There has been discussion here in other threads that the NEC rules in the U.S. May force Tesla to abandon the UMC. I wonder if the Model X will usher in an era of just a permanently mounted EVSE. If so, it would be nice if Tesla could sell their proprietary car plug in high volumes to portable EVSE manufacturers.

Frank Mucus said:

Yesterday I had another licensed electrician look at it and he said it was the adapter's fault, not the outlet or wiring cause the breaker didn't trip and everything else seems fine.

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Don't use that electrician. He's a complete moron and has no idea what he's talking about. Not only is that not true but breakers themselves can melt without tripping due to bad contact. The breaker will trip when it exceeds x current for y time. It has nothing to do with temperature. This failed due to a faulty connection and nothing more. Could it have been the UMC 14-50 plug? Yes. Could it have been the receptacle? Yes.

Make sure to check the UMC itself to make sure there wasn't melting where it connects to the adapter. With that much heat, there may be damage there too, and if you use a brand new adapter with a brand new receptacle to a damaged UMC, you will just have another melt issue.

NEMA 14-50R device jury-rig mounted (to who knows what? Scheesh!) = Trouble

Frank Mucus said:

How could it be trouble if I was using it for over a year. I said from the beginning he took it apart too.

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Uh, no you didn't (re read your first post). Well, you were using the adapter for over a year too. It had to be either the adapter or the receptacle that had a problem. Actually, it could have been both. Does it really matter? Both need to be replaced.

mknox said:

I posted this in another thread, but I was speaking with an owner who had his car in for its "annual" and Tesla proactively replaced his UMC's NEMA 14-50 adapter with a new (3rd generation) one. The interesting thing here is he claims this new adapter limits the car to 32 amps when charging. He says Tesla told him that 40 amps is "too much" for the UMC or something like that. And yes, I'm talking about the 14-50 adapter and not the discontinued 14-30 or 10-30 adapters.

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I can certainly believe this, based on my own experience with the UMC 14-50 adapter. If I charge at 40 amps, both the adapter and the cable between it and the UMC heat up considerably. Since I don't actually need 40 amps when charging overnight, I dialed back to 32 amps and now it barely even gets warm.