Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Scary issue with Nema 14-50 adapter melting

qwk

P130DL
Dec 19, 2008
3,024
766
At this point in time(over 30k UMC's out there), there isn't really much Tesla could do but supply band-aids for the UMC, which they are doing. The biggest flaw with the latest UMC's are the tiny power carrying pins that the adapters attach to. They work as long as you keep the adapter flush, but overheat when there is a gap.

A simple adapter/UMC redesign that involved a thread-on connection of the adapters to the UMC would have solved the majority of their issues, but now that would involve handing out 30+k free UMC's, which I'm sure that Tesla wants to avoid, hence the band-aids. This is a classic case of when cheap becomes very expensive.
 

William13

Active Member
Mar 19, 2011
1,003
86
South Bend
I expect that Tesla will eventually need to replace many UMCs with a better design. They have known about the melting connections for over one year. New UMCs could be better and slowly replace our old design. I won't need a new one for years as I have a HPWC.
 

EarlyAdopter

Active Member
Jun 24, 2012
2,818
2,047
Redmond, WA
Do we know for certain that the source of overheating has ever originated from the connections between the adapter and UMC body? I haven't seen conclusive evidence that ruled out the source of overheating possibly coming from the wall socket in any of the cases.
 

Grendal

SpaceX Moderator
Jan 31, 2012
5,755
7,016
Santa Fe, New Mexico
Do we know for certain that the source of overheating has ever originated from the connections between the adapter and UMC body? I haven't seen conclusive evidence that ruled out the source of overheating possibly coming from the wall socket in any of the cases.

If you're even the least bit worried have a professional electrician do an evaluation. The connection between the wiring, adapter, and UMC body are all electrical and an electrician is the proper judge for such things.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Do we know for certain that the source of overheating has ever originated from the connections between the adapter and UMC body? I haven't seen conclusive evidence that ruled out the source of overheating possibly coming from the wall socket in any of the cases.

Yes. In the case of my melted UMC about 9 months ago, there was no sign of melting from the front of the adapter - it was all at the rear of the adapter, where it attached to the UMC head. If heat were generated in the receptacle, I would expect there to be signs of melting up front (on the adapter prongs) as well, or heat stress signs on the wire insulation behind the receptacle, etc. My receptacle and the 14-50's prongs looked almost good as new, but the adapter was melting.

This was when I first found the melting:
CameraZOOM-20130419114733733.jpg


This was last April. Tesla first replaced the adapter, and then the UMC.
 

ACDriveMotor

Member
Aug 11, 2013
893
28
Seattle, WA
This may be old news to many but hoping this helps some newer owners...

I have not had melting problems but I have noticed that the retaining clip on the UMC is very easy to bend. In my opinion tat happens because of the odd way to remove and re-attach adapters. You press the button to remove the adapter but must not press the button when re-attaching an adapter or you will bend the retaining clip. If the clip bends rather than seat itself with a click, the adapter will not be properly attached for a tight connection. It is not obvious from the outside when this happens. The friction of the adapter will keep it attached. However I did note that there was a very slight gap between the adapter body and the UMC head.

To fix this situation I had to very carefully bend the retaining clip back into place without breaking it in order to get a proper connection.

I checked the manual and it does give proper instructions - but how many people read the manual? Note also that this was not demonstrated to me as part of delivery - so maybe I am a rare case.

In my opinion the retaining clip is likely to be a common source of problems for some.
 

efusco

Moderator - Model S & X forums
Mar 29, 2009
5,421
666
Nixa, Missouri, United States
This may be old news to many but hoping this helps some newer owners...

I have not had melting problems but I have noticed that the retaining clip on the UMC is very easy to bend. In my opinion tat happens because of the odd way to remove and re-attach adapters. You press the button to remove the adapter but must not press the button when re-attaching an adapter or you will bend the retaining clip. If the clip bends rather than seat itself with a click, the adapter will not be properly attached for a tight connection. It is not obvious from the outside when this happens. The friction of the adapter will keep it attached. However I did note that there was a very slight gap between the adapter body and the UMC head.

To fix this situation I had to very carefully bend the retaining clip back into place without breaking it in order to get a proper connection.

I checked the manual and it does give proper instructions - but how many people read the manual? Note also that this was not demonstrated to me as part of delivery - so maybe I am a rare case.

In my opinion the retaining clip is likely to be a common source of problems for some.
Interesting, I'll have to take a look b/c it certainly seems that the retaining clip is an issue. About 2 times out of 3 the NEMA 14-50 adapter will just slide out without pressing the button despite being fully seated. I'll take a look.
 

JimLovewell

Member
Mar 24, 2014
14
0
San Leandro, CA
This is from another post


Please don't hack off the UMC's wall plug socket without understanding that there is a fourth control pin with the following resistance values to ground:

Tesla UMC Plugs Resistance

40 amps - 9.08k ohms

24 amps - 33.16k ohms

16 amps - 75k ohms

12 amps - 140k ohms

After reading this tread I am more convinced than ever that this issue is really not going away (even with the new adapter that Tesla says they will be sending out). I also have been fighting a hot adaptor. I keep cleaning the contacts with contact cleaner and the temperature goes down 5 to 10 degrees C. But, several weeks later its back being hot again. The hottest my connector has gotten was two weeks ago, 68 degrees C (154 degrees F). That is much too hot. I also notice that if I don’t charge over 2.5 hours the temperature never gets over 53 degrees C (127 degrees F). This morning I charge for 4 hours and 15 minutes (the straw that broke the camels back) and the temperature was to 63 degrees C (145 degrees F).
It is a poor design to have two contacts (14-50 and round pins) within thermal conduction within one another. I have decided it worth a $100.00 to cut the Tesla 14-50 adaptor off and replace it with a Hubbell HBL9451C 14-50 plug (plus the signaling resistor). This will get me to just one set of contacts to worry about and will run much cooler (and I need peace of mine to be safe). Note, I am running another 14-50 plug at 48 Amps. and it only runs at 35 degrees C (95 degrees F). It is crazy that Tesla would design this substandard part. And I don’t see how it got through UL testing. Note my ambient temperature runs between 22 to 25 degrees C.
 

EarlyAdopter

Active Member
Jun 24, 2012
2,818
2,047
Redmond, WA
Jim,

Have you had your wall side of the outlet inspected? There's a chance the overheating you're experiencing is due to faulty wall connections and you're observing heat being conducted back into the adapter through the plug prongs. Those prongs are good for conducting heat too, not just electrons.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Note, I am running another 14-50 plug at 48 Amps. and it only runs at 35 degrees C (95 degrees F).

48A continuous load? You shouldn't be doing this on a 50A rated receptacle.

I agree that the adapters introduce another potential for resistance. When you say "within thermal conduction within one another", wiring naturally provides a thermal conduction bond. Perhaps there is more room for dissipation if you make the distance between adapter and 14-50 plug greater, you might dissipate high-resistance heat across more of a surface, but it will still have its issues.

Check your receptacle prongs to ensure they're tight, receptacle wiring is tight and torqued well.

We'll know soon how the adapters have changed things... if there is still a problem, the reports of melting will be replaced by reports of the fuse burning through.
 

JimLovewell

Member
Mar 24, 2014
14
0
San Leandro, CA
Jim,

Have you had your wall side of the outlet inspected? There's a chance the overheating you're experiencing is due to faulty wall connections and you're observing heat being conducted back into the adapter through the plug prongs. Those prongs are good for conducting heat too, not just electrons.

Hi EarlyAdabter,
Yes, I did inspect my outlet when I installed it a year ago. At that time both contacts average around 0.50 mOhm of resistance (each contact power dissipation was under 1.0 watt, good). Today, one of contacts varies from 1.00 to 7.55 mOhm of resistance when I plug into it several times (the other contact is still fine, always below 0.50 mOhm). The power dissipation on that high resistance contact can be as much as 12 watts, bad). On inspection of the contacts (under a microscope) I cannot see any oxidation. The metal coating is still shiny.
On the Tesla round contacts, I cannot measure them because I cannot get to the leads (yet) unless I cut it off. When I get my new Hubbell HBL9451C 14-50 plug I will cut off the Tesla “fancy adapter and its mate” and leave enough lead length so I can measure the Tesla round contacts too. So, more data to come on this. I will also be able to use the “cut off adapter mate” to test Tesla’s new adapter and compare it to the old one when I receive it. Note, on charging at work I only need the 14-50 plug. So, on one of my Tesla Universal Chargers it makes sense for me to cut it off the “fancy adapter and its mate” (especially since I am having a heating issue) and use a good low contact resistance Hubbell plug (I have had very good luck with Hubbell parts in the past).

Wish me luck.

Best regards, Jim.
 

Lloyd

Well-Known Member
Jan 12, 2011
6,258
2,048
San Luis Obispo, CA
48A continuous load? You shouldn't be doing this on a 50A rated receptacle.

I agree that the adapters introduce another potential for resistance. When you say "within thermal conduction within one another", wiring naturally provides a thermal conduction bond. Perhaps there is more room for dissipation if you make the distance between adapter and 14-50 plug greater, you might dissipate high-resistance heat across more of a surface, but it will still have its issues.

Check your receptacle prongs to ensure they're tight, receptacle wiring is tight and torqued well.

We'll know soon how the adapters have changed things... if there is still a problem, the reports of melting will be replaced by reports of the fuse burning through.

Are the new adapters "Fused" or breaker style that will automatically reset when cooled? I understood they were breaker style.
 

JimLovewell

Member
Mar 24, 2014
14
0
San Leandro, CA
48A continuous load? You shouldn't be doing this on a 50A rated receptacle.

I agree that the adapters introduce another potential for resistance. When you say "within thermal conduction within one another", wiring naturally provides a thermal conduction bond. Perhaps there is more room for dissipation if you make the distance between adapter and 14-50 plug greater, you might dissipate high-resistance heat across more of a surface, but it will still have its issues.

Check your receptacle prongs to ensure they're tight, receptacle wiring is tight and torqued well.

We'll know soon how the adapters have changed things... if there is still a problem, the reports of melting will be replaced by reports of the fuse burning through.

Hi FlasherZ,

Normally I would agree with you that one should not run 48 Amps though a 50A rated receptacle but this receptacle uses the same contacts that are in the 14-60 receptacle. So, I know I will get very low resistance on a good receptacle. I have check my temperature rise with 48A continuous load and after 2 ½ hours, the temperature is only 37 degrees C (99 degrees F). That is only 16 degrees C (29 degrees F) "temperature rise" above ambient (so it is working fine for now). Note 1, the outlet specification says the contacts are rated at 75 degrees C. That being said, that is way too hot for me. If you read my previous post you will see I am planning to give analytical results (contact resistance) on comparison between Tesla’s new versus old adapter (at lease with a sample size of one.) Note 2, the 48A continuous load on a 50A rated receptacle is running a full 10 degrees C cooler than many of the temperatures I measure around the Tesla CE and UL rated Mobile Charger. I do not know how they ever manage to get a CE and UL rating. Good thing I wasn’t on the review committee!

Thank-you for your reply,

Best regards,

Jim
 

PhilBa

Active Member
Apr 20, 2013
1,382
68
Seattle
Personally, I would be conservative on this. You're getting less than 2KW for a gain of around 6 additional M/hr. In my mind that's not worth the risk of dealing with a denied insurance claim.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Are the new adapters "Fused" or breaker style that will automatically reset when cooled? I understood they were breaker style.

Perhaps they are, and that will be a good thing. If they are breakers, you'll see a bunch of people reporting their UMC's died randomly during charging. Point is that we'll still see the failures, it will just manifest in a different way. I hope they've redesigned the contact surface area a bit - stronger clips or something similar to hold better to the UMC head.

- - - Updated - - -

Normally I would agree with you that one should not run 48 Amps though a 50A rated receptacle but this receptacle uses the same contacts that are in the 14-60 receptacle. So, I know I will get very low resistance on a good receptacle. I have check my temperature rise with 48A continuous load and after 2 ½ hours, the temperature is only 37 degrees C (99 degrees F). That is only 16 degrees C (29 degrees F) "temperature rise" above ambient (so it is working fine for now). Note 1, the outlet specification says the contacts are rated at 75 degrees C. That being said, that is way too hot for me. If you read my previous post you will see I am planning to give analytical results (contact resistance) on comparison between Tesla’s new versus old adapter (at lease with a sample size of one.) Note 2, the 48A continuous load on a 50A rated receptacle is running a full 10 degrees C cooler than many of the temperatures I measure around the Tesla CE and UL rated Mobile Charger. I do not know how they ever manage to get a CE and UL rating. Good thing I wasn’t on the review committee!

The 75 deg C termination is for the wiring terminals on the back side of the receptacle, it's a common rating for these receptacles and is primarily used to determine the ampacity of the conductors required to connect to it.

Keep in mind there may be liability or insurance implications with violating the NEC (unless specifically listed for 100% continuous load duty, equipment must be sized at 125% of the continuous load offered).

(Note that my UMC doesn't have a UL stamp on it... I'm not sure it was listed to begin with. :) )
 

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,346
Ottawa, Canada
Automotive equipment is not subject to UL.

The HPWC is listed, probably because electricians and electrical authorities won't touch them otherwise.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Automotive equipment is not subject to UL.

The HPWC is listed, probably because electricians and electrical authorities won't touch them otherwise.

There are UL categories for electrical supply equipment - power supplies, power protection devices, etc.

The question is whether something is subject or not - in the US, officially, you don't *have* to get UL certification, but there are plenty of categories that would fit the device.
 

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top