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Scary issue with Nema 14-50 adapter melting

FalconNinetyD

Active Member
Dec 20, 2010
1,101
11
USA
The locking pin *will* bend if you press the release button on the adapter while sliding the adapter onto on. Make sure you only press the button when removing an adapter.
 

VolkerP

EU Model S P-37
Jul 6, 2011
2,464
27
Germany
I want to endorse the suggestion of thermal sensors in the UMC plug head and adapters. Heat is a sure sign of energy flow going the wrong way.

After all, the split phase U.S. residential power system is to blame here. High power applications require high currents. Even with everything hard wired in the HPWC, there were troubles like blowing 100A fuses and super hot handles.

The European UMC delivers 11kW with 16A current. This is because it is 3 phase power. Still, the UMC adapter snaps on and requires very little force to do so. I usually charge with 12A at home and use 16A only for quick daytime top ups.

My electrician recommended to re-torque the screws in my wiring on a regular basis. This is a scaring thought when I consider the mass adoption of electric vehicles. Someone will charge his EV at home or in a hotel with a degraded electrical infrastructure.
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
After all, the split phase U.S. residential power system is to blame here. High power applications require high currents. Even with everything hard wired in the HPWC, there were troubles like blowing 100A fuses and super hot handles.

The European UMC delivers 11kW with 16A current. This is because it is 3 phase power. Still, the UMC adapter snaps on and requires very little force to do so. I usually charge with 12A at home and use 16A only for quick daytime top ups.

Question: Is residential power typically three-phase in Europe? We have plenty of three-phase here in N. America but it is not typical in residential settings.

My electrician recommended to re-torque the screws in my wiring on a regular basis. This is a scaring thought when I consider the mass adoption of electric vehicles. Someone will charge his EV at home or in a hotel with a degraded electrical infrastructure.

Good advice... and good point!
 

Dave EV

Active Member
Jun 23, 2009
1,675
1,071
San Diego
RE: system design -- I would think there's a way to integrate one or more thermistors into the J1772 signalling circuitry, so that if the temperature on/near either the adapter contacts or the plug blades gets too hot, the car stops charging...
Yep, and not hard to do. Given how many occurrences of melted plugs there have been out there, I'm surprised that EVSE manufacturers are putting these into both the wall plug and car plug.

My Nissan Leaf Forum View topic - Blink / Rav4 Blows Out a Contactor Pin (with gory pics)
 

VolkerP

EU Model S P-37
Jul 6, 2011
2,464
27
Germany
Question: Is residential power typically three-phase in Europe? We have plenty of three-phase here in N. America but it is not typical in residential settings.

Modern residential power systems are 3 phase TN-C-S System 400V 3x63A or 3x50A in Germany, Austria, and Switzerland. France and Italy have 3 phase. Single phase loads in excess of 32A violate electric code. From Widodh I understand that some homes in Netherlands have single phase 35A service, but 3 phase is run to the main panel anyway. Parts of Norway have 3 phase IT network.

Some older homes have single phase with really low amperage e.g. 20A where electricity was intended for lighting only. OTOH a 100A service is really unusual here. 200A and 400A residential services are unheard of. Larger buildings and commercial sites have medium voltage (20kV) 3 phase supply.

'nuff OT.
 

AudubonB

One can NOT induce accuracy with precision!
Mar 24, 2013
8,042
26,479
FlasherZ or others with long experience in the electrical world: could you explain why it is that a standard circuit breaker remains unaffected by the situation apparent here? Why is this not the case of "runaway" current, so to speak?

BTW, our experience and subsequent discussion with one of its employees has the Tesla showroom at Fashion Square in Scottsdale AZ was as follows: its 80A charge site there has its entire length of cable get so hot that the employees wear heat gloves to detach the working end from their cars. Not knowing this, I detached mine barehanded and, while I didn't blister my hand, I will vouch that it was as hot a handle as I could bear. Employee (he was quite junior) told me they are not worried. I would be!
 

fcharland

Member
Jun 18, 2013
70
50
Qc, Canada
FlasherZ or others with long experience in the electrical world: could you explain why it is that a standard circuit breaker remains unaffected by the situation apparent here? Why is this not the case of "runaway" current, so to speak?

BTW, our experience and subsequent discussion with one of its employees has the Tesla showroom at Fashion Square in Scottsdale AZ was as follows: its 80A charge site there has its entire length of cable get so hot that the employees wear heat gloves to detach the working end from their cars. Not knowing this, I detached mine barehanded and, while I didn't blister my hand, I will vouch that it was as hot a handle as I could bear. Employee (he was quite junior) told me they are not worried. I would be!

Because you need less current than the max amperage the breakers is made for to heat this cable. A short of a few amps will heat the cable significantly
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
Because you need less current than the max amperage the breakers is made for to heat this cable. A short of a few amps will heat the cable significantly

Exactly. Think how hot a portable space heater gets without tripping the breaker. Same thing here.
 

miimura

Well-Known Member
Aug 21, 2013
6,104
5,704
Los Altos, CA
FlasherZ or others with long experience in the electrical world: could you explain why it is that a standard circuit breaker remains unaffected by the situation apparent here? Why is this not the case of "runaway" current, so to speak?
The adapter is designed to couple the Mobile Connector to the electrical socket. Cabling should have low resistance and therefore little heating effect at the design current. The problem with the adapter arises when it is not well connected, resulting in high contact resistance and therefore, excessive heating. The total current draw through the breaker is normal, so it does not trip. Tesla should really put a thermistor in the adapter coupler to shut down or reduce the charging current. This thermal protection would protect the MC from damage from poorly connected sockets and loose adapters. The socket can melt too if the screws holding the wire to the back of the socket are not torqued properly. That melting can also damage the MC plug at the same time.
 

AudubonB

One can NOT induce accuracy with precision!
Mar 24, 2013
8,042
26,479
Got it...I think. Let me write this through and let me know if I'm understanding this correctly:

Let's say I have a motor that demands a lot of current - say 1500W at 120V. If I wire it with, say, 22ga cord then in two shakes of a coon's tail that cord's wires are gong to be saying "Holy Crapoly, we're passing on far too many electrons!"....and heat up with all that excitement and, eventually, melting from it.

That meltdown will cause a short circuit...and THAT is what will trip the 20A breaker further upstream.

OK, so back to our 14-50: in this situation we have gotten 2/3s or so down the prior-described road....a too-thin stretch that shows itself to the world as hot-to-handle...but not, at least so far, to go that extra step into real meltdown. And that "too-thin", as I understand you are saying it, is a function of the poor connection, loose screws or SOME OTHER seeming design fault (OP avers he did have the adapters fully engaged).

About right?
 

fcharland

Member
Jun 18, 2013
70
50
Qc, Canada
Got it...I think. Let me write this through and let me know if I'm understanding this correctly:

Let's say I have a motor that demands a lot of current - say 1500W at 120V. If I wire it with, say, 22ga cord then in two shakes of a coon's tail that cord's wires are gong to be saying "Holy Crapoly, we're passing on far too many electrons!"....and heat up with all that excitement and, eventually, melting from it.

That meltdown will cause a short circuit...and THAT is what will trip the 20A breaker further upstream.

OK, so back to our 14-50: in this situation we have gotten 2/3s or so down the prior-described road....a too-thin stretch that shows itself to the world as hot-to-handle...but not, at least so far, to go that extra step into real meltdown. And that "too-thin", as I understand you are saying it, is a function of the poor connection, loose screws or SOME OTHER seeming design fault (OP avers he did have the adapters fully engaged).

About right?

too thin a cable means more resistance. More resistance means more heat. This is how electric heaters work actually.

Same principle with loose connection , insuficiently torqued screws... They make it harder for the electricity to pass in the wire, (resistance) and as a result, that creates heat.

if a breaker is made for 15 A, (about 1500 W) and the (heating) load really is 1500 w, then it will not trip.

though, IF a total short curcuit occurs ( ground and live cable touch each other ) more than 1500 W will try to pass through, and so the breaker would then trip.
 
Last edited:

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
Btw, I can tell from that photo that the adapter is not firmly locked into the UMC , and that is exactly why this melted.

Going back to this comment, I noticed something yesterday: My UMC was replaced a couple of weeks ago due to connectivity with the car issues. Yesterday, I had to charge offsite at 120 volts and changed the adapter. On my "new" UMC, there is about 1/8 to 1/4 inch of "play" between the adapter and the cable with the adapter clicked into place. It wiggles significantly with both the 120 volt and the 14-50 240 volt plugs attached. My previous UMC's plugs were very snug when locked in place.
 

wycolo

Active Member
May 16, 2012
3,068
423
WA & WY
UMC = universal MOBILE adapter.

This is lightweight unit to carry in trunk and use outdoors or in a parking garage. If it indeed has UL/CSA approval I'm guessing it is as a MOBILE device to be used outdoors, etc. It has a minimal reed-switch type Contactor, not a heavy duty 'clunking' type Contactor. Also it has the different adapter heads with surprisingly minimal connectors lacking the spring-loaded snap-together 'feel good' action we have come to expect from modern devices. A fine (undercoat) cat/dog hair could easily get caught in these adapter interfaces and raise the resistance (ohms) causing heat. Best to leave in trunk for occasional use.

Get a real EVSE from the likes of Clipper Creek to permanently mount on garage wall. Get a CLUNKER!!
--
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
\
That meltdown will cause a short circuit...and THAT is what will trip the 20A breaker further upstream.

Correct. In some cases, this is what happens. In other cases, it never reaches this point to trip the circuit breaker, because the wires never get hot enough to melt the wire insulation and create a short-circuit, but outlet parts and plastic cases can melt.

OK, so back to our 14-50: in this situation we have gotten 2/3s or so down the prior-described road....a too-thin stretch that shows itself to the world as hot-to-handle...but not, at least so far, to go that extra step into real meltdown. And that "too-thin", as I understand you are saying it, is a function of the poor connection, loose screws or SOME OTHER seeming design fault (OP avers he did have the adapters fully engaged).

Correct. Doesn't have to be too-thin, can also be dirty connections, so that the electrons only use a portion of the surface area of the pins. That will create a higher resistance, which will create more heat. Heat dissipated is defined by Joule's heating law, P (watts) = (I (amps) ^ 2) * R (ohms). This is why drawing back on the current has a significant effect on reducing heat generation.
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
Going back to this comment, I noticed something yesterday: My UMC was replaced a couple of weeks ago due to connectivity with the car issues. Yesterday, I had to charge offsite at 120 volts and changed the adapter. On my "new" UMC, there is about 1/8 to 1/4 inch of "play" between the adapter and the cable with the adapter clicked into place. It wiggles significantly with both the 120 volt and the 14-50 240 volt plugs attached. My previous UMC's plugs were very snug when locked in place.

Just to clarify, I have no heating issues at all and the UMC is working perfectly despite the "play" in the adapter connection. I didn't mean to suggest I was having a problem. Just providing another data point around the OP's issue.
 

miimura

Well-Known Member
Aug 21, 2013
6,104
5,704
Los Altos, CA
UMC = universal MOBILE adapter.

This is lightweight unit to carry in trunk and use outdoors or in a parking garage. If it indeed has UL/CSA approval I'm guessing it is as a MOBILE device to be used outdoors, etc. It has a minimal reed-switch type Contactor, not a heavy duty 'clunking' type Contactor. Also it has the different adapter heads with surprisingly minimal connectors lacking the spring-loaded snap-together 'feel good' action we have come to expect from modern devices. A fine (undercoat) cat/dog hair could easily get caught in these adapter interfaces and raise the resistance (ohms) causing heat. Best to leave in trunk for occasional use.

Get a real EVSE from the likes of Clipper Creek to permanently mount on garage wall. Get a CLUNKER!!
--
I've always felt that the Tesla Mobile Connector was a little fragile to use as the primary means to charge a Model S on a daily basis. A Leviton EVB40 (the one recommended for the RAV4 EV that also uses a single Tesla on-board charger) would do the same job as the MC and would be much more durable. Of course, Clipper Creek is the gold standard, but at $1,999 for the TS-60, it is significantly more expensive than both the Leviton and a Tesla HPWC.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
How so? The cable and car connector seem to be very similar to Tesla's permanent mount HPWC.

My biggest concern from an engineering perspective is the pin design in the adapters. They seem to be a bit undersized and leave zero room for flex or contact impairments. If the pins were 6 gauge, or perhaps even 8 gauge, they might provide a bit more protection against heat.
 

qwk

P130DL
Dec 19, 2008
3,024
766
My biggest concern from an engineering perspective is the pin design in the adapters. They seem to be a bit undersized and leave zero room for flex or contact impairments. If the pins were 6 gauge, or perhaps even 8 gauge, they might provide a bit more protection against heat.

I'm not surprised that they haven't majorly re-engineered the UMC, as the old adaptors would then not fit the new style pins. Since everything in the UMC is engineered to the bare minimum for 40A charging, it would take an entirely new design to alleviate these problems.
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
My biggest concern from an engineering perspective is the pin design in the adapters. They seem to be a bit undersized and leave zero room for flex or contact impairments. If the pins were 6 gauge, or perhaps even 8 gauge, they might provide a bit more protection against heat.

Fair enough, but the UMC is supposed to be an everyday charging solution and not just a temporary road trip device. My third replacement UMC has a fair bit of "play" with the adapter is clicked in, unlike my first two. So far, no heating or melting issues, but I'll certainly keep an eye out. I even bought one of those pistol grip temperature guns to check things out periodically.
 

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