If you check out my pics you will see it fully melted the one terminal and also the adapter. As I said, I replaced both the outlet and the adapter, but with a Leviton outlet rated to 75C. Cord was not damaged at the adapter.
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Scary issue with Nema 14-50 adapter melting
- Thread starter robertmgarrett
- Start date
If you check out my pics you will see it fully melted the one terminal and also the adapter. As I said, I replaced both the outlet and the adapter, but with a Leviton outlet rated to 75C. Cord was not damaged at the adapter.
I'm adding this datapoint to every thread where I see this table -
32 amps - 20k ohms (measured from a Canadian 14-50 adapter)
You won't get that from a Mobile Connecter either Gen1 or Gen2 because a NEMA 14-50 has a 50 amp breaker (although the car will only get 40 amps max with Gen1 and 32 amps max with Gen2).
That is beyond the rating of any Tesla Mobile Connector. You need a Wall Connector to get that level of current delivery.
FlatSix911
Porsche 918 Hybrid
Last night we walked into my garage and saw my NEMA adaptor, cord and outlet on FIRE!! Should I call Tesla and have them come out? I may need to call my homeowners insurance to repair my garage and fire damage. It looks like the prongs overheated and melted. Any help is appreciated.
Attachments
Most likely nothing to do with Tesla. Loose connection somewhere, cant tell for sure from pix, but probably owners outlet-to-UMC-plug was loose. How old was the receptacle? Daily plugging and unplugging? Residential grade receptacle or industrial grade? DIY install or electrician?
Uh huh. This was the old version 1 UMC that DOESN'T have a temperature sensor. Now you see why they added one in the next version.
No, it won’t trip in this case. There was high resistance in the connection which caused heat and it melted. Breaker will NOT trip unless it’s OVER current. If anything it was under current.
The newer mobile connectors do have temp sensors that try to catch this. Picture looks like an old Mobile Connector that should have been ditched.
Note that the column on the left is not the charging amps. It’s the circuit breaker amps. 9600 watts / 240 volts is 40 Amps. Or 80% of the circuit amps.
Highest the cars can charge at these days is 48A on a 60A circuit only available on Wall Connector.
I'd put money on the issue being either a loose wire and/or cheap 14-50 outlet. Leviton 14-50 outlets, for example, are well known to start going high resistance and melting after a few years.
This thread has the full details on which outlets are recommended for daily use:
Master Thread: Definitive 14-50 NEMA Outlet Guide
Comparing the 2 outlets recommended by Tesla with the sub $10 big box model as well as the one I think you should buy 1. Hubbell 9450a 2. Bryant 9450fr 3. Cooper 5754n 4. Leviton 279-S00 The Hubbell and Bryant are far and away the superior product here and since Hubbell owns Bryant and these...
teslamotorsclub.com
beatle
Active Member
Breaker will trip if the breaker itself is hot, generally around 140F. If the receptacle melted, I'd check the breaker. My Leviton 14-50 melted after 2 years of daily use @ 40A on my gen1 UMC. I replaced the receptacle, and a few weeks later my breaker tripped while charging. It was hot - too hot to touch. I removed and retightened the wires going into it which brought the temperatures down to around 80F.
Now even though I have a gen1 UMC, I still only charge at 32A unless I need the extra charging speed.
Breakers usually have two mechanisms of tripping:
- Thermal trip - breaker gets too hot and it trips. Good for detecting long duration, excessive loads.
- Magnetic trip - too much current and it trips. Good for detecting high current under short periods of time.
Dropping charge current a bit is very useful at reducing heat buildup - the amount of power dissipation due to resistance at a location goes up by the square of current. P = I^2 * R (P=Power, I = Current, R = Resistance) So if you drop the current by 50%, the amount of heat loss in the wires will be dropped by 75%. Going from 40 to 32A gets you 80% of the charging power, but power lost in the wires is 64% of the heat loss at 40A.
To drop the power lost in the wire by half from 40A, you would drop the charge current to about 28-29A.
I use a Gen2 Wall Connector and knowing that they are designed to handle up to 80A is nice when the car only charges at up to 48A. Just need to put it on a 100A circuit!
But we were not talking about the breaker getting hot. We were talking about the outlet/plugs melting and that won’t trip the breaker.
An arc fault breaker might have tripped though.
Actually that’s not quite right.
Either breaker can work. The thermal based breakers don’t work well in harsh environments and their trip point will move a lot based on ambient temp.
The magnetic ones are more immune to harsh environments and have much wider operating temp range.
beatle
Active Member
I was correcting your statement that said the "breaker will not trip unless it was over current" which is not true. If your receptacle melted, it's worth checking the breaker as well.
The thermal breakers don't trip due to say the lugs on the breaker being loose. They don't have a thermal sensor (like on the newer Mobile connectors). However they are designed using a thermal scheme that shifts the trip point with ambient temperature. So I still stand by my statement. If a Thermal breaker had a similar fault as this plug/outlet did the results would have been similar. It would have melted down and probably not tripped or tripped far too late. They are not trying to protect against that type of fault. If a fire raises the ambient temp enough to lower the trip point enough to trip on enough load yeah. But that's not meant to be a safety feature, it's a flaw.
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