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Error Code UMC-a001 Inadequate outlet grounding

HELP! Hoping I could some insight on this… so I have a Zencar Level 2 EV charger (NEMA14-50) that I had before and I’m using on my MY with J1772 adapter. Its plugged into a 14-50 to 10-30 pigtail adapter so that I can plug into my dryer outlet. It only gives me 16A 13m/hr but does the trick.

I also have a Tesla NEMA 14-50 adapter and Gen 2 Mobile Connector. I tried plugging into the 14-50to10-30 pigtail adapter and then dryer outlet but T on MC flashes green then red and then I get an Error Code “UMC-a001 Inadequate outlet grounding.” 😧

I’m wondering why does my Zencar Level 2 charger work without issue, but the Tesla Gen 2 MC not? Could it be the 10-30 pigtail adapter? Or maybe my panel is not grounded? Do I need to hire an electrician and change my 10-30 outlet to a 14-50?

I thought about just getting the Tesla 10-30 adapter since it is already grounded, but it only gets 21m/hr as opposed to 29m/hr from the 14-50. I suppose I can keep using the Zencar Level 2 at 16A 13m/hr 😔

Sorry for the long post! Any advice would help. Thank you!
 

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jcanoe

Well-Known Member
Oct 2, 2020
5,738
6,358
Maryland
Any advice would help. Thank you!
Don't do that. The 10-30 does not have a ground connection only a neutral connection. The Tesla Mobile Connector (with 14-50 plug adapter installed) probably detects some current on the ground because it is tied to the neutral via the 10-30 adapter and throws an error. The Zencar is more forgiving of this improper wiring condition. If you want to use the Tesla Gen2 Mobile Connector then get the Tesla 10-30 power plug adapter.
 
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Tam

Well-Known Member
Nov 25, 2012
11,267
10,304
Visalia, CA
...NEMA14-50...
That's the wrong one for your dryer outlet. Your dryer outlet has the writing "30A" on it so you need NEMA 10-30 adapter and not NEMA14-50.

This is what you need:

1118556-10-B_0_2000.jpg


Please pay $45 and be safe rather than using the wrong NEMA14-50.


...Do I need to hire an electrician and change my 10-30 outlet to a 14-50?...
You can but it's not only a change of outlet but also getting the thicker wirings to accommodate the increase in Amperes from 30 to 50A as well as circuit breaker.
 
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Your 14-50 to 10-30 adapter may not be wired properly, indeed, if it's not specifically for EV charging it's hard to guess how they even COULD wire it properly. You should get the Tesla 10-30 adapter instead.

There's also a little talked about issue that can crop up if your 10-30 outet is wired from a subpanel. The 10-30 adapter works by using the neutral pin as if it were a ground. This works because the neutral and ground wires are bonded together at the main panel. However, if your 10-30 is wired from a subpanel, you will have all the other circuits on that panel using that neutral bus and feeding return currents through it. This can leave the netural wire on your 10-30 with a non-zero potential and could conceivably cause problems.
 
Your 14-50 to 10-30 adapter may not be wired properly, indeed, if it's not specifically for EV charging it's hard to guess how they even COULD wire it properly. You should get the Tesla 10-30 adapter instead.

There's also a little talked about issue that can crop up if your 10-30 outet is wired from a subpanel. The 10-30 adapter works by using the neutral pin as if it were a ground. This works because the neutral and ground wires are bonded together at the main panel. However, if your 10-30 is wired from a subpanel, you will have all the other circuits on that panel using that neutral bus and feeding return currents through it. This can leave the netural wire on your 10-30 with a non-zero potential and could conceivably cause problems.
Thanks y’all. I just ordered a 10-30 adapter from Tesla. I guess I’ll just have to settle for 30A 21m/hr but definitely better safe than sorry!
 

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