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Correct adapter for a 220 40 amp hook up
- Thread starter JavTPY
- Start date
You actually need to limit it to 32 amps max. But yes you can limit it. You should have him put a 50 amp breaker in the panel.
MXLRplus
Active Member
The fastest a UMC (the included EVSE that comes with the car) will charge at is 32 amps. If he wired it for 40a you are safe.
However, if you plug a bigger EVSE into that 14-50, the car will default to 40 or 48 amps and cause a hazardous condition.
(That is a 14-50. A licensed electrician should never wire it for 40a since it is a 50 amp receptacle.)
However, if you plug a bigger EVSE into that 14-50, the car will default to 40 or 48 amps and cause a hazardous condition.
(That is a 14-50. A licensed electrician should never wire it for 40a since it is a 50 amp receptacle.)
iamnid
Active Member
You can use up to 80% of whatever breaker he installed; however, since you appear to be using the mobile connector, you'll be limited to 32 amps no matter what. So if the breaker is 40amps, .8 of that is 32 amps anyway. Also, you can set the upper limit of amperage on the car anyway. I think you're good to go though because the mobile connector that comes with the car tops out at 32 amps.
What you will want to do is:
A. Replace your breaker with a 30A breaker and install a NEMA 14-30 outlet.
B. Purchase and install a Tesla wall connector. It can adjust to take 40 amps.
Additionally, unless you have taken that photo sideways, you will need to re-mount that outlet so that it is installed vertically. There is no way that the plug will sustain such sideways force.
MXLRplus
Active Member
@M3BlueGeorgia - If you plug a 40a EVSE into that, the car will request all 40 amps and then you are at risk since you are running the circuit at 100% continuous duty cycle.
M3BlueGeorgia
Active Member
That's valid, but a bit weird.
It is considered normal to use either 40A or 50A with a 14-50 socket.
You won't be pulling more than 32A continuous anyway, because that's the maximum the Mobile Connector can pull, so everything will work correctly with a 40A breaker
MXLRplus
Active Member
What you know about electric car charging is pretty limited apparently.
No, it is NOT acceptable to wire a 14-50 at 40a for Tesla / EVSE duty. It's dangerous. Don't tell people to do it. The Gen 1 UMC pulls 40 amps. Running a EVSE circuit at 100% duty cycle is not clever.
His setup will work and is safe for Gen 2 UMCs. However, if he changes EVSEs in the future all bets are off.
As a corrective note to some posts above: it is completely legal and up to code to put a 50A receptacle on a 40A circuit. This is because no 40A receptacle exists. It would be recommended to put a label at the receptacle stating that it is 40A, so that people are made aware (whether they pay attention and know what to do is an entirely different story).
Indeed since you are using a Gen 2 UMC, you are all set otherwise, since it only allows 32A anyway.
p.s. It's 240V, not 220V.
Indeed since you are using a Gen 2 UMC, you are all set otherwise, since it only allows 32A anyway.
p.s. It's 240V, not 220V.
Looks like it is considered "OK".
Ok to use Nema 14-50 plug with 40amp circuit?
If someone plugs in a device which will draw 40A, the breaker should trip after some time. So its not exactly a death sentence. Besides, he may have put in a wire which is genuinely capable of 50A, in which case, the risk is more about the overall load of the house.
MXLRplus
Active Member
The 40 amp setup should be somehow limited to only accept Gen 2 Tesla UMCs. No 40 amp EVSE's like Teslas Gen1 or JuiceBox 40, etc, should be used at that receptacle.
How are you going to make sure that in the future nobody plugs a Gen1 or other 40 amp EVSE into it?
Like I said, it will work and will be safe for his Gen 2 UMC that came with his particular EV.
It's always best to wire receptacles to accept their rated amps to insure future safety. EVSEs have had a troubled history.
I was unaware that the umc limits the current to 32 amps, i feel like he is good to with his current setup. The breaker should prevent the issue you are worried about. However, there is a possibility that the breaker will just run hot and not trip, which isn’t particularly good.
Also, if the wiring was done with 8awg thhn then the wiring is rated for 50 amps, which is why i think he would be better off with a 50 amp breaker. I think it is thhn because it is installed in flex, but you gotta be sure as NM is only rated for 40 amps.
I think the NEC is going to undergo some changes regarding the rules because your scenario isn’t wrong....
Thank you for the input. I have a few comments and answers to some of the issues that came up
1. Yes the picture was sideways,
2. It sounds like I am ok with the current set up due to the vehicle that I am getting and the charger that comes with it- will keep this in mind.
3 I won’t ever get another type of EV or an older Tesla/charger and will pull the wiring if I sell the house, just to be safe.
Thank you for all the replies!
1. Yes the picture was sideways,
2. It sounds like I am ok with the current set up due to the vehicle that I am getting and the charger that comes with it- will keep this in mind.
3 I won’t ever get another type of EV or an older Tesla/charger and will pull the wiring if I sell the house, just to be safe.
Thank you for all the replies!
It really depends on the breaker you have. What size of breaker was installed for this plug?
MXLRplus
Active Member
Please learn about electric cars and how to refuel them. Just because the law says you CAN do something doesn't mean you SHOULD do something.
Ok, I'll play a little more. You made what I believe is a factually incorrect statement: "That is a 14-50. A licensed electrician should never wire it for 40a since it is a 50 amp receptacle"
I suggested that you read the electrical code. You also stated that a car could pull 48A from a 14-50 outlet. That's also incorrect, unless the operator/installer incorrectly configured their EVSE or commanded their vehicle to exceed the pilot signal. I'm not aware of any properly built plug-in EVSE that will advertise a charging current above 40A when plugged into a 14-50 outlet. You do know about J1772 pilot signals right?
I apologize for being a little terse but I think you know *nothing* about what I know.
Now apropos to the original question. The configuration as installed the licensed electrician is safe. I agree with the recommendations that outlet be labeled. I wouldn't bother pulling the outlet if I moved. Odds are the outlet as is will be useful to the future occupant.
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