Correct adapter for a 220 40 amp hook up

[Janus]

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.

A 40A breaker would imply the wiring is also only rated to handle 40A. With EVSEs, the 80% rule applies, so only 32A can be used.

For (only) the modular v2 UMC, it is limited to 32A, so that would be safe. BUT, for many EVSEs (included Tesla's v1 UMC, and Tesla's "Corded Mobile Connector"), when they connect to a NEMA 14-50, they presume that a full 40A is available to them. Pulling 40A constantly for many hours on a wire/breaker only rated for 40A is a fire hazard, and should never be done.

While placing appropriate signage "may" satisfy code requirements, I personally would never do it. As then the requirement is placed on the driver to read the sign, understand it, and configure their car/EVSE appropriately. At least in my experience, relying on a user to change a default setting is a receipt for disaster.

 

[MXLRplus]

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.

You're right about my dumb 48a comment. My bad.

We will disagree about wiring EVSE outlets to a lower specification than the receptacle. You do it your way, I'll do it mine.

 

[qdeathstar]

Please read the electrical code.

I feel like you are missing his point. The code hasn’t caught up to EVs quite yet. Yes, the code says you can put a 50 amp outlet on a 40 amp circuit.

But should you for an EV circuit? I suspect not. I’d bet that code changes in the next few cycles.

what happens to the 40 amp breaker when you put 40 amps through it?

 

[frankvb]

what happens to the 40 amp breaker when you put 40 amps through it?

Most likely it will not trip for hours (or possibly never). Whether it will overheat I have no idea.

 

[qdeathstar]

Most likely it will not trip for hours (or possibly never). Whether it will overheat I have no idea.

It will over heat, as that is how breakers work. The heat up, pull on a bimetallic strip, then break the connection.

 

[arnolddeleon]

A 40A breaker would imply the wiring is also only rated to handle 40A. With EVSEs, the 80% rule applies, so only 32A can be used.

For (only) the modular v2 UMC, it is limited to 32A, so that would be safe. BUT, for many EVSEs (included Tesla's v1 UMC, and Tesla's "Corded Mobile Connector"), when they connect to a NEMA 14-50, they presume that a full 40A is available to them. Pulling 40A constantly for many hours on a wire/breaker only rated for 40A is a fire hazard, and should never be done.

While placing appropriate signage "may" satisfy code requirements, I personally would never do it. As then the requirement is placed on the driver to read the sign, understand it, and configure their car/EVSE appropriately. At least in my experience, relying on a user to change a default setting is a receipt for disaster.

The OP said their licensed electrician did a load calculation and they were limited to 40A. They didn't specify what wire was used so we don't know. If it were my install I would have the electrician use the larger wire so if panel got upgraded in the future or the loads change it would be easy to upgrade.

Signage is not a code thing, it's just to help a future user.

NO ONE is recommending that you pull 40A continuously a 40A circuit.

The funny thing is circuit breakers are there precisely to cover the case that someone either doesn't read the instruction or otherwise does something stupid. It's suppose to trip. Is it ideal, NO! Is it safe YES! Is a recipe for disaster NO! Can it be safer, of course!

Since everyone seems to be concerned about safety let me point where something is more likely to go wrong; the installation of the wires themselves at the receptacle and receptacle itself. Since the OP is using a gen 2 UMC they have some fault detection, the plug has a thermal sensors. The OP didn't indicate if they planned to leave their UMC plugged in or if they plan to unplug it on regular basis. The receptacle that is in the photo looks one that is used for ovens and other fixed appliances. They're usually not designed for a lot plug-in/plug-out cycles. I would caution the OP if they plan to regularly unplug their UMC.

I will close by emphasizing, the OP appears to have safe install. They are *miles* (or should I say kilowatts?) ahead of many users, they used a licensed electrician who knew their stuff.

 

[Janus]

The OP said their licensed electrician did a load calculation and they were limited to 40A. They didn't specify what wire was used so we don't know. If it were my install I would have the electrician use the larger wire so if panel got upgraded in the future or the loads change it would be easy to upgrade.

There is nothing to suggest that was done, and it's dangerous to make such a presumption.

Is it ideal, NO! Is it safe YES! Is a recipe for disaster NO!

That is a blatant misrepresentation. I very much don't appreciate it.

NO ONE is recommending that you pull 40A continuously a 40A circuit.

Once again, you are misrepresenting what I wrote.

 

[Rocky_H]

The OP said their licensed electrician did a load calculation and they were limited to 40A.

There is nothing to suggest that was done, and it's dangerous to make such a presumption.

Bull. Why would you say that? It's stated here in the OP's post:

had an electrician come out and install a 220v, 40 amp outlet (that’s all the juice I had left!)

 

[Janus]

Bull. Why would you say that? It's stated here in the OP's post:

You misunderstand. I am responding to the second half of the quote (see below). There's nothing in the original post to indicate that higher capacity wiring was used.

The OP said their licensed electrician did a load calculation and they were limited to 40A. They didn't specify what wire was used so we don't know. If it were my install I would have the electrician use the larger wire so if panel got upgraded in the future or the loads change it would be easy to upgrade.

 

[Rocky_H]

You misunderstand. I am responding to the second half of the quote (see below). There's nothing in the original post to indicate that higher capacity wiring was used.

Then what you said made no sense at all, or you didn't comprehend what he wrote, because he absolutely did not make such a "dangerous presumption" that you accused him of:

They didn't specify what wire was used so we don't know.

He says right here, that we don't know what size wire was used. No claim is made about that.

If it were my install I would have the electrician use the larger wire so if panel got upgraded in the future or the loads change it would be easy to upgrade.

And then he specifies here what he would prefer to do in his own situation--NOT assuming it's what was done in the OP's case.

 

[Janus]

Then what you said made no sense at all, or you didn't comprehend what he wrote, because he absolutely did not make such a "dangerous presumption" that you accused him of.

You're missing the conversation regarding breaker sizes. There are several posts on this, include the below.

The funny thing is circuit breakers are there precisely to cover the case that someone either doesn't read the instruction or otherwise does something stupid. It's suppose to trip. Is it ideal, NO! Is it safe YES! Is a recipe for disaster NO! Can it be safer, of course!

 

[Rocky_H]

You're missing the conversation regarding breaker sizes. There are several posts on this, include the below.

I'm not missing that. What I don't see is the basis for your accusation:

There is nothing to suggest that was done, and it's dangerous to make such a presumption.

I am responding to the second half of the quote (see below). There's nothing in the original post to indicate that higher capacity wiring was used.

He never claimed that he thought higher capacity wiring was used than was appropriate for the 40A circuit that it is. Yet you claimed that he made that "dangerous presumption".

 

[Janus]

I'm not missing that. What I don't see is the basis for your accusation:


He never claimed that he thought higher capacity wiring was used than was appropriate for the 40A circuit that it is. Yet you claimed that he made that "dangerous presumption".

Wow, I am very done nitpicking a week-old conversation. If you have something productive to add to this thread, then please do so. Otherwise, I've lost interest in playing your silly games.

 

[Janus]

I'm just holding you accountable for a false accusation you made against someone. I consider that a right thing to do--not a game. I'm fine if you want to take it back and drop it, though.

I stand by everything I wrote. Nothing I wrote is false. Though I very much don't appreciate your continuing harassment.

 

[JavTPY]

I looked at the invoice and 3 Gauge 6 wires were used in addition to an 8 gauge ground wire.

I appreciate all the feedback and didn’t mean to incite an argument between members. I think all responses came from a good place so thank you for your feedback!