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Tesla Wall Connector: Hard wiring Vs NEMA 14-50

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I’ve my Tesla Model Y delivery date finalized and now I’m exploring the options for charging. I ordered Tesla Wall Connector and thinking to connect to NEMA 14-50 for flexibility. Appreciate if I get response to following questions.

  • I understand that 60 Amp hard-wired wall connector works best, however, what are the cons of installing NEMA 14-50 with 50 Amp wire? Appreciate if someone let me know how slow the charging will be if Tesla Wall Connector is connected to NEMA 14-50 (50 Amp)
  • Assuming I opt for NEMA 14-50, would it affect the installation rebate or any State/Federal(?) rebate? One electrician said if I do not opt for hard wiring, the rebate can be denied. Is it true?
  • Any EV rebates available to apply for state of MD (Montgomery County)?
TIA
 
That’s a 14-50 so if you get the mobile connector it will be plug and play and work just fine.

But that also looks like just the generic cheap 14-50 receptacle you get from the typical home improvement store and not an industrial grade one. It can still be fine as long as you don’t frequently plug and unplug it.

If the circuit is built for 50 amps, you can potentially convert the outlet to use with a hardwired wall connector instead and be able to charge at 40 amps instead of the mobile connector limit of 32 amps.
 
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That’s a 14-50 so if you get the mobile connector it will be plug and play and work just fine.

But that also looks like just the generic cheap 14-50 receptacle you get from the typical home improvement store and not an industrial grade one. It can still be fine as long as you don’t frequently plug and unplug it.

If the circuit is built for 50 amps, you can potentially convert the outlet to use with a hardwired wall connector instead and be able to charge at 40 amps instead of the mobile connector limit of 32 amps.

Is there an easy way to check if the circuit is built for 50 amps before I get an electrician to come over?
 
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A builder grade 14-50 receptacle is fine for an electric range but not optimal for charging an EV. @E90alex suggested having an electrician remove the 14-50 receptacle and mount the Tesla Wall Connector in its place. The Wall Connector is designed to be hard wired (so no plug and receptacle.) The Wall Connector can charge 25% faster than the Mobile Connector on the same 50 amp rated circuit. The Wall Connector has a longer 24 foot charging cord (Mobile Connector cord is 18 feet.) There are other benefits to the Wall Connector.
 
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No it’s a 30 amp breaker…….was done by licensed electrician here in Las Vegas NV
30 amp breaker on a 14-50 outlet definitely is against code and most likely means the wiring can only handle 30 amps. It should not be used with the 14-50 adapter because it will try to pull 32 amps and overload the circuit and trip the breaker, or worse cause a fire. You can temporarily reduce the charge amperage in the car to 24 amps or lower, but that should not be relied on as a permanent solution.

Your options are (from least to most expensive):
1) replace the receptacle with a 14-30 receptacle and purchase the 14-30 adapter for the mobile connector from Tesla. This will let you charge at 24 amps
2) rewire the circuit for 50 amps with a 14-50 receptacle and use a 14-50 adapter with the mobile connector
3) rewire the circuit for 60 amps (or 50 amps if your panel/home can’t handle 60 amps dedicated for charging) and hardwire a wall connector
 
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No it’s a 30 amp breaker…….was done by licensed electrician here in Las Vegas NV
Ahem. I'm adding my voice to the crowd.

If one looks at available 240 VAC sockets, there are 15A sockets; there are 20A sockets; there are 30A sockets; and there are 50A sockets.

There's a rule: A given amperage socket is supposed to be used with wire that's good for that amperage and a breaker that's also good for that amperage. It's a triple: Socket, wire, breaker. There's more.

Tricky bit #1: If one has a 40A load, you'll note that there's not a 40A socket. So, the NESIC says that one can use a NEMA 14-50 with a 40A breaker and 40A wire. That gets labeled at the socket end that one is doing that.

Otherwise, the triple (socket:wire:breaker) business rules.

Tricky bit #2: If one is running a continuous heavy load, then the maximum current of that load is no more than 80% of the (socket:wire:breaker) ratings. So, you got a 115 VAC socket with a 15A breaker on it (NEMA5-15)? Then, max steady load is 12A. Period. If you have a 20A socket, wire, and breaker (NEMA5-20), then max load is 16A.

And, if you've got a hard-wired Tesla Wall Connector, and you want to charge at 48A, then (48/0.8) = 60, so you need a 60A breaker, you configure the Wall Connector for a 60A circuit, and you use wire that can handle at least 60A.

Next: I don't care if that electrician says that he's licensed: If he put a NEMA14-50 on a 30A breaker, then the electrical inspector from your political unit would likely make him lose his license. Let's get real.

The problem is heat. Wire has resistance per unit length. The power dissipation in a wire is the current*current*resistance_of_the_wire.

There's actually a very simple formula that says how hot something gets when it has power dissipated in it. It's (T(wire) = Pd * Theta(Wire-to-ambient) + T Ambient). Theta is calculated by setting up, say, a particular grade of wire; surrounded by the wire insulation; with the cable (ROMEX, whatever) embedded in a wall with, say, exterior insulation, wood, and all that jazz. Stick a thermocouple on the wire, put 10A of current in it, and see how hot the wire gets. People with PhDs who work for the UL and/or the people who publish the NESIC code do this, come up with values for Theta, and then Tables Get Published.

Why do they do this? Because it's very possible to get the wire hot enough to make the insulation of the wire scorch. Once it's nice and brown, more current starts flowing through the insulation. And the insulation either catches on fire or catches the house on fire.

THIS IS NOT A DRILL. HOUSES CAN AND DO BURN DOWN TO THE GROUND BECAUSE OF IDIOTIC WIRING PRACTICES THAT DO NOT FOLLOW CODE.

You may have noticed: Copper wire costs money. An electrician who saves cash by putting in undersized wire might get away with it for a while.. until the first house burns down and the mob with pitchforks and torches comes to throw the sucker in jail.

Now, you've been warned. You might think that you can live with the risk; besides, this idiot told you it was OK, right? How do you feel about your loved ones being woken up at 2 a.m. by a blast of heat and smoke?

Don't screw with this. Find a real electrician, clearly not this guy. And, if you'd like to save some poor schmuck who's the victim of this idiot, I'd strongly suggest giving your local electrical building inspector a call.
 
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The first thing to find out is what kind of wire was used on that circuit. You need to know what amperage the existing wiring can support. Once we know that, then we will know whether you are actually stuck at 30a or can go higher. How did you determine that this circuit had a 30a breaker? Is it possible that the labeling is wrong and it is actually a 40a or 50a breaker?

Here's the deal. If you really are limited to 30a, then you need that outlet replaced with a 14-30 to use the mobile connector. If the circuit is actually 40a or 50a, then you can use the mobile connector with the existing 14-50.

Is this new construction? If so, you may be able to file a warranty claim to fix the mismatched outlet and breaker. Depending on what they advertised when they said it was wired for EV charging, you may even be able to make them rewire it for at least 50a.
 
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A builder grade 14-50 receptacle is fine for an electric range but not optimal for charging an EV. @E90alex suggested having an electrician remove the 14-50 receptacle and mount the Tesla Wall Connector in its place. The Wall Connector is designed to be hard wired (so no plug and receptacle.) The Wall Connector can charge 25% faster than the Mobile Connector on the same 50 amp rated circuit. The Wall Connector has a longer 24 foot charging cord (Mobile Connector cord is 18 feet.) There are other benefits to the Wall Connector.
This ^

Builders are just checking a box the county requires them to check. They are doing it for as little cost as possible. I like the advice above for a permanent home charging setup in your new home.
 
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Thanks for the responses……..will investigate this further…..it was an added amenity advertised with the house and moving from a condo it made me further interested in a Tesla which I have an MYLR on order .
No it’s a 30 amp breaker…….was done by licensed electrician here in Las Vegas NV
Well, yes, you do have a charging circuit, but that's messed up, and should be corrected.

30 amp breaker on a 14-50 outlet definitely is against code
It sounds crazy, but isn't actually a violation. The forbidding only goes the other way. You are not allowed to have the breaker be higher rated than the outlet. The breaker can be lower, and even can be that way, but it's amateurish and dumb to not match them at the 30A level.

The first thing to find out is what kind of wire was used on that circuit. You need to know what amperage the existing wiring can support. Once we know that, then we will know whether you are actually stuck at 30a or can go higher.
This is the important thing. You need to get a look at what type of wire is in there to know what choices you have. A 30A circuit would be fine for charging, but should be switched to either just wire a wall connector onto it instead of the outlet or switch that to a 30A outlet type. Those are easy and cheaper fixes than ripping out and changing the wire that is already in the wall trying to make it a higher power circuit.
 
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I just bought a new home and this outlet is in my garage……when I bought the home they said it was wired for EV
I ordered a MY Tesla a week ago. What do I need for charging? The wall connector or the Mobile connector?
Thanks …..a total noobie here
A lot of good advice has been given to you regarding your question, but since this appears to be installed a little less than optimally, I'm curious if the person who installed this circuit used a GFCI breaker for this circuit?

Since you are a newbie you should know that any receptacle in a garage needs to be fed from a GFCI breaker, which will have a test button on it.

Have you ordered a Mobile Connector? Tesla has not provided those with new cars for cars ordered since about April of 2022. When you order the Mobile Connector, you may also need to order an appropriate power cable if you need to connect it to a receptacle that is not a NEMA 5-15 or 14-50.

And if you plug a 14-50 plug into a 14-50 receptacle, let me reiterate that it will charge at 32 amps and overload the 30 amp circuit you now have, so you are going to have to do something to get ready for charging.

But if you have not already ordered Mobile Connector, or can return it, I suggest you go with a Tesla Wall Connector, especially if the 14-50 is not being fed with a GFCI breaker. Since the WC is hard wired (not plugged in to a receptacle) it does not need to be on a circuit protected with an expensive GFCI circuit breaker. It is a little more expensive than the Mobile Connector, but not by much, and if you have to install a GFCI breaker for the 14-50 might even be less expensive.

The Wall Connector is a 240 volt device, which can be configured for 15, 20, 30, 40, 50, or 60 amp breakers/circuits, but the actual charging current will be 80% of these ratings. Depending on your driving requirements, you may not need a circuit that is more than 30 amps.

It is possible that the person who installed this circuit installed wire that is of a different capacity than the circuit breaker. You need to determine the size of the wire that was installed for this circuit. Here is a list of breakers and wire sizes: for copper wire:

Breaker size, Romex, THWN/MC

15, #14, #14
20, #12, #12
30, #10, #10
40, #8, #8
50, #6, #8
60, #4, #6

The above is not the exact ampacity rating of these wires, rather it is the size wire needed for Tesla Wall Connector, depending on the breaker size at which the WC is configured. THWN wire needs to be in conduit. MC is Metal Clad cable which has THWN wires in a flexible metal covering.

I suggest you determine the wire size and type for this circuit, install the correct circuit breaker if needed (GFCI for receptacle, standard for WC), and install the correct NEMA receptacle for the rating of the circuit (wire size and type, breaker) or better yet install a Tesla Wall Connector and configure it for the rating of the circuit.

If all of this is too much for you, then you need to contact an electrician who is up to date on the requirements for EVs. Or with the above information you can have a more educated discussion with the builder who built your house, but as Rocky_H says, since it is OK to install a NEMA 14-50 receptacle on a 30 amp circuit, you might have an uphill battle trying to deal with the builder.

Hope this has been helpful.
 
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It sounds crazy, but isn't actually a violation. The forbidding only goes the other way. You are not allowed to have the breaker be higher rated than the outlet. The breaker can be lower, and even can be that way, but it's amateurish and dumb to not match them at the 30A level.
Here is a discussion of how this works and why this is allowed:

For a single receptacle on a branch circuit NEC 2017 210.21(B)(1) says:

"a single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit."

A 50 amp receptacle is, indeed, not less than the rating of @dguitarnut's 30 amp circuit so the installation at his new house complies with 210.21(B)(1)!

The case of the Tesla Mobile Connector is not completely compatible with NEMA's design because the MC will set the car's charging rate (up to 32 amps) depending on the type of NEMA adapter that is used with the MC. It appears the Tesla engineers who designed the MC did not take into account the possibility of a NEMA 14-50 receptacle being fed with a 30 amp circuit, and were not aware that 210.21(B)(1) might allow this to happen.

I suspect the builder or electrician that installed this circuit is aware that a lot of EVSE's are equipped with a NEMA 14-50 plug, and can be configured for whatever amp draw the circuit is capable of, and in a effort to "check the box" of a potential home buyer's requirement for EV charging capability they installed what they thought would work (and comply with the NEC) at the lowest possible price. They might think they have done a good job and be surprised to see someone is not happy with what they have done and I think @dguitarnut could have a hard time arguing with the builder or electrician that they should consider this a warranty claim because the circuit does not violate the NEC, but of course the builder or electrician might want to install a NEMA 14-30 receptacle out of the goodness of their hearts since it is such a cheap way to fix the problem. In any case, the minimal amount of effort to make this circuit to work properly with the MC is a very inexpensive thing to do: Just change the 14-50 to a 14-30 will do that.

I doubt the builder or electrician is obligated to do even that, but if they did it would resolve the problem.

I still say the best resolution of this would be to install a hard wired Tesla Wall Connector properly configured for the ampacity of whatever circuit is already installed. Even if it is a 30 amp circuit, charging at 80% (24 amps) it will very likely be satisfactory unless you run your car down to less than 20% every day or can't charge it overnight.

(Another way to fix this as a DIY project without involving the builder or electrician would be to purchase a non-Tesla EVSE that is equipped with a NEMA 14-50 plug and configure it for 24 amp charging. You would then have to use the J1772 to Tesla adapter that comes with the Model Y unless you can find a non-Tesla EVSE with a Tesla connector on the end of the cable. The You Tube channel "State of Charge" has lots of videos on just about every EVSE made. I suspect with Ford's upcoming decision to use the Tesla connector starting in 2025 there will be lots of EVSE's built with Tesla connectors, but I am unaware of any that are made today. Anyone know of any?)

A little on why this is allowed:

Sometimes it is necessary to install a receptacle that has a higher rating than the circuit because certain size receptacles are not made. For example, a NEMA 14-50 is often installed on a 40 amp circuit. Usually this is done for a range, which is semi-permanently plugged in, usually until the kitchen is renovated, and the receptacle is behind the range. Most people go through life and never realize this receptacle is even there. Note that for houses built in the olden days the receptacle will probably be a NEMA 10-50

Just for a complete understanding, and to underscore the difference, for two or more receptacles on a branch circuit NEC 2017 210.21(B)(3) says:

210.21(B)(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or, where rated higher than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.

Screen Shot 2023-06-02 at 11.37.55 AM.png


Note in the case of when there are 2 or more receptacles on a branch circuit, it would not be permissible to install a NEMA 14-50 amp receptacle on a 30 amp circuit.

But a 15 amp receptacle can be installed on a 20 amp circuit. The reason this is allowed is because the feed through part of a 5-15 receptacle that feeds a downstream receptacle is designed to carry 20 amps, and the cords used on appliances that are equipped with a NEMA 5-15 plug are not used on appliances which draw more than 12 amps or 1500 watts (at 125 volts), and the rare 120 volt appliance that draws more than 12 amps is equipped with a NEMA 5-20 plug (the plug with one blade turned 90 degrees from normal). Tesla sells a NEMA adapter with a 5-20 plug for 16 amp 120 volt charging for use with the Tesla Mobile Connector.

A lot of thought has gone into the NEMA standards for receptacles and plugs!

I hope this is interesting, and I am sure I will be informed I have made any mistakes.
 
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Here is a discussion of how this works and why this is allowed:

For a single receptacle on a branch circuit NEC 2017 210.21(B)(1) says:

"a single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit."

A 50 amp receptacle is, indeed, not less than the rating of @dguitarnut's 30 amp circuit so the installation at his new house complies with 210.21(B)(1)!

The case of the Tesla Mobile Connector is not completely compatible with NEMA's design because the MC will set the car's charging rate (up to 32 amps) depending on the type of NEMA adapter that is used with the MC. It appears the Tesla engineers who designed the MC did not take into account the possibility of a NEMA 14-50 receptacle being fed with a 30 amp circuit, and were not aware that 210.21(B)(1) might allow this to happen.

I suspect the builder or electrician that installed this circuit is aware that a lot of EVSE's are equipped with a NEMA 14-50 plug, and can be configured for whatever amp draw the circuit is capable of, and in a effort to "check the box" of a potential home buyer's requirement for EV charging capability they installed what they thought would work (and comply with the NEC) at the lowest possible price. They might think they have done a good job and be surprised to see someone is not happy with what they have done and I think @dguitarnut could have a hard time arguing with the builder or electrician that they should consider this a warranty claim because the circuit does not violate the NEC, but of course the builder or electrician might want to install a NEMA 14-30 receptacle out of the goodness of their hearts since it is such a cheap way to fix the problem. In any case, the minimal amount of effort to make this circuit to work properly with the MC is a very inexpensive thing to do: Just change the 14-50 to a 14-30 will do that.

I doubt the builder or electrician is obligated to do even that, but if they did it would resolve the problem.

I still say the best resolution of this would be to install a hard wired Tesla Wall Connector properly configured for the ampacity of whatever circuit is already installed. Even if it is a 30 amp circuit, charging at 80% (24 amps) it will very likely be satisfactory unless you run your car down to less than 20% every day or can't charge it overnight.

(Another way to fix this as a DIY project without involving the builder or electrician would be to purchase a non-Tesla EVSE that is equipped with a NEMA 14-50 plug and configure it for 24 amp charging. You would then have to use the J1772 to Tesla adapter that comes with the Model Y unless you can find a non-Tesla EVSE with a Tesla connector on the end of the cable. The You Tube channel "State of Charge" has lots of videos on just about every EVSE made. I suspect with Ford's upcoming decision to use the Tesla connector starting in 2025 there will be lots of EVSE's built with Tesla connectors, but I am unaware of any that are made today. Anyone know of any?)

A little on why this is allowed:

Sometimes it is necessary to install a receptacle that has a higher rating than the circuit because certain size receptacles are not made. For example, a NEMA 14-50 is often installed on a 40 amp circuit. Usually this is done for a range, which is semi-permanently plugged in, usually until the kitchen is renovated, and the receptacle is behind the range. Most people go through life and never realize this receptacle is even there. Note that for houses built in the olden days the receptacle will probably be a NEMA 10-50

Just for a complete understanding, and to underscore the difference, for two or more receptacles on a branch circuit NEC 2017 210.21(B)(3) says:

210.21(B)(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or, where rated higher than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.

View attachment 943290

Note in the case of when there are 2 or more receptacles on a branch circuit, it would not be permissible to install a NEMA 14-50 amp receptacle on a 30 amp circuit.

But a 15 amp receptacle can be installed on a 20 amp circuit. The reason this is allowed is because the feed through part of a 5-15 receptacle that feeds a downstream receptacle is designed to carry 20 amps, and the cords used on appliances that are equipped with a NEMA 5-15 plug are not used on appliances which draw more than 12 amps or 1500 watts (at 125 volts), and the rare 120 volt appliance that draws more than 12 amps is equipped with a NEMA 5-20 plug (the plug with one blade turned 90 degrees from normal). Tesla sells a NEMA adapter with a 5-20 plug for 16 amp 120 volt charging for use with the Tesla Mobile Connector.

A lot of thought has gone into the NEMA standards for receptacles and plugs!

I hope this is interesting, and I am sure I will be informed I have made any mistakes.
The problem with that logic is that an outlet for 30A exists: 14-30. The exception really only was created for 40A circuits in which a 14-50 is acceptable (as per your table) due to no 14-40 existing. Of course by the wording of the code, you can argue with inspector it's a single receptacle and thus the table does not apply, but in practical terms, many EVSEs can easily overload the circuit because they expect a 14-50 to support 40A continuous.

And if you overload the circuit, you violate 210.23:
In no case shall the load exceed the branch-circuit ampere rating...

As it relates to the poster, he should check what actual wiring is used. It's possible only the breaker was undersized.
 
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The problem with that logic is that an outlet for 30A exists: 14-30. The exception really only was created for 40A circuits in which a 14-50 is acceptable (as per your table) due to no 14-40 existing. Of course by the wording of the code, you can argue with inspector it's a single receptacle and thus the table does not apply, but in practical terms, many EVSEs can easily overload the circuit because they expect a 14-50 to support 40A continuous.

And if you overload the circuit, you violate 210.23:
In no case shall the load exceed the branch-circuit ampere rating...

As it relates to the poster, he should check what actual wiring is used. It's possible only the breaker was undersized.
I agree, and I would not want this in my garage. I was just trying to help the noobie by giving him as much info as I could think of. Hopefully he will check out the wire size that was installed and have the correct size and type of breaker for the wire and a receptacle that matches the capacity of the circuit, or better yet a hard wired Tesla Wall Connector configured for the capacity of the breaker and circuit.

The way 210.21(B)(1) is written, you could have a single 14-50 receptacle on a 15 amp 250 volt circuit. Of course, that would be ridiculous to the extreme. But there are use cases for which an oversized receptacle is appropriate when it is the only receptacle on a circuit, as long as the intended load to be connected to it does not exceed the rating of the circuit. It depends on the utilization equipment which is why I think the NEC allows this, and an EVSE that comes with a 14-50 but can be set for 24 amps is probably one of those cases where a 14-50 could be installed on a 30 amp circuit. Seems to me this would not be much different than a Tesla Wall Connector set for 30 amp breaker / 24 amp charging on a 30 amp circuit? Please label that 14-50 "30 Amp Circuit".

The title of 210.23 is "Permissible Loads, Multiple-Outlet Branch Circuits", so it does not apply for circuits with a single receptacle.

Final thought: Given all the different configurations used for EV charging (i.e. the problem of a Gen 1 Mobile Connector (40 amps) plugged into a 14-50 receptacle wired with a 40 amp circuit), it is my belief that for an EV the only safe setup is for the breaker size, wire, and receptacle all have the same capacity, and the breaker type matching the requirement of the circuit (GFCI breaker or receptacle, standard breaker for hard wired EVSE). I hope a future edition of the NEC addresses this by requiring the that size of the receptacle must match the size of the circuit (breaker and wire), an including not allowing a 40 amp circuit to have a 14-50 receptacle like is common for ranges. That is the only way I can think of to ensure long term safety since over the years the owner of a property and the types of EVSE therein are likely to change. Over the years the "intended load" for EV receptacles is much more likely to change than a range, oven, or dryer receptacle.

Of course, the AHJ has the final say.
 
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So if it is a 14-30 circuit is it safe to use with my Tesla mobile connector……can I dial down on the charging software to provide at 30 amp charging or perhaps lower? I realize charging times will increase….
I take delivery of MYLR tomorrow and moving into the new home in 30 days
No need to "dial" anything down. The 14-30 adapter from Tesla will automatically take care of that for you. Charging will be at 24a on a 30a circuit.
 
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