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Converting NEMA 10-50 to 14-50

benimohit

New Member
Apr 21, 2021
3
6
Kent
Hi All, Getting a 2021 Model Y tomorrow and my garage(new house) has a NEMA 10-50 outlet. I am trying to change the outlet to 14-50.

Info:
1. The wiring is 6AWG from circuit breaker(50) to the outlet and then to a hot tub(Circuit breaker is shared) (see the picture added )
2. The box is a plastic box and I dont see any ground wire coming in to the box.
3. there is an unused 110/120 box right by the side of the NEMA 10-50 and this does have ground wire.

Questions:
1. Is it okay to have the shared circuit breaker in this case ?
2. Do I need to have a ground wire for replacing this NEMA 10-50 to 14-50. (if no, then will there be any risk ) ?
3. Can I get the ground wire connection the unused box and use it !

Please enlighten me! thanks :)
 

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Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
6,863
13,483
Springfield, VA
Hi All, Getting a 2021 Model Y tomorrow and my garage(new house) has a NEMA 10-50 outlet. I am trying to change the outlet to 14-50.

Info:
1. The wiring is 6AWG from circuit breaker(50) to the outlet and then to a hot tub(Circuit breaker is shared) (see the picture added )
2. The box is a plastic box and I dont see any ground wire coming in to the box.
3. there is an unused 110/120 box right by the side of the NEMA 10-50 and this does have ground wire.

Questions:
1. Is it okay to have the shared circuit breaker in this case ?
2. Do I need to have a ground wire for replacing this NEMA 10-50 to 14-50. (if no, then will there be any risk ) ?
3. Can I get the ground wire connection the unused box and use it !

Please enlighten me! thanks :)

Turn off the circuit breaker and have an electrician come and evaluate. No, code won’t allow a car charger and a hot tub to be on the same breaker.

When you buy a NEMA 14-50 receptacle, but a Bryant or a Hubbell instead of the Leviton (poor quality; fire hazard).
 
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Rocky_H

Well-Known Member
Feb 19, 2015
7,845
9,870
Boise, ID
I know people are sounding harsh here, but it's for your own good. Basically every thing that you are asking if you can do...are things you cannot do.

You can't have the two things shared on a breaker and there isn't the right wiring to convert it to a 14-50. This could be switched to a 6-50, and Tesla does sell an adapter plug for that. But again, it can't be on a shared circuit, so you still need to get an electrician to take a look and see what can be done here. And it doesn't necessarily need to be a 50A circuit. If you can get a separate 30A circuit put in, maybe that would be a good idea.
 
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Unfortunately, you can't easily convert a NEMA 10-50 outlet into a NEMA 14-50 outlet, or even a NEMA 6-50 outlet.

As you mention in your initial post, the NEMA 10-50 outlet is hot-hot-neutral and is missing the ground conductor.
NEMA 6-50 is hot-hot-ground, and NEMA 14-50 is hot-hot-neutral-ground. Both of these require a ground conductor.

Any modern EVSE (including the one that comes with the Tesla), will refuse to charge a vehicle if there's no ground detected for added safety. They use a "ground assurance test" (passing a small amount of current through ground) and detect it via the other wires to verify there is an active ground connection. For more info about this, for example, please see the Tesla Gen 3 Wall Connector manual, bottom of page 5 and also page 8.

And to answer the second part of your question, as per most local codes, your ground conductor must be of the same wire gauge as your current-carrying conductors. In your case, that would be a 6 AWG wire back to your main breaker panel. You would not be allowed to simply tap into an existing ground wire in a 120V NEMA 5-15 circuit. Think about it this way: if there is indeed a fault and the 50A circuit needs to dump its current into ground, you wouldn't want it dumping 50A into a 12 AWG or 14 AWG ground wire going back to the main panel. This will likely superheat the wire and melt it, with potential ignition.

Adding a 6 AWG ground wire to an existing circuit inside of a wall is not trivial and will likely cost you just as much money as putting in a new 50A circuit, as the electrician would need to fish the wire through wall and/or cut open the wall to add it in. I'd recommend calling several electricians and gettings quotes on adding a 6 AWG ground wire to your existing 50A circuit vs running a new 50A circuit.
 
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You don't have enough wires for a 14-50. You could rewire/relabel the white wire to convert it to ground and use a 6-50 outlet or wall connector but...
You'd need to be sure that neutral wire isn't connected to anything else.
You'd need to run a different circuit to the hot tub, which likely needs a neutral.
You'd need to resolve all the other issues with this wiring such as the shared breaker, spliced wires, uninsulated neutral, ungrounded hot tub, etc.
You might not even have a neutral here. It's possible that the uninsulated wire is a proper ground from the main panel and it's just being used here as a neutral which can make the entire house wiring somewhat unsafe for people or electronics. You can remove the interior cover plate from your main breaker to see how this circuit is being fed.

If it's really impractical to do those things you could add a new ground then replace this outlet box with a small subpanel that then branches out to the car and hot tub. It's OK to have your existing 50A breaker supplying a subpanel that branches out to multiple 50A breakers, but it needs to be grounded.

Or if you really want to do the bare minimum, you could abandon the hot tub, replace the breaker with 30A GFCI, and replace the 10-50R with a 10-30R. That's legal and fine and yes you can charge the Tesla without a ground using their 10-30 adapter. But this is a lousy way to do it.

Your plastic box is OK, sometimes it's even required to prevent garage fumes from entering the house. But the box isn't big enough for the wires that are in there. Hopefully this house isn't as "new" as you make it sound because whoever did that wiring was clearly not a professional.
 
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jcanoe

Well-Known Member
Oct 2, 2020
5,332
5,823
Maryland
Any modern EVSE (including the one that comes with the Tesla), will refuse to charge a vehicle if there's no ground detected for added safety. They use a "ground assurance test" (passing a small amount of current through ground) and detect it via the other wires to verify there is an active ground connection.
Why does Tesla support a NEMA 10-30 plug adapter for the Gen2 Mobile Connector since there is no ground connection for the 10-30 receptacle?

Gen 2 NEMA Adapters
 
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Why does Tesla support a NEMA 10-30 plug adapter for the Gen2 Mobile Connector since there is no ground connection for the 10-30 receptacle?

Gen 2 NEMA Adapters
I suspect Tesla would like not to have to deal with the 10-30, which was replaced with the (grounded) 14-30 in code nearly 25 years ago, but there are still plenty of houses with these older plugs.

As many people have advised, a competent electrician is needed to sort this out.
 
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Why does Tesla support a NEMA 10-30 plug adapter for the Gen2 Mobile Connector since there is no ground connection for the 10-30 receptacle?

Gen 2 NEMA Adapters
I can't provide definite proof (e.g. teardown), but I do believe they use the neutral wire as ground inside the NEMA 10-30 adapter for the Mobile Connector. Neutral is tied back to ground at the main panel so their "ground assurance test" passes.

I think it's fine if you use an OEM adapter like the NEMA 10-30 one, as then you shift the liability to Tesla. I personally would not use a 3rd party NEMA 10-50 adapter for the Mobile Connector. In case there is a ground fault and something goes wrong, the 3rd party company will deny any liability. Even if the adapter itself is the same construction inside Tesla's own NEMA 10-30 adapter.

However, I would not re-wire the NEMA 10-50 receptacle to a NEMA 6-50 doing a similar thing by yourself. NEMA 6-50's ground prong is assumed to be a non-current carrying wire so you shouldn't connect neutral to it. Of course you could consider permanently re-purposing one of the 6 AWG wires to be a dedicated ground wire to the main panel and convert the outlet to a NEMA 6-50, as Gauss Guzzler suggested, but then your hottub will likely not work due to it requiring 120V circuitry (neutral wire).

You might not even have a neutral here. It's possible that the uninsulated wire is a proper ground from the main panel and it's just being used here as a neutral which can make the entire house wiring somewhat unsafe for people or electronics. You can remove the interior cover plate from your main breaker to see how this circuit is being fed
This is probably the scariest part of the entire situation right now. I would right away test that uninsulated wire to determine whether its neutral or ground. Unfortunately you can't do that at the receptacle, and will need to very carefully open the main panel to take a peek. If you don't feel comfortable with this, ask any electrician.
 
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You'd need a neutral and a ground for a proper subpanel.

So it seems your 10-50 outlet was incorrectly installed using ground as neutral and then someone tapped a hot tub into it again using the ground as a neutral. The safest option would be to replace the outlet with a 6-50 and run a new line to the hot tub.
 
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I wonder if it was a NEMA 6-50 outlet to begin with. Then someone purchased the hotub which needs a NEMA 10-50 outlet. Instead of running a new circuit, they switched the NEMA 6-50 outlet to a NEMA 10-50 outlet by re-purposing the ground wire as a "neutral", even though its actually tied back to the main panel as a ground. (and hence bare wire seen in the wall).

Whoever did this knew that the hot tub doesn't need the neutral wire as it didn't have any built-in 120V circuits. Since this is the case, the bare wire is probably OK since its just acting as a ground. The real danger will be if someone plugs in another NEMA 10-50 device that actually uses the neutral conductor, in which case the "ground" will be energized.

Also, why do you have a hot tub inside your garage? Aren't these usually outside in your back yard on a concrete slab? 😄
 
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MY-Y

Active Member
Mar 4, 2020
1,315
1,568
MD
Another thing to consider. The pic of your box with the outlet hanging out looks way too crowded to me. The NEC also addresses how much you can cram in a box.

I suggest getting an electrician to remove the spliced outlet (hard to believe an electrician did that) and put a blank cover on that box. A new circuit and box are in order for your car.
 
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Why does Tesla support a NEMA 10-30 plug adapter for the Gen2 Mobile Connector since there is no ground connection for the 10-30 receptacle?

Gen 2 NEMA Adapters

Because using the neutral as a ground was allowed under the NEC until 1996 and there are still plenty of old installations out there with grandfathered in NEMA 10 sockets.

OP: If you're asking the kinds of things you're asking, then your only course of action is to hire a competent electrician to sort it out and make sure things are up to code and safe. As pointed out upthread, there appear to be numerous issues with the current situation. An EV draws large amounts of current for sustained periods, unlike a hot tub. This means that even if the circuit worked for your hot tub, any latent issues are much more likely to come up when plugging a car into the circuit. Things like fires and shock hazards. Don't chance it. Get professional assistance. This is beyond your DIY abilities.
 
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