Changing a TT-30 to a 10-30 circuit

[beths11]

@islandbayy , @Cosmacelf , and @linkster and many others who may please jump in. I have found your electrical conversations very educational. I am hoping you can help me with what I believe is a simple question?

I currently have a TT-30 outlet installed,(ground, neutral, hot). As we know it is a 120v/30amp circuit. I believe I can change it to a 10-30 for Tesla charging ONLY as Tesla does not use a neutral (hot, hot, ground). I would replace the single pole 30amp breaker with a 30amp double pole breaker. The black would connect to one leg, the neutral would now become hot and connect to the second leg, and the ground stays grounded. At the plug end I would connect the ground to ground, hot to hot and the old neutral now becomes hot. I have a Tesla 14-30 adapter (new, not recalled one) I would make an adapter which would have a 10-30 plug on one end and a 14-30 receptacle on the other end. The neutral connection on the 14-30 receptacle would have nothing connected to it. I can now plug in my Tesla 14-30 adapter and charge at 24 amps.

Am I thinking correctly??

 

[BerTX]

I'm not an electrician. You should hire one.

The NEMA 10-30 is not configured as you describe. It is an older outlet -- the 3rd pin is not a ground, but a neutral. Maybe a 6-30 would do what you want.

Your logic is good otherwise, assuming your TT-30 has appropriately sized wire and you wrap both ends of the white wire with black tape to indicate its use.

edit -- and clearly label your homemade adapter that it is for Tesla use only

 

[beths11]

I'm not an electrician. You should hire one.

The NEMA 10-30 is not configured as you describe. It is an older outlet -- the 3rd pin is not a ground, but a neutral. Maybe a 6-30 would do what you want.

Your logic is good otherwise, assuming your TT-30 has appropriately sized wire and you wrap both ends of the white wire with black tape to indicate its use.

edit -- and clearly label your homemade adapter that it is for Tesla use only

I understand the 10-30 has three connections, originally intended for Hot, Hot, neutral. Is there something that would prevent me from connecting a ground to the neutral pin since the Tesla does not need the neutral for charging? I would then have a 10-30 wired hot,hot ground(the ground connects to the neutral leg) which would connect, through and adapter to a 14-30 wired hot, hot, ground, no neutral connection (which the Tesla doesn't need).

As they are both 30amp circuits(TT-30 and 10-30) the 10-2 wire size should be a non-issue

 

[BerTX]

I understand the 10-30 has three connections, originally intended for Hot, Hot, neutral. Is there something that would prevent me from connecting a ground to the neutral pin since the Tesla does not need the neutral for charging? I would then have a 10-30 wired hot,hot ground which would connect, through and adapter to a 14-30 wired hot, hot, ground, no neutral connection (which the Tesla doesn't need).

As they are both 30amp circuits(TT-30 and 10-30) the 10-2 wire size should be a non-issue

Code.

If you are going to illegally wire an outlet, change its use, and clearly label it for Tesla use only, then you might as well illegally wire a 14-30 outlet with no neutral and skip all the homemade adapter gradeaux.

I thought your goal was to have a legal outlet, then build an adapter to connect to your 14-30.

 

[beths11]

Code.

If you are going to illegally wire an outlet, change its use, and clearly label it for Tesla use only, then you might as well illegally wire a 14-30 outlet with no neutral and skip all the homemade adapter gradeaux.

I thought your goal was to have a legal outlet, then build an adapter to connect to your 14-30.

No, a legal outlet is not my goal. A safe outlet, clearly labeled, to charge my car efficiently is the goal. The outlet is on a pole, at a RV pad, at a remote part of my property. It will be a TT-30 again when I sell the property.

Thank you. Of course, I can skip the 10-30 plug and just install the 14-30 plug with no neutral.

 

[BerTX]

No, a legal outlet is not my goal. A safe outlet, clearly labeled, to charge my car efficiently is the goal. The outlet is on a pole, at a RV pad, at a remote part of my property. It will be a TT-30 again when I sell the property.

Thank you. Of course, I can skip the 10-30 plug and just install the 14-30 plug with no neutral.

I deny saying you could do that. You must have misunderstood.

 

[KJD]

Am I thinking correctly??

Come on, go buy a NEMA 14-50 outlet and rewire the thing properly. Please do not scrimp on things like this.

FAQ: Home Tesla charging infrastructure Q&A

 

[beths11]

Come on, go buy a NEMA 14-50 outlet and rewire the thing properly. Please do not scrimp on things like this.

FAQ: Home Tesla charging infrastructure Q&A

The problem is the circuit runs underground 3 feet and there is no way to put new wire in. I believe for a 50amp outlet 6 gauge wire is required Wire Gauge Tables
What is currently run is 10 gauge. Sorry if I wasn't clear.

 

[Rocky_H]

I'll weigh in a little. @BerTX is giving good advice. You get to pick your poison, but your original suggestion was picking both poisons, which you don't need to do.

(1) Wire the outlet fully to code, but have to use an adapter. In that case, you should just make it a 6-30, and then build a pigtail to use your Tesla 14-30 adapter.

(2) As you said, if you're not worried about it meeting code, you can just put a 14-30 outlet on it directly with an empty neutral, and you can plug into it directly with the Tesla 14-30 plug and no intermediate adapter needed.

 

[Cosmacelf]

Yes, you are correct, that will work, beths11. Instead of connecting the 10-30 neutral pin to ground, just connect it to neutral and it will thus be code. The Tesla adapter works find like that. Of course, you aren't supposed to wire a new 10-30 these days, but that's the only thing that isn't kosher.

 

[Cosmacelf]

Oh, yeah, since you are going to be using an adapter, wire in a 6-30 instead. 100% code.

 

[Cosmacelf]

The only thing I don't like about wiring in a 14-30 is that you might die of a heart attack and the new owner would get a surprise.

 

[beths11]

Oh, yeah, since you are going to be using an adapter, wire in a 6-30 instead. 100% code.

@Cosmacelf , thanks for the reply, I actually started thinking about this, and got your name from the thread on converting a 110/20a circuit to a 240v/20a cicuit Nema 6-20.. I feel silly not thinking to google nema 6-30 and do the same thing in 30amps...Of course, change the tt-30 to a 6-30 and make a 6-30 to 14-30 pigtail then use my tesla adapter.

Oh, yeah, since you are going to be using an adapter, wire in a 6-30 instead. 100% code.

This is a much better solution

 

[Cosmacelf]

Oh, one more thing, when you convert a neutral to a hot wire, usually the neutral wire is white. It is a good idea to wrap black electrical tape around a segment of the white wire insulation at both ends (in the panel box and in the receptacle) thus signifying the conductor as hot.

 

[BerTX]

Yes, you are correct, that will work, beths11. Instead of connecting the 10-30 neutral pin to ground, just connect it to neutral and it will thus be code. The Tesla adapter works find like that. Of course, you aren't supposed to wire a new 10-30 these days, but that's the only thing that isn't kosher.

I don't think anybody thinks the 10-30 is the way to go and we've moved on, but this solution bothers me. I thought neutral would need to be the same size as the hot wires, and this sounds like cable that would have a smaller ground wire size. It also would be bare wire.

 

[davewill]

Just a final nail in the coffin of the 10-30. In most jurisdictions, new 10-30 installations are not allowed anyway.

 

[ncitro]

Correct me if I am wrong, I am not an electrician either and would recommend you consult one.

That being the case I would just replace the RV TT-30 outlet with a 14-50 outlet and put a double pole breaker 30 amp breaker on it. Connect the black to L1, white to L2 (with tape), and green/bare to ground. There will be no neutral, but my understanding this would not present a safety issue. If someone attempted to plug their RV (or range I guess) into the outlet it would probably pop the 30 amp breaker as it is undersized, and the lack of a neutral would not provide any 120v at the outlet, but that would just prevent things from working, it should not be a safety issue. The 30 amp breaker will do its job of protecting the wire, and you have the added advantage of not needing a adapter. Worst case you could mark it TESLA ONLY and I would think it would be no less safe than what you are proposing and would not require any adapters.

I made a cable up with a surface mounted 14-50 and a piece of three conductor #8 I keep in the car when travelling to my in laws or parents. I keep a few common 30 amp breakers with it and that way can plug it into their breaker panel if I am out there and need to charge. I just dial the car charger down to prevent a problem.

 

[CmdrThor]

Correct me if I am wrong, I am not an electrician either and would recommend you consult one.

That being the case I would just replace the RV TT-30 outlet with a 14-50 outlet and put a double pole breaker 30 amp breaker on it. Connect the black to L1, white to L2 (with tape), and green/bare to ground. There will be no neutral, but my understanding this would not present a safety issue. If someone attempted to plug their RV (or range I guess) into the outlet it would probably pop the 30 amp breaker as it is undersized, and the lack of a neutral would not provide any 120v at the outlet, but that would just prevent things from working, it should not be a safety issue. The 30 amp breaker will do its job of protecting the wire, and you have the added advantage of not needing a adapter. Worst case you could mark it TESLA ONLY and I would think it would be no less safe than what you are proposing and would not require any adapters.

I made a cable up with a surface mounted 14-50 and a piece of three conductor #8 I keep in the car when travelling to my in laws or parents. I keep a few common 30 amp breakers with it and that way can plug it into their breaker panel if I am out there and need to charge. I just dial the car charger down to prevent a problem.

So much is wrong about your solution and your use of the mobile 14-50 outlet. If you really want to wire up a temporary outlet (not a great idea), you should at least use the proper 14-30 outlet and Tesla 14-30 adapter. Manually dialing down the amps is not a safe solution.

And regarding your solution for replacing the TT-30 with a 14-50, not only would you be missing the neutral, which is a safety issue for anything that plugged in other than a Tesla, but users also would be expecting a 50 amp breaker. Yes theoretically the breaker should pop, but you could also start a fire.

 

[davewill]

You can't wire a 14-50 with a three wire circuit, and only a 30a breaker. Instead, use a 6-30r which is appropriate for your circuit. Be sure to mark the white wire with red at both ends so that others will know it is hot. Then make an adapter for 6-30p to 14-30/50 and plug the UMC into that.

 

[beths11]

So much is wrong about your solution and your use of the mobile 14-50 outlet. If you really want to wire up a temporary outlet (not a great idea), you should at least use the proper 14-30 outlet and Tesla 14-30 adapter. Manually dialing down the amps is not a safe solution.

And regarding your solution for replacing the TT-30 with a 14-50, not only would you be missing the neutral, which is a safety issue for anything that plugged in other than a Tesla, but users also would be expecting a 50 amp breaker. Yes theoretically the breaker should pop, but you could also start a fire.

Too bad you didn't read through the thread..