Changing a TT-30 to a 10-30 circuit

[bonnie]

Maybe I missed it, but why not use an adapter? I'm currently renting a house while building & found an outside TT30 here at the rental house. I bought this adapter and have been charging with zero problems (outside of the slow rate, that is).

 

[beths11]

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 6-50p to 14-30/50 and plug the UMC into that.

Thank you others up thread mentioned this as well...I appreciate your confirmation of the solution

 

[beths11]

Maybe I missed it, but why not use an adapter? I'm currently renting a house while building & found an outside TT30 here at the rental house. I bought this adapter and have been charging with zero problems (outside of the slow rate, that is).

View attachment 216889

Yes, I have that adapter. Reading a thread on the forum regarding changing a 5-20(120v/20amp) to a 6-20(240/20amp) and the improvement to the charging of the car, got me thinking about improving my 30A/110V. It is much more efficient, electrically speaking, to charge using 240V rather than 110V because of the energy that the car's charging overhead uses. I over thought it. I just need to change the tt 30r (120v/30amp) to a 6-30 (240v/30amp) and make an adapter from 6-30 to my Tesla 30A adapater. I will not have to mess with setting the amp setting in the car for charging as the adapter will take care of it.

Many thoughtful replies, thanks to all.

 

[bonnie]

Yes, I have that adapter. Reading a thread on the forum regarding changing a 5-20(120v/20amp) to a 6-20(240/20amp) and the improvement to the charging of the car, got me thinking about improving my 30A/110V. It is much more efficient, electrically speaking, to charge using 240V rather than 110V because of the energy that the car's charging overhead uses. I over thought it. I just need to change the tt 30r (120v/30amp) to a 6-30 (240v/30amp) and make an adapter from 6-30 to my Tesla 30A adapater. I will not have to mess with setting the amp setting in the car for charging as the adapter will take care of it.

Many thoughtful replies, thanks to all.

Ah got it. Totally missed that.

I'm not here long enough to do anything more than use the adapter. There is a CHAdeMO a few miles away that I can always use to bump things up, if necessary. And a supercharger about 15 miles away in a real emergency. But I can put about 100 miles or more on the X between the evening and the next morning using the TT30, and that suffices in the majority of cases.

For now. The new house will have 400amp service with my 70amp Roadster HPC and a 80 amp HPWC for the X ... and a 14-50 for non-Tesla visitors.

 

[CmdrThor]

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

My response was to ncitro's suggestions, not to your plans. Your plans were definitely better than his. What you proposed was reasonably safe although not to code (but you stated you knew that so fine). Putting a 14-50 outlet on your circuit would definitely be an unsafe bad idea though.

 

[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.

My apologies, thank you for clarifying your reply. I jumped in instead of paying more attention to whom your reply was directed.

 

[ncitro]

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.

Sorry for the long delay, I thought I was subscribed and I was not.

I appreciate your insight, and freely admit I am learning as I go, but I am unsure how it could start a fire. The circuit breakers job is to protect the wiring, as long as the breaker is sized appropriately for the wire, how could a fire begin? If anything tried to pull more current through the cable than the 30 amps it is rated to (such as if someone were to plug a mobile connector into the outlet and not dial it down) it should trip the breaker long before a fire could happen as that is its purpose. If any device tried to pull 120V off of the neutral wire (which is not connected), it would not be able to get it and would (I assume) not work correctly, but should not cause a fire. Note I did not tie the neutral to the ground to supply the outlet to 120V as that would obviously be unsafe.

Regardless to prevent an issue I will switch my cord to a #6, 4 conductor cord and a 50 Amp breaker to be safe, but I am curious to explore this more just to learn.

 

[CmdrThor]

Sorry for the long delay, I thought I was subscribed and I was not.

I appreciate your insight, and freely admit I am learning as I go, but I am unsure how it could start a fire. The circuit breakers job is to protect the wiring, as long as the breaker is sized appropriately for the wire, how could a fire begin? If anything tried to pull more current through the cable than the 30 amps it is rated to (such as if someone were to plug a mobile connector into the outlet and not dial it down) it should trip the breaker long before a fire could happen as that is its purpose. If any device tried to pull 120V off of the neutral wire (which is not connected), it would not be able to get it and would (I assume) not work correctly, but should not cause a fire. Note I did not tie the neutral to the ground to supply the outlet to 120V as that would obviously be unsafe.

Regardless to prevent an issue I will switch my cord to a #6, 4 conductor cord and a 50 Amp breaker to be safe, but I am curious to explore this more just to learn.

It *should* trip the breaker, but breakers are not 100% reliable. Regarding a device trying to pull 120V when the neutral is missing, take a look at this thread from an RV forum about plugging into an outlet with an open neutral.

30 amp "open neutral" - Airstream Forums

 

[ncitro]

Interesting read. Had not occurred to me that internal to the RV (or house in the other example) the neutrals of two 110v devices on different sides of the bus would supply them with 240v. That would be a mess for sure and definitely a safety hazard. I appreciate the knowledge and correction.

 

[davewill]

... If any device tried to pull 120V off of the neutral wire (which is not connected), it would not be able to get it and would (I assume) not work correctly, but should not cause a fire. Note I did not tie the neutral to the ground to supply the outlet to 120V as that would obviously be unsafe. ...

My understanding is that without the neutral connected, the 120v can end up finding another path to ground through the appliance with bad consequences.

 

[beths11]

Interesting read. Had not occurred to me that internal to the RV (or house in the other example) the neutrals of two 110v devices on different sides of the bus would supply them with 240v. That would be a mess for sure and definitely a safety hazard. I appreciate the knowledge and correction.

Which is exactly why an RV should not be plugged in. As long as the car is the only device plugged into the outlet, and it does not use a neutral there is no problem. I think...

 

[snort]

I just discovered this thread. The right way to do what the OP wants is to make a TT-30 to 30 amp adapter, either 10-30 or 14-30. Tesla has stopped selling the 10-30 so that may force your hand.

The TT-30 to 14-50 is a second choice. You need to remember to dial down the current to 24 amps. In an ideal world if you forgot to do this, the breaker would pop and remind you to fix things. I prefer to never test breakers.... the breaker might be somewhere you can't reset it, especially if you're plugging in at an RV park after the manager has gone home for the night.

It turns out the car/UMC doesn't care if it sees single phase power plugged into an adapter spec-ed for two phase, or two phase power into an adapter spec-ed for single phase--it just does the right thing. The adapter connection only sees 3 conductors: either Hot1, Hot2 and Ground or Hot, Neutral and Ground. The 10-30 Neutral is connected to the ground conductor in the adapter. The car does insist that the single phase neutral and ground are matched and you get this wrong it will give you an error message, so if you see this you just need to swap the two hot leads. Nothing bad happens.

What I did is to buy an adapter like the one above, and replace the 14-50R with a L6-30R. I have a whole set of 30 amp adapters (6-30, TT-30, L14-30, extension, 10-30) so I standardized on the L6-30, because it was a bunch cheaper and smaller than the 10-30R I could find, and made an L6-30P to 10-30R adapter.

I'm pretty sure the reason Tesla doesn't encourage this sort of thing is because the electrical code deprecates plugging EVSEs into extensions or adapters. There's a good reason for that, but sometimes you have no choice. This is a case where the code makes things a little less safe.

-Snortybartfast

 

[jasonb]

I'll add my experience. I ghetto'd up a dryer extension cord (10-30 -> 14-50) for umc to plug into. I had to pull ground from 110v outlet to make umc happy. had to set current draw to 24amp. yuck. but it worked. and then i got s/w update which erased my 24amp setting. not good.

so now i'm thinking i'm going to put proper wall charger stat.

 

[Cosmacelf]

Yeah, software updates are notorious for resetting settings. It's a safety issue that Tesla lets fall through the cracks. While I have a bunch of adapters for the nema 14-50 that require dialing down the amp setting, I only use them for travel, not for regular use.

 

[davewill]

I'll add my experience. I ghetto'd up a dryer extension cord (10-30 -> 14-50) for umc to plug into. I had to pull ground from 110v outlet to make umc happy. had to set current draw to 24amp. yuck. but it worked. and then i got s/w update which erased my 24amp setting. not good.

so now i'm thinking i'm going to put proper wall charger stat.

That's because you wired it wrong. When making a 10-30 adapter, you wire the neutral on the 10-30 to the ground on the UMC, leaving the neutral disconnected. Then you label it most carefully so some idiot doesn't try to use it to power their RV and blow up all the appliances.

 

[jasonb]

That's because you wired it wrong. When making a 10-30 adapter, you wire the neutral on the 10-30 to the ground on the UMC, leaving the neutral disconnected. Then you label it most carefully so some idiot doesn't try to use it to power their RV and blow up all the appliances.

i thought about it a little bit and I understand what you are saying but I think I like my way better. If i'm touching stuff in garage, its got an honest ground on it. am i wrong? that said, since I dont have a gfci breaker its kind of a moot point.

ideally i would put a wall charger with gfci breaker. i did a 14-50 w/ gfci in backyard for welder but cant' reach it with car. rats.

 

[davewill]

i thought about it a little bit and I understand what you are saying but I think I like my way better. If i'm touching stuff in garage, its got an honest ground on it. am i wrong? that said, since I dont have a gfci breaker its kind of a moot point.

ideally i would put a wall charger with gfci breaker. i did a 14-50 w/ gfci in backyard for welder but cant' reach it with car. rats.

Since a 10-30 is almost always the only outlet on the circuit and the neutrals and grounds are bonded at the main panel, it's safe to repurpose the neutral as a ground. The wiring for the ground you're taking from the 5-15 may not be sized big enough for a 30a circuit, although that may not be a big deal. Also, if you're plugging in at a random remote location, there may not be a handy 5-15 around to plug into.

Also, how the official adapter from Tesla repurposes the neutral, so that would seem to be the way to go.

If the 10-30 isn't needed for any other use, it can be replaced with a 6-30 which does not have a neutral. If you're worried about the 24a setting, you can get one of the 30a adapters for the UMC, or get a wall connector and set it for a 30a circuit.