Home 240v charging question/HPWC

[HankLloydRight]

We just moved into a new house, and in the back of one of the garages was a NEMA 6-20 outlet. I think it was used for an air compressor previously. It uses 12-2 G NM-B Romex to the main panel where there's a 15 amp/240v breaker.

Since the 6-20 outlet is rated for 20 amps, can I just swap in a 20 amp breaker and charge my car at 240v@16a?

Also, if instead I remove the outlet and run that 12-2G wire directly into a 1st Gen HPWC, can the HPWC be set for that particular power input?

Otherwise I can gerryrig a NEMA 10-30 adapter with my UMC and just set the charge current in the car appropriately.

Thanks.

 

[Rocky_H]

Huh. That's a little weird that they would have it on a 15A circuit. 12 gauge Romex is rated for a 20A circuit, so yeah, that would be fine to just change the breaker to a 20A, and then get the Tesla 6-20 adapter. Easy peasy.

I do think that 20A was a common enough setting that most of the wall connectors had that available, so any of those versions should work with that if you wanted instead of an outlet. They have the manuals for each version on Tesla's website, so probably make sure if 20A is available for the version you would get.

Since you asked about the Gen1, I went and checked the manuals and learned something surprising. I thought they all supported lower level circuits, but not quite. There were the A & B versions of the Gen1, and they only support 40A and up! The C & D versions of Gen1 support lower levels like 15, 20, 30, etc. up to 100A. And the Gen2 supported lower levels too.

 

[Brock-WI]

I would confirm it is 12-2 on both ends and swap it to the 240v 20a breaker and use that, it is the safest way to go. I have put the 6-20's in using #12 in a couple of houses, it's the easiest thing to do and charing at 16a 240v is pretty good and not a huge load on most home systems.

 

[HankLloydRight]

Great, thanks for the replies.

My Gen1 UMC doesn't have a 6-20 adapter as far as I can tell. Gen 1 NEMA Adapters

I have it working now at 240v@12a on the 15amp breaker. Off to HD to get a 20 amp breaker.

I ended up direct wiring my Gen 1A HPWC to the 12-2 romex (see photo below). I know it's a little gheto, but it works. I would like to find a proper strain relief that fits in the side of the HPWC. I set the DIP switch to the lowest setting (40amps) and when I plugged in the car, I jumped in VERY QUICKLY to dial down the charging amps to 12. It (of course) had defaulted to 32!

And then off it went! Charging at 2880w (8mph) now. Hope to get up to 3,840 later with the new breaker.

Up until now in this new house I was charging at 120v/12amps in the main garage (SLOOOW), but I now have a GFCI problem over there whenever it rains.

 

[Rocky_H]

My Gen1 UMC doesn't have a 6-20 adapter as far as I can tell. Gen 1 NEMA Adapters

Oh yeah, Tesla has a very thin selection of adapters for the 1st gen UMC. EVSEAdapters.com filled in Tesla's gaps by making really good plug adapters that fit the Tesla UMCs. Buy this one:
NEMA 6-20 Adapter for Tesla Model S and Model X Gen 1 – EVSE Adapters

I ended up direct wiring my Gen 1A HPWC to the 12-2 romex (see photo below). I know it's a little gheto, but it works. I would like to find a proper strain relief that fits in the side of the HPWC. I set the DIP switch to the lowest setting (40amps) and when I plugged in the car, I jumped in VERY QUICKLY to dial down the charging amps to 12. It (of course) had defaulted to 32!

Wow, creative. I'll give you props for that. So you had one of the original ones that can't set for lower than 40A circuits, huh? That's too bad.

 

[HankLloydRight]

. Buy this one:
NEMA 6-20 Adapter for Tesla Model S and Model X Gen 1 – EVSE Adapters

Wow, I didn't know those even existed! Thanks. I might get one of those for my UMC, but for now, the HPWC is working great.

Wow, creative. I'll give you props for that. So you had one of the original ones that can't set for lower than 40A circuits, huh? That's too bad.

Yup. The previous owner got it when he bought the car new in 2014, and gave it to me when I bought it in 2017. It's pretty beat up and the front panel LEDs have never worked, but it still charges the car. I previously had a NEMA 14-50 plug attached to it to plug into the socket at my previous house. I also have the stainless steel wall mounting plate, but don't have the proper screws to mount the HPWC to the mounting plate. So I just leave it on the shelf there.

I definitely like having this setup instead of the UMC hanging off a wall socket.

 

[Rocky_H]

I definitely like having this setup instead of the UMC hanging off a wall socket.

Well...I don't know that I would for a long term solution. That wall connector is set for a 40A circuit, and only have the setting lowered in the car's settings. The reduced amp settings in the car are far from permanent. There are at least two things that have happened more than a few times that can cause the car to forget that:
1. Software updates. I've seen some reports of this, where an update in the car caused it to forget someone's memorized lower amp setting at home or some location, and it reverts back to the default higher level.

2. GPS location being off. These are tagged to a location, so it will use that when you are back at home in your garage, but I've had this happen to me, where there is something causing the GPS location to be off by about a block or two, and when I get home and plug in, it tries to start charging at the full, highest rate.

So I wouldn't trust that very well for a permanent setup. The amp limits in the UMC plug adapters are more solid and send the right maximum amp signal to the car. And yes, the 3rd party ones from EVSEAdapters do have that amp limit signaling built into them too, like the official ones, which is why I highly recommend them.

 

[HankLloydRight]

All valid points and I've also seen the GPS be off a bit.

But worse-case scenario, wouldn't the breaker blow before any harm is done?

 

[Rocky_H]

All valid points and I've also seen the GPS be off a bit.

But worse-case scenario, wouldn't the breaker blow before any harm is done?

It probably would. It is supposed to. But breakers do have some failure rates, where a small % of them are defective or the mechanism are old or whatever, and it may not. It's kind of like doing something that's likely to burn a bit because your smoke alarms are supposed to let you know before it gets out of hand. Better to not set up a dangerous situation, and expect the emergency backup system to be foolproof.

 

[HankLloydRight]

It probably would. It is supposed to. But breakers do have some failure rates, where a small % of them are defective or the mechanism are old or whatever, and it may not. It's kind of like doing something that's likely to burn a bit because your smoke alarms are supposed to let you know before it gets out of hand. Better to not set up a dangerous situation, and expect the emergency backup system to be foolproof.

I had a feeling you were going to say this. I bought a new breaker, so it's not old. But I understand the risks.

I'm having an electrician come in soon to do some other work in the house, and I'll likely have him run a 50amp circuit from the same panel and replace the existing 15am circuit. The HPWC is only 5 feet from the main panel (through a wall), so it's a short, easy run to replace. I also want to get a 30 or 50amp circuit run to my main garage so I can charge there as well.

 

[Rocky_H]

"soon" sounds good. I like what you've got temporarily set up and would be fine using it for a few months. I just wouldn't want that to be a permanent setup for years.

 

[NickFie]

I'm having an electrician come in soon to do some other work in the house, and I'll likely have him run a 50amp circuit from the same panel and replace the existing 15am circuit. The HPWC is only 5 feet from the main panel (through a wall), so it's a short, easy run to replace. I also want to get a 30 or 50amp circuit run to my main garage so I can charge there as well.

That will be a good setup.

 

[HankLloydRight]

"soon" sounds good. I like what you've got temporarily set up and would be fine using it for a few months. I just wouldn't want that to be a permanent setup for years.

Yup. I'm waiting on permits and crew availability to install Tesla solar and 2 PW2s, so I'm sure to get it all done on or before that happens.