208v panel to nema 14-50 not charging my Model 3 in Arizona

[eprosenx]

208v can also come from a 240v three-phase delta transformer. The voltage between any two legs will be 240v. The voltage between two of the legs and the neutral (i.e. L2-N and L3-N) will be 120v. The other leg will be 208v to the neutral. That leg is often referred to as the high leg. If your electrician gave you just the 208v high leg and the neutral and that is what he is referring to as 208 single phase then that is probably the cause.

If one of the two hot legs is the high leg that may be the problem but since I do not think the UMC uses the Neutral I do not think that would matter.

Two points of clarification here:

1. The service you describe is “240v three phase high leg delta”. Basically that says that only one phase pair is center tap grounded (neutral). There are other “delta” wiring methods (that could also be 208v or 240v) like corner grounded or ungrounded... We have seen one ungrounded setup discussed here in the forums which is kind of un-nerving as it requires special monitoring to be safe. I know the Wall Connector WILL NOT WORK on an ungrounded system. The UMC is a bit more forgiving in some ways though (specifically that it will accept hot/hot connections or hot/neutral connections without changing a setting unlike the Wall Connector), so I don’t know what it’s behavior is.
2. The UMC does not use the neutral, but it sure as heck does test to make sure ground is good and I suspect the way they do this in part is by measuring voltages from the hots to ground. These tests rely on neutral and ground being bonded and they likely dislike it when from each hot to ground don’t match.

Great info though, thanks for posting!

 

[NickFie]

My electrician says we have the nema 14-50 set up as a :single phase with a neutral"...

Tell the electrician Tesla HPWC or 14-50 should have two hots and a ground. The in-car Charger is happiest with 205-240 Volts. Can charge at 110 Volt, but slowly and inefficiently.

As mentioned earlier, Tesla doesn’t use neutral pin in 2-hot connectors. 14-50 socket neutral obviously should be connected according to code.

 

[233.3]

The same $520 cord, when I bring it home, charges my car on my nema 14-50 outlet from my home 220v system.
-B

OP used same UMC and home and it worked so that test has already been done. (I believe someone suggested this, maybe I misread)

2. The UMC does not use the neutral, but it sure as heck does test to make sure ground is good and I suspect the way they do this in part is by measuring voltages from the hots to ground. These tests rely on neutral and ground being bonded and they likely dislike it when from each hot to ground don’t match.

If that is correct and the OP does have a high leg delta system and the high leg was used then that would be the problem and I would predict that the UMC would indicate either a voltage or ground problem. Unless we hear from the OP on voltage measurements we may never know.

 

[doghousePVD]

Thanks for the info.... he does say it's single phase with a neutral.... maybe that's not going to work...

That may be the the problem. It needs a ground, not a neutral.

Also, check the rotating switch in the box. My electrician set it wrong ("test mode" IIRC) and the charger didn't work.

 

[doghousePVD]

I hadn't even considered that they might be on three-phase delta system. I worked at a business with that and it was very unique (old school with two transformers)... had to pay careful attention to how you hooked circuits up in the panel.

If you have 208V, you are on a three phase system.

 

[Big Earl]

If you have 208V, you are on a three phase system.

Obviously. The question is which three phase system and how did the electrician wire it?

 

[Big Earl]

That may be the the problem. It needs a ground, not a neutral.

Also, check the rotating switch in the box. My electrician set it wrong ("test mode" IIRC) and the charger didn't work.

It can work with neutral instead of ground if it’s wired properly. Tesla sells a NEMA 10-30 adapter for the mobile connector, which is ungrounded.

The mobile connector doesn’t have the internal rotating power setting switch like the wall connector does. It also auto-switches between line-to-line and line-to-neutral modes unlike the wall connector, which has a dip switch for that setting.