Universal Mobile Connector Tesla NEMA 10-30 Adaptor Wiring

[CaliM3Hi]

Hi, I didn't seem to find an answer to the specific question, so posting here.
I rent, and have a NEMA 10-30R wall plug that is used for a dryer.
Tesla sells a 10-30 adaptor for the UMC (I'll be buying the latest version of UMC). My understanding, however, is that Tesla does not use the Neutral wire, but does require a Ground wire.
1. Does the Tesla adaptor route the plug's Neutral wire to the internal Ground in the UMC? My understanding is that it's a no-no to short Neutral to ground at the device level.

2. I was thinking of getting a splitter so that I wouldn't be plugging in and out of the wall plug often and could keep the dryer plugged in (though I would never run the two at the same time). I saw a comment on how a splitter might interfere with the UMC temperature sensor. How does a splitter cause that, and would it fix the issue if I unplugged the dryer from the splitter?

Thanks very much for your feedback.

 

[CaliM3Hi]

Yeah, makes sense that the range and heating are 240V. I just wasn't sure how to read the panel. When I get the car and UMC, I'll see how things go and definitely monitor the plug temperature. I think by using the 10-30 adapter, the car will auto set the charge current to 24A. If it doesn't, I'll be sure to set it manually.

 

[davewill]

Interesting scenario, but Tesla's info sheet and manual doesn't mention that as something to look out for on the 10-30, so it's possible Tesla already mitigated this situation:

https://www.tesla.com/sites/default/files/pdfs/installation-guides/NEMA_10-30_installation_guide_NA_en_ca.pdf

https://www.tesla.com/sites/default/files/pdfs/charging_docs/gen_2_umc/Gen2_Mobile_Connector_en_TW.pdf

I think the major difference with Tesla's solution is that the 10-30 adapter reports itself to the Mobile Connector as such via a chip on the adapter, so Tesla can treat it as a different case (connected to neutral instead of ground), whereas your conversion may not have made that distinction.

Maybe. We don't have any real data either way. It obviously hasn't been a big problem.

 

[davewill]

So the dryer outlet box has a ground wire that is connected to the receptacle's plate. After turning off the breakers for washer and dryer, continuity tester shows continuity between dryer ground and neutral, and also between dryer ground and washer (110v) neutral and ground.

There's only one panel I have found in the unit, which is a townhome in a 6 condo building. I don't know if this is considered a subpanel. The dryer outlet is about 6 feet from the panel. The dryer and water heater are the only 220v appliances. They have their own individual breakers and are on the same panel row (marked w/ red tape). The other breakers are for washer, dishwasher, range, heater, AC, and 'lights'.

No, that should be the main panel, any you should be fine.

 

[Rocky_H]

I think the major difference with Tesla's solution is that the 10-30 adapter reports itself to the Mobile Connector as such via a chip on the adapter, so Tesla can treat it as a different case (connected to neutral instead of ground), whereas your conversion may not have made that distinction.

I don't think there's anything to report or indicate. It really just uses two pins to read the voltage difference and then the ground pin. That's all it is using from the outlet. Whether that's the normal ground or this pseudo-ground-neutral of the 10-XX series outlets, there's nothing to do differently.

 

[stopcrazypp]

I don't think there's anything to report or indicate. It really just uses two pins to read the voltage difference and then the ground pin. That's all it is using from the outlet. Whether that's the normal ground or this pseudo-ground-neutral of the 10-XX series outlets, there's nothing to do differently.

But somehow that Leaf EVSE got fried by being connected to the neutral instead of the ground, so perhaps there are other risks. As that post said, neutral can potentially carry current from other loads, while ground doesn't unless there is a problem with the circuit.

 

[Rocky_H]

But somehow that Leaf EVSE got fried by being connected to the neutral instead of the ground, so perhaps there are other risks.

That is a totally different type of external risk that could happen based on the house's wiring. And it could be a potential thing that could happen to any EVSE.
But that has nothing to do with what you were saying:

I think the major difference with Tesla's solution is that the 10-30 adapter reports itself to the Mobile Connector as such via a chip on the adapter, so Tesla can treat it as a different case (connected to neutral instead of ground), whereas your conversion may not have made that distinction.

None of that is happening. A Tesla 14-30 plug or a Tesla 10-30 plug are the same thing inside, and they don't identify differently to make the Tesla UMC treat them differently. They both do the same thing as 30A rated plug connections, and that's it.

 

[Eric33432]

But somehow that Leaf EVSE got fried by being connected to the neutral instead of the ground, so perhaps there are other risks. As that post said, neutral can potentially carry current from other loads, while ground doesn't unless there is a problem with the circuit.

It is possible for the neutral, on a sub panel, to be a few volts higher (in reference to ground) than the same neutral wire is back at the service equipment if there is a heavy current flowing on it. It would depend on the size and length of the neutral wire and the amount of current flowing. How a few volts on a neutral can damage a Leaf I do not know.

It is also possible for the neutral on a sub panel to have a significant voltage on it if it is loose or the connections are corroded.

It is possible for the neutral wire from the POCO to come loose at the meter or service equipment where it is connected to the terminal that is also bonded to the local ground. In that event, the voltages between line and neutral can go higher than 120 volts (or lower) depending on the loads connected between L1 and neutral and L2 and neutral, which then are essentially in series with each other, because the local ground connection is a much higher resistance back to the source than the solidly connected neutral wire is. This can cause all sorts of damage to equipment. I have seen it happen.

I don't think any of this would be a reason not to use a 10-30 to send electrons to your Tessie whether from a main panel or sub panel.

 

[Eric33432]

So the dryer outlet box has a ground wire that is connected to the receptacle's plate. After turning off the breakers for washer and dryer, continuity tester shows continuity between dryer ground and neutral, and also between dryer ground and washer (110v) neutral and ground.

There's only one panel I have found in the unit, which is a townhome in a 6 condo building. I don't know if this is considered a subpanel. The dryer outlet is about 6 feet from the panel. The dryer and water heater are the only 220v appliances. They have their own individual breakers and are on the same panel row (marked w/ red tape). The other breakers are for washer, dishwasher, range, heater, AC, and 'lights'.

BTW, this looks to be a sub panel because there is no main disconnect. The main disconnect for your apartment is probably located close to wherever the electric meter is located.