Tesla Mobile Connector “chip” ?

[Gwelo]

Hello all,
The home we just moved into has a 220v outlet under the sink tied to a 60 amp breaker used for an On Demand water heater. We installed a Heat Pump water heater and removed the on demand unit. Since the outlet in on an outside wall I pulled the wires thru and hooked up an Eaton outdoor rated box with a 14-50 Eaton receptacle to use with our Tesla Mobile Connector.

The inspection report on the home called out the 60 amp breaker as having insufficient wire size which could pose a fire hazard. No mention of the wire size or what would be appropriate.

I could find no markings on the wire I could see (4 wire, orange sleeve) so I changed the breaker to 30 amps, hooked everything up and plugged in my friends 2020 model Y. The charge screen went to 32 amps very quickly so I changed it to 24 thinking the 30 amp breaker would trip. The car charged and everything was fine.

Doing a little research I understand the Mobile connector has a “chip” that reads the circuit to limit charge current to an appropriate level. Is my understanding correct or am I off base here? If true, I’m thinking of changing the breaker to 40 amps for faster 32 amp charging.

Thoughts welcome.

 

[RayK]

A 14-50 mobile connector (UMC) adapter plug will "tell" the UMC that it's plugged into an outlet which is able to deliver a continuous 40A but will be limited to 32A by the UMC. If you have changed the breaker to a 30A, then your outlet should be a 14-30. That will require a 14-30 adapter plug from Tesla.

 

[Gwelo]

Thank you! That makes sense. I way overthought that.

 

[ewoodrick]

That's not a good thing to do. Yes that car will recognize that the circuit is overloaded and roll back charging appropriately. But that's a safety feature and should not be a primary feature.

The plug was probably wires as an intermittent duty connection with a wire size too small for constant duty. A constant duty connection has to be derated by 80% over a standard duty connection.

You should be able to replace breaker with a 30A and use a 14-30 socket and adapter to become "safer". The wall connector may allow you to dial it to 40A, for a little more charge, but 30A should be sufficient 99.9% of the time.

 

[RayK]

Thank you! That makes sense. I way overthought that.

Note that switching over to the 14-30 outlet, or any other 240V 30A outlet for that matter, means that you'll get a maximum of 24A for charging (80% de-rating of breaker). I would think that your wiring should be able to handle a continuous 32A on a circuit which previously had a 60A breaker, but you should try and double-check the gauge of wire that's being used.

edit: Also note... if you switch the breaker to a 40A unit, then you still will NOT be able to charge to 32A since you're still stuck with a 30A (14-30) outlet. There's no 40A outlet that is a NEMA standard.

 

[Gwelo]

Yes, no thought of changing to 40A, Need to determine the wire size first. I have a sample and will measure o.d. to see what that tells me.

 

[MP3Mike]

I could find no markings on the wire I could see (4 wire, orange sleeve) so I changed the breaker to 30 amps, hooked everything up and plugged in my friends 2020 model Y.

Orange normally means that it is 10 AWG, which is rated for a maximum of 30A, meaning that you should charge at no more than 24A.

Since the outlet in on an outside wall I pulled the wires thru and hooked up an Eaton outdoor rated box with a 14-50 Eaton receptacle to use with our Tesla Mobile Connector.

Since that is probably 10 AWG wire, you should replace the 14-50 outlet with a 14-30, and buy the matching adapter from Tesla.

 

[EdJack]

Step 1: Determine Wire Size.
Step 2: If you haven't determined Wire Size, go back to Step 1.

All other decisions are made once wire size is determined.

The wire size will determine what breaker size to use and what receptacle to use. Also, I believe the "chip" you are referring to is based on what pigtail adapter is plugged into your Mobile Connector. So you should use the proper pigtail adapter sized to the receptible, not try and use an oversized pigtail that will try and pull more juice than it should, and then trying to have the Mobile Connector try to dial it down or manually trying to dial it down on the Tesla display screen.

 

[Cosmacelf]

The outer sheath being orange is a big red flag. @MP3Mike is correct. That sounds like Romex cable (vinyl outer wrap) and orange usually means rated for a 30A breaker.

Maybe take a picture of the opened up panel and we can probably tell you what wire gauge, but at this point, I would assume 10 AWG and good for a 30A receptacle/breaker. So you are likely looking at buying:

- NEMA14-30 receptacle
- Tesla 14-30 adapter

The Tesla 14-30 adapter will tell the Mobile Connector and thus the car to only charge at 24A.

 

[Gwelo]

Yes, wire is #10 so 30 amp breaker is correct and in place. Just ordered the 14-30 adapter from Tesla. Looking for Hubbell or ? 14-30 receptacle to replace the 14-50, any recommendations?
Thanks for all the help!

 

[EdJack]

Hubbell, Bryant, or Cooper are usually what people recommend.

At least one good thing about going with a 14-30 is you can typically get a Hubbell or Bryant much cheaper. Due to supply/demand issues where everyone with an EV is buying 14-50, the prices for 14-50 have really gotten jacked up. A 14-30 might even be half the price of a 14-50 due to sellers jacking up prices on 14-50 Hubbells due to EV demand.

 

[Gwelo]

I decided to move the location and install a Tesla Wall Connector so I started a new thread. Take a look and let me know what you think.

Q's on Moving my Charging Station

I'm not happy with where my charger is so I want to move it about 50' for better access. I have an existing Eaton outdoor box that is fed through the wall of the house. See: Tesla Mobile Connector “chip” ? I will replace the Eaton box with a junction box and run wire/conduit to the new...

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