ELECTRICIANS! Please help!

[PO44O]

Hi everyone. Im very close to having everything ready and need help solving the missing piece.

I currently have 6-3 Romex running to a 14-50 NEMA outlet.

I will be replacing that outlet with a subpanel. Throwing on two seperate breakers which will be used to run two Tesla Wall Connectors. I know Ill be limited to 40A and want to split it 20A/20A when both my MY and M3 are charging at the dame time.

My question is.. what subpanel size should I buy? And what size of should those two breakers inside the subpanels be?

Thank you.

 

[jjrandorin]

Im not an electrician, but I think that you want (2) 50 amp breakers in that sub panel, and the wall connectors setup with load sharing of a 50 amp circuit so that they charge at max 40 amps separately, and 20 amps when running at the same time.

You also would get a lot better response if you posted this type of question in one of the vehicle battery and charging subforums (S / X / 3 / Y).

 

[terranx]

While it won’t make a big difference, the current limit in power sharing mode lets you set it down to the amp. So if you set each wall connector to 48A and then the network limit to 44A, you’ll get a 44A charge limit which is technically allowed with 6/3 romex.

 

[PO44O]

While it won’t make a big difference, the current limit in power sharing mode lets you set it down to the amp. So if you set each wall connector to 48A and then the network limit to 44A, you’ll get a 44A charge limit which is technically allowed with 6/3 romex.

I was thinking about pushing that min/max as you just posted but realized the difference when charging to 80% battery at 40A vs 48A is like 4.5 hrs vs 5.3. Decided to go with sleeping at ease and wake up with no difference in charge instead.

Thanks!

 

[PO44O]

Im not an electrician, but I think that you want (2) 50 amp breakers in that sub panel, and the wall connectors setup with load sharing of a 50 amp circuit so that they charge at max 40 amps separately, and 20 amps when running at the same time.

You also would get a lot better response if you posted this type of question in one of the vehicle battery and charging subforums (S / X / 3 / Y).

Thanks for the response. First time posting here.

Ill definitely cross post it over there. What you posted really makes sense. Any idea on the subpanel? I was originally thinking 50 but couldnt really find a 50 and see mostly 60A and 100A subpanels.

 

[terranx]

Thanks for the response. First time posting here.

Ill definitely cross post it over there. What you posted really makes sense. Any idea on the subpanel? I was originally thinking 50 but couldnt really find a 50 and see mostly 60A and 100A subpanels.

You can use a bigger subpanel as long as the breaker feeding the subpanel is appropriately sized. I'm using a 100A subpanel with a 65A feed servicing two tesla chargers.

 

[Cosmacelf]

You can use any sized subpanel as long as it rated for 50A or more. The 6/3 romex will be wired to the main lugs, the neutral bar and the ground bar. Make sure not to connect the neutral and ground bars. Use two 50A breakers for each of your Wall Connector feeds. You can use 6/2 NM-B cable for those, or even 8/2 MC cable, or THHN in conduit (see here: Advice for EV Charging in North America).

 

[sovereignbat]

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