Quick Sanity Check on Dual Wall Connector Plans

[jimmyz80]

Since it looks like my wife's Model 3 will be arriving in the coming months to join my Model S, I really need to get off my butt and convert our garage from a one EVSE to two EVSEs. I think I have a sound plan in mind, but want to make sure there are no obvious flaws before I have at it. I'm planning on getting a permit and inspection for this, which is something I've never done before, so I really don't want to find out at the end that I made an expensive mistake.

My house has 200A service to a main panel outside, and all of the heavy loads (oven, AC units, etc.) have their breakers out there on the main panel. Then there is a 90A sub panel in my garage, fed from the main panel. Right now I have my single Wall Connector hooked up to a 50A circuit that's run directly from the main panel (50A breaker and 6AWG NM-B).

Originally I was thinking about doing a "power sharing" design with a 60A circuit split between the two Wall Connectors. Since we're not going to be living in the house too much longer, I'm thinking it may be advantageous to just run two individual 50A circuits (assuming a load calc allows it) to each Wall Connector. This way when we move out, I can just swap in NEMA 14-50 outlets at each location and the the house would be "Dual EV Ready" for any type of car.

Since I don't have additional breaker spots on the outdoor main panel, I was thinking about taking this approach:
1. Remove my existing 50A circuit from the main panel, and replace it with a 100A circuit that would terminate in a new sub-panel in the garage. Something along the lines of this one: CH4L125FP Eaton Cutler-Hammer CH 3/4-Inch Main Loadcenter, Single-Phase, 2 Circuits, Eight-Pole, #14 €“ 1/0 Wire, 125A, Nema 1

2. From the new sub-panel, run two 50A circuits, one to each Wall Connector.

The wiring would be 1-1-1 Aluminum SER (75C rating since no contact with thermal insulation) from the main panel to the new sub panel, and then 6/3 Copper NM-B from the new sub-panel to each of the Wall Connectors. The wiring would be pretty easy to run, since the main panel and the garage walls have crawl space on the back-side. So I can just tack up the SER/NM cables in the crawl space, and clamp them at the panels and Wall Connectors.

Does this seem like a reasonable plan?

 

[ShawnA]

Hi Jimmy,

Questions for you - I am not an electrician

Do your electric codes allow a remote sub panel like the one you showed without a main disconnect on it?
The sub panel does not appear to support a main disconnect and your 100 A breaker supplying it is in another location.
I don't think this is usually acceptable.

You intend to use both of your Wall connectors at 40 A.... Right? 40 A at 125% = 50 A breaker...

Shawn

 

[jimmyz80]

Hi Jimmy,

Questions for you - I am not an electrician

Do your electric codes allow a remote sub panel like the one you showed without a main disconnect on it?
The sub panel does not appear to support a main disconnect and your 100 A breaker supplying it is in another location.
I don't think this is usually acceptable.

You intend to use both of your Wall connectors at 40 A.... Right? 40 A at 125% = 50 A breaker...

Shawn

The existing sub-panel does not have a main breaker in it, and it passed code when the house was built in 2010. I'm not 100% certain but I suspect nothing has changed.

And yes, 50A circuits are to be set for 40A charging. 80A total load on a 100A circuit to the main panel.

 

[GSP]

@jimmyz80,

Do you have a newer HPWC, with the built in holder for the charging cable? If so, you could minimize install costs by keeping your 90 A sub panel and 50 A HOWC circuit as is.

Just add another 50 A breaker for the second HPWC, and use the new HPWC's power sharing feature to keep the total charging current of both cars at 40 A or less. If only one car is charging you get full 40 A speed.

When you move out install only one 14-50 and block off the second one (it will be pre-wired if the new homeowner wants to install another circuit).

GSP

 

[ShawnA]

HI GSP,

I was going to install 2 of the Gen 2 power sharing HPWC.
Why I did not:
1 They both feed from the same single breaker - That is great for me
2 You need some kind of additional junction box to splice the "wye" high current wiring one to each HPWC (1,2,3. or 4)
That was an expensive nuisance for me
3 You run light gauge signal wire between the shared units.
The junction box made it unnecessarily complex and expensive.

I thought they daisy chained through each other with the high current conductors - They do not.
Sharing will not work with one GEN 2 and one GEN 1 HPWC. Only multiples of Gen 2.
They are not made to share across 2 breakers only one breaker.
"Sharing" with them is a specific term of load balancing controlled by the signal wires between HPWCs.

So you may hook one Gen 1 to one 50A breaker and another Gen1 or Gen 2 to another 50A breaker
Be sure to set both of the HPWC at 40A.
if your system will support it. This is not "sharing" according to the way it was designed.
That being said it will work very well and is probably your least cost solution.

So, to further question Jimmy's original setup.
Jimmy when you remove the 90A from the Main panel, were you also going to remove the existing
50A breaker from that panel? It would then move to the garage and be half of the new
100A panel in the garage(?).

Shawn

 

[ai4px]

HI GSP,

I was going to install 2 of the Gen 2 power sharing HPWC.
Why I did not:
1 They both feed from the same single breaker - That is great for me
2 You need some kind of additional junction box to splice the "wye" high current wiring one to each HPWC (1,2,3. or 4)
That was an expensive nuisance for me
3 You run light gauge signal wire between the shared units.
The junction box made it unnecessarily complex and expensive.

I thought they daisy chained through each other with the high current conductors - They do not.
Sharing will not work with one GEN 2 and one GEN 1 HPWC. Only multiples of Gen 2.
They are not made to share across 2 breakers only one breaker.
"Sharing" with them is a specific term of load balancing controlled by the signal wires between HPWCs.

So you may hook one Gen 1 to one 50A breaker and another Gen1 or Gen 2 to another 50A breaker
Be sure to set both of the HPWC at 40A.
if your system will support it. This is not "sharing" according to the way it was designed.
That being said it will work very well and is probably your least cost solution.

So, to further question Jimmy's original setup.
Jimmy when you remove the 90A from the Main panel, were you also going to remove the existing
50A breaker from that panel? It would then move to the garage and be half of the new
100A panel in the garage(?).

Shawn

Expense for a Y to split out to two HPWCs? I bought a $17 Eaton 2 breaker 125amp sub panel. I’ve installed two 50 amp “br” type breakers in it for $9.86/ea. So creating a legal and safe Y connection in my garage added $40 to the price of my install.

 

[ShawnA]

Hi Ai4px,

I think you missed my point...
You have two circuits at 50 Amp each.
It's a good setup..
That is not the setup for sharing the way Tesla implements it.

If you have the signal wires for communication between HPWC for Tesla sharing
either car could draw 80 Amps (older car 2 chargers) or 72 Amps (newer car largest battery) which would
not cooperate with your 50 Amp breakers.
If you are sharing between two 32 Amp. cars you are in good shape.

Shawn

 

[ai4px]

Hi Ai4px,

I think you missed my point...
You have two circuits at 50 Amp each.
It's a good setup..
That is not the setup for sharing the way Tesla implements it.

Let me be a little more clear... I added a 50amp breaker to my main panelbox and ran one 6awg cable to the garage. In the garage, I have a 125amp rated subpanel box with two 50 amp breakers in it feeding two 14-50 plugs. So I really only have 50amp service that must be shared.... I just came up with a code approved way to make that one wire feed two plugs. Inspectors usually frown on having two wires in one terminal block.

I'm pretty sure you can get insulated terminal blocks that allow you to Y off to two outlets, but I'd still have to find an enclosure for them and I simply couldn't beat $17 for a sub panel. This is one of those times where doing it right is cheaper / easier.

 

[miimura]

3 port Polaris connectors run about $25 each, so doing a 4 or 6 slot sub-panel is actually cheaper than 3 Polaris connectors, one each for L1, L2, N required for a 14-50.

Polaris 4-14 AWG Bagged Insulated Multi-Tap Connector, Black-IPL4-3B - The Home Depot