Gen3 Dual Charger Load Sharing

[Rocky_H]

@Tronguy Yes, all of that just like that. It really is the same layout as just doing a subpanel. The "smarts" or "sharing" part of it is that you can do what looks like vastly overloading that subpanel, and the "appliances" will just make sure to never let themselves overload it.

 

[EdJack]

The wiring is split in a separate junction box using "Polaris IPL250-3B multi-tap insulated connector", you can't hookup three separate 6 AWG wires on a single "marrette" type twist connector. My installation is absolutely done to code, having an additional sub-panel just to split my circtuit is the same as using multi-tap connector in a junction box, it's approved. ESA also allows having two EVSE (Car Chargers) hooked up on a single circuit if the EVSA have current limiting software, which is the case for the Tesla Gen3 chargers.

I didn't post this information to get doubted on my electrical installation, I wanted to give information on how Gen3 Power Sharing worked as more and more people are getting a second EV and this question is asked.

In no case do I suggest anyone doing this themselves, always use an electrician if you don't know what you are doing and get a permit.

Your installation with branched wires from a single circuit would be compliant with daisy-chained Gen 2 Connectors.

However, Gen 3 Connectors doesn't allow for branched wires. They each need individual circuits, individual breakers, and individually runs sets of wire. Either from Main Panel or Sub Panel.

Just a friendly suggestion. Just swap out the junction box with the Polaris Tap Connector with a small Sub Panel. Input to Sub Panel is same input as Polaris Tap. Then 2 breakers in the Sub Panel, with the outputs being the 2 outputs of the Polaris Tap run directly to the 2 Wall Connectors. (Would also need a neutral from Main to Sub). Then you would be compliant with Tesla Installation Manual. Would be less than $70 for the Sub Panel.

Also, the beauty of a Sub Panel is you have more options, functionality, and future-proofing. You can add more Wall Connectors, or hang additional things like NEMA receptacles for Tesla Mobile Chargers and such.

What if you fry your battery or your Tesla catches fire or something, and you try to make a warranty claim with Tesla or Insurance claim. Then Tesla or Insurance Company see the Wall Connectors aren't installed per manual specifications? May void warranty or Insurance Company deny claim.

 

[davewill]

Maybe I'm missing something, but didn't he put separate 60a circuit breakers on each of the EVSEs? That's what's in the disconnect boxes in the picture. That would seem to fit the bill.

 

[Whatstreet]

Why do we have redundant circuit breakers? If the sum of the loads, meaning any one of them also, exceeds 60A it will break. It's just as safe, if all wire involved is rated for 60A. But building codes will be building codes.

 

[davewill]

Why do we have redundant circuit breakers? If the sum of the loads, meaning any one of them also, exceeds 60A it will break. It's just as safe, if all wire involved is rated for 60A. But building codes will be building codes.

Because of the wider capabilities of Gen3 power sharing. You can have two wall connectors of differing amperages and an overall budget of yet another amperage. That requires different circuit breakers. If all the wall connectors and the overall budget was the same 60a, one might argue that a single breaker is safe, but Tesla didn't write the install instructions that way, so you're not allowed to do it.

 

[Cosmacelf]

All right. So, this feels a little weird, but bear with me here. Starting from the top:

1. In the main breaker panel, there's a duplex 60A breaker that provides (at most) 48A of continuous load. Two hots, a safety ground, and maybe a neutral leave the breaker box.
2. Now, on my Gen 2 WC, the two hots, neutral, and ground hit the WC and there it stops. If I add another Gen 2 WC, I bolt on another pair of hots, a neutral (not sure about the neutral, got to go dig out the manual), and a ground and connect that to the next Gen 2 WC in line.
3. On the Gen 3 WC, the 60A service wire from the breaker panel shows up and goes into a sub-panel that is mounted next to or near the first Gen 3 WC. The sub-panel accepts that 60A service feed and connects said feed to two (2) each 60A breakers.
4. Each of the 60A service feeds from those two (2) 60A breakers in the sub-panel then go to a Gen 3 WC.

So: For current to get to a Gen 3 WC in case #3 above, it first goes through a 60A breaker on the main panel, then one of the two 60A breakers in the sub-panel, and then to the associated Gen 3 WC?

Feels weird, somehow. But I guess in a Standard House it's not unusual for current to go through the Main Breaker in the main, then through innumerable breakers on each circuit, and so on.

And total current in the feed back to the main breaker panel never exceeds 48A, right?

Yes, just delete all talk of the neutral in the above. EVSEs don’t use or require a neutral wire, just two hots and a ground.

 

[Cosmacelf]

Maybe I'm missing something, but didn't he put separate 60a circuit breakers on each of the EVSEs? That's what's in the disconnect boxes in the picture. That would seem to fit the bill.

I agree, which is why it is code compliant. Those boxes have appropriate disconnect fuses/breakers in them as per the OP.

 

[Whatstreet]

Because of the wider capabilities of Gen3 power sharing. You can have two wall connectors of differing amperages and an overall budget of yet another amperage. That requires different circuit breakers. If all the wall connectors and the overall budget was the same 60a, one might argue that a single breaker is safe, but Tesla didn't write the install instructions that way, so you're not allowed to do it.

I think there is a misunderstanding in the Tesla instructions. A wall connector needs a 60A breaker in the main panel, that's true. But circuit sharing implies a group of wall connectors all pull from the same breaker in the main panel. The host wall connector manages the current of each client on the wall connector network to not exceed 48A for a 60A breaker. I would be surprised if there was a local building code for this in my county.

 

[Rocky_H]

A wall connector needs a 60A breaker in the main panel, that's true.

No, it's not necessarily. That main panel breaker will be the amount for the entire feed for the whole group of connectors. That may be a 100A or a 150A breaker. That's what runs out of the main panel to the subpanel.

But circuit sharing implies a group of wall connectors all pull from the same breaker in the main panel.

Sure, eventually that current does come through that breaker in the main panel and then through the sub. But people can choose the wire size and breaker size for whatever setting they are going to use for each individual wall connector in the subpanel, and those can be different levels.

I would be surprised if there was a local building code for this in my county.

It's a little new and unfamiliar to a lot of inspectors. This allowance for software managed load control systems was I think implemented in 2020 NEC, so it's not implemented everywhere and still unknown to some inspectors in some places even where it is implemented.

 

[Whatstreet]

No, it's not necessarily. That main panel breaker will be the amount for the entire feed for the whole group of connectors. That may be a 100A or a 150A breaker. That's what runs out of the main panel to the subpanel.

That is one scenario, but there are others.

For residential, many people will have one line pulled for an EVSE then later would like to add another EVSE and due to cost would prefer not to pull another line. They would like to share the line that is already installed by using smart EVSEs that will negotiate current for each so that the maximum current for the line is not exceeded. All wiring for the second EVSE meets the rating of the main panel circuit breaker so either EVSE could pull maximum current though not at the same time.

In that case adding redundant breakers seems unnecessary and I would be hard pressed to tell you which one would trip first during an overload if they were installed. Tesla's recommendations should consider this scenario also. Building codes are the standards not Tesla's recommendations. There needs to be judgment for the circumstances.

 

[davewill]

I think there is a misunderstanding in the Tesla instructions. A wall connector needs a 60A breaker in the main panel, that's true. But circuit sharing implies a group of wall connectors all pull from the same breaker in the main panel. The host wall connector manages the current of each client on the wall connector network to not exceed 48A for a 60A breaker. I would be surprised if there was a local building code for this in my county.

No misunderstanding, they're pretty clear. I think Tesla didn't want to complicate things by creating a different set of instructions for the specific case of multiple wall connectors sharing a single circuit.

For residential, many people will have one line pulled for an EVSE then later would like to add another EVSE and due to cost would prefer not to pull another line. They would like to share the line that is already installed by using smart EVSEs that will negotiate current for each so that the maximum current for the line is not exceeded. All wiring for the second EVSE meets the rating of the main panel circuit breaker so either EVSE could pull maximum current though not at the same time.

In that case adding redundant breakers seems unnecessary and I would be hard pressed to tell you which one would trip first during an overload if they were installed. Tesla's recommendations should consider this scenario also. Building codes are the standards not Tesla's recommendations. There needs to be judgment for the circumstances.

But code specifically says to follow the manufacturer's instructions. So there it is.

Besides, there isn't much difference between a junction box and a subpanel. In your example, you simply put a small load center on the existing line near the first wall connector, then run circuits on breakers from there to the first and second wall connectors. Easy peasy.

 

[Ninja1000]

Your installation with branched wires from a single circuit would be compliant with daisy-chained Gen 2 Connectors.

However, Gen 3 Connectors doesn't allow for branched wires. They each need individual circuits, individual breakers, and individually runs sets of wire. Either from Main Panel or Sub Panel.

Just a friendly suggestion. Just swap out the junction box with the Polaris Tap Connector with a small Sub Panel. Input to Sub Panel is same input as Polaris Tap. Then 2 breakers in the Sub Panel, with the outputs being the 2 outputs of the Polaris Tap run directly to the 2 Wall Connectors. (Would also need a neutral from Main to Sub). Then you would be compliant with Tesla Installation Manual. Would be less than $70 for the Sub Panel.

Also, the beauty of a Sub Panel is you have more options, functionality, and future-proofing. You can add more Wall Connectors, or hang additional things like NEMA receptacles for Tesla Mobile Chargers and such.

What if you fry your battery or your Tesla catches fire or something, and you try to make a warranty claim with Tesla or Insurance claim. Then Tesla or Insurance Company see the Wall Connectors aren't installed per manual specifications? May void warranty or Insurance Company deny claim.

My installation was approved by 2 master electricians, it's up to code and I'm also an electrical engineer. A tap connector is allowed to split a circuit, each Gen3 charger is protected by it's own 60amp breaker. Putting a sub-panel with 2 60amp breaker with be the exact same results, it's in 3 boxes instead of one, wiring is exactly the same.

And please explain how this would fry a battery? The tesla charger is in the vehicle, the wall charger only supplies current to the vehicle. The vehicle will use the maximum allowed current depending on the scenario.

 

[Whatstreet]

ut code specifically says to follow the manufacturer's instructions. So there it is.

My conclusion is I would be better served buying EVSE's with a manual that did not make a one fits all recommendation. I have already found one.

 

[MattM24]

My installation was approved by 2 master electricians, it's up to code and I'm also an electrical engineer. A tap connector is allowed to split a circuit, each Gen3 charger is protected by it's own 60amp breaker. Putting a sub-panel with 2 60amp breaker with be the exact same results, it's in 3 boxes instead of one, wiring is exactly the same.

And please explain how this would fry a battery? The tesla charger is in the vehicle, the wall charger only supplies current to the vehicle. The vehicle will use the maximum allowed current depending on the scenario.

I don’t believe it was clear before that your Wall connectors are on separate breakers. All sounds correct in my opinion.