Any electricians here?

[DerbyDave]

I don't interpret that drawing in the install manual the same way you do. That "one supply" is the main service panel, and each line coming off of it is interpreted by me as its own branch circuit with its own 60A breaker (consistent with the language).

So why would you need load sharing? Just wire each wall connector to its own branch circuit. We could have done this last year, and didn't need Tesla to help.

 

[MN-MS100D]

The point of load sharing is not to gain an advantage on a circuit, but to gain an advantage on a service. We want to maximize the power used for charging, while the main circuit breaker sees no increase in load, whether it be 1, 2, 3 or 4 Teslas charging on the electrical service.

The NEC, and the installation instructions for the HPWC are clear that each circuit needs to be protected individually by a circuit breaker like any other circuit.

 

[DerbyDave]

I can therefore have 1 circuit: 24 A, 60A. 100A protected by a circuit breaker servicing 4 wall connectors. If one or more wall connector is in use at a time, the circuit will never exceed the maximum circuit capacity also controlled by the circuit breaker. This assumes the end devices are properly configured to not exceed the maximum circuit capacity, whether one is in use or all 4. Tesla has made the controllers limit total use to not exceed designed load of the configured circuit and breaker.

 

[ZilWin]

If I had room for a second 60a breaker in my panel I would not have the need for load sharing a single 60a supply. Correct? Remember I am NOT an electrician. I totally understand and feel confident (kind of) that both of these connectors will work the way they are wired, AS LONG AS THE SOFTWARE DOES ITS JOB!! in the case that the software does not allocate the total 60a supply correctly then I see an issue with not having individual circuits with their own breakers. Again, I am NOT an electrician.

For the record, I am not a licensed electrician either. However I do understand a bit about power and load distribution. 40 years figuring out how television broadcast engineers could get themselves in so much trouble.
Load sharing in Wall Connectors and seperate circuit breakers for each unit are completely different issues. Separate breakers individually protect the load center from each wall connector. Load sharing apportions the charging duties to each wall connector so that it does not overload the load center by charging both vehicles at 48A at the same time. Either the charge management reduces the current each wall connector delivers to each car as they charge simultaneously or it only allows one or the other to charge at the full 48A. You are correct when you say that as long as the load management system works correctly you will not have an issue as each wall connector will operate in it's own turn or both at reduced rates.
Even with seperate 60A breakers and each wall connector set for 48A, using both at the same time will almost exceed the 100A service at your load center. Turn your dishwasher on or the air conditioner in the bedroom and 'poof' you've tripped the main 100A breaker. Even terminating each wall connector in a 60A breaker would require some smart load management either internal to the wall connectors software or manually by only charging one car at a time or manually throttling the current demand to both cars.
Ironically, the way it is wired right now, if both Wall connectors started charging at 48A you would trip the 60A breaker instantly and protect the rest of the system(so long as you don;t overload the wires between the splice and the breaker). With each connector on a seperate 60A breaker, if load management fails you have a very large overload in progress upstream of the 60A breakers in the load center. If there was a subpanel with a Master breaker and a 60A breaker for each wall connector instead of the splice it would protect everything upstream and downstream from a dual max charge scenario.

 

[a1machinista1]

For the record, I am not a licensed electrician either. However I do understand a bit about power and load distribution. 40 years figuring out how television broadcast engineers could get themselves in so much trouble.
Load sharing in Wall Connectors and seperate circuit breakers for each unit are completely different issues. Separate breakers individually protect the load center from each wall connector. Load sharing apportions the charging duties to each wall connector so that it does not overload the load center by charging both vehicles at 48A at the same time. Either the charge management reduces the current each wall connector delivers to each car as they charge simultaneously or it only allows one or the other to charge at the full 48A. You are correct when you say that as long as the load management system works correctly you will not have an issue as each wall connector will operate in it's own turn or both at reduced rates.
Even with seperate 60A breakers and each wall connector set for 48A, using both at the same time will almost exceed the 100A service at your load center. Turn your dishwasher on or the air conditioner in the bedroom and 'poof' you've tripped the main 100A breaker. Even terminating each wall connector in a 60A breaker would require some smart load management either internal to the wall connectors software or manually by only charging one car at a time or manually throttling the current demand to both cars.
Ironically, the way it is wired right now, if both Wall connectors started charging at 48A you would trip the 60A breaker instantly and protect the rest of the system(so long as you don;t overload the wires between the splice and the breaker). With each connector on a seperate 60A breaker, if load management fails you have a very large overload in progress upstream of the 60A breakers in the load center. If there was a subpanel with a Master breaker and a 60A breaker for each wall connector instead of the splice it would protect everything upstream and downstream from a dual max charge scenario.

So that's the long way of saying what?
I just got off the phone with the owner of the electrical company. He was really great and agreed that is is worth a second look. He will be coming over with the installing technician next week. I sent him a few snippets of the installation manual for him to look at, along with another file of the installation manual. Not a big deal on my end, I feel lucky that he's not the type of person to tell me to **** off not to question his work.

 

[ucmndd]

So why would you need load sharing? Just wire each wall connector to its own branch circuit. We could have done this last year, and didn't need Tesla to help.

Just because you install, for example, four wall connectors on four 60 amp circuits, doesn’t mean you have service to the facility that can support that much power on all four circuits continuously.

THAT’s what load sharing is for.

I generally agree that OP’s installation, with 48 amps of continuous power shared between two daisy chained 48 amp capable devices, isn’t really a problem. But scenarios quickly devolve from there. Imagine a scenario where you want 3 wall connectors and have 100 amps available to share between all three. Are you going to daisy chain or splice them all together on the same 100 amp circuit? Are you gonna run #2 copper to/through all of them? That would be dumb.

 

[DerbyDave]

The wall connectors properly configured for sharing will not overload the circuit(s) they are attached to -- period. If you have 3 wall connectors configured on a 100 Amp circuit where there is not 100 Amps available to that circuit, that would be an improperly provisioned circuit. Even then, the Wall connectors on that circuit will not draw more than the available power, and apportion it between the wall connectors. It will step down its draw to the available power. Even one wall connector on one circuit does this now, and did this before sharing was available. If the wiring is inadequate and gets hot, it will also step down or shut down, throwing errors. Tesla is very careful on power management.

 

[ucmndd]

The wall connectors properly configured for sharing will not overload the circuit(s) they are attached to -- period. If you have 3 wall connectors configured on a 100 Amp circuit where there is not 100 Amps available to that circuit, that would be an improperly provisioned circuit.

Obviously. That is not my point. My point is that would be a stupid way to install 3 or 4 wall connectors. Particularly when Tesla says plain as day they should each be on their own circuit in the installation manual. That’s the right way to do it. Lots of wrong ways might work too, but that’s the right way.

Even then, the Wall connectors on that circuit will not draw more than the available power, and apportion it between the wall connectors. It will step down its draw to the available power. Even one wall connector on one circuit does this now, and did this before sharing was available.
If the wiring is inadequate and gets hot, it will also step down or shut down, throwing errors. Tesla is very careful on power management.

Emergency thermal protection and detecting voltage sag is not really the same thing as “stepping down to draw the available power”. That’s not “power management” so much as “don’t burn the house down”.

 

[Rocky_H]

Load sharing in Wall Connectors and separate circuit breakers for each unit are completely different issues.

Yes. This doesn't really get talked about enough, but this new required installation with individual breakers does provide a bit more freedom in the wiring setups and amps per unit. Remember that in the original proposal listed in the product manual, it was saying up to 16 wall connectors shared. The software that Tesla has rolled out at this point only supports up to 4. So this was intended to enable more variety than the Gen2 setups.

In the old Gen2 system, where they could be wired together, you didn't get to specify amp levels per unit. You specified one main, like 100A breaker, you set that in the "master" unit, and then all others were just set as "slave", and they ALL had to support the full wire gauge of the main 100A line.

With this separate breakering, you can mix sizes more how you want, depending on if you know one or two of them are going for small range vehicles, or vehicles with slow onboard chargers, or you want to use some thinner wire, or whatever. You can set a main input line at 60A or 80A for the total. And you can set up your four shared ones as 60, 60, 30, and 30 if you want or some other combinations of different amps per unit.

 

[a1machinista1]

Yes. This doesn't really get talked about enough, but this new required installation with individual breakers does provide a bit more freedom in the wiring setups and amps per unit. Remember that in the original proposal listed in the product manual, it was saying up to 16 wall connectors shared. The software that Tesla has rolled out at this point only supports up to 4. So this was intended to enable more variety than the Gen2 setups.

In the old Gen2 system, where they could be wired together, you didn't get to specify amp levels per unit. You specified one main, like 100A breaker, you set that in the "master" unit, and then all others were just set as "slave", and they ALL had to support the full wire gauge of the main 100A line.

With this separate breakering, you can mix sizes more how you want, depending on if you know one or two of them are going for small range vehicles, or vehicles with slow onboard chargers, or you want to use some thinner wire, or whatever. You can set a main input line at 60A or 80A for the total. And you can set up your four shared ones as 60, 60, 30, and 30 if you want or some other combinations of different amps per unit.

Why would you set any at a lower amperage? Doesn't that the defeat the purpose of load sharing? That would be like me setting both of mine to 30a.

 

[Rocky_H]

Why would you set any at a lower amperage?

I just answered that:

depending on if you know one or two of them are going for small range vehicles,

or vehicles with slow onboard chargers,

or you want to use some thinner wire,

Those are three good possibilities if you know some of them won't need the highest capability and don't want to waste the cost on the extra thick wire. Wire costs money!

Doesn't that the defeat the purpose of load sharing? That would be like me setting both of mine to 30a.

Remember what I mentioned about how this was originally designed for up to 16 units? At some hotel or shopping center, they may have some longer wiring runs between the subpanel and the wall connectors, and maybe they want to just do the more moderate 30 or 40A wiring on those branches. That can save some money on copper wire if that's what they want to offer. And no, that doesn't defeat the purpose of load sharing. If they have 10 of those on 40A circuits, that could be 400 total amps! (Just talking about circuit ratings right now, not the 80% constant draw amount) They would need to load share to communicate not to overrun whatever the feed line is capable of.

 

[a1machinista1]

I would think 99.9% of people here are not concerned with more than two chargers.

 

[Rocky_H]

I would think 99.9% of people here are not concerned with more than two chargers.

Right, and in that case, the cost issues for N = 2 aren't as much. Later on, when they do open up the larger sharing groups, this can become more of a useful option when cost issues are bigger with a larger number of wiring runs to do.

 

[a1machinista1]

Right, and in that case, the cost issues for N = 2 aren't as much. Later on, when they do open up the larger sharing groups, this can become more of a useful option when cost issues are bigger with a larger number of wiring runs to do.

Sure