Any drawback to future proofing a single Tesla wall connector with 100 amp circuit?

[Antares Nebula]

Any drawback to future proofing a single Tesla wall connector with 100 amp circuit?

Want to install a Tesla Wall Connector for one Tesla (Model 3). May or may not buy additional Teslas in future. Since I (that is my electrician) have to do the electrical work for one connector, which only requires a 60 amp breaker (per Tesla website), should I go ahead and wire it all for a 100 amp breaker (per Tesla's rec for multiple Teslas and 2+ wall connectors)?

Besides any additional costs, is there any other drawback, like the potential to over load the single wall connector (overheating, fire risk, etc.)?

It's unclear to me because, on the one hand, you don't want a larger breaker and circuit than you need. But, on the other hand, even in the future if you had two wall chargers, you may not be using them at the same time, so it is the same risk of having a 100A circuit for only a single wall charger during those single use periods.

Thanks!

 

[F14Scott]

I think anything over 60 amps requires a manual disconnect switch, by NEC code.

 

[Daniellane]

That’s exactly what I did for my first wall charger for my Model S. I added a small 125a sub-panel (acts as a disconnect) and pre-wired for a 2nd Charger which I added when we got our 2nd Tesla (Model 3) Worked out great!
I posted these videos on YouTube of the set up:
Tesla Model 3 & Model S Load Sharing 2 HPWCs (720p)

Tesla Wall Charger Cable Management

Tesla Wall Charger Cable Management System Upgrade.

 

[Rockster]

Future proofing your installation in this way is ideal. I did the same thing, starting with one wall charger and then going to two when we got the second Tesla.

As for a disconnect, I’m not an electrician but I don’t think a disconnect is required if the wall charger is within a certain distance of the electrical panel.

Here’s my installation before I closed up the wall:

 

[araxara]

I have 3 HPWCs each on a 100A breaker in a 125A panel. They are wired together to "intelligently" share power using a Master/Slave/Slave configuration. I have tried to charge all the Teslas (Model-S 80A, Model-X 72A & Model-3 48A) together occasionally, but generally I have different times set so there is minimal overlap. Now, unfortunately, all new Teslas sold have lower amperage Level-2 charging so my setup may be overkill.

 

[Zaxxon]

No, no downside other then cost. And if you do eventually add other HPWCs, you will likely come out ahead on cost vs retrofitting later

 

[Antares Nebula]

Thanks everyone for all the responses. Very helpful!

 

[Antares Nebula]

Follow up question:

If there was some kind of resistive failure, you would want it to cut off at 60 amps vs 100 amps. Maybe rather than having two wall connectors connected together with a 100 amp circuit (as Tesla recommends), it's better to have two separate 60 amp circuits connected to independently wired wall connectors?

 

[Runt8]

Follow up question:

If there was some kind of resistive failure, you would want it to cut off at 60 amps vs 100 amps. Maybe rather than having two wall connectors connected together with a 100 amp circuit (as Tesla recommends), it's better to have two separate 60 amp circuits connected to independently wired wall connectors?

I’m not qualified to answer your question from a safety perspective, but from a charging perspective, the answer is “it depends.” An unshared 60 amp circuit would allow a Model 3 to always get the maximum charge rate (as opposed to sharing a 100 amp circuit between two Teslas). However, some Model S and X’s can charge at a higher rate so having a 100 amp circuit would allow them to charge faster (when only one vehicle is charging).

Probably the most likely answer is, either way will allow you to charge multiple Teslas fast enough that it won’t matter which you choose.

 

[Daniellane]

I’m not qualified to answer your question from a safety perspective, but from a charging perspective, the answer is “it depends.” An unshared 60 amp circuit would allow a Model 3 to always get the maximum charge rate (as opposed to sharing a 100 amp circuit between two Teslas). However, some Model S and X’s can charge at a higher rate so having a 100 amp circuit would allow them to charge faster (when only one vehicle is charging).

Probably the most likely answer is, either way will allow you to charge multiple Teslas fast enough that it won’t matter which you choose.

Exactly S & Xs had 72 amp chargers until very recently as my Model S does. Some older Model S’s have dual 40 amp chargers (80 amps). In our setup (See post#3) we have a 100 amp & a 50 amp circuit breaker in a 125 amp sub panel. The two wall chargers share the 100 amp circuit and a the 50 amp breaker powers a NEMA 14-50 outlet. I make sure the 50 amp breaker is always off when the 100 amp breaker is on.
The inspector said this was perfectly fine & legal.
The 14-50 is just used as a backup in case of a wall charger failure... or for driveway charging. On at least one occasion I had to use it to do a firmware update to the mobile charger that was part of a normal firmware to the car.

 

[Antares Nebula]

Thank you @Daniellane, @Rockster, and everyone else. I really like @Daniellane setup, and @Runt8 makes an excellent point.

The only other possible improvement I can think of is having two separate 100 amp circuits or even a combined 200 amp circuit, if any of these are even legal or doable in a home environment the first place. Why? Is it possible that Tesla's future home chargers could work at even faster charge rates (and thus higher amperage)? Overkill ?!!? Fire hazard ?!?

 

[Daniellane]

Thank you @Daniellane, @Rockster, and everyone else. I really like @Daniellane setup, and @Runt8 makes an excellent point.

The only other possible improvement I can think of is having two separate 100 amp circuits or even a combined 200 amp circuit, if any of these are even legal or doable in a home environment the first place. Why? Is it possible that Tesla's future home chargers could work at even faster charge rates (and thus higher amperage)? Overkill ?!!? Fire hazard ?!?

Not likely...
The 100 Amp setup is pretty great for two shared chargers.
The batteries are dc. There is an onboard charger that accepts AC current to a specific limit in Amps. It converts the AC to dc. All new Teslas are now 48 amps. (Possible off menu SX upgrades to 72)
Superchargers are much higher power, however they are DC. The onboard charger’s AC to DC conversation is bypassed, although it does contain the processor that manages the Supercharging process.
As far as I understand it the Master wall connector max is 80amps which requires a 100 amp circuit. Load max is 80% of breaker. Additional wall charger is set as slave.
From page 9 of wall connector install manual. Download the manual.

 

[Daniellane]

FYI
Installation Manuals - Wall Connector

 

[Antares Nebula]

So, technically, if all new Teslas are 48 amps (or one only has those models), then the rotary switch on the Wall connector need not be set greater than 48, correct?

 

[Antares Nebula]

Also to ask another follow up question @Daniellane, in your setup with the two wall connectors sharing a 100 amp breaker, if you have two model 3s charging simultaneously, that means the max draw on each wall connector at 80% is 40 amps each. Two questions:

So that means with such a setup, you're not getting max charge rate (48 amps) on BOTH vehicles at the same time. Is it then better to have at least a 120 amp breaker/circuit?

In your above setup, what exactly happens internally with the wall chargers? Do they end up tripping the breakers or do they know that only 80 amps can be drawn collectively. How do they know what the max draw on the external circuit is? (I'm not electrically inclined, so sorry if it's a stupid question.) Or do they limit themselves based on the rotary switch. For example, if you set the switch to 40 amps, then they don't trip the breaker. But if you set them both to 48 amps, they trip it. ??

Thanks!

 

[Daniellane]

So, technically, if all new Teslas are 48 amps (or one only has those models), then the rotary switch on the Wall connector need not be set greater than 48, correct?

If you only have one charger on a 60 amp circuit. Mine is set to 80. Splits 40 to each car if both are charging. I believe the circuit is the determining factor, not the car charger. The car sets the amps it will take dynamically and by location. So if you had a 40 amp circuit you’d set it to 32...

 

[Antares Nebula]

Well, maybe never mind, I think you guys answered it above. In the master/slave setup, with 80 amp max draw on the master, there is no tripping risk. I guess the upshot is that in such a setup, you cannot get max charging speeds on both wall connectors.

The only way to circumvent this is set them up independently on separate 60 amp circuits. The drawback here is that in case you buy one of the older higher amperage charging Tesla cars, since all the new ones are 48 amps. OR if in the future, perchance, Tesla comes out with higher amperage charging vehicles and wall chargers.

 

[davewill]

Since the subjet is future proofing, I don't think too much effort need be spent worrying about older cars with >48a charging, so two indendent 60a wall connectors would probably be preferable to the shared 100a circuit. However, the shared 100a isn't really much of a compromise, IMHO. After all, if both cars are charging at the same time, it's probably a standard overnight charge, in which case 40a is plenty. The situation where you'd care about that last 8a would be a daytime charge where you have a limited amount of time before needing to leave again. The chances of BOTH cars being in the same situation at the same time is low.

 

[eprosenx]

Since the subjet is future proofing, I don't think too much effort need be spent worrying about older cars with >48a charging, so two indendent 60a wall connectors would probably be preferable to the shared 100a circuit. However, the shared 100a isn't really much of a compromise, IMHO. After all, if both cars are charging at the same time, it's probably a standard overnight charge, in which case 40a is plenty. The situation where you'd care about that last 8a would be a daytime charge where you have a limited amount of time before needing to leave again. The chances of BOTH cars being in the same situation at the same time is low.

Yeah, I also would call out that in the long term there will be lots of EV vehicles on the market. You will likely have two different manufacturer vehicles some day. So either you will need to switch to some kind of J1772 load sharing system, or, end up with two separate circuits non load shared. For this reason, my plan is to run dedicated circuits to each vehicle (home run to a panel) even if I do implement some kind of load sharing to keep below a load calculations cap.

The reality is nearly nobody has 120a of available load capacity. Most don’t have 100a laying around even...

 

[Zaxxon]

The reality is nearly nobody has 120a of available load capacity. Most don’t have 100a laying around even...

This is the real advantage of the HPWC, IMO. You can take one 100A breaker/wiring run (or whatever is the most you can spare) and can power up to four parking spots with that power, with the cars sharing it intelligently.

Even when you do have capacity for independent runs, it's generally much cheaper to use one unless your panel is in the garage.