Adding EV charging circuits, what is code?

[h2ofun]

I continue to want to add some EV charging circuits to my garage, BUT, trying to find out if what I want to do can even be coded. If not, need to change direction.

I have a 400 amp feed, 200amp per subpanel setups.

One 200amp feed goes into my garage subpanel. It has my 4 heat pump compressors on a 100amp breaker. Has 15Kw of solar in a generation panel with 3 powerwalls. It also has like 5 20 general purpose circuits for the garage. One 240 for my air compressor.

What I wanted to do is tap off this feed with another 200 amp subpanel into my garage. There ideally I would love to have up to 5 with 60 amp breakers to feed tesla chargers.

BUT, as I think about this, what is code for what they will allow? Meaning, I am dumb enough assuming that if anything were to pull more than a total of 200 amps, the breaker would blow. Meaning, all the wiring subpanels, etc could never exceed their specs. But, I could make the breaker blow, technically, if I wanted to turn everything on.

Now, if the above is not able to be coded, meaning I could add no extra circuits to this feed, then I am thinking what are my other choices?

Currently I have 2 SE 11.4K inverters in the garage on 60 amp circuits? SE does have this kit, which I assume allows one to add, and I assume can charge even with the inverter off at night? But could one also just tap these lines with a 14-50 connection so I could use telsa chargers?

https://www.solaredge.com/sites/default/files/single_phase_inverter_integrated_ev_charger_SetApp_na.pdf

Or what other ideas do folks have that I can get a permit for.

So far I have not found a person who really knows this stuff to give me the best direction to go.

But this group, with all the experts, I hope can lead me the right way.

 

[wwhitney]

One 200amp feed goes into my garage subpanel. It has my 4 heat pump compressors on a 100amp breaker. Has 15Kw of solar in a generation panel with 3 powerwalls. It also has like 5 20 general purpose circuits for the garage. One 240 for my air compressor.

What I wanted to do is tap off this feed with another 200 amp subpanel into my garage. There ideally I would love to have up to 5 with 60 amp breakers to feed tesla chargers.

So, it goes like this:

The calculated load on your 200A garage subpanel needs to be no more than 200A. You need the load information for all the equipment supplied by the panel.

For the heat pump compressors, that info should be on a nameplate on each compressor, most important will be MCA (Minimum Circuit Ampacity) and MOCP (Maximum Overcurrent Protection). Additional information on the nameplate would let you make a sharper computation since you have multiple units.

For the air compressor, you need the nameplate current draw. Also for any other fixed equipment, like a garage door opener. For the general purpose circuits, I think those and the lighting circuits are just figured at 3 VA / sq ft for the area served. (That's the rule for a dwelling unit, and I think it would extend to the garage, not 100% sure.)

Then roughly you add that all up and say you get a figure like 100A. That leaves you 100A of headroom, would would be enough for (2) 50A circuits for 40A continuous EVSEs. Or you could get system where the EVSEs could talk to each other and be configured never to draw more than 80A at once, that would let you have more than 2.

Anyway, if you gather all the data, it's not that hard to do the computation. You'd want to know literally everything that each breaker in the garage subpanel supplies, everything that is plugged in or connected that dies when you turn off the breaker.

Cheers, Wayne

P.S. The other way to get a number for the existing load, to determine what headroom you have for EVSEs, is to actually measure it with a meter that records the power usage over each 15 minute interval for 30 days, see NEC 220.87.

 

[h2ofun]

So, it goes like this:

The calculated load on your 200A garage subpanel needs to be no more than 200A. You need the load information for all the equipment supplied by the panel.

For the heat pump compressors, that info should be on a nameplate on each compressor, most important will be MCA (Minimum Circuit Ampacity) and MOCP (Maximum Overcurrent Protection). Additional information on the nameplate would let you make a sharper computation since you have multiple units.

For the air compressor, you need the nameplate current draw. Also for any other fixed equipment, like a garage door opener. For the general purpose circuits, I think those and the lighting circuits are just figured at 3 VA / sq ft for the area served. (That's the rule for a dwelling unit, and I think it would extend to the garage, not 100% sure.)

Then roughly you add that all up and say you get a figure like 100A. That leaves you 100A of headroom, would would be enough for (2) 50A circuits for 40A continuous EVSEs. Or you could get system where the EVSEs could talk to each other and be configured never to draw more than 80A at once, that would let you have more than 2.

Anyway, if you gather all the data, it's not that hard to do the computation. You'd want to know literally everything that each breaker in the garage subpanel supplies, everything that is plugged in or connected that dies when you turn off the breaker.

Cheers, Wayne

P.S. The other way to get a number for the existing load, to determine what headroom you have for EVSEs, is to actually measure it with a meter that records the power usage over each 15 minute interval for 30 days, see NEC 220.87.

Interesting. Since my 20 amp circuits only have lights and garage doors which do not get used much. Air compressor hardly ever gets turned on.
And the mini splits on the 100 amp line are off for at least 6 months of the year, seems talking measure would need to be done? What kind of meter?
And seems would want to measure during the 6 months mini splits off? And since I have no EV car now, nothing there either. So, if you were me, how would you go after this?

 

[jjrandorin]

So, if you were me, how would you go after this?

I doubt you will ever end up with an entire garage full of EVs to charge, but to answer that question, in your case I would get Load sharing wall connectors (J1772 to not be tied to any specific brand) and share a 60amp circuit for 2, or 2 60 amp circuits for 4 if the load calculation allows.

Something like this:

Grizzl-E Duo – GRIZZL-E

 

[h2ofun]

I doubt you will ever end up with an entire garage full of EVs to charge, but to answer that question, in your case I would get Load sharing wall connectors (J1772 to not be tied to any specific brand) and share a 60amp circuit for 2, or 2 60 amp circuits for 4 if the load calculation allows.

Something like this:

Grizzl-E Duo – GRIZZL-E

Pretty cool. Yes, for the cost of permits, labor I just want to push it to the limit even though would never be used.

The Tesla gen 2 can load share up to 4 charges now I believe, and could expand to more.

This is why I need a real real smart person who knows how to make this stuff work. Anyone know such a person like this out of Sacramento Northern Calif. Seems it could be a great project for someones resume

 

[jjrandorin]

Pretty cool. Yes, for the cost of permits, labor I just want to push it to the limit even though would never be used.

The Tesla gen 2 can load share up to 4 charges now I believe, and could expand to more.

This is why I need a real real smart person who knows how to make this stuff work. Anyone know such a person like this out of Sacramento Northern Calif. Seems it could be a great project for someones resume

Tesla gen 2 wall connectors can share up to 4 chargers off one circuit, in a load sharing capacity. It only needs one breaker to do so, and load sharing is done via a communications cable (as in hard wired) between the units. More than 4 require an additional ciruit / (breaker).

Tesla gen 3 wall connectors can do load sharing as well, but the setup for those is supposed to be 1 breaker per wall connector, and load sharing communication is done via wifi. I think you can share more than 4, but since the tesla installation manual calls for 1 breaker per wall connector, that kind of doesnt matter to me how many they can share.

Tesla gen 2 wall connectors are only available through ebay / craigslist etc and in general, people sitting on those now are in a "I know what I got" mode, especially if they are "new old stock" in box, so tesla gen 2 wall connectors cost more than they did when new, in most cases, if you can find one.


I only know all this detail right now about these because I am getting a second tesla, and wanted load sharing on the Gen 2 wall connector I have setup.

"Push to the limit" would be installing 4 gen 2 wall connectors on 100amp circuit in load sharing capacity. Unless you are planning to open a restaurant or something, even if you had 4 EVs on such a circuit, and they were charging all at the same time, it would be 20amps per EV which would still likely be enough to charge all 4 overnight.

With load sharing, when one finishes, the power then gets split "1 fewer". Installing 4 wall connectors on (1) 100 amp circuit in a load sharing configuration is a "max it out / I will never use that" situation.

 

[h2ofun]

Tesla gen 2 wall connectors can share up to 4 chargers off one circuit, in a load sharing capacity. It only needs one breaker to do so, and load sharing is done via a communications cable (as in hard wired) between the units. More than 4 require an additional ciruit / (breaker).

Tesla gen 3 wall connectors can do load sharing as well, but the setup for those is supposed to be 1 breaker per wall connector, and load sharing communication is done via wifi. I think you can share more than 4, but since the tesla installation manual calls for 1 breaker per wall connector, that kind of doesnt matter to me how many they can share.

Tesla gen 2 wall connectors are only available through ebay / craigslist etc and in general, people sitting on those now are in a "I know what I got" mode, especially if they are "new old stock" in box, so tesla gen 2 wall connectors cost more than they did when new, in most cases, if you can find one.


I only know all this detail right now about these because I am getting a second tesla, and wanted load sharing on the Gen 2 wall connector I have setup.

"Push to the limit" would be installing 4 gen 2 wall connectors on 100amp circuit in load sharing capacity. Unless you are planning to open a restaurant or something, even if you had 4 EVs on such a circuit, and they were charging all at the same time, it would be 20amps per EV which would still likely be enough to charge all 4 overnight.

With load sharing, when one finishes, the power then gets split "1 fewer". Installing 4 wall connectors on (1) 100 amp circuit in a load sharing configuration is a "max it out / I will never use that" situation.

I met using gen 3 charges. My mistake. I hear the fw works with them sharing now for 4, but could be expanded. I just want to put as my lines in that I can get permitted so I could put whatever type if any down the road. Trying to do max flexibility, just like I now have installed basically as many solar panels as my roof would hold.

 

[ATPMSD]

You have a lot going on so I suggest you spend some money and hire an electrician to explore your options. As to multiple Wall Connectors, as noted the Gen 3 Wall Connector has WiFi power sharing so it you have capacity for one you can install four and enable load sharing.

 

[h2ofun]

You have a lot going on so I suggest you spend some money and hire an electrician to explore your options. As to multiple Wall Connectors, as noted the Gen 3 Wall Connector has WiFi power sharing so it you have capacity for one you can install four and enable load sharing.

I continue to try and find one to hire who wants the job. So far, no luck

 

[ATPMSD]

I continue to try and find one to hire who wants the job. So far, no luck

Wow!

 

[jjrandorin]

Wow!

Part of the challenge with this is, once someone has "Solar + battery storage" (or in @h2ofun 's case solar + battery storage + generator), when / if you want to add "anything else" electrical, it becomes a challenge, especially if you want it on the backup loads side.

A "regular" electrician is not interested in touching ANYTHING on the backup loads side (ignoring for a moment that installations with powerwalls usually end up with large red stickers that say " DO NOT ADD LOADS " to the backup loads panel). Depending on your setup, you might be able to get a regular electrician to "touch" something in the main panel if its not backed up.

If Tesla itself is the installer of the PV+ storage (not the case in @h2ofun 's installation), they are usually not interested in sending an electrician out to do any "additions", like installing wall connectors, or circuits for hottubs, or anything else. If the installer is a third party, one could contact them but they also may be "not interested" in doing any additions to loads on a system, especially on the backup loads side.

This is why, when people ask "should I add this load now, or can I add it after install?" I always say " do it now, because doing it "later" is going to either be "kinda hard" or "mostly impossible", depending on your home setup. In no cases is it "easy" unless you are doing the work yourself and know how to do it.

 

[ATPMSD]

on the backup loads side

Why are you looking to put it there? I would have thought the interconnects control where solar power goes (house, battery or utility) and where house power comes from (solar, battery or utility). So anything you want to do on the ”house” side of the system seems like fair game? Think of this as adding a circuit for an outlet in the house. Your new circuit is just 240V @ 60Amps.

This does not seem like anything unusual for an electrician. But hey, I do not have solar so what do I know?

 

[jjrandorin]

Why are you looking to put it there? I would have thought the interconnects control where solar power goes (house, battery or utility) and where house power comes from (solar, battery or utility). So anything you want to do on the ”house” side of the system seems like fair game? Think of this as adding a circuit for an outlet in the house. Your new circuit is just 240V @ 60Amps.

This does not seem like anything unusual for an electrician. But hey, I do not have solar so what do I know?

There are a few different reasons one may want to add a load to the backup loads side, but that isnt this thread.

For the rest, I posted what actual experience is, when attempting to do this, in post #11 in this thread, which will be corroborated by pretty much anyone else here who has attempted to get any circuit added after the fact, to the backup loads side of an existing PV + ESS install. Additionally, A particular install may not have a "non backed up loads" side, depending on how it was configured.

 

[h2ofun]

Part of the challenge with this is, once someone has "Solar + battery storage" (or in @h2ofun 's case solar + battery storage + generator), when / if you want to add "anything else" electrical, it becomes a challenge, especially if you want it on the backup loads side.

A "regular" electrician is not interested in touching ANYTHING on the backup loads side (ignoring for a moment that installations with powerwalls usually end up with large red stickers that say " DO NOT ADD LOADS " to the backup loads panel). Depending on your setup, you might be able to get a regular electrician to "touch" something in the main panel if its not backed up.

If Tesla itself is the installer of the PV+ storage (not the case in @h2ofun 's installation), they are usually not interested in sending an electrician out to do any "additions", like installing wall connectors, or circuits for hottubs, or anything else. If the installer is a third party, one could contact them but they also may be "not interested" in doing any additions to loads on a system, especially on the backup loads side.

This is why, when people ask "should I add this load now, or can I add it after install?" I always say " do it now, because doing it "later" is going to either be "kinda hard" or "mostly impossible", depending on your home setup. In no cases is it "easy" unless you are doing the work yourself and know how to do it.

Yep, I blew it

 

[slcasner]

Part of the challenge with this is, once someone has "Solar + battery storage", when / if you want to add "anything else" electrical, it becomes a challenge, especially if you want it on the backup loads side.

A "regular" electrician is not interested in touching ANYTHING on the backup loads side (ignoring for a moment that installations with powerwalls usually end up with large red stickers that say " DO NOT ADD LOADS " to the backup loads panel).

I knew this would be my situation as I wanted to restore a 50A cooktop circuit that had been disconnected in a previous remodel and add a 30A circuit to allow installation of a heat-pump water heater. My solution was to file a separate permit application in parallel with Tesla's that included new load calculations justifying the additional circuits, then I did the work myself -- extending the cooktop circuit (which involved some tricky fishing the cable down a wall cavity from attic to crawl space that an electrician probably wouldn't be willing to take the time to do) and installing the new HPWH circuit while the roof was off. Tesla's electricians were nice enough to leave my new cables ready and capped off in the new backup panel, then I installed my new breakers before the red sticker was applied. I'm still waiting for inspection on Tesla's permit (another long story) and I will try to schedule mine at the same time.