Energy Battery Storage and PV system directly on one Residential Main Panel?

[cern_EE]

Hi all, so I have this one massive Single Family project where the home is 3600 sq ft in LA County. Demand Amps were originally 173A, so we were going with a 200A service and a panel with a 200A bus rating. Solar (which is required for new Construction in CA) was allocated 9.6kW of continuous load while using the 120% rule. I recently received the following plan check comment:

For all new one and two-family dwelling units, the service panels and/or sub-panels shall have the capacity of an additional load not less than 5kVA for every 2,000 square feet of living space, designated to accommodate future energy storage system(s). This load shall be considered continuous and demand factors shall not apply. Additionally, the service panels and/or sub-panels shall have space(s) reserved/dedicated to permit installation of the branch circuit overcurrent protective device(s) for energy storage system. (LACEC 220.41).


It looks like LA county Incorporated requirements on having Energy Storage Systems (ESS) earlier than the state and the counties that I mostly complete projects in, which are on NEC 2017. With this new ESS demand at 125% this bumps my service size to 400A with a demand of 225A (10kW added). I updated the Bus ratings to 400A with a 225A main breaker.

My question is, with the main breaker being 225A and the bus rating being 400A, does this comply with NEC2017 705.12(B)(2)(3)(a) which would allow for the PV and ESS to be located on separate circuits, anywhere on the panel? I'd place them on the very last circuits on the panel, but I'm curious about others' thoughts.

If it doesn't comply, I would definitely appreciate feedback on other ways one may go about adding the "future" ESS loads to the system while still complying with NEC requirements. Thanks!

 

[jaggedben]

Yes, the PV and or ESS could go anywhere on the busbar. You'll probably have a 200A breaker to an MID I'm guessing (Tesla Gateway or something similar), but still the same answer.

I'm assuming here the max continuous output of both PV and ESS is roughly 75A based on what you said. You could go up to 175A with that.

One caveat: I don't see too many resi panels with an actual 400A busbar, though they do exist. You might do better go with a split 200/200 type meter main, and connect the MID to the top service disconnect position, using the 200A panelboard section for non backed up loads. That should still be allowed if the permit is issued before the end of this year.

 

[wwhitney]

Demand Amps were originally 173A, so we were going with a 200A service and a panel with a 200A bus rating. Solar (which is required for new Construction in CA) was allocated 9.6kW of continuous load while using the 120% rule.

Presumably you mean 7.68kW of PV inverter output, i.e. 7.68kW of continuous power? Which is 9.6kW after the 125% factor, and could use a 40A breaker and comply with the 120% rule.

One option to consider is a 200A meter/main breaker only (no distribution section), with a 200A feeder to a splice box. From the splice box you have a 200A feeder to a 200A main breaker distribution panel for the loads, and a 200A feeder (or smaller using the tap rules) to an OCPD for the PV inverter. That avoids the busbar interconnection limitations by using the feeder interconnection rules. And if ESS were ever installed, it would be added to the feeder segment to the PV, or, for something like the Tesla Powerwall, the splice box would replaced by their Gateway (MID), which has room for some generation breakers.

Cheers, Wayne

 

[jaggedben]

Presumably you mean 7.68kW of PV inverter output, i.e. 7.68kW of continuous power? Which is 9.6kW after the 125% factor, and could use a 40A breaker and comply with the 120% rule.

One option to consider is a 200A meter/main breaker only (no distribution section), with a 200A feeder to a splice box. From the splice box you have a 200A feeder to a 200A main breaker distribution panel for the loads, and a 200A feeder (or smaller using the tap rules) to an OCPD for the PV inverter. That avoids the busbar interconnection limitations by using the feeder interconnection rules. And if ESS were ever installed, it would be added to the feeder segment to the PV, or, for something like the Tesla Powerwall, the splice box would replaced by their Gateway (MID), which has room for some generation breakers.

Cheers, Wayne

If I understand correctly, he is saying that when the possible future ESS is included as a load (presumably for grid charging), he needs a 225A service.

 

[wwhitney]

If I understand correctly, he is saying that when the possible future ESS is included as a load (presumably for grid charging), he needs a 225A service.

Good point. But my comments still apply, the install could be done with a 225A service (if that's a thing) and panels, no need to go to a 400A busbar.

Also, not familiar with the LA regulation, but does it really require you to include the 10 kVA ESS system as a load? Since the idea of the ESS would be to reduce grid dependency or for load smoothing, that seems backwards. Seems like the could require installing it as a PCS, or at least allow it, so that the load on the service would not be increased.

Cheers, Wayne

 

[jaggedben]

Good point. But my comments still apply, the install could be done with a 225A service (if that's a thing) and panels, no need to go to a 400A busbar.

Not really a thing. Most likely you'd be putting a 225A OCPD in a 400A piece of equipment and if I recall correctly LADWP is one of those jurisdictions that requires the service conductors to match the equipment rating instead of the overcurrent device. So if you have to pay for a 400A service, you might want to actually get one.

Also, not familiar with the LA regulation, but does it really require you to include the 10 kVA ESS system as a load? Since the idea of the ESS would be to reduce grid dependency or for load smoothing, that seems backwards. Seems like the could require installing it as a PCS, or at least allow it, so that the load on the service would not be increased.

Cheers, Wayne

Yeah, seems to me what he quoted only requires 5KW. OTOH, if the user can still change settings to make the batteries charge from the grid, and any future ESS is likely to be more than 5KW...