PG&E \ Off-Grid System Design

[TheHappyNomads]

I'm trying to finalize documents to submit for a permit in my city (Hayward, CA) but am trying to figure out what exactly I need to include when it comes to disconnects and stuff. I am NOT interested in a grid-tie system but simply want to reduce my grid consumption by eliminating EV charger and electric dryer from my main service panel. On the example diagrams they're asking for A/C disconnects between the inverter and main service panel but I wouldn't need that correct? I don't want to include unnecessary elements in the design to reduce complexity.

Here's my plan:

(8) 415w panels feeding (2) LV6548s feeding a ~30kwh battery bank (we are putting an addition on our house and so I will have room in the future to add more panels if desired)

All of this will feed an AC Load Center from/to which I will run service to my EV Charger and dryer receptacle.

I am planning on running a breaker from my main service panel to the 6548s so that during low PV production days I can recharge batteries overnight if desired.

Since I will not be feeding the grid at all I am assuming PG&E doesn't need to be notified or involved in the process and the permitting process will cover all my bases, correct? I looked around on the PG&E website but couldn't find any information so anyone with any experience \ knowledge would be great if I am not taking something into consideration.

Here's what I've got so far. Still need to get around to the single line diagram. Not going to include the wiring from the AC Load Center to the EV Charger or Dryer Receptacle.

 

[hwy17]

I think they will consider this an interconnected non exporting system. The inverter is still interacting with the grid if you connect it to AC.

 

[400bird]

I am planning on running a breaker from my main service panel to the 6548s so that during low PV production days I can recharge batteries overnight if desired.

This line right here makes it grid tied.

Why recharge from the grid? That will cost you something like 20% more energy due to inefficiency. Why not just switch those two loads over to the grid when the battery runs low?

Since I will not be feeding the grid at all I am assuming PG&E doesn't need to be notified or involved in the process and the permitting process will cover all my bases, correct? I looked around on the PG&E website but couldn't find any information so anyone with any experience \ knowledge would be great if I am not taking something into consideration.

It's grid tied, you'll need to involve PGE. Well, need it PGE's opinion, should is more accurate.

Here's what I've got so far. Still need to get around to the single line diagram. Not going to include the wiring from the AC Load Center to the EV Charger or Dryer Receptacle.

 

[EricBarbour]

Very vague drawing. You are aiming for a totally "off grid" system, yes? Usually people install a transfer switch so they can run various circuits from utility power OR the solar/inverter/battery. And you can easily get manual transfer switches with up to 10 circuits so you can run parts of the house on utility and other parts on solar, selectable as desired. They have generator inlet sockets to install on an outside wall, letting you plug in either the solar inverter or a generator. Installed by an electrician which is recommended--it has to be installed near and wired directly into the breaker panel, and there is a lot of wiring. Transfer switches usually include separate breakers on each circuit and wattmeters on each side of the 240v split-phase service. No, you do not have to deal with PG&E, because this setup does not backfeed to the grid and is on the HOUSE side of the breaker panel. It's between you and the electrician (and local government if they require a permit).

Connecticut Electric Emergen 50 Amp 10-Circuits G2 Manual Transfer Switch EGS1012KG2 - The Home Depot

The Connecticut Electric G2 series generator transfer switch features a 50A, 10-circuit manual transfer switch that eliminates the possibility of power back feeding into the utility line or generator when power is restored. This transfer switch comes with detailed instructions to help with the...

www.homedepot.com

Reliance Controls 10-Circuit 30 Amp Manual Transfer Switch Kit 310CRK - The Home Depot

This 10-circuit, 30 Amp manual transfer switch kit includes everything needed to make a professional transfer switch installation in a home, office, or small business. It is completely pre-wired and designed

www.homedepot.com

Generac sells automatic transfer switches, but they are usually a single switch to feed the whole house, and are meant to work with an outdoor pad-mounted generator.

 

[EricBarbour]

This line right here makes it grid tied.

No it doesn't. This is merely a circuit feeding power FROM the utility to the battery charger in the inverter.

It's grid tied, you'll need to involve PGE. Well, need it PGE's opinion, should is more accurate.

No. "Grid tied" means the system is directly connected to the utility grid and can feed power back into the grid. That's NOT what this person is trying to do.

 

[400bird]

I didn't look at the drawing the first time through. I don't think a rooftop PV disconnect is needed or meets code for the required firefighter disconnect.

 

[hogback]

I don't think one needs to tell pge that they plug in a battery charger and charge batteries.

 

[hwy17]

No it doesn't. This is merely a circuit feeding power FROM the utility to the battery charger in the inverter.

AIO's don't have a separate charger inside, the AC input interconnects the inverter.

 

[onokai]

I thnk you have it right in terms of a non grid tied system and PG&E is out of that loop. I am wonding about the 8 415V panels feeding 30 KW of power . I am feeding 24 400w panesl to a 22.5 Kw battery bank and in winter we need all of them. We are 5 hours north of your location just north of Eureka which is miore cloudy amnd more rain for sure.

 

[400bird]

I don't think one needs to tell pge that they plug in a battery charger and charge batteries.

It isn't just a battery charger.

 

[hogback]

It isn't just a battery charger.

Isn't that all it's doing in terms of a pge interaction? I'm not familiar with the proposed equipment, I must admit.

 

[TheHappyNomads]

This line right here makes it grid tied.

Why recharge from the grid? That will cost you something like 20% more energy due to inefficiency. Why not just switch those two loads over to the grid when the battery runs low?

It's grid tied, you'll need to involve PGE. Well, need it PGE's opinion, should is more accurate.

That's actually the goal in my mind. I didn't know of another way to do this until now = manual transfer switch.

 

[TheHappyNomads]

Very vague drawing. You are aiming for a totally "off grid" system, yes? Usually people install a transfer switch so they can run various circuits from utility power OR the solar/inverter/battery. And you can easily get manual transfer switches with up to 10 circuits so you can run parts of the house on utility and other parts on solar, selectable as desired. They have generator inlet sockets to install on an outside wall, letting you plug in either the solar inverter or a generator. Installed by an electrician which is recommended--it has to be installed near and wired directly into the breaker panel, and there is a lot of wiring. Transfer switches usually include separate breakers on each circuit and wattmeters on each side of the 240v split-phase service. No, you do not have to deal with PG&E, because this setup does not backfeed to the grid and is on the HOUSE side of the breaker panel. It's between you and the electrician (and local government if they require a permit).

Connecticut Electric Emergen 50 Amp 10-Circuits G2 Manual Transfer Switch EGS1012KG2 - The Home Depot

The Connecticut Electric G2 series generator transfer switch features a 50A, 10-circuit manual transfer switch that eliminates the possibility of power back feeding into the utility line or generator when power is restored. This transfer switch comes with detailed instructions to help with the...

www.homedepot.com

Reliance Controls 10-Circuit 30 Amp Manual Transfer Switch Kit 310CRK - The Home Depot

This 10-circuit, 30 Amp manual transfer switch kit includes everything needed to make a professional transfer switch installation in a home, office, or small business. It is completely pre-wired and designed

www.homedepot.com

Generac sells automatic transfer switches, but they are usually a single switch to feed the whole house, and are meant to work with an outdoor pad-mounted generator.

Yes, vague drawing because this particular drawing just has to show configuration of elements. I also have to include a single line drawing of all the electrical in the PV system.

Thanks for the heads up on the manual transfer switch, I was unfamiliar with those and they seem like the solution for my situation. I'll check out the options you linked.

 

[TheHappyNomads]

I didn't look at the drawing the first time through. I don't think a rooftop PV disconnect is needed or meets code for the required firefighter disconnect.

In my jurisdiction it is and meets code unless I have RSS installed.

" IF ANOTHER MEANS OF RAPID SHUTDOWN IS NOT PRESENT, PROVIDE A ROOFTOP DC DISCONNECT * @ ROOF WITHIN 3’ OF PV ARRAY ALONG ACCESS PATHWAY PER HAYWARD FIRE ORDINANCE."

 

[TheHappyNomads]

AIO's don't have a separate charger inside, the AC input interconnects the inverter.

So what you're saying is that because of this there is potential for the inverter to actually backfeed the grid which makes it connected. Is that right?

 

[TheHappyNomads]

I thnk you have it right in terms of a non grid tied system and PG&E is out of that loop. I am wonding about the 8 415V panels feeding 30 KW of power . I am feeding 24 400w panesl to a 22.5 Kw battery bank and in winter we need all of them. We are 5 hours north of your location just north of Eureka which is miore cloudy amnd more rain for sure.

I admit it's not ideal but at the moment that's all the rooftop space I have available to me and those are the panels I've got. I'm under no expectation that I will be able to recharge the full battery bank each day until I am able to find a way to connect more panels into my system.

The battery bank is oversized because I got a helluva deal on some retired EV battery modules and didn't want to pass up on the opportunity. Figured I would oversize ESS and then install PV production to match eventually.

 

[hwy17]

So what you're saying is that because of this there is potential for the inverter to actually backfeed the grid which makes it connected. Is that right?

Yes, the inverter is interacting on it's AC side.

And even if you used a chargeverter, I think you'd have a very uphill battle trying to get the building department to understand it as a non interconnected system. They just aren't used to the concept at all.

 

[zanydroid]

I don't think one needs to tell pge that they plug in a battery charger and charge batteries.

PG&E rule21 does require commercial/industrial customers to notify them of this. Because of the change in usage pattern that needs to be accounted for in capacity planning.

In theory (IE there is a policy PDF covering this).

In practice I do not know if it is enforced.

 

[zanydroid]

I am planning on running a breaker from my main service panel to the 6548s so that during low PV production days I can recharge batteries overnight if desired.

Where is the discussion of UL9540 compliance to pass AHJ inspection? I don’t know of a AHJ in California that would not enforce it

EDIT: did you verify if the exemption for recycled EV modules is still in effect?

 

[zanydroid]

So what you're saying is that because of this there is potential for the inverter to actually backfeed the grid which makes it connected. Is that right?

If programmed incorrectly. There were some recent reports of POCO in other parts of the US sending nastygrams after detecting a few W of backfeed from AIOs that in principle should have been programmed and interlocked to prevent the combined charger/inverter from doing something bad

With a chargeverter there is no ambiguity as to whether it’s a firmware bug in the AIO or a measurement bug at the POCO. Since the chargeverter is charge only.