Where to connect grid tied solar - Generator, 2 ATS, and 2 Inverters

[DanS26]

Multiple branch circuits to a detached structure are not allowed per NEC 225.30. But there are exceptions....see NEC 225.30 (A) (5) Parallel power production systems. Check with your AHJ before you start digging.

[oregon_phil]

Each inverter should have a 40amp breaker per SE manual.

Regarding voltage rise, I have 6 ft from my string inverter to meter breaker panel with a 1.5VAC voltage rise. My POCO stepdown transformer is 50 feet from my meter breaker panel. Remember I'm not a sparky.

[Mr. Inquisitive]

After doing a bit of searching, a 70A combiner with two breakers is fairly cheap. Since the inverters are 32A max continuous output, that should work and then I could tie into the MSP on a 70A breaker. I would of course have an AC disconnect at the combiner as well. I would derate the garage panel to ~120A.

Does that sound like a good way to do this?

[Mr. Inquisitive]

Dan, I am thinking the original owner had intended to expand. The capacities of the panels are overkill as well.

Phil, thanks for that. I will do some searching on the two inverters.

[DanS26]

OP...there is a lot going on which is questionable before you even think about a solar install....two ATS for a little 11kW Generac is a red flag......

[oregon_phil]

I will need to read up on how inverters would interact with each other. There seems to be some knowledge I am missing on how they detect each other and how that interaction would change by having them connected on different panels. It is not like there is a rectifier in between them by going to a different panel.

I do get derating the garage panel if I am not using it to connect the inverters. Thankfully it is WAY oversized for its current use. I think the original owner was building it out to be a massive workshop. It could handle its current load and any foreseeable load if derated to 100A.

Here are the other pictures I promised ...
main panel3.jpggarage subpanel (2).jpghouse subpanel.jpg

And for those that are bearing with my ignorance, I appreciate your giving me the opportunity to interact and learn.

I wasn't really concerned about interaction but how two inverters are supposed to be legally connected together. If you search this forum for two inverters connected together you'll see some are required to use a combiner box then to the breaker panel with various AC shutoffs. Also measure your line voltage and research inverter voltage rise issues for long runs like the one you are proposing.


And standard disclaimers to my abilities were previously stated.

[J.P.M.]

I see Oregon Phil listed his profession so the OP could have an idea about his skill set. How about the rest of you just handymen putzing with electrician stuff?
Myself 38 years feeding my family as a journeyman electrician, you might have noticed I didn't offer advice, to many unknows in a forum post.

Mike: You get what you pay for around here. Since all advice/comment is free and access or ability to post is not strictly controlled nor vetted, it all adds up to not much, or at least not much you can take to the bank.
It's like the wild west with respect to who posts what and what folks do with the information. Those who don't know that or don't figure it out and take all the unvetted stuff flying around here as gospel are naive.
No accuracy or correctness of information is expressed, implied or guaranteed.
Some posters are more knowledgeable than others and quite professional. Some other posters think they're knowledgeable and helpful but are really delusional with respect to their knowledge and abilities - with some of the crap they post being dangerous. We've all seen examples and do what we can - but no promises.

As a practical matter, see item 12 under terms of use. No warranties or guarantees about the accuracy of any information. That's just the way it is.

[Mr. Inquisitive]

I read this to say you would run an additional set of AC lines for the inverters.

Questions to help you figure out the details:

1) How do you combine two inverters at the garage?
2) Two 7.7 inverters is 80 amps worth of breakers at the meter breaker panel. You have a 200 amp service disconnect at the meter base for the garage unit. What does the service disconnect need to be decreased to in order to fulfill the 120% rule? Does this set up still work?

I will need to read up on how inverters would interact with each other. There seems to be some knowledge I am missing on how they detect each other and how that interaction would change by having them connected on different panels. It is not like there is a rectifier in between them by going to a different panel.

I do get derating the garage panel if I am not using it to connect the inverters. Thankfully it is WAY oversized for its current use. I think the original owner was building it out to be a massive workshop. It could handle its current load and any foreseeable load if derated to 100A.

Here are the other pictures I promised ...
main panel3.jpggarage subpanel (2).jpghouse subpanel.jpg

And for those that are bearing with my ignorance, I appreciate your giving me the opportunity to interact and learn.

[Mr. Inquisitive]

I see Oregon Phil listed his profession so the OP could have an idea about his skill set. How about the rest of you just handymen putzing with electrician stuff?
Myself 38 years feeding my family as a journeyman electrician, you might have noticed I didn't offer advice, to many unknows in a forum post.

Mike, I can appreciate your cynicism as it is indeed difficult to provide a solution without knowing all of the information. That being said, it is super helpful to have people making suggestions and also about things to look for.

As for myself, I am not an electrician. I am a certified electronic tech that has done component level troubleshooting for years and then went into IT. However, I have been involved in installing large power installations in data centers (everything from diesel generators, to running whips), installed an 11.4k PV system on my home (the inspector was quite complimentary of my work), and have performed quite a bit of residential wiring over the years. That being said ... I do not at all feel qualified to design this layout, but feel I have the capacity to learn.

So the point of this response is basically ... If you don't see enough information to be able to help give pointers, ask. By being silent, it doesn't help.

[DanS26]

I see Oregon Phil listed his profession so the OP could have an idea about his skill set. How about the rest of you just handymen putzing with electrician stuff?
Myself 38 years feeding my family as a journeyman electrician, you might have noticed I didn't offer advice, to many unknows in a forum post.

Mike, there are parts of the country that the NEC is just a suggestion. No inspections, no nothing.....if your house burns down that is your problem.

[Mike 134]

I see Oregon Phil listed his profession so the OP could have an idea about his skill set. How about the rest of you just handymen putzing with electrician stuff?
Myself 38 years feeding my family as a journeyman electrician, you might have noticed I didn't offer advice, to many unknows in a forum post.

[DanS26]

The new and additional garage main breaker will have to be derated to 150 amps. Two 40 amp breakers installed at the bottom of the garage panel accepting load from each inverter. Make sure AHJ is OK with this since some jurisdictions require a blade disconnect instead of breakers. Remember this new garage panel cannot interact with the existing garage panel.

IMO I would not go this route.....instead run 5 wires of high voltage DC to inverters at the 400 amp load center 300ft away.

[oregon_phil]

I will have to give this some thought. It is 2 inverters so I think I would need to run 2 sets of DC vs 1 set of AC if I put the inverters at the garage. I don't intend to go over 14kW total in the long term so this should be doable on a single AC run.

I read this to say you would run an additional set of AC lines for the inverters.

Questions to help you figure out the details:

1) How do you combine two inverters at the garage?
2) Two 7.7 inverters is 80 amps worth of breakers at the meter breaker panel. You have a 200 amp service disconnect at the meter base for the garage unit. What does the service disconnect need to be decreased to in order to fulfill the 120% rule? Does this set up still work?

[oregon_phil]

I am not sure if this is the case. The main panel is a 400A panel. The inverters are 7.6kW inverters. would that really exceed 120%? Or am I misunderstanding what you are saying?

To clarify, the meter base is connected to the house 200 amp service disconnect and garage 200 amp service disconnect. The garage 200amp service disconnect is connected to 30 space/40 circuit breaker panel with 200 amp buss bars (assumed, doesn't specifically say). You can connect one inverter to buss bars. But there might be other ways to do what you want. Best talk to an electrician.

[DanS26]

I will have to give this some thought. It is 2 inverters so I think I would need to run 2 sets of DC vs 1 set of AC if I put the inverters at the garage. I don't intend to go over 14kW total in the long term so this should be doable on a single AC run.

Yes....4 wires of large diameter of aluminum or 4 wires of slightly smaller copper for AC vs 5 wires of smaller diameter copper for DC. Voltage loss caclculation will be very important.