So, I’m tryna plan out systems for two different structures, which ultimately I’d like to tie together. Each structure presently has a separate service entrance and utility account; they are about 165 feet apart and not tied together in any way. (Btw this is rural, with no building codes).
Each solar system would have its own inverter(s), batteries and PV. But for several reasons, I’d like them to share Solar and battery resources with each other, and do away with one of the utility services. One reason is that the buildings are occupied and used differently; sometimes one of them uses a lot of power over a few days, then is dormant for a week or two. So taking care of those variable demands can be evened out if both systems can be tied together and shared. Another reason is that we’d like to get rid of one of those utility accounts (they now tack on a $30/month “service fee” per account), but we don’t want to go fully off grid.
So please comment if you see any problems with this plan: The structure where utility service will remain would have a larger system: more batteries, more PV, and two inverters in parallel. That system would tie to the grid (but not export; the utility grid would be only for augmenting to handle peak loads in excess of solar system capacity or when the sun doesn’t shine for several days).
The parallel inverters each have 200-amp pass-through, and would feed the main panel for that structure. Off that main panel, we would run an underground feeder cable to the second structure, where it would run into the grid lugs of the inverter there. That inverter would feed the main panel of the second structure.
In essence, the two parallel inverters would form a sort of mini-grid feeding the solo inverter and providing their excess capacity when needed, and the solo inverter could become AC-coupled power to the two-inverter structure when needed.
I clearly would need to set the frequency-shift of the parallel grid-connected inverters so that they wouldn’t export to the utility grid, but haven’t completely thought through how to manage the solo inverter so that it doesn’t “export” all of its power to the upstream inverters unless necessary.
Anyway, I can’t find anything wrong with this plan. Which of course means I’ve overlooked something. Any thoughts?
One thing I’m really not sure about is grounding. Can I get by with triplex URD cable between the structures, and rely on ground rods for grounding at the downstream structure? Or is it better to run four-plex with a continuous ground between the buildings? Probably will bury 3 feet deep anyway, but I’m thinking it would be safer to have a ground in the trench.
Also, I suppose I’ll need to un-bond the ground and neutral at the downstream structure, since it no longer would be the “main” panel of the system. Is this correct?
Thoughts and advice are greatly appreciated.
Each solar system would have its own inverter(s), batteries and PV. But for several reasons, I’d like them to share Solar and battery resources with each other, and do away with one of the utility services. One reason is that the buildings are occupied and used differently; sometimes one of them uses a lot of power over a few days, then is dormant for a week or two. So taking care of those variable demands can be evened out if both systems can be tied together and shared. Another reason is that we’d like to get rid of one of those utility accounts (they now tack on a $30/month “service fee” per account), but we don’t want to go fully off grid.
So please comment if you see any problems with this plan: The structure where utility service will remain would have a larger system: more batteries, more PV, and two inverters in parallel. That system would tie to the grid (but not export; the utility grid would be only for augmenting to handle peak loads in excess of solar system capacity or when the sun doesn’t shine for several days).
The parallel inverters each have 200-amp pass-through, and would feed the main panel for that structure. Off that main panel, we would run an underground feeder cable to the second structure, where it would run into the grid lugs of the inverter there. That inverter would feed the main panel of the second structure.
In essence, the two parallel inverters would form a sort of mini-grid feeding the solo inverter and providing their excess capacity when needed, and the solo inverter could become AC-coupled power to the two-inverter structure when needed.
I clearly would need to set the frequency-shift of the parallel grid-connected inverters so that they wouldn’t export to the utility grid, but haven’t completely thought through how to manage the solo inverter so that it doesn’t “export” all of its power to the upstream inverters unless necessary.
Anyway, I can’t find anything wrong with this plan. Which of course means I’ve overlooked something. Any thoughts?
One thing I’m really not sure about is grounding. Can I get by with triplex URD cable between the structures, and rely on ground rods for grounding at the downstream structure? Or is it better to run four-plex with a continuous ground between the buildings? Probably will bury 3 feet deep anyway, but I’m thinking it would be safer to have a ground in the trench.
Also, I suppose I’ll need to un-bond the ground and neutral at the downstream structure, since it no longer would be the “main” panel of the system. Is this correct?
Thoughts and advice are greatly appreciated.
