Jason:
I am wondering on the advisability of hardwiring the outputs of all four inverters together. If one inverter fails the other three can backfeed into it without any means to disconnect the failed inverter and without over-current protection. Have you considered landing the output of each inverter on a separate, appropriately sized 2 pole breaker in the output load-center? In the same vein, how are you feeding generator input into the inverters? Are these hard-wired paralleled as well? You might consider having the generator feed a dedicated load-center with an appropriately sized breaker to feed each inverter. You protect the conductors as required and you can isolate any inverter for service What size should these breaker be? If your inverter can supply 62.5 AAC, upsizing for continuous duty and to the next higher standard breaker size you get 80 amps. If you use 80 amp breakers into and out of each Sol-Arc you require #4 copper at 75°C. Each inverter and all of the conductors are protected for the max current they will see and you get the combined amperage at your output. There should be no need to run 400 amp wire. BTW, you can easily contrive a bypass system by creating a sliding mechanical interlock. You run an appropriately sized feeder between the generator fed and inverter fed panels. The bypass breaker in the inverter-fed panels is interlocked with the inverter output breakers. The installation might look like this <https://millersolar.com/MillerSolar/Portfolio/Inverters/battery_iinverters/Chimney_Rock/Chimney_rock.html>. This is way cheaper and easier than installing an additional 200A, double-throw safety switch. (A home-made interlock may not be listed but what is the worse that will happen if all breakers are on? The inverters will detect backfeed and shut down. No harm will come of it.) Hope this helps. William Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski via RE-wrenches *Sent:* Tuesday, March 26, 2024 2:26 PM *To:* RE-wrenches *Cc:* Jason Szumlanski *Subject:* [RE-wrenches] Sol-Ark 15K AC Output I am going to have a quad-stack of Sol-Ark 15K for an off-grid 120/240V system with a 150A generator. I know the max real power is 62.5A each inverter including battery and PV. That would be 62.5A x 4 = 250A total. I intend to connect the output of the 4 inverters together with a 5-port Polaris tap, with the output of the Polaris Tap going to a 400A main lug only panelboard. My question revolves around the 200A passthrough capability for the generator, which is 150A max output and would be connected to the Grid input on each inverter. Since each inverter would need to handle the full pass-through current, that would require minimum 150A conductors on the input side of each inverter. I am under the impression that the inverters can supplement the "grid" or generator in this case if the current exceeds the available input. That means the inverter would have 150A of input plus 62.5A of inverter power for a total of 212.5A. But there is a 200A load OCPD, so I could size the load conductors from each inverter for 200A. Obviously the 4 inverters can only pass through 150A from the generator in total, which would probably be split among them, but could go through a single unit if the rest fail. Now, is it possible for each inverter to output 62.5A each PLUS 150A of generator power spread across them for a total of 400A? That is important because I would need to size the combined output conductors for 400A if that is the case. I guess I'm not clear on how Sol-Ark 15K handles grid/generator assist/supplement. It does not seem to be documented clearly. Jason Szumlanski Florida Solar Design Group
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