What do you need a auto transfer switch for? How big is your battery bank and how large is the household load?
That is how mine will be wired, except I will run the inverter EGC's directly back to the bonded main panel and a seperate EGC to 3 pole transfer switch and on to the subpanel.
I don't think you need the auto switch. You can use the Manual xfer switch to directly supply grid power to your sub-panels should you need to take the LVs offline for any reason. My question is how do you isolate them from AC in? Is the feed to the manual xfer switch before or after that 60A breaker you show? If before, that's my answer (and glancing at your diagram again I just saw the 100A breaker feeding that line so nevermind I have my answer)
Battery bank is 38.4 kWH, covering one sunny day ... normal house load, with current AC unit is 54A (strangely, exactly the capacity of the two inverters in inverter mode). I'll be adding 5 mini-splits soon which should take that number down considerably, except when the central still goes on. The original plan/calcs were made to cover 90% of the energy use ... everything but high throughput loads (such as once in a blue moon I have 4 burners going on my stove). So, I'd like to get everything possible on the solar system as possible, as close to the capacity of the 54A as possible, then never have to worry about overloading it, nor the system running out of juice. Thus the auto-transfer ...
So both inverters directly back to the Main instead of tied to each other first? Somewhere in that long thread you basically showed the pic I'm showing ... did you change your design slightly? As I recall, you were talking about objectionable current between the inverters on the Ground, but that that wouldn't matter on a "single" power source, especially in metal conduit ... does sending them both directly back to the Main fix that?
See above for whey auto-transfer switch ... fire and forget. (My family would be really annoyed otherwise with outages as I'm trying get as much as normal use as possible running through the solar system.)
Yep, 4S2P is correct. Just fixed that. Thanks!
I just realized ... you're right, in this design, there's no need for the auto-transfer switch at 60A. I need a larger one to handle any overages ... as well as a larger CB on the main box ... let's go see if I can find one ...
I would use a 150A breaker in your first panel after the service entrance direct to a manual XFER rated for that amount, run the 60A outputs from the two inverters to its other input. The output would be Teed to feed both of the subpanels.
Inverters daisy chained. There will be objectionable current between the 2 inverters under inverter power depending on balance of 120V loads.
I think you need to look at conservation first and spend the money there. A 38.4Kwh battery will not supply a 54A/13Kw load for a day, only about 3 hours continuous. Granted, the load won't be continuous however it does show less than 3 hours of actual runtime. PV is 14.5Kw, the math just doesn't work well.
I've got a similar system where the math doesn't really add up, but it does allow me to shave some of the electric cost. My math is worse than his as I have only 2K worth of solar connected to 20KWH worth of battery. I cycle the battery bank between 60 and 85% SOC (when I can get it that high) each day. In the worst case the 60% could feed my normal consumption for about 10-hours allowing the storm to pass and the grid to return or the ability to start the genset. If the situation is really in the toilet I can load shed in the subpanel.
But ... that would mean I'd have to think about how much power I'm using, no? If I'm understanding you correctly(?), I'd be on solar-only with +6A backup through the inverter to the grid unless I manually switch back to the grid. I don't want to think about it and at the same time I want to max out my solar usage ... if I go over on the high use loads, the auto-transfer simply gives me back essentially what I had before going to solar. For the high amp/low use stuff, $10 a month max to pay for that from the grid is fine with me, especially so long as my 5 and 10 year olds don't have to worry every time they flip a switch ... did I understand your suggestion? Just words are difficult with this type of stuff ...
The LVs will "blend" grid and solar when set to SUB or SBU (Solar Utility Battery or Solar Battery Utility) mode. Unless you're going to be exceeding 6500 watts on either leg the machines would be fine. If you pull beyond that you're right and I misunderstood. I my setup I specifically excluded certain circuits due to my capability limits (wall ovens, central air, laundry, dishwasher)
First, thank you. I'm enjoying defending this design ... this is a great experience, as I'm finding holes that I otherwise wouldn't have thought of. I doubt that even if I'd hired a master electrician with tons of solar experience I could have gotten what I wanted. (I have a couple of contractors, right now, out front building a simple stone column for a fence, and I'm walking out every 30 minutes micro-managing them.)
On the first inverter, you would use the EGC port on input and output. Internally the EGC ports are interconnected. As for 2 EGC's from the inverters run in the conduit to the transfer switch as shown in the diagram, I will only have one as there will only be one conduit from inverters to the transfer switch. That EGC will come from the second inverter.
