Looking at this Swiss inverter it's 2.3VA, 1.3 times rating for 15 mins. Where did you get this 6A figure from and how do you find an inverter Isc the easy way?
The 6a figure came from the SMA SI3.0M manual, which is a 2.3kW unit, for which they recommend B6. Basically it's limited by the output impedance, which rises a tad as the inverter warms up. Is it in the manual?
You'll have a loop impedance tester. Had odd results trying that on a large diesel genny, and IIRC the PWM output of an inverter ain't going to help. Or try a 10A mcb and a 6kw load. If it doesnt trip, drop the breaker. It's a really tricky subject, particularly on large island generation, as fault levels change depending on source. Protection engineers earn their money.
Hopefully another member will have a good answer.
Ok...so hypothetically if my inverter has a live-earth or neutral-earth fault and the inverter RCD(s) sticks closed, and the fault goes to the grid neutralising point backfeeding the Grid RCD, no smoke?
A N/E fault doesnt always trip an RCD (in PME), and the fault current will be minimal and won't exceed the touch voltage. The live fault would go inverter L, (RCD) MCB, RCBO, load, load case/E, earth point, inverter E = inverter N, so the MCD should trip in 0.4s. On a socket circuit.
If the breaker didnt go, then the inverter would probably shut down on over current. So other than sharing the earth point, there is no connection to the grid. If you're still in doubt, drop an earth rod and use that for the inverter. Your protection will be worse due to rod impedance/touch voltage. Hmm. Wouldnt recommend that as you'd then have different earth potentials in one room, and that will be outside the regs.
For info, note that you have the potential for 380V at your inverter only sockets WRT grid, as the two aren't synchronised. Many years ago there was a 'rule' that you couldn't have socket outlets on different phases in the same room, but I can't remember reading that anywhere that mattered.
Just noticed you're using DP MCB. You could go single pole safely, as inverter N & E are linked.
With a 12 year life on those batteries, if you limit the continuous current to c/10 = 125/10 = 12.5A, twice for each string, = 25A x 48V = 1.2kva, they will probably go on longer.
I got a similar set up to you (10 year Yuasa 100Ah), in similar circumstances. All 8 lasted ok for 12 years, 2 died at 13 years, but I didnt notice as they were in series on a 24V setup. Now at year 15, they are not in great shape and have around 25Ah capacity. Time to scrap them.
Calculations for cables assume an operating temperature of at least 60C, and a lot higher depending on insulation. I have to admit not liking feeling incomers at that temperature in factories, etc. Good tip on the sense cables. I have used bolt on fuses in the past, covered in heatshrink.
No more pictures of your solar po*n. We'll need to call a nurse for Biff.
