I currently have the hall ceiling PB down, all the plasterboard out of the airing cupboard on the landing so have access to the stud & partition walls within said airing cupboard. The Consumer unit is in the hall and has 5 spare RCBO ways. (a shower booster pump had exploded spraying hot water all over when it was under a previous owner so all the plasterboard had failed).
I may want to one day put a solar PV array on the roof.
Now it seems a good idea for me to lay some twin and earth cable from a spare RCBO way in the CU (in hall) through the hall ceiling, up the airing cupboard walls into the loft and put a junction box on the end with a suitable label.
The total cable length to the inverter (which I assume will be in the loft) will be no more than 15 metres.
Now my questions are this.....
If I assume a PV array up to 4kWp, that makes it up to 18.18 amps (assuming lossless 100% efficient inverter of course) so that suggests a
20A RCBO and according toGiven the 15m cable length and the narrow margin of 2A between the peak current output of the inverter and that the 2.5mm2 cable is rated up to
20A, I am inclined to lay 4.0mm2 cable while the plasterboard is down.Is my choice of a 20A RCBO OK for a PV array or should I be using the next rating up and hence increase the 4.0mm2 to 6.0mm2 cable?
I have room to leave a few metres of cable in the void behind the CU so the cable can be pulled further into the hall if it has to go into boxes of gubbins mounted next to the CU before finally being wired into the CU's spare RCBO way.
Can a RCBO be used the "wrong way round" or does PV specific RCBO's have to be used? (my CU is a 2 pole isolator main switch with 13 RCBOs so no seperate RCD or MCBs are used.)
Will a FIT accredited installer be happy to use this pre-laid cable or will they refuse to use and lay their own cable in horrible white trunking?
Do I have to make the entire cable run visible to them for inspection purposes?
Will any extra boxes be needed next to the CU such as a generation meter and isolation switch or can all these go into the loft?
Looking forward to the comments...
Stephen.