Help with solar pv advice

[Fergie44]

Hi, we've just fitted a new consumer unit in a house with two solar PV installations, one on a garage, one on an outbuilding, which are supplied by their own DBs, tapped from old rewireable fuse boards which control sockets and lights for the garage and outbuilding. These rewireable fuseboards are supplied from our new consumer unit, our issue is we want to fit stand alone RCDs for the rewireables to protect the sockets and lighting. The solar installer has assured us that we can fit normal RCBOs in our consumer unit without any worry and that the inverter will shut off within 0.5 of a second although we are worried that if a fault occurs on the sockets that our RCBO will trip out first and therefore could possibly get backfeed from the DC side of the solar into the sockets and lighting because the RCD on their DB hasn't tripped, therefore contacts are closed. Any advice? Are we OK to just fit RCBOs? Are we sticking to regs?

 

[dansk]

Is it like this?

Main c/u, feeding 3036 board, which feeds pv db?

 

[moggy1968]

What inverter do you have?
Solar asside, there is no value in fitting RCDs in the garage as they are (I presume) protected by the RCDs on the main board. There will be no discrimination, they would both trip.
I wouldn't like to see the PV sharing an RCD with a household circuit however.
If the garage supply is non RCD (which it doesn't need to be if it is fed by SWA and your system is earthed by your supplier rather than a stake in the garden) then I would fit an RCBO on your garage sockets and feed the PV off an MCB (no rcd protection)

 

[Fergie44]

Yeah there is 32amp MCB feeding garage, 20 amp MCB feeding outbuilding from main ccu to re-wireable and solar installers took supply out into connectors to supply solar DBs and re-wireables.

 

[Fergie44]

Inverter is a sunny boy 1kw. House is TT. The PV has its own DB fed by a 20A MCB which they've put on a 30mA RCD and there is also an old re-wireable fuse board with 30A fuse and 5A fuse. We've fitted an MK15 way board and the first five circuits are the only ones left which are on the non-RCD side, so we are hoping we could fit RCBOs instead directly in the board rather than fitting RCDs in the garage but for some reason we're thinking that it wont comply if we fit RCD protection at the main board back in the house?

 

[moggy1968]

TT, what a pain!!
All your circuits then need to be RCD protected. I would feed the garage with a time delay RCBO and then individual standard RCBOs in the garage. This will give you some discrimination on tripping (if your working in the garage it will trip before the house RCBO, saving you a walk indoors!)
you may need a type B RCBO for the solar, but the jury is still out on that one!

 

[SolarCity]

TT systems are interesting with RCDs. It has been discussed here before:

http://www.electriciansforums.net/p...gy-forum/48796-ads-rcds-pv-installations.html

I still don't think that a type B RCD is necessary but as always I'm prepared to be shown otherwise.