Working on electrics with 2 supplies.

[HappyHippyDad]

I have little knowledge of PV.

When working on circuits supplied by a domestic CU, is it fine to just have the main switch off in the CU or should you be isolating the PV as well?

The stickers all over the CU's in this example all say to disconnect both supplies.

 

[PEG]

I believe you're correct.

However, for the sake of flicking a switch, would you risk it?

Definitely not ...but if someone did not know that already,they need to pass the tools along...

 

[Lucien Nunes]

The inverter itself should shut down so that it does not backfeed AC to the DB when the mains is off, although as mentioned one should not rely on that. Because its output neutral is not referenced to earth (until it is tied to the DNO supply) the SP MCB does not make it 100% safe if it did start up, as a difference in leakage could make the N more live than the L.

But, the main point of the '2 supplies' stickers around the inverter is to remind that with the AC off, the DC from the panels is still live unless it's dark. So before working on the inverter, both the DC and AC sides need to be isolated.

 

[Pete999]

The inverter itself should shut down so that it does not backfeed AC to the DB when the mains is off, although as mentioned one should not rely on that. Because its output neutral is not referenced to earth (until it is tied to the DNO supply) the SP MCB does not make it 100% safe if it did start up, as a difference in leakage could make the N more live than the L.

But, the main point of the '2 supplies' stickers around the inverter is to remind that with the AC off, the DC from the panels is still live unless it's dark. So before working on the inverter, both the DC and AC sides need to be isolated.

Also see post 4

 

[Lucien Nunes]

Pete makes a very good point. It's easy to fall into the trap of thinking that the second supply 'must' be the PV, when there's an automatic backup set ready to spring into life the moment you pull the public supply main switch, and a hidden UPS in what used to be the computer room but now isn't, etc etc.