Will this CU have live circuits after the RCD trips?

[ccam108]

I've been looking at a new build property with solar panels on the roof, and I took a photo of the consumer unit. One thing that caught my eye was that the solar panels appear to be connected to an MCB that is downstream of an RCD.

Is this normal? It looks to me like if a fault occurred in one of the circuits on the same RCD, for example the kitchen sockets, then those circuits would still be energised from the solar panels after the RCD trips.

 

[DetlefSchmitz]

In my opinion it is a crap way to connect the PV, although actually very common. I much prefer connecting to a Henley block between the meter and the CU. This allows proper monitoring points for import and export, as well as making it easier to make your own decisions as to whether an RCD is required.

 

[AdrianUK]

I can understand your concern, but the designers of solar systems have taken that scenario into account.

The solar panel inverter MUST should down when it notices that the mains has disappeared. The are many reasons for this requirement, not only to prevent backfeeeding of circuits in the manner you suggest but also to prevent your solar system from attempting to backfeed the street in the event of a power outage or to cause danger to a linesman attempting to repair a fault.

It also follows from that it is not possible to deliberately use a solar panel system as an alternative to the mains and hence create an "off grid" supply.

 

[flameport]

In my opinion it is a crap way to connect the PV, although actually very common.

Not only crap, it also means that when a fault occurs and the RCD trips, the power will not be disconnected within the required maximum of 40ms.
On an EICR, code C2 and Unsatisfactory.

Is this normal?

Probably happens a lot, but PV systems should not be installed in that way.

 

[ccam108]

The solar panel inverter MUST should down when it notices that the mains has disappeared.

That makes a lot of sense, thanks.

Not only crap, it also means that when a fault occurs and the RCD trips, the power will not be disconnected within the required maximum of 40ms.
On an EICR, code C2 and Unsatisfactory.

Is it something that I should bring up with the site manager during snagging? Next time I visit, I might take my RCD tester with me to see if it does fail.

 

[flameport]

Is it something that I should bring up with the site manager during snagging?

Definitely. If a fault occurs, the RCD trips, but you then have the extra time it takes the inverter to detect the loss of power and shut down - which is anything up to 0.5 seconds, far in excess of the RCD maximum disconnection time.

PV should be connected via it's own MCB with no RCD, or if an RCD is actually needed, via a separate RCBO.