How does a solar inverter connect to a CU without bypassing the RCD?

[jacoscar]

Hi all, I've had quite a few solar panels quotes from different solar companies and I realise I have asked questions that they might not have been able to answer correctly as they were the salesmen and not the electricians doing the work.
I think one of them said they will connect the inverter to one spare MCB of the consumer unit, is this correct?
I have a consumer unit with a single RCD for both rings and two non RCD lighting circuits; if they connect a new MCB to the RCD side of the consumer unit, doesn't that mean that in case of a fault on one ring, the rcd might not disconnect because the current is flowing from the inverter to the ring directly without passing through the RCD (as there is no power drawn from the grid)?

 

[flameport]

connect the inverter to one spare MCB of the consumer unit, is this correct?

Yes, that is the usual method.

if they connect a new MCB to the RCD side of the consumer unit,

That arrangement is not permitted, the inverter must connect to an MCB on the non-RCD side.

If connected to an RCD which also supplies other circuits, when the RCD trips the inverter will detect the loss of supply and shut down, but not within the required disconnection time of the RCD.
If the circuit to the inverter requires an RCD, then that RCD or RCBO must supply the inverter only.

 

[jacoscar]

Yes, that is the usual method.


That arrangement is not permitted, the inverter must connect to an MCB on the non-RCD side.

If connected to an RCD which also supplies other circuits, when the RCD trips the inverter will detect the loss of supply and shut down, but not within the required disconnection time of the RCD.
If the circuit to the inverter requires an RCD, then that RCD or RCBO must supply the inverter only.

Thanks, so they connect it to the non-rcd side on the CU.
Isn’t another reason that if the load on one rcd side circuit is less than the current pv production (and excess going into a battery), then all current flows from inverter to said circuit, without going through any rcd? Is this even remotely possible?

 

[bernardgreen]

they might not have been able to answer correctly as they were the salesmen and not the electricians doing the work.

If they are selling an item then they should have the technical knowledge to answer the questions the potential purchasers are going to ask.

 

[JohnD]

.. then all current flows from inverter to said circuit, without going through any rcd? Is this even remotely possible?

No.