www.ultimatehandyman.co.uk

I know an amendment is about to be issued with BS 7671 on the use of omi directional RCD's where one can have power both sides.

however if the RCD does not cause the supply to fail, what is the point? I can see if fitted the wrong way around then after it trips it can still energise the tripping mechanism so cause over heating under fault conditions, but I looked at my own solar and battery install and the solar inverter is designed not to island, so if the supply is removed it shuts down, so even if the inverter did have a RCD between the inverter and grid, it would never trip and have power both sides.

Yes power can transfer in both directions when all is running correctly, but how would the direct of power flow affect a RCD? Current always flows in both directions as it is AC.

An RCD marked “in” and “out” or “line” and “load” or with arrows indicating the direction of
power flow can have their RCD function rendered permanently inoperable when connected
incorrectly e.g. if, under certain conditions, there is a voltage present on their load terminals.
The damaged RCD could remain in use without indication that its RCD protective function
no longer operates.

According to


https://www.beama.org.uk/static/c3939aa ... evices.pdf

Most Solar inverters are designed so if the grid fails they will auto disconnect from the grid supply, this is required to ensure when the grid is switched off for any reason you do not get a back feed. However when the grid is live then power can travel in either direction.

I can see how with a RCD fitting it in reverse can result in circuits within the device remaining live after it has tripped, however it is rather pointless for any trip to be arranged so there is power both sides when the contacts open.

There is differing guidance from industry bodies on whether a microgenerator should or
should not be installed to the load side of any RCCB that is shared with other circuits

Really, how would a RCD cut the supply to the shared device?

When I first read the report I took it on face value, but as one starts to look at bi-directional RCD's one finds they are also marked load, the advert clearly says they are bi-directional but the pictures show them marked load, so some one has it seems got it wrong.