Short version: if a circuit is protected by an RCBO, do you also need an RCD? Long version: I have a two storey garage with a Consumer Unit; the CU has a 100A Mains Switch, a couple of 32A MCBs (one for the downstairs sockets, one for the upstairs), and a 6A MCB for the lighting. The garage itself appears to be fed from the house via a small separate CU with a single MCB and an RCD (what I'd think of as a "Shower Unit"). It looks a lot like this: https://www.screwfix.com/p/wylex-4-...-shower-consumer-unit/3458j?_requestid=513183 The problem is that the garage has a mains-powered roller shutter door, so if I'm in the garage and trip the RCD (in the house), I'm left in the dark (and have to override the door and lift it to get out). I can't change the 100A Mains Switch in the garage CU for a DP RCD, as if the RCD is tripped from a socket on the garage upper storey (accessible through another door) it would kill the power to the roller shutter door (which would need to be manually opened in order to get into the ground floor, in order to reset the RCD). To try to solve this, I've replaced the two 32A MCBs in the garage CU with 32A RCBOs. Everything's Type B, but unfortunately it seems the RCD in the house trips before the garage RCBOs; so it doesn't help. Because all circuits in the garage (apart from the lighting) are now on RCBOs, would it be acceptable to replace the RCD in the house "shower unit" with an identically rated Mains Switch? I'm aware the RCBOs are Single Pole (breaking the live only), but I assume the DP RCD in the house will break both live and neutral when it trips.