will a SELV bathroom fan need RCD protection?
No, the voltage however has to be below 12 volt, but S = separated so there is no earth, so a RCD can't possibly work even if you could get one to work on extra low voltage.
Our lighting is on the non-rcd side of the CU but I'm sure I read somewhere that any electrics in a bathroom should be rcd-protected
Yes it does need RCD protection.
Don’t use a RCD-FCU on a lighting circuit. The fuse will have no discrimination against a 6a MCB
Yes likely the fuse will not rupture even if 1 amp, but since not interested in the fuse but the RCD protection yes likely a way to get the RCD protection as long as passive not active.
The idea of fitting in the CU is best, and today there are short RCBO's so many can be converted, but not all, my old house still has old Wilex board with fuses replaced with MCB's there is no way those can be changed for RCBO's so depends on CU, and the make there are some obsolete ones that can't be upgraded.
If there isn't one then a fault in the fan could leave you in the dark ( RCD or MCB tripped ) until an electrician can come and isolate the fan from the lighting circuit
That is very good advice, even if isolator in the loft you need a way to disconnect the fan.
I'll get the spark to handle it I guess...I was just thinking about cable routes and possible boxes!
Good idea, he needs to sign he has designed it, so unless he tells you to run a wire or cable, then don't do it, bathrooms are a special location so need council informing that work has been done and complies, don't really know why, as when I tried to get a copy they could not provide it, so much for traceable record.
P.S. if it is a new shower do remember 3 meters to any socket in same room, if in bedroom hight of doors and gaps over doors matters.
