replacing old CU + wiring bathroom fan - please help

[glider2]

Hi,

I’d like to replace my girlfriend’s old CU (see picture in profile) with a new one that has MCB’s for each circuit as well as RCD protection for the sockets and for the circuit from which I will install a bathroom fan. I have a few questions relating to this project:

1. what CU configuration should I go for? The current installation has 4 fuses (30A for sockets, 30A for cooker, 5A for lighting and 15A to the cupboard light where I guess there used to be an immersion heater). What should these be replaced with? Where does the RCD go if I want to run a cable from the bathroom lighting switch to the bathroom fan? I should also protect the socket circuit, correct?

2. how do I isolate the current CU to disconnect it a reconnect a new one? Any special tools needed to do this?

3. regarding the installation of the bathroom fan (see window picture in profile). The bathroom has a ceiling mounted light with a switch just outside the bathroom. I thought I’d mount the fan on the window (in zone 2) to avoid having to bore a hole through 30 cm of tiles and brick. Regarding the wiring, I thought I’d pinch it from the bathroom lighting circuit, through a 3-pole isolator switch and to the fan. How would you run the cable? I don’t think there’s a void in the ceiling to run cable easily, so a cable run would need to be bolstered out, correct? How do I get across the wall tiles to the window mounted fan? Where should I place the isolator switch given that it needs to be outside zones 0-3? There is a bit of space on the ceiling that would sastisfy that requirement.

Thanks.

 

[Click-Sure]

Beware of old CU's with old rewirable type fuse carriers as over time people tend to add to them willy-nilly over time, its not that unusual to find several circuits all fed from one fuse, ring finals spread across fuses etc etc.

Before a CU change is even attempted it is best practice to thest the existing fixed wiring thoroughly to find out its condition - remember, just because it works does not mean that it is safe!

isolating the existing CU means fulling the service fuse. There is a topic of debate on this but curring the seals and pulling it is illegal and should only be carried out by your DNO. Getting them to fit an isolator is the best option.