Wiring for Bathroom Mirror - Want to use old shower switch.

[Jurassicspark]

If the mirror has an issue in the future, will it not stop all the lights on the same circuit from working?

Trying to understand best practice!

It can but its not a biggie. I doubt the mirror will develop an issue to trip a RCD.

I take it that you've got a split load consumer unit if you do then you don't need to lose sleep over it.

 

[Taylortwocities]

If the mirror has an issue in the future, will it not stop all the lights on the same circuit from working?

If you use that avenue of thought, you would have a separate circuit for each and every device in a house.

 

[SUNRAY]

Or when you've got a socket on the shower cable plug your mirror light into that

This is most likely to be the easiest solution.

It provides a socket in the loft which one of our ex members would enjoy messing his pants over.
It provides the cheapest way of installing an appropriate fuse.
It provides the desired isolation between the existing lighting circuit and the mirror light.
It provides perfect isolation when doing future works; such as changing the mirror, redecorating etc.
There is only one downside or disadvantage that I foresee - you would have to access the loft for the isolation.

If you do this arrangement do not shorten the existing cable, that leaves it reusable for its original purpose if required.

 

[Jurassicspark]

There is only one downside or disadvantage that I foresee - you would have to access the loft for the isolation.

Or just turn off the MCB/RCBO supplying the shower.

 

[SUNRAY]

Or just turn off the MCB/RCBO supplying the shower.

Which is likely to leave the neutral connected - not usually a biggie.