On 27/10/2020 17:30, me wrote:
@John Rumm, not sure I understand what you're saying. What I intended
was to run some three core and earth from the shower pull switch so
that I'd have a permanent live and neutral and a switched live all
going to the fan via a fused fan isolating switch. So the fan will
still run on when the shower pull switch is turned off after using
the shower. None of that would go near the consumer unit of course.
Does that sound ok?


Yup, that would be fine - your OP made it sound like you just wanted to
pickup just from the switched live from the shower isolator.

The only slight practical difficulty you may have is getting a good
termination on the smaller fan cable at the same time as the (sometimes
significantly) larger shower supply cable, bearing in mind shower
connections need to be 'kin tight!

You will also need to check that whatever cable you use to connect the
fan is offered adequate fault current protection by the shower MCB. This
is not likely to be a problem with say a B32 MCB and 1.5mm^2 3&E. But
you start getting more marginal on larger MCBs and shorter cable lengths
(as the prospective fault current rises). Having the fuse close to the
main shower isolator helps reduce the risks.


--
Cheers,

John.

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