John Rumm wrote:
On 11/09/2012 16:29, Thomas wrote:
Hello

Following on from my recent installation of an extractor fan.

The fan I fitted requires 4 connections: neutral, permanent live,
and two switched lives. I bought myself a length of 4 core cable of
the required

Sounds like your bought one wire too few...

rating but I'm confused about which colours to use and whether
there might be a different coloured cable that I should have used.

Blue is neutral, while brown, and black are "live" colours (in the
harmonised colour scheme). Green/yellow is earth.

The cable that I bought has inners coloured brown, blue, black and
green/yellow. I wired the blue to the neutral and the brown to the
permanent live - leaving the black and green/yellow for the two
switched lives. I have a 3 pole isolator on all of the live cables,
but even so, I'm not comfortable with having a green/yellow for a
potentially live cable and I'd like to find a solution to this asap.

What is the normal convention in these situations - is there a 4
core cable with different colours made specifically for this type
of installation?

Its very bad practice to re-purpose a green/yellow CPC in a
cable/flex.
The typical 5 core flex used by central heating installers may be more
appropriate. Or I would probably run a length of T&E and one of 3&E to
give five cores plus earth.

As both John and Andy have pointed out you should not use the green/yellow
for anything other than "earth". It's also bad practice not to run an earth
out with all the other cores even for something that will not be earthed.
You "park" the earth core in a piece of strip connector inside the fan.

As they both said, 5 core flex is one suitable answer.

--
Adam