Bathroom fan installation

[CJR]

Hi - hoping someone can offer some advice here.
I am installing a XPELAIR DX100S bathroom extractor fan (replacing a broken one) however the customer wants it to be wired in isolation (i.e. not switched on/off in connection with the bathroom lights). The previous one was however and therefore the existing cable supplying the fan is 3 core and earth. Is it safe to terminate the existing grey wire at the fan and at the fan switch leaving just one 3 core and earth cable connected in the fan switch? Or is there a concern leaving a permanent live feed in the fan switch (which I assume leads back to the ceiling lights as the supply into the light switch is 2 core and earth and so not coming from there!)
I'm confusing myself just writing this so hope someone can make sense of my wafflings!
Thank you

[moderator2]

Moved to Electrical.

[wine~o]

You are not just confusing yourself, you are confusing me. The fan requires permanent live, switched live, neutral and earth which is 3 core and earth... Unless you mean that the customer doesn't want the over-run ???

[Someone-Else]

(I didn't understand when I first read it either)

[aeromech3]

Guys sorry, I just fitted one of these, it has no switch or timer but needs 3 core as it has an earth terminal (not sure why as it is plastic) also the live neutral terminal block is very small and cable route only on one side; it came with a kit of extending duct, outlet shutter and some seals; I had a problem with mine as a decal inside the fan track lifted and caused the blades to stall however Xpelair where very good about my complaint.

[Someone-Else]

but needs 3 core as it has an earth terminal (not sure why as it is plastic)

Sorry to correct you, but the earth is NOT counted as a core in a cable, so the cable you would use is called Twin and Earth, not 3 core.



This is Twin and earth cable




This is 3 core and earth cable




This is 3 core Flex


The earth terminal is to terminate the earth of the cable. If the cable is cut the current should flow down the earth. Also if the fan is ever changed and needs an earth there is one there.

[aeromech3]

Thanks S-E for the lesson, I understand better the reason for the inner bare earth wire in twin and earth!
What I took as an earth terminals is in fact screws for expanding the clips which grip the ducting.
Xpelair instructions state:- "The appliance is intended for connection to fixed wiring". blar blar "THE APPLIANCE IS DOUBLE INSULATED AND DOES NOT REQUIRE AN EARTH CONNECTION".
Later it states for the DX100S - 2 core but for those with Timer / Humidistat 3 core. The plastic body has moulding for a pull cord switch, timer and movement sensor even though the DX100S does not have these.

[CJR]

Thanks all. I don’t think I explained my question very well! I was wondering what I do with the spare “core” (ie what was the switch live supply in the old fan). So what I did was terminate it at either end of the cable (ie at the fan and at the fan switch). Hoping that’s ok but open to other ideas of what others would have done!

[wine~o]

Just isolate it. Leave it in place in case it is needed in the future.