"Andy Burns" wrote in message
...
Dave Plowman (News) wrote:

Because they have a permanent live for the timer circuit as well as a
switched live from the light. Hence the need for a three pole to totally
isolate them.

Thanks, but as I said lurch pre-empted (rather than prompted) my
question, I could see why you'd need to isolate the permanent and
switched lives, but not why you'd need to isolate the neutral.

Actually I still do wonder *why* (apart from "them is the rules") I mean
a ceiling rose is fixed wiring and you can't individually isolate
neutral from that ... so why is it deemed necessary to do so on fixed
equipment such as the fan?

What if some twerp has reversed the positive and neutral connections at some
point further back in the circuit ?...

With 'portable appliances' you can isolate them by pulling the plug out -
not so with fixed appliances IYSWIM.