In article , ARW
writes
On 28/02/2019 16:44, Robin wrote:
On 28/02/2019 15:00, GB wrote:
On 28/02/2019 14:38, dennis@home wrote:
On 28/02/2019 14:15, Paul Herber wrote:
On Thu, 28 Feb 2019 12:21:12 +0000, bert wrote:

In one bedroom we have a ceiling fan supplied from the lighting
circuit.
It's been there for over 10 years no problems.
In the past few nights a couple of times when switching it off the RCD
protecting the ring mains has tripped. But the lighting circuits don't
go through it and the lights are still on including the one which is
part of the fan and the fan itself can be switched back on.
Puzzled as to how this can happen - and where to start looking.

Earthed via a the ring-main circuit?




Probably not, RCDs don't just detect earth leakage but any current
imbalance between live and neutral.

It wouldn't actually matter where it was earthed if there was
leakage to earth and it wouldn't affect other circuit unless they
also had an earth leakage problem as RCDs aren't connect to earth.



Quite agree. I think Clive is probably right as to the cause. Within
the consumer unit, all the lives and all the neutrals are connected
together, so there's scope for some coupling between circuits. The
only thing that's really surprising (to me) is that the RCD
protecting the lighting circuit does not trip.
I wouldn't assume there there is an RCD protecting the lighting
circuit. *Very many homes don't have them.


Of course the 18th edition has altered that for future installs (I
think you are correct about the OPs lights)

He is. No rcd on lighting circuits. Personally I think they are as much
a liability as a help.
Just for info and not related to the OPs question. Domestic properties
are now required to have RCD protection on the lighting circuits even
if the cables are run in a manner or of the type that would not require
RCD protection (eg in trunking or SWA)


--


Adam

--
bert