In article , GB
writes
On 28/02/2019 18:02, ARW wrote:
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)

Is that on the basis that it's okay to get electrocuted by the lighting
circuit? Perhaps it's a more refined way to die.


Very limited opportunities to be electrocuted by a lighting circuit
compared to a ring main.

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