I was thinking of back EMF.
That could make it back through the lights to the other circuits as a
spike of some kind.
Brian

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"Tim+" wrote in message
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bert Wrote in message:
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.-- bert

It would suggest that it's not supplied by the lighting circuit...

Tim
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