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Posted to uk.d-i-y
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Clever electrical scheme
On 19/11/16 19:43, Roger Hayter wrote:
Tim Watts wrote:
On 19/11/16 12:43, Roger Hayter wrote:
Just replacing a bathroom light fitting. Running from it in the
opposite direction to the standard 1.5sqmm T&E supplying it is a single
core 1.5sqmm red cable (proper PVC outer sleeve and everything). This
connects to an extractor fan, providing a live connection switched by
the light switch. The light circuit is part of a 10A light circuit,
eminently reasonable so far. However, the fan is also supplied with its
only neutral and a permanent live connection from a fused (13A) but
unswitched spur off a nearby socket circuit.
Don't ask me how I know, but this is an electric shock risk (fortunately
only to parts of one hand owing to good self-training).
Does anyone think this is a good idea?
No, that's not OK.
For one, you are effectively sharing a neutral between two circuits.
And you are potentially sharing the lives if the fan electronics fails
in an interesting way.
If you had to do this, using a relay as a full galvanic isolator (relay
coil driven by lights, contacts on the socket spur side) would be
theoretically OK - but it will still confuse the next person who looks
at this.
Can you not pick up a lighting live from somewhere?
It was a bit of a rhetorical question - I didn't leave it like that!
Oh - OK 
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