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?

--

Roger Hayter

On Saturday, 19 November 2016 12:43:21 UTC, 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?

It's a very bad idea. There is the possibility in the event of a fault that live can backfeed from the extractor fan if the semiconductor timer circuit fails, to the socket circuit even if the socket circuit is switched off at source. Someone working on the wiring could easily have full 240V hand-to-hand if only the socket live source was disconnected (MCB opened or fuse pulled).

Owain

Yes one should strive to get all connections from the one place not two
separate ones as in the future you may not be around to warn them.
Personally I do still find having unswitch lives in ceiling roses a bit of a
nonsense, but then that is probably just me.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
wrote in message
...
On Saturday, 19 November 2016 12:43:21 UTC, 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?

It's a very bad idea. There is the possibility in the event of a fault that
live can backfeed from the extractor fan if the semiconductor timer circuit
fails, to the socket circuit even if the socket circuit is switched off at
source. Someone working on the wiring could easily have full 240V
hand-to-hand if only the socket live source was disconnected (MCB opened or
fuse pulled).

Owain

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?

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!

--

Roger Hayter

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