Witchy wrote:
Hi folks,

Not been here for ages 'cos of a new job Down South, hence no diy
apart from weekends!

Anyhoo, got an oddity at a mate's house with the bathroom light. The
switch is outside the door and contains 3 cables, one of which looks
like it contains 2 red wires?! 2 blacks are joined in a choc-block,
one red doesn't go anywhere and the other 3 reds are in the switch.

Ceiling rose has 3 sets of cables, one of which goes to another light
which is being removed.

Now the conundrum - with the light OFF there's 240V across the swtich.
Turn the light ON and the voltage vanishes.

Any clues?

cheers

adrian/witchy, now in cambridgeshire.
--
cheers,

witchy/binarydinosaurs


When you switch the light on both sides of the switch are at the same
potential - both at 240V - volmeters measure the potential difference
between two points, with them both at 240V the reading will be zero..

Measure between earth and the conductors they will both be 240V when the
switch is on and just the feed side will be at 240 v when the switch is off.