OT : Paging the electricians

I'm trying to fit a new ceiling light and have replaced the old wall
dimmer switch with an on/off switch.There's only 1 switch in the room.
At the ceiling end are 2 sets of cables that did have the Live's
twisted together and seemed to be switched on the Neutrals.
This doesnt work with the new light and I can't get any combination of
wires to work.One of the Live's is permanantly live.
I haven't a clue as to why there are 2 sets of wires apart from
perhaps there used to be another wall switch before I moved in.
Any ideas or should I just GAMI?

Steve

 

Did the switch work with the old light?

If so then the connections at the light are wrong (he said, stating the
obvious).

From memory the way a single switch works is that you have the lighting
ring spurred to the 'connection block' in the light. The neutral and
earth are connected directly to the light (in as far as the earth is
used...). The live goes to a connection block where it goes to the
switch (so you've got the two red wires twisted together. The black
from the switch then comes back to feed the live connection of the lamp.

So the two sets of cables in the ceiling sound right for a single switch
system. The live being constantly live is the cable from the ring, the
live not live is the feed to the switch.

You're connecting something incorrectly (again, stating the obvious) or
maybe something is fucked.

Stand in a bucket of water, wet your thumb and try that in the socket in
case the bulb is fucked.

 

The wiring sounds correct.
It is a 'loop-in' circuit, where one side of the light fitting is always
live, as is one side of the switch. They get swapped around over time,
so it could be a switched live or neutral. Either way, it should still
work.
There will be 6 wires from 2 cables (or 4 wires if no earth) going into
the ceiling fitting.
One of these cables is the 'loop' which will always be live, this comes
from your fusebox/rcd, then goes to each light fitting in turn,
eventually returning to the fusebox. That means one side of the light
fitting is always live, even when the switch is off. The other cable at
the ceiling goes to the switch.
So at the ceiling, you'll have 4 connections,- the outer ones are
usually one wire from the loop cable, one from the switch cable, the
light is attached to these.
Then one of the middle connections is where the the other wires from the
loop and switch are joined together.
The 4th connection will be the earths joind together.

If you have put it back as before, then the only problem will likely to
be a poor connection, or a faulty new fitting (it happens).

It is a really simple circuit, so shouldnt be hard to trace the fault.
HTH
Alan.

 

This is slightly wrong after reading it again, if it is a loop-in
circuit, there will be 3 cables at the light fitting. It makes no
difference to you anyway, as the connections will be the same.

Alan

 

If you smell smoke, this warning has come too late ;-)

 

Join the 2 reds together with a chocolate block

One black to one side of the lampholder, the other black to the other
side.(The black coming from the switch is a switched live and should
really have a red sleeve or piece of red tape on it)

Owain

 

Switched neutral, Shirley.

 

No, it's a neutral-coloured wire but carrying the switched live. Often
two/three core is used and the black/blue is the return live from the
switch. Even if single-core is used throughout, it's not uncommon for
some lazy **** to have used reds or blacks for everything. In such cases
the live wires should be tagged with a red sleeve or tape.

 

Think it probably is a switched live. They often seem to use the normal
T+E cable with the red picking up 'live' from the lighting ring and the
switch then switches this to the black to provide the live to the light
unit.

 

Yep - my fuckwittery strikes again.There are 2 wires in the switch and
3 holes.
All sorted now

Steve

 

Excellent.

Now look at your email (assume you still read the Elefantentreffen
list).