"Dave Plowman (News)" wrote in message
...
In article ,
alex6192 wrote:
I am trying to replace two light switches for dimmers.

Both switches are two way.

One of the switches has three wires and the other has two.

Make those cables. And the inner 'wires' are normally called cores.

Each of the wires have three inner wires (excluding the bare earth) and
they are coloured black, grey and brown. One of the main wires (the 3
wire box) has 'switched feed' written on it. All the other wires are
unmarked.

Strange. You're describing a two way switch circuit by the three core
cable - but the 'switched feed' is normally two core. Here's the diagram


L1 L1
0===========0 0===========0============= Line
| \ / |
C 0================================O C
\ / \ /
0===========0 0===========0============= Switch return
L2 Optional L2
Intermediate


The dimmer switch I have bought (which i intend to fit onto the box
which has three wires coming from it) has two L1 terimnals, two L2
terminals and two which have a symbol that looks like a wavy line with
an arrow going through it.

I've never seen one like that - what make is it? Most have three terminals
for two way switching marked Com, L1, l2.

A lot of dimmer switches use this labelling method. The "wavy line" terminal
is the Com. It is supposed to represent a dimmed connection to terminals L1
and L2


It looks to me that the existing switches are intermediates. These have
four terminals as opposed to three. As per the diagram above. If that's
the case the switch part of the dimmer will also have to be an
intermediate - and I've not come across one that is.

I'd also guess there were choc block connectors inside the boxes which
you've omitted to mention.


I do not think so. I think there is a link wire that the OP did not mention
between L1 and L1. There are many ways of wiring things this up. This is
probably the best option, and I suspect a junction box is involved
somewhere.

If you double your picture up so that it shows a two gang two way set up and
a link wire that joins L1 to L1 (not shown)

L1 L1
0===========0 0===========0=============Link to line
| |
C 0================================O C
\ /
0===========0 0===========0============= Bank 1 lights==
L2 L2



L1 L1
0===========0 0===========0============= Line======
| |
C 0================================O C
\ /
0===========0 0===========0============= Bank 2 Lights=
L2 L2

Then the 3 core and earth cable labelled "switched feed" is the cable to the
right of the picture (Line, bank 1 lights and bank 2 lights). The OP needs
to identify the permanent live from this cable(most probably the brown),
then the other two cores are the outputs for banks 1 and 2 of the lighting
circuits.


Adam