"John Rumm" wrote in message
o.uk...
dennis@home wrote:


"John Rumm" wrote in message
o.uk...
dennis@home wrote:

Not really - even wiring to the 17th edition using the "standard"
arrangement with 3&E run between floors to facilitate the "other" two
way switch, you will still have a switch position containing live
wires from two separate circuits.

Why?
You have live running to the top switch, two switched lives from the
top switch to the bottom switch and one switched live running back to
the fitting, only one live circuit is needed and no neutrals run down
the cable at all. Operating the switches will either turn the light on
and off if the wrong circuit is isolated or do nothing.

And that means the bottom two gang light switch has lives from the
upstairs and downstairs circuits. (and the upstairs likewise if two way
switching is implemented in both directions).

If its a two gang then the lives can come from any circuit, there isn't a
rule that says otherwise.

The live must come from the same circuit that the neutral returns two.
This normally means that the light on each storey will connect to the
neutral belonging to the circuit feeding that storey, hence the live needs
to come from there also.

I have drawn an example of double two way switching using the 17th (and
16th for that matter) edition recommended way of wiring two way switches
he

http://wiki.diyfaq.org.uk/index.php?...tching_circuit

No borrowed neutrals (so RCBO safe), feed to each lamp from the adjacent
circuit for the storey, but two circuits live conductors present at each
two gang switch.

That's how I do them.