I seem to recall reading somewhere that in 2 way switching for house lighting its a good idea to have a neutral wire parallel to the lives to cut down on interference, is this so? In which case I need 4 core and earth not 3 core and earth.
I is mentioned at:
ting its a good idea to have a neutral wire parallel to the lives to cut d own on interference, is this so? In which case I need 4 core and earth not
3 core and earth.Paul1966
Posts: 1538 Joined: 21 December 2004
The key point is that whatever current flows in one direction along a condu ctor in a cable should also flow in the opposite direction along another co nductor in that cable.
In a single 2C(+E) cable running to a light, the instantaneous current at a ny moment in L is counteracted by an equal current in N flowing in the oppo site direction. In a 2C switch loop, both conductors are live, but the inst antaneous current flowing to the switch at any instant in time is balanced by an equal current flowing in the adjacent conductor back from the switch.
This principle just extends to 3C cable and multi-way switching. You might have three conductors in the cable, but for any given combination of switch positions only two will be carrying current, and those currents will be fl owing in opposite directions.
DICEGEORGE was thinking very hard :
I think you may be looking at the now illegal 'Carter' method. Yes, interference during switching can be reduced by running 'flow' and 'return' wires in close proximity, but the difference is slight and light switching is not frequent anyway. Mostly a home will not be wired with live and neutral co located along their length anyway.
Network and phone cables use twisted pairs and are used as pairs, so as to avoid interference generation and pickup of interference affecting the signal. What is picked up (or radiated) by one wire, is cancelled out by its opposite number.
No. Because your 2 or 3 wires to the switch are already balanced - current down to the switch = current back up from the switch.
so if 3CE is good enough for 2 way switching is 4CE ever used in a normal-ish house?
[george]240v Room Thermostats e.g. Controlling UFH zones
What sort of interference are you talking about?
You might also find it very difficult to obtain 4 core and earth. I've never seen it in terms of house wiring.
But if it is a problem on a two way switched circuit, it would also be a problem on the common way to wire lighting with a switch drop from ceiling rose to switch.
not for lighting, perhaps for heating.
Hmm, cannot see that myself. Without screening and stuff like that switch impulses will just radiate in my experience.
Brian
With all the incredibly noisy switch mode supplies and powerline internet adaptors around nowadays, I think most houses need wiring with screened cables and possibly undeground as well! Brian
I have only ever used the "Alternative method of Two Way Switching" on that page .. adding intermediate when needed
Normal houses ... only 3c+e
Why? It doesn't cause a problem here. And I'd guess I have more AV equipment than most.
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