Need help with 2 way switching.!!!!

michal_p@tiscali.co.uk · Nov 3, 2008

I know it doesnt sound very serious but I urgently need a wiring diagram
of two way switching in UK's old councill house.

This is one of the systems where every one way switch has three live wires in it.
I know how it works but have no idea how 2 way switching is organised in system like that.
What I have is two switches with three wires (red) in each. One rose with one phase (red) wire.
When circuit is powered all wires in switch boxes are live at the same time (all six of them) but the one in ceiling rose is not. Maybe I should say not quite live

. Saying not quite I mean that voltage between neutral and phase is 35V

. And I'm absolutely sure as I've checked twice and even got my FLUKE tester to confirm this strange reading. FLUKE said 40V.

Has anyone had situation like that before.
1) Any ideas what may cause such tremendous voltage drop?? Distance between rose and CU is less than 3 meteres. I,ve already checked all roses for loose connections.

2)Any links to diagrams of this kind of system?

Thanks for any help

WarrenG · Nov 3, 2008

[email protected] said:
I know it doesnt sound very serious but I urgently need a wiring diagram
of two way switching in UK's old councill house.

This is one of the systems where every one way switch has three live wires in it.
I know how it works but have no idea how 2 way switching is organised in system like that.
What I have is two switches with three wires (red) in each. One rose with one phase (red) wire.
When circuit is powered all wires in switch boxes are live at the same time (all six of them) but the one in ceiling rose is not. Maybe I should say not quite live . Saying not quite I mean that voltage between neutral and phase is 35V. And I'm absolutely sure as I've checked twice and even got my FLUKE tester to confirm this strange reading. FLUKE said 40V.

Has anyone had situation like that before.
1) Any ideas what may cause such tremendous voltage drop?? Distance between rose and CU is less than 3 meteres. I,ve already checked all roses for loose connections.

2)Any links to diagrams of this kind of system?

Thanks for any help

Michal,

It sounds to me that you need to find the live at the first switch being feed out of the three. Two of them are just strappers from one switch to the other. Try to do some dead continuity testing to see what is what.

Here's a link I hope it helps!

http://i3.photobucket.com/albums/y63/the_jinj/1and2way.jpg

Warren
http://images.google.co.uk/imgres?i...q=two+way+switching&gbv=2&hl=en&sa=G&ie=UTF-8

michal_p@tiscali.co.uk · Nov 5, 2008

Thanks for that.
There si still however question about this voltage drop.
Has anyone any idea (relted to this situation or not) why voltage can be down to 40V?? Except for extremely long cable run of course.
Thanks for any thogths on this subject.

jeremy · Nov 5, 2008

I would hazard a guess that the 30-40V you're getting is induced by running alongside a cable carrying 230. Are these singles in conduit ? Take the rose down and find any wires behind it . Power down and with a continuity tester ID each conductor then reconnect as appropriate. If the ceiling live isn't then I reckon ther's a disconnected joint, and can someone tell me how to get rid of this slanty writing. I accidentally hit a button and I don't know which one!!

DanBrown · Nov 5, 2008

Its not voltage drop, and as for induced a.c. sounds very unlikely unless in a large factory/commerical building with bundles of 230v cables running parallel. For me i'd say a bad neutral somewhere as iv'e comes across this a few times before.
Try doing a voltage check between live and earth and hopefully get 230v, and then back to live and neutral test. If you get 35 volts or so, put it down to the neutral conductor and do a resistance check (if an old building with old wiring you could also do an IR check).
Hope it helps.. Let us know how you get on...

Scotty · Nov 5, 2008

Looks like you hit control + i rather than shift + i

DanBrown · Nov 5, 2008

Scotty said:
Looks like you hit control + i rather than shift + i

What you mean??

Scotty · Nov 5, 2008

Pressing Ctrl and i at the same time on the keyboard sets italic mode, I do it myself when I mean to do shift and i to get a capital I.
I just thought that is what you had done, absolutely no relevance to the electrical question but you did ask.

WarrenG · Nov 5, 2008

Michal,

At which position is the red cable in the rose?

I would try and track the red wire in the Rose. Try a continuity test to see if you can identify it at the first switch?

jeremy · Nov 5, 2008

Many thanks Scotty for the advice on my sausage trotters!!. I've measured induced V on cpc ( not connected in the board) of 103V. Once properly connected Induced V goes away. I'm told by my old physics teacher that induction relies on the amount of influence of enegised cables on cables with nowhere to go to. Still, could be wrong, I usually am

michal_p@tiscali.co.uk · Nov 10, 2008

thanks for all your answers.
I've solved already a problem and this is what I have found.
1)I don't now why but this strange voltage seems to have been caused by cross connecting two diferrent circuits. What I mean is that somebody used live(phase) wire that belonged to one circuit and the neutral to the other.
Technically I still don't understand why it produced 35 V but the fact is that after correcting it everything is back to normal.

Theory with induced currents is not however without basis. As I mentioned
at the beginning I had two light switches 3 wires in each and all of them life at the same time. After closer examination I found that some of them were voltages at around 25 V and they disappeared after I powered down other lighting circuits. These are single cables running in metal conduits

Thanks for all your answers guys.
Michael

fengine · Nov 10, 2008

Got this info off other sites

Capacative coupleing between the switch feed and the switch wire becuase the two way strappers connected to them which probably run together for a fair few metres without a cpc between them.

Lighting circuits can suffer from unwanted capacitive coupling between live and switched live cores which, if it's big enough, can cause low energy lights to flicker. An earth wire between the live core and the switched live(s) will shunt the leakage away to earth ---- BUT ONLY IF YOU EARTH IT.

A cfl at the lamp holder will flash a bit as the capacitors inside it trickle charge through the cableing, the lamp will try and strike, it will then go out and the cycle starts over, connect a high impedance voltmeter there instead and you'll get some voltage between 0 and 230, which will vanish as soon as any sort of real resistive load is connected