Old 2 way switching

[Robert Turnbull]

hi, i though someone on here might have a quick answer to this.

I've been called to a house because the builder has changed the face plates on the switches for the hall landing and now the lights are not working at all.

I only had a quick look, and this is what i found.

1 x hall light
1 x landing light
2 x gang switch in hall
2 x gang switch on landing

3 x 1.5 2 core cables at each switch, NO 3 cores

their is a 1 cable in each switch and the third cable has a core in each switch. I have never seen this before so i saw slightly confused so i thought id get some advice before i pull it all apart. what isn't helping is the customer said the 2way didn't work properly. so i don't know if this is ever going to work or someone had messes the connections up before. Also the cable has no earth making it hard to identify the live conductors. i did have a try with a test pen but it was picking up live on everything due to the confined nature of the switch.

Can anyone shed any light on this. i has hoping it was a old style of 2 way that ive not encountered.

thanks

Rob

 

[Plonker 3]

You need to bell the cables out to prove which one is which, you don't need a CPC to do this just simply short any 2 cores out of the same cable and ensure the other cables are clear.

Once you have established which ones are which then you should be able to determine if it is possible to 2 way the lighting up. It sounds as though you wont as there will at each switch be a switch wire and 2 twin and earths between them which should be 3 core and earth.

 

[telectrix]

first, check at the 2 way light rose to see if it's looped in there, or at a JB in the loft. then it's a case of belling out the cables. ytou'll quite likely find that the l feed comes from downstairs circuit. often referred to as a borrowed N. if it were my job, i'd be looking at installing a 3 core between switches and reconfiguring the wiring.

 

[Robert Turnbull]

i'm going back prob on the weekend i will have to bell it out, thought i might be able to save some time as all the builder did was to change the plates so he will have just got somthing wrong. so it will be a expensive i was saying about no earth meaning i can't put a tester to read a voltage to dertermine the feeds. I dont think they are overly bothered about having the 2 way work, especially as the builder has just finished decorating and wall papering the landing and hallway. They will just want them to work i think. i thought this config might be a old style

 

[StuSpiers]

just bell the cables out.

You need 2 X strappers
1 X feed
1 X switch wire for a two way system.

It has been like that from year dot.

 

[telectrix]

it might simply be that he's missed a L link between the 2 switches in the hall. what you need to do is short each cable R/BK then bell out. with no cpc, make sure everything is plastic. you should find that the back box lugs are nylon. if metal lugs, use plastic faceplate screws.

 

[Robert Turnbull]

its 2 '2 way' systems together thats confusing me. i only spend 10 min on it as it was fathers day and had my boy with me. i happened to be in my van in the area when he called. thought i might sort it in a few mins.

To me there is not enough cables for 2 systems, but if the feed is taken across there might be, but i see i am just going to have to bell it all out. what i ment was its going to cost the builder now for my time.

nothing is linked in the switches, should it be?

 

[telectrix]

when the strappers are just 2 core, it was usual for the L feed for the landing light to be obtained from the hall switch using a link between the commons. so yo have a L tro the common of both switches downstairs, strappers from L1 and L2 in the second switces, then L to the lights from the commons of the second switches

 

[Richard Burns]

They could have done interesting things using a junction box or a light fitting to take a S/L back downstairs and, if the lights are on different circuits, using T&E to carry two lines to the switch as in the diagram below.

This would be one arrangement whereby you have 3xT&E in each switch with one cable having one core going to each common, however the problem with this is that this would work.
However this is just me thinking about possibilities and the best way to test is to bell out the cables.
Also check what cables you have at each light fitting, this may make it clearer (or totally confuse!!)

 

[spark 68]

What I have come across before is where the installer has used two T+E cables instead of a single 3+E, usually doubling up the blacks at the common.

Just a thought.

 

[shocking_eg]

since these have no earths whats the chances this "builder" has installed metal switches

 

[ample current]

I have come accross something like this. The upstairs light was powered up by the live taken from the downstairs dining room light,(From switch on other side of wall from stairwell) and the hall light was powered from the landing light. so only had 4 conductors.(2 sets of 2 strappers)

 

[nickblake]

beware of the shared neutral always a possability on a circuit like this

 

[needasparks]

Not sure in your case but can only say round my way this was very common for early seventies to have normal L/SL at each switch and two pairs of strappers and does indeed have borrowed neutrals, no links are required as up live does down and down live does up.
Load on one common and feed on the oposite. hope this helps.

 

[ackbarthestar]

I simplified bathroom/office lighting for a client yesterday. No borrowed neutrals, cpcs in place all in T&E except for one obvious 3-core conversion and a fan connection in a JB. But it did look quite busy inside the deep single boxes

Switch 1 (2-ganged) controlling bathroom light (no 1) using 2 way and fan via JB
L-N * 1
Strappers * 1
L-Sw * 1
N -Sw * 1

Up to JB (20A 6way)

L-N * 3
L-Sw * 1
L-N-Sw * 1
N-Sw * 1

Switch 2 ( 3-ganged) controlling two bathroom lights 2-2way (no 1,2) and second 1 way bathroom light (no 3)

L-N * 2
Strappers * 1
L-Sw * 1
3-core * 1
N-Sw * 1

Its not particularly difficult to sort out. The key is not to get flustered and take each pair at a time. You can anticipate what should happen at each switch plate So start by drawing what you think might happen.

1/ Find the live feed and Neutral from the CU
2/ Identify the Lives and switches
3/ Identify the strappers (that's the easy bit)
4/ Identify all the Neutral and switches
5/ Check that there are no class I fittings if using Twin cables

Whatever you do. (state the bleeding obvious) do not switch the neutrals