"Strange" light switch wiring

kkelly77

I was replacing a broken light switch. Took the faulty one off the wall to find 3 brown wires

2 are connected to "2 Way" and the third is in "COM".

Can anyone explain this type of wiring setup, as I was expecting the usual N E L wires? Thanks.

brightspark

Not that unusual, there are rarely neutrals present at light switches.

The reason why two wires are in one terminal is that it is the live feed to another switch.

BUT that particular switch being made of brass MUST be earthed!

As you are replacing it, you have two choices...

either replace it with a switch which doesn't require earthing (i.e. The usual white plastic ones)

OR ensure it is connected properly to earth.


The existing wires are incorrectly terminated, there should not be excessive copper visible.

Ideally the two wires together should have been in the 'common' terminal, and the single wire should be in the other terminal. (I am assuming normal wiring methods here, it is an unlikely possibility that the two wires in '2 way' are going to two separate lights and the other wire is the live feed from the distribution board)

kkelly77

brightspark wrote: »

Not that unusual, there are rarely neutrals present at light switches.

The reason why two wires are in one terminal is that it is the live feed to another switch.

BUT that particular switch being made of brass MUST be earthed!

As you are replacing it, you have two choices...

either replace it with a switch which doesn't require earthing (i.e. The usual white plastic ones)

OR ensure it is connected properly to earth.


The existing wires are incorrectly terminated, there should not be excessive copper visible.

Thanks Brightspark.

To clarify, the wire from COM is going to the light in question and the other 2 are the live in and live out (to the next switch)?

brightspark

Yes, in a typical installation that is what I would expect, but it doesn't really matter, as long as you keep the pair of brown wires that are together currently in one terminal and the other wire in the other terminal.

Bruthal

And as long as one of the terminals used is the common.

Danny Mulcahy

It is a really bad idea to replace your switch with a brass/metal switch unless you get an earth to it.

Is there a metal or plastic box behind the switch..If metal you really need to get an earth

kkelly77

Danny Mulcahy wrote: »

It is a really bad idea to replace your switch with a brass/metal switch unless you get an earth to it.

Is there a metal or plastic box behind the switch..If metal you really need to get an earth

Metal dry line box and it is earthed

Danny Mulcahy

kkelly77 wrote: »

Metal dry line box and it is earthed

Your ok so.:cool:
Just a fly earth needed off the box to earth the switch

karldel123

Hello

Can anyone explain to me about a 3 gang switch. I had a clown remove the switch from the wall without labeling where the wires should be re-connected.

It is a 3 gang switch, all the cables are still in the switch as they were previously connected into connector strips. It has A1 A2 B1 B2 C1 C2 and 3 COMs (A,B,C). The 3 COMs are looped and there is an extra wire coming from the C COM. There is a wire in A1 and C 1 and then there is a wire in each of the Bs (B1 & B2). The switch controls 3 different lights, first switch controls a lamp on one side of a bed, the middle switch controls the main room light which also has a switch at the door, and the 3rd switch controls another lamp on the other side of the bed.

On the connector strips I have only found 1 constant live. Should this be connected to COM?

See attached pictures

I am also aware that wrong colored cables are being used. I can change these if I could just figure out what is doing what on the switch.

Any help is appreciated.

Thanks

brightspark

Yes the constant live would normally be in the COM

karldel123

Cheers Bright Spark,

And I take it the reason it has a wire from B1 and B2 is because that light is also controlled from another switch?? Am I right?

Danny Mulcahy

That earth cable should not be used as a switch live cable.if there is still an earth at the switch it could be used but should be sleeved in brown.
At a glance it looks like Your lights where wired incorrectly.

It would be worth calling an electrician to look over your wiring .

brightspark

Yes a 2way circuit involves using 'strappers', so both B1 and B2 are used

An explanation here

http://www.wellwhataboutthat.com/html/diy_tip_-_how_to_wire_a_2_way_.html


Where did the blue wires in your photo of the switch come from?

And the earth wire??

Only the 5 brown wires you have in the connector are usually needed for the circuit you described.

karldel123

I know the cables used are wrong, i will be changing them when I figure what goes where. that was what the witch looked like when I found it.
There is no earth at the switch,

karldel123

Hi Brightspark,

That is exactly how I found the switch, I reckon who ever done the job originally hadn't enough brown cable left and/or was too lazy/stupid and used what ever was left over at the bottom of his tool box.

brightspark

Can you clarify, the photo of the switch shows wires in the various terminals, are they connected to the lights or what? It looks like the switch is on a table?

Bruthal

Yea it looks like any available pieces of wire were used to connect the switch to the connector-terminated lighting switch feeds, wires, and strappers.

karldel123

yes bright spark the switch is just on a table at moment. A decorator took it off completely when he was wallpapering but didn't bother to mark where each cable should go back. at the moment the cables are going nowhere. I just left them in terminals to post the picture here

brightspark

So the wires currently connected to the switch aren't connected anywhere else?

If so, it looks like he did mark them in an odd way, each colour probably represents a different wire on the connector switch.

Also could you take more pics of the wires at the connector, it's probably the lighting but one of the cables looks damaged?

Also that screw attached to the light switch looks wrong!

Bruthal

Anyway, very simple for any electrical person to sort. Not so easy to give what would require a detailed description of tests to determine what is what in the connector.

But to find the live feed in the connector strip, and connect it to each of the other connectors, 1 at a time, to find which ones bring on each of the lights on each side of the bed.

So the live feed then connects to the looped commons on the switches.

One connector for the bed side lights connects to where the green/yellow is, the other to where the brown on its own is, and the remaining 2 in the connector should be the 2 way strappers and they go where the 2 blues are.

Thats how it looks anyway from the limited photos. As I said though, ultra simple for electrical fella there with a meter (or piece of bridging wire) to sort it in a minute or 2.

karldel123

Yeah the cables are not going anywhere at the moment.

Are you talking about the 2nd cable from the bottom that looks fatter than the others? this a brown sleeve over the cable.

Yeah that screw was another pleasant surprise I found. I think it was just left there and never taken out, you know how the switches always include screws at the back when you buy them. The screws that were in the face plate are actually longer ones so I reckon this screw just wasnt taken out. I have removed it now anyway

karldel123

Bruthal wrote: »

Anyway, very simple for any electrical person to sort. Not so easy to give what would require a detailed description of tests to determine what is what in the connector.

But to find the live feed in the connector strip, and connect it to each of the other connectors, 1 at a time, to find which ones bring on each of the lights on each side of the bed.

So the live feed then connects to the looped commons on the switches.

One connector for the bed side lights connects to where the green/yellow is, the other to where the brown on its own is, and the remaining 2 in the connector should be the 2 way strappers and they go where the 2 blues are.

Thats how it looks anyway from the limited photos. As I said though, ultra simple for electrical fella there with a meter to sort it in a minute or 2.

I know which one the connectors is the constant live, so connect that to COM and then go from there with each other one until I get the correct right switch for each light yeah?

Bruthal

karldel123 wrote: »

I know which one the connectors is the constant live, so connect that to COM and then go from there with each other one until I get the correct right switch for each light yeah?

For the following,, Switch off MCB for each swap.

Get a piece of wire. Connect it between the constant live and any other wire in the connector. Note what light comes on. Note it on paper clearly.


Do same for all other 4 wires. One will light one bedside light, another will light other one. Another will light main ceiling light. And the other will light nothing, (which is due to the way 2 way wiring works)

Once you determine, and very clearly make a diagram of connectors and what lights what, you can continue. You really only need to find the 2 wires that light the bedside lights. These will then leave the 2 wires which are the 2 way pair for ceiling light. These 2 go where the 2 blues are on the switch in the photo.

Get one bedside light wire, connect where the earth coloured wire is. Get other one, connect where the single brown is on its own. Do this using intuition as to which switch you want to do which light.

Connect the live feed to the common loop.

brightspark

Make sure you don't leave any exposed live wires when testing (or indeed when finished)

If I had no meter I would turn off the feed MCB, the put a link from your identified live connector to one of the other connectors and observe if a light comes on, then turn off the power and try next connector, and repeat until all have been done. (Or at least until you have identified the ones supplying the bedside lights)


As Bruthal has said you need to identify the two bed side lights, then by elimination the other two are the strappers for the two way switch, and it doesn't matter what way round they go.

!!!DONT FORGET TO TURN OFF THE SUPPLY BEFORE WORKING ON ANY OF IT!!!!


Typing on an iPad is slow. Bruthal explained it well.

karldel123

Cheers Lads,

I will give it a go, Thanks for all the info!!

Danny Mulcahy

Be sure the tighten the terminals.
You need to bend the conductor over itself(double it up)

If you dont you can over tighten it and they will snap(a potential fire situation)

Someone that isnt qualified doesnt know the simple things that are common knowledge and common sense to someone in the trade.

It is worth leaving some jobs(no matter how simple they seem) to the professionals.

Not typing this in a vex or rude manner....Just my thoughts on it:)

Bruthal

Yes even the very simple electrician things are done wrong by diy`rs

karldel123

I got it working. Tried what you said Bruthal and Brightspark and its all working ok. All switches are doing what they are supposed to be doing and no sparks/burning smells/tripped breakers!!!! Thanks for your help!!