Replacing light switch

Payton

Hi all, I was replacing my sisters light switch (Kitchen/Side Extention/ Back Garden Light) from a 2 gang to a 3 gang, as the light in her extention when switched on turned on the light for the back garden so I said Id put them on seperate switches. When I opened the switch there was 3 live wires! One was the live going to the switch for the kitchen light and the wires going to the extention and the back garden light were live aswell when disconnected from the switch surley this is not normal or is there a way around it? Ive wired it back up the way it was but im looking for some advice on how to wire it as I taught the wires going to the extention and back garden light would have been switch wires??

davelerave

could be reverse polarity

shocko2009

is one of the switches 2way switched with another switch??if it is its possible that the strappers (ie..the 2 wires between the two switches) are showing up as being live!...even tho only 1 of them will be

Payton

"could be reverse polarity" is that a big job?

Shocko2009 when I opened the switch I used a phase tester to see which switch had the live wire going to it, I turned off the power removed all the wires from the terminals and turned the power back on, I got 1 live going to the Kitchen lights and the two wires (Extention and Back garden lights) were both live aswell. I hope that makes some sense

DublinDilbert

davelerave wrote: »

could be reverse polarity

I guess davelerave is suggesting that the switch could be on the neutral lines going back to the board, which is possible.

What colour were all the wires in the switch?

When you say you got a "live" reading on the wire coming from the light fitting, if you remove the light bulb do you still get a reading? With the switch removed is either of the pins in the light fitting live?

Payton

All the wire are grey with a black inner. Im getting a "Live" reading from 3 wires in the switch, I havnt tried testing the light fitting yet, but I assume you want me to check to see if it's live? I'll do that tomorrow.

DublinDilbert

on the verge wrote: »

All the wire are grey with a black inner. Im getting a "Live" reading from 3 wires in the switch, I havnt tried testing the light fitting yet, but I assume you want me to check to see if it's live? I'll do that tomorrow.

Yep see if there's a live supply going to the fitting. You don't even need to remove the switch, just switch it off... then test the 2 contacts in the light fitting with the phase tester....

intbn

on the verge wrote: »

All the wire are grey with a black inner. Im getting a "Live" reading from 3 wires in the switch, I havnt tried testing the light fitting yet, but I assume you want me to check to see if it's live? I'll do that tomorrow.

hi on the verge,
it sounds like reverse polarity you've there like davelerave and dublindilbert suggested, the neutrals(black or blue) at the switch instead of the lives(red or brown), very john wayne if ye ask me.. blue is the new colour for neutral cables but the old colour was black, like what you've got. they should be either brown(new live colour) or red(old live colour).
i'm affraid all i can offer on this suggestion front is to get it rewired by a qualified sparks.
looking forward to hearing what an experienced brightspark would do
good luck

2011

on the verge, my first question to you is how are you testing what is live ??

Are you by any chance using something like this?


"Phase tester" screwdrivers are banned from most sites because not only do they suggest that something is live when it isnt, they often say something is dead when it is live! They have resulted in lots of accidents.

davelerave

Ya.It may be reverse-polarity assuming no incoming strappers or 'false-positives' from phase tester

aujopimur

Dump the phase tester

Payton

Thanks guys, I was using a Phase tester, or do I need a Multimeter? I can get my hands on a multimeter tomorrow and I'll try it during the week.

shocko2009

try get a lend of 1,dont buy 1,will set ya back a few quid!....if your in dublin il sort the problem for ya! defo sounds like ya had cowboys in!

davelerave

Do you know what to do with the multimeter when you get it:D.you will still need a sparkie if you find a prob!

2011

on the verge:

the light in her extention when switched on turned on the light for the back garden so I said Id put them on seperate switches.

OK first of all this may not be possible to do this by only changing the switch. It depends on the way it is wired.

on the verge:

When I opened the switch there was 3 live wires!

So what you may have is:

• Wire 1 = Switch feed. This is a cable that brings a live supply from the board to the switch and feeds all other cables.
• Wire 2 = Switch wire. This may bring a supply to the extension light and from there to the back garden light.
• Wire 3 = Loop switch feed. This would give a switch feed to the next switch on the same circuit.

Or perhaps this:

• Wire 1 = Switch feed. This is a cable that brings a live supply from the board to the switch and feeds all other cables.
• Wire 2 = Switch wire bringing a live supply to the extension lights only.
• Wire 3 = Another switch wire bringing a live supply to the garden light only.

The first situation means some rewiring will be required to do what you want.
The second situation would suit you best, meaning that your goal can be achieved by simply changing the light switch.


on the verge:

One was the live going to the switch for the kitchen light and the wires going to the extention and the back garden light

Now that we know that your testing of cables was flawed you need to go back to the drawing board and work out what wire is doing what!

davelerave:

could be reverse polarity

Reverse polarity would not cause all 3 wires to be live when disconnected. 2 wires at most would be live in this situation.

Although reverse polarity is a possibility nothing described so far would suggest this is the case to me. The chances are the "phase tester" is the issue.

do I need a Multimeter?

There is no subsitute for something like this:


They aren't cheap!


intbn:

it sounds like reverse polarity you've there like davelerave and dublindilbert suggested, the neutrals(black or blue) at the switch instead of the lives(red or brown), very john wayne if ye ask me..

Just because a cable is black or blue ar any other coluor does not mean it is a neutral. Take nothing for granted! In the 1980s for example it was normal practice with domestic installations to run a 1.5 T&E (red and black cores at the time) to switches (with 3 plate ceiling roses) and the result was that black cores were used as switch wires and/or switch feeds (i.e. they are live). This was normal practice at the time and many of these systems are still in place. Years later a brown/brown cable came on to the market and this issue was resolved.

Even in the 1990s black was often used a standard permanent live colour for emergency light fittings (red, yellow and blue being the phase colours).

Now in the 2000s we are using black, grey and brown as phase colours.

The first lesson: Never assume anything when it comes to electrics! Treat everything as live until it is proved otherwise. Ignoring this advice has cost many people their lives.

Payton

I wont be buying it, I can borrow one from work tomorrow or during the week, I'll try and do a diagram or photo that might be easier.