Problem replacing switch...

[londondiyer]

I have started, what I thought would be a simple task... which has gone wrong, and I hope one of you guys can help... to follow is as much info as I can think of...

I wanted to replace 2-gang dimmer switch in the lounge, that the switch buttons had fallen off of - and which was ugly... I want to replace it with a normal one way 2-gang switch, not a dimmer; The first switch controls a wall light on the same wall as the switch, the other a pair of wall lights on the opposite wall - the room has no ceiling lights

Firstly.. When turning off the power I found this wasn't part of any of the lighting circuits on the fuse box (do I assume that this is running off of the main ringmain, that the sockets run off of?). I turned off the power through the main switch on the fuse box...

This is where I made my mistake, I took off the dimmer, and didn't draw a plan of where/how the cables were wired... what I do know is:

1. there are three cables in the box, both with one red, one black, and an earth in

2. the earths are all wired into the metal box - the original switch was also earthed from the box, as it was metal, however, the new switch is plastic, so I'm fine with that

3. the original switch was strangely configured (which is why no diagram was an error), this is what I know/recall
- the three black wires were seperated, and just put into a single terminal block, and not connected to the switch in anyway
- the three red wires were connected to the dimmer switch, two in one place, one in another
- in addition there ws a length of cable, with a black sleeve, that went from one 'gang' to the other

As I said, I stupidly removed the original switch, and didn't draw a plan of where/how the cables were wired. I tried to wire up the new switch, trying several different configurations for the wiring, and have had no joy - each time I switched the power back on, nothing

I tried another switch to, in case it was a faulty switch, but it wasn't

Any help would be appreciated...

 

[ban-all-sheds]

Either your lighting circuit loops through the switch (see the last drawing here: //www.diynot.com/wiki/electrics:lighting-circuit-layouts) or the switch was wired by a numpty who didn't know to use the black as the switched live.

But it makes no difference - leave the blacks connected, put the permanent live into one COM terminal and link that to the other COM. Put the other 2 reds into the L1s.

You'll need either a multimeter or an electrician to identify which of the reds is the permanent live.

 

[pjcomp]

Three earths to back box - fine.
Three blacks (neutrals) together - fine.
Of the reds, one is the incoming power, the other two go to the lights. You now have to find out which is which, and if you don't have a test meter and know how to use it I'm not going to suggest the trial and error method!
When you find out which is which, the live feed goes to one of the switch terminals labelled COM. The other two go to the terminals labelled L1, or one-way, or similar. You then need a connector wire between the two COM terminals.

pj

 

[sparkwright]

All three blacks in terminal block.

Find the one red that is live, ie the permanent feed. Put this in a 'common' terminal, then run a short red link from here to the other 'common' terminal.

Put wall light red in a terminal marked L1.

Put remaining wall light red in the remaining terminal marked L1.

Leave both L2s empty.

You may have different switch markings;
Common = L1
L1 = L2
L2 = L3

Common, L1 and L2 are the most usual.

 

[londondiyer]

Thanks guys, I think I understand now... (it seems a diagram would have solved all this!)

One further question... without a two pronged tester, and not being keen on using the neon screw driver, would using 'trial and error' (ie swithcing off the power, and trying the three reds in each of the possible combinations) be dangerous/damaging in any way

I note that one response said if you "don't have a test meter and know how to use it I'm not going to suggest the trial and error method"

could I actually test using a single gang switch? leaving the black wires in the terminal block... and putting one red in one end, and two in the other end...

thanks again for all your invaluable help

I have the time, and am happy to walk back and fourth to the fuse box, it's not far!

 

[EFLImpudence]

.
If I may interject with regard to recent discussion.

Other posters may note that all three of the above replies state that the Live conductor is placed in the Common terminal.

 

[sparkwright]

I suspect the feed wire wouldn't have the end doubled over, as it has to share a terminal with a link.

It's possible the other two wires have their ends doubled over.

The trial and error method you propose wouldn't cause any diastrous effects, providing you don't work live and you work safely.

 

[ban-all-sheds]

Don't do trial and error.

Get some common sense and get the right tools you need to do the DIY jobs you want to do.

I assume you use screwdrivers to deal with screws, not the points of knives? A hammer for nails rather than a lump of rock?

If you want to work on your electrics a multimeter is essential.

 

[londondiyer]

hello

thanks for all your help yesterday, unfortunately, I haven't solved my problem...

I waited until daylight, so I could see what I was doing, bought a multimeter... tested multimeter on a socket, and it works fine...

tested the cables for the switch in question, and nothing...

- earth wires untouched, and earthed, together, to box
- black wires all together in terminal block

Tested the red wires and no reading at all..
- tested the reds in pairs, nothing
- also tested each red in turn, with the terminal block for the black wires, nothing

What can I have done? I have looked at fuse box, everything fine, I've even used the test function on the fuse box, and everything seems to be working fine...

If checked the bulbs, they haven't 'blown'...

I'm wishing I hadn't touched the original dodgy/ugly switch!

 

[EFLImpudence]

also tested each red in turn, with the terminal block for the black wires, nothing

You did have the power ON didn't you?

Meter on AC V - ONE of the reds should be 240V ish to the blacks (and earths)

 

[londondiyer]

yes, power was on...

meter set to AC (250), and as I said, it worked as expected/desired in a socket...

when you say 'and earths', what do you mean, should I be doing something with them, or just leaving them earthed to box?

I have now put the three reds together, in a terminal block, to keep them safe and out of the way, and put a blank plate on the box... which to my mind should mean both sets of lights will be on permanently? but they aren't...

I am assuming, therefore, the circuit has somehow been damaged/disrupted, but I can't work out how, all I have done is taken off a switch!

aggghh!

 

[EFLImpudence]

when you say 'and earths', what do you mean, should I be doing something with them, or just leaving them earthed to box?

No, that is correct but the voltage reading between L & N and L & E will be the same.

I have now put the three reds together, in a terminal block, to keep them safe and out of the way, and put a blank plate on the box... which to my mind should mean both sets of lights will be on permanently? but they aren't...

Yes, they should be on.

I am assuming, therefore, the circuit has somehow been damaged/disrupted, but I can't work out how, all I have done is taken off a switch!

It would appear so.

aggghh!

Quite.

 

[sparkwright]

In the first post there was some uncertainty about which circuit was feeding the lights.

If the lights were fed from the socket circuit I would expect there to be a switched or unswitched fused spur unit somewhere before the light switch.

There may be an RCD somewhere that may have tripped.

Either way, make sure no bare wire ends are left exposed.

You could test your test meter on a known live source, assuming you are competent to use it - absolutely no offence intended here by the way.

 

[londondiyer]

hi there sparkwright, thanks for your reply

I tested the meter on a socket, and know it works - no offence taken by the way!

That's right, these lights aren't on ayt of the 'light' circuits, as I switched them all off, and they were still lit... I could only switch them off throwing the main switch...

If we assume that "the lights were fed from the socket circuit", where might the "switched or unswitched fused spur unit somewhere before the light switch", or "RCD" be found? are they likely to be in a wall, or under floor boards... or near the fuse box? (but not part of the fuse box)

This is an old house, and this is another random thing we have found that's a pain in the arse!

Sorry to be such a pest, and thanks for all your help...

 

[sparkwright]

If there is an RCD I would expect it to be in or at the consumer unit.

If there is a fused spur unit I would expect it to be near the switch, somewhere between the switch and a nearby socket. Behind a piece of furniture perhaps.