Switch problem


Postby bristol » Wed Jan 05, 2011 4:21 pm

Hi everyone

I have a house which has had the kitchen and dining room knocked into one.
The previous owner therefore installed a double lighting switch in the dining room area, which controlled the lights in both the former dining room and the kitchen.
In the kitchen, what I presume to be the original switch remained and controlled just the kitchen light.
All this has worked since 2005 until last week, when clearly a 'disconnect' of some sort happened.

The dining room switch still lights the dining room area, but not the kitchen.
The kitchen switch still works there HOWEVER - when the dining room switch is used for the kitchen, the kitchen light will not work via the switch there until the dining room switch is turned to 'off'.

I checked the kitchen light and all is connected as before, as is the kitchen light switch. However, when I unscrewed the dining room double switch it looks like a neutral wire has come loose.
This switch has 3 cables coming into the back box, all with LNE. The 3 Earths are connected to an earthing block in the box, the 3 lives go individually into 3 separate connection points in the switch and 1 neutral goes into the other one. One of the other neutrals is cut and is tucked up in the box, whilst the other as I say, appears to have come loose.
I thought that maybe the loose neutral should be placed with the connected one, but all this does is leave the dining room light on permanently.
I have placed insulation tape on the offending wire in the meantime, but does anyone have any thoughts please?

Cheers
bristol
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Postby BLAKEY1963 » Thu Jan 06, 2011 10:21 pm

[quote="bristol"]Hi everyone

I have a house which has had the kitchen and dining room knocked into one.
The previous owner therefore installed a double lighting switch in the dining room area, which controlled the lights in both the former dining room and the kitchen.
In the kitchen, what I presume to be the original switch remained and controlled just the kitchen light.
All this has worked since 2005 until last week, when clearly a 'disconnect' of some sort happened.

The dining room switch still lights the dining room area, but not the kitchen.
The kitchen switch still works there HOWEVER - when the dining room switch is used for the kitchen, the kitchen light will not work via the switch there until the dining room switch is turned to 'off'.

I checked the kitchen light and all is connected as before, as is the kitchen light switch. However, when I unscrewed the dining room double switch it looks like a neutral wire has come loose.
This switch has 3 cables coming into the back box, all with LNE. The 3 Earths are connected to an earthing block in the box, the 3 lives go individually into 3 separate connection points in the switch and 1 neutral goes into the other one. One of the other neutrals is cut and is tucked up in the box, whilst the other as I say, appears to have come loose.
I thought that maybe the loose neutral should be placed with the connected one, but all this does is leave the dining room light on permanently.
I have placed insulation tape on the offending wire in the meantime, but does anyone have any thoughts please?

Cheers[/quote]

BRISTOL
One would need to have knowledge to distinguish if your blacks are neutrals or not , because they could be black switch wires .
You might be wise to get in an electrician to help you with this.

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Postby bristol » Sat Jan 08, 2011 8:13 am

Thanks Blakey - would any of the black cables act as neutrals?
I presumed that the clearly connected one was a neutral.
If the loose black cable is actually a switch, where should it be conected?
I never work with the power on of course so how dangerous would it be to trial and error, eg connect the loose black wire to the connected red ones in turn?
I presume it sat with one of them, although all of them appear tightly connected so how this wire got loose god only knows.
As I said earlier, when I connected the loose wire to the other black one, all that happened was that the dining room area light stayed on permanently.
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Postby ericmark » Sat Jan 08, 2011 3:06 pm

A while ago I tried to carefully word together detailed instructions on how to test wires in a ceiling rose with nothing more than a screwdriver to find out which was the switch wire.

However, two things one the non-electrician who tried to follow the procedure did not follow to letter, was unsuccessful in tracing the cables. Plus, second, an electrician complained that I had given dangerous information and I was banned from this site.

In some ways he was correct. To try to get some one to follow a whole string of instructions without making at least one error is asking for mistakes to be made.

The problem is two fold. If a line and neutral are connected together the fuse or MCB should auto disconnect the circuit. But it does not auto disconnect straight away there will be some time even if only 0.1 seconds and in that time one can destroy the light switch. Secondly it could create a borrowed neutral situation which in turn could result in some one getting a shock at a latter date.

The only way to safely trace the wires is with the power off and using some self powered testing device.

We refer to it as belling out and this is because years ago we would use a door bell unit and the two wires that would normally feed the bell push would be out two test probes. Today many multi-meters have a built in buzzer and no longer do we use a bell.

When you say “One of the other neutrals is cut and is tucked up in the box” that makes me think it would have been wired as a two way switch and rather than running triple and earth between the switches two separate cables have been used. I will guess you will find in the other switch of the pair it also has “One of the other neutrals is cut and is tucked up in the box”.

Since in a switch box it is likely there are no neutrals and most the black cables are return wires feeding the lamps. However one pair likely goes to the other switch of the pair. And you need to find out which pair of wires this is.

Two way switching does not normally work as taught in school. The method taught in school would form a large induction loop and cause a main hum on radios etc. So where the switch is marked Com, L1 and L2 at the switch directly connected to the light there will be two wires in the L1 and L2 and a single wire in Com. The two switches are connected together like for like so L1 on one switch goes to L1 on other switch of pair.

You should find this all as diagrams on projects section.

Although I can give the pointers as above I can’t tell you how to repair and of course no one but you knows how good you are at electrics. But since you seem to think all black wires are neutrals and also who ever wired your house has not it seemed put the ID sleeving on the wires to show which are Line and which are Neutral I would suggest maybe it would be safer not to DIY.

You may find other forums where you can post pictures but be ready for some stick as other forums don’t have the gentlemen found on this one.
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Postby BLAKEY1963 » Sat Jan 08, 2011 10:29 pm

BRISTOL
There is a possability the black wire could be a switch wire on
the live side , but even with power off you would need a continiuity tester set on omhs to do an r1 + r2 test , to verify the polarity of the black wire ( in your case neutral or live conductor ).
Testing the stray core , would prove the polarity , and then you wouldnt be guessing as to what the cable is.
An electrician would Have the test gear to do this for you if you dont have a continuity tester. To just assume and reconnect is not really the thing to do if you dont have the knowledge to work safely.

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Postby bristol » Fri Jan 14, 2011 3:06 pm

Thanks Blakey and ericmark

I think it was spelled out to me quite clearly - you don't mess around with electrics!
My son has a mate who's an electrician so he's coming over on the weekend.
Thanks again to you both.

Regards
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Postby BLAKEY1963 » Sun Jan 16, 2011 12:19 pm

[quote="bristol"]Thanks Blakey and ericmark

I think it was spelled out to me quite clearly - you don't mess around with electrics!
My son has a mate who's an electrician so he's coming over on the weekend.
Thanks again to you both.

Regards[/quote]

BRISTOL
Hope your electrician sorts things out for you.

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