Lighting Problem

[viciousemu]

Hi and having had a look through the forum to find an answer to my question (I couldn't see one by the way) I'd just liker to say this site looks really helpful.

In my house I have all of my lighting (upstairs and downstairs) on the same MCB. This had always been the case since I moved in and I am planning on a complete rewire (rather old wiring).

Anyway started having some problems in that the MCB for the lights would trip out randomly every now and again, sometimes a bulb would have blown and sometimes nothing that had obviously caused the problem.

There was a trip on this MCB a couple of days ago. I turned it back on and all the downstairs lights were fine, however none of the upstairs lights were working.

I am pretty competent so turned the power off, looked behind all the upstairs switches and all the upstairs light fittings. I also found a couple of JB's for the upstairs lights in the loft, they all look fine too. Finally  I also looked in the behind the 2 gang 2 way switch in the hallway as it controls the landing light as well as the hallway... I wasn't able to find a problem. It's so odd as it is just the upstairs lights that are affected and all the downstairs lights are fine, yet they are all on the same MCB. I am not convinced that the hallway and landing switches are wired correctly buy as all the wires are secure and has always worked in this configuration I have left alone at this stage.

From a perplexed individual any help or advice would be really helpful...

If it's any help I think the landing light is the first in line amongst the upstairs landing switch (only 1 gang) have the following wires:

1 yellow (switched live for hallway - connected to L1)

1 black (switched live for landing - also connected to L1)

1 blue (neutral - connected to L2)

2 red (live - connected to Common)

2 yellow/green (earth - connected to back box)

In the ceiling light fitting (not a rose but a modern multiple bulb fitting) on the landing there are:

3 red lives (all looped together in a terminal block connector)

1 black switched live (connected to live on light fitting)

1 blue neutral (connected to neutral on on light fitting)

2 earth connoted to each other in a terminal block connector)

Assuming the hallway (which works) is the last light working before the landing (which I believe is the first light in line where there are problems), I have also listed below the hallway (2 gang 2way) switch configuration:

2 red (1 connected to the top common, 1 connected to bottom common)

1 black (switched live connected to the bottom L1)

1 yellow (switched live connected to top L1)

1 blue (neutral connected to top L2)

2 earth connected to back box

(bottom L2 left empty).

I hope this is enough info...

Thanks so much in advance,

Vicious Emu.

Before I forget, I have checked all the bulbs and they are fine.

 

[Sharpend]

What work if any have you done/had done recently?

Why are you sure that it's these switches that are your problem?

Do you suffer with rodents?

 

[viciousemu]

Hi Sharpend and thanks for the speedy response.

No rodents... There was a problem with the RCD which was replaced recently (by a qualified spark). The problem with the upstairs lights occurred around 3 weeks after that. I have checked the consumer unit and the lighting radial (just one 3 core 1.0mm cable although given all the lights in the house are on this one MCB I thought a 1.5mm would be better so may have it changed in the future). Is in the correct MCB. No other work carried out. I followed the cables in the loft and it looks to me that the landing light is the first light in line upstairs. As a result of all the lights upstairs (and only upstairs is affected) I deduced that the problem would mostly likely be with this fitting/switch. I also added the hallway switch info as it does also operate the landing light.

Hope this helps.

 

[sparkytim]

Hi how many wires leave the MCB?

You say ALL the lights up and down are of the one MCB.

If so and only one cable leaves the Consumer Unit fed by this MCB then you must have a joint splitting the circuit in two sommwhere

This sounds like the most likley place for the fault to be.

 

[Evans Electric]

You sound fairly competent EMU,  do you have a mains tester of any sort ? 

Also I'm taking a guess that  you have a modern board  ( MCBs / RCD etc )   when you say "Old" wiring  ....is it black rubber cable  or grey PVC  with red/black cores .  ?  

There may be a "Borrowed " neutral  from  the upstairs to the downstairs in the loft ,...hence the sparks has put them all on the same circuit . 

You could do with a tester to see if you've lost the live or the neutral somewhere .  

 

[Doc Hudson]

From a perplexed individual any help or advice would be really helpful...

If it's any help I think the landing light is the first in line amongst the upstairs landing switch (only 1 gang) have the following wires:

1 yellow (switched live for hallway - connected to L1)

1 black (switched live for landing - also connected to L1)

1 blue (neutral - connected to L2)

2 red (live - connected to Common)

2 yellow/green (earth - connected to back box)

In the ceiling light fitting (not a rose but a modern multiple bulb fitting) on the landing there are:

3 red lives (all looped together in a terminal block connector)

1 black switched live (connected to live on light fitting)

1 blue neutral (connected to neutral on on light fitting)

2 earth connoted to each other in a terminal block connector)

Assuming the hallway (which works) is the last light working before the landing (which I believe is the first light in line where there are problems), I have also listed below the hallway (2 gang 2way) switch configuration:

2 red (1 connected to the top common, 1 connected to bottom common)

1 black (switched live connected to the bottom L1)

1 yellow (switched live connected to top L1)

1 blue (neutral connected to top L2)

2 earth connected to back box

(bottom L2 left empty).

I hope this is enough info...

Thanks so much in advance,

Vicious Emu.

Before I forget, I have checked all the bulbs and they are fine.

Blue is not going to be a neutral. if you have a neutral connected onto one side of a switch something will almost certainly blow when operating the switch. Are you sure no one has been replacing any switches and got some wires mixed up, leaving what should be a permanent live feed as a switched live feed so some lights switches are wired in series instead of parallel. What happens if you turn every switch in the house on and leave them all on. Could your MCB tripping be because you have a switch wired wrong, so it is shorting the cable when it operates? 

Doc H.

 

[steptoe]

Id agree, from a quick read it certainly sound as though your wiring connections at the switches is incorrect,

rule 1

if you have changed something, tell us,

with holding information makes it impossible to diagnose a fault easily without being there.