Lighting cicuit issues

[Glynk71]

Hi all, I'm looking for some advice. This morning there was an audible thud and the lighting breaker tripped. I reset it and it did it again after 10mins or so. I reset it again and now only the first light in the circuit comes on. The lights are daisy chained, I inspected the wiring in the working light rose and all is OK. What is the next step in troubleshooting. We are isolated and with 10 inches of snow it will be after the thaw to get someone out. Thanks in advance Glyn.

 

[mainline]

A bit more information is needed.

Are we talking about upstairs /downstairs or all.

If only the first light in a string/loop is working, then it suggests a break in the wiring could be due to rodents ?

Have you checked other roses ?

 

[Glynk71]

Thanks for replying. The whole house is on one circuit. The light in the cupboard under the stairs is working but no others. I assume the next one in the chain would be the living room logistically which I haven't looked at yet. The neutrals i believe run to a jb on the landing.

 

[ProDave]

Too many variables to make much sense of it, but start WITH THE POWER TURNED OFF opening each light switch in turn and looking for wires out of the terminals. Then check all the light fittings.

If nothing obvious at the fittings or switches then it is likely to be rodent damage, a cable trapped by a floor board, nail through a cable etc etc and could be anywhere.

 

[binky]

Cupboard light is not likely to be part of the circuit, unless there's a cable running from that to elsewhere.

If the neutrals are all at a job on the landing, chances are the lives and earths are to. Sounds like you have what is known a ',spider wiring' ie everything is fed from a large square jb on the landing.

 

[Glynk71]

The cupboard light is controlled by the lighting switch on the consumer unit the same as the rest. The rose has two sets of wires, so I assumed it was part of the circuit. Am I right in thinking that if the neutral, live, and switched live are good to the first light, the problem must lie between there and the next light? If they were good wouldn't the next light work. I apologise, electrics aren't my forte.

 

[SPECIAL LOCATION]

Hi all, I'm looking for some advice. This morning there was an audible thud and the lighting breaker tripped. I reset it and it did it again after 10mins or so. I reset it again and now only the first light in the circuit comes on. The lights are daisy chained, I inspected the wiring in the working light rose and all is OK. What is the next step in troubleshooting. We are isolated and with 10 inches of snow it will be after the thaw to get someone out. Thanks in advance Glyn.

Thanks for replying. The whole house is on one circuit. The light in the cupboard under the stairs is working but no others. I assume the next one in the chain would be the living room logistically which I haven't looked at yet. The neutrals i believe run to a jb on the landing.

Is this breaker an MCB or RCD?

If you only have one lighting circuit, this suggests to me that the wiring could be quite old?
As for many years it has been good practice to split lights and sockets across multiple circuits during rewires / Consumer unit replacements so that in the event of a fault you do not lose all lights or all power..

If the wiring is quite old, (I am guessing your breaker that tripped may be an early MCB and not and RCD or RCBO?..) then the various cable joints will also be old...

And old joints and cable terminations where conductors have been squashed into screw terminals that have been subject to the heating & cooling effects of electricity passing through them for years can finally break down during an increased current flow during a lamp failure..

I have known a halogen lamp to blow and also burn out a cable joint part way down the lighting circuit...

However lights are wired as radial circuits, and can have branches anywhere... e.g. at junction boxes, switches, light fittings...
So you cannot assume the order anything is wired in, unless you have tested and proved the circuit with suitable test gear..

The only assumptions you should ever make during any fault investigation is that: "Everything is faulty, until you have proved otherwise"

If you don't have access to any suitable test kit then it is going to be quite difficult to prove you have fixed the problem..?
As sometimes visual inspection of a joint does not immediately show a failed continuity between conductors.

I would have started with some dead continuity and insulation resistance tests, (L-N, L-E, N-E)..
Disconnecting the circuit from the consumer unit, and using my various plug-in lamp adaptors to minimise the amount of accessories I need to open up...

Then depending upon the results I get I would probably find somewhere to split the circuit at a mid-pint to do further tests..

e.g. a good test meter and a set of adaptors similar to these can save hours of faffing around opening up accessories and possibly putting more faults onto the wiring? https://www.test-meter.co.uk/megger-la-kit-lamp-adaptor-testing-kit

 

[Glynk71]

Is this breaker an MCB or RCD?

If you only have one lighting circuit, this suggests to me that the wiring could be quite old?
As for many years it has been good practice to split lights and sockets across multiple circuits during rewires / Consumer unit replacements so that in the event of a fault you do not lose all lights or all power..

If the wiring is quite old, (I am guessing your breaker that tripped may be an early MCB and not and RCD or RCBO?..) then the various cable joints will also be old...

And old joints and cable terminations where conductors have been squashed into screw terminals that have been subject to the heating & cooling effects of electricity passing through them for years can finally break down during an increased current flow during a lamp failure..

I have known a halogen lamp to blow and also burn out a cable joint part way down the lighting circuit...

However lights are wired as radial circuits, and can have branches anywhere... e.g. at junction boxes, switches, light fittings...
So you cannot assume the order anything is wired in, unless you have tested and proved the circuit with suitable test gear..

The only assumptions you should ever make during any fault investigation is that: "Everything is faulty, until you have proved otherwise"

If you don't have access to any suitable test kit then it is going to be quite difficult to prove you have fixed the problem..?
As sometimes visual inspection of a joint does not immediately show a failed continuity between conductors.

I would have started with some dead continuity and insulation resistance tests, (L-N, L-E, N-E)..
Disconnecting the circuit from the consumer unit, and using my various plug-in lamp adaptors to minimise the amount of accessories I need to open up...

Then depending upon the results I get I would probably find somewhere to split the circuit at a mid-pint to do further tests..

e.g. a good test meter and a set of adaptors similar to these can save hours of faffing around opening up accessories and possibly putting more faults onto the wiring? https://www.test-meter.co.uk/megger-la-kit-lamp-adaptor-testing-kit

 

[Glynk71]

The house was rewired and the consumer unit updated relatively recently, within the last 10 yrs. It looks like the landing carpet is coming up tomorrow. I'm very much in the countryside, we do occasionally get mice. I've been up the loft tonight to see if we had any leaks that maybe causing a short. The old wiring is still in place and the new wiring simply mirrors it. I've unravelled christmas lights that make more sense!

 

[SPECIAL LOCATION]

The house was rewired and the consumer unit updated relatively recently, within the last 10 yrs. It looks like the landing carpet is coming up tomorrow. I'm very much in the countryside, we do occasionally get mice. I've been up the loft tonight to see if we had any leaks that maybe causing a short. The old wiring is still in place and the new wiring simply mirrors it. I've unravelled christmas lights that make more sense!

You photos suggest it is older than 10 years...?

As since 2008 wiring regulation 522.6.6 has required RCD protection for cables buried in walls...
And the MCB marked as lights appears to be direct from the main switch with no RCD protection...
And those Volex CU's are quite dated now.

So guessing 2007 or earlier, more likely 17 years +

 

[Glynk71]

It has rcd protection. I don't know if they have upscaled an old unit or if my previous photos didn't provide enough information

 

[SPECIAL LOCATION]

It has rcd protection. I don't know if they have upscaled an old unit or if my previous photos didn't provide enough information

That type of consumer unit normally had no RCD protection for the 6 left hand circuits nearest the main switch..
And the 6 right hand circuits did have RCD protected..
Commonly called a Split-load consumer unit.

If you turn the RCD off do the lights go off?

Can't believe anyone would have fitted one of those in the past 10 years..??
It would have been a dual RCD consumer unit.

e.g. 1x main switch plus 2x RCDs

 

[Glynk71]

I have had a look this morning. It only has one rcd, and that doesn't appear to on the lighting circuit. It looks like i may have been out by a few years on my guesstimation of when it was replaced. We had another dumping of snow overnight so it looks like we are going to be in the dark for a while.

 

[ProDave]

You really need to get an electrician in. He has the knowledge and test equipment to quickly work out what is wrong and trace and find the fault.

Unless you want to be days or weeks without light and without knowing what caused the MCB to trip in the first instance. There could be a dangerous fault lurking there somewhere.