Why are the lights not working!!!!!

[HappyHippyDad]

Just popped in to a friends house on the off chance that I could quickly remedy some none working lights before heading off to work. Unfortunately it was all a bit odd!

Over the past 2 years the ground floor lights have stopped working perhaps 3 times. They stop for either days or weeks then start working again.

None of the ground floor lights are working at present, so I started at the origin, I.e the CU. There was 240v on the line conductor (to earth) leaving the RCBO, but also 240V on the neutral conductor (to earth) leaving the CU. I realise it's unlikely to be a faulty RCBO, but I have come across a faulty protek MCB before, along with a faulty chint RCD. Only 2 faulty breakers in the past 10 years, as it's nearly always something else that's at fault. I'm only mentioning this to explain why I dived in with 'faulty breaker', plus I was hoping for a quick fix.

However, in the meantime they all started working and there was no longer 240V on the neutral terminal of the outgoing RCBO. All I had done is take the lid off of the CU and switched a few light switches on and off.

As stated earlier i considered a faulty RCBO, so I put the ground lights on a different RCBO. They then all stopped working again, and there was now 240V on the outgoing neutral terminal of this RCBO (along with 240V on the line). I put them back in the original RCBO and they all worked again.

Also, the test button on the RCBO's didn't work when there was 240V on both the line and neutral, when this cleared the test button worked.

Also, the test button didn't seem to work on the spare RCBO's that had power going to them, but no outgoing conductors in place. However, they did work on one of the RCBO's that was spare (without conductors). I checked the busbar and it was correctly in place for all RCBO's.

Ground lights are now switched off and I'll return, but I'm embarrassed to say I really can't think of what to do. Usually, a fault shows up, I break the circuit down, find it and fix it, but this is different to usually. Any suggestions?

 

[timhoward]

240v on the N terminal of the RCBO makes my mind jump to faulty RCBO, poor termination of RCBO N fly lead, or wider issue with N of the installation.

 

[Marvo]

As per Tim, check the circuit neutral isn't accidentally behind the cage clamp termination of the RCBO instead of inside it. Could be an upstream neutral fault but that would probably affect other ccts. Faulty RCBO is also possible.

 

[timhoward]

(It's probable that some of the RCBO's test button don't work because the N fly leads aren't connected and are taped up underneath. Could also be why your attempted cct move failed)

 

[littlespark]

11 rcbo’s and only 8 fly leads connected.

If the remaining fly leads are in the block below… look there first. Must be a loose connection.

Watch your fingers on the unguarded live busbar there.

 

[westward10]

11 rcbo’s and only 8 fly leads connected.

If the remaining fly leads are in the block below… look there first. Must be a loose connection.

Watch your fingers on the unguarded live busbar there.

I suspect they could be for the ones not in use.

 

[UNG]

Looking at the RCBO flylead terminations into the neutral bar I suspect some of them are clamped on the cable insulation rather than the crimped ferrules

 

[HappyHippyDad]

(It's probable that some of the RCBO's test button don't work because the N fly leads aren't connected and are taped up underneath. Could also be why your attempted cct move failed)

Blimey, that's ridiculously obvious,
I hate trying to do things quickly, without giving it the time and thought that is needed.
Thankyou everyone for your thoughts (and for not telling me I'm a plonker).

 

[Rockingit]

My brian's a bit fried at the moment to reverse engineer your post in my head but could it be a case of reverse polarity and a switch been put through the N side? That would give you a backfeed onto the N explaining the N-CPC voltage and ensure that nothing then worked as you've got no PD. Hence, only affected by a certain combination of switching. Maybe.

 

[timhoward]

By the way, those fly leads are a truly shocking colour. Reminds me of school dinners and some cheap powdered desert they used to slop out, was it called Instant Whip?!

 

[Dustydazzler]

Is it just me, but don't a lot of the cables, especially the cpc sleev look very sun faded

 

[littlespark]

By the way, those fly leads are a truly shocking colour. Reminds me of school dinners and some cheap powdered desert they used to slop out, was it called Instant Whip?!

Instant whip, angel delight…. Under another name….

And for a final nostalgia hit…. Cremola Foam.



Back to the problem… I never even noticed some rcbo’s didn’t have outgoing cables.

For intermittent symptoms… looking for an intermittent fault. I’d look at how those tails are terminated into the neutral bar… looked pushed too far in

 

[UNG]

Thankyou everyone for your thoughts (and for not telling me I'm a plonker).

We could if it would make you feel any better just be careful of anyone calling you Rodney

 

[HappyHippyDad]

My brian's a bit fried at the moment to reverse engineer your post in my head but could it be a case of reverse polarity and a switch been put through the N side? That would give you a backfeed onto the N explaining the N-CPC voltage and ensure that nothing then worked as you've got no PD. Hence, only affected by a certain combination of switching. Maybe.

My instinct was to switch off the lights I had switched on, thinking the same as above, lost track of what I had switched on and off though. Again, rushing!
I'm liking the N fly lead being casually terminated in the N bar (intermittently making contact).

 

[James]

Blimey, that's ridiculously obvious,
I hate trying to do things quickly, without giving it the time and thought that is needed.
Thankyou everyone for your thoughts (and for not telling me I'm a plonker).

You are a plonker,
99% of the time if you have a good voltage between N and earth, the N cable is not connected reliably to the incoming N terminal.
The only other option is that the earth is not connected to earth and infact is sitting at 230v relative to N and true earth.

However, sitting comfortably at my desk with a beer, it is easy to call you a plonker or anything else that springs to mind.

Out on site with the customer breathing down your neck and a whole host of measurements that don’t seem to make sense, things are not so easy.
Get fixated on a wrong assumption or trying to chase down a fault using “it’s probably this” approach can lead to anyone becoming confused.

I am a smoker and wouldn’t recommend it to anyone but it does have the advantage of giving me a reason to escape, stand outside and consider what I am dealing with and come up with a plan of attack.

Whatever fault it is that is confusing, nearly always has a logical cause, sometimes it is just a case of saying to the customer that you need to pop out to the van and “find your spare flux capacitor or calibrated test meter”
Use the time to stare at the clouds and summon your logical brain into action.

Anyone who has never misdiagnosed a fault is either a lucky person that has never had a difficult fault to figure out or a liar.

Don’t beat yourself up, we have all had days where we are the plonker, let’s face it if I had a pound for every mistake I have made, maybe I wouldn’t quite be a millionaire Rodney but I would certainly have enough to go to the Bahamas for a week.