Upstairs Lighting Circuit Nightmare!!

[Hiddo]

Evening

I attended a job today where the upstairs lighting circuit is dead. IR is >200MOHM across L-N L-E & N-E getting a high continuity reading 1.46OHM but here is the dilemma.

I have visually inspected in the loft and corrected a few faults/mistakes and still cant get power into the circuit. I ran a fly lead from the CU and when I put the power back on it blew the MCB (No RCD).

I have checked all the terminations and even replaced some of the legs on the circuit as they were broken into and jointed.

Do I just start again or has anyone come across this before?

Cheers

 

[Adam W]

What kind of 'faults/mistakes' did you 'correct' in the loft?
I think I'd try to find the first light on the circuit, get that working, and take it from there.
I wouldn't try juicing it up until I'd found the fault and rectified it - R1+R2 and IR maybe, but not 'bang'.

 

[Guest123]

If your I/R is >200Mohms between all conductors, that is fine. Where did you get your 'high continuity' reading of 1.46ohms from???

 

[Hiddo]

The faults/mistakes were a spur of the circuit to a socket (Removed) and a connector block used to feed an extra light so installed a JB. I cant find the first light, that is the problem. I have told the customer I might have to re-wire the circuit but the feed from the CU to the first light is not where I would expect it to be I.E straight up to loft.

Ive never seen anything like this before and Im sure the customer has been "having a go" but wont own up.

 

[Hiddo]

Lenny got that from what i thought was the first light and then from two other lights. Give or take they are all about the same!!

 

[Adam W]

The faults/mistakes were a spur of the circuit to a socket (Removed) and a connector block used to feed an extra light so installed a JB. I cant find the first light, that is the problem. I have told the customer I might have to re-wire the circuit but the feed from the CU to the first light is not where I would expect it to be I.E straight up to loft.

Ive never seen anything like this before and Im sure the customer has been "having a go" but wont own up.

That was my initial impression as well - it sounds like he might have just got a couple of connections the wrong way around, or otherwise drilled or nailed through something.
I reckon you might have to do a bit of belling out to suss out what's going on, and you'll probably find the fault in the process.

 

[Hiddo]

My plan was to split all the lights from each other and then get one working then the next etc.

Its gonna be one of them jobs I know it!!

Thanks for your input.

 

[1shortcircuit]

I reckon you might have to do a bit of belling out to suss out what's going on, and you'll probably find the fault in the process.

If in doubt, bell it out :thumbsup

One thing that has always stuck in my mind is when I was told NEVER try to understand or presume how the electrician before did it... You need to prove where that first leg is so that you can proceed onto the next one.

I would disconnect the terminations in the consumer unit and join together Live and CPC, disconnect all the wiring at every light upstairs and bell it all out, doing the same with the switch wires too. You never know, for some daft reason the first point may be a ruddy outside light or an odd downstairs light for some bizarre reason???

You will suss it out this way

Be sure to really put the pressure on the home owner to see if he'll own up to doing any work. If he knows you'll be charging him by the hour to do this he may change his tune and start giving you an idea of where the fault may be because his "Friend" decided to do an odd job for him just the other day but it kinda slipped his mind

Good Luck:thumbsup

 

[Paul.M]

Good advice from shortcircuit, I had a problem a couple of weeks ago. Full kitchen rewire and new c/u, didn't touch the rest of the house apart from testing before the c/u change. On the last day doing the 2nd fix just for the cooker, hob and some plinth lights the home owner says the upstairs lights don't work since I did my work? They flickered for a couple of days then all off! The first question I ask is "what was the last thing done to the lights?" Husband put in a new bathroom light. All it was were a snapped off neutral in the fitting but my question and their honesty saved me a lot of time and them a bit of money. Always best to be honest to the sparky just wish that everyone was.

 

[Octopus]

You took out the "spur" to a socket - are you sure this wasn't the source of power for the circuit?

 

[Amp David]

Quality thinking there Murdoch, like it!

 

[1shortcircuit]

Quality thinking there Murdoch, like it!

I agree but surely the mention of "Spur" indicates that there is only one cable terminated in the accessory?

Wouldn't it be great if this was the factor that had been overlooked and solves the problem :thumbsup

Definitely worth going back to double check as more often than not, when we start to become muddled we often overlook the most blatantly obvious things

 

[Octopus]

In my mind I still can't reconcile the nice high IR readings and the MCB going bang.

I'd also be looking for recently changed light fittings with the switch wire connected incorrectly i.e. connected between live and neutral with no lamp in series!

 

[Hiddo]

The Socket was definitely not the feed to the circuit. I belled everything but no feed could be found. I undid everything, checked it, re terminated. I ran a new feed in and hey presto - normal service resumed. >299MOHM IR reading. 0.62OHM R1+R2. Happy Me and Happy Customer.

 

[Paul.M]

The Socket was definitely not the feed to the circuit. I belled everything but no feed could be found. I undid everything, checked it, re terminated. I ran a new feed in and hey presto - normal service resumed. >299MOHM IR reading. 0.62OHM R1+R2. Happy Me and Happy Customer.

So where has the original feed gone then?