Help ... Shed in Darkness !

[DavidFMarks]

I have a strange lighting fault on an admittedly ancient system in an old stone house where the physical location of wiring is difficult or near impossible to established. Trying to switch on shed light produced no result and I identified an mcb tripped on the consumer board. Trying to reset produced a flash and retrip. I then switched off all circuits that were still on and successfully reset the mcb. I have now switched on all circuits successfully but shed and several indoor lights still don’t work. Since there are no other fuses or mcb’s around I presumably have physical damage somewhere causing an open circuit. I have a junction box in an outside toilet and have established that a live feed emerged from somewhere inside the house into that box . There are two other cables connected to the box, one disappears back into the house and presumably feeds the inside lights which are not working and the other heads for the shed. I have checked the one which presumably should have been live. There is only about 15 v between live and neutral but 230v between live and earth and also between neutral and earth. Can anyone guess what might have happened here ! The only other small, non technical and somewhat unreliable clue is that our dog ( a bit of a wimp ) was in a very nervous state in the room on the other side of the wall to the junction box in which two of the non working lights are situated. I should perhaps add that although I am qualified in electrical engineering .. it was when Faraday was still in short trousers so please excuse my apparent ignorance.. Any helpful suggestions would be appreciated

 

[DPG]

I can't imagine anyone being able to help with this without actually getting to the installation and doing some testing. I like the dog clue by the way Daz

 

[Bobster]

I have a strange lighting fault on an admittedly ancient system in an old stone house where the physical location of wiring is difficult or near impossible to established. Trying to switch on shed light produced no result and I identified an mcb tripped on the consumer board. Trying to reset produced a flash and retrip. I then switched off all circuits that were still on and successfully reset the mcb. I have now switched on all circuits successfully but shed and several indoor lights still don’t work. Since there are no other fuses or mcb’s around I presumably have physical damage somewhere causing an open circuit. I have a junction box in an outside toilet and have established that a live feed emerged from somewhere inside the house into that box . There are two other cables connected to the box, one disappears back into the house and presumably feeds the inside lights which are not working and the other heads for the shed. I have checked the one which presumably should have been live. There is only about 15 v between live and neutral but 230v between live and earth and also between neutral and earth. Can anyone guess what might have happened here ! The only other small, non technical and somewhat unreliable clue is that our dog ( a bit of a wimp ) was in a very nervous state in the room on the other side of the wall to the junction box in which two of the non working lights are situated. I should perhaps add that although I am qualified in electrical engineering .. it was when Faraday was still in short trousers so please excuse my apparent ignorance.. Any helpful suggestions would be appreciated

Should be no problem for you... the laws of physics haven't changed, even from when Faraday was around.

 

[IzzyS]

There is only about 15 v between live and neutral but 230v between live and earth and also between neutral and earth. Can anyone guess what might have happened here !

Yes.

Draw out the circuit, then think about what needs to "break" for you to be able to measure 230v between N and E.

Then, if you haven't already got a calibrated insulation resistance & continuity tester, maybe call in someone who has.

 

[Darkwood]

Same as any fault in your Engineering side just need to locate it and would suggest at the last illuminated fitting or the first one out (or the connecting wire).. its clear the fault was a short circuit and has blown itself clear leaving part of the circuit out... if its a bank of lights that have their own switch then could be in the switch box... too many ifs buts and whys here to give it any better.

 

[Richard Burns]

So there was a short circuit fault line to neutral (possibly earth) that tripped the MCB, then on renergising the MCB without clearing the fault, the fault current blew the fault clear, this should have burnt out at the point of the fault, your voltage measurements indicate a broken neutral connection. If you were measuring just the supply cable to the JB then the broken neutral is before that point. So look for points of use in that cable which may have failed. Just remember that all the cables both line and neutral may well be at 230V to earth so a significant shock hazard.

 

[Marvo]

The only other small, non technical and somewhat unreliable clue is that our dog ( a bit of a wimp ) was in a very nervous state......

Being African I'm a lot more for innovative and unconventional fault finding techniques so maybe sprinkle doggy treats evenly around the room, let the nervous dog loose and watch which biscuits get eaten last. Chances are the fault will be in that vicinity

Seriously though, as already stated sounds like you have an open circuit neutral which is a bit dangerous because the neutrals on one side of the fault then 'float' at 230v so it can catch out those who are unwary. Bearing in mind the neutral that sounds like it 'blew clear' might only be a symptom of another short circuit fault elsewhere upstream so I'd recommend at this stage in the game you get someone in who has experience and the right test equipment.

 

[DPG]

Where's he gone? Has he took the dog for a walk? Daz

 

[ipf]

Where's he gone? Has he took the dog for a walk? Daz

No...he's gone to fix things.....probably frazzled by now due to useful info given.:dead: :nono:

 

[uksparks]

Quite often when you find half the lights don't work, a bulb has blown and caused an already semi loose neutral in a pendant elsewhere on the circuit to come loose and not work and put burn marks just around the terminal slightly.

 

[DavidFMarks]

Quite often when you find half the lights don't work, a bulb has blown and caused an already semi loose neutral in a pendant elsewhere on the circuit to come loose and not work and put burn marks just around the terminal slightly.

Thanks for helpful suggestions folks. I have now reinstated shed lighting by temporarily feeding it from another circuit. Currently still trying to locate the apparent short which has left the neutral on the original feed floating. I do by the way realise that the laws of physics haven't changed since Faraday, Unfortunatley my mental capacity has !