Scratching my head lighting fault???

[snowhead]

Not the earth, the circuit cpc. There were other people in the house but not in the area of the fault, why do you ask?

So you know exactly where the fault is according to this;(not in the area of the fault)?

 

[SJD]

Hi guys, am new to the forum. My issue is I got called to a friends house as they have an issue with their lights, I arrived and the issue was 1 lighting circuit controlling about 5 lights. I only had some hand tools on me thinking it would just be a hidden rcd or a lamp! I played around a little and the rcd trips with only the line conductor connected to the installation and the neutral and cpc isolated(with or without them connected). I think am having a mind blank as cannot think what would cause this to trip. Tried splitting the lights but is an old cottage and there must be jb's under the floor as am missing feeds at lights/switches?If anyone has come across a similar situation or can shed a little "light" on the situation, it would be gratefully received!!!

With only Line connected, there is some leakage to either earth (more likely) or another circuit, causing the RCD to trip. If there were metal light fittings, you might even have found one to be LIVE with the CPC disconnected!

 

[davesparks]

See the post above.
He knows why.

He's just lucky there's a working rcd in there doing its job!
You can just imagine an ancient bare three strand earth on the watermain taking the brunt of the neutral current and raising all the pipes up to a nice tingly potential!
Bzzzzzzzt

 

[telectrix]

a nice tingly potential




​love it. class.

 

[Englishman]

Yet another member who has signed up because he has no clue about doing his job. If it even is his job. Can these not be stopped?

 

[Paul.M]

These kind of threads are very closely monitored, lets see what the OP comes back with tomorrow.

 

[Englishman]

I just think that they get far too much information gifted. I've said it before, I know that you sometimes get strange situations that you need to ask help with, but a lot of these threads are clearly by people who have little knowledge or equipment, trying to either fix their own jobs, or charging some unfortunate soul to do their work.

 

[GMES]

As Paul already said it is being watched so lets see what the op comes back with also it helps us out if you see a post that concerns you just it the report button to bring it to our attention, we don't expect any of you guys to give out step by step guides.

 

[TJ Anderson]

That is the plan for tomorrow! Just cannot get my head round why it would trip without the neutral or cpc being connected? And also when everything connected will turn lights on for 1-2 seconds and then trip the rcd?

What test gear do you have Ben and what tests are you going to carry out tomorrow?

 

[davesparks]

Yes will do, hopefully will be a lot easier with my mft and analysing my test results, didn't think I would need it lol! - typical

An mft for fault finding? Whats wrong with a good old fashioned megger, much more helpful than a digital display when you're looking for a fault.

 

[Englishman]

Yes will do, hopefully will be a lot easier with my mft and analysing my test results, didn't think I would need it lol! - typical

It should have been the first thing you packed, and I'm not sure why you wouldn't think that you'd need testing equipment to track a fault down.

 

[telectrix]

An mft for fault finding? Whats wrong with a good old fashioned megger, much more helpful than a digital display when you're looking for a fault.

agree. my old megger BM7 stays on the van for fault finding. nobody would think of nicking it and, if they did, it only cost me £2.

 

[davesparks]

agree. my old megger BM7 stays on the van for fault finding. nobody would think of nicking it and, if they did, it only cost me £2.

I've got an analogue Robin yellow brick which was all of £20 on eBay. It's the same as the one my mentor had when I was an apprentice

 

[Sparky2blues]

My money is on a borrowed neutral too

 

[SJD]

My money is on a borrowed neutral too

If the circuit has been working for sometime, i.e. the neutral has not been recently borrowed (and the RCD not recently installed or connected circuits reconfigured) - and just decided to start tripping the RCD - then I'd say a borrowed neutral seems somewhat unlikely. But the original description of the problem was a little vague, so I'd not rule anything out.