High R2 - Lighting Circuit

[Marcus Vaughan]

Hi all,

I was hoping to sneak in a little job late this afternoon - changing a faulty bathroom pull chord for an outside switch plate. No problems with access. Straight forward enough.

House is almost certainly post 60's. CPC's present in lighting circuit.

Live Zs = open circuit.
R2 test with wander lead from MET to as many lighting JB's in the loft I could find = 60 k ohms.

So there is some sort of reading.

Loose connection?

Back tomorrow so any advice on where to start always appreciated.

It looks like the lights are wired in single line + cpc, looped in an out using every which method you can think of, and a neutral looping around each load.

Like I said - where to start.

There are other circuits available in the loft - I could bridge across from 1 JB to another with some 4.0mm if I have to (I suppose).

 

[Octopus]

Yep. Split board. RCD protected.

Does the home owner have the certificate for the installation of the CU? The schedule of test results could make interesting reading

 

[Marcus Vaughan]

I would do a R1 +R2 at other lights on the circuit.

In a house of that age CPC's may be present, but they may not have been connected up.....

I have noticed that before. It seems odd to me when there are CPC’s terminated and connected all over the circuit but not taken back to CU.

 

[Marcus Vaughan]

Does the home owner have the certificate for the installation of the CU? The schedule of test results could make interesting reading

I’ll ask. I was thinking that because I was getting 50k ohms rather that complete open circuit that the install designed to be earthed but something has gone wrong somewhere. I have already sorted out a couple of tapped up connections outside of enclosures - that sort of thing.

 

[Pete999]

Zs for live Zs. Low resistance ohmmeter for R2 wonder lead.

Thanks

 

[Octopus]

the reading you are getting could be a return path via the filament of a bulb and the neutral.

You need to do proper dead tests........

 

[westward10]

Start at the source and see if you can locate a cpc in the CU or you will be chasing shadows.

 

[Marcus Vaughan]

Start at the source and see if you can locate a cpc in the CU or you will be chasing shadows.

Will do. I already got that shadow chasing feeling today. Scratched my head a lot.

 

[Marcus Vaughan]

the reading you are getting could be a return path via the filament of a bulb and the neutral.

I’ll admit to not fully understanding that.

You need to do proper dead tests........

Yep.

 

[buzzlightyear]

At least one fitting is class 1 - at a glance.

and the rest are class2 then, are switches PVC .

 

[Toneyz]

Take lamps out, take L, N,&E of the circuit out of C.U join live and earth at C.U. do R1 +R2 from there back through circuit probably loose/poor connected earth.

 

[Marcus Vaughan]

Thank you.
It might be fun trying to work out which neutral is which though. Wired in singles and a little congested.
Great....

 

[Toneyz]

If you take lamps out and you haven't got any loads between live and neutral you may not need to it just rules out rouge results.

 

[ED17]

Could turn out to be an expensive switch change!

 

[westward10]

Test first!!!
Said it so many times.

 

[Marcus Vaughan]

Test first!!!
Said it so many times.

I might be guilty of not testing first on this occasion....