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).

 

[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....

 

[Marcus Vaughan]

And it’s probably a 100 downlighters!

 

[Octopus]

Test first!!!
Said it so many times.

Yup, a Zs at the point you wish to change or spur off at can save a lot of hassle

 

[Octopus]

And it’s probably a 100 downlighters!

Turn off all the light switches & do the R1 + R2 with both live and neutral disconnected from the CU - obviously you need to turn the switch on at the light you are working on..

You've mentioned singles - are the CPC's singles or is the set up reliant on the conduit for the earth continuity?

 

[westward10]

Think he means 6181Y so needs to confirm if they incorporate a cpc.

 

[Marcus Vaughan]

Could turn out to be an expensive switch change!

Exactly my thoughts. As far as they are concerned everything is working. That old chestnut.

 

[Marcus Vaughan]

Think he means 6181Y so needs to confirm if they incorporate a cpc.

Correct. sheathed.

 

[David M]

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

Where can I get one of these "wonder" leads? sorry couldn't help myself

 

[ruston]

@David M. I have one , and tools . I often wonder where they are .
The more I have the less I've got.

 

[Marcus Vaughan]

Where can I get one of these "wonder" leads? sorry couldn't help myself

 

[Marcus Vaughan]

Difinitely a CPC at the CU. Half way through R1+R2 now - and have one switch at only 0.42 ohms. All others are about 60 ohms