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).

 

[Pete999]

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).

What was your MFT set on?

 

[westward10]

Check in the board for the presence of a cpc.

 

[Octopus]

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.....

 

[buzzlightyear]

might be sniped of some where .

 

[ipf]

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.....

Yep, link at CU and test at the lighting points first.
Although, are you saying the lives are looped at the switches and neutrals at lights? If so, switch 'em on first

 

[buzzlightyear]

pre 60 years no earths need then ,right pete!

 

[Octopus]

RCD for circuit?

 

[Pete999]

pre 60 years no earths need then ,wright pete!

Right

 

[buzzlightyear]

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.

what class fittings in the bathroom ?

 

[Wilko]

I have found an older (red an black) 1mm twin and earth cable with the earth discontinuous in part of the run. Either a manufacturing defect or the 1mm pulled too hard during installation I reckon, as the cable appeared ok externally.

 

[Jay Sparks]

I have found an older (red an black) 1mm twin and earth cable with the earth discontinuous in part of the run. Either a manufacturing defect or the 1mm pulled too hard during installation I reckon, as the cable appeared ok externally.

And this is exactly why I tell apprentices to check for continuity at EVERY point/accessory. You never know if the cable inside the sheath is continuous or has snapped and pulled a part!!

Jay

 

[Marcus Vaughan]

What was your MFT set on?

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

 

[Marcus Vaughan]

what class fittings in the bathroom ?

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

 

[Marcus Vaughan]

RCD for circuit?

Yep. Split board. RCD protected.