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.

 

[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....

 

[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

 

[DPG]

60 Ohms or 60 kOhms?

 

[buzzlightyear]

now that came to mind !

 

[Marcus Vaughan]

60 Ohms or 60 kOhms?

Sorry. 60 k ohms.

4 faults in CPC terminations at switches and JB’s. Now getting correct R1 + R2.

 

[Marcus Vaughan]

Thanks All. Sure enough CPC was present at consumer unit in with the line. It reached two out of the 8 rooms in the circuit.

Found no less than 4 disconnect CPC’s at junction boxes. I managed to clear the faults to switches at least and a couple of pendants. Never got round to the downlighters - that’s a can if worms. Pretty sure all the CPC faults were caused by whoever riddled the ceiling with the downlighters. Very poor installation.

The customer grumbled about the fault finding though stated ‘I want everything safe for insurance purposes’ but wasn’t prepared to pay for it. I basically worked for an extra 3 hours for free.

Perhaps if the fault was on the line or neutral they would be more understanding?

Thanks all. I can close this ‘Minor Works’ out.

I had a issue with the RCD testing though - all three failed.....new thread.

 

[DPG]

Nice one. Yeah looks a bit shoddy.

 

[Gareth Brookes]

I would send him a quote to get it to the state he wants it and add a bit for the 3 hours you have not charged for

 

[Gareth Brookes]

I would send him a quote to get it to the state he wants it and add a bit for the 3 hours you have not charged for

 

[buzzlightyear]

The customer grumbled about the fault finding though stated ‘I want everything safe for insurance purposes’ but wasn’t prepared to pay for it. I basically worked for an extra 3 hours for free.

I would have walked away from that job. before I start a job I tell the customer
if you want a job doing I tell them no earths on lighting circuits, right down to the bonding the job will not be done .

 

[Marcus Vaughan]

View attachment 40297now that came to mind !

I would have walked away from that job. before I start a job I tell the customer
if you want a job doing I tell them no earths on lighting circuits, right down to the bonding the job will not be done .

I think I must be a soft touch. I take a conscientious approach and always do loads of little extras ‘I’ll just tidy that up so they have no further problems’

I need to toughen up.

I’m a . (Supposed to be a -----!)

Today was a school day in so many ways.

 

[Octopus]

Good man .......... good post, answered questions raised AND gave good feedback on what you found.

Shame lots of posters don't do the same!