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).

 

[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.