Lighting IR low help....!

[Just]

I've been scratching my head today on a survey and before I advise remedial work just want to be sure I'm not missing something obvious.. Firstly 3 strand 1.5, singles into the board with no CPC at the board, but all light fittings have a cpc and worst fitting R1 R2 was 0.6ohms so quite high. Seeing this I did IR test at the board got an odd result so checked any thing that may affect this. Isolated boiler at switch and two fans at fan iso, still rubbish, removed lamps still rubbish. Disconnected both lighting circuits and IR'd R1, MET and getting 0.03M R1,Rn .05M upstairs R1,Rn is dead short 27ohms. Is there anything else that would give this reading?Lamps I've missed, security lighting..etc The RCD main incomer isn't tripping??! If I sort it.. how do I write up missing CPC at board and what CSA do I fill in as I have seen everything from 0 to 2.5mm (none at DB, 1mm most fittings but found a 2.5 of a shower cable in another..) shall I just put a range! LOL

 

[DurhamSparky]

suggest further investigation , from what you saying i would rewire the lights fully to save face!

 

[telectrix]

what are the singles run in? if in steel conduit ot trunking, that might be the cpc.

 

[Just]

No conduit or trunking. So if cpc's are being robbed I can't check the separation box or can I note this as a noncompliance in the existing installation box? hmmm

 

[IQ Electrical]

No conduit or trunking. So if cpc's are being robbed I can't check the separation box or can I note this as a noncompliance in the existing installation box? hmmm

The 'separation box' is something rather different to what you are describing!

 

[Just]

Sorry meant IR between individual circuits not SELV PELV etc. In this case, can existing CPC's be combined from existing other circuits, therefore a note in existing installation box? Any ideas on p poor IR vals?

 

[IQ Electrical]

Cpc's can be common and interconnected, 543.1.2 refers.

Why would you need to IR test 'between circuits' on cpc's anyway? With the usual parallel paths, I'd be amazed if you ever got a 'clear' reading on that one

 

[Electricalserv]

Securirty lighting pir's may be a problem have you, tested live and neutral tro earth? Or is cpc missing? Not sure I fully understand your situation

 

[Just]

Hi, every fitting has a CPC but as I said in #1 everything from 1 - 2.5mm... worst R1 R2 was .64ohms but there are no lighting CPC's at the DB. When I IR LN/MET I get .06M. and the same on the upstairs radial. GOing back today to check for powered antennas, smokes, PIR's fans etc etc but fear the worst and wonder where to start. Splitting upstairs/downstairs at the two way? Or would you go to every fitting first for obvious signs? Luckily it's a pre-DB change survey but want the job and know she won't want a rewire as it is an HMO so we have tenant disruption issues and 'it ain't broke yet'. Reason for change is 20 year old Proteus board plastic breaking down so earth and neutral plastic bars broken, holes everywhere, but has main RCD which tests okay and doesn't trip with iffy light circuit. Really this is a floors up job isn't it?

 

[Just]

Okay some improvement today! 'Twas bugging me so isolated everything and found the cause of my main problems... 12v lamp up inside the center of an extractor. Doh! I still have problems though but things are better..
up
L/N 254 M ohms
N/E 506 M Ohms
L/E 1.18 M...

Down
L/E 248M Ohms
L/N 1.18 M Ohms
N/E 286 M Ohms.

I noticed a bell transformer on the way out didn't clock as there is a plug in bell so will check that tomorrow.
Took all the switch plates and ceiling roses down and nothing obvious,
Any advice greatly appreciated. Cheers.

 

[Just]

Cpc's can be common and interconnected, 543.1.2 refers.

Why would you need to IR test 'between circuits' on cpc's anyway?

Hi IQ no didn't say that, I was talking about interconnections between circuits,(not well explained sorry) I know cpc's can be combined but how would I write up as there is no CPC to the MET? but each fitting has a cpc obviously from another circuit. I presume a note in existing installation but what CSA for CPC as they are all different!

 

[IQ Electrical]

Hi IQ no didn't say that, I was talking about interconnections between circuits,(not well explained sorry) I know cpc's can be combined but how would I write up as there is no CPC to the MET? but each fitting has a cpc obviously from another circuit. I presume a note in existing installation but what CSA for CPC as they are all different!

You could include a note but assuming all fittings have an acceptable R2 reading then I would just include a LIM in the 'cpc size' box on your schedule of circuit details.

 

[Just]

Thanks IQ, are you saying I should do an R2 to every rose and switch with a wander lead back to the MET as there is no CPC for lighting in DB?

 

[ratpig]

Are there any shaver sockets?

 

[IQ Electrical]

Thanks IQ, are you saying I should do an R2 to every rose and switch with a wander lead back to the MET as there is no CPC for lighting in DB?

A Zs at the fittings is probably better, even though you can't trace the route of the cpc, you can still prove compliance for ADS.