Going to look at my parents' outdoor lighting on Saturday (weather permitting)...

[Mr.Si]

They've got a few different circuits supplied from a separate CU in the shed, all protected behind a single RCD. Controlled by a 6 way switch in the house.

There's one circuit which trips the whole outdoor installation, which is basically 2 flood lights. Initially they turn on, but shortly afterwards the RCD goes.

I'm thinking this is an insulation resistance issue between Phase to Earth or Neutral to Earth but will need to test this to confirm. Though it might just be an issue with water ingress, causing the insulation resistance issue. Does that sound about right?

Since it's an RCD protected circuit, I assume I'll need to remove Ph & N and join together in a choc-bloc or in a croc-clip and test between here and earth, is that right?

I'll have my GN3 and Onsite guide etc, but just wanted to run it by you all first...

I'll appreciate your comments.

 

[Wiredspark]

No harm done. Enjoy your honeymoon Mr.Si.

 

[Mr.Si]

Well, I went back today and replaced the two floods with two new ones (Thorn OTX70s instead of the Azar Nordex ones which were there before).

Following this, all now works fine! So it simply was old units being a problem - just getting old and leaking to earth more than they should.

I also decided to do some more insulation resistance tests for the rest of the cabling and found some dodgy results! N - CPC from the CU to the Switch (all armoured cable under concrete) was 0.86 M Ohms. L-CPC and L-N were both about 27 M Ohms, which is fine, but for the location and for the distance, I'd have expected >500 M Ohms.

I did R1 + R2 aswell and that was about 36 Ohms.

Parents won't let me replace the cabling - it'd be a massive job for them and it would involve digging out all the patio etc.

Despite the results, I'm surprised that all is actually working properly. So I was doubting myself and equipment. Calibration is due though... But my experience is so small at the moment, I'd need someone else to check it out too.

But anyway, they are aware and have been told that it's not as it should be.

Si

 

[pushrod]

Try one of those calibration check cards of ebay or as a very quick check just use a reel of cable if you have any lying around and calc what it should be. Certainly seems as if that cable is dodgy ( or your tester is lol)- might be worth seeing if you could put a replacement in via a different route