Rcd tripping on downlights

[cliffed]

Been called into a job,electrician who started to find the fault,left & said he couldn’t find the fault,leaving the client running extension leads everywhere for lights,even in the bathroom.
Basically for what ever reason the rcbo trips ,it can be reset but trips again.
It’s a bungalow with joint boxes for the lights,& loads of fibreglass.Ive split the circuit so now half of the lights are on,but kitchen & diner are off.
The M ohm resistance of the faulty cable is L - E,N - E 0.09,L- N 6.90,
No idea why this cable is at fault,managed to get to all lights,they seem ok,not ideally terminated but looks ok.
Later today will try & get to switches & megger as I go along,the baffling thing,is that this fault is happening ,it a nightmare.

 

[cliffed]

think of the xmas bonuses for doing the job !

Yea,rather be at the pub

 

[cliffed]

If there are only 2 rooms to go .......... disconnect the lights at the switches .......... than add 1 by 1 to see how the IR results change, and if the light buld can be removed you NEED to do this. L&N to cpc isn't a great help in such situations.

Agree,who ever wired/connected this lot,used junction boxes everywhere,lights ,switches,pull a cable to see where it’s going another joint box appears from the fibreglass,trying to get the rest working safely,then the recommendations will follow.

 

[Madocks]

split the circuit, at light no .1 whats the IR results, then add 5 lights and test again

 

[cliffed]

Sounds so simple,the lights on new circuit fine,the faulty one involves quite a few lights,it’s a real mess up there,will let you know how things go,thanks.
Merry Xmas

 

[DPG]

All you can do is keep narrowing down until you find it. Think of the satisfaction when you do though! Make sure you take a picture of the fault and let us know.

Extra sprouts if you find it before Christmas!!

 

[cliffed]

Cheers I will,merry Xmas,I love sprouts

 

[marconi]

Can I put Loft Insulation over Downlights? | Downlights.co.uk - https://www.downlights.co.uk/faq-can-i-put-loft-insulation-over-downlights-.html

You mentioned the roof is insulated with fibreglass. Have the halogen downlights been covered with a 'hat' - see link. You may find the wiring and fitting have overheated. Some extra work to supply and fit these 'hats' if they are not used.

Temporarily, swap over the L and N conductors of lighting circuit at the CU, and then energise the circuit. If RCBO remains set, this might provide some evidence the earth leakage path is predominantly L-E. Not a decisive test though. (Remember L has a pd of 240V wrt E whereas N has a pd of 0V to 1 or 2V).

 

[cliffed]

Thanks,breaking up now for hols,left most of the lights on,will find fault when back to work,client ok about it all,so merry Xmas

 

[Mark Chancellor]

I had exactly this once. I was called out to a house where the RCD kept tripping from the lighting circuit. After a couple of hours testing and searching the home owner decided to mention an old outside light that had "never" worked. The kids had been playing football a while back and had smashed the glass cover. But as the light never worked they just ignored it as it was down the side of an alleyway that they never used. Turned out the supply to the light was still intact and live, a water filled lamp holder was the problem.

 

[Mark Chancellor]

One overlooked problem of the RCD tripping in the consumer unit is when some idiot sticks the neutral wire from a split load RCD board and puts it the other neutral bar.

The continuity test on each light will need to be done to ascertain where the high resistance reading is. I personally hate daisy chaining downlights when they can be All centralised into 1 junction box equal resistance on each light and you need the permanent supply in there to provide a,feed to the common on the switch I still prefer 3 plate wiring I ----ing hate 2 plate going through the switch

 

[Mark Chancellor]

Can I put Loft Insulation over Downlights? | Downlights.co.uk - https://www.downlights.co.uk/faq-can-i-put-loft-insulation-over-downlights-.html

You mentioned the roof is insulated with fibreglass. Have the halogen downlights been covered with a 'hat' - see link. You may find the wiring and fitting have overheated. Some extra work to supply and fit these 'hats' if they are not used.

Temporarily, swap over the L and N conductors of lighting circuit at the CU, and then energise the circuit. If RCBO remains set, this might provide some evidence the earth leakage path is predominantly L-E. Not a decisive test though. (Remember L has a pd of 240V wrt E whereas N has a pd of 0V to 1 or 2V).

That's why I'm glad I use gu10 led's hardly any heat they are brighter they use less wattage but provide the same brightness and they don't melt the downlights fitting overtime. It's amazing how many downlights I have seen have been buried under insulation.

Nice way to cause a loft fire

 

[Pete999]

Should have checked first then, I would have

 

[Mark Chancellor]

Should have checked first then, I would have

Which quote was you referring to?

 

[Pete999]

Which quote was you referring to?

The one with the water in the outside lights

 

[Mark Chancellor]

The one with the water in the outside lights

Oh was that what he on about? Lol I did not read that far back. It is boxing day and a few wines