RCD Tripping in outbuilding on Lights, please help

[Pensdown]

The insulation tests are fine, the ring main doesnt trip, the lights are on a seperate breaker, i havent checked the polarity of all lights will do when i return but what i dont understand is that there are two circuits in one 6A breaker which isnt a problem as there are only 8 lights but even whe i try the circuits seperate, and try to put a lamp in they still trip. any advice would really help

Have you tried splitting the 2 circuits to narrow the fault down?

 

[Har_vey]

How are the cables fed from unit to the lights?

How many switches in circuit?

Check the switch pins.

 

[Barnie]

ive split the circuits and its happening on both, i havent checked the switch oins but i will do im going back on sunday so im arming myself with info

 

[JohnD]

If you can, take a digital photo of the inside of the CU. I'd be really interested to see it.

 

[Barnie]

from what i have checked it all seems to be wired fine, rcd and MCB for socket and MCB for lights, it s only happening on the light circuit, ive IR tested it and no problem

 

[Spark123]

Have you checked no fittings have been accidentally wired wired L-E as opposed to L-N?

 

[Barnie]

i will also check that too, its excellent advice guys thanks, anything else you can think of then please let me know. i take it ill have to go through the two circuits and check each light and switch seperately to find the culprit if its not the ccu. and anything else thats coming off the circuit like a small fan heater etc. while im on the subject of fault finding, is there a fault find, diagnosis and rectify form and certificate or do you just use a PIR? just wondered as would i have to go through all the supply characteristics etc etc paperwork just for a fault find and put right situation?

 

[JohnD]

In a shed or garage you won't have many lights. But if you had a biggish circuit, you could disconnect about half way along, and see if the fault still occurred. If so, it's in the half nearest the supply. If not, it's in the further half. Then halve it again, and so on until you've narrowed it down to a single thing.

Of course, there may be more than one fault, but once you've fixed one "half" you can move on to the next.

This will work for any radial (rings are different )

 

[Barnie]

thankyou John thats great advice!!!!