any ideas..lighting circuit keeps tripping

[mdgibbs32]

Hi Guys

I hate being beaten but this has got me scratching my head.
Got a lighting circuit thats tripping the mcb (6A 1.5mm t&e), RCD doesnt trip so has to be overload ("has to be" is taken with pinch of salt please!)

All bulbs out - trips
SELV disconencted - trips
all switches unwired - trips
IR test r1+rn >200 ohms r1+r2 >2ohms r2+rn >200 ohms
continuity test - fine

getting a bit annoyed at this one...anyone any bright ideas ?...(get it..Bright..lighting circuit)
It has to be a wiring fault but im at a loss now

 

[telectrix]

find the approx. mid point. dis the ougoing leg. see if it trips. then depending on whether or not, go back towards CU if still tripping, or away from CU if the first bit of the leg is OK. and i don't understand what you have posted re IR tests. they should be L-N, L-E, N-E.and result should be in Mohms , not ohms.

 

[mdgibbs32]

hi telectrix
Your quite correct should have been typed like that... iphone and frustration getting better of me

 

[Former Sponsor TM]

Hi, looking at your insulation resistance test results it appears that you have a problem across R1+R2

 

[mdgibbs32]

sorry that was a typo (on iphone)..all IR tests are greater than 200Mohms

 

[telectrix]

could be a faulty breaker, then. try replacing it before more head scratching, or temporarily shift the circuit to the other lighting circuit.(don't forget to move the neutral if they're on different RCDs though)

 

[mdgibbs32]

thanks telectrix
when you have eliminated the impossible, whatever remains, however improbable, must be the truth ...in desperation rigged up a single 40W light on a totally NEW short radial with one switch, wired to existing MCB – IT TRIPPED !! new MCB and all is fine..
MCB is faulty !!....now I’m annoyed at myself for not trying that 1[SUP]st[/SUP]
Oh well lesson learned

 

[trev]

Check your CU terminations and take a look at the bus bar too.

 

[telectrix]

Check your CU terminations and take a look at the bus bar too.

he's sorted trev. knackered MCB.

 

[mdgibbs32]

thanks guys...most of a day spent on site for an MCB !!
oh well sometimes you win sometime you loose !!
Own fault should have considered it earlier