External lighting fault

[Bradley6969]

Fault on external lighting roughly 12 lights around a building, RCBO tripping, my tester only goes to 200 Megger Ohms
L-N is 0 Megger
N-E is greater than 200 Megger
L-E is greater than 200 Megger
LN-E is 150 Megger

Now tested insulation from board and roughly found the middle light with 1 cable so must be joint boxes somewhere I can’t find, went to a light further and found a joint box and tested each leg and was getting near to no Megger Ohms on each side, any further ideas?

 

[telectrix]

short, water, cable fault. test everyting and then find the fault.

 

[Bradley6969]

Yes looks like the plan of action,
now I’m getting L-N 0 Megger could this be cause of lamps/ballasts still connected giving false readings?
Looks like I’ll be testing and bypassing each fitting

 

[Jim_e_Jib]

Fault on external lighting roughly 12 lights around a building, RCBO tripping, my tester only goes to 200 Megger Ohms
L-N is 0 Megger
N-E is greater than 200 Megger
L-E is greater than 200 Megger
LN-E is 150 Megger

Now tested insulation from board and roughly found the middle light with 1 cable so must be joint boxes somewhere I can’t find, went to a light further and found a joint box and tested each leg and was getting near to no Megger Ohms on each side, any further ideas?

Are all the lamps/bulbs disconnected when you are testing? 0 mega ohms could be a dead short or it could be some value less than 1 mega ohm.

 

[telectrix]

was tryin gto help but the beer taken over, snd it s tinme for my hbeddibyes accordonf to nursie,

 

[Bradley6969]

Are all the lamps/bulbs disconnected when you are testing? 0 mega ohms could be a dead short or it could be some value less than 1 mega ohm.

There all still connected, there’s something like 12 lights and was getting 0 Megger at the board L-N and when tested at light in the middle of circuit something like 0.06 Megger

 

[westward10]

If the luminaires are still connected you cannot obtain a line/neutral reading, forget that. If you are 100% certain the neutral is isolated at the dist board and you are getting zero meg to earth then you need to break down the circuit to find the fault.

 

[Bradley6969]

If the luminaires are still connected you cannot obtain a line/neutral reading, forget that. If you are 100% certain the neutral is isolated at the dist board and you are getting zero meg to earth then you need to break down the circuit to find the fault.

Thanks, and was only 0 Megger L-N, all others were off the scale so all good must of been cause I left al lamps in, need to open all fittings and go from there, thanks again

 

[davesparks]

Thanks, and was only 0 Megger L-N, all others were off the scale so all good must of been cause I left al lamps in, need to open all fittings and go from there, thanks again

It might be an idea to learn how to test correctly before you damage installed equipment or your tester with your haphazard attempts at testing.

 

[Bradley6969]

It might be an idea to learn how to test correctly before you damage installed equipment or your tester with your haphazard attempts at testing.

Only been testing on 250v sorry mr know it all

 

[davesparks]

Only been testing on 250v sorry mr know it all

You were carrying out the test incorrectly regardless of what voltage you tested at,my point still stands. Testing at 250V instead of 500V just further proves that you don't understand the test you are carrying out.

I don't know it all or expect anyone else to know it all, but I do expect an electrician to know the basics of the science of electricity and understand insulation resistance testing.

 

[Charlie_]

Only been testing on 250v sorry mr know it all

I wouldn’t call him Mr know it all...
A suitable title would be Mr Electrician

You need to carry out tests on the wiring at 500v

 

[telectrix]

i first do a continuity test L-N to see if there are any loads connected. sometimes there may be a neon switch will read something like 23K ohms. ( or is it 2.3 K, i forget, bloody dementia)

 

[Pete999]

Only been testing on 250v sorry mr know it all

Only been testing on 250v sorry mr know it all

Being a bit harsh in your reply there Bradley, I sent you a PM which you haven't responded to, trying to help you with your terminology, a thanks would be nice, but not holding my breath, for a reply anytime soon.

 

[Bradley6969]

I apologise.