Not sure if this is the right place to ask but......

[lobsterbob]

I have been tasked to sort out a tripping problem. It's on outside light set in concrete blocks it's an old system and the "brick" lights aren't water tight. A couple of months ago they tripped out. And last night I had a look to see if it was a simple problem I flicked the switch to see if the problem had rectified itself - thinking water may have caused the initial problem it tripped out straight away. Re-energized the lights stayed on for approx 3 mins then tripped again. I dismantled the guts of the lights one by one and discovered a chard lamp/lamp holder disconnected this. Re energized pop straight away - powered up again almost straight away and they stayed on from approx 3 mins then pop. It's protected by an MCB - do they need to be up-graded to an RCD because they're outside? Why aren't they tripping out straight away on the second re-energizing? I thought if there was a problem like a short circuit they'd go in x amount of time even if you re-energized 100 times?
I'm not a fully qualified spark but could you please give me a few pointers on how to solve this problem please and any explainationas to why would be grateful.

 

[malcolmsanford]

Unfortunately your going to have to go down the road of testing a circuit which is an electricians domain. I would personally take down the light just leaving the cables becasue if the fitting is burnt it needs removing. I would then find where it is fed from a disconnect from there and do a 500V Insulation Resistance test on the cable. This will establish if the cable is good or not.

If I were you then again take the light down and put the cables into a connection strip, and then energise the circuit and see what happpens. A cautionary note the more a MCB trips the more likely it will be damaged and this might be your problem now.

 

[Guest123]

If it's an MCB operating then it's either overloading or there is a L-E or L-N short circuit.

It could be that the short circuit is arcing together and only making a dead short at random times.

First thing would be to inspect all the fittings for obvious signs of arcing, if they all look fine try clamping the circuit feeding the lights as other light may have been added to this circuit over time. After this if there is still a problem then you will need IR test the fixed wiring to locate the fault.