Gate Lights - this is weird!

[nickonline]

Hope someone can help! My gate lights work fine for about 6 hours or so and then unexpectedly trip my mcb for no apparent reason. The lights are switched from inside the house. I've bought and installed brand new lights and changed the switch but no improvement, although I got a record 11 hours out of them recently!
It's not an overload issue as the lights typically fail during the night. Bulbs are simple everyday 60w. The gate lights are fed via the switch to an external junction box and armoured cable from there to the lights. Have checked all connections and no signs of any damage to the cable.
Can anyone suggest some test I could do to try and get to the bottom of this, perhaps at least to isloate the issue to pre or post switch.
Many thanks
Nick

 

[Adam_151]

Can anyone suggest some test I could do to try and get to the bottom of this, perhaps at least to isloate the issue to pre or post switch.

insulation resistance of the cable, unfortunatly its unlikely that you'll have the equipment to do this

 

[Qedelec]

There is the faintest possibility that you have a fault MCB.
Assuming you have two lighting cicuits, swap the cables and see if the other one trips. Other than that, as Adam has said you will have to do insulation tests on the circuit.

 

[nickonline]

Thanks for the replies - much appreciated. Have changed to the other MCB (worth a go!) and failing that will call in the pros.