Lighting circuit RCD trips after 5-15 minutes, all lights OFF

[kingshott]

why would a lighting circuit keep tripping after 5-15 minutes, hard to isolate parts of the circuit, old house. The first trip was for no apparent reason, since then circuit will hold up for 5-15 minutes. Upstair and downstairs on one circuit. Have checked all accessible switches/connections, nothing loose and no soot, in the roof area some rodent nibbles on outer insulation (plus 3 wasps nests, so no going back there for a day or two). Does the time delay indicate something (like something heating up and failing, but what, all lights OFF still fails)? Any help much appreciated.

 

[ukpablo]

what did the ir tests show?

 

[Darkwood]

Comfirm it rcd and not mcb or rcbo so we dont head down the wrong road, this can one of the hardest faults to find and could be ingress of moisture in say an outside fitting or a trapped wire under a board that can cause the trip when walked over, the nibbled wires situe is a high suspect though, would suggest IR test which may reveal where problem exists.

 

[kingshott]

I am not an electrician, so do not have an IR tester, is there anyway I can test the insulation myself?

 

[ukpablo]

no
need a tester bud, visual not going to test it fully im afraid!

 

[kingshott]

thanks, appreciate the tip, at least I know an IR test is the way to go, I will call an Electrician in! Cheers.....