Well it did. Trip off randomly I mean. A split load consumer unit and the offending R.C.D. tripped off three separate circuits. 1. Some bungalow lights. 2. Heating system and oil boiler plus immersion heater fed from ring final. . 3. Single radial circuit to one single socket supplying the washing machine.
Number 2 showed strange insulation tester readings. I suspected the tester. I then used a different insulation resistance tester and got the same strange fluctuating readings. The reading went from high to low resistance. I suspected water in an outside light. I tested stuff in the garage which was fed from the ring and found the fault. It was not water or electronic breakdown of an outside P.I.R. light.
The fault which has been there for 30 years was found inside an old fluorescent fitting.
You'll never guess just what happened. A prize to the winner.
old fluorescent light circuit - Bing
Z.
