ELECTRIC FULLY TRIPPING OUT - please help!

[Invisible-Man]

Invisible, John is right, and as far as I am aware, to comply with Britich Standards, FCU's need to be Double Pole switched anyway, so it is likely that you would isolate the fault by turning off the offending equipment..

Could be wrong on the DP requirement for the FCU's though..anyone know the exact position on this?

Sorry, was not thinking, I was only thinking of people isolating via there MCB, INDUSTRYSPARK mentioned earlier in the post about leaving a possible faulty circuit off to see if the problem stops, could be confusing to a DIY'er, may be to say, isolate the circuit via double pole switch if on a fixed appliance rather than the MCB, this may be understood and more clear saving a mis-diagnosis, just an idea