main rcd tripping under load

[ollski]

Have a puzzle for you all, my dishwasher works great but as soon as i start up any other appliance like a kettle or oven it trips the main rcd....no problem, get my sparky brother round he fits a new rcd. Now all high load appliances trip the rcd!.
It doesn't matter which ring main they are on either I have disconnected each ring main in turn at the consumer unit and tried the appliances on the one remaining and they still trip....where do I start looking?

 

[breezer]

i have seen similar before, it was nothing to do with rcd, but a "homemade heater" for a pond, wht ever was dissconected it still triped, them by chance looked in the garden and..........

 

[TonyS]

Hi, I'm new to this forum. I'm an electrical engineer with 30 years experience.

One of the most common, but overlooked faults is a neutral to earth short circuit. It's doesn't be come apparent untill a fair amount of load is being passed by the RCD. Unfortunatly it's also one of the hardest faults to find.

You will need a "Metrohm" test set. Each circuit needs to be disconected from the neutral block in the consumer unit and an insulation test made between the individual circuits to earth. Please remember to unplug all appliances from the supply. The 500 volts test voltage will fry most modern electronic toys.

Best of luck.... And be careful....