I changed a couple of sockets at a property I am working on and put my plug tester in to check and it tripped the rcd. Tried a couple of times then took sockets off to check them - all ok. Tried to do loop test with my kew 63 tester - tripped again. Tried a few other sockets in property and all tripped out. Plugged Dyson into same sockets and it worked fine. Consumer unit is 30 year old split load unit with 100mA rcd main switch and 30mA secondary rcd. Can test ok on 100mA rcd side but trips on testing secondary side. Connections ok inside. Has anyone come across this type of fault before. I seem to recall it happening before on another consumer unit which I changed. I believe it was an MK unit as is the one I am writing about now.