tumble dryer tripping my RCB?

My Zanussi lindo 1000 heat pump condensing tumble dryer is tripping the circuit breaker whenever it is plugged in, at first it was just the MCB. I have cleaned a wet sock out of the condenser box and drained water out of it, left it open for a few days to dry out. Now it trips the RCB straight away when plugged in. I wondered about an earthing fault? can anyone help, couldnt work out how to get the side panels off :-(
many thanks