My circuit breaker to my Rapide 4 shower unit trips out even when the switch controlling the shower is in the off position.
I have changed my micro circuit breaker unit and upgraded to 40amps.
I cannot find any faults in the wiring system

Tony Prodger, December 2008

So it's not the shower tripping the 40A breaker because even when there's no power to it the breaker trips.

You have a short circuit in the wiring to the switch or in the switch itself - best to get a sparky in.

8.5kW shower needs 10mm cable and 40A breaker
9.5kW shower needs 10mm cable and 45A breaker

Peccavi, December 2008