Hoover HDC6 Condenser Dryer tripping RCD - Drawings / Manuals?

My dryer is intermittantly (but often) tripping the main RCD on the consumer unit. Does anyone have any idea what it may be / what I should check first? Can anyone tell me where I could get hold of a service manual or electrical drawings please?

I've visualy inspected what wiring I can see with the lid off and the elements for damage and they look ok. I could do with some advice before I dive in and try and get to the motor.

Thanks.