This is quite basic stuff you ask - it suggests that an electrician may be safer for you...
Shower switches will be two-pole i.e. both live (red) and neutral (black) will be switched - as in connected / not connected. One pair of red/black will be the supply into the switch and the other pair of red/black wires will run to the shower.
The Green/Yellow are Earth conductors and are never switched - there should be a separate terminal for them so that they may be permanently joined together.
Isolate the supply before starting &...
Take care...
Peccavi, October 2010
