I change the old power switch to the oven with the new one. ?

should have supply into top of switch which would connect e-earth i would assume, line will be incoming red and n- will be incoming black, cable out to cooker load will be red and black will be neutral, you ideally need to know which is the incoming cable and which one is out but it is not the end of the world if connected the wrong way as switch will still safely isolate (reason blacks were doubled before as old switch only isolated live supply which is fine, new switch isolates live and neutral which is better)

shaun robinson
April 2010