I have just changed an old Wylex consumer unit for a new Excel 6 way with an already installed RCD in it. When i press the Test button the RCD wont trip out. I have disconnected all circuits and it still doesnt work. I have reconnected just one circuit (water cylinder immersion) turned the immersion on and it still doesent work. I disconnected the Immersion circuit and connected just the shower circuit, turned the shower on and it still doesnt trip out. I have also swapped out the RCD for another (seperate consumer unit for economy 7 storage heating) and repeated the above steps and got the same results. Should the test button trip out the RCD with no circuits connected? I would assume that a 9.5Kw Shower would be a sufficient load if current needed to run through the RCD for it to trip? Any ideas would be greatly appreciaated. Im not an electrician but am fairly competant. I dont have any sophisticated test equipment other than a multimeter. Many thanks.