My old Smiths immersion heater timer has packed up so I've bought a Drayton Lifestyle Dual Channel Programmer (LP522) to replace it (with a view to also using it for our CH system in future). the problem is that the old timer simply has one incoming LNE feed cable in and one LNE out to the immersion heater. the LP522 instructions say to have a 3Amp fuse on the live in.....but this doesn't make sense as this will obviously blow as soon as the immersion heater comes on!!!!! help please.....should I have bought a timer instead of a programmer?