tado

Hi All, I'm really hoping someone will be able to help me with the wiring situation on the backplate of the Potterton as it's a non standard one and as such will need to swap this one out for the Tado backplate. The trouble I'm having is that there's no hep available for what working is needed...

Have an old Danfoss 102 timer unit, I'm swapping it out for the Tado extension kit. Just looking at the wiring... so in 3, what's the black wire for?