Does your version of the DT10 control the heating and hot water?
It is possible by leaving the other controller on continuos (24 hours) and then connecting the new stat to the boiler
All controls wired in series - in out, in out, in out like a Christmas tree
That was if any turn off then the circuit breaks and the boiler truns off
So the receiver will take the mains and two cables from Ls and Lr - you could use a single 4 or 5 core cable
Hello Andrew. I am partially familiar with the Greenstar 24i so I already knew I had to connect to Lr and Ls terminals. But just connecting an external controller was not sufficient. but what I needed to do (hence the question) was to disable the existing controller. Well I found the answer here https://community.nest.com/message/27953#27953 all that is need is to disconnect the ribbon cable from the DT10. So it is important not to leave the existing controller in the system (even on 24 hours would not work as it is still controlled by the old wireless stat) Tony