I have an old analogue thermostat that I want to replace with a digital programmable one. The old analogue one has three wires into it whereas the new one I've purchased only talks about connecting two wires, can this be done? I've added a few images which hopefully will help. The first is the connections on the old thermostat, the second is the wiring diagram from the cover of the old thermostat and the third is the wiring diagram from the new thermostat. It says to connect the boiler to the 'com' (common) and 'no' (normal open) terminals. Thanks in advance.