thermostat controller?

Some systems have a frost-stat - they fire it up if the temperature gets close to zero - to prevent the pipes from bursting due to ice.

The user instructions for your thermostat can be found here...

http://jcbathrooms-heating.com/Siemens%20room%20stat%20instructions.pdf

The Comfort Setting is set by the user
The Setpoint is set by the user
Frost protection kicks in at 5 deg C

The word setback does not appear.

I have looked at the instructions and find it all too complicated for me but...

I think Setpoint is their term for the point in time that it's set to turn on

I think Comfort is the term they use for the temperature setting.

This word puzzle below may have something to do with it....
But who can say?

The switch on and off times are interrelated. When trying to set a switching time to a time after the subsequent switching time, the latter time will automatically be pushed forward (or backward).

So - things should be much clearer now...

Your user instructions are not very helpful - we have a small thermostat dial on the wall in the hall - we set it to 15 when we get up and we set it to 10 when we go to bed - the boiler is on all the time - we buy our energy from Ovo in Bristol - things for us are much more simple than they seem to be for you. TRVs on all radiators allow us to make some rooms cooler.

Good luck...

Happy new year...
December 2014