Wiring for my current battery powered Thermostat

[AmatureGuy]

Hi All

I just need to know as to which wires represent which and if there is a power wire in the attached picture as my current Thermostat is battery powered and I am looking to see if I can replace if with the smart Thermostat.  Current thermostat is CM67 Honeywell.

In the picture attached I don't have the blue and green & yellow wire connected anywhere.

 

[ProDave]

IF (and that is a big if) it has been wired according to the diagram the yellow wire with red sleeve in terminal A is a L feed and the blue MIGHT be neutral or it might not be connected anywhere.  The only way to find out would be to test it.  the Red in terminal B would be the switched output.

Even then, the L feed might only be on when the boiler programmer is calling for heat, it depends on how it is wired, and that might not be what your smart thermostat wants either.