Boiler does start as per times set (Twice: once in morning and once in evening, two hours each time). Water tank gives hot water. But all radiators in the house are cold.
This began after holes were drilled right above Thermostat that dropped lots of fine dust on Thermostat and surely quite some got in.
Previously when turned Thermostat was giving 'kt' sound when room temperature was crossed. No such sound any more.
Regards, BarJor