"clicking" Thermostat?
Both the Smartstat, and Easystat thermostats contain within them, a mechanical relay. When power is called for, the relay will engage and an audable click can be heard. Some thermostats will be louder than others. In addition, certain types of construction may cause the click to be louder. For example, a tiled wall may carry sound better and make the click sound resonate more within the room. The audable click is normal.