The Sinopé low-voltage thermostats ( TH1400ZB , TH1400WF , and TH1400RF) are not dead-band thermostats that start heating when the temperature drops below the set point and stop it when it rises above. Instead, they are proportional thermostats that estimate the power needed to maintain the temperature as close as possible to the set point for the next cycle. It is possible for the thermostats to start heating even if the temperature is above the set point because they calculate that if they don’t start, the temperature will drop too low during the next cycle.