In which control action does the thermostat operate in reverse?

The thermostat operates in reverse action when it responds to a rise in temperature by turning off the heating source or activating cooling systems. This type of control is common in environments where maintaining a specific temperature range is crucial, such as in climate control systems.

In reverse action, the control device's output is opposite to the input; for example, if the desired temperature (setpoint) is exceeded, the thermostat will take action to decrease the temperature – this is indicative of reversing its operation compared to a direct approach, where an increase in temperature would lead to an increase in energy input (heating).

This method is particularly useful in systems needing to respond to fluctuations in environmental conditions to maintain comfort or operational efficiency, differentiating it from other control actions which may not reflect the necessity of reversing the action based on the input signal.