What is the purpose of a reverse acting aquastat in a hydronic system?

A reverse acting aquastat is used in hydronic heating systems primarily to control the operation of circulation pumps based on water temperature. Its purpose is to stop the circulator when the water temperature falls below a specified setpoint. By doing this, it ensures that the system operates efficiently and prevents the circulator from running when there is insufficient heat in the water, which can save energy and protect the system components.

This functionality is crucial because when the water temperature is below the setpoint, it typically indicates that the water is not hot enough to effectively provide heating to the space. Stopping the circulator in this scenario helps to avoid unnecessary operation that could waste energy and lead to increased wear and tear on system components.

The other options present different operational scenarios that do not align with the primary function of a reverse acting aquastat. For instance, activating the burner at high temperatures or maintaining a constant boiler temperature are not tasks assigned to this type of aquastat, as its focus is specifically on temperature regulation related to the circulator's operation.