What type of controller increases line pressure when room temperature increases?

A direct acting controller is designed to respond to changes in a controlled variable, such as room temperature, by increasing line pressure in response to an increase in temperature. This is typically achieved through a sensing element that detects the rise in temperature and activates a control mechanism to adjust the pressure accordingly.

In applications where maintaining a consistent environmental condition is crucial—like in heating, ventilation, and air conditioning systems (HVAC)—this type of controller plays a critical role. As the temperature increases beyond a set point, the direct acting controller compensates by boosting the pressure to enhance the flow of heating or cooling mediums, ensuring that the desired temperature is maintained.

The other options, while relevant in different contexts, do not function in the same manner as a direct acting controller. A reverse acting controller operates inversely; it would decrease line pressure in response to a rise in temperature. Parallel and compound controllers have their own specific applications but do not fit the scenario described, which focuses on the direct relationship between rising room temperature and increased line pressure.