Refrigeration Plant Operator B Full Practice Test 2025

The primary function of a flow switch, also known as a sail switch, in relation to hot water coils is to ensure that there is consistent water flow through the system. When water flow is detected, the flow switch allows the system to operate normally, which includes keeping the outside air dampers open and the fan running to maintain proper ventilation and temperature control.

If the water flow is interrupted—either due to pump failure, a blockage, or any other issue—the flow switch will activate and trigger the closure of the outside air dampers and stop the fan. This is crucial because operating the heating coils without adequate water flow can lead to overheating and potential damage to the coils due to the lack of cooling. By closing the dampers and stopping the fan, the system protects itself from possible harm while preventing cold air from entering the space that is being heated.

Looking at the other options: regulating the temperature of water and controlling humidity levels pertain to different aspects of HVAC systems and do not directly involve the role of the flow switch, while monitoring the pressure of the steam relates to steam systems rather than water flow in hot water coils. The key function here is the safety mechanism provided by the flow switch in managing airflow in response to water flow conditions.