Development of Power-head Based Fan Airflow Station

Fan airflow measurement is critical for heating ventilation and air conditioning (HVAC) system operation, control, and fault detection. It has been a challenge for HVAC professional. Since fan curves under a given fan speed can relate fan airflow to fan head or fan power, both fan head based and fan power based fan airflow stations have been developed and implemented in many air handling units (AHUs). The fan airflow station obtains the airflow based on the measured fan curve, fan speed and fan head or fan power. However, it is hard to obtain accurate fan curves since airflow measurement is still required to determine fan curves. On the other hand, the fan airflow can be obtained by measured fan power and fan head with fan efficiency curve. Since the fan efficiency varies slightly when the HVAC system airflow changes, the power-head based fan airflow station mainly depends on fan head and fan power measurement. The paper presents the theoretical models and the experiments of the power-head based fan airflow station.