VC-20-007 — Using Normalized Airflows and Powers to Model the Performance of Multispeed Fan-Coil Units with Permanent Split Capacitor Fan Motors (RP-1741)

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Conference Proceeding by ASHRAE, 2020



Four manufacturers provided laboratory airflow and power data as a function of external static pressure for 37 multispeed fan-coil units with permanent split capacitor motors. These data were used to develop an airflow performance model of fan-coil units that could be implemented in a building simulation program. The fan-coil units had fan motors ranging from 0.033 hp to 0.75 hp (25 W to 560 W) and maximum airflows that ranged from 242 ft3/min to 2646 ft3/min (0.11 m3/s to 1.25 m3/s). The model included normalized fanmotor power and fan airflow at each speed setting. The normalized power versus normalized airflow data for the range of external static pressures typically plotted in a grouping of data at each speed setting. These average normalized powers and airflows were evaluated for each unit. The normalized values were combined with a linear fit to the high airflow and power curves to develop a straightforward process for generating airflow and power curves as a function of external static pressure. A procedure was developed to determine the intersection of the air system curve with the fan-coil airflow and power curves. The resulting model could be used to describe the airflow and power performance of a specific manufacturer’s permanent split capacitor fan-coil unit over multiple speeds and external static pressures.

Citation: 2020 Virtual Conference Technical Papers

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