LAUSR

Part-load performance models for fans driven by electronically commutated motors in fan-powered terminal units were developed based on the analysis of data from 36 series and parallel units provided by four manufacturers. Fan motors ranged from 0.33 to 1 hp (249 to 746 W) and maximum external static pressures from 0.5 to 0.75 in. w.g. (125 to 188 Pa). Part-load performance was estimated from the intersection of the duct system and fan curves. The intersection of the two curves determined the external static pressure for estimating both fan airflow and power. Part-load airflow and power fractions were then estimated by using the airflow and power at the maximum airflow controller setting as the reference. The part-load curve tracked close to the fan law curve at airflow fractions above 0.4. The deviation between the two curves was 18.8% at an airflow fraction of 0.4 and increased at lower airflow fractions. The power consumption of motor controller may contribute to the deviation from the fan law curve at airflow fractions below 0.4. The model can estimate the part-load performance for fan-powered terminal units with electronically commutated motors in building simulation programs considering the wide range in fan motor sizes and maximum static pressures in the dataset.