Performance of Parallel Fan-Powered Terminal Units with Electronically Commutated Motors
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Measurements were made on eight fan-powered terminal units that used electronically commutated fan motors. Semi-empirical models were developed for fan airflow output, fan power consumption, and primary airflow for parallel fanpowered variable-air-volume terminal units with electronically commutated motors. Units with both 8 in. (203 mm) and 12 in. (304 mm) primary inlets from three different manufacturers were tested. Fan power and airflow data were collected at downstream static pressures ranging from 0.1 to 0.5 in. w.g. (25 to 125 Pa). Upstream static pressures were varied from 0.0 to 2.0 in. w.g. (0 to 498 Pa). Data were collected at four different primary inlet damper positions and at four different control input volt-age settings to the electronically commutated motors. Model variables included primary air inlet damper position, input voltage setting, the air inlet differential sensor pressure, and the upstream (primary air) and downstream (supply air) static pressures. Each terminal unit was also tested with the fan off to characterize any leakage from the unit. Most of the resulting fan power and airflow models, except leakage, had R 2 values greater than 0.90. The models for terminal unit leakage had R 2 values that ranged from 0.826 to 0.972. These models could be used in HVAC simulation programs to estimate the performance of parallel fan-powered terminal units with electronically commutated motors. In addition, the potential savings of using EMC-versus SCR-controlled motors could be explored. 2011 ASHRAE.
