Applying mass and energy balances to model series and parallel fan-powered terminal units.

Performance data from four manufacturers of fan-powered terminal units was analyzed and simple models of the fan/motor power use developed. These data included two fan motors: permanent split capacitor motors with silicon controlled rectifier control and electronically commutated motors. Fan sizes ranged from approximately 250 to 3500 ft³/min (0.118 to 1.65 m³/s) and motor sizes ranged from one-third to one hp (248.6 to 745.7 W). A mass and energy balance component approach was used to estimate the annual heating, cooling, and fan energy use of a five zone small office building that utilized a variable air volume system with fan-powered terminal units. Results were then compared to published results that used a systems approach to model fan-powered terminal units. Comparisons were made for five cities (Houston, New York, San Francisco, Chicago, and Phoenix). The two modeling approaches produced results that were within six percent of each other.