AT-15-025 -- A Simplified Model of the Fan/Motor Performance of Fan-Powered Terminal Units That Use Electronically Commutated Motors ✓ Most Recent

Four manufacturers provided detailed performance dataon 36 fan/motor combinations applied in commercially availableseries and parallel fan-powered terminal units. The fanmotors ranged in size from 0.33 to 1 hp (249 to 746 W). Datawere provided for fan static discharge pressures ranging from0.1 to 0.75 in. w.g. (25 to 187 Pa). All of the fan motors wereelectronically commutated motors. The performance datawere analyzed to develop a generalized performance modelthat would be suitable for use in building energy simulationprograms. The model developed had two components. First,the data for static discharge pressures ranging from 0.1 to0.5 in. w.g. (25 to 125 Pa) were used to develop a correlationbetween the full-load power and the maximum airflow of thefan/motor combinations. These data were fit with a simplelinear regression model. Second, part-load power and airflowdata were evaluated over a wide range of controller settings foreach fan/motor combination. The data were normalized to theairflow and power corresponding to the maximum controllersetting for each static pressure. It was found that the normalizeddata for those fan motors whose full maximum poweroperations were less than 80% of the rating of the motor wereproblematic and were not used in the part-load evaluation.Thenormalized power and airflow were fit with a third-degreepolynomial. The resulting full-load power correlation alongwith the part-load correlation can be used together in a buildingsimulation program to estimate the part-load energy use offan/motor combinations used in fan-powered terminal unitsthat use electronically commutated motors.