Empirical performance models of fan airflow, primary airflow and power consumption weredeveloped for series and parallel variable air volume fan powered terminal units. Anexperimental setup and test procedure were created to test the terminal units at typical designpressures and airflows. Each terminal unit observed in this study used an 8 in (20.3 cm) primaryair inlet. Two fan motor control methods were considered. The primary control of interest wasthe electronically commutated motor (ECM) controller. Data collected were compared withprevious research regarding silicon rectified control (SCR) units. Generalized models weredeveloped for both series and parallel terminal units. Coefficients for performance models werethen compared with comparable SCR controlled units. Non-linear statistical modeling wasperformed using SPSS software (2008).In addition to airflow and power consumption modeling, power quality was also quantified.Relationships between real power (watts) and apparent power (VA) were presented as well asharmonic frequencies and total harmonic distortion. Power quality was recorded for each ECMcontrolled terminal unit tested. Additional tests were also made to SCR controlled terminal unitsused in previous research (Furr 2006).The airflow and power consumption performance models had an R2 equal to 0.990 or greater forevery terminal unit tested. An air leakage model was employed to account for leakage in theparallel designed VAV terminal units when the internal fan was turned off. For the leakagemodel, both ECM and SCR controlled units achieved an R2 greater than or equal to 0.918.
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