Performance of ECM Controlled VAV Fan Powered Terminal Units
Cramlet, Andrew Charles
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Empirical performance models of fan airflow, primary airflow and power consumption were developed for series and parallel variable air volume fan powered terminal units. An experimental setup and test procedure were created to test the terminal units at typical design pressures and airflows. Each terminal unit observed in this study used an 8 in (20.3 cm) primary air inlet. Two fan motor control methods were considered. The primary control of interest was the electronically commutated motor (ECM) controller. Data collected were compared with previous research regarding silicon rectified control (SCR) units. Generalized models were developed for both series and parallel terminal units. Coefficients for performance models were then compared with comparable SCR controlled units. Non-linear statistical modeling was performed 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 as harmonic frequencies and total harmonic distortion. Power quality was recorded for each ECM controlled terminal unit tested. Additional tests were also made to SCR controlled terminal units used in previous research (Furr 2006). The airflow and power consumption performance models had an R2 equal to 0.990 or greater for every terminal unit tested. An air leakage model was employed to account for leakage in the parallel designed VAV terminal units when the internal fan was turned off. For the leakage model, both ECM and SCR controlled units achieved an R2 greater than or equal to 0.918.