Modeling the Performance of ECM and SCR Series Fan-Powered Terminal Units in Single-Duct VAV Systems Conference Paper uri icon


  • Single-duct variable-air-volume systems often use series-and parallel-fan-powered terminal units to control the airflow in conditioned spaces. A laboratory-verified model of single--duct variable-air-volume systems was developed to simulate both series and parallel fan terminal units where the terminal unit fans are controlled by either silicon-controlled rectifiers or electronically commutated motors. The paper provides the equation needed to simulate the performance of a fan-powered terminal unit. The simulation model developed here includes a five-zone office building whose performance was simulated in five cities in the United States: Houston, Phoenix, Chicago, New York, and San Francisco. The model includes total plant energy, total cooling plant energy, primary fan energy, terminal unit fan energy, and heat energy added. The single-duct variable-air-volume simulation results showed that the reduction in the annual energy used by the office building with series-fan-powered terminal units having electronically commutated motors compared to series units having silicon-controlled rectifier-controlled motors varied by location. The largest energy savings for the building was in Phoenix (8.4%), while the smallest was in Chicago (5.9%). In all cases, the reduction in electricity used by the terminal unit fans with electronically commutated motors was near 65%). These results indicate that using fan-powered terminal units with electronically commutated motors offers the potential for sizable savings in energy compared to units with silicon-controlled rectifier-controlled motors. 2012 ASHRAE.

published proceedings


author list (cited authors)

  • Davis, M. A., Bryant, J. A., & O'Neal, D. L.

complete list of authors

  • Davis, Michael A||Bryant, John A||O'Neal, Dennis L

publication date

  • January 1, 2012 11:11 AM