Part 1 states that for several years, electronic variable speed drives (VSDs) have been used on fan motors in large building variable air volume ventilation systems to replace inlet vanes. In Part 1 presents a case study of a VSD retrofit in which the drives were installed on four fan motors in an office building. Examines fan motor performance using analysis of motor input power as a function of airflow. States the analysis shows that, despite considerable savings over inlet vanes (35%), the high cost of VSDs results in a relatively long payback period. Measurements showed that reducing supply duct static pressure can significantly boost the savings achievable with VSDs.

KEYWORDS: Fans, ventilation, energy conservation, modernising, controls, calculating, air flow, variable volume air conditioning, offices, case studies, pressure, algorithms, static pressure, computer controls, models