Notes that centrifugal fans driven by single-speed induction motors have traditionally been used in the HVAC industry but have an airflow characteristic that depends on the static pressure seen by the system. Variable speed systems are starting to emerge as a strong alternative to traditional systems because of their ability to match the demand of the air-conditioned space, resulting in higher efficiencies and higher comfort. System efficiency can be improved by constraining the range of airflows provided by the fan or blower system in response to system pressure, that is, by controlling the airflow over the heat exchanger. Presents a method of regulating airflow independently of the static pressure and without the need for airflow sensors.

KEYWORDS: year 1996, ) Air flow, fans, electric motors, variable speed motors, algorithms, controls, heating, ventilation, air conditioning, efficiency