Variable-frequency drives (vfd’s) are used to regulate flow on supply and return air-handling units, ventilation systems, cooling tower fans, and recirculating pumps, as well as some refrigeration compressors.
“These vfd’s have come a long way in technology and value since their troublesome introduction into variable air volume systems just 20 years ago,” said John Drews, director of hvac sales, AC Technology Corp., Uxbridge, MA.