Despite the economic advantages and significant energy savings available by using AC variable-frequency drives (VFDs) in HVAC applications, many building operators do not repair or replace drives when they fail because the motors can easily continue to run through a bypass contactor. While this is a great solution for short-term outages, continued operation in this mode quickly becomes an expensive way to operate a fan.
Budget cuts and competitive pressures have reduced building maintenance staffs in many public and private enterprises. This frequently results in a reprioritization of activities, forcing concentration on addressing issues that are required to be fixed at the moment. Repair items such as an HVAC drive system operating in bypass mode may be considered only a nuisance to be dealt with as time permits. And of course, time seldom permits.