this is a new standard, it will increase the service calls and it's going to cost you more money. Technology is very useful when used correctly, with the advancement there are new processes and procedures. A lot of the variable speed motors have up to 15 profiles that help create a perfect flow rate(velocity) and remove more or less humidity. Compared to the PSC Fan motors and there 4-speed ability the variable speed fans are superior. PSC is much less efficient fan motors that require capacitors, they have been in use for a very long time. With the PSC motor, you have a motor that comes on at one speed and the airflow to the unit will not affect the speed of the motor .with a variable speed motor its using sensors to validate volume of air and in instances where there is not enough air the unit will have a symptom of “hunting” where the motor ramps up and down to maintain the airflow pressure inside the unit.
