ZOO Fans’ Advanced Variable Speed Transformer Controller is an autotransformer based microprocessor controller designed to provide various options for the control of ZOO Fans. This Controller supports dynamic speed control for quiet, variable speed operation of the fans, and eliminates the undesirable motor hum often associated with Triac controllers. The fans can be controlled via Building Automation Systems (BAS), Manually (MAN), or Automatically (AUTO) with the addition of two dedicated temperature sensors. AUTO operation is based on the temperature difference (delta T) between these two sensors, typically placed near the floor and the ceiling. Fan speed and airflow are automatically controlled, based on the delta T and on the ceiling height as programmed via the configurable User Interface. Dynamic management of fan speed via the AUTO function or via BAS, typically results in fans running at lower speeds overall, while still maintaining thermal equilibrium in the space. By defaulting to LOW fan speed instead of OFF, constant background mixing continues to maintain comfort levels and save energy by supporting existing HVAC.