The mixing box contains the following controls:
- TRANSFORMER (40VA) - Furnishes 24V AC to damper motor through economizer relay, mixed air sensor and potentiometer. The primary of the transformer is either 115V or 230V (consult wiring diagram).
- DAMPER MOTOR (DM) - A 24V motor to drive the damper blades open and closed. The 24V power drives the motor in one direction and an internal spring drives the motor in the opposite direction.
- ENTHALPY CONTROL (EC) - An adjustable single pole, double throw temperature and humidity (enthalpy) sensing relay that determines if outside air can be used instead of mechanical cooling.
- MIXED AIR SENSOR (MS) - A non-adjustable thermistor that senses the mix of return air and fresh air and signals the damper motor to move the two dampers to maintain the proper mix of air.