LOW TEMPERATURE COMPRESSOR LOCKOUT SWITCH—The Economizer is equipped with a low ambient temperature lockout switch located in the outdoor airstream which is used to lock out the compressors below a 42_F (5.6_C) ambient temperature.
Economizer Control Modes—Determine the Economizer control mode before set up of the control. Some modes of operation may require different sensors. Refer to Table 11. The Economizer is supplied from the factory with a supply air temperature sensor, a low temperature compressor lockout switch, and an outdoor air temperature sensor. This allows for operation of the Economizer with outdoor air dry bulb changeover control. Additional accessories can be added to allow for different types of changeover control and operation of the Economizer and unit.
OUTDOOR DRY BULB CHANGEOVER— The standard controller is shipped from the factory configured for outdoor dry bulb changeover control. The outdoor air and supply air temperature sensors are included as standard.
For this control mode, the outdoor temperature is compared to a selectable set point on the sensor. See Fig. 40. If the outdoor-air temperature is above the set point, the Economizer will adjust the outdoor air dampers to minimum position. If the outdoor-air temperature is below the set point, the position of the outdoor-air dampers will be controlled to provide free cooling using outdoor air. When in this mode, the LED next to the free cooling set point potentiometer will be on. The changeover temperature set point is set using the switches on the sensor. See Fig. 40 for the corresponding temperature changeover values.
In this mode of operation, the outdoor-air temperature is compared to the return-air temperature and the lower temperature airstream is used for cooling. When using this mode of changeover control, turn the free cooling/enthalpy set point potentiometer fully clockwise to the D setting. See Fig. 39 and Fig. 44.
EXHAUST FAN
SETPOINT
LED LIGHTS WHEN
EXHAUST CONTACT
IS MADE
MINIMUM DAMPER 
POSITION SETTING
MAXIMUM DAMPER DEMAND
CONTROL VENTILATION
SETPOINT
LED LIGHTS WHEN
DEMAND CONTROL
VENTILATION INPUT
IS ABOVE SETPOINT
DEMAND CONTROL
VENTILATION SETPOINT
LED LIGHTS WHEN
OUTDOOR AIR IS
SUITABLE FOR FREE
COOLING
ENTHALPY
CHANGEOVER SETPOINT
A09708
Fig. 39 - Economizer Controller Potentiometer and LED
Locations
