The JADE™ Economizer System is an expandable economizer control system, which includes a W7220 Economizer Module (controller) with an LCD and keypad. The W7220 can be configured for 4 different economizer strategies: referential or differential dry bulb, referential or differential enthalpy. The W7220 Economizer Module can be used as a stand-alone economizer module wired directly to a commercial set back space thermostat and sensors to provide Outdoor Air dry-bulb economizer control. The W7220 Economizer Module can be connected to optional Silk Bus sensors for single or differential enthalpy control. The W7220 Economizer Module provides power and communications on the Silk Bus for the Silk Bus sensors. The W7220 Economizer Module automatically detects sensors by polling to determine which sensors are present. If a sensor loses communications after it has been detected, the W7220 Economizer indicates a device fail error on the display or through the AUX 1 OUT terminal programmed to SYS.