1. An economizer controller plug and play system recognition method performed by an economizer controller installed on-site for controlling an HVAC economizer system, the method comprising: the economizer controller discovering sensors connected to the economizer controller; the economizer controller repopulating a menu structure in accordance with control types of the discovered sensors; and the economizer controller repeating the method; and wherein the method is performed automatically by the economizer controller by executing a system configuration determination routine stored in firmware of the economizer controller.