The MC4002 has 2 stages of cooling control available for each connected air conditioner. It is designed for systems with or without economizers and for systems with 2-stage or dual compressors. The 2nd stage available for each air conditioner permits complete and proper control when economizers are installed or when 2-stage or dual compressors are utilized. With the addition of a simple 2 wire humidity controller as an input signal, it can provide electric reheat dehumidification circuit. The controller can also be configured for use with heat pumps. (NOTE: The electric reheat dehumidification feature is not available when configured for heat pumps). The MC4002, either in basic form or when equipped with optional alarm relay boards, is a fully functional controller with unique configurable capability. The MC4002 can be ordered as a basic controller only or factory equipped with one of two variations of alarm boards with varying amounts of alarm capabilities to fit the user’s requirements. Ethernet communication option is also available. If only the base controller is initially installed, it can be easily upgraded by simple snap-in of the alarm relay board and plug-in of the communication cable to the main controller board. Form C dry contact alarm relays are used, offering both NO and NC switching to meet the user’s specific alarm protocol, providing complete flexibility to meet any user’s requirements. All alarm actuations are individually indicated on the controller front panel, along with indication for active stages of cooling or heating, and which unit is currently “lead”. A digital display indicates building temperature and is also used for all of the programming functions.