A system and method of operating an HVAC system including a HVAC unit including a unit temperature sensor, a unit controller, and a variable speed compressor, and a two-stage system controller in communication with the unit controller, the method including operating the system controller to transmit a conditioning signal to the unit controller based in part on a system demand, operating the unit controller to receive the conditioning signal, and receive outdoor air temperature data from the unit temperature sensor, operating the unit controller to determine whether the outdoor air temperature data is greater than or equal to a cooling temperature limit or less than or equal to a heating temperature limit, and operating the unit controller to transmit a speed signal to the compressor based in part on the plurality of conditioning signals and the outdoor air temperature data.