US Patent 10047969 Energy saving controller

A method for controlling an air handler including a fan and a heater or a compressor, the method including installing an energy saving controller (“ESC”) between a thermostat and the air handler, monitoring by the ESC of ON and OFF durations of the heater if the air handler is in a heating mode, or the compressor if the air handler is in cooling mode, in a first cycle and of ON duration of a second cycle, and determining the fan's first run time extension amount based on the ON and OFF durations of the first cycle and the ON duration of the second cycle.