The re-use of return air in central conditioning systems is one of the most important procedures for saving power consumption. However, the requested fresh air of the people existed within the conditioning space imposes determining the number of times to be used. This research aims to link the work of the central conditioning system (heating) of a facility with the number of people existing within this facility by modifying the ratio of mixed fresh air and return air to save the electrical power consumption. Also, to raise the temperature of the mixture air by controlling the flow of hot water continuously rather than using on-off technique. As well as, to respond to any change in the number of people and get rid of repeated machine starting. Our research has been done by using specialized physical model consisted of test room, heat and movement sensors, pump, water tank, heat exchanger and air mixing blades. These devices are controlled by microcontroller type PIC16F877A. The experimentally obtained results showed the ability of controlling the amount of return air depending on the number of people and controlling the speed of the pump continuously providing a saving of electrical energy consumption up to 68% compared with the case of full speed.