heat exchanger that might otherwise be lost in a similar manner the air conditioner compressor 24 is activated and deactivated by signals from the y terminal of the thermostat 29 at times t 5 and t 7 as shown again the signals to the fan motor 15 as received from terminal g of the thermostat 29 cause the fan to turn on at time t 6 and turn off at time t 8 to provide a similar on delay of time t 6 t 5 and an off delay of time t 8 t 7 the on delay allows for the air conditioning system to be operational for a sufficient time such that when the blower motor 15 comes on it is cooled air rather then hot air that is circulated similarly the off delay allows for the continued circulation of the residual cool air in the system after the air conditioner is turned off at time t 7 referring now to fig4 a flow chart of the present system is shown during the heating operation wherein a demand signal is generated at step 38 as determined by the difference between the said point of the thermostat and the actual temperature as indicated by the thermostat if the demand is greater than the specified off set as established by the operator and set into the thermostat then the heat is turned on as shown in steps 39 and 41 if the on delay timer.