Abstract: This relates to a thermodynamic electronic actuator for intermittently controlling the operation of a heating and/or air conditioning system for any temperature controlled area when a door or window is left open or ajar. The actuator circuit comprises a normally-closed switch (or switches if used for more than one opening), which initiates operation of a count-up timer to interrupt the thermostat line after a predetermined period whenever a door or window is left open. To restore power, all that is required is to shut the window or door. This actuates a count-down timer that will restore the thermostat line after a predetermined period, assuming the window or door is not reopened, interrupting the countdown.