The present invention contemplates a method and apparatus for load-shedding duty cycling which overrides the normal thermostat control in a space conditioning system, upon receipt of an external signal as from the power company, in a manner such that the consumed power does not rise above the level that persisted just prior to the initialization signal. The present invention monitors the thermostat-controlled cycling pattern of a space conditioning system such as an air conditioner. Normally, the last thermostat-controlled cycle is then caused to become the reference or control cycle for the load shedding interval. That is, the ON portion of the reference cycle is caused to become the maximum allowable ON interval and the OFF portion of the reference cycle is caused to become the minimum OFF interval for the entire load shedding interval.
The device may be started by a single radio command or other means. The release from load control may be automatically timed or based on other signals. A radio receiver or other such means is provided to receive the signal from the power utility company which starts the load control function.
Unique features are also provided to prevent the undesirable effects of tampering with the thermostat setpoint just prior to the load shedding interval or to compensate for any cycle pattern of unusually long duration. This is done by compensating for the effect of these events by modifying the reference or control cycle when the appear.