Load control system and method for regulating power supply to a thermostat

A method of controlling a load control relay (LCR) for a heating, ventilating, and air conditioning (HVAC) system having a thermostat and a load control line coupling the thermostat to a load, the method comprising:

• measuring a thermostat-induced delay between a time the LCR is restored and a time power is received on the load control line;
• defining a compensation time to offset the thermostat-induced delay;
• calculating a new cycle shed time and a new cycle restore time based on the compensation time;
• and
• controlling the LCR according to the new cycle shed time and the new cycle restore time.

A load control system for selectively supplying power to a thermostat of a heating, ventilating, and air conditioning (HVAC) system, the load control system comprising:

• a load control relay (LCR) coupleable to the HVAC system;
• a sensor configured to sense whether a load control line for a load of the HVAC system is active;
• a communication system capable of communicating with a master station to receive a control command comprising a shed percentage and one of a control duration and a cycle period for controlling the LCR;
• and
• a controller for selectively controlling the LCR according to the control command, the controller programmed to:
• calculate a cycle shed time and a cycle restore time based on the control command;
• control the LCR according to the cycle shed time and the cycle restore time;
• determine a thermostat delay between a restore time of the LCR and a time the sensor senses that the load control line is active;
• modify the cycle shed time and the cycle restore time based on the thermostat delay to counteract the thermostat delay;
• and
• control the LCR according to the modified cycle shed time and the modified cycle restore time.