HVAC system with improved control switching

A heating, ventilation, and/or air conditioning (HVAC) system, comprising:

• an alternating current (AC) power source;
• a thermostat comprising at least one external control signal relay connected to the AC power source;
• an interlock switch connected to the AC power source;
• a full wave rectifier configured to receive an alternating current (AC) from the AC power source and output a direct current (DC) when each of the at least one external control signal relay and the interlock switch are closed;
• and
• a power relay activation control circuit comprising at least one capacitor, wherein the power relay activation control circuit is configured to receive the direct current from the full wave rectifier and provide actuation control of a power relay in response to a voltage exceeding a predetermined threshold switching voltage.

A method of operating a heating ventilation and/or air conditioning (HVAC) system, comprising:

• providing an alternating current (AC) power source to a thermostat comprising at least one external control signal relay connected to the AC power source;
• providing an interlock switch coupled to the thermostat;
• receiving an alternating current (AC) from the AC power source and outputting a direct current (DC) when each of the at least one external control signal relay and the interlock switch are closed;
• receiving the direct current from the full wave rectifier by a power relay activation control circuit;
• and
• actuating control of a power relay in response to a voltage exceeding a predetermined threshold switching voltage.