Patent ID: 8708242

Claim:
A thermostat adapted for direct connection to a Heating, Ventilation, and Air Conditioning (HVAC) system and an intermediate auxiliary HVAC control unit, the thermostat comprising: a plurality of wiring terminals each adapted to make electrical connection with one of a plurality of control wires running between a first location where the thermostat is installed and a second location where the HVAC system is installed; and processors and circuitry configured and programmed to communicate with the intermediate auxiliary HVAC control unit directly at the second location via one or more of the plurality of control wires connected to one or more of the plurality of wiring terminals, the intermediate auxiliary HVAC control unit being directly electrically connected to the HVAC system via a plurality of HVAC control wires, the processors and circuitry further configured and programmed to: automatically determine whether the intermediate auxiliary HVAC control unit is installed, or whether the intermediate auxiliary HVAC control unit is not installed and the plurality of control wires are connected directly to both the plurality of wiring terminals and to the HVAC system; operate in a first mode to control the HVAC system directly and receive electrical power directly from the HVAC system when the intermediate auxiliary HVAC control unit is not installed and the plurality of control wires are connected directly to both the plurality of wiring terminals and to the HVAC system; and operate in a second mode to control the HVAC system indirectly by electronically re-purposing at least one of the plurality of control wires such that the thermostat communicates with and receives electrical power from the intermediate auxiliary HVAC control unit when the intermediate auxiliary HVAC control unit is installed.