Patent ID: 7402780

Claim:
A thermostat for controlling the operation of an air conditioning system and either a conventional heating system or a heat pump system with back up electric heating for a space, the thermostat comprising: a first connector for connecting to an air conditioning system; a second connector for connecting to either a conventional heat system or a heat pump reversing valve; a selection means for selecting from at least a first conventional heating mode of operation and a second heat-pump mode of operation of the thermostat; the first mode of operation being configured to establish air conditioning by providing an on signal to only the first connector and to establish heating by providing an on signal to only the second connector; the second mode of operation being configured to establish air conditioning by providing an on signal to only the first connector and an off signal to the second connector, and to establish heating by providing both an on signal to the first connector and an on signal to the second connector; where the thermostat is configured to detect when the second connector is connected to a conventional heating system and the second heat-pump mode of operation has inappropriately been selected, in which mode heating operation is established by an on signal to both the first and second connectors which causes the air conditioning system that is connected to the first connector and the conventional heating system that is connected to the second connector to be simultaneously operated, said thermostat being configured to detect the inappropriate selection by monitoring heating operation in the second mode by detecting a predetermined decrease in space temperature, and to responsively discontinue heating operation.