The heat pump components are controlled by a three stage room thermostat model in TRNSYS. The thermostat employs night setback and a deadband and operates in the following manner:

HEATING:

If the room temperature falls below the user-specified set point for heating minus the thermostat deadband, the thermostat will call for heating by the heat pump and provide enable signals to the ground loop pump, the fan, and the domestic hot water loop pump. If the room temperature continues to fall further and reaches the auxiliary heating set point minus the deadband, the thermostat will call for auxiliary heating by the electric resistance heater. The fan, ground loop pump, and domestic hot water loop pump will remain on. The auxiliary heater will remain on until room temperature rises above the auxiliary heater set point temperature at which point the auxiliary heater will shut off; leaving the ground loop pump, the fan, and the hot water loop pump on. The heat pump, ground loop pump, hot water loop pump, and fan will remain on until the room temperature rises above the heating set point temperature.

COOLING:

If the room temperature rises above the user-specified set point for cooling plus the thermostat deadband, the thermostat will call for cooling by the heat pump and provide enable signals to the ground loop pump, the fan, and the domestic hot water loop pump. The heat pump, ground loop pump, hot water loop pump, and fan will remain on until the room temperature falls below the coling set point temperature.