Embodiments of the present disclosure are directed to a controller for a heating, ventilation, and/or air conditioning (HVAC) system. The controller is configured to operate in a first defrost mode or a second defrost mode, determine that feedback from a first sensor of the HVAC system is unavailable, receive feedback from a second sensor of the HVAC system, and operate the HVAC system in the second defrost mode instead of the first defrost mode in response to unavailability of the feedback from the first sensor and based on the feedback from the second sensor.

A monitoring system is configured to monitor a property. The system includes a sensor that is configured to generate sensor data that reflects an attribute of the property. The system further includes an HVAC system that is configured to generate and provide conditioned air to the property and that is configured to generate HVAC system data that reflects an attribute of the HVAC system. The system includes a monitor control unit that is configured to determine that the HVAC system is likely malfunctioning. The control unit is configured to receive the sensor data. The control unit is configured to determine that the HVAC system is likely operating correctly. The control unit is configured to determine a cause of the HVAC system transitioning from likely malfunctioning to likely operating correctly. The control unit is configured to update a model that is configured to identify causes of HVAC system malfunctions.

A monitoring system is configured to monitor a property. The system includes a sensor that is configured to generate sensor data that reflects an attribute of the property. The system further includes an HVAC system that is configured to generate and provide conditioned air to the property and that is configured to generate HVAC system data that reflects an attribute of the HVAC system. The system includes a monitor control unit that is configured to determine that the HVAC system is likely malfunctioning. The control unit is configured to receive the sensor data. The control unit is configured to determine that the HVAC system is likely operating correctly. The control unit is configured to determine a cause of the HVAC system transitioning from likely malfunctioning to likely operating correctly. The control unit is configured to update a model that is configured to identify causes of HVAC system malfunctions.

A climate control system that detects presence of a person in a room by analyzing small fluctuations in barometric pressure due to breathing. When the room is occupied, thermostatic control by the occupant may be enabled; when unoccupied, HVAC systems may be set to a low-power state. Barometric data may be processed using a bandpass filter that passes frequencies that correspond to typical human respiration rates. Barometric data may be used to determine when doors or windows are open or closed. Embodiments may connect to property management systems determine whether occupants are expected; when a room unoccupied but an occupant is expected, HVAC systems may be set to a standby state that saves power but allows temperature to return quickly to desired levels when a person enters the room. Occupancy detection may also use data from other sensors such as gas analyzers that detect compounds in exhaled breath.

A climate control system that detects presence of a person in a room by analyzing small fluctuations in barometric pressure due to breathing. When the room is occupied, thermostatic control by the occupant may be enabled; when unoccupied, HVAC systems may be set to a low-power state. Barometric data may be processed using a bandpass filter that passes frequencies that correspond to typical human respiration rates. Barometric data may be used to determine when doors or windows are open or closed. Embodiments may connect to property management systems determine whether occupants are expected; when a room unoccupied but an occupant is expected, HVAC systems may be set to a standby state that saves power but allows temperature to return quickly to desired levels when a person enters the room. Occupancy detection may also use data from other sensors such as gas analyzers that detect compounds in exhaled breath.

A fan motor stopping apparatus includes a conversion circuit that converts alternating-current voltage supplied from an alternating-current power supply into direct-current voltage, a smoothing capacitor that is connected to a fan motor included in an air conditioner and smooths the direct-current voltage from the conversion circuit, a voltage detection circuit that detects a voltage across the smoothing capacitor, and a fan motor shutdown circuit that suspends the fan motor in operation when the voltage detection circuit detects a voltage less than or equal to a threshold that is preset for suspending the operation of the fan motor.

A fan motor stopping apparatus includes a conversion circuit that converts alternating-current voltage supplied from an alternating-current power supply into direct-current voltage, a smoothing capacitor that is connected to a fan motor included in an air conditioner and smooths the direct-current voltage from the conversion circuit, a voltage detection circuit that detects a voltage across the smoothing capacitor, and a fan motor shutdown circuit that suspends the fan motor in operation when the voltage detection circuit detects a voltage less than or equal to a threshold that is preset for suspending the operation of the fan motor.

A control system for a heating, ventilation, and/or air conditioning (HVAC) system includes a controller. The controller is configured to control the HVAC system to condition an air flow based on first feedback from a first sensor of the HVAC system, receive second feedback from a second sensor of the HVAC system, and control the HVAC system to condition the air flow based on the second feedback instead of the first feedback when the first feedback from the first sensor being no longer available. The first feedback is indicative of a first operating parameter of the HVAC system, and the second feedback is indicative of a second operating parameter of a refrigerant flowing through the HVAC system.

A control system for a heating, ventilation, and/or air conditioning (HVAC) system includes a controller. The controller is configured to control the HVAC system to condition an air flow based on first feedback from a first sensor of the HVAC system, receive second feedback from a second sensor of the HVAC system, and control the HVAC system to condition the air flow based on the second feedback instead of the first feedback when the first feedback from the first sensor being no longer available. The first feedback is indicative of a first operating parameter of the HVAC system, and the second feedback is indicative of a second operating parameter of a refrigerant flowing through the HVAC system.

An air conditioning system includes a refrigerant cycle, a power feed unit, a controller, and a processor. The refrigerant cycle includes an outdoor unit and a plurality of indoor units. The outdoor unit includes a compressor. In a case where a power source for at least one indoor unit of the plurality of indoor units is interrupted, the power feed unit feeds power from an auxiliary power source to the at least one indoor unit. The controller controls at least the compressor. In the case where the power source for the at least one indoor unit of the plurality of indoor units is interrupted, the processor makes one of a determination to stop the compressor and a determination to cause the compressor to continue operating. The processor transmits to the controller an instruction corresponding to the determination that has been made.