An HVAC system includes a reversing valve configured to receive compressed refrigerant and direct the refrigerant based on an operating mode of the HVAC system. One or more suction-side sensors measure suction-side properties associated with refrigerant provided to an inlet of the compressor. The suction-side properties comprise a suction-side temperature. One or more liquid-side sensors measure liquid-side properties associated with the refrigerant provided from an outlet of the compressor. A controller monitors the suction-side property and liquid-side property. The controller determines whether the suction-side property is greater than the liquid-side property. If the suction-side temperature is greater than the liquid-side temperature, the reversing valve is determined to be in an equalizing configuration. The equalizing configuration corresponds to a configuration in which the refrigerant provided from the outlet of the compressor is directed to the inlet of the compressor without first being directed to other components of the HVAC system.

An HVAC system includes a compressor, condenser, and evaporator. A sensor measures a value associated with the refrigerant in the condenser or the evaporator, and a controller is communicatively coupled to the compressor and the sensor. The controller determines, based on an operational history the compressor, that pre-requisite criteria are satisfied for entering a sensor validation mode. After determining the pre-requisite criteria are satisfied, an initial sensor measurement value is determined. Following determining the initial sensor measurement value, the compressor is operated according to a sensor-validation mode. Following operating the compressor according to the sensor-validation mode for at least a minimum time, a current sensor measurement value is determined. The controller determines whether validation criteria are satisfied for the current sensor value. In response to determining that the validation criteria are satisfied, the controller determines that the sensor is validated.

A solar distillation system for producing a distillate and providing cooling for a structure or appliance, and a method of using the system to produce a distillate and cool a structure or appliance. The system includes a distillate cooling coil, a secondary cooling coil, an expansion valve which is capable of controlling an amount of a coolant that flows through each of the coils. The system also includes a compressor, a plurality of sensors including a temperature sensor and a distillate flow sensor, and a controller which receives input from the sensors and controls the activity of the compressor and expansion valve. The system is capable of producing distillate at night in the absence of solar radiation.

A system and a method are provided including a system controller for a refrigeration or HVAC system having a compressor rack with a compressor and a condensing unit with a condenser fan. The system controller monitors and controls operation of the refrigeration or HVAC system. A rack controller monitors and controls operation of the compressor rack. The system controller determines a flood-back discharge temperature corresponding to a flood-back condition, receives an actual discharge temperature associated with the compressor rack, compares the actual discharge temperature with the flood-back discharge temperature, and generates a notification to the rack controller based on the comparison.

Provided is a gas-liquid separator, including a connection pipe connected to a refrigerant pipe in the evaporator, the refrigerant pipe in which a two-phase refrigerant flows, a header connected to the connection pipe, wherein a gas refrigerant separated from the two-phase refrigerant flows inside the header, a bypass pipe connected to the header to guide a flow of the gas refrigerant to a compressor, a flow rate control valve installed at the bypass pipe, and a controller configured to control opening and closing of the flow rate control valve based on whether a preset condition is satisfied.

Systems and methods are disclosed for exchanging thermal energy between a drain liquid and a source liquid for heating or cooling of the source liquid. One method for heating a source liquid may involve transferring heat from a drain liquid using a heat pump. A system may include a refrigerant, a source liquid and a drain liquid, two or more heat exchangers that facilitate an exchange of thermal energy, and a means for transporting the refrigerant.

A cooling system is designed to operate in two different modes. Generally, in the first mode, when parallel compression is needed, certain valves are controlled to direct gaseous refrigerant from a tank to a compressor in the system and to direct refrigerant from low side heat exchangers towards other compressors. In this manner, a compressor in the system is transitioned to be generally a parallel compressor. In the second mode, when parallel compression is not needed, the valves are controlled to return the refrigerant flow back to normal.

A method operates an absorption heat pump system, specifically the flow of hydronic cooling fluid through the condenser during system start-ups, or when the cooling fluid temperature is low. To minimize the time for an absorption heat pump to reach full cooling or heating capacity, it is desirable for the high side pressure to increase as fast as possible, and the low side pressure to decrease as fast as possible. Since the high side pressure is a function of the temperature of the refrigerant exiting the condenser, if the condenser cooling fluid temperature is low, the corresponding high side pressure will be low, which may not permit adequate working fluid flow rates from the high pressure side of the system to the low pressure side.

The present invention provides a system and method for an improved multistage, cascade refrigeration system using hot gas defrost to rid the evaporator of ice build-up which accumulates over time, while the air in the evaporator enclosure remains below the freezing point of water. The present invention thus provides greater defrost flexibility with increased ease of design and implementation than current refrigeration systems, which allows for more robust hot gas defrost function for multistage refrigeration systems, such that it is unaffected by temperature changes of the condensing fluid (ambient air temperature for air cooled condensers, water temperature for water cooled condensers), and can be readily adapted to any refrigerant suitable for a selected temperature range.

A method and system for improving energy efficiency of a refrigeration system include system components such as a condenser, one or more expansion valves, an evaporator, one or more compressors, and a system controller electrically coupled to the one or more of the system components, according to one embodiment. The system controller is configured to selectively actuate, directly or indirectly, the one or more expansion valves, the condenser, and/or the one or more compressors, at least partially based on temperatures and/or pressures of the system fluid at various points of the system, to control a temperature of a refrigerated area.