An HVAC system includes an evaporator. The evaporator includes a sensor configured to measure a property value (i.e., a saturated suction temperature or a saturated suction pressure) associated with saturated refrigerant flowing through the evaporator. The system includes a variable-speed compressor configured to receive the refrigerant and compress the received refrigerant. The system includes a controller communicatively coupled to the sensor and the variable-speed compressor. The controller monitors the property value measured by the sensor and detects a system fault, based on the monitored property value. In response to detecting the system fault, the controller operates the compressor in a freeze-prevention mode, which is configured to maintain the property value above a setpoint value by adjusting a speed of the variable-speed compressor.

A system includes a pressure exchanger (PX). The PX is coupled to a motor that controls an operating speed of the PX. The system further includes a condenser. An outlet of the condenser is fluidly coupled to a first inlet of the PX. The system further includes a pressure gauge. The pressure gauge is configured to provide first pressure data. The first pressure data is indicative of a pressure of a fluid of the condenser. The system further includes a first controller configured to cause the motor to adjust the operating speed of the PX. The first controller causes the motor to adjust the operating speed of the PX based on the first pressure data.

A system includes a pressure exchanger (PX) configured to receive a first fluid at a first pressure and a second fluid at a second pressure and exchange pressure between the first fluid and the second fluid. The system further includes a condenser configured to provide corresponding thermal energy from the first fluid to a corresponding environment. The system further includes a first ejector to receive a first gas and increase pressure of the first gas to form the second fluid at the second pressure. The first ejector is further to provide the second fluid at the second pressure to the PX.

A refrigerant control system includes: a charge module configured to determine an amount of refrigerant that is present within a first portion of a refrigeration system within a building; and an isolation module configured to selectively open and close an isolation valve of the refrigeration system and to, via the isolation valve, maintain the amount of refrigerant within the first portion within the building below a predetermined amount of the refrigerant.

An air conditioner unit includes a compressor for circulating refrigerant through refrigeration loop, an indoor fan, and an outdoor fan. A controller is configured to operate the air conditioner unit in a standard mode of operation to heat a room, determine that an occupant is present in the room, and operate the air conditioner unit in an occupant mode of operation in response to determining that the occupant is present in the room. The occupant mode of operation includes adjusting at least one operating parameter of the air conditioner unit to increase a discharge temperature of a flow of indoor air relative to the standard mode of operation.

An air-conditioning apparatus includes outdoor units each including a compressor and outdoor heat exchanger, refrigerant flowing through the outdoor units; an indoor unit including an indoor heat exchanger, a heat medium flowing through the indoor unit; relay devices to which the outdoor units are connected, and to which the indoor unit is connected, each relay device includes a heat medium heat exchanger that exchanges heat between the refrigerant and the heat medium; and a controller. The controller controls action of the outdoor units, the indoor unit, and the relay devices. The controller determines necessity for a defrosting operation; responsive the defrosting operation being necessary, compares an indoor unit total load with an outdoor unit total capacity; and controls an operating frequency of the compressor of an outdoor unit other than the outdoor unit on which the defrosting operation is to be performed to increase the outdoor unit total capacity.

A refrigerant control system includes: a charge module configured to determine an amount of refrigerant that is present within a refrigeration system of a building; a leak module configured to diagnose that a leak is present in the refrigeration system based on the amount of refrigerant; and at least one module configured to take at least one remedial action in response to the diagnosis that the leak is present in the refrigeration system.

An HVAC system includes an evaporator. The evaporator includes a sensor configured to measure a property value (i.e., a saturated suction temperature or a saturated suction pressure) associated with saturated refrigerant flowing through the evaporator. The system includes a variable-speed compressor configured to receive the refrigerant and compress the received refrigerant. The system includes a controller communicatively coupled to the sensor and the variable-speed compressor. The controller monitors the property value measured by the sensor and detects a system fault, based on the monitored property value. In response to detecting the system fault, the controller operates the compressor in a freeze-prevention mode, which is configured to maintain the property value above a setpoint value by adjusting a speed of the variable-speed compressor. This prevents or delays freezing of the evaporator during operation of the system during the detected system fault.

A system includes a pressure exchanger (PX) configured to receive a first fluid at a first pressure, receive a second fluid at a second pressure, and exchange pressure between the first fluid and the second fluid. The first fluid is to exit the PX at a third pressure and the second fluid is to exit the PX at a fourth pressure. The system further includes a first heat exchanger configured to provide the first fluid to the PX and provide corresponding thermal energy from the first fluid to a third fluid. The system further includes a turbine configured to receive the third fluid output from the first heat exchanger. The turbine is further configured to convert corresponding thermal energy of the third fluid into kinetic energy.

A fluid handling system includes a pressure exchanger (PX) configured to receive a first fluid at a first pressure and a second fluid at a second pressure and exchange pressure between the first fluid and the second fluid. The system further includes a condenser configured to provide corresponding thermal energy from the first fluid to a corresponding environment. The system further includes a receiver to receive the first fluid output by the PX. The receiver forms a chamber to separate the first fluid into a first gas and a first liquid. The system further includes a first booster to increase pressure of a portion of the first gas to form the second fluid at the second pressure and provide the second fluid at the second pressure to the PX.