The disclosed technology includes devices, systems, and methods for heat pump systems configured to operate in low ambient temperatures. The disclosed technology can include a heat pump water heater system having an evaporator, a first compressor configured to compress refrigerant to a first pressure, and a second compressor configured to compress the refrigerant to a second pressure. The second pressure can be greater than the first pressure. The heat pump water heater system can include a preheater configured to receive the refrigerant at the first pressure and heat water and a condenser configured to receive the refrigerant at the second pressure and heat water. The water can be passed through the preheater before being passed through the condenser.

The present disclosure provides a compressor with an oil equalizing pipe, a parallel compressor set, and an oil equalizing method. The compressor includes at least one oil equalizing pipe, an opening at one end of the oil equalizing pipe is formed in a target oil level of an oil sump, and the opening at the other end of the oil equalizing pipe is formed in a suction port; and when the oil level of the oil sump of the compressor is higher than the target oil level, the extra oil enters the suction port through the oil equalizing pipe. Compared with the prior art, the present disclosure has the advantages that, when the compressor is running, the gas in the suction port flows, so that the pressure at the suction port is less than the pressure on the surface of the oil sump; when the oil level of the oil sump of the compressor is higher than the target oil level, the extra oil enters the suction port through the oil equalizing pipe under the action of the above pressure difference, a part of the oil enters vortex and is discharged from the compressor via the exhaust port, and the oil discharged from the compressor returns to the other compressor lack of oil through a pipeline, thereby achieving oil balance between different compressors.

A system for modulating hot gas reheat operation of a heating, ventilation, and/or air conditioning (HVAC) system with multiple compressors, wherein the HVAC system is configured to regulate air provided to multiple zones. The system includes a controller configured to respond to a call for dehumidification in the absence of a call for cooling by sequentially energizing a first compressor of the multiple compressors in a reheat mode of the first compressor, energizing a second compressor of the multiple compressors in a cooling mode of the second compressor, energizing a third compressor of the multiple compressors in a reheat mode of the third compressor initially at full capacity, and energizing a fourth compressor of the multiple compressors in a cooling mode of the fourth compressor.

A refrigerant cycle apparatus, that circulates a flammable refrigerant in a refrigerant circuit, includes: a gas-side cutoff valve; a liquid-side cutoff valve, where the gas-side cutoff valve and the liquid-side cutoff valve are disposed on opposite sides of a first portion of the refrigerant circuit; a detection unit that detects refrigerant leakage from the first portion into a predetermined space; and a control unit that sets a cutoff state in the gas-side cutoff valve and the liquid-side cutoff valve when the detection unit detects the refrigerant leakage from the first portion into the predetermined space. The cutoff leakage rate at the gas-side cutoff valve is higher than the cutoff leakage rate at the liquid-side cutoff valve.

A heat pump system and a cooling/heating system using same, the heat pump system being able to prevent the occurrence of a vortex in a process in which fluid flows into a heat storage tank, and to supply and maintain constant-temperature cooling and heating. The heat pump system according to the present invention includes: an indoor unit which functions as a condenser during heating and functions as an evaporator during cooling; an outdoor unit which functions as an evaporator during heating and functions as a condenser during cooling; a heating medium for heat exchange; and a heat storage tank in which the heating medium for cold/hot water is stored.

A refrigeration cycle device includes: a refrigerant circuit which circulates a mixed refrigerant containing at least CF3I and HFO1123, the RC including a compressor, an expansion valve, an indoor heat exchanger, an outdoor heat exchanger and a refrigerant reservoir; an injection pipe having a first end at a first height within the refrigerant reservoir and a second end connected to the compressor; and an injection valve included in the injection pipe. The CF3I has the greatest fluid density among refrigerants contained in the mixed refrigerant. The first height is higher than a height at which an end of a refrigerant pipe, other than the injection pipe, is located within the refrigerant reservoir.

An air conditioner includes an outdoor unit including a compressor, an outdoor heat exchanger, and a switching device, an indoor unit including a first heat exchanger and a throttle regulator, a discharge pipe connected to a discharge side of the compressor, a low-pressure suction pipe connected to a low-pressure suction side of the compressor, a first piping connecting the discharge pipe, the outdoor heat exchanger, the throttle regulator, and the first heat exchanger in sequence, a second piping connecting the first heat exchanger and the low-pressure suction pipe, an economizer arranged at the first piping between the outdoor heat exchanger and the throttle device, and first and second refrigerant flow paths arranged in the economizer. Refrigerant flow directions in the first and second refrigerant flow paths are opposite to each other.

An economizer control system includes a compressor including a compression area, a piston chamber, and an economizer inlet configured to receive economizer vapor into the compression area via a flow path that extends between the economizer inlet and the compression area. At least a portion of the flow path traverses the piston chamber. The economizer control system also includes a piston disposed within the piston chamber and configured to contact the economizer vapor. The piston is moveable between an open position that opens the flow path and a closed position that closes the flow path. Additionally, the economizer control system includes a biasing system configured to apply force to the piston to bias the piston toward the closed position.

In a refrigeration cycle apparatus, a refrigerant pipe is connected to a compressor, a first heat exchanger, an expansion valve, a second heat exchanger, a heat absorber, and the compressor sequentially in this order. R290 is used as refrigerant flowing through the refrigerant pipe. The heat absorber is provided in a portion of the refrigerant pipe between the compressor and the first heat exchanger or the second heat exchanger serving as an evaporator. The heat absorber is disposed in contact with an electric component. A branch pipe is connected in parallel with the portion provided with the heat absorber in the refrigerant pipe. The branch pipe is provided with a flow rate regulating valve.

A refrigerant metering system/method incorporating a manual expansion valve (MEV), condenser isolation valve (CIV), flow isolation valve (FIV), and evaporator isolation valve (EIV) is disclosed. The MEV is configured to replace a conventional automated expansion valve (AEV) that controls a refrigerant flow valve (RFV) that is positioned in a heating, ventilation, and air conditioning (HVAC) system between a refrigerant condenser coil (RCC) and a refrigerant evaporator coil (REC) and permits manual metering of refrigerant by the RFV from the RCC to the REC and also allows complete shutoff of refrigerant flow by the RFV from the RCC to the REC. The MEV allows rapid HVAC repair and restoration of service where a replacement AEV is not readily available. The CIV/FIV/EIV are positioned in the refrigerant flow lines to permit the AEV and/or REC to be isolated from HVAC refrigerant flow for repairs to the AEV and/or REC.