A heat pump system includes a compressor, a usage side heat exchanger, a heat source side heat exchanger, an expansion mechanism, a main refrigerant flow control valve switchable between cooling and heating modes, a gas reheat heat exchanger, a fan, and a secondary refrigerant flow control device switchable between first, second, and third modes. Refrigerant flows from the compressor discharge line to the main refrigerant flow control device in the first mode. Refrigerant flows from discharge line to gas reheat heat exchanger and then main refrigerant flow control valve in the second mode. Refrigerant flows both from discharge line to gas reheat heat exchanger and then main refrigerant flow control valve, and from discharge line to main refrigerant flow control valve without flowing through the gas reheat heat exchanger in the third mode. Refrigerant flows to the usage side and hot gas reheat heat exchanger in the heating mode.

A heat pump system includes a compressor, a usage side heat exchanger, a heat source side heat exchanger, an expansion mechanism, a main refrigerant flow control device switchable between cooling and heating modes, a gas reheat heat exchanger, a fan, and a secondary refrigerant flow control device switchable between first, second, and third modes. Refrigerant flows from the compressor discharge line to the main refrigerant flow control device in the first mode. Refrigerant flows from discharge line to gas reheat heat exchanger and then main refrigerant flow control device in the second mode. Refrigerant flows both from discharge line to gas reheat heat exchanger and then main refrigerant flow control device, and from discharge line to main refrigerant flow control device without flowing through the gas reheat heat exchanger in the third mode. Refrigerant may flow to the usage side and hot gas reheat heat exchanger in the heating mode.

The purpose of the present invention is to provide a vehicle air conditioning system and a control method of the vehicle air conditioning system which enable detecting leaks of flammable refrigerant without requiring a separate sensor. This vehicle air conditioning system is provided with: a refrigeration cycle for cooling (23); a heat pump cycle for heating (33); a refrigerant that is very flammable, has an explosive range near room temperature, and circulates in the refrigeration cycle for cooling (23) and the heat pump cycle for heating (33); an outside temperature sensor (44) which detects the outside temperature; a pressure sensor (49) which detects the refrigerant pressure; and a control device which calculates the refrigerant density, which is the density of refrigerant, on the basis of the outside temperature and the pressure, and determines whether or not the refrigerant density has fallen below a prescribed threshold value which is based on the amount of sealed refrigerant, the total volume in the refrigeration cycle for cooling (23) and in the heat pump cycle for heating (33), the volume of the vehicle cabin, the standard density of the atmosphere, and the explosive limit of the refrigerant.

An outdoor unit according to the present disclosure includes: a compressor that sucks refrigerant, compresses the sucked refrigerant, and discharges the compressed refrigerant; a first refrigerant flow switching device that switches a flow passage for the refrigerant between a flow passage for a cooling operation and a flow passage for a heating operation; a heat-source-side heat exchanger that causes heat exchange to be performed between the refrigerant and external fluid; a heat-source-side backflow prevention device and a connection pipe that are included in a flow passage for the refrigerant in which an outlet from which the refrigerant flows to an outside region and an inlet into which the refrigerant flows from the outside region are unchanged regardless of which of the cooling operation and the heating operation is performed; and a flow passage pipe through which part of the refrigerant having flowed from the inlet passes in the cooling operation.

A refrigeration cycle apparatus includes a hot water tank, a heat source for heating water in the hot water tank, and a refrigeration cycle circuit that includes an indoor heat exchanger, a heat-source heat exchanger, and a water heat exchanger. The indoor heat exchanger may operate as a condenser. When an outside temperature is greater than a specified temperature, the refrigeration cycle apparatus operates in a first state in which the heat-source heat exchanger operates as an evaporator and the water heat exchanger does not operate. When the outside temperature is less than the specified temperature, the refrigeration cycle apparatus operates in a second state in which the water heat exchanger operates as an evaporator and refrigerant therein absorbs heat from water in the hot water tank heated by the heat source and the heat-source heat exchanger does not operate.

Embodiments relate generally to subcooling control of a heating, ventilation, and air conditioning (HVAC) system. An HVAC system may include a first electronic expansion valve (EEV) fluidly coupled to an indoor coil, wherein the first EEV is adjacent to the indoor coil. The HVAC system may also include a second EEV fluidly coupled to an outdoor coil, wherein the second EEV is adjacent to the outdoor coil. A system controller may be configured to control the first and second EEVs to control a flow of refrigerant to control subcooling (SC) produced by the HVAC system. The second EEV remains open during a cooling mode, and the first EEV modulates during the cooling mode. The second EEV modulates during a heating mode, and the first EEV remains open during the heating mode.

A method for air-conditioning of watercraft and the like using a device with: an electronically controlled variable-r.p.m. compressor, a main gas/water condenser (5), at least one environmental heat-exchanger (3) with an electronically controlled fan (14), at least one electronically controlled expansion valve (8), and at least one first electronic control unit (4) programmed for calculating continuously a temperature deviation detected (DeltaT=T_ad−T_a), and as a function of said temperature deviation regulating in combination, the r.p.m. of the compressor (1), opening of the flow valve (8), and the r.p.m. of the fan of the heat-exchanger (3).

A method of conditioning air includes controlling a secondary refrigerant flow control valve to select between a first mode in which refrigerant flows from a discharge line to a main refrigerant flow control valve, and a second mode in which refrigerant flows from the discharge line to a gas reheat heat exchanger and then flows to the main refrigerant flow control valve. A heat transfer medium flow control valve is controlled to adjust the flow of the heat transfer medium into a heat source side heat exchanger. The heat transfer medium flow control valve allows the heat transfer medium to flow to the heat source side heat exchanger when the secondary refrigerant flow control valve is in the first mode, and adjusts the flow of the heat transfer medium to the heat source side heat exchanger when the secondary refrigerant flow control valve is in the second mode.

A heat pump system includes a compressor, usage side heat exchanger, heat source side heat exchanger, expansion mechanism, main refrigerant flow control device switchable between cooling and heating modes, gas reheat heat exchanger connected in the refrigerant circuit, a fan disposed to direct an airflow across the usage side heat exchanger and the gas reheat heat exchanger into a target space, and a secondary refrigerant flow control device switchable between first and second modes. Refrigerant flows from the discharge line to the main refrigerant flow control device in the heating mode and the cooling mode in the first mode. Refrigerant flows from the discharge line to the gas reheat heat exchanger in a gas reheat mode and then flows to the main refrigerant flow control device in the second mode. A flow of the heat transfer medium to the heat source side heat exchanger is adjustable.

A pressure spike prevention assembly for use in a heat pump system includes a thermostatic expansion valve that includes a first port and a second port. The first port is designed to be fluidly coupled to an indoor coil, and the second port is designed to be coupled to an outdoor coil. The pressure spike prevention assembly further includes a multi-way valve that includes an inlet port, an output port, and a liquid line port. The inlet port is fluidly coupled to the first port. The output port is fluidly in communication with the second port. The liquid line port is configured to be fluidly coupled to a charge compensator of the heat pump system via a liquid line of the heat pump system.