An HVAC system is disclosed, comprising: (a) a compressor, (b) a source heat exchanger for exchanging heat with a source fluid, (c) a first load heat exchanger operable for heating/cooling air in a space, (d) a second load heat exchanger for heating water, (e) first and second reversing valves, (f) first and second 3-way valves, (f) a bi-directional electronic expansion valve, (g) a first bi-directional valve, and (h) a second bi-directional valve to modulate exchange of heat in the first load heat exchanger when operating as an evaporator and to control flashing of the refrigerant entering the source heat exchanger when operating as an evaporator, (h) a source pump for circulating the source fluid through the first load heat exchanger, (i) a water pump for circulating water through the second load heat exchanger, and (j) a controller to control operation of the foregoing.

A refrigeration cycle apparatus includes: a refrigerant circuit in which a compressor, a condenser, an expansion device, and an evaporator are connected by pipes, and refrigerant circulates; a high-pressure sensor that detects a pressure of the refrigerant on a discharge side of the compressor; a first temperature sensor that detects a temperature of the refrigerant on an outlet side of the condenser; and a controller that determines that the high-pressure sensor is abnormal, when the compressor is in operation and the temperature detected by the first temperature sensor is higher than a saturated liquid temperature or a saturated gas temperature that is calculated from the pressure detected by the high-pressure sensor.

A method for operating and controlling a vapor-compression cycle includes providing a system comprising an evaporator with a fan, a compressor, a condenser with a fan, an integrated expander, and a flash tank device with a vapor/liquid two-phase inlet and two outlets wherein a first outlet is a vapor outlet and a second outlet is a liquid outlet, and a metering valve; bringing a vapor-compression cycle up to steady-state at a fixed operating condition; opening the metering valve until the desired compressor suction superheat is achieved; and maintaining the desired degree of superheat by selectively increasing and decreasing superheat by reducing and increasing metering valve flow rate respectively.

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.

Disclosed is a CO.sub.2 based refrigeration system including a condenser for transferring heat from a CO.sub.2 refrigerant of the refrigeration system to an air stream. The system further includes a metering device downstream of the condenser and a bypass arrangement. The metering device is configured to create a pressure drop so that part of the refrigerant liquifies, when received in a supercritical state, from the condenser such that a liquid component and a flash gas component are generated. The bypass arrangement includes a valve and a bypass line to allow the refrigerant to bypass the metering device.

A method of operating a refrigeration and heating system (2a, 2b) comprises: circulating a refrigerant through a refrigeration circuit (4) which comprises in the direction of flow of the circulating refrigerant: at least one compressor (6a, 6b, 6c); a refrigeration circuit side (8a) of a coupling heat exchanger (8); at least one gas cooler (10); at least one expansion device (12, 14); and at least one evaporator (16); circulating a heating fluid through a heating circuit (20) which comprises a heating circuit side (8b) of the coupling heat exchanger (8) and at least one heat consumer (22); wherein the coupling heat exchanger (8) is configured for transferring heat from the circulating refrigerant to the circulating heating fluid. The method further includes increasing the temperature of the refrigerant entering the at least one gas cooler (10) in order to meet increased heating demands by allowing at least a portion of the heating fluid to flow directly from an outlet to an inlet of the heating circuit side (8b) of the coupling heat exchanger (8) bypassing the at least one heat consumer (22) or by allowing at least a portion of the refrigerant circulating through the refrigeration circuit (4) to bypass the coupling heat exchanger (8).

A heat pump includes a compressor, a metering device, a first heat exchanger, a second heat exchanger, a first fan, a second fan, and a refrigerant circuit between the first heat exchanger and the second heat exchanger. A thermal storage device coupled to the refrigerant circuit is configured to store thermal energy when the refrigerant fluid is above a threshold temperature and discharge thermal energy when the refrigerant fluid is below the threshold temperature. The heat pump is operated in a heating mode in which heat is transferred from the refrigerant fluid at the first heat exchanger and the temperature of the refrigerant fluid at the thermal storage device is above the threshold temperature, and a defrost mode in which heat is transferred to the refrigerant fluid at the first heat exchanger and the temperature of the refrigerant fluid at the thermal storage device is below the threshold temperature.

An HVAC system is disclosed, comprising: (a) a compressor, (b) a source heat exchanger for exchanging heat with a source fluid, (c) a first load heat exchanger operable for heating/cooling air in a space, (d) a second load heat exchanger for heating water, (e) first and second reversing valves, (f) first and second 3-way valves, (f) a bi-directional electronic expansion valve, (g) a first bi-directional valve, and (h) a second bi-directional valve to modulate exchange of heat in the first load heat exchanger when operating as an evaporator and to control flashing of the refrigerant entering the source heat exchanger when operating as an evaporator, (h) a source pump for circulating the source fluid through the first load heat exchanger, (i) a water pump for circulating water through the second load heat exchanger, and (j) a controller to control operation of the foregoing.

To improve the heat exchange efficiency of a heat exchanger that includes an upstream heat exchange unit and a downstream heat exchange unit. When the heat exchanger functions as an evaporator, a gas outlet pipe is an upstream refrigerant outlet that is located adjacent to the other end of upstream flat pipes of the upstream heat exchange unit, and a gas outlet pipe is a downstream refrigerant outlet that is located adjacent to the other end of downstream flat pipes of the downstream heat exchange unit. First resistance to refrigerant flow in the upstream heat exchange unit and second resistance to refrigerant flow in the downstream heat exchange unit are adjusted in order that the degree of superheating of refrigerant at the downstream refrigerant outlet is smaller than the degree of superheating of refrigerant at the upstream refrigerant outlet.

A charge-verification system for a circuit including a condenser having an inlet, an outlet, and a coil circuit tube extending between the inlet and the outlet is provided. The charge-verification system may include a first of coil temperature sensor located on the coil circuit tube a first distance from the inlet and a second of coil temperature sensor located on the coil circuit tube a second distance from the inlet. The charge-verification system may also include a controller receiving a first signal from the first temperature sensor indicative of a first temperature and a second signal from the second temperature sensor indicative of a second temperature. The controller may determine which of the first signal and the second signal is closer to an actual saturated condensing temperature of the condenser.