A refrigerant system includes a compressor configured to pressurize a refrigerant fluid. The compressor includes a sump portion. A heater is situated to heat at least the sump portion. A controller is configured to selectively operate the heater to apply heat to at least the sump portion while the compressor is off and continue operating the heater when the compressor turns on until a temperature of the compressor or a temperature of fluid discharged from the compressor satisfies at least one criterion.

A refrigeration apparatus (1) includes a main refrigerant circuit (2) including a positive displacement compressor (4), a condenser (6), an expansion valve (8), and an evaporator (10), through which a refrigerant circulates successively in a closed loop circulation, a lubrication refrigerant line (18) connected to the main refrigerant circuit (2) between the condenser (6) and the expansion valve (8) or to the condenser (6), in which circulates a portion of the refrigerant of the main refrigerant circuit (2) and connected to the compressor (4) for lubrication of the compressor (4) with the refrigerant. The lubrication refrigerant line (18) includes, upstream from the compressor (4): a throttle valve (20) adapted to vary the lubrication refrigerant flow entering the compressor (4), a downstream pressure detector (30) configured to measure refrigerant pressure (P3) downstream the throttle valve (20) and upstream the compressor (4).

A method of managing a compressor start operation, the method includes controlling a valve disposed upstream of a compressor to lower a saturated suction temperature of a refrigerant to be below an ambient temperature while starting the compressor.

Provided are a method and apparatus for controlling the operation of a compressor of an HVAC system in response to the refrigerant super heat value for refrigerant within the compressor. First and second signals are received for indicating one or more temperature values of refrigerant substantially at the first compressor sump and within the first distributor tube, respectively. A saturated suction temperature is estimated using at least the second signal. A first super heat value is calculated for refrigerant substantially at the first compressor sump using at least the saturated suction temperature and the one or more temperature values indicated by the first signal. A first control signal is generated for at least de-energizing the first compressor if the calculated first super heat value is below a tolerance value defining the minimum super heat value at which the first compressor may be operated.

A refrigeration apparatus (1) includes a main refrigerant circuit (2) including a positive displacement compressor (4), a condenser (6), an expansion valve (8), and an evaporator (10), through which a refrigerant circulates successively in a closed loop circulation, a lubrication refrigerant line (18) connected to the main refrigerant circuit (2) between the condenser (6) and the expansion valve (8) or to the condenser (6), in which circulates a portion of the refrigerant of the main refrigerant circuit (2) and connected to the compressor (4) for lubrication of said compressor (4) with the refrigerant. The lubrication refrigerant line (18) includes, upstream from the compressor (4): a throttle valve (20) adapted to vary the lubrication refrigerant flow entering the compressor (4), a downstream pressure detector (30) configured to measure refrigerant pressure (P3) downstream the throttle valve (20) and upstream the compressor (4).

A method of heating a component within a heating, ventilation and air conditioning (HVAC) system is provided. The method includes maintaining a non-heating condition of the HVAC system component when the HVAC system component is in a non-operational state. The method also includes determining when the HVAC system component will switch from the non-operational state to an operational state, the determination based on a threshold parameter being met. The method further includes operating a heating device from the non-heating condition to a heating condition to heat the HVAC system component from a temperature to a target temperature suitable for the operational state of the HVAC system component.

An air conditioner and a control method thereof are provided. The air conditioner includes: a compressor including a coil; an oil pool connected to the compressor through an oil piping; a main control board configured to receive a power-on signal of the air conditioner, obtain an actual temperature of the oil pool after receiving the power-on signal, generate a required heating amount in response to the actual temperature of the oil pool being lower than a preset startup temperature, and generate timing control signals according to the required heating amount; a power device, wherein two sides of the power device are respectively connected to the main control board and the coil, and the power device is configured to drive the coil to heat the oil pool according to the timing control signals generated by the main control board.

Provided are a method and apparatus for controlling the operation of a compressor of an HVAC system in response to the refrigerant super heat value for refrigerant within the compressor. First and second signals are received for indicating one or more temperature values of refrigerant substantially at the first compressor sump and within the first distributor tube, respectively. A saturated suction temperature is estimated using at least the second signal. A first super heat value is calculated for refrigerant substantially at the first compressor sump using at least the saturated suction temperature and the one or more temperature values indicated by the first signal. A first control signal is generated for at least de-energizing the first compressor if the calculated first super heat value is below a tolerance value defining the minimum super heat value at which the first compressor may be operated.

A climate-control system may include a compressor, a condenser, an evaporator, a first sensor, a second sensor, a third sensor, and a control module. The compressor may include a motor and a compression mechanism. The condenser receives compressed working fluid from the compressor. The evaporator is in fluid communication with the compressor and disposed downstream of the condenser and upstream of the compressor. The first sensor may detect an electrical operating parameter of the motor. The second sensor may detect a discharge temperature of working fluid discharged by the compression mechanism. The third sensor may detect a suction temperature of working fluid between the evaporator and the compression mechanism. The control module is in communication with the first, second and third sensors and may determine whether a refrigerant floodback condition is occurring in the compressor based on data received from the first, second and third sensors.

An air-conditioning apparatus includes: a refrigerant circuit in which a compressor, a four-way valve, a heat source-side heat exchanger, an expansion valve and a load-side heat exchanger are connected; and a controller which controls a refrigeration cycle in which refrigerant is circulated in the refrigerant circuit, to switch a flow passage for the refrigerant in accordance with which of a cooling operation, a heating operation and a defrosting operation is performed. The controller includes: a refrigeration-cycle control unit which controls the four-way valve to switch the flow passage of the refrigerant when the operation to be performed is switched from the heating operation to the defrosting operation; and a compressor control unit which sets an operation frequency of the compressor at a value lower than an operation frequency which is applied during the heating operation, when the operation is switched from the heating operation to the defrosting operation.