A heating, ventilation, and air-conditioning (HVAC) system comprises a plurality of sensors, a tandem compressor comprising a first compressor and a second compressor, and a controller communicatively coupled to the plurality of sensors and the tandem compressor. The controller is operable to operate threshold logic that turns off the tandem compressor if the tandem compressor is operating outside of a threshold range. The controller is further operable to determine a temperature demand of a structure associated with the HVAC system based on data received from at least one of the plurality of sensors and determine that the HVAC system requires a change of state to meet the temperature demand. The controller may disable the threshold logic for a pre-determined period of time in response to determining that the HVAC system requires the change of state and perform the change of state independently of the threshold logic.

The purpose of the present invention is to provide a refrigerator in which the capacity of an oil tank can be made smaller than in the prior art while a foaming phenomenon is addressed. The refrigerator is provided with: a refrigeration cycle which includes a condenser, an evaporator, and an electric compressor having a compression mechanism to be driven by a motor and in which a refrigerant circulates; an oil tank in which a lubricating oil is stored; a heater which is set in the oil tank and which heats the lubricating oil; a lubricating oil supply line which is connected to the oil tank and which supplies the lubricating oil from the oil tank into a housing having the motor housed therein; a lubricating oil discharge line which returns the lubricating oil from the housing back to the oil tank; a pressure equalizing pipe which has one end connected to the oil tank and the other end connected to the refrigeration cycle; and a buffer tank which is set to the pressure equalizing pipe, which receives the refrigerant and the lubricating oil flowing out from the oil tank, and in which the lubricating oil is stored.

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.

A compressor may include a shell containing a motor, a compression mechanism and a lubricant sump. The compressor may also include first and second temperature sensors, and a control module. The first temperature sensor may be at least partially disposed within the lubricant sump and may measure a first temperature of a lubricant at a first position. The second temperature sensor may be at least partially disposed within the lubricant sump and may measure a second temperature of the lubricant at a second position that is vertically higher than the first position. The control module is in communication with the first and second temperature sensors. The control module may determine a first difference between the first temperature and the second temperature. The control module may determine whether a liquid level of the lubricant in the lubricant sump is below a predetermined level based on the first difference.

A method for managing and controlling a heat pump based on a compression/expansion thermodynamic cycle of an operating fluid including at least: first and second heat exchangers; an expansion valve; and a compressor. The compressor is able to suck and compress a wet operating fluid. A plurality of temperature sensors detects the delivery temperatures Tm of the compressor, an evaporation temperature SST in the first exchanger, and a condensation temperature SDT in the second exchanger. The temperature difference between the lubricating oil in the compressor and the operating fluid at the compressor delivery is kept equal to or greater than a safety threshold OIL_SH such that there is no condensation of the operating fluid in the lubricating oil.

A compressor includes a shell, a first temperature sensor, a second temperature sensor, and a control module. The shell includes a motor, a compression mechanism and a lubricant sump. The first temperature sensor is at least partially disposed within the shell and configured to measure a first temperature of a lubricant at a first position. The second temperature sensor is at least partially disposed within the shell and configured to measure a second temperature of the lubricant at a second position that is vertically higher than the first position. The control module is in communication with the first and second temperature sensors and configured to determine a first difference between the first temperature and the second temperature. The control module is configured to determine whether a liquid level of the lubricant in the lubricant sump is below a predetermined level based on the first difference.

An HVAC system includes a plurality of sensors, a tandem compressor, and a controller. The tandem compressor comprises a first and second compressor, each comprising a crankcase heater. The controller determines that one of the sensors has failed, and in response, initiates the first and second crankcase heaters and transmits an alert indicating that one of the sensors has failed. Further, the controller may disable threshold logic such that the first and second compressors are controlled independently of a determination whether the tandem compressor is operating outside of a threshold range. The controller operates the first and second compressors according to a safe mode, wherein first on or off settings of the compressors are determined based on a first required load operation of the tandem compressor. The first required load operation is determined from a first temperature demand of a structure associated with the HVAC system.

In a case where a concentration of refrigeration oil detected by the concentration sensor is less than a first threshold value, the control device operates the heater such that a part of a refrigerant in a liquid state in the compressor is vaporized, and in a case where the concentration of the refrigeration oil detected by the concentration sensor exceeds a second threshold value greater than the first threshold value and a temperature of the refrigeration oil detected by the temperature sensor is less than a specified temperature, the control device operates the heater such that the refrigerant in the liquid state in the compressor is vaporized and the temperature of the refrigeration oil in the compressor is increased.

An HVAC system includes a plurality of sensors, a tandem compressor, and a controller. The tandem compressor comprises a first and second compressor, each comprising a crankcase heater. The controller determines that one of the sensors has failed, and in response, initiates the first and second crankcase heaters and transmits an alert indicating that one of the sensors has failed. Further, the controller may disable threshold logic such that the first and second compressors are controlled independently of a determination whether the tandem compressor is operating outside of a threshold range. The controller operates the first and second compressors according to a safe mode, wherein first on or off settings of the compressors are determined based on a first required load operation of the tandem compressor. The first required load operation is determined from a first temperature demand of a structure associated with the HVAC system.

A refrigeration device includes a radiator, an evaporator, a compressor, a heater and a control device. The radiator causes a refrigerant to radiate heat. The evaporator causes the refrigerant to evaporate. The compressor compresses the refrigerant circulating between the radiator and the evaporator. The heater heats lubricating oil in the compressor. The control device controls the heater so that an oil temperature of the lubricating oil in the compressor reaches an oil temperature target value obtained by adding a predetermined temperature to saturation temperature of the refrigerant in the compressor.