A vapor compression system includes a compressor, a first heat exchanger, an expansion valve and a second heat exchanger arranged serial refrigerant flow path; a first fan configured to direct air over the first heat exchanger; a controller coupled to the first fan and the compressor, the controller configured to: set a compressor discharge superheat limit; determine a compressor discharge superheat; compare the compressor discharge superheat to the compressor discharge superheat limit; and when the compressor discharge superheat is less than the compressor discharge superheat limit, the controller reducing at least one of a compressor speed and a first fan speed.

A method including: determining a cooling value; and comparing the cooling value to an activation point of a lead compressor. The lead compressor is in a tandem set of scroll compressors of a cooling system. The tandem set of compressors comprises a lag compressor. The method further includes: activating the lead compressor when the cooling value is greater than the activation point; activating the lag compressor subsequent to activating the lead compressor; and determining whether conditions exist including: an alarm associated with the lag compressor being generated, and the lead compressor being deactivated. The method further includes deactivating the lag compressor when at least one of the conditions exists in the cooling system.

In one aspect, a fan array fault response control system is provided for a cooling tower. The fan array fault response control system includes a fan interface configured to be in communication with a plurality of fans of the cooling tower and a processor operably coupled to the fan interface. The processor is configured to detect at least one non-operational fan of the plurality of fans. The processor configured to effect, in response to detecting the at least one non-operational fan, a reduced fan speed of at least one operational fan of the plurality of fans.

A two-stage cascade refrigeration system is provided having a first refrigeration stage and a second refrigeration stage. The first refrigeration stage defines a first fluid circuit for circulating a first refrigerant, and has a first compressor, a condenser, and a first expansion device. The second refrigeration stage defines a second fluid circuit for circulating a second refrigerant, with the second refrigeration stage having a second compressor that is a variable speed compressor, a second expansion device, and an evaporator. A heat exchanger is in fluid communication with the first and second fluid circuits to exchange heat between the first and second refrigerants. A controller stages operation of the first and second compressors and runs the second compressor at an initial speed less than a maximum speed initially when a staging protocol is performed during start up or re-starting of the refrigeration system.

Provided is a cooling system wherein a first two-phase refrigerant can be circulated by a pump through an evaporator, to a first condenser, to a refrigerant-to-refrigerant heat exchanger and back to the pump. By providing the refrigerant-to-refrigerant heat exchanger in series with the condenser, a first environment can be cooled without having to operate a vapor compression circuit when an ambient temperature outside the first environment is a predetermined amount below an ambient temperature in the first environment.

A refrigeration cycle apparatus includes a compressor, a condenser, a first subcooling device that subcools a refrigerant by exchanging heat with the air, a second subcooling device that performs a heat exchange between refrigerant streams that have been branched by a branch pipe, thereby subcooling one of the refrigerant streams, a flow control device that adjusts a flow rate of the second stream of the refrigerant and passes this refrigerant through the second subcooling device, a bypass path that allows the refrigerant passing through the flow control device and the second subcooling device to flow therethrough, an expansion valve, an evaporator, and a controller configured to control an amount of heat exchanged in the first subcooling device and an amount of heat exchanged in the second subcooling device based on a temperature of the air.

A drive circuit is provided and includes a rectification circuit, a buck converter, a first inverter, and a second inverter. The rectification circuit is configured to rectify a first AC voltage signal to generate a rectified voltage signal. The buck converter is configured to downconvert the rectified voltage signal to a DC voltage signal, wherein the DC voltage signal is supplied to a DC bus. The first inverter is configured to convert the DC voltage signal to a second AC voltage signal and supply the second AC voltage signal to a compressor motor. The second inverter is configured to convert the DC voltage signal to a third AC voltage signal and supply the third AC voltage signal to a condenser fan motor. Peak voltages of the second AC voltage signal and the third AC voltage signal are less than peak voltages of the first AC voltage signal.

A method for a refrigeration system includes receiving a temperature difference (TD) setpoint indicating a desired temperature difference between outside air and refrigerant and modifying the TD setpoint based on conditions currently being experienced by the refrigeration system. The modified TD setpoint is selected to cause a decrease in total power consumption, wherein the total power consumption comprises power consumed by a compressor to yield a discharge pressure and power consumed by a condenser fan to operate a fan speed.

A refrigeration system includes a supplemental heat exchanger operably disposed between a condenser and an evaporator. This supplemental heat exchanger is located in selective fluid communication with the air in the conditioned space, and can be toggled between an “invisible” mode in which the heat exchanger acts as a simple fluid conduit between the condenser and evaporator, and a “humidity reduction” mode in which the heat exchanger operates to transfer heat from hot refrigerant to the colder conditioned space. This addition of heat into the conditioned space decreases the relative humidity of the conditioned space and subcools the refrigerant leading to the expansion valve and evaporator. This subcooling of the liquid enables the evaporator to operate at a lower temperature which enhances the moisture removal from the air moving through the evaporator. The supplemental heat exchanger may be located in a physically elevated position relative to the remainder of the conditioned space to utilize stratification of hot air to create a default “invisible mode” without inducing airflow.

A motor drive control device includes a three-phase rectifier; a boosting circuit including a reactor, a switching element, and a backflow preventing element and boosts a direct-current bus voltage supplied from the three-phase rectifier; a smoothing capacitor; an inverter circuit; a boosting control unit; an inverter control unit; and a circuit protecting unit suppresses a ripple current flowing through the smoothing capacitor. In the circuit protecting unit, a correlation of an on-duty ratio of the switching element included in the boosting circuit, the output power of the inverter circuit, and an estimated ripple current are set. On the basis of the on-duty ratio of the switching element, output power of the inverter circuit, and the correlation, the circuit protecting unit determines an estimated ripple current flowing through the smoothing capacitor. When the estimated ripple current exceeds a preset threshold, the circuit protecting unit suppresses the ripple current.