A container including a housing defining a product space and including a refrigeration system. The refrigeration system is coupled to the container and is in communication with the product space to condition the product space. The refrigeration system is operably connected to each other and selectively conditions the product space in a low temperature mode and a medium temperature mode.

For more efficient operation of an air cooled chiller, a refrigerant pump and bypass valve connected in parallel feed refrigerant from the condenser to a receiver. The pump is activated in response to pressure in the condenser; the bypass is used otherwise. Further efficiency is provided by controlling the condenser fan based on power consumption by the air cooled chiller and/or resetting a set point of the evaporator to meet load conditions. An expansion valve for the evaporator is controlled based on chilled water temperature, such as Delta T, or information from an air handling unit. Feedback of valve setting or position, air temperature, valve size, and/or importance of an air handling unit may be used to control the flow of chilled water. In addition to or an alternative to control of the chilled water flow, the refrigerant temperature may be controlled based on information from the air handling unit.

A refrigeration system includes a compressor having a first stage and a second stage; a heat rejecting heat exchanger including an inter-cooler and a gas cooler, the intercooler coupled to an outlet of the first stage and the gas cooler coupled to an outlet of the second stage; an unload valve coupled to an outlet of the intercooler and a suction port of the first stage; a flash tank coupled to an outlet of the gas cooler; a primary expansion device coupled to an outlet of the flash tank; a heat absorbing heat exchanger coupled to an outlet of the primary expansion device, an outlet of the heat absorbing heat exchanger coupled to the suction port of the first stage; and a controller for executing a startup process including controlling the unload valve to direct refrigerant from the intercooler to the suction port of the first stage.

A method of controlling a heating, ventilation and air-conditioning (HVAC) system includes measuring an ambient temperature and determining whether the ambient temperature is below a threshold temperature value. Responsive to a determination that the ambient temperature is below the threshold temperature value, measuring a condenser-fan cycle time of the HVAC system and setting a speed of the compressor based on the measured condenser-fan cycle time.

A refrigeration system includes a free cooling system having an air-cooled heat exchanger, where the air-cooled heat exchanger includes a fan configured to move air over coils of the air-cooled heat exchanger to remove heat from a coolant flowing through the air-cooled heat exchanger, and a mechanical cooling system with a refrigerant loop that includes an evaporator, a compressor, and a condenser disposed along the refrigerant loop, where the compressor is configured to circulate a refrigerant through the refrigerant loop, and wherein the evaporator is configured to receive the coolant and transfer heat from the coolant to the refrigerant. The refrigeration system also includes a controller configured to adjust a fan speed of the fan up to a threshold fan speed, to initiate operation of the compressor when the fan speed reaches the threshold fan speed, wherein the fan speed and a compressor speed of the compressor are based at least on an ambient air temperature and a cooling load demand.

A heat-exchange ventilation device includes: a heater connection terminal to which an external connection heater is connected; a temperature sensor that measures a temperature of a supply air flow passing through an air supply passage; and a control unit that controls operations of an air supply fan and an air exhaust fan and turning-on and turning-off of the external connection heater based on a measurement result of the temperature sensor. The external connection heater is installed in an outdoor air-supply duct and heats a supply air flow flowing through the air supply passage into a heat exchanger. The air supply fan is operable at a plurality of intensities, and the control unit prohibits a state in which the air supply fan is operated at an intensity lower than an intensity set in advance and the external connection heater is turned on.

An ice maker control system includes a low side pressure transducer on a suction line and a high side pressure transducer on a discharge line. The ice maker's refrigeration system is hermetically sealed and devoid of pressure taps for servicing gauges. The ice maker can display an indication of real-time suction or discharge pressure. The ice maker can store records of suction and discharge pressure over time and display time series data for suction and discharge pressure on the display. The ice maker can cycle the condenser fan based on the discharge pressure. An additional high pressure switch can shut off the compressor independently of the controller or transducers. During a pulldown routine, the ice maker refrains from delivering water to the ice formation device until the suction pressure is below a threshold.

Air conditioner units and methods for operating air conditioner units are provided. A method includes determining an operational state of each heater bank of a plurality of heater banks of the air conditioner unit, and determining a speed of a blower fan of the air conditioner unit when the operational state of every heater bank is active. The method further includes comparing a blower fan motor rotational frequency to a rotational frequency threshold value when the speed is a low speed, and deactivating one of the plurality of heater banks when the blower fan motor rotational frequency is greater than the rotational frequency threshold value.

Systems, apparatus and methods for operating a chiller plant while minimizing or eliminating the occurrence of centrifugal compressor surge. Taking into account chiller design specifications and current operating conditions, a compressor lift point at which surge is predicted to occur is established. Minima and maxima for various chiller setpoints that avoid or eliminate the occurrence of compressor surge are imposed on setpoints provided by a conventional optimizing chiller controller. The chiller system is operated in accordance with the resultant anti-surge setpoints. Coolant tower flow is modulated to enable the compressor to operate at near-surge conditions while preventing the onset of actual surge.

The present invention provides for a control system for operating a heating, ventilation, and air conditioning (HVAC) system. A controller operates compressors in tandem. In response to detection of a high pressure condition in refrigerant flowing through a high pressure side of the HVAC system, the controller operates the HVAC system with a first compressor on and a second compressor off.