Abstract: A heating ventilation and air conditioning (HVAC) system includes a plurality of heating, ventilation and air conditioning (HVAC) units servicing a plurality of zones of a building. A plurality of controllers is connected to the plurality of HVAC units, each controller servicing one or more zones of the plurality of zones. The plurality of controllers include at least one first controller servicing at least one first zone that is powered off when the HVAC system is in a first operating mode and a second controller servicing a second zone of the plurality of zones that remains powered on when the HVAC system is in the first operating mode. The at least one second controller is operably connected to the at least one first controller to enable powering on of the first controller when an environmental condition in the second zone falls outside of a selected range.

Abstract: An air conditioning system having a cooling mode and a free-cooling mode is provided. The system includes a refrigeration circuit, two pressure sensors, a controller, and a pump-protection sequence resident on the controller. The refrigeration circuit includes a compressor and a pump. The first pressure sensor is at an inlet of the pump, while the second pressure sensor is at an outlet of the pump. The controller selectively operates in the cooling mode by circulating and compressing a refrigerant through the refrigeration circuit via the compressor or operates in the free-cooling mode by circulating the refrigerant through the refrigeration circuit via the pump: The pump-protection sequence turns the pump to an off state based at least upon a differential pressure determined by the controller from pressures detected by the first and second pressure sensors.

Abstract: An air conditioning system having a cooling mode and a free-cooling mode. The system having a refrigeration circuit having a compressor and a pump; a suction pressure sensor for measuring a suction pressure of the compressor; a discharge pressure sensor for measuring a discharge pressure of the compressor; a controller for selectively operating in the cooling mode by circulating and compressing a refrigerant through the refrigeration circuit via the compressor or operating in the free-cooling mode by circulating the refrigerant through the refrigeration circuit via the pump; and a recover-refrigerant sequence resident on the controller, the recover-refrigerant sequence being configured to pump the refrigerant in a portion of the refrigeration circuit not used in the free-cooling mode to remaining portions of the refrigeration circuit used in the free-cooling mode when the controller switches from the cooling mode to the free-cooling mode.

Abstract: An air conditioning system having a cooling mode and a free-cooling mode. The system having a refrigeration circuit having a compressor and a pump; a suction pressure sensor for measuring a suction pressure of the compressor; a discharge pressure sensor for measuring a discharge pressure of the compressor; a controller for selectively operating in the cooling mode by circulating and compressing a refrigerant through the refrigeration circuit via the compressor or operating in the free-cooling mode by circulating the refrigerant through the refrigeration circuit via the pump; and a recover-refrigerant sequence resident on the controller, the recover-refrigerant sequence being configured to pump the refrigerant in a portion of the refrigeration circuit not used in the free-cooling mode to remaining portions of the refrigeration circuit used in the free-cooling mode when the controller switches from the cooling mode to the free-cooling mode.

Abstract: A method of controlling an air conditioning system having a cooling mode and a free-cooling mode, including activating the air conditioning system; measuring a first temperature of ambient air surrounding a condenser, measuring a second temperature of the working fluid; calculating a difference between the first and second temperatures; and comparing the difference to a predetermined value, wherein if the difference is greater than or equal to the predetermined value the free-cooling mode is activated, and wherein if the difference is less than the predetermined value the cooling mode is activated.

Abstract: An air conditioning system having a cooling mode and a free-cooling mode is provided. The system includes a refrigeration circuit, two pressure sensors, a controller, and a pump-protection sequence resident on the controller. The refrigeration circuit includes a compressor and a pump. The first pressure sensor is at an inlet of the pump, while the second pressure sensor is at an outlet of the pump. The controller selectively operates in the cooling mode by circulating and compressing a refrigerant through the refrigeration circuit via the compressor or operates in the free-cooling mode by circulating the refrigerant through the refrigeration circuit via the pump: The pump-protection sequence turns the pump to an off state based at least upon a differential pressure determined by the controller from pressures detected by the first and second pressure sensors.

Abstract: A method of controlling an air conditioning system having a cooling mode and a free-cooling mode, including activating the air conditioning system; measuring a first temperature of ambient air surrounding a condenser; measuring a second temperature of the working fluid; calculating a difference between the first and second temperatures; and comparing the difference to a predetermined value, wherein if the difference is greater than or equal to the predetermined value the free-cooling mode is activated, and wherein if the difference is less than the predetermined value the cooling mode is activated.

Abstract: An air conditioning system having a cooling mode and a free-cooling mode is provided. The system includes a refrigeration circuit, two pressure sensors, a controller, and a pump starting sequence resident on the controller. The refrigeration circuit includes a compressor and a pump. The first pressure sensor is at an inlet of the pump, while the second pressure sensor is at an outlet of the pump. The controller selectively operates in the cooling mode by circulating and compressing a refrigerant through the refrigeration circuit via the compressor or operates in the free-cooling mode by circulating the refrigerant through the refrigeration circuit via the pump. The pump starting sequence cycles the pump between an on state and an off state based at least upon a differential pressure determined by the controller from pressures detected by the pressure sensors.

Abstract: Refrigerant is circulated through a vapor compression system including a compressor, a gas cooler, an expansion device, and an evaporator. When a sensor detects that frozen water droplets form on the evaporator, a valve positioned between the discharge of the compression and inlet of expansion device is opened. Refrigerant from the discharge of the compressor bypasses the gas cooler and enters the inlet of the expansion device. The high temperature refrigerant melts the frost on the evaporator. As the frost melts, the passage of the evaporator is opened to allow air to flow through the evaporator.

Abstract: Refrigerant is circulated through a vapor compression system including a compressor, a gas cooler, an expansion device, and an evaporator. When a sensor detects that frozen water droplets form on the evaporator, a valve positioned between the discharge of the compression and inlet of expansion device is opened. Refrigerant from the discharge of the compressor bypasses the gas cooler and enters the inlet of the expansion device. The high temperature refrigerant melts the frost on the evaporator. As the frost melts, the passage of the evaporator is opened to allow air to flow through the evaporator.