Abstract: Methods and systems consistent with this invention control a hot gas bypass valve in a refrigeration system including a centrifugal compressor, a condenser, an evaporator, and a hot gas bypass line between the compressor and the evaporator. Such methods and systems continuously sense for a surge condition during operation of the refrigeration system, indicate a surge condition when the refrigeration system is operating under surge conditions, and open at least partially the hot gas bypass valve in response to the sensed surge condition to return the refrigeration system to operating under non-surge conditions. Methods and systems consistent with this invention also sense a present head parameter representative of the present head of the compressor, sense a present load parameter representative of the present load, and control the hot gas bypass valve so as to avoid surging in the compressor in response to the present head parameter, the present load parameter, and stored head and load parameters.

Abstract: Methods and systems consistent with this invention control a hot gas bypass valve in a refrigeration system including a centrifugal compressor, a condenser, an evaporator, and a hot gas bypass line between the compressor and the evaporator. Such methods and systems continuously sense for a surge condition during operation of the refrigeration system, indicate a surge condition when the refrigeration system is operating under surge conditions, and open at least partially the hot gas bypass valve in response to the sensed surge condition to return the refrigeration system to operating under non-surge conditions. Methods and systems consistent with this invention also sense a present head parameter representative of the present head of the compressor, sense a present load parameter representative of the present load, and control the hot gas bypass valve so as to avoid surging in the compressor in response to the present head parameter, the present load parameter, and stored head and load parameters.

Abstract: Methods and systems consistent with this invention control a hot gas bypass valve in a refrigeration system including a centrifugal compressor, a condenser, an evaporator, and a hot gas bypass line between the compressor and the evaporator. Such methods and systems continuously sense for a surge condition during operation of the refrigeration system, indicate a surge condition when the refrigeration system is operating under surge conditions, and open at least partially the hot gas bypass valve in response to the sensed surge condition to return the refrigeration system to operating under non-surge conditions. Methods and systems consistent with this invention also sense a present head parameter representative of the present head of the compressor, sense a present load parameter representative of the present load, and control the hot gas bypass valve so as to avoid surging in the compressor in response to the present head parameter, the present load parameter, and stored head and load parameters.

Abstract: An adaptive control apparatus and a method for automatically controlling a refrigeration system as a function of cooling load and head. A control panel controls the operation of a hot gas bypass valve so as to avoid surging of the compressor in response to cooling load and head. The control apparatus and method also allow for automatic self calibration.

Abstract: When sensors are employed to monitor the evaporator refrigerant pressure and the leaving chilled liquid temperature in an air conditioning system of the type having a liquid chiller, the sensor outputs will normally have a prescribed relationship with respect to each other as long as the sensors are functioning properly and regardless of the operating condition of the air conditioning system. By effectively comparing the output of one sensor relative to that of the other sensor, a faulty condition of either sensor may be detected. This is achieved by calculating the equivalent evaporator temperature, from the evaporator refrigerant pressure, and subtracting the equivalent temperature from the leaving chilled liquid temperature to obtain a difference temperature which is then compared to a predetermined known temperature range representing normal functioning of the two sensors. When one of the sensors is defective the difference temperature will fall outside of the range.

Abstract: When sensors are employed to monitor different operating variables or parameters in a refrigeration system, the sensor outputs will normally have predetermined known relationships with respect to each other as long as the sensors are functioning properly and regardless of the operating condition of the refrigeration system. By comparing the output of one sensor relative to that of another sensor, a faulty condition of either of those two sensors may be detected. For example, during stabilized system operation the output of a condenser pressure sensor should always indicate a higher pressure than that reflected by the output of an evaporator pressure sensor. By effectively subtracting the evaporator pressure from the condenser pressure, a faulty sensor may be discovered. If the result of the subtraction is zero or negative, at least one of the pressure sensors is defective. When a faulty sensor is detected, a warning message is displayed to operating personnel.

Abstract: To conserve energy in a large capacity refrigeration or air conditioning system, where liquid (usually water) is chilled by the system's evaporator and is then used to cool a building, the temperature setpoint of the chilled liquid leaving the evaporator may be reset upward from its desired level. Normally, if the temperature of the leaving chilled liquid falls below the setpoint by a fixed differential (such as 4.degree. F.) to a cut-out temperature, the system's compressor is shut down as a safety precaution to prevent freeze-ups. A nuisance compressor shutdown may be avoided when the setpoint is reset to a higher level (since the actual temperature of the leaving chilled liquid at that time may be at or below the desired setpoint and may be more than 4.degree. below the reset setpoint) by lowering the cut-out temperature to a fixed level substantially below the desired setpoint, such as down to 36.degree. F.

Abstract: An improved condenser including a longitudinal extending baffle and a series of transversely extending baffle plates creating a desired flow path for vapor to be cooled which is introduced into a shell. The condenser is characterized by high efficiency performance resulting from improved heat transfer coefficients and better purging of non-condensable gases because of the novel baffle arrangement.

Abstract: A control system and a method are disclosed for automatically controlling a hot gas bypass valve as a function for cooling load and head. A valve/controller is provided for controlling the operation of the hot gas bypass valve so as to avoid surging of the compressor in response to temperatures of the chilled liquid entering the evaporator, the chilled liquid leaving the evaporator, and the liquid refrigerant at the outlet of the condenser.