Abstract: A refrigerant system has an electric motor positioned either inside or outside of a hermetically sealed shell containing a compressor pump unit and is mechanically coupled to drive this compressor pump unit. The electric motor has at least one thermoelectric cooler to cool, or assist in cooling, of at least one component of the electric motor.

Abstract: A service valve for isolating the compressor of a chiller system from a flooded evaporator cooler that includes a suction pipe mounted in the top section of the evaporator that extends downwardly into the evaporator shell and a shut-off valve mounted inside the shell that is arranged to close against the bottom opening of the suction pipe. The valve is connected by linkage to a shaft that passes through the suction pipe outside the evaporator which when rotated, permits the valve to be opened and closed.

Abstract: The present invention is a method for operating an air conditioner chiller system under high ambient air conditions. When the temperature of the standard discharge saturation temperature increases above a first predetermined temperature as a result of a rise in ambient air temperature, an expansion valve is throttled to reduce the capacity of the system compressor. The amount of throttling can be made to be dependent on the amount that the discharge temperature exceeds the first predetermined temperature so that compressor capacity is reduced by an amount no more than is necessary to assure that a maximum operating design pressure is not exceeded.

Abstract: An improved cooler with level sensor for measuring variation in the liquid refrigerant level of a refrigerant within the cooler, comprises a cooler shell for holding the refrigerant, heat exchanger tubes for carrying the liquid to be cooled, and a liquid refrigerant level sensor comprising a probe extending to a point above the heat exchanger tubes, one or more thermistors; and a heating element. When the probe is totally within the vapor refrigerant above the heat exchanger tubes, the heater raises the temperature of the thermistors above the saturation temperature of the refrigerant. As the liquid refrigerant level begins to rise, the liquid refrigerant comes in contact with the outside of the probe. Since the heat transfer coefficient of the liquid refrigerant is significantly higher than that of the vapor refrigerant, the probe in that area is quickly cooled to the saturation temperature.

Abstract: An oil separator for a refrigeration system having two inlets for receiving two streams of a mixture of oil and refrigerant for separation. One inlet is on each side of the oil separator. This allows for a separator with a smaller diameter to be used to achieve the same preferred speed of travel of the oil-refrigerant mixture.

Abstract: The present invention is a method for controlling oil lubricant pressure of a screw type compressor in an air conditioning system. In response to a low oil pressure condition, evaporator pressure is lowered to increase the pressure differential across a compressor, to thereby bring about an increase in oil pressure. Evaporator pressure can be lowered by decreasing the maximum operating pressure of the evaporator, and by throttling an expansion valve by the amount required to lower the evaporator pressure in accordance with the reduced maximum operating setpoint.

Abstract: An oil separator for a refrigeration system having a screw compressor for pressurizing and circulating refrigerant through the system, an evaporator, a condenser and an oil separator. The oil separator is placed within the housing of the condenser.

Abstract: A flash tank economizer containing a first expansion device to expand high pressure refrigerant from a system condenser to an intermediate pressure and a second expansion device for further expanding liquid refrigerant at the intermediate pressure that has collected in the tank to a desired low pressure for delivery to the system evaporator. Vapor phase refrigerant produced by the first expansion in the tank is injected back into the system compressor at the intermediate pressure.

Abstract: A method and control system are disclosed for operating a refrigeration system to protect an evaporator in a refrigeration system against freezeups of a heat transfer fluid cooled in the evaporator by operation of the refrigeration system. A first signal indicative of the temperature of the heat transfer fluid in the evaporator and a second signal indicative of the temperature of the heat transfer fluid leaving the evaporator are provided to a microcomputer system which processes the first and second signals to determine when the temperature of the heat transfer fluid in the evaporator falls below the temperature of the heat transfer fluid leaving the evaporator by a selected amount. The microcomputer system generates an alarm signal to shut down operation of the refrigeration system if the microcomputer system determines that the temperature of the heat transfer fluid in the evaporator is less than the temperature of the heat transfer fluid leaving the evaporator by the selected amount.

Abstract: A method and control system are disclosed for operating a refrigeration system to protect the refrigeration system compressor from flooding at startup of the refrigeration system. When the refrigeration system is to be shut down, refrigerant flow from a condenser to an evaporator of the refrigeration system is effectively closed off and the refrigeration system compressor is run for a first preselected time period sufficient to reduce the refrigerant pressure in the evaporator to a first desired, relatively low level. Then, prior to restarting the refrigeration system, the compressor is again run with the refrigerant flow from the condenser to the evaporator closed off to pump refrigerant out of the evaporator to reduce the refrigerant pressure in the evaporator to a second desired, relatively low level.This dual pump down cycle ensures that no liquid refrigerant from the evaporator will enter the compressor when the refrigeration system is restarted.

Abstract: Programmable headers with fixed jumpers are used at the input of a microprocessor to develop a binary code for use by the microprocessor to configure the microprocessor to the physical characteristics of an assembled refrigeration unit. The programmable header is programmed at the factory by selectively breaking the jumpers to develop the binary code. The programming of the microprocessor for accessory equipment can be performed by field service personnel by using small DIP switches to develop a binary code for the microprocessor.

Abstract: A field test circuit for an electronic control of a refrigeration unit. The test circuit has a field installed test panel with a control switch and a readout device for indicating that portion of the electronic control to be tested. A microprocessor is provided with a logic program that provides coded information regarding the stage of capacity of the refrigeration unit, the operational status of the unit, diagnostic information of the unit, and a test procedure for testing all inputs and outputs of the microprocessor.

Abstract: A method and control system are disclosed for operating a refrigeration system to protect the refrigeration system compressor from adverse operating conditions. A first signal indicative of the saturation temperature of the refrigerant in an evaporator of the refrigeration system, and a second signal indicative of the temperature of gaseous refrigerant flowing from the evaporator to the compressor of the refrigeration system compressor, are provided to a microcomputer system which processes the first and second signals to determine the superheat of the gaseous refrigerant flowing to the compressor. The microcomputer system generates an alarm signal to shut down operation of the refrigeration system if the detected superheat is less than a lower limit or greater than an upper limit of a normal range of superheat values.

Abstract: A refrigeration system is disclosed which may have multiple compression and condenser stages, in which an electronic refrigerant expansion valve is controlled by the digital output of a microcomputer which adjust the expansion valve in response to a valve change signal which is a function of a fraction of the deviation of the sensed refrigerant superheat from a desired superheat added to a multiple of the computed rate of change of the refrigerant superheat.

Abstract: An incrementally adjustable electronic expansion valve for precisely controlling refrigerant flow through the valve is disclosed. Basically, the expansion valve includes a stepper motor, a sleeve member, and an orifice assembly. The sleeve member is incrementally moved over a slot(s) in the orifice assembly by operation of the stepper motor to control refrigerant flow between an inlet and an outlet of an expansion valve. A control system provides electronic digital control signals to the stepper motor to control operation of the motor in response to superheat of refrigerant flowing from an evaporator to a compressor of the refrigeration system. The electronic expansion valve may also include sealing means to substantially prevent refrigerant flow through the valve when the sleeve member is in its fully closed position.

Abstract: A method and control system for operating a refrigeration unit to permit random loading and unloading sequences of multiple compressors and unloaders. The random loading and unloading sequences of the two circuits of compressors and unloaders is performed by a microprocessor. A random sequence is selected at start-up and the selected sequence loads the compressors to full load, where upon another random sequence is selected to unload the compressors.The compressors are also loaded in response to the water temperature leaving the chiller. The leaving water temperature is compensated for by a return water temperature which determines the temperature drop through the heat exchanger. The temperature drop is divided by the number of active stages to determine the drop/stage, which is an indication of how the leaving water temperature will change when a capacity stage is either added or subtracted.

Abstract: Apparatus for and a method of operating a high performance shell and tube type heat exchanger utilizing tubes having integral internal fins. A specific tube circuit configuration is selected to limit the temperature drop of the refrigerant within the tube to a preselected range as the refrigerant flows through the circuit.