Abstract: A frequency control apparatus of a multi-refrigeration cycle is provided with a current sensor to detect a primary current for a motor or a pressure sensor to detect a pressure at the discharge side of a compressor to detect a load in the refrigeration cycle. When a value detected by the sensor is estimated as being lower than a predetermined value range, the frequency of a current to be supplied to the motor is increased, and when the value detect by the sensor is estimated as being higher than the predetermined value range, the frequency is decreased, whereby the rising time of the refrigeration cycle can be shortened. Further, the frequency is determined by a weighted error average value of the difference between target room temperature in the rooms and detected temperature in the rooms to thereby control the multi-refrigeration cycle to provide an appropriate performance.

Abstract: A cooling device comprising a variable displacement type compressor, a condenser, an expansion valve and an evaporator. The displacement of the compressor is controlled in response to both the actual evaporation temperature of refrigerant and the actual condensing temperature of the refrigerant, so that the actual evaporation temperature approaches a predetermined desired evaporation temperature which is reduced as the actual condensing temperature is increased.

Abstract: A sliding-vane rotary compressor includes a first control valve responsive to the pressure in a low pressure chamber for adjusting the rate of communication between a high pressure side and a low pressure side, and a second control valve operative in the same manner as the first control valve under the control of an external signal. With this construction, an optimum displacement control of the compressor is achieved. Also disclosed is an apparatus for controlling a variable displacement compressor, in which a solenoid valve is controlled depending on internal and external thermal load conditions of the compressor for selectively blocking fluid communication between high and low pressure sides.

Abstract: An automobile air conditioner system includes a variable displacement compressor having a wobble plate and a pressure control valve disposed in the compressor for controlling the pressure in a crank chamber. The pressure control valve is operative under the control of predetermined conditions, such as the temperature of an evaporator.

Abstract: A low-temperature showcase comprises a heat insulated wall, on the top of which an opening for putting-into or taking-out commodities is formed. The inside of the heat insulated wall is divided into an air passage and a storage chamber thereover by a dividing plate which is installed inside this heat insulated wall in a nearly horizontal fashion. The air passage is formed in a manner that the cross-section thereof is of a U-shape, and the storage chamber is formed surrounded by this air passage. At both ends of the air passage, vent ports are formed at the positions facing each other through the opening of the heat insulated wall inbetween. The air passage is divided into two parts by a fan case corresponding to the respective vent ports and a blast fan which can rotate reversibly is supported by this fan case. In each halved air passage, an evaporator is installed in the vicinity of the vent port, and when one of the evaporators is put in cooling operation, the other evaporator is subjected to defrosting.

Abstract: A refrigerating apparatus executing the redistributing operation of refrigerant when the actual suction pressure of a compressor is lower than a suction pressure lower limit value. The suction pressure lower limit value is varied in response to the condensation temperature of refrigerant which varies in accordance with the actual temperature in the vicinity of a condenser. When the condensation temperature of refrigerant is greater than a predetermined comparison value, a first limit value is selected as the suction pressure lower limit value. Otherwise, a second limit value less than the first limit value is selected. The refrigerating apparatus may be controlled in accordance with the selected suction pressure lower limit value.

Abstract: A control device for a variable capacity compressor in an automotive air conditioning system includes a first temperature sensor disposed forward of the evaporator, a second temperature sensor disposed behind the evaporator and a third temperature sensor disposed at the outside of the automobile compartment. The control device compares the air temperatures detected by the sensors with predetermined temperatures, and controls the capacity of the compressor in accordance with the compared results.

Abstract: A low refrigerant charge detecting device comprises a refrigerant superheat temperature transducer that senses refrigerant leaving the evaporator and provides a positional output indicative of the superheat temperature of the sensed refrigerant, an ambient air temperature transducer that senses ambient air and provides a positional output indicative of the ambient air temperature, and a low charge signal effecter that responds to both the positional outputs and provides a low charge signal at predetermined refrigerant superheat and ambient air temperatures.

Abstract: A device for freezing foodstuffs on a tray cart includes a liquid cryogenic refrigerant spraying system for each side of the cart. The spraying systems are activated by reversible magnet valves. Rotary fans circulate the vaporized refrigerant. The fans are reversibly rotated for drawing in or blowing out the vaporized refrigerant across the cart shelves.

Abstract: In a refrigeration cycle in which a capacity-variable compressor a condenser, an expansion mechanism and an evaporator are connected in the order named, a device for controlling the capacity in the refrigeration cycle comprising a means for detecting the temperature of the compressor or the temperature of the gas discharged therefrom and a control device for limiting the maximum rotational speed of the compressor when the output from the means for detecting the temperature indicates a detected temperature lower than a predetermined level.

Abstract: A system and apparatus for controlling the operation of a vibrating compressor using a predetermined frequency corresponding to the load thereof, comprising a first sensor for detecting a temperature of pressure corresponding to the saturated vapor pressure of a refrigerant sucked by a vibrating compressor, a second sensor for detecting a temperature or pressure corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the compressor, and a control section for generating a drive power of a predetermined frequency based on the temperatures and pressures detected by the first and second sensors, and characterized in that the compressor is driven by a drive power generated by the control section.

Abstract: An air conditioner with a radiant temperature control comprises a refrigeration cycle for air-conditioning a room to be air conditioned at a desired temperature, a temperature setting section for generating set data for setting the desired temperature as a target value, a first temperature sensor section for detecting a room temperature of the room to be air-conditioned, a second temperature sensor section for detecting a radiant temperature of the room to be air-conditioned, a control section for receiving the set data from the temperature setting section and detection data from the first temperature sensor section and for generating an operation control signal to the refrigeration cycle in accordance with the difference therebetween, and a correcting section for receiving the set data from the temperature setting section and detection data from the second temperature sensor section and, when the difference therebetween deviates from a predetermined value, correcting the set data from the temperature setting

Abstract: This controller is used for controlling a centrifugal compressor along its path of minimum power consumption while avoiding a surge condition. It is especially useful in a refrigeration system having a variable speed centrifugal compressor with adjustable inlet guide vanes. In such an application, the controller opens the inlet guide vanes enough to satisfy the cooling demand and then, to minimize power consumption, reduces the speed of the compressor while further opening the vanes (compensating for the reduced speed) until either the inlet guide vanes are fully open or an impending surge condition is detected. The onset of a surge condition is detected by monitoring motor current fluctuations. When fluctuations above a predetermined amplitude occur in excess of a predetermined frequency, the controller determines that a surge is impending.

Abstract: An automotive air conditioner system including a first detector for detecting a cooling load in the front-seat space of a vehicle passenger compartment, a second detector for detecting a cooling load in the rear-seat space, a discriminator for selecting a larger one of the detected cooling loads, and a controller for controlling operation of a refrigerant compressor in accordance with the selected cooling load.

Abstract: A control system for a compressor motor used with an air conditioning unit is disclosed. A current for generating a non-rotating magnetic field is supplied to the compressor motor to preheat a compressor. A current for generating a rotating magnetic field is also supplied to the compressor motor together with the current for generating a non-rotating magnetic field to heat the compressor. The heat pump using this control system is thus capable of transmitting sufficient heat energy immediately after start of the operation of the heat pump.

Abstract: A temperature controlled switching device in which a first fluid filled temperature sensor responding to the temperature of heating or cooling means moves a first lever. A second sensor sensing the room temperature moves a second lever. The two levers being interconnected to move a snap action switch for control of the heating or cooling means.

Abstract: An apparatus for alarming abnormal coolant in a space cooling cycle, comprising a coolant passage for guiding high-pressure side liquid coolant in said space cooling cycle, a sensor disposed in said coolant passage and provided with a movable part having an operating fluid sealed therein and adapted to be operated by the difference of the pressure of said operating fluid and that of said liquid coolant, and a switch and an alarm device disposed in said coolant passage and interlocked with the movable part, and said operating fluid having higher saturated pressure than the saturated pressure of said coolant and possessing an ability to operate said switch when the extent of subcool of said coolant exceeds a prescribed level and the pressure of the coolant exceeds the pressure of said operating liquid and when the pressure of the coolant exceeds the pressure under which said operating fluid is wholly in a gasified state.

Abstract: Control method for a liquid-cooled cable installation with a hollow conductor, through which a coolant flows, as the cable conductor. The hollow space is divided in the longitudinal direction by partitions forming separate canals for the outgoing flow and the return of the coolant and in which canals the coolant is in contact with the conductor at high-voltage potential. Heat exchangers are provided at the start and the end of the cable system or at intermediate stations. The cable flow temperature (.theta..sub.Z *) of the coolant is lowered with increasing load of the cable by influencing the heat exchanger and is conversely raised with falling load in such a manner that the mean value of the coolant (.theta..sub.m) remains constant.

Abstract: A space conditioning closed loop refrigeration system, particularly a vehicle air conditioning system utilizing a positive displacement compressor having a slide valve for varying the capacity and shiftable between full load and full unload positions and vice versa and driven therebetween by a linear fluid motor having a movable member coupled to the slide valve and forming a first chamber which is normally dumped via a slide valve modulator to compressor suction pressure and a second chamber open to compressor discharge pressure. A restricted passage between chambers tends to cause the first chamber to reach compressor discharge pressure absent that chamber dumping to suction.

Abstract: A membrane innerly divides a body in two rooms, one of which is subjected to a first pressure of the ratio of pressures which is to be compared to a threshold. In the other room, there is a gas in pressure equilibrium with its condensate; this gas is in thermal contact with another gas which is also in pressure equilibrium with its condensate and which is subjected to the second pressure of the pressure ratio. The forces on the membrane balance each other when the ratio equals the threshold. The threshold is equal to the ratio between the pressure of the two gases in equilibrium with their condensate. This threshold is substantially stable when the temperature varies. The membrane is connected to control means.

Abstract: Presented is a control device which may be added to an already existing air conditioning refrigeration system, or which may be built into the air conditioning refrigeration system at the factory and which monitors the temperature and pressure of a refrigerant flowing in the refrigeration system to determine increases or decreases in the ratio of pressure change to temperature change above or below a predetermined and desirable super-heat temperature for the particular system involved. The increase or decrease of this super-heat beyond predetermined upper and lower limits sustained for a predetermined interval, initiates deactivation of the refrigeration system so as to prevent damage thereto.

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 capacity control system for a refrigeration system including a compressor, a condensor, and an evaporator, all connected in a closed refrigeration circuit is provided. The compressor includes a plurality of adjustable inlet guide vanes, a motor connected to regulate the inlet guide vanes position, and an electrical speed motor connected to drive the compressor. The capacity control system includes a microprocessor responsive to continual measurements of a PRV signal, a compressor head signal and a suction flow signal for calculating a current operating point. The microprocessor determines whether the operating point is sufficiently away from a surge surface. The microprocessor will cause the operating point to move to a new operating point of a lower compressor speed and a more open PRV position if the operating point is sufficiently away from surge.

Abstract: A microprocessor based control for tempering supply air in a multi-stage temperature conditioning system. The temperature conditioning stages are normally controlled in response to a comfort temperature sensor to maintain the zone at a setpoint. However, if a sensor in the supply airstream indicates that the temperature of the supply air is less than a predetermined minimum, the primary control algorithm is overridden and the temperature conditioning stages are controlled to increase the supply air temperature. Tempering the supply air prevents personal discomfort due to excessively cold air being supplied to the zone.

Abstract: An improved cooling system includes a vapor compression refrigeration loop made up of a compressor, an expansion valve, an evaporator and a condenser. A cool air fan blows air past the cool surfaces of the evaporator. The cooled air is directed to the interior of the structure by a cool air duct. A thermostat actuates the cool air fan and the compressor when the temperature in the structure rises above a selected value. Recognizing that cooling systems are oversized, and thus run inefficiently during normal operation, a compressor cycling switch is used to cycle the compressor on and off during the cool demand cycles according to the air temperature in the cool air duct. This increases the efficiency of the system by reducing back pressure on the compressor and reducing icing of the system.

Abstract: A variable speed drive motor system is disclosed. The motor system is particularly suitable for use as a drive system for a centrifugal compressor in a refrigeration system. The motor system includes an AC auxiliary motor/generator with inverter control. The motor/generator is interconnected through a transmission system to a main motor to drive an output drive shaft at varying speeds. Preferably, the interconnecting transmission system is an epicyclic gear system.

Abstract: Presented is a control device which may be added to an already existing air conditioning refrigeration system, or which may be built into the air conditioning refrigeration system at the factory and which monitors the temperature and pressure of a refrigerant flowing in the refrigeration system to determine increases or decreases in the ratio of pressure change to temperature change above or below a predetermined and desirable super-heat temperature for the particular system involved. The increase or decrease of this super-heat beyond predetermined upper and lower limits deactivates the refrigeration system so as to prevent damage thereto.

Abstract: An air conditioning control system, for use with an air conditioning system having a variable-capacity compressor, varies the compressor loading in accordance with evaporator pressure at return air temperatures above an upper set point and fixes the compressor loading at 33% thereabouts when the return air temperature falls below the upper set point. If the temperature continues to fall, the compressor will be shut down at a lower set point at which the heating apparatus may be automatically and momentarily activated. The compressor will not again be activated until the temperature rises above the upper set point. The heating is deactivated as soon as the temperature rises above the lower set point.

Abstract: Method and apparatus for controlling the cooling of a hermetic type control box accommodating therein electronic apparatus by means of a cooling system. A cooling member of the cooling system is disposed at an upper portion of a hermetically closed chamber in which the electronic apparatus is housed. On the basis of measurements of intra-box temperature and extra-box temperature, control is so performed that the intra-box temperature is maintained higher than the extra-box temperature by a predetermined value when the cooling is being effected within the control box by means of the cooling system.

Abstract: A refrigeration system for a chilled-product vending machine including a refrigeration compressor, a temperature sensor for detecting the temperature within said vending machine and turning the compressor ON and OFF to define a compressor cycle in response to the detection of predetermined temperature limits, an evaporator coil and evaporator fan means for blowing air across said evaporator coil and circulating said air throughout the vending machine.

Abstract: A control device is disclosed for controlling the operation of a compressor in an air conditioning or refrigerating system. The compressor includes a variable displacement device which changes the capacity of the compressor and a magnetic clutch which operates the compressor in response to an external drive mechanism. The control device controls the operation of both the variable displacement device and the magnetic clutch in response to the temperature of the cool air generated at the evaporation of the air conditioning or refrigerating system. Two temperature detectors having different thermal response characteristics detect the temperature of the cool air. The difference between the temperatures detected by these sensors is used by the control device to control the operation of the variable displacement device.

Abstract: An apparatus for controlling an air conditioner having a refrigeration cycle including an evaporator disposed in an air passage for supplying air to an area to be air-conditioned and a compressor having a mechanism for varying a volume of discharge from the compressor, comprises signal generator responsive to a humidity in the area to be air-conditioned for producing a signal indicative of the humidity; and means responsive to the signal from the signal generator for actuating the mechanism for varying the volume of discharge from the compressor.

Abstract: An air conditioner for vehicles in which the temperature of an evaporator is detected and an ON-OFF control of the compressor is achieved to maintain the evaporator temperature at a pre-set temperature. The air conditioner has means for detecting the temperature of air flowing into the evaporator, and means for varying the pre-set temperature in such a manner that the pre-set temperature is increased as the detected air temperature is decreased and is decreased as the detected air temperature is increased.

Abstract: An air conditioning system for preventing the fogging of vehicle windows includes a defroster switch which is closed to turn on a compressor when the temperature at or around the surfaces of an evaporator drops down to a predetermined off mode level. When the temperature outside the vehicle passenger compartment drops from a relatively high level to a first predetermined level, the off mode level becomes saturated to a constant (maximum) level. As the outside temperature further drops to reach a predetermined second temperature level, the off mode level is progressively lowered from the maximum level to a lower level. With this control, the compressor is turned on again after being closed by closing of the defroster switch, thereby permitting the vehicle windows to be cleared of the fogging from their inner surfaces.

Abstract: A temperature sensing means for a refrigeration apparatus including sensing means responsive to the temperature within a refrigerated space and to an ambient temperature condition for signalling the temperature condition of the refrigeration apparatus. In the disclosed embodiment, the sensing means is mounted in the access door of the refrigeration apparatus and the temperature sensors are mounted within a single housing. The sensor for sensing the ambient temperature is effectively insulated from the refrigerated space and senses the ambient temperature through a portion of the housing and door. In the illustrated embodiment, the sensing means is used to provide an ambient temperature compensated over-temperature alarm for the refrigeration apparatus.

Abstract: In a transport refrigeration system of the type adapted to provide either heating or cooling, loss of refrigerant is detected by first and second sensors 58 and 60 located upstream and downstream, respectively, of the expansion device 34, and with the downstream sensor 60 also being downstream of the location at which hot gas is injected from line 56 to pass to the refrigerant coil 40 in a heating mode of operation. The arrangement includes means for both determining the mode of system operation, either heating or cooling, and comparing the differential temperatures sensed for determining the departures from ranges of temperatures normally expected with an adequate charge of refrigerant.

Abstract: The outlet temperature of a cooler (31) is controlled within predetermined limits in accordance with the difference between a desired set temperature in an enclosure (13) and the actual temperature therein in such a manner as to minimize the time the cooler (31) is energized. Minor temperature variations in the enclosure occuring while the cooler (31) is off are compensated for by positioning an air mix door (37).

Abstract: A control system for a rotary helical screw compressor of the variable speed type includes a variable speed motor driving the compressor for varying the compressor capacity and a slide valve member which is adjusted optimally for varying the volume of gas trapped in the working chamber prior to discharge as a function of the pressure ratio across the compressor. There is also provided a control system for a rotary helical screw compressor of the fixed speed type which include a first slide valve member for varying the compressor capacity through modulating the volume of gas trapped in the working chamber prior to compression and a second slide valve member for adjusting optimally the volume of gas trapped in the working chamber prior to discharge as a function of the pressure ratio across the compressor.

Abstract: A temperature control circuit of an automobile air-conditioning system includes a temperature sensor for detecting the temperature of air blown into the room of the automobile. The signal detected by the sensor is compared at a first comparator with a voltage level corresponding to a predetermined temperature. The output of the first comparator at a time when the blown air temperature is lowered to the predetermined temperature, is delayed by a delay circuit and is applied to a second comparator. Then, the second comparator generates a signal for stopping the operation of the refrigerant compressor. The signal is also applied to a third comparator which maintain the stop signal until the signal corresponding to a higher temperature is applied thereto from the temperature sensor. Thus, the frost on the refrigerant evaporator can be defrosted before the compressor restarts.A fourth comparator is used for controlling the temperature of the room of the automobile.

Abstract: A condensation air drying apparatus comprising a refrigeration system, the evaporator of which is used for cooling an air flow to or below its dew point whereby the moisture in the air as drawn through the cooler by a fan is condensed on the cooler and drained off. A switch over valve enables the cooler to be temporarily connected as a condenser in the refrigerator system, whereby the cooler is heatable for defrosting. A temperature sensor mounted direct on the cooler serves to control the fan power for optimal economy in normal operation and to detect frost formation and control start and stop of the defrosting cycles in response to such detection. The control equipment may include an air temperature sensor adjusting the working characteristic of the cooler temperature sensor in an optimal manner according to the temperature of the air to be dried.

Abstract: The control system disclosed herein regulates a centrifugal compressor which has inlet guide vanes adjustable to vary the compressor capacity. A variable speed motor is connected to drive the compressor, and variation of this motor speed provides another input for regulating the compressor capacity. A control system achieves optimum energy efficiency, while avoiding surge, by the manner in which the motor speed and the inlet guide vane positions are regulated. To do this, a control signal must be derived to indicate the compressor head value. This signal is achieved by providing two signals, one related to the absolute condenser pressure, and the second related to the absolute evaporator pressure. The control system operates on these two signals to provide a third signal which is a function of a ratio, in which the numerator is the difference between the condenser and evaporator pressures, and the denominator is the evaporator pressure. Alternative measurement and processing techniques are described.

Abstract: An evaporator inlet water temperature control system for controlling the inlet water temperature of an evaporator utilized in an inverter driven centrifugal chiller. The system creates the proper chilled water set point at the evaporator outlet needed to maintain the inlet water at its set point for greater efficiency of operation. Control is accomplished by generating an electrical error signal which is a function of an inlet water set point voltage and the actual inlet water temperature. A logic signal is produced as a function of the error signal detected by the circuit and establishes a dead zone band representing a range in which the error signal is acceptable. Output of the control system is passed to the capacity control circuit of an inverter driven centrifugal compressor chiller.

Abstract: Modulating system for electrically or pneumatically controlled chillers in which a sensor senses the space condition, in a controlled environment or space. Output signals from an enthalpy sensor or other sensor representing the space condition are fed to chiller modulator electronic controls and thence to the chiller modulator interface controls, be they electric or pneumatic. The sensor monitors the conditions in or returning from the controlled space or environment. By measuring both humidity and temperature, the enthalpy sensor generates an effective temperature or comfort level. The input signal from the sensor is compared to an operator adjustable set-point. If the measured condition is less than the set-point, an error signal is generated which is proportional to the difference multiplied by an operator-set sensitivity control.

Abstract: The logic control system of the invention regulates the frequency of operation of an inverter which drives an electric motor, and also regulates the level of the d-c bus voltage supplied to the inverter. This is accomplished by sensing the level of the bus voltage and the level of the current supplied to the motor, and comparing the sensed values to a reference or set point signal. The motor drives a compressor, and a capacity control system cooperates with the logic control system in the regulation of the compressor. The capacity control system provides signals, such as start/stop and inverter set point, to the logic control system to assist in regulating operation of the inverter which drives the compressor. In particular the logic control system includes a reference conductor on which a basic reference control signal is developed for use in controlling both the amplitude and the frequency of the a-c energy supplied by the inverter to the motor.

Abstract: An air source heat pump system incorporating a refrigerant charged bulb within the air flow passing over the outdoor coil of the heat pump system to sense outside ambient air temperature. The refrigerant charged bulb supplies a variable saturated pressure which acts upon a bellows of a control unit whose opposite side is subjected via a second bellows to saturated suction pressure (corresponding to refrigerant evaporating temperature) of the refrigerant returning from the outdoor coil to the inlet of the compressor. The bellows provides a spring load. An electrical switching device responsive to this pressure differential acts to first block unnecessary loading of the compressor and secondly to initiate unloading of the compressor. Additional switching means prevents excessive unloading of the compressor and insures subsequent initiation of loading to prevent liquid logging of the evaporator coil.

Abstract: A system and method for controlling a refrigeration unit of an air conditioning system operating in connection with a given building environment so as to establish conditions providing a desired comfort level within the building environment, the system and method being arranged to detect the output of the refrigeration unit, to detect changes in interior or exterior conditions which will affect the comfort level in the building environment and to provide at least one control signal in response to the detected output and conditions for operating the refrigeration unit, the control signal being compensated for the predetermined dynamic characteristics of the particular refrigeration unit and the predetermined dynamic characteristics of the particular building environment such that the control signal will anticipate further change in the conditions within the building environment and will operate the refrigeration unit so as to counter the anticipated further change and tend to maintain the desired comfort level

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.

Abstract: A compressor fault detection and control system for a reverse cycle refrigeration system for detecting faulty compressor operation and for controlling the system in response to the detection of a fault by inhibiting the compressor and for providing a fault indication, the control system comprising a controller means receiving inputs indicative of the outdoor air temperature, the temperature of the compressor discharge refrigerant, and an output indicative of a demand from a building temperature sensing means for heating or cooling of the building. The controller means also includes timing means and means for comparing the value of the compressor discharge temperature and the value of the outdoor air temperature.

Abstract: A compressor start fault detection and control system for a reverse cycle refrigeration system for detecting faulty compressor startup operation and for controlling the system in response to the detection of a fault by inhibiting the compressor and for providing a fault indication, the control system comprising a controller means receiving an input indicative of the temperature of the compressor discharge refrigerant and an output indicative of a demand from a building temperature sensing means for heating or cooling of the building.

Abstract: A temperature compensated safety control is employed to shut off the compressor at high compression ratios, caused, for example, by reduced air flow over the condenser or other reasons. This is especially useful on both reverse cycle heat pumps and conventional, non-reversible refrigeration and air conditioning systems to protect the compressor. In a preferred embodiment, the temperature compensation is provided by making the control responsive to outdoor ambient air temperatures.