Abstract: A temperature controller and method of controlling temperature for use in a refrigerating device includes a temperature sensor for detecting temperature in a compartment of the refrigerator, a conversion element, a refrigerating cycle driving element, a comparison element, and a memory element. The conversion element converts the temperature detected by the temperature sensor into a voltage value. The refrigerating cycle driving element operates a refrigerating cycle to cool the compartment in accordance with the voltage value. The comparison element compares the voltage value with a predetermined voltage range. This predetermined voltage range is wider than a voltage range corresponding to an ordinary operating temperature range at which the temperature in the compartment is maintained.

Abstract: A variable capacity refrigeration system includes a control scheme having three interrelated closed loops. The system includes a refrigeration system controller and at least one variable speed, electronically commutated DC motor driving a compressor. In the first closed loop, the controller supplies a speed command signal to a motor drive which governs the speed of the motor driven compressor. The speed of the compressor varies the system's capacity to condition the temperature of a comfort zone. A temperature sensor in the zone provides a temperature feedback signal to the controller to complete the first closed loop. In the second closed loop, the speed command signal from the controller is varied in response to a speed feedback signal received from a compressor drive which includes both the motor and the motor drive. The third closed loop is between the motor drive and the motor.

Abstract: When the temperature of an internal heat-exchanger decreases below a first value in cooling mode, a normal operation, wherein a variable capacity compressor operates in response to the temperature in a space to be cooled, stops temporarily, and a defrost operation, in which the driving frequency of the compressor periodically decreases by a prescribed value until the temperature of the internal heat-exchanger increases above a second value greater than the first value, begins. When the temperature of the internal heat-exchanger increases above a second value greater than the first value, the compressor operates in response to the temperature in the space. When the compressor stops during the defrost operation, the temperature of the internal heat-exchanger is compared with a third value greater than the second value and the operation of the compressor responding to the temperature in the space is inhibited until the temperature of the internal heat-exchanger increases above the third value.

Abstract: A method and an apparatus of automatically switching between cooling and heating of an air conditioner, has which is a first temperature higher than a desired room temperature, a second temperature which lower than the desired room temperature, a first temperature zone not less than the first temperature, and a second temperature zone not more than the second temperature. The method includes the steps of changing an operation mode from a cooling mode to a heating mode during the cooling mode when the room temperature after duration of a first time remains in the second temperature zone, and changing the operation mode from the heating mode to the cooling mode during the heating mode when the room temperature after duration of a second time remains in the first temperature zone.

Abstract: An electric signal T1 representing the evaporating temperature of refrigerant is processed by a phase lead network and thus converted to T1' with a single time constant so as to compensate for the time lag due to the time constant of a temperature sensor for sensing the evaporating temperature. An electrical signal T2 representing superheated vapor temperature at the outlet of an evaporator is processed by a phase lag network and thus converted to T2', so as to have a larger time constant than that of the unprocessed signal T2 and a signal corresponding to .DELTA.T'=T1'-T2' is used to control the degree of valve opening of an electric expansion valve.

Abstract: A refrigerator control for operating a refrigerator which may experience an abnormal temperature condition due to operation in low ambient temperatures includes a temperature sensor for sensing the temperature of a portion of a refrigerator compartment in order to detect an abnormally low temperature in another portion of the compartment. If the compartment temperature at the end of a predetermined length of time since cooling was last supplied to the compartment is below a predetermined value, then an abnormal condition is assumed to exist and corrective action is taken to eliminate the abnormal condition. A preferred form of corrective action is to prevent compressor re-energization until the compartment temperature reaches a second predetermined value.

Abstract: Apparatus for detecting frost buildup on an evaporator (34) of a refrigeration system (10) includes an air velocity sensor (42) in the air flow path. The sensor is connected to an analog to digital converter (46) which delivers binary signals representative of air velocity to a microcomputer (50) which includes a processor and a memory. Microcomputer (50) is programmed to prompt an operator through a screen (56) at a user station (52) to input an air flow reduction factor at a keyboard (54). The microcomputer uses the air flow reduction factor and the velocity sensed when the evaporator is fully defrosted to calculate a defrost initiation value. When the air velocity sensed at the sensor is no longer greater than the initiation value the microcomputer generates a defrost initiation signal. The microcomputer also includes a timer clock and periodically prints at a printer (58) the time and the velocity sensed.

Abstract: A freezer machine includes a freezing vessel arranged to freeze an amount of water for ice or ingredients for ice cream or similar cold products introduced thereinto, a refrigeration circulation circuit including a compressor, a condenser and an evaporator coil arranged for thermal exchange with the freezing vessel, and a solenoid valve disposed within a bypass circuit connected in parallel with the refrigeration circulation circuit to supply therethrough the hot gas outflowing from the compressor directly into the evaporator coil when the solenoid valve has been energized. A power supply circuit for the freezer machine is designed to deactivate the compressor at a predetermined time before the end of ice or ice cream or cold product preparation, and to energize the solenoid valve in response to deactivation of the compressor.

Abstract: A ratiometric temperature controller for a transport refrigeration system, and a method of controlling the load temperature of a transport refrigeration system with digital signals, without the necessity of utilizing a digital computer. The method, implemented by the ratiometric controller, includes the steps of providing an analog ratio between the load temperature and a selected set point temperature, converting the analog ratio to a digital signal, and providing a logic array which is programmed to provide a plurality of transport refrigeration system control signals in response to predetermined values of the digital signal.

Abstract: In a temperature control system when can be operated as a heat pump, frost deposited onto an outdoor heat exchanger (evaporator) is detected by a change in temperature of the refrigerant which flows into an indoor heat exchanger (condenser), so that a sensor to detect the deposition of the frost need not be attached to the outdoor heat exchanger. The refrigerant temperature is measured at the inlet of the indoor heat exchanger, and the temperature control system is switched to defrosting operation on the basis of this temperature and various elapsed time periods if the actual heat capability of the incoming refrigerant is insufficient, detecting the temperature of the refrigerant on the inlet side of the indoor heat exchanger, namely, by detecting the temeprature at a single position.

Abstract: A method and apparatus for monitoring and protecting a transport refrigeration system, and a load in a load space to be conditioned by the transport refrigeration system. The temperature of the air discharged by the transport refrigeration system into the load space is compared with the returning air temperature to provide a signal D responsive to the algebraic difference. Signal D, which represents the actual conditioning mode, is compared with the commanded conditioning mode of the transport refrigeration system, and also with reference values selected according to whether or not the selected set point temperature of the load space is above or below a predetermined heat lock out temperature, to detect improper operating modes and other malfunctions of the transport refrigeration system, as well as insufficient refrigerant charge.

Abstract: An accessory device for conventional refrigeration systems that include an auxiliary compressor of lower capacity piped in parallel with the compressor of the conventional system. The auxiliary compressor cuts in after a certain temperature is reached and automatically the speed of the fan is decreased to compensate for the lower capacity of the system. Time delays are incorporated to each of the compressors to allow the high and low pressure ports to equalize.

Abstract: A method for randomly delaying a restart of electrical equipment following an availability of power for energizing the equipment includes the steps of measuring an environmental temperature, e.g., the room where the electrical equipment is located, converting a predetermined fractional portion of the value of the sensed temperature to a number and using the number following an availability of power for energizing the equipment after a time period having a duration restarting the equipment. An apparatus employing this method includes a restart control, a temperature sensor and an equipment start programmer responsive to the temperature sensor and connected to the restart control for producing a restart control energizing signal dependent on a predetermined fractional portion of the value of the sensed temperature.

Abstract: A method of operating a switching relay with inductive coils by a microprocessor control to prevent the transient electro-magnetic noise caused by the switching relay from resetting the microprocessor and restarting the program at the beginning. Prior to switching a relay a code is loaded in the memory of the control. After the relay switching noise causes a reset, the control detects the code and jumps back to its proper place without a disruption in its operation.

Abstract: A refrigerator temperature control system is disclosed in which the compressor for compressing a refrigerant is driven selectively at either a normal lower rotation speed or a higher rotational speed and the higher rotational speed is applied only when any of the freezer compartment temperature and the fresh food compartment temperature is not reduced below a predetermined temperature level for at least a predetermined time interval.

Abstract: Herein disclosed is an improved cooling/heating unit incorporated with an automative air conditioner. The unit achieves quick freezing of ice cubes by stopping operation of an electric fan for a predetermined time. The electric fan is located in a refrigerated compartment through which a portion of an evaporator, which also passes through a freezer compartment, is arranged. By suppressing the operation of the fan, the total heat transfer capacity of the system can be directed toward increasing the cooling capacity in the freezer compartment.

Abstract: The present invention is directed to a device for sensing compressor malfunctions and disengaging the compressor from the engine's driving force upon detection of a malfunction. A malfunction is defined herein as the rotation of the compressor below a predetermined speed. In situations where the compressor is on during engine start-up, the engine's starting motor will be exerted to the extent that the engine, and hence the compressor, will not rotate at its proper speed, making engine start-up more difficult. In order for the engine start-up condition not to produce a malfunction detection and erroneously disengage the compressor from the system, a malfunction override circuit is provided. The override circuit comprises a capacitor which is discharged through a transistor connected to the relay for controlling the current to the clutch coil. The relay remains closed due to this capacitor voltage, and the compressor remains engaged, thereby overriding the malfunction detector during engine start-up.

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: Disclosed are refrigeration system control systems and methods for compressor motor protection and defrost control. The disclosed systems and methods are generic in the sense that they are self-calibrating and so may be employed in a variety of different air conditioner or heat pump models of different sizes and capacities, without being specifically tailored for a particular model. The disclosed systems and methods sense loading on the compressor and evaporator fan motors, preferably by sensing the voltage across the capacitor-run winding of an AC induction motor and normalizing with respect to line voltage. The self-calibrating capability is implemented by taking advantage of the changing loads as a function of time on both the compressor and fan motors during both normal and abnormal operation of a refrigeration system. In overview, a reference value of motor loading is established for each motor at certain times during an ON cycle.

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: An air-conditioning apparatus capable of regulating temperature in a plurality of rooms independently of the other by adopting a variable air quantity control system, the apparatus being constructed with heat load measuring device for detecting a temperature condition in each room by a room thermostat and measuring the heat load in the room based on the condition signals derived from the detection of the temperature condition; damper control quantity determining device for determining the degree of opening of a damper in each branched duct on the basis of the measured result of the heat load; damper control device for controlling the degree of opening of the damper on the basis of the determination by the damper control quantity determining device; device for measuring the operating conditions of the air-conditioning apparatus with signals obtained from detection of pressure and temperature within the air duct after the damper control by the damper control device; device for determining the number of revoluti

Abstract: An electronic thermostat for controlling multiple temperature altering apparatus of an animal enclosure or the like employs a linear sensor comprised of an elongate black body, tubular probe containing a semiconductor active element of a current source which produces a sensor current that varies linearly with changes in temperature. A voltage divider to produce a plurality of temperature sensor signals which are used to produce primary of override actuation signals. The set temperature signal is selectable between two set point limits which are selectively variable to calibrate different scales. A plurality of detectors respectively compare the plurality of sensor signals with a common set temperature reference signal to produce a plurality of detection signals at a plurality of preselected temperatures associated therewith.

Abstract: Monitoring apparatus for sensing the temperature within a refrigeration unit that experiences periodic defrosting cycles. The apparatus is capable of discerning the differences between a normal defrost cycle and system failure and provides a warning signal when a failure occurs.

Abstract: This apparatus selects a start-up mode of operation for controlling the compressor (1) at maximum speed only when the difference between the measured temperature of a room at the start of the operation and a target temperature is larger than a predetermined value. A normal mode of operation otherwise is selected for controlling the compressor (1) at a speed lower than maximum thus extending the life of the compressor (1).

Abstract: An energy efficient heat pump dryer for clothes and other washables having a sealed rotatable clothes tumbling drum and means for circulating a stream of heated drying air in a substantially closed path through the tumbling drum. The drum is journaled upon a combined bearing and air seal means at each end. A heat pump is incorporated as the source of heat for the drying air, as a means for recirculating heat from the drying air exhausted from the tumbling drum, and as a means for removing entrained moisture from the exhausted drying air. The dryer is adapted to operate from a 110 volt household power supply and requires no air vent to the outside.

Abstract: A controlled refrigeration system includes a plurality of refrigerant compressors fed from a common suction manifold (line). Each compressor is associated with a respective controller. The individual controllers are set to effect the cutting in of its associated compressor at different levels of input voltage from a pressure transducer using digital techniques. The individual controllers each produce respective digital cut-in, cut-out, down-time delay and power-up delay signals. Respective logic circuitry is provided within each controller for producing control outputs which effect the energization and deenergization of the individual controllers. The compressors are turned on and off in sequence as the demand for compression respectively increases and decreases. The power-up delay period differs for each controller so that no more than one is energized at a given time when the system comes on line after a power failure or extended period of shut down.

Abstract: An outdoor unit of an air conditioner of an engine heat pump type comprises an engine; first and second compressors driven by the engine and having substantially same capacity and heat exchangers for the compressors, said heat exchanger for the first compressor being adapted to utilize an atmosphere as a heat source in a heating operation, said heat exchanger for the second compressor being adapted to utilize a waste heat of the engine as a heat source in the heating operation, a rotation speed of the second compressor being set smaller than that of the first compressor in the heating operation, only the second compressor is adapted to operate in a defrosting operation for the heating operation while utilizing the waste heat of the engine as the heat source, said compressors being adapted to operate in a cooling operation and a rotation speed of the engine and a number of the compressors to be operated being controlled so as to control a cooling capacity in the cooling operation.

Abstract: An air conditioning unit for automobiles is equipped with a bypass passage around the evaporator therein which is adapted to pass a substantial part of the ambient air introduced into the air conditioning unit when the air conditioning is halted. In addition, a control means is provided for controlling the operation of the bypass passage, specifically a time delay circuit to delay the opening and closing of the bypass passage when the air conditioning is stopped and started.

Abstract: A refrigeration system energy controller 10 for controlling the on-Off cycle time of a refrigeration compressor motor 25. A pressure-sensing device 27 senses high and low pressure thresholds in the refrigeration low-side suction line, the high threshold event being converted to a first digital voltage that energizes the refrigeration compressor motor 25, and the low threshold event being converted to a second digital voltage that produces a fixed duration timing signal setting the minimum time duration of the compressor motor 25 on-Off cycle.

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: Control apparatus for producing a control signal indicating that a physical variable has reached a userselected level. A transducer generates for the control apparatus electrical pulses having a repetition period which is a function of the physical variable. The control apparatus repeatedly counts clock pulses in response to the transducer pulses to provide a first digital signal representative of the repetition period of the transducer pulses. The apparatus also repeatedly generates a second digital signal corresponding to the user-selected level of the physical variable by adding to a preset binary code a binary amount related to a userselected voltage. The first and second digital signals are compared to produce the control signal for a switching circuit which responds thereto. The comparison is overriden if an analysis of most significant bits of the first digital signal shows that the physical variable varies beyond a predetermined level.

Abstract: An ice machine control having an on-delay timer in the circuit controlling the circulating water pump so that, at the start of an ice making cycle, the evaporator-ice mold is allowed to cool well below freezing before water begins to circulate to the mold.

Abstract: The specification discloses a vehicle cabin temperature control including a thermostat and a power circuit responsive thereto for selectively applying electrical power to a heating/cooling device. The control further includes a protection circuit coupled to the power circuit for interrupting the power applied to the heating/cooling device when a short-circuit is detected.

Abstract: A programmable maintenance timer system suitable for use with industrial equipment such as a centrifugal water chilling system and a telemetry system including a microprocessor-based computer with a programming device for presetting selectively a maintenance time interval representing a number of hours before a maintenance service is to be performed, for counting down the time interval to zero, and for generating an output signal after the time interval has reached zero to the telemetry system so as to alert service personnel that the industrial equipment is due for a scheduled maintenance. The timer system also includes a non-volatile memory device to record permanently the total elapsed operating hours in the preset maintenance time interval so as to avoid loss of such information upon a power failure and/or back-up battery failure.

Abstract: Method and apparatus are disclosed for controlling the pressure in a single compressor refrigeration system, comprising a timer for establishing a selected time period functionally related to the compressor on-off cycle, a pressure detecting means for establishing and detecting an operating suction pressure range in the system for determining when upper and lower limits of the operating pressure range have been exceeded, means for generating a compressor turn-on signal in response to exceeding the upper limit of the operating pressure range, means for generating a compressor turn-off signal in response to exceeding the lower limit of the operating pressure range, and control means receiving the compressor turn-on signal for applying the turn-on signal to the compressor in response to the suction pressure exceeding the operating pressure range upper limit, the control means receiving the compressor turn-off signal and cooperating with the timer for preventing the application of the turn-off signal to the compr

Abstract: The present invention relates to a defrosting device, for a refrigerator with a number of cooling compartments, which only supplies heat to the evaporator in the fresh food compartment when strictly necessary, that is, when fast defrosting is required, whereas it provides for natural defrosting as long as this is sufficient. In a first arrangement, fast defrosting is performed each cooling cycle but only for part of the time the compressor is off and only after a given temperature threshold has been exceeded by the evaporator in the fresh food compartment or by the freezer. In a second arrangement, fast defrosting is only performed for one out of "n" number of cycles. Both these arrangements provide for energy saving as compared with known technology besides improving fast freezing performance by reducing food freezing time again as compared with known technology.

Abstract: To reduce the probability of top freezing of a fresh cargo 12 in a trailer 10 served by a transport refrigeration unit 14, a control arrangement is provided including a sensor 18 controlling signals according to discharge air temperature fed to a first timer 20 which provides time periods according to the level of discharge air temperature, with shorter duration periods with lower discharge air temperatures, and when timer 20 times out effects actuation of relay 22 to reduce refrigerating capacity and start a duration timer 26 to maintain the reduced refrigeration capacity, with timer 26 functioning through a reset 28 to again start timer 20 when the duration timer has expired, and has caused the relay 22 to be operated to a position of normal refrigerating capacity.

Abstract: A control device for refrigeration cycle constructed with a compressor, a condenser, an electrically operated expansion valve, an evaporator, and so forth, all being connected in series, wherein there are further provided a by-pass extending from an inlet or an outlet or both of the expansion valve upto an inlet of the compressor through a capillary tube; a first temperature sensor to sense a temperature of a cooling medium at the inlet of the compressor; a second temperature sensor to sense a temperature of the cooling medium within an intake tubing, through which the cooling medium is taken into the inlet of the compressor; and a control device which calculates a super-heat quantity of the cooling medium taken into the compressor on the basis of a difference between the detection outputs of the first and second temperature sensors, and controls a degree of opening of the electrically operated expansion valve, thereby enabling the refrigeration cycle to be operated at high efficiency and in an energy-saving

Abstract: The circuit arrangement includes a first voltage divider including a temperature sensitive resistance 18 and resistor R1 which feed an analog signal through line 30 to comparators CP1-4, which also receive reference voltages from a second voltage divider comprising R2-5. CP1 goes high with a falling temperature of 26.degree. F. or lower, CP2 goes high when the temperature falls below 22.degree. F. and CP3 goes high when the temperature falls below 18.degree. F. A first timer 20 is turned on when any of the comparators are turned on and counts pulses from an R-C circuit including R8-11 and C1. Whether R8 and 9 are in the oscillator circuit depends upon whether the bilateral switches S2 and S3 controlled by the comparator CP2 and CP3 have shunted them out. Accordingly, the counting is speeded up as the temperature drops.

Abstract: On an automotive vehicle having a stick-shift transmission and an air conditioner, the air conditioner is turned off by a switch operated by the gear shift lever when shifting from neutral into first gear. The air conditioner is kept off during the relatively brief interval while the transmission is being shifted through the lower gears. The air conditioner comes on after the transmission has been shifted into high gear.

Abstract: An automotive air conditioner has an air duct in which a refrigerant evaporator of a refrigeration cycle is disposed in fluid-flow communication with a variable capacity refrigerant compressor to be drivingly connected to or disconnected from an automotive engine and provided with compressor displacement varying members. The position of the compressor displacement varying members is electronically controlled such that they are placed in the minimum compressor displacement position each time when the compressor operation is started.

Abstract: An apparatus and method is disclosed for regulating delay periods in the operation of an air conditioning system. A speedup means is provided for a serviceman to speed up the delay intervals to avoid long waiting periods between modes of operation of the air conditioning unit. Means are provided for removing the speedup means after delay periods have occurred to prevent inadvertent operation of the air conditioning system with shortened delay intervals.

Abstract: A control system for a low mass hydronic boiler is disclosed which includes a sensor for measuring the temperature of the fluid exiting the boiler. The level of fuel flow provided to the boiler is reduced when the water temperature exceeds a predetermined high temperature limit. The level of fuel flow provided to the boiler is increased only after the water temperature has decreased below a predetermined reset temperature limit and a predetermined interval of time has elapsed.

Abstract: A control system is disclosed for turning a diesel engine on and off to power a refrigeration plant, based on temperature requirements. The desired temperature limits are preset, and when these limits are exceeded, a first timer is set for a desired delay, during which the engine is off; delay times of up to one hour are usual. At the end of this delay time, the first timer will activate glow plugs in the engine. Simultaneously with turning on the glow plugs, a second timer actuates the engine starter after a short delay to start the engine. During the delay period set by the first timer, the diesel engine will be off, and hence, the control system saves diesel fuel and reduces engine maintenance. An electronic circuit for operating the timing system is also disclosed.

Abstract: A control circuit for cycling the evaporator fans on and off independently of the operation of the compressor of the refrigeration system is described. The evaporator fan is cycled on with the compressor and continues to run during the entire compressor ON cycle. A first timer causes the evaporator fan to run for an additional delay period following the cycling OFF of the compressor and the fans continue to blow air over the evaporator coil until the temperature of the evaporator coil is sufficiently above the freezing point of water (32.degree. F., 0.degree. C.). The fans are then cycled OFF. A second cycling timer is provided to intermittently cycle the evaporator fans on and off for predetermined short intervals following the above-described delay period, and during the time when the compressor is OFF. A third timer is provided to preclude freezing of the vended products and/or the evaporator coil when a vending machine is disposed in a below-freezing environment.

Abstract: An airconditioner wherein cooling is performed by forming a refrigerant circulation passage which condenses a refrigerant delivered from a compressor by means of an outdoor heat exchanger and which evaporates it by means of an indoor heat exchanger, while warming is performed while condensing the refrigerant by means of the indoor heat exchanger by furnishing the refrigerant circulation passage with a heating heat exchanger which heats the refrigerant through a heat medium higher in temperature than the open air and which is located in parallel with the outdoor heat exchanger and between the indoor heat exchanger and the suction side of the compressor; characterized by comprising a circuit which bypasses the higher pressure side and lower pressure side of the compressor through a solenoid valve, and a controller which normally closes the bypass circuit during the cooling and normally opens the bypass circuit during the warming and which opens the bypass circuit for a predetermined period of time at the starti

Abstract: A duty cycle controller for an air conditioning system. Solid state switches are connected in series with the heating and cooling switches of a thermostat in circuits for energizing the cooling and heating subsystems, respectively, of an air conditioner. A switch control circuit, when enabled, causes the solid state switches to be conductive when set and nonconductive when reset. Timing signals from a counter applied to the switch control circuit determine the state of the switch control circuit and thus the duty cycles for the heating and cooling subsystem. The controller is provided with a safety circuit which disables the switch control circuit to render the solid state switches nonconductive for a predetermined period of time after a power interruption or after a cooling or heating switch of the thermostat opens. The controller assures that each heating and cooling duty cycle begins with a full energization period. The length of the heating and cooling duty cycles can be readily varied.

Abstract: A control system for an automatic vending machine functions to operate a refrigerator, for example, continuously during a first mode after a power interruption or restocking occurs, and then switches to a non-continuous mode which may be controlled thermostaticly or by cyclicly switching the refrigerator on and off at selected intervals of time. Also, a timer may be set to turn off the refrigerator and other accessories such as lights altogether during selected times of day.

Abstract: A method for controlling the energization of a crankcase heater for use in a refrigeration circuit is disclosed. The crankcase heater is energized through normally closed relay contacts except when the compressor is operating and except for a delay period after compressor operation. A microprocessor control is utilized to calculate the delay period based on the length of the period of compressor operation and to control the energization of the crankcase heater.

Abstract: There is disclosed in combination with a vehicle air conditioning compressor control system that normally cycles a refrigerant compressor on and off according to cooling demand, a timed cycling override control that operates to maintain the compressor on and prevent cycling regardless of cooling demand for a preselected time period when the vehicle speed falls below a predetermined speed and the ambient temperature remains above a preselected temperature.