General Electric Company

Walter J Pohl

William J McCarty

Robert P Alley

Roy W Abbott

George E Stocking

Frederick E Hicks

John W Relyea

Arthur L Burns

Russell L McCreary

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. At later times the then-prevailing motor loading is compared to the stored reference in order to provide a basis for control decisions. The ratio of capacitor-run winding voltage to line voltage is an advantageous indicator of motor loading. In one embodiment, a reference ratio of capacitor-run winding voltage to line voltage is established, and at later times is compared to the then-prevailing ratio of capacitor-run winding voltage to line voltage.

Self-calibrating control methods and systems for refrigeration systems

Refrigeration system control systems and methods for protecting a refrigerant motor/compressor, for example in an air conditioner, against conditions of excessive loading. The systems and methods of the invention recognize and distinguish between conditions of high operating load and insufficient condenser airflow, and take appropriate action for each. High operating load conditions are responded to by providing a motor/compressor cool-down interval, followed by a restart, so that an air conditioner remains operating at its maximum capacity, consistent with the field conditions. Insufficient condenser airflow conditions are responded to by eventually terminating operation of the motor/compressor until, for example, a service technician is called. Operation is based on a recognition that excessive loading conditions are manifested much sooner when the cause is insufficient condenser airflow than when the cause is a high operating load. In the disclosed embodiments, loading on the motor/compressor is sensed, and the motor/compressor is de-energized when a condition of excessive loading is recognized, whatever the cause. After a cool-down interval, the motor/compressor is re-energized, but a count is maintained of the number of times the motor/compressor is de-energized in response to a recognized condition of excessive loading. In order to distinguish between blocked condenser airflow conditions and conditions of excessive load, operation is terminated permanently when the count reaches a predetermined number such as six, but the count is reset when continuous run time exceeds eight minutes.

Blocked condenser airflow protection for refrigeration systems

Calibrated methods and systems for protecting refrigerant motor/compressors against overload and loss of refrigerant conditions, independent of compressor and system size, while avoiding the need for a plurality of sensors. The disclosed methods and systems are generic in the sense that they 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, although a factory calibration adjustment is required. The disclosed methods and systems sense loading on the compressor motor, and make control decisions based thereon. A permanent compressor motor reference loading is established when the refrigeration system has a known correct refrigerant charge and the motor/compressor has a known load. This is typically accomplished in the factory after a predetermined stabilization interval has elapsed following initial start up of the motor/compressor. During operation thereafter, at least a representation of prevailing compressor motor loading is at least periodically sensed. A low-load condition indicative of a loss of refrigerant or of insufficient evaporator airflow is recognized if the prevailing loading is less than a low load threshold loading established as a first predetermined function of the permanent reference loading. A high load condition indicative of an excessive load on the motor/compressor is recognized if the prevailing loading exceeds a high load threshold loading established as a second predetermined function of the permanent reference loading. In either case, the motor/compressor is deenergized.

Protection methods and systems for refrigeration systems suitable for a

Disclosed are apparatus and methods for controlling the defrosting of the outdoor heat exchange coil of a heat pump. In general, the disclosed apparatus and methods use the differencee between the outdoor heat exchanger and the outdoor ambient temperature to determine when to initiate a defrosting operation. Only a single sensor is employed, this single sensor being positioned at least proximate the outdoor heat exchanger such that the sensor responds to ambient temperature when the heat pump is first started and the heat exchanger is free of frost, and such that the sensnor becomes surrounded with frost as frost builds up on the heat exchanger during operation. At the beginning of a run the sensor is employed to read the ambient temperature, which is memorized. As frost builds, the sensor begins to reflect the temperature of the heat exchanger as the sensor becomes increasingly insulated by the frost from the surrounding air. During operation thereafter, the sensor is periodically read, the difference between the prevailing sensor temperature and the stored reference is determined and compared to an established difference reference, and a defrosting operation is initiated if the comparison difference exceeds the difference reference. The single sensor is also employed to determine when to terminate a defrosting operation, and also to determine whether to operate the outdoor fan as an aid to a defrosting operation.

Single-sensor head pump defrost control system

In a self-contained air conditioner unit of the reversible refrigeration type having cooling and heating cycles, a no-drain heat pump is provided wherein in the heating cycle, water collected on the outdoor heat exchanger operating as the system evaporator is transferred to the indoor section. The condensate is directed into the indoor air flow where it is atomized and directed through the relatively warm indoor heat exchanger operating as a condenser to humidify the air. Control means are provided which produces a signal in the event the condensate when present is not being transferred to the indoor section during the heating cycle.

Air conditioning apparatus

A reverse air cycle type heat pump is provided that utilizes a refrigeration system having a unidirection refrigerant flow wherein the condenser and evaporator retain their functions, but the air directed across them is redirected for different operations. The refrigeration system is provided with a secondary defrost circuit including a first conduit between the upper portion of the evaporator and the compressor casing and a second conduit having a valve which permits refrigerant flow to by-pass the expansion device only when compresssor operation terminates and the system pressure differential is equalized. This defrost circuit causes the relatively warm refrigerant in gaseous phase in the compressor to displace the relatively cold refrigerant in liquid phase in the evaporator with the flow continuing until the defrost process is completed.

Refrigeration system gravity defrost

A two-stage circuit for controlling all operational functions of a reversible air cycle heat pump unit, including room thermostat functions and defrosting functions. All user controllable functions are controlled via a remotely locatable thermostat-like control unit mounted on an inside wall of the room separate from the heat pump unit, and connected to the heat pump unit with only five conductors. A number of desirable functions and features are provided. For example, for optimum energy usage the control provides two stages in both heating and cooling modes of operation, with almost constant temperature differential between the two stages regardless of temperature setting, and almost constant hysteresis for each stage. To facilitate compliance with Government-imposed regulations where applicable, heating and cooling limits are independently adjustable without any modification whatsoever for use in those public buildings where heating and cooling must be limited.

Two stage control circuit for reversible air cycle heat pump

An electronic thermostatic control for a heat/cool air conditioning unit and with variable temperature anticipation useful when the unit is located above or below the room's normal zone to compensate for different effects of air stratification as between heat and cool operating modes. A comparator circuit output switches the compressor on and off and a portion of the comparator output is fed back to one of the comparator inputs to effect a degree of temperature anticipation. The feedback is altered by a load impedance switch and into and out of the comparator output circuit to vary the voltage swing on the comparator output and thus to vary the feedback. The amount of alteration of the feedback is selected to achieve the desired variation of temperature anticipation between heating and cooling operating modes.

Electronic thermostatic control for a heat/cool room air conditioning

A versatile yet low cost mode selection control system for an air conditioning unit such as a combination heating and cooling unit having a plurality of operational modes, and which control system is capable of responding both to a relatively local mode selection unit and a relatively remote mode selection unit. Both the relatively local mode selection unit and the relatively remote mode selection unit can exercise independent control over the mode selection, not necessarily limited to mere on/off control, and either may override a selection made at the other at any time. Electronic momentary push button and holding circuitry is employed electronically provide a function similar to that of the prior art mechanical push button configuration wherein only one push button can be actuated at a time, with actuation of any one push button deactuating all others.

Air conditioning control system with local and remote control

Frost control apparatus is disclosed for a temperature conditioning system such as a heat pump or the like, wherein a compressor circulates a volatile fluid through the closed system. Frost-buildup on the indoor and outdoor coils of the system is controlled by means of respective defrost cycles which occur in accordance with the conditions sensed by temperature sensing elements positioned at various points in the system. The defrost cycle for the indoor coil is maintained throughout a predetermined temperature range of ambient indoor air. The defrost cycle for the outdoor coil is initiated as a function of the differential between the temperature of the outdoor coil and that of ambient outdoor air and it varies in magnitude as a function of ambient outdoor air temperature. The termination of the outdoor coil defrost cycle is determined by a sensed temperature condition.

Frost control system

A circuit for protecting single phase induction motors of the type having a start winding connected in series with a start/run capacitor. The circuit contains a resistance bridge wherein the motor start winding forms one leg thereof. A d.c. signal is applied to the input terminals of the bridge. A filter is connected to the output terminals of the bridge so that a relatively ripple free d.c. output signal from the bridge can be applied to the positive input terminal of a d.c. comparator, the negative terminal of which is connected to d.c. reference ground. A reference resistor in a leg of the bridge adjacent the start winding is selected so that the bridge is unbalanced to present a positive d.c. signal to a terminal of the comparator so long as the resistance value of the start winding is less than the value of the reference resistor. An excessive temperature increase of the start winding raises its resistance to equal that of the reference resistor to cause the bridge to balance when the temperature of the start winding reaches a predetermined maximum value, whereupon the comparator switches from a conductive to a non-conductive state. An SCR connected to the comparator output controls the operation of a motor-protecting relay to disengage the motor from its driving source when the bridge becomes balanced and when the comparator switches from one output state to another. A re-start button connected across the SCR permits re-start of the motor after it has been disengaged from its driving source by operation of the comparator.

Circuit for protecting induction motors

A solid state electronic circuit for protecting a single phase induction motor against excessive loading by comparing motor start winding voltage with motor source voltage is disclosed, wherein the circuit automatically removes the motor from its driving source upon the occurrence of such excessive loading. An additional feature includes comparing start winding voltage with source voltage to remove the motor from its driving source upon the occurrence of excessive start winding voltage and corresponding excessive high motor speed. A motor starting circuit to permit the start winding voltage to rise to its normal running level and a time delay restarting circuit to permit the motor to automatically restart after elapse of a selected lock out period following removal of the motor from the source due to insufficient or excessive loading is also provided.

Protective control circuit for induction motors

The present invention provides a restrictor for use in a refrigeration system including the method of adapting its use to the system and more particularly to a restrictor that is formed by providing a flattened portion of tubing that is bent to establish a substantially U-shaped restrictor having diverging leg members connected at their apex by an arcuate segment. Means are provided for moving at least one of the leg members relative to the other so that the diameter of the arcuate segment is altered. Altering the diameter of the arcuate segment causes the cross-sectional area of the restrictor passageway in the segment area to change and, accordingly, the refrigerant flow through the restrictor is effectively adjusted to optimize the refrigeration system efficiency.

Growing community of inventors

Louisville, KY, United States of America

Walter J Pohl