Environmental control unit for harsh conditions

Abstract

A method of controlling an air conditioning system of the type having a variable capacity compressor circulating refrigerant through a condenser, an expander, an evaporator and returning to the compressor. Sensors are disposed to sense a refrigerant condition selected from one of pressure and temperature on one or both the compressor high pressure and low pressure side; and, in the event of an overload condition, the sensors generate a control signal that effects operation of an actuator for moving a member in the compressor to vary the compressor capacity to the lowest capacity output. Alternatively, the generated control signal may vary the compressor speed.

1 . A method of controlling cooling rate in an air conditioning system of the type circulating refrigerant from a compressor with a variable capacity control mechanism to an outdoor heat exchanger through an expander to an indoor heat exchanger and return, comprising:
 (a) providing an electrically operated actuator and effecting movement of the compressor variable capacity mechanism;   (b) sensing a compressor high side condition and generating a first electrical signal indicative thereof;   (c) sensing a compressor low side condition and generating a second electrical signal thereof; and,   (d) connecting said first and second sensor signals in a circuit and generating an electrical control signal in response to one of first and second signals and controlling the electrically operated actuator with the control signal and varying the compressor capacity.   
     
     
         2 . The method defined in  claim 1 , wherein said step of the compressor low side condition includes sensing the indoor heat exchanger discharge temperature. 
     
     
         3 . The method defined in  claim 1 , wherein the steps of sensing a condition includes sensing one of pressure and temperature. 
     
     
         4 . The method defined in  claim 1 , further comprising sensing ambient temperature in the area to be air conditioned and generating a third electrical signal indicative thereof and changing the control signal in response to said third signal. 
     
     
         5 . The method defined in  claim 1 , wherein the step of connecting an electrically operated actuator includes connecting a solenoid operated valve. 
     
     
         6 . The method defined in  claim 1 , wherein the step of connecting an electrically operated actuator includes connecting an electromagnet. 
     
     
         7 . A method of controlling refrigerant circulating through a variable capacity compressor, an exothermic heat exchanger, an expander, an endothermic heat exchanger and return comprising:
 (a) sensing a refrigerant condition on the compressor high side;   (b) sensing a refrigerant condition on the compressor low side; and,   (c) reducing the compressor variable capacity when an overload condition is sensed in one of steps (a) and (b).   
     
     
         8 . The method described in  claim 7 , wherein the step of sensing a refrigerant condition on the compressor high side includes sensing one of refrigerant pressure and temperature. 
     
     
         9 . The method defined in  claim 7 , wherein the step of sensing a refrigerant condition on the compressor low side includes sensing one of pressure and temperature. 
     
     
         10 . The method defined in  claim 7 , wherein the steps of sensing include:
 (a) generating an electrical control signal indicative of the sensed condition; and,   (b) the step of varying compressor capacity includes disposing a servomechanism receiving the electrical control signal and moving a control member in the compressor.   
     
     
         11 . The method defined in  claim 7 , the step of sensing a condition of the refrigerant on the compressor high side includes sensing a condition intermediate the expander and the endothermic heat exchanger. 
     
     
         12 . The method defined in  claim 11 , wherein the step of sensing a refrigerant condition intermediate the expander and the endothermic heat exchanger sensing one of temperature and pressure. 
     
     
         13 . The method defined in  claim 7 , wherein the steps of changing the compressor variable capacity includes:
 (a) connecting an electrically operated actuator to the compressor;   (b) generating a low capacity control signal in response to sensing an overpressure or the compressor high side; and,   (c) applying the low capacity control signal to the actuator and varying the compressor for lowest capacity.   
     
     
         14 . The method defined in  claim 13 , wherein the step of generating a control signal includes disposing at least one pressure switch and changing circuit resistance upon actuation of the pressure switch. 
     
     
         15 . The method defined in  claim 13 , wherein the step of generating a control signal includes disposing a thermistor in circuit and varying the resistance in response to sensed refrigerant temperature. 
     
     
         16 . The method defined in  claim 13 , wherein the step of generating a control signal includes sensing the air temperature in the area to be cooled. 
     
     
         17 . The method defined in  claim 7 , wherein the step of sensing a high-side condition includes sensing compressor discharge temperature. 
     
     
         18 . The method defined in  claim 7 , wherein the step of changing the compressor capacity includes changing the compressor speed. 
     
     
         19 . An environmental control unit comprising:
 a variable output compressor;   an outdoor coil connected to said variable output compressor via a first conduit;   an indoor coil connected to said variable output compressor via a second conduit; and,   a controller for said variable output compressor compressor, said controller comprising:
 a first sensor connected to said first conduit for sensing a compressor high side condition and generating a first signal; and, 
 a control circuit for generating a control signal in response to said first signal in order to reduce a capacity of said variable output compressor. 
   
     
     
         20 . The unit of  claim 19 , further comprising:
 a second sensor connected to said second conduit for sensing a compressor low side condition and generating a second signal;   wherein said control circuit generates a control signal in response to said second signal.   
     
     
         21 . The unit of  claim 19 , wherein said first and second sensors comprise one of a pressure sensor and a temperature sensor. 
     
     
         22 . The unit of  claim 19 , wherein said first and second sensors are positioned in series. 
     
     
         23 . A method of controlling cooling rate in an air conditioning system of the type circulating refrigerant from a compressor with a variable capacity to an outdoor heat exchanger through an expander to an indoor heat exchanger and return, comprising:
 (a) sensing at least one of a compressor high side condition and a compressor low side condition;   (b) generating a control signal indicative sensed condition; and,   (c) varying the compressor capacity in response to the control signal.