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A cooling system controller controls the capacity of a variable capacity compressor based upon the temperature of a housing being cooled, the suction pressure of the compressor or both of these criteria. The cooling system controller is capable of controlling either single-evaporator or multiple-eva

A cooling system controller controls the capacity of a variable capacity compressor based upon the temperature of a housing being cooled, the suction pressure of the compressor or both of these criteria. The cooling system controller is capable of controlling either single-evaporator or multiple-evaporator refrigeration systems. The multiple-evaporator systems can have evaporators of similar temperatures or of mixed temperatures. The controller also allows the use of one or more condenser fans that are operated in a lead/lag fashion to control the cooling capability of the system.

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1. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable c

1. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing to maintain a specified temperature in said housing; and a vapor injection system for injecting vapor into said compressor at a position intermediate a suction pressure and a discharge pressure, said system controller being coupled to said vapor injection system for controlling injection of said gas. 2. The cooling system according to claim 1, further comprising a temperature sensor for sensing a temperature of gas at said discharge pressure, said system controller being coupled to said temperature sensor for controlling injection of said vapor based on said temperature of said gas at said discharge pressure.3. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; and a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing to maintain a specified temperature in said housing. 4. The cooling system according to claim 3, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.5. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing to maintain a specified temperature in said housing; and a first and a second condenser fan, said controller being coupled to said condenser fans to control said fans based upon a temperature sensed by said temperature sensor, percent duty cycle, and a calculate d minimum pressure differential. 6. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor, wherein said compressor compresses a gas between a suction pressure and a discharge pressure; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; a pressure sensor for sensing said suction pressure; and, a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing and said suction pressure to maintain a specified temperature in said housing. 7. The cooling system according to claim 6, wherein said compressor is a scroll compressor.8. The cooling system according to claim 6, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another.9. The cooling system according to claim 8, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.10. The cooling system according to claim 6, wherein said system controller determines an average suction pressure over a specified period of time within each control cycle time.11. A cooling system comprising: a plurality of housings each having a respective evaporator disposed therein; a condenser coupled in fluid communication with said evaporators; a compressor coupled in fluid communication with said evaporators and said condenser, said compressor being a pulse-width modulated variable capacity compressor; a temperature sensor disposed in at least one of said housings, said temperature sensor operable to read a temperature within said at least one of said housings; and a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said at least one of said housings to maintain a specified temperature in said plurality of housings. 12. A cooling system comprising: a plurality of housings, each having an evaporator, an evaporator controller, and a temperature sensor in each of said plurality of housings, each said temperature sensor operable to read a temperature and connected to said evaporator controller in said each of said plurality of housings; a condenser coupled in fluid communication with said evaporators; a compressor coupled in fluid communication with said evaporators and said condenser, said compressor being a pulse-width modulated variable capacity compressor; and a system controller coupled to said evaporator controller and said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on temperature sensor and demand loading state values communicated to said system controller by said evaporator controller. 13. A cooli ng system comprising: a housing: an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a vapor injection system for injecting vapor into said compressor at a position intermediate a suction pressure and a discharge pressure, said system controller being coupled to said vapor injection system for controlling injection of said gas. 14. The cooling system according to claim 13, further comprising a temperature sensor for sensing a temperature of gas at said discharge pressure, said system controller being coupled to said temperature sensor for controlling injection of said vapor based on said temperature of said gas at said discharge pressure.15. The cooling system according to claim 13, wherein said compressor is a scroll compressor.16. The cooling system according to claim 13, wherein said compressor is a scroll compressor.17. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another; a temperature sensor disposed in said housing and operable to read a temperature within said housing; and a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor. 18. The cooling system according to claim 17, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.19. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a first and a second condenser fan, said controller being coupled to said condenser fans to control said fans based upon a temperature sensed by said temperature sensor, percent duty cycle, and a calculated minimum pressure differential. 20. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser, wherein said compressor compresses a gas between a suction pressure and a discharge pressure, and said cooling system further comprises a pressure sensor for sensing said suction pressure, said system controller being coupled to said pressure sensor for controlling said capac ity of said compressor based on said suction pressure and said temperature within said housing a temperature sensor disposed in said housing and operable to read a temperature within said housing; and a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor. 21. The cooling system according to claim 20, wherein said compressor is a scroll compressor.22. The cooling system according to claim 20, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another.23. The cooling system according to claim 22, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.24. The cooling system according to claim 20, wherein said system controller determines an average suction pressure over a specified period of time within each control cycle time.25. A cooling system comprising: a housing: an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a plurality of housings each having a respective evaporator disposed therein, said temperature sensor being disposed in at least one of said housings. 26. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a plurality of housings, each having an evaporator, an evaporator controller, and a temperature sensor in each of said plurality of housings, each said temperature sensor connected to said evaporator controller in said each of said plurality of housings, each said evaporator controller communicating temperature sensor and demand loading state values to said system controller.