Method and apparatus for refrigeration system control having electronic evaporator pressure regulators

1. In a refrigeration system, a controller operable to meet cooling demand and control suction pressure for a plurality of refrigeration circuits each including a variable valve and an expansion valve, said controller operable to control said variable valves independently of said expansion valves to meet said cooling demand by determining a change in a measured parameter and controlling at least one of said variable valves based upon said change to an approximately fully open position.

2. The controller of claim 1 , wherein said measured parameter is temperature.

3. The controller of claim 1 , wherein said measured parameter is an average of multiple temperature measurements.

4. The controller of claim 1 , wherein said measured parameter is pressure.

5. The controller of claim 1 , wherein said measured parameter is an evaporator pressure regulator valve position.

6. A method comprising:

positioning an expansion valve proximate an evaporator in each circuit of a plurality of refrigeration circuits;

positioning an electronic variable valve in communication with said each circuit of said plurality of refrigeration circuits;

positioning a sensor in communication with said each circuit of said plurality of refrigeration circuits to measure an operating parameter;

communicating a compressor with said electronic variable valves; and

associating a control system with said compressor and said electronic variable valves, wherein said control system is operable to control said compressor while controlling electronic variable valves independently of said expansion valves to meet a demand for cooling and positioning at least one of said electronic variable valves at approximately fully open and positioning another of said electronic variable valves at less than approximately fully open based upon said measured operating parameter.

7. A method comprising:

detecting a temperature or pressure value in each refrigeration circuit of a plurality of refrigeration circuits wherein each of said refrigeration circuits includes an expansion valve;

comparing said detected values to a set point value;

updating an evaporator pressure regulator valve position based on said comparing; and

controlling a suction pressure of each of said refrigeration circuits independently of said expansion valve respectively associated with each of said refrigeration circuits based on said updating until one of said evaporator pressure regulator valves is approximately fully open.

8. The method of claim 7 , wherein said comparing includes PID control.

9. The method of claim 7 , wherein said comparing includes determining an error value and said updating includes adjusting a valve position of each of said evaporator pressure regulators.