Method and apparatus for monitoring and controlling the operation of a refrigeration unit

• US 5,303,560 A
• Filed: 04/15/1993
• Issued: 04/19/1994
• Est. Priority Date: 04/15/1993
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Thermo King Corporation (Trane Technologies plc)
• Inventors: Hanson, Jay L., Herrig, Doyle G.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US08/046,314
• Time in Patent Office: 369 Days
• Field of Search: 62/125, 62/126, 62/127, 62/129, 62/230, 340/664, 361/22, 361/31, 361/87, 361/93, 361/94, 361/97, 236/94, 165/11.1
• US Class Current: 62/126
• CPC Class Codes: B60H 1/3225 characterised by safety arrangements, e.g. compressor anti-seizure means or by signalling devices
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25D 29/003 for movable devices
• CPC Class Codes: G05D 23/1917 using digital means

Abstract

Methods and apparatus for monitoring and controlling the operation of a refrigeration unit in a manner which eliminates the need for circuit breakers and fuses in control circuits which are instrumental in selecting and changing the operational mode of the refrigeration unit. When a need to change to a different operating mode is detected, a controller energizes a control device associated with the different operating mode and quickly determines if the current draw is within an acceptable range. If the current draw is within an acceptable range or window, the controller initiates the requested different operating mode. If the current draw is not within the acceptable range, the controller generates an appropriate alarm and different courses of action are decided upon which depend upon whether the current draw is above or below the limits of the acceptable range, the nature of the requested operating mode, and the desired temperature of a space conditioned by the refrigeration unit.

Claims

1. A method of operating and monitoring a refrigeration unit which includes electrical control having a voltage source, a control circuit which includes a plurality of control devices, and a controller which selectively energizes and de-energizes the control devices via a plurality of control outputs, comprising the steps of:

determining if the refrigeration unit is running,

de-energizing the control outputs of the controller when the determining step finds the refrigeration unit is not running,

measuring the magnitude of the current draw of the control circuit from the voltage source with the control outputs of the controller de-energized,

providing a current reference value which indicates the maximum allowable current draw with the control outputs of the controller de-energized,

comparing the measured current draw with the reference value, and

providing an alarm which indicates the controller should be checked when the measured current draw exceeds the reference value.

2. The method of claim 1 wherein the plurality of control components includes a predetermined control device which enables starting of the refrigeration unit, and including the steps of:

determining if the unit should be started when the unit is found not running,

energizing the predetermined control device which enables the starting of the refrigeration unit, when the unit should be started,

measuring the magnitude of the current draw of the control circuit after the predetermined control device is energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the predetermined control device energized,

comparing the latest measured current draw with the current draw window,

starting the unit when the measured current draw is within the limits of the current draw window, and

de-energizing the predetermined control device when the measured current draw is not within the limits of the current draw window.

3. The method of claim 2 wherein the refrigeration unit is operable in selectable different operating modes, with the plurality of control devices including a control device associated with each operating mode, and including the steps of:

running the unit, after the starting step, in a predetermined initial operating mode,

determining when a different operating mode is required,

energizing the control device associated with the different operating mode,

measuring the magnitude of the current draw of the control circuit after the control device of the different operating mode is energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the control device of the different operating mode energized,

comparing the latest measured current draw with the current draw window, and

initiating the different operating mode when the latest measured current draw is within the limits of the current draw window.

4. The method of claim 3 including the steps of:

providing an alarm when the latest measured current draw is not within the limits of the current draw window,

allowing the unit to operate with the control device of the different operating mode energized when the latest measured current draw is less than the lower limit of the current draw window, and

shutting the unit down when the latest measured current draw exceeds the upper limit of the current draw window.

5. The method of claim 3 including the steps of:

providing an alarm when the latest measured current draw is not within the limits of the associated current draw window,

allowing the unit to operate with the control device of the different operating mode energized when the latest measured current draw is less than the lower limit of the associated current draw window,

de-energizing the control device when the latest measured current draw exceeds the upper limit of the associated current draw window,

measuring the current draw after the control device of the different operating mode is de-energized,

providing a maximum current reference value which indicates the maximum allowable current with the control device of the different operating mode de-energized,

comparing the latest measured current draw with the maximum current reference value,

allowing the unit to run with the control device of the different operating mode de-energized when the latest measured current draw does not exceed the maximum current reference value, and

shutting the unit down when the latest measured current draw exceeds the maximum current reference value.

6. The method of claim 2 wherein the starting step started the unit running, and wherein the refrigeration unit controls a conditioned space to a predetermined null temperature range adjacent to a selected set point temperature via heating, cooling and null cycles, and including the steps of:

determining when conditions for a null cycle are satisfied,

de-energizing the control outputs of the controller when the determining step finds that conditions for a null cycle are satisfied,

measuring the magnitude of the current draw of the control circuit with the control outputs of the controller de-energized,

providing a current reference value which indicates the maximum allowable current draw with the control outputs of the controller de-energized,

comparing the latest measured current draw with the reference value,

initiating a null cycle when the latest measured current draw does not exceed the reference value, and

providing an alarm which indicates the controller should be checked when the latest measured current draw exceeds the reference value.

7. A method of operating and monitoring a refrigeration unit operable in a plurality of different selectable operating modes, including electrical control having a voltage source, a control circuit which includes a plurality of control devices associated with the plurality of operating modes, and a controller which selectively energizes and de-energizes the control devices via a plurality of control outputs, comprising the steps of:

determining when a change from one operating mode to a different operating mode is required,

energizing the control device associated with the different operating mode,

measuring the magnitude of the current draw of the control circuit after the control device of the different operating mode is energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the control device of the different operating mode energized,

comparing the measured current draw with the current draw window, and

initiating the different operating mode when the measured current draw is within the current draw window.

8. The method of claim 7 wherein the plurality of control devices includes a predetermined control device which enables starting of the refrigeration unit, and including the steps of:

determining if the unit should be started when the unit is not running,

energizing the predetermined control device which enables the starting of the refrigeration unit, when the unit should be started,

measuring the magnitude of the current draw of the control circuit after the predetermined control device is energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the predetermined control device energized,

comparing the latest measured current draw with the current draw window,

starting the unit when the measured current draw is within the limits of the current draw window, and

de-energizing the predetermined control device when the measured current draw is not within the current draw window.

9. The method of claim 8 including the step of running the unit, after the starting step, in a predetermined initial operating mode.

10. The method of claim 8 including the step of providing an alarm which indicates the predetermined control device should be checked when the latest measured current draw is not within the associated current draw window.

11. The method of claim 7 wherein the refrigeration unit is operable in low and high speed modes and the electrical control includes a high speed control device controllable by an output of the controller which is energized to change to a high speed mode, and including the steps of:

determining when a high speed mode is required, energizing the high speed control device when the high speed mode is required,

measuring the magnitude of the current draw of the control circuit with the high speed control device energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the high speed control device energized,

comparing the latest measured current draw with the current draw window, and

initiating the high speed mode when the latest measured current draw is within the current draw window.

12. The method of claim 11 including the steps of:

providing an alarm when the latest measured current draw is outside the associated current draw window,

allowing the unit to operate with the high speed control device energized when the measured current is below the lower limit of the current draw window,

de-energizing the high speed control device when the measured current draw exceeds the upper limit of the current draw window,

measuring the current draw after the high speed control device is de-energized,

providing a maximum allowable current reference value,

comparing the latest measured current draw with the reference value,

allowing the unit to operate with the high speed control device de-energized when the comparison step finds that the measured current draw does not exceed the reference value, and

shutting the unit down when the comparison step finds that the measured current draw exceeds the reference value.

13. The method of claim 7 wherein the refrigeration unit is operable in cooling and heating modes and the electrical control includes a heat control device controllable by an output of the controller which is energized to change from a cooling mode to a heating mode, and including the steps of:

determining when a heating mode is required,

energizing the heat control device,

measuring the magnitude of the current draw of the control circuit with the heat control device energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the heat control device energized,

comparing the latest measured current draw with the current draw window, and

initiating the heating mode when the measured current draw is within the current draw window.

14. The method of claim 13 wherein the refrigeration unit controls the temperature of a conditioned space to a selected set point temperature, and including the steps of:

determining if the selected set point temperature is above or below a predetermined value which respectively indicates non-frozen and frozen loads in the conditioned space,

allowing the unit to operate with the heat control device energized when the latest measured current draw is below the lower limit of the current draw window and the selected set point temperature indicates a frozen load,

shutting the unit down when the measured current draw is below the lower limit of the current draw window and the selected set point temperature indicates a nonfrozen load,

de-energizing the heat control device when the latest measured current draw exceeds the upper limit of the current draw window,

measuring the current draw after the heat control device is de-energized,

providing a maximum allowable current reference value,

comparing the latest measured current draw with the reference value,

allowing the unit to operate with the heat control device de-energized when the comparison step finds that the latest measured current draw does not exceed the reference value and the selected set point temperature indicates a frozen load,

shutting the unit down when the comparison step finds that the latest measured current draw exceeds the reference value, and

shutting the unit down when the comparison step finds that the latest measured current draw is less than the reference value and the selected set point temperature indicates a non-frozen load.

15. The method of claim 13 wherein the refrigeration unit is operable in low and high speed modes and the electrical control includes a high speed control device controllable by an output of the controller which is energized to change to a high speed heat mode, and including the steps of:

determining when a high speed heat mode is required when the heat control device is energized,

energizing the high speed control device,

measuring the magnitude of the current draw of the control circuit with the heat control device and the high speed control device energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the heat control device and the high speed control device energized,

comparing the latest measured current draw with the current draw window, and

initiating the high speed heat mode when the measured current draw is within the limits of the current draw window.

16. The method of claim 15 including the steps of:

providing an alarm when the latest measured current draw is outside the limits of the current draw window,

allowing the unit to operate with the high speed control device energized when the latest measured current draw is below the lower limit of the current draw window,

de-energizing the high speed control device when the measured current draw exceeds the upper limit of the current draw window,

measuring the current draw after the high speed control device is de-energized,

providing a maximum allowable current reference value,

comparing the latest measured current draw with the reference value,

allowing the unit to operate with the high speed control device de-energized when the comparison step finds that the latest measured current draw does not exceed the reference value, and

shutting the unit down when the comparison step finds that the latest measured current draw exceeds the reference value.

17. The method of claim 7 wherein the refrigeration unit is operable in a defrost mode, with the refrigeration unit including an evaporator coil, a defrost damper, and a damper control device controllable by an output of the controller, and including the steps of:

determining when a defrost mode should be initiated to defrost the evaporator coil,

energizing the damper control device when a defrost mode is required,

measuring the magnitude of the current draw of the control circuit with the damper control device energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the damper control device energized,

comparing the latest measured current draw with the current draw window,

providing an alarm when the latest measured current draw is outside the limits of the current draw window,

de-energizing the damper control device when the measured current draw is outside the limits of the current draw window,

measuring the current draw after the damper control device is de-energized,

providing a maximum allowable current reference value,

comparing the latest measured current draw with the reference value,

allowing the unit to operate with the damper control device de-energized, and disabling the defrost mode, when the comparison step finds that the latest measured current draw does not exceed the reference value, and

shutting the unit down when the comparison step finds that the latest measured current draw exceeds the reference value.

18. The method of claim 17 wherein the control includes a heat control device controllable by an output of the controller, and including the steps of:

storing the measured current draw when the current draw for the damper control device is within the limits of the associated current draw window,

energizing the heat control device when the current draw for the damper control device is within the limits of the associated current draw window,

measuring the magnitude of the current draw of the control circuit with the damper control device and the heat control device energized,

providing a current draw window having upper and lower limits which include the value stored in the storing step, to provide a current draw window which defines an allowable current draw range for the control circuit with the heat control device and damper control device both energized,

comparing the latest measured current draw with the associated current draw window, and

initiating the defrost mode when the latest measured current draw is within the current draw window.

19. The method of claim 18 including the steps of:

providing an alarm when the measured current draw with the damper control device and the heat control device both energized is outside the associated current draw window,

de-energizing the heat control device when the measured current draw with the damper control device and the heat control device both energized is outside the current draw window,

measuring the current draw after the heat control device is de-energized, when the upper limit of the associated current draw window is exceeded,

comparing the latest measured current draw with the stored current draw,

shutting the unit down when the measured current draw exceeds the stored current draw,

de-energizing the damper control device when the measured current draw does not exceed the stored current draw, and also when the measured current draw with both the damper and heat control devices energized is below the lower limit of the associated current draw window,

measuring the current draw after the damper control device is de-energized,

providing a maximum allowable current draw reference value,

comparing the latest measured current draw with the reference value,

allowing the unit to operate with the damper control device de-energized when the latest measured current draw does not exceed the reference, and

shutting the unit down when the comparison step finds that the latest measured current draw exceeds the reference value.

20. The method of claim 18 including the steps of:

detecting when the defrost mode should be terminated,

de-energizing the heat control device when the detecting step detects termination of defrost,

measuring the current draw after the heat control device is de-energized,

comparing the latest measured current draw with the stored current draw,

providing an alarm when the latest measured current draw exceeds the stored current draw,

shutting the refrigeration unit down when the latest measured current draw exceeds the stored current draw,

de-energizing the damper control device when the measured current draw does not exceed the stored current draw,

measuring the current draw after the damper control device is de-energized,

providing a maximum allowable current reference value,

comparing the latest measured current draw with the reference value,

allowing the unit to run when the comparison step finds the latest measured current draw does not exceed the reference value,

providing an alarm when the comparison step finds the latest measured current draw exceeds the reference value, and

shutting the unit down when the comparison step finds the latest measured current draw exceeds the reference value.

21. The method of claim 20 including the step of providing a delay before the damper control device is de-energized, to allow the evaporator coil to cool before the defrost damper is opened by the damper control device.

22. The method of claim 7 wherein the refrigeration unit is operable in a hot gas by-pass mode and the electrical control includes a hot refrigerant gas by-pass control device controllable by an output of the controller which is energized to initiate a hot gas by-pass mode, and including the steps of:

determining when a hot gas by-pass mode is required,

energizing the hot gas by-pass control device,

measuring the magnitude of the current draw of the control circuit with the hot gas by-pass control device energized,

providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the hot gas by-pass control device energized,

comparing the latest measured current draw with the current draw window,

providing an alarm when the latest measured current draw is outside the limits of the current draw window,

de-energizing the hot gas by-pass control device when the latest measured current draw is less than the lower limit of the current draw window,

allowing the unit to run with the hot gas by-pass control device energized when the latest measured current draw is less than the lower limit of the current draw window,

de-energizing the hot gas by-pass control device when the latest measured current draw exceeds the upper limit of the current draw window,

measuring the current draw after the hot gas by-pass control device is de-energized,

providing a maximum allowable current reference value for the current draw with the hot gas by-pass control device de-energized,

comparing the latest measured current draw with the reference value,

allowing the unit to run with the hot gas by-pass control device de-energized when the latest measured current draw does not exceed the reference value, and

shutting the unit down when the latest measured current draw exceeds the reference value.

23. The method of claim 22 wherein the refrigeration unit is operable in a suction line modulation mode, and the refrigeration unit includes a suction line modulation valve, and including the steps of:

determining if the suction line modulation mode is required after the measured current draw is found to be within the associated current draw window,

operating the unit with the hot gas by-pass control device energized when the determining step finds that the modulation mode is not required,

storing the measured current draw when the determining step finds that the modulation mode is required,

energizing the modulation valve when the determining step finds that the modulation mode is required,

measuring the current draw after the step of energizing the modulation valve,

providing a current draw window having upper and lower limits which include the stored value, defining an allowable current draw range for the control circuit with the hot gas by-pass control device and modulation valve both energized,

comparing the latest measured current draw with the current draw window, and

initiating the hot gas by-pass mode with the modulation mode when the latest measured current draw is within the limits of the associated current draw window.

24. The method of claim 22 including the steps of:

determining when the modulation mode is not required,

de-energizing the modulation valve when the modulation mode is not required,

measuring the current draw after the de-energizing step,

comparing the latest measured current draw with the stored value,

allowing the unit to operate with the modulation valve de-energized when the comparison step finds the latest measured current draw does not exceed the stored value, and

shutting the unit down when the comparison step finds that the latest measured current draw exceeds the stored value.

25. The method of claim 22 including the steps of:

providing an alarm and de-energizing the modulation valve when the measured current draw with the hot gas by-pass control device and modulation valve both energized is not within the associated current draw window,

allowing the unit to operate when the measured current draw is less than the lower limit of the current draw window,

measuring the current draw after the step of de-energizing the modulation valve when the latest measured current draw exceeds the upper limit of the current draw window,

comparing the latest measured current draw with the stored value,

allowing the unit to run when the latest measured current draw does not exceed the stored value, and

shutting the unit down when the latest measured current draw exceeds the stored value.

26. Control apparatus for monitoring and controlling the operation of a refrigeration unit, with the electrical control apparatus including a voltage source, a control circuit which includes a plurality of control devices, and a controller which selectively activates the control devices via a plurality of control outputs, comprising:

a current shunt disposed between the voltage source and the control circuit,

means determining if the refrigeration unit is operating,

means de-energizing the control outputs of the controller when the refrigeration unit is not operating,

means measuring the magnitude of the current draw of the control circuit with the control outputs of the controller de-energized,

means providing a current reference value which indicates the maximum allowable current draw with the control outputs of the controller de-energized,

means comparing the measured current draw with the reference value, and

means providing an alarm which indicates the controller should be checked when the measured current draw exceeds the reference value.

27. The apparatus of claim 26 including:

means for determining if the unit should be started when the unit is found not running,

a control device which, when energized, enables the starting of the refrigeration unit,

means energizing said control device,

means measuring the magnitude of the current flow through the current shunt with the control device energized,

means providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the control device energized,

means comparing the latest measured current draw with the current draw window,

means starting the unit when the latest measured current draw is within the limits of the current draw window, and

means de-energizing the control device when the latest measured current draw is not within the limits of the current draw window.

28. The apparatus of claim 27 including:

means operating the unit, after starting, in a predetermined initial operating mode which requires continuous energization of the control device by the controller,

means providing a plurality of different operating modes, including a control device controllable by an output of the controller for each of the plurality of different operational modes,

means determining when a different operating mode is desired,

means energizing the control device associated with the different operating mode,

means measuring the magnitude of the current flowing through the current shunt when the control device of the different mode energized,

means providing a current draw window having upper and lower limits which define an allowable current draw range for the control circuit with the control device of the different mode energized,

means comparing the latest measured current draw with the current draw window, and

means initiating the desired different operating mode when the measured current draw is within the limits of the current draw window.

29. The apparatus of claim 28 including:

means providing an alarm when the latest measured current draw is not within the limits of the associated current draw window,

means allowing the unit to operate when the latest measured current draw is below the lower limit of the current draw window,

means de-energizing the control device when the latest measured current draw exceeds the upper limit of the current draw window,

means measuring the current draw with the control device de-energized,

means providing a maximum current reference value,

means comparing the latest measured current draw with the maximum current reference value,

means allowing the unit to run when the latest measured current draw does not exceed the maximum current reference value, and

means shutting the unit down when the latest measured current draw exceeds the maximum current reference value.

30. The apparatus of claim 26 wherein the voltage source includes a battery and generator means, and including an additional current shunt connected to measure battery current.