Method and apparatus for controlling capacity of a multiple-stage cooling system

• US 5,067,326 A
• Filed: 08/23/1990
• Issued: 11/26/1991
• Est. Priority Date: 07/31/1979
• Status: Expired due to Term

• Current Assignee: Richard H. Alsenz
• Original Assignee: Richard H. Alsenz
• Inventors: Alsenz, Richard H.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US07/571,746
• Time in Patent Office: 460 Days
• Field of Search: 62/175, 62/226, 62/228.3, 62/117, 62/228.4, 62/193, 236/1 EA, 417/5, 417/7, 417/44, 417/13, 184/6.1, 184/6.16
• US Class Current: 62/193
• CPC Class Codes: F25B 2400/075 with parallel compressors
• CPC Class Codes: F25B 2600/0253 with variable speed
• CPC Class Codes: F25B 2600/111 of condenser fans
• CPC Class Codes: F25B 2600/112 of evaporator fans
• CPC Class Codes: F25B 40/02 Subcoolers
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: G05D 23/1912 whose output amplitude can take more than two discrete values
• CPC Class Codes: G05D 23/20 with sensing elements having variation of electric or magnetic properties with change of temperature G05D23/13 takes precedence
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A refrigeration system is provided with a compressor whose speed is varied to provide load control. In order to prevent compressor damage is lubricating oil pressure sensing control is provided which generates a compressor speed increase signal whenever the oil pressure drops below a predetermined minumum.

Claims

1. Apparatus for controlling the capacity of a refrigeration system having a variable speed compressor, said compressor having an associated suction pressure and a minimum operating oil pressure, said compressor being adapted to operate at variable speeds between a maximum and a minimum speed, said system coprising:

(a) pressure selecting means for establishing an operating suction pressure range;

(b) pressure detection means for sensing the suction pressure and for cooperating with said pressure selecting means to generate a first increase speed signal when said suction pressure exceeds the pressure range, and to generate a decrease speed signal when said suction pressure falls below the pressure range;

(c) oil pressure detection means for providing a second increase speed signal when said oil pressure falls below said minimum operating oil pressure; and

(d) selection means for receiving said first and second increase speed signals and causing the speed of the compressor to increase in respective response thereto, and for receiving the decrease speed signal and causing the speed of the compressor to decrease in response thereto.

2. Apparatus for controlling the capacity of a refrigeration system comprising a variable speed compressor for compressing a refrigerant, said compressor being adapted to operate between a maximum and a minimum speed, said compressor also utilizing oil and having an associated oil pressure, said refrigeration system further including a condenser for condensing the compressed refrigerant, an evaporator connected to said compressor and to said condenser for evaporating said condensed refrigerant and directing siad evaporated refrigerant to said compressor, pressure selection means for establishing a minimum operating oil pressure level, and an oil pressure detection means that generates an increase speed signal when said oil pressure falls below said minimum operating pressure level.

3. A refrigeration system comprising:

(a) a predetermined number of commonly piped compressors wherein one compressor being adapted to operate at variable speeds between a maximum and a minimum speed, said variable speed compressor also having an associated operating oil pressure;

(b) oil pressure selection means for establishing a minimum operating oil pressure level for said variable speed compressor;

(c) oil pressure detection means for determining the oil pressure associated with said variable speed compressor, said oil pressure detectiong means cooperating with said oil pressure selection means to generate a first increase speed signal when said oil pressure exceeds said minimum oil pressure level, and causing the variable speed compressor to increase the speed in response thereto;

(d) pressure selection means for establishing a first and a second suction pressure range, each said pressure range having an upper and a lower limit, the first pressure range being associated with the variable speed compressor and the second pressure range being associated with the remaining compressors;

(e) detection means for sensing the suction pressure and for cooperating with the pressure selection means to provide a second increase speed signal when the suction pressure exceeds the upper limit of the first pressure range, a decrease speed signal when the suction pressure falls below the lower limit of the first pressure range, an increase capacity signal when the suction pressure exceeds the upper limit of the second pressure range and that the variable speed compressor is operating at the maximum speed, and a decrease capacity signal when the suction pressure falls below the lower limit of the second pressure range and that the variable speed compressor is operating at the minimum speed; and

(f) selection means for receiving the second increase speed and the decrease speed signals and in respective response thereto increasing and decreasing the speed of the variable speed compressor, and for receiving the increase capacity and decrease capacity signals and in respective response thereto energizing and de-energizing a compressor of the refrigeration system.

4. The apparatus of claim 3 wherein said compressors have unequal capacity.

5. The apparatus of claim 3 wherein said compressors have equal capacity.

6. A method of controlling a refrigeration system having a variable speed compressor which is adapted to operate between a minimum and maximum speed, the compressor utilizing oil during operation and having an associated oil pressure, said method comprising the steps of:

(a) establishing a minimum oil pressure for operating the compressor;

(b) determining the compressor oil pressure;

(c) generating an increase speed signal whenever the compressor oil pressure falls below the minimum oil pressure level; and

(d) increasing the speed of the compressor in response to the increase speed signal.

7. A method of operating a multiple compressor refrigeration system having a common suction pressure wherein at least one compressor is adapted to operate at a variable speed between a minimum and maximum speed, said varaible speed compressor utilizing oil and having an associated oil pressure, said method comprising the steps of:

(a) establishing a minimum oil pressure for operating the variable speed compressor;

(b) determining the oil pressure associated with the variable speed compressor;

(c) increasing the speed of the variable speed compressor whenever the oil pressure associated with the variable speed compressor falls below the minimum oil pressure and that the variable speed compressor is operating at below the maximum speed;

(d) establishing a minimum common suction pressure;

(e) determining the common suction pressure of the refrigeration system; and

(f) decreasing the speed of the variable speed compressor when the common suction pressure falls below the minimum common suction pressure and that the oil pressure is above the minimum oil pressure level.

8. A method of controlling the capacity of a refrigeration system having a plurality of commonly piped compressors with a common suction pressure, at least one compressor in said plurality of compressors being adapted to operate at variable speeds between a minimum and maximum speed, said variable speed compressor utilizing oil and having an associated oil pressure, said method comprising the steps of:

(a) establishing a minimum oil pressure for the variable speed compressor;

(b) determining the oil pressure of the variable speed compressor; and

(c) increasing the speed of the variable speed compressor whenever the oil pressure of the variable speed compressor falls below the minimum oil pressure level and that the variable speed compressor is operating at a speed below the maximum speed.

9. A method of controlling the capacity of a refrigeration system having a plurality of commonly piped compressors with a suction pressure, at least one compressor in said plurality of compressors operating at variable speeds between a minimum and maximum speed, the variable speed compressor utilizin goil and having an associated oil pressure, said method comprising the steps of:

(a) establishing a minimum oil pressure for the variable speed compressor;

(b) determining the oil pressure associated with the variable speed compressor;

(c) establishing a suction pressure range having an upper and a lower limit;

(d) determining the common suction pressure of the refrigeration system; and

(e) de-energizing a compressor of the compressor system and increasing the speed of the variable speed compressor whenever the oil pressure associated with the variable speed compressor is below the minimum oil pressure level and that the common suction pressure is below the lower limit of the suction pressure range.

10. A method of controlling the capacity of a refrigeration system having a variable speed compressor having a minimum and maximum speed and a plurality of compressors, said compressors having a common suction pressure, said variable speed compressor utilizing oil and having an associated oil pressure, said method comprising the steps of:

(a) establishing a minimum oil pressure for the variable speed compressor;

(b) determining the oil pressure associated with the variable speed compressor;

(c) establishing a suction pressure range having an upper and a lower limit;

(d) determining the common suction pressure of the refrigeration system;

(e) increasing the speed of the variable speed compressor whenever the suction pressure is above the lower limit and the oil pressure falls below the minimum oil pressure level; and

(f) de-energizing a compressor and increasing the speed of the variable speed compressor whenever the oil pressure falls below the minimum oil pressure level and that the suction pressure is below the lower limit.

11. The method of claim 10 wherein the upper and the lower limits are the same.

12. The method of claim 10 wherein the compressors in said plurality of compressors have unequal capacity.

13. The method of claim 10 wherein the compressors in said plurality of compressors have equal capacity.