Control system for an air conditioning/refrigeration system

• US 5,203,179 A
• Filed: 03/04/1992
• Issued: 04/20/1993
• Est. Priority Date: 03/04/1992
• Status: Expired due to Term

• Current Assignee: Ecoair Corp.
• Original Assignee: Ecoair Corp.
• Inventors: Powell, James W.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US07/845,675
• Time in Patent Office: 412 Days
• Field of Search: 62/180, 62/186, 62/209, 62/210, 62/212, 62/224, 62/225, 62/226, 62/227, 62/228.4, 62/216
• US Class Current: 62/180
• CPC Class Codes: F04D 27/0261 by varying driving speed
• CPC Class Codes: F24F 1/00 Room units for air-conditioning, e.g. separate or self-contained units or units receiving primary air from a central station
• CPC Class Codes: F24F 11/00 Control or safety arrangements
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/32 Responding to malfunctions or emergencies
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/64 using pre-stored data
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 11/871 by controlling outdoor fans
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2140/00 Control inputs relating to system states
• CPC Class Codes: F24F 2140/12 Heat-exchange fluid pressure
• CPC Class Codes: F24F 2140/50 Load
• CPC Class Codes: F24F 2221/56 Cooling being a secondary aspect
• CPC Class Codes: F25B 2600/021 Inverters therefor
• CPC Class Codes: F25B 2600/21 Refrigerant outlet evaporator temperature
• CPC Class Codes: F25B 41/34 with the valve member being actuated by electric means, e.g. by piezoelectric actuators
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A microprocessor-based air conditioning/refrigeration control system adapted for use with a variable speed compressor measures acceleration of the compressor and the temperature or pressure of the refrigerant exiting therefrom, determines the rate of change of the temperature or pressure of the refrigerant, and decreases acceleration of the compressor if the rate of change of the temperature or pressure of the working fluid indicates surging of the compressor. Superheat of the refrigerant is maintained at a first predefined level while the compressor is operating at constant speed and is increased to a second, higher predefined level while the compressor is accelerating. The system is able to diagnose deterioration of the compressor by measuring and comparing power input to the compressor and rate of change of temperature or pressure of the refrigerant at the compressor between initial and subsequent periods, and differentiate between deterioration of a drive component or a pressurizing component of the compressor.

Claims

1. A method of controlling a refrigeration system having a working fluid and, in sequence, an evaporator, a variable speed centrifugal compressor, a condenser and an expansion valve, comprising:

a) operating said compressor at a constant speed;

b) maintaining said working fluid a first predefined level of superheat between said evaporator and said compressor while said compressor is operating at constant speed;

c) accelerating rotation of said compressor;

d) increasing the superheat of said working fluid between said evaporator and said compressor to a second predefined level above said first predefined level and maintaining the superheat at said second predefined level while said compressor is accelerating; and

e) decreasing the superheat of said working fluid to said first predefined level when said compressor returns to a constant operating speed.

2. The method of claim 1 wherein said expansion valve is adjustable to vary the flow of said working fluid in the system and wherein the superheat of said working fluid is increased in step (d) by adjusting flow of said working fluid through said expansion valve.

3. The method of claim 1 wherein said evaporator includes a variable speed fan to vary the rate of heat transfer of said working fluid and wherein the superheat of said working fluid is increased in step (d) by adjusting heat transfer of said working fluid at said evaporator.

4. Apparatus for controlling a refrigeration system having a working fluid and, in sequence, an evaporator, a variable speed centrifugal compressor, a condenser and an expansion valve, comprising:

a sensor for determining when said compressor is operating at a constant speed;

a microprocessor control for maintaining said working fluid at a first predefined level of superheat between said evaporator and said compressor while said compressor is operating at constant speed;

a sensor for determining when rotation of said compressor is accelerating; and

a microprocessor control for increasing the superheat of said working fluid between said evaporator and said compressor to a second predefined level above said first predefined level and maintaining the superheat at said second predefined level while said compressor is accelerating.