Street, Norman E. (O'Fallon, MO, US)
Sunderland, Ted W. (Troy, MO, US)

Plaque It!

11/337911

09/09/2008

01/23/2006

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Hussman Corporation (Bridgeton, MO, US)

374/171

62/228.3, 62/209, 62/228.1

F25B1/00; F25B49/00

374/171, 62/228.3, 62/129, 62/228.1, 62/209, 374/170, 374/152, 62/213, 62/126

3312081	Control apparatus for refrigeration system	April, 1967	Berger et al.
3527059	METHOD OF CONTROLLING PARALLEL-OPERATING REFRIGERATION COMPRESSORS	September, 1970	Rust et al.
3735377	MONITORING AND SHUTDOWN APPARATUS	May, 1973	Kaufman
3783681	METHOD AND APPARATUS TO MONITOR QUALITY OF OPERATION OF A PISTON IN A CYLINDER	January, 1974	Hirt et al.
3874187	REFRIGERANT COMPRESSOR WITH OVERLOAD PROTECTOR	April, 1975	Anderson
4060716	Method and apparatus for automatic abnormal events monitor in operating plants	November, 1977	Pekrul et al.
4071078	Hydronic heating and cooling system	January, 1978	Padden
4084388	Refrigeration control system for optimum demand operation	April, 1978	Nelson
4102394	Control unit for oil wells	July, 1978	Botts
4152902	Control for refrigeration compressors	May, 1979	Lush
4184341	Suction pressure control system	January, 1980	Friedman
4246763	Heat pump system compressor fault detector	January, 1981	Mueller et al.	62/160
4325223	Energy management system for refrigeration systems	April, 1982	Cantley
4333316	Automatic control apparatus for a heat pump system	June, 1982	Stamp, Jr. et al.
4372119	Method of avoiding abnormal combination in an internal combination engine and an arrangement for carrying out the method	February, 1983	Gillbrand et al.
4384462	Multiple compressor refrigeration system and controller thereof	May, 1983	Overman et al.
4390321	Control apparatus and method for an oil-well pump assembly	June, 1983	Langlois et al.
4390922	Vibration sensor and electrical power shut off device	June, 1983	Pelliccia
4399548	Compressor surge counter	August, 1983	Castleberry
4425010	Fail safe dynamoelectric machine bearing	January, 1984	Bryant et al.
4429578	Acoustical defect detection system	February, 1984	Darrel et al.
4463574	Optimized selection of dissimilar chillers	August, 1984	Spethmann et al.
4478051	Electronic temperature control system	October, 1984	Ibrahim
4479389	Tuned vibration detector	October, 1984	Anderson, III et al.
4545210	Electronic program control for a refrigeration unit	October, 1985	Lord
4603348	Method for composing addresses of a memory	July, 1986	Yamada et al.
4614089	Controlled refrigeration system	September, 1986	Dorsey
4633672	Unequal compressor refrigeration control system	January, 1987	Persem et al.
4653280	Diagnostic system for detecting faulty sensors in a refrigeration system	March, 1987	Hansen et al.
4748820	Refrigeration system	June, 1988	Shaw
4811897	Duct type air conditioning system	March, 1989	Kobayashi et al.
4812997	Control apparatus for an air conditioning system	March, 1989	Okochi et al.
4829779	Interface adapter for interfacing a remote controller with commercial refrigeration and environmental control systems	May, 1989	Munson et al.
4842044	Furnace control system	June, 1989	Flanders et al.
4870863	Modular switch device	October, 1989	Duncan et al.	73/431
4884412	Compressor slugging protection device and method therefor	December, 1989	Sellers et al.
4885564	Power line carrier communication system for monitoring refrigerated containers	December, 1989	Vercellotti et al.
4909076	Cavitation monitoring device for pumps	March, 1990	Busch et al.
4913625	Automatic pump protection system	April, 1990	Gerlowski
4951029	Micro-programmable security system	August, 1990	Severson
4958502	Controller for a refrigeration unit	September, 1990	Satoh et al.
4967567	System and method for diagnosing the operation of air conditioner systems	November, 1990	Proctor et al.
5012652	Crankcase heater control for hermetic refrigerant compressors	May, 1991	Dudley
5035119	Apparatus for monitoring solenoid expansion valve flow rates	July, 1991	Alsenz
5050397	Air conditioner apparatus with starting control for parallel operated compressors based on high pressure detection	September, 1991	Sugiyama et al.
5056036	Computer controlled metering pump	October, 1991	Van Bork
5062278	Air-conditioning apparatus including an indoor unit and an outdoor unit having its compressor driven by a three-phase AC power supply	November, 1991	Sugiyama
5065591	Refrigeration temperature control system	November, 1991	Shaw
5109700	Method and apparatus for analyzing rotating machines	May, 1992	Hicho
5123256	Method of compressor staging for a multi-compressor refrigeration system	June, 1992	Oltman
5128855	Building automation system operating installation control and regulation arrangement	July, 1992	Hilber et al.
5131237	Control arrangement for a refrigeration apparatus	July, 1992	Valbjern
5142877	Multiple type air conditioning system which distributes appropriate amount of refrigerant to a plurality of air conditioning units	September, 1992	Shimizu
5181389	Methods and apparatus for monitoring the operation of a transport refrigeration system	January, 1993	Hanson et al.
5203178	Noise control of air conditioner	April, 1993	Shyu
5224835	Shaft bearing wear detector	July, 1993	Oltman
5231846	Method of compressor staging for multi-compressor multi-circuited refrigeration systems	August, 1993	Goshaw et al.
5249429	Methods of operating a refrigeration system	October, 1993	Hanson
5323385	Serial bus communication method in a refrigeration system	June, 1994	Jurewicz et al.
5327742	Hierarchial control for discrete chiller units	July, 1994	Duff et al.
5362206	Pump control responsive to voltage-current phase angle	November, 1994	Westerman et al.
5381692	Bearing assembly monitoring system	January, 1995	Winslow et al.
5390206	Wireless communication system for air distribution system	February, 1995	Rein et al.
5437163	Method of logging data in a transport refrigeration unit	August, 1995	Jurewicz et al.
5448230	Remote data acquisition and communication system	September, 1995	Schanker et al.
5460006	Monitoring system for food storage device	October, 1995	Torimitsu
5465081	Multicomponent wireless system with periodic shutdown of transmitting and receiving modes	November, 1995	Todd
5499512	Methods and apparatus for converting a manually operable refrigeration unit to remote operation	March, 1996	Jurewicz et al.
5509786	Thermal protector mounting structure for hermetic refrigeration compressors	April, 1996	Mizutani et al.
5515693	Enable system for a controlled atmosphere system for a refrigerated container	May, 1996	Cahill-Obrien et al.
5533347	Method of refrigeration case control	July, 1996	Ott et al.
5561817	Method of securely controlling direct memory access (DMA) of a shared memory by a DMA device on an expansion board	October, 1996	McCormack et al.
5566879	System for centralized controlling of a plurality of temperature regulating devices	October, 1996	Longtin
5577390	Compressor for single or multi-stage operation	November, 1996	Kaido et al.
5586444	Control for commercial refrigeration system	December, 1996	Fung
5592824	Driving control device for air conditioner	January, 1997	Sogabe et al.
5596878	Methods and apparatus for operating a refrigeration unit	January, 1997	Hanson et al.
5598566	Networked facilities management system having a node configured with distributed load management software to manipulate loads controlled by other nodes	January, 1997	Pascucci et al.
5602757	Vibration monitoring system	February, 1997	Haseley et al.
5610339	Method for collecting machine vibration data	March, 1997	Haseley et al.
5626027	Capacity control for multi-stage compressors	May, 1997	Dormer et al.
5630324	Multiple type air conditioner system and address setting method thereof	May, 1997	Yoshida et al.
5634345	Oil monitoring system	June, 1997	Alsenz
5647223	Control device for air conditioner	July, 1997	Wada et al.
5869963	Magnetoresistive sensor and head	November, 1997	Spargo et al.
5701482	Modular array processor architecture having a plurality of interconnected load-balanced parallel processing nodes	December, 1997	Harrison et al.
5707210	Scroll machine with overheating protection	January, 1998	Ramsey et al.
5713724	System and methods for controlling rotary screw compressors	February, 1998	Centers et al.
5763959	Control cabinet for building automation systems	June, 1998	Chambers
5797729	Controlling multiple variable speed compressors	August, 1998	Rafuse et al.
5822739	System and method for remote postage metering	October, 1998	Kara
5825664	Field-mounted control unit	October, 1998	Warrior et al.
5884072	Networked facilities management system with updated data based on aging time	March, 1999	Rasmussen
5940337	Method and apparatus for controlling memory address hold time	August, 1999	Jiang
5950709	Temperature control with stored multiple configuration programs	September, 1999	Krueger et al.
5975854	Compressor with protection module	November, 1999	Culp, III et al.
5984645	Compressor with combined pressure sensor and high pressure relief valve assembly	November, 1999	Cummings
6005424	Integrated power switch for parasitically powered devices	December, 1999	Douglass
6017192	System and method for controlling screw compressors	January, 2000	Clack et al.
6041605	Compressor protection	March, 2000	Heinrichs
6125642	Oil level control system	October, 2000	Seener et al.
6178362	Energy management system and method	January, 2001	Woolard et al.
6185946	System for sequencing chillers in a loop cooling plant and other systems that employ all variable-speed units	February, 2001	Hartman
6276901	Combination sight glass and sump oil level sensor for a hermetic compressor	August, 2001	Farr et al.
6294889	Process and a control device for a motor output suitable for being controlled through a communication bus	September, 2001	Briant et al.
6302654	Compressor with control and protection system	October, 2001	Millet et al.
6332327	Distributed intelligence control for commercial refrigeration	December, 2001	Street et al.
6427461	Space conditioning system with outdoor air and refrigerant heat control of dehumidification of an enclosed space	August, 2002	Whinery et al.
6449715	Process control configuration system for use with a profibus device network	September, 2002	Krivoshein
6533552	System and methods for controlling rotary screw compressors	March, 2003	Centers et al.
6579078	Multi-stage centrifugal compressor driven by integral high speed motor	June, 2003	Hill et al.
6647476	Subsystem replacement method	November, 2003	Nagasawa et al.
6820157	Apparatus, program product and method of replacing failed hardware device through concurrent maintenance operation	November, 2004	Eide et al.
20030037555	Distributed intelligence control for commercial refrigeration	February, 2003	Street et al.
20040016244	Refrigeration system and method of configuring the same	January, 2004	Street et al.
20040016251	Refrigeration system and method of operating the same	January, 2004	Street et al.
20040016253	Refrigeration system and method of operating the same	January, 2004	Street et al.
20040024495	Communication network and method of communicating data on the same	February, 2004	Street et al.
20040144849	Building control system using integrated MEMS devices	July, 2004	Ahmed	236/1E
20040193330	Method and system for controlling compressors	September, 2004	Mehaffey et al.

WO/1998/040800	September, 1998			A MONITORING SYSTEM
WO/1999/017066	April, 1999			AN ADAPTIVE CONTROL FOR A REFRIGERATION SYSTEM USING PULSE WIDTH MODULATED DUTY CYCLE SCROLL COMPRESSOR
WO/1999/024771	May, 1999			DEVICE AND METHOD FOR CONTROLLING THE OPERATION OF DOMESTIC REFRIGERATORS AND FREEZERS
WO/2001/069147	September, 2001			DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION
WO/2002/075227	September, 2002			DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION

AS Interface (ASI) News—“AS-Interface accepted as European Standard”, 1 page, available at http://www.as-interface.com/news/en50295.html on Sep. 23, 1999.
AS Interface (ASI) News—“Technical Enhancements Extend AS-Interface Capabilities”, 2 pages, dated Oct. 28, 1998, available at http://www.as-interface.com/news/en50295.html on Sep. 23, 1999.
Siemens Manual, “Actuator Sensor Interface—System Description”, May 1996, Siemens Aktiengesellschaft, Germany, 63 pages.
Siemens Manual, “Actuator Sensor Interface”, 1999, Siemens Energy & Automation, Inc., Batavia, Illinois, 128 pages.
Echelon Corporation—“Introduction to the LonWorks® System” (Version 1.0), Published by Echelon Corporation, Palo Alto, California, 1999, 74 pages.
Michael R. Tennefoss, “Echelon White Paper: Implementing Open, Interoperable Building Control systems”, Published by Echelon Corporation, Palo Alto, California, 2000, 14 pages.
American Microsystems, Inc., “A2SITM Advanced AS-Interface IC”, Published by American Microsystems, Inc., Pocatello, Idaho, Mar. 2000, 27 pages.
Norman E Street et al., U.S. Appl. No. 11/185,227, filed Jul. 20, 2005.

Norman, Marc E.

Michael Best & Friedrich LLP

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 10/461,202, filed on Jun. 12, 2003, now U.S. Pat. No. 7,047,753 entitled “REFRIGERATION SYSTEM AND METHOD OF OPERATING THE SAME”; which is continuation-in-part of U.S. patent application Ser. No. 09/849,900, filed on May 4, 2001, entitled “DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION”, issued as U.S. Pat. No. 6,647,735; which is a continuation-in-part of International Patent Application No. PCT/US01/08072, filed Mar. 14, 2001, entitled “DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION”; which is a continuation-in-part of U.S. patent application Ser. No. 09/524,939, filed on Mar. 14, 2000, entitled “DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION”, issued as U.S. Pat. No. 6,332,327; all of which are incorporated herein by reference.

What is claimed is:

1. A refrigeration system comprising: an evaporator, compressor, and condenser in fluid communication; a system controller operable to control the refrigeration system; and a compressor controller supported by the compressor, and distinct from and in communication with the system controller, the compressor controller including a digital sensor that senses at least one of a pressure and temperature of the compressor and operable to control the compressor based on the sensed at least one of the pressure and temperature, the digital sensor comprising a housing, a sensing device disposed within the housing, and an analog-to-digital (A/D) converter disposed within the housing and coupled to the sensing device.

2. A refrigeration system as set forth in claim 1 wherein the digital sensor is a dual pressure/temperature sensor.

3. A refrigeration system as set fourth in claim 1 wherein the sensing device generates an analog signal representing a sensed parameter and the (A/D) converter converts the analog signal to a serial digital signal.

4. A refrigeration system comprising: an evaporator, compressor, and condenser in fluid communication; and a controller supported by the compressor and operable to control at least the compressor, the controller including a digital sensor that senses at least one of a pressure and temperature of the compressor, the digital sensor comprising a housing, a sensing device disposed within the housing, and an analog-to-digital (A/D) converter disposed within the housing and coupled to the sensing device.

5. A refrigeration as set forth in claim 3 wherein the digital sensor is a dual pressure/temperature sensor.

6. A refrigeration system as set fourth in claim 3 wherein the sensing device generates an analog signal representing a sensed parameter and the (A/D) converter converts the analog signal to a serial digital signal.

FIELD OF THE INVENTION

The invention relates to sensing the failure of a sensor and, more particularly, sensing the failure of a sensor in a refrigeration system.

BACKGROUND

Electronic control systems applied to refrigeration systems (e.g., a commercial refrigeration system such as can be found at a supermarket) require sensing devices to acquire real-time information about the state of the system. The acquired data is used to determine control actions as well as alarm and failure status. Accuracy of the sensed data is imperative in order to maintain system control. Inaccurate or missing data will result in poor system performance and could potentially cause damage to the system components.

SUMMARY

In one configuration of a refrigeration system embodying the invention, implementation of a distributed control methodology places intelligence at the point of control and/or sensing. Division of the control tasks and distribution of the control/monitoring devices segregates system operating parameters. To regain system wide control and monitoring capability, a communication network (or series of networks) is established among subsystems and monitoring devices. The network(s) provides an infrastructure for the sharing of operating parameters among the control and/or monitoring devices and a system wide master control. In order to reduce the potential impact of a failed sensing device, a method of determining sensor and data integrity is required.

Distribution of controls produces redundant sensing devices to support distributed control functions. Each distributed device supports one or more sensing devices. Sensed data is retrieved filtered and scaled by the attached device. During retrieval and manipulation of the sensed data, the control can test for open, shorted, and non-responding sensors. If such a condition exists the sensor is marked as failed and the data ignored. In some constructions, the failed sensor condition is then reported to the system controller. This alerts the system controller not to use data from the failed sensor and to report the failure.

The aforementioned process helps protect the system controller from operating on data from a failed sensing device. In another construction, further testing and comparison of the sensed data from multiple sensing elements detects data skewed by partial sensor failure or garbled data transmission from the distributed controls. As an example, a refrigeration system with multiple (e.g., four) parallel compressors has multiple (e.g., four) suction pressure sensors (i.e., one attached to each compressor). These sensors, under normal circumstances, will report pressures that deviate only 2-3 PSI sensor to sensor. Continued deviations outside this range are indicative of a failed sensing device. The refrigeration system can mark the offending device as failed and remove from calculations affecting control. The failure is also reported to alert service personnel. The reported message can include an error code.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a refrigeration system.

FIG. 1A is an schematic flow diagram of a second refrigeration system suitable for use in connection with a distributed intelligence control system.

FIG. 2 is a schematic representation of one construction of a bus compatible compressor safety and control module.

FIG. 3 is a schematic representation of a compressor.

FIG. 4 is a flow diagram illustrating an exemplary operation of the control and safety module in a standard operating mode.

FIG. 5 is a flow diagram illustrating an exemplary operation of the control and safety module in a master controller failure mode.

FIG. 6 is a schematic representation of aspects of a solid state relay device.

FIG. 7 is a system block diagram illustrative of aspects of a commercial refrigeration system.

FIG. 8 is a block diagram illustrating aspects of a partially wireless configuration of the commercial refrigeration system of FIG. 7.

FIG. 9 is a block diagram of a bus compatible branch control subsystem, suitable for use with the commercial refrigeration system of FIGS. 7 and 8.

FIG. 10 is a block diagram of a commercial refrigeration system including bus compatible valve control.

FIG. 10A is a block diagram of an exemplary construction of the system of FIG. 10 using valve controller to control an evaporator valve associated with a subcooler.

FIG. 11 is a block diagram that illustrates a system using modular case control modules to provide monitoring and control functions for a plurality of refrigeration display cases.

FIG. 12 is a block diagram that illustrates the use of a modular case controller configured for display case monitoring.

FIG. 13 is a block diagram that illustrates the use of a modular case controller to provide branch control for a plurality of display cases configured in a refrigeration branch.

FIG. 14 is a block diagram illustrating the reduced wiring requirements associated with using a distributed intelligence refrigeration control system.

FIG. 15 is a schematic representation of a second construction of a bus compatible compressor safety and control module.

FIG. 16A-16F are flowcharts representing one method of dynamically controlling a plurality of multiplexed compressors.

FIG. 17 is a table representing parameters identified as rack parameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 18 is a table representing parameters identified as suction group parameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 19 is a table representing parameters identified as system data parameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 20 is a table representing parameters identified as suction group parameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 21 is a table representing parameters identified as condenser parameters, which are communicated to and from the rack PLC in FIG. 7.

FIGS. 22A, 22 B, 22 C, and 22 D are schematic representations of a 256-bit memory coupled to the microprocessor 1505 in FIG. 15.

FIG. 23 is a flowchart of a read sequence for one method of communication between the master controller 70 and the BCCSCM 1500 .

FIG. 24 is a flowchart of a write sequence for one method of communication between the master controller 70 and the BCCSCM 1500 .

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “coupled” and “communication” and variations thereof herein are used broadly and encompass both direct and indirect mountings, connections, couplings and communications. Further, “connected,” “coupled,” and “communication” are not restricted to physical or mechanical connections, couplings, or communications.

Referring now to FIG. 1, one construction of a refrigeration system (e.g., a commercial refrigeration system for use in a food store) is shown to comprise one or more fixtures (which are illustrated as food display merchandisers 10 A and 10 B in the shopping arena of a food store). The merchandisers 10 A and 10 B each incorporate at least one evaporator coil 12 A and 12 B (or like heat exchanger unit), respectively, disposed for cooling the merchandiser. Three multiplexed compressors (designated 14 A, 14 B, and 14 C, respectively) are connected by way of a suction header 16 and a low side return pipe 18 in fluid communication with the low side of the evaporators 12 A and 12 B for drawing refrigerant away from the evaporators. A condenser (generally indicated at 20 ) including a fan 22 and heat exchanger 24 is in fluid communication on the high discharge side of the compressors 14 A, 14 B, 14 C for removing heat and condensing refrigerant pressurized by the compressors. Although an air-cooled condenser 20 is shown, other types of condensers, such as those liquid cooled from a ground source water supply, may be used. Moreover, it is to be understood that the single illustrated fan 22 represents one or more fans typically used in a condenser for commercial refrigeration applications.

Refrigerant from the condenser 20 is stored in a receiver 26 in communication with expansion valves 28 A and 28 B by way of a high side liquid delivery line 30 . The expansion valves 28 A and 28 B meter refrigerant into respective evaporators 12 A and 12 B and induce a pressure drop for absorbing heat, to complete the refrigeration circuit. The compressors 14 A, 14 B, and 14 C, and usually also the suction header 16 and receiver 26 , are mounted on a compressor (or condensing unit) rack (not shown) prior to shipment to the store location where the refrigeration system is to be installed.

The food display merchandisers 10 A and 10 B illustrated with the evaporators 12 A and 12 B can be placed in the shopping arena of a food store. However, it is understood that other types of cooling fixtures could be placed in other parts of the store (e.g., a service area or backroom cooler). The liquid line 30 and suction return line 18 have been broken to indicate connection to other evaporators (not shown) in the system. Evaporators may be connected to the same piping circuit between the receiver 26 and the suction header 16 , or in a different circuit or “branch” (not shown) connected to the receiver. Further, the number of compressors 14 in the refrigeration system can be more or less than three (including only a single compressor). The refrigeration system typically includes a compressor, a condenser, an expansion valve and an evaporator. Other components can be included but are not essential, and the precise mounting or location of the system components may be other than described. Moreover, the same aspects of the refrigeration system have application outside the food store environment; for example, the invention can be used with cooling other perishable, non-food products such as blood, plasma and medical supplies. Also, some aspects of the communications network (discussed below) have application in other systems.

As shown in FIG. 3 and in one construction, each compressor 14 A, 14 B, and 14 C comprises an electric motor 32 driving a shaft 34 connected to a pressurizing unit 36 . For purposes of the description herein, compressor 14 A will be referred to; the other compressors 14 B and 14 C preferably having the same construction. The pressurizing unit may take on any suitable form. In one construction, reciprocating pistons driven by a motor constitute the pressurizing device, but more and more, the quieter rotary devices found in scroll compressors and screw compressors are being employed to compress the vaporous refrigerant. A scroll compressor is illustrated in FIG. 3. The compressor 14 A has a low side suction inlet 38 that receives the vaporous refrigerant from the evaporators 12 A and 12 B and a high side discharge outlet 40 through which hot, pressurized refrigerant is discharged from the compressor. In one construction, the motor 32 and pressurizing unit 36 are semi-hermetically or hermetically sealed within an outer casing or shell 42 . The motors 32 of the compressors are each connected to a respective high voltage (e.g., three phase 480 V AC or 208 V AC) power line 44 A, 44 B, and 44 C (FIG. 1) extending from a power distribution center 46 within the food store. These lines are shielded, such as by placement within a conduit, as may be required by electrical codes.

In one construction, the compressors 14 A, 14 B, and 14 C each have a bus compatible compressor safety and control module 48 (also referred to as “BCCSCM,” “compressor operating unit, “compressor control module,” or “compressor controller”) for monitoring at least one, but preferably several operating conditions or parameters of the compressor. The “operating parameters,” in one construction, include (1) control parameters providing information used for controlling the compressor 14 , and (2) safety parameters providing information about whether the compressor 14 is operating within its designed operational envelope or in a manner which could damage the compressor 14 . It is envisioned that any number of parameters could be monitored, including only safety parameters or, less likely, only control parameters. Control parameters for the compressor 14 may include, but not limited to, suction temperature, suction pressure, and discharge pressure. Safety parameters for the compressor 14 can include, but not limited to, discharge pressure, discharge temperature, oil level (or pressure), phase loss/reversal, and motor winding temperature. As is apparent, some of the control parameters are also classified as safety parameters.

The bus compatible compressor safety and control module (“BCCSCM”) 48 is constructed and arranged to receive and/or detect the various operating parameters and control operation of the compressor. In one construction, the BCCSCM comprises a processor 49 and multiple sensors in communication with the processor 49 . In the illustrated construction of FIG. 3, the compressor 14 A is built with individual continuous reading analog sensors including a discharge pressure sensor 50 , a discharge temperature sensor 52 , a suction pressure sensor 54 , a suction temperature sensor 56 , and a motor winding temperature sensor 58 (FIG. 3). In one construction, the temperature sensors 52 , 56 and 58 are variable resistance, RTD-type sensors. An oil level sensor 60 can be of the type that changes the state of a circuit when the oil level falls below a predetermined minimum, and does not provide a continuous reading of the oil level. A power phase monitoring device 62 incorporated into the BCCSCM 48 is capable of detecting both phase loss and phase reversal on the three phase power line 44 A coming into the compressor 14 A. It is to be understood that other sensors can be used (e.g., digital sensors as discussed below).

In one construction of the commercial refrigeration system, the sensors 50 - 62 are installed at the compressor assembly site and disposed within the hermetically (or semi-hermetically) sealed shell 42 of the compressor (FIG. 3). This construction allows the sensors 50 - 62 to be protected in the shell 42 and, particularly in the case of the suction pressure sensor 54 , are located close to the pressurizing unit 36 for more accurate readings of compressor function. However, it is to be understood that the sensors 50 - 62 could be located other than in the shell 42 . For instance, it is envisioned that sensors could be replaceably received in openings 59 in the shell (schematically illustrated in phantom in FIG. 3) accessible from the exterior, or external to the compressor shell as in the case of a reciprocating semi-hermetic compressor, or any other motor driven compression device.

The processor 49 of the BCCSCM 48 , in one construction, is a dual processor system, including a host controller (such as a microcontroller, an ASIC, or a microprocessor, any of which may be connected to a memory) and a communication slave controller. The host controller and communication slave are not separately represented in FIG. 2, but are collectively represented as the processor 49 . In one construction, the host controller has a 256 byte internal RAM, 8 kilobytes of flash program memory, and 16 input/output pins for control interface. The communication slave, in one construction, is an application specific integrated circuit (ASIC) that communicates with the field bus network (described in one construction below as AS-Interface® network). The communication slave translates the protocol of the field network into a signal understood by the host controller, and vice versa.

For an exemplary construction of the communication slave, if the field bus network provides four data bits per message, the communication slave can be configured to extend the data capabilities of the field bus network by interfacing with an intermediate memory device (an additional RAM) between the communication slave and the host controller. In such a construction, the communication slave and the host controller interface with the RAM to extend the data capabilities of the field bus network by using sequential read or write cycles of the field bus network to build larger data sizes. In other words, rather than limiting the data sizes to four bits, larger data sizes are constructed by grouping multiple four-bit data transmissions. The communication slave sequentially writes the data into (or reads the data from) the additional RAM. The host microcontroller reads the data from or writes the data to the additional RAM. Thus, for example, a sixteen-bit data parameter may be constructed over the course four successive data cycles.

Alternative structures of the BCCSCM can also be employed. For example and as shown in FIG. 15, the BCCSCM 1500 includes a microprocessor 1505 , RAM 1510 , and program memory 1515 . The BCCSCM 1500 also includes a communication slave 1520 , a suction sensor 1525 , a discharge sensor 1520 , an oil sensor 1535 , a current sensor 1540 , and a voltage sensor 1545 . The BCCSCM 1500 also further communicates with the compressor 14 to receive switched contact input from a high-pressure cut out 1550 and oil level sensor 1555 and communicates with a compressor on/off control 1560 .

In other constructions of the refrigeration system, a field bus protocol having larger inherent data sizes could be accommodated, thereby potentially eliminating the need for a communication slave to translate the protocol. In yet another construction, the communication slave and the host controller (or microprocessor 1505 ) are combined as single controller (e.g., a single ASIC) or as a single microprocessor and memory. Unless specified otherwise, when referring to the construction shown in FIG. 2, the description also applies to the construction shown in FIG. 15.

The host controller (e.g., microprocessor 1505 ) is adapted to receive signals from the sensors indicative of the values of the sensed operating parameters. The host controller also stores safety limit values for the measured safety parameters, respectively. The host controller is capable of generating digital status information indicative of the values of the operating parameters. When a safety limit is traversed, the host controller is capable of generating a digital status information signal including specific information as to which safety parameter is out of specification. The signals are translated by the communication slave for sending over the field bus network. This will be discussed in further detail below.

In one construction, the BCCSCM 48 for each compressor 14 further includes a switch device 64 . The switch device 64 , in one construction, is a three pole solid state relay such as SSRD Series panel mount heavy duty solid state AC relay. The SSRD Series is made by Teledyne, Inc. of Los Angeles, Calif. and available from Allied Electronics of O'Fallon, Mo. The relay operates, upon receiving a command from the processor 49 (or processor 1503 ), to block at least two of the three phases of the electrical power to the compressor motor 32 , thereby turning the motor off. It is to be understood that other switch devices can be used. The processor 49 is programmed to cause the relays to turn off the compressor ( 14 ) when a safety limit value of one of the safety parameters is traversed.

In another embodiment, the SSRD is constructed to include an overcurrent protection capability. A current sensor (shown as current sensor 1540 in the BCCSCM 1500 ), which can be associated with the switch device, monitors the current through the SSRD. If the sensed current exceeds a threshold (e.g., 350 A for 1.5 line cycles), the SSRD is shut off (rendered non-conducting) to protect the compressor motor 32 . Such an overcurrent condition can occur, for example, if the rotor of the compressor motor 32 locks. Thus, a current sensor associated with the SSRD serves as a locked rotor detector. The sensed current information may also be used to detect other compressor abnormalities.

A current sensor that is a self-contained part of the compressor-controlling device provides certain benefits. For example, current information is available on the system control bus via the BCCSCM for use in safety and control applications, and the value of the current can be used for energy management/monitoring functions. The current sensor may be constructed internal to the SSRD, or it may be a sensor external to the SSRD. For example, a current sensing toroid could be used external to the SSRD to sense current. Alternatively, a high power, current sensing resistor may be included within the SSRD to sense current.

FIG. 6 is a schematic representation of another aspect of an SSRD. A typical commercial refrigeration compressor system uses three-phase electrical power. Thus, by controlling the SSRD, the application of phases A, B, and C of such a three-phase power system is also controlled.

As illustrated in the construction of FIG. 6, the SSRD includes three opto-isolators 102 , 104 , and 106 that are constructed as an integral component of the overall SSRD assembly. Opto-isolator 102 is associated with phase A, opto-isolator 104 is associated with phase B, and opto-isolator 106 is associated with phase C. The opto-isolators 102 , 104 , and 106 detect the zero-crossing of the respective phases with which they are associated. Thus, when phase A crosses zero, opto-isolator 102 produces an output, via its collector, on line 108 . Likewise, when phase B crosses zero, opto-isolator 104 produces an output on line 110 . Similarly, when phase C crosses zero, opto-isolator 106 produces an output on line 112 . As one skilled in the art can appreciate from the foregoing, such zero-crossing information amounts to phase reference information, which may be compared to determine the relationship between the power phases.

As those skilled in the art will also appreciate, if power is applied to the compressor motor 32 when an improper phase relationship exists, the compressor motor 32 may be damaged or destroyed. For example, if a scroll compressor is run backwards, for even an instant, because of an improper phase relationship, the compressor may be seriously damaged or ruined. The zero-crossing detection capability of the SSRD shown in FIG. 6 is integral to the SSRD and available when the SSRD is open-circuited—when it is non-conducting and no power is applied to the compressor motor 32 . Hence, a BCCSCM with the SSRD shown in FIG. 6 can monitor the phases for a proper polarity relationship before applying power to the compressor motor 32 . Stated differently, a BCCSCM with the SSRD shown in FIG. 6 can determine the presence of an improper phase relationship by comparing the phase information to an acceptability standard and prevent potential damage to the compressor motor 32 that would otherwise occur if power were applied to the motor. In contrast, prior art phase polarity detection schemes rely on devices external to the SSRD. Such prior art schemes do not detect an improper phase relationship before applying power. Rather, such systems check the phase relationship only after power application. In such systems, if an improper phase relationship is detected, power is removed. As those skilled in the art can appreciate, the compressor motor 32 may be damaged or destroyed before power is removed, even if it is removed relatively rapidly. Thus, the SSRD, as shown in FIG. 6 (and as shown as 1560 in FIG. 15), provides for phase detection prior to the application of power.

Referring again to FIG. 1, a master controller 70 (also referred to as a system controller) for controlling all of the compressors 14 A, 14 B, and 14 C of the refrigeration system is in electronic communication with all of the BCCSCMs 48 of the refrigeration system via line 80 . In one construction, the controller 70 includes a CPU 72 (or simply a processing unit) which coordinates data transfer among the components of the system. The CPU 72 also processes data acquired from the BCCSCMs 48 and determines control commands to be sent to the BCCSCMs. Other logic devices can be used in place of the CPU 72 to perform the function of the CPU 72 .

In one specific construction, the CPU 72 includes a 16-bit RISC processor, has 64 kilobytes of read only memory (ROM), 16 kilobytes of random access memory (RAM), a real time clock to perform time-based control functions, and at least two interfaces (e.g., serial interfaces) to permit connection to a local human-machine interface (hereinafter, “HMI”), as well as a remote interface. The local and remote interfaces may also be referred to herein as input/output devices. The CPU 72 can also include both digital and analog inputs and outputs, and is powered by a 24-VDC power supply 74 transformed and rectified from a 120-VAC feed line 69 .

The controller 70 further includes a communications module 76 to permit the CPU 72 to work with a field bus networking system. The field bus networking system is designed to connect sensors, actuators, and other control equipment (e.g., BCCSCM 48 ) at the field level. An example of a suitable field bus networking system is the AS-Interface® (or AS-i) networking system. Components for the AS-i network are sold commercially by Siemens Aktiengesellschaft of Germany, and available in the United States from Siemens Energy Automation and Control, Inc. of Batavia, Ill. The communications module 76 can be powered by the same 24-VDC power supply 74 used by the CPU 72 .

In one construction, the controller 70 includes a network power supply 78 , which provides a 24-VDC to 30 VDC power supply connected to the 120-VAC feed line 69 . The network power supply 78 provides power to the field bus network via line 79 as further discussed below.

In one construction, the field bus network includes an unshielded two wire bus 80 connecting the communications module 76 (and hence the CPU 72 ) to all of the BCCSCMs (and, as discussed below, other control modules). One wire is a ground wire and the other is a communication and power line which carries all communication and power for the BCCSCMs 48 . Power for the BCCSCMs is supplied from the network power supply 78 through line 79 , which has a communications decoupling feature allowing communications and power to be supplied over the same line. The BCCSCMs 48 are each connected to the bus 80 at nodes 82 by a respective coupling that penetrates insulation of the bus cable and makes contact with the wires. Each BCCSCM 48 is plugged into the coupling to connect the control and safety module to the network.

In the construction shown in FIG. 1, the master controller 70 also controls cycling of the condenser fans 22 . For example, the master controller 70 can monitor discharge pressure and liquid refrigerant temperature to determine when to cycle the condenser fans 22 . Similarly, the master controller 70 can monitor discharge pressure and outdoor ambient temperature to determine whether to split the condenser.

In the illustrated construction, the master controller 70 transmits these cycling commands from the CPU 72 to a condenser controller 84 located close to the fans 22 . The condenser controller 84 executes the commands for shutting down or energizing the condenser fans 22 . Because the condenser is, in some constructions, located remotely from the compressor rack, it may be undesirable or impractical to locate the condenser controller 84 on the same field network bus (e.g., AS-i bus) as the CPU 72 . FIG. 1 illustrates such a situation, in which the condenser controller 84 has its own field bus network (e.g., another AS-i bus 85 ). In other words, the condenser controller 84 can have its own field bus network for controlling the condenser fans, just like the network of the compressors 14 A, 14 B, and 14 C with the master controller 70 . For example, the CPU 72 can communicate with the condenser controller 84 over a relatively longer distance network. The Multipoint Interface or “MPI”, available from Siemens, is an example of such a longer distance network/field bus. Another example is the ProfiBUS standard. In this way, the condenser controller 84 acts as a gateway to extend the range of the master controller 70 in a situation in which the primary field bus network associated with the compressor rack could not practically be used. Thus, the master controller 70 provides operating and control functions to the condenser controller 84 . The condenser controller 84 , via its own field bus network 85 , supplies the control information to a BCFCM 86 which drives the fans 22 . Likewise, data available at the condenser (e.g., an ambient air temperature associated with the condenser and information regarding which fan(s) is/are on) may be transmitted to the master controller 70 . In one construction, an air temperature sensor provides ambient air temperature data directly to the condenser controller 84 (i.e., independently of any field bus network), which transmits such data to the master controller 70 .

Advantageously, if the master controller 70 ceases communications with the condenser controller 84 , the condenser controller is preferably programmed to independently determine and provide at least some of the control information required to drive the fans 22 via the BCFCM. Other condenser control arrangements may be used. For instance, the condenser controller 84 could be eliminated and its functions programmed into the master controller.

The BCFCM 84 includes, in one construction, a communication slave controller and a microprocessor and memory as described in connection with the BCCSCM 1500 of FIG. 15. However, the BCFCM would include different inputs and outputs connected to the microprocessor of the BCFCM than the microprocessor 1505 . In other words, the inputs and outputs connected to the microprocessor of the BCFCM would be the inputs and outputs associated with the condenser 20 .

Referring now to FIG. 4, in one operation of the refrigeration system, the sensors 50 - 62 or 1525 - 1545 of each BCCSCM 48 or 1505 (e.g., the BCCSCM associated with compressor 14 A) provide information regarding the operating parameters monitored by the sensors. The information provided by the sensors 50 - 62 or 1525 - 1545 could be limited to whether or not a pre-set safety limit value has been traversed. However, in one construction, at least some of the sensors provide signals to the processor of each BCCSCM 48 or 1500 indicative of the actual value of the operating parameter at the time sampled.

In one construction, the sensors for discharge pressure 50 and temperature 52 , and suction pressure 54 and temperature 56 provide digital signals to the processor 49 indicative of the actual value of the parameter measured. Thus, the sensor/transducer converts the analog data to a digital format before providing the information to the processor 49 .

In the construction shown in FIG. 15, the sensors 1525 , 1530 , and 1535 are dual function pressure/temperature sensors having an addressable, 14 bit analog to digital converter. That is, each sensor includes a first sensing device (e.g., thermistor) that senses a temperature and a second sensing device (e.g., a strain gauge) that senses a pressure. Both the first and second sensing devices are disposed within a single housing. The A/D converter is also located within the sensor housing and converts the analog signals from the detecting devices to a single digital signal conveying the measured parameters. The A/D converter can include other channels (e.g., a channel for monitoring the supply voltage to the sensors), and the digital signal can convey information relating to the other channels. Additionally, the digital signal can send an error code to the processor 1503 when an error code occurs at the sensor. For example, if the A/D converter does not receive a signal from the temperature sensing device, it can generate an error code that is communicated to the processor 1503 . The processor 1503 can then communicate to the system controller that a sensor error has occurred. An example dual function pressure/temperature sensor is a ML 200 psis per SCD1126, part no. 9310101, manufactured by Honeywell.

The motor winding temperature sensor 58 , and the current and voltage sensors 1540 and 1545 provide an analog signal to the processor 1505 indicative of the actual value of the parameter measured. The oil level sensor 60 (or 1555 ) provides a circuit open or circuit-closed signal to the processor indicative of whether an oil level safety limit has been traversed. The high pressure cut out 1550 provides a circuit open or circuit-closed signal to the processor indicative of whether a pressure limit has been traversed.

As explained above with respect to FIG. 6, phase loss or phase reversal can be monitored/detected by monitoring the zero crossings of each phase with a plurality of opto-isolator devices. An alternative, separate power phase monitoring device 62 may also be used. Such a separate power phase monitoring device 62 would, for example, provide a circuit open or a circuit closed signal to the microcontroller to indicate whether a phase loss or phase reversal has occurred.

The processor 49 or 1503 of each BCCSCM 48 or 1500 checks the inputs from each sensor to determine whether a safety limit value for any of the measured compressor characteristics has been exceeded. If no safety limit values are exceeded, the processor 49 loads the sensor data for transmission to the master controller 70 when the processor is queried. The master controller 70 is the system network controller in standard operation of the refrigeration system shown in FIG. 1. In the illustrated embodiments, the host controller (or the microprocessor 1505 ) stacks the information to await transmission to the master controller 70 . The processor 49 (or 1503 ) then waits for a message from the master controller 70 containing commands and a query for the sensor data. As soon as the message is received, the processor 49 responds over the communication and power line of the two-wire bus 80 to the controller 70 with the information data stored from the sensors 50 - 62 .

For the construction shown in FIG. 1, data from all of the processors flows in a stream over the communication and power line of the bus 80 to the communication module 76 and thence to the CPU 72 of the master controller 70 . The communication protocol allows the CPU 72 to associate the operating parameter information received with particular compressors, and to discriminate between different operating parameters for each compressor. In one construction, more specifically, each BCCSCM is assigned a particular address, which allows the controller 70 to communicate individually with each of the BCCSCMs over the same line, and also allows the BCCSCM processors to identify themselves to the master controller.

The data is now available through interfacing with the master controller 70 , either remotely or by a local human machine interface, to view individual compressor data. The processor 49 (or 1503 ) also looks for the command portion of the master controller 70 message for a command to turn the compressor ( 14 A, 14 B, or 14 C) on or off. If such a command is present, the processor 49 executes it by operating the solid state relay (switch device 64 ) to turn the compressor on or off. However, if the command is to turn the compressor on, the processor 49 will not execute it if the processor 49 has previously determined that a safety limit value of one of the safety parameters has been traversed and remains in a safety exception state. It is envisioned that other capacity control commands could be received and executed by the processor 49 such as when the compressor was of a variable capacity type. The software of the processor then returns to the initial step of reading the sensor inputs.

Before proceeding further, another method of communication between the master controller 70 and the BCCSCM 1500 (or 48 ) will now be discussed. The method below will be described for the master controller 70 in communication with the BCCSCM 1500 via an AS-i cable (i.e., bus80); however, other networks can utilize the method below. For example, other networks that do not utilize an AS-i bus can implement the method.

The communication slave 1520 shown in FIG. 15 is an AS-i compatible ASIC that is in communication with the communication module 76 (referred to below as the master). The communication module 76 is or includes an AS-i compatible ASIC. The communication slave 1520 is in further communication with the microprocessor 1505 . More specifically, the communication slave 1520 and the microprocessor 1505 are electrically coupled by four “control” (or “parameter”) channels P 0 , P 1 , P 2 , and P 3 ; four “output” channels DO 0 , DO 1 , DO 2 , and DO 3 ; four “input” channels DI 0 , DI 1 , DI 2 , and DI 3 ; a DSR channel; and a PST channel. Each channel P 0 , P 1 , P 2 , P 3 , DO 0 , DO 1 , DO 2 , DO 3 , DI 0 , DI 1 , DI 2 , DI 3 , DSR, and PST is coupled to the communication slave 1520 at a respective terminal. Other configurations can be utilized for the communication method described below. For example, the method is not limited to four “input” or four “output” channels. Additionally, other devices can be used in place of the master ASIC, slave ASIC, and the microprocessor.

The AS-i networking solution was originally designed to control four actuators (relays, solenoids, etc.) and/or read four switched inputs. To control the four actuators, the AS-i master transmits requests via the two-wire interface, which also carries the 30 VDC power, to the AS-i slave. In response to the master requests, the AS-i slave either switches its outputs to the state directed by the AS-i master or responds to the master with the current state of its inputs. In accordance with this communication activity, four data bits representing the desired output state or current input state are transmitted during each master-request/slave-response communication cycle. The AS-i slave can also use parameter bits to define or control operation of the attached slave (e.g., to logically AND or OR with the other inputs/outputs). A data exchange with the AS-i slave causes the data strobe output DSR to pulse, while a parameter write to the AS-i slave causes the parameter strobe PST to pulse.

For communication between the communication module 76 and the BCCSCM 1500 , a redefinition of the use of the inputs and outputs of the slave 1520 allows the slave 1520 to be connected to a microprocessor as a communication gateway via the AS-I bus. When coupled in this fashion, the slave/microprocessor 1520 / 1505 combination creates an AS-i bus accessible slave device capable of communicating variable length data elements from an addressable array of bytes. Further, by defining some of the available addressable bytes as pointers into the microprocessor memory space, additional data space is available for transmission over the AS-i bus.

The AS-i protocol calls for communication between the AS-i master and AS-i slave to be in four-bit data packets. That is, each request or response across the AS-i bus includes a wholly self-contained message of four-bits. Please note, however, each request and response can include other bits (e.g., addressing bits, parity bit(s), etc.) for communication between devices on the network.

Generally speaking, a master request controls the output states of the output terminals P 0 -P 3 or DO 0 -DO 3 and the AS-i slave 1520 responds by including the states of the inputs DI 0 and DI 3 . The control (or parameter) bits P 0 -P 4 provide additional information to the microprocessor. The P 0 and P 1 bits are data block selection bits (discussed below), the P 2 bit is a read/write selection bit, and the P 3 bit is a compressor ON/OFF bit. The microprocessor 1505 monitors activity on the communication channels with the slave 1520 and controls the inputs to the slave 1520 .

The microprocessor is coupled to a 256-bit memory. The 256-bit memory is divided into four, eight-byte blocks. When writing to or obtaining data from the 256-bit memory, the P 0 and P 1 bits select one of the blocks. Therefore, the number of blocks (2 ^(m) blocks) can vary if the number of selection bits (m) varies. FIGS. 22A, 22 B, 22 C, and 22 D represent one configuration for the four blocks 2210 , 2220 , 2230 , and 2240 .

Each block is further divided into sixteen sub-blocks. For the construction shown in FIGS. 22A-22D, each sub-block includes four-bits (or a nibble). The size of each sub-block (e.g., (n) bits) is equal to the number of input/output channels (e.g., (n) channels). The total number of sub-blocks in a block is equal to 2 ⁽ⁿ⁾ , and a binary number from 0 (e.g., 0000) to 2 ⁽ⁿ⁾ (e.g., 1111) identifies each sub-block. However, other configurations are possible.

Referring to FIGS. 22A-22D, each sub-block contains one or more pieces of information (e.g., one or more parameters), one or more sub-blocks can be combined to form a piece of information (e.g., form a parameter), one or more sub-blocks can be used as a pointer, or a sub-block can be unused. For example, block 2240 uses sixteen nibbles for storing six parameter values. More specifically, nibbles 0000 and 0001 (byte 0 ) represent a value for the “suction pressure cut in” parameter; nibbles 0010 and 0011 (byte 1 ) represent a value for the “suction pressure cut out” parameter; nibbles 0100 and 0101 (byte 2 ) represent a value for the “split suction assignment” parameter; nibbles 0110, 0111, 1000, and 1001 (bytes 3 and 4 ) represent a value for the “discharge pressure limit” parameter; nibbles 1010, 1011, 1100, and 1101 (byte 5 and 6 ) represent a value for the “discharge temperature limit” parameter; and nibbles 1110 and 1111 (byte 7 ) represent a value for the “oil pressure limit” parameter. As another example, nibbles 1110 and 1111 (byte 7 ) of block 2210 include values for eight parameters. As yet another example, nibbles 1110 and 1101 (byte 6 ) of block 2220 is unused in the configuration shown.

In the construction shown in FIG. 22, bytes 0 and 1 of block 2230 include a 16-bit pointer. The 16-bit pointer points to data stored in RAM 1510 . The resulting value corresponding to the pointer is stored in bytes 2 and 3 of block 2230 . By using the pointer, additional storage capabilities can by used at the processor 1503 . Other pointers, pointer sizes, and data sizes can be used. Also, it should be noted, that the data blocks 2210 to 2250 are mirrored at the master controller 70 .

Because there is only a four-bit control architecture, the network uses an operation sequence for reading and writing data of particular length. FIG. 23 includes a flow diagram representing a read sequence. At 2300 , the AS-i master issues a “write_parameter” message to the AS-i slave 1520 . The “write_parameter” message includes a two-bit value for selecting a data block, a one-bit value for informing the processor 1503 a read operation is beginning, and a one-bit value for the current compressor state. The “write_parameter” message is then communicated from the communication slave 1520 to microprocessor 1505 on channels P 0 -P 3 .

At block 2305 , the master issues a “data_exchange” message to the slave 1520 . The “data_exchange” message includes a four-bit value pointing to one of the sixteen nibbles of the selected block. The “write_parameter” message is then communicated from the communication slave 1520 to the microprocessor 1505 on channels DO 0 to DO 3 .

At block 2310 , the microprocessor 1505 responds by obtaining the stored bits of the identified nibble, and communicating the obtained bits to the slave 1520 on channels DI 0 to DI 3 . The slave then communicates the obtained nibble to the master in the next state change. At block 2320 , the master controller 70 stores the obtained nibble in its mirrored 256-bit storage.

At block 2325 , the master controller determines whether all nibbles for the requested parameter have been obtained. If the result is affirmative, the master controller combines the stored nibbles (or divided if the parameter is less than a nibble), resulting in the requested parameter value. If the result is not affirmative, then the network repeats blocks 2305 , 2310 , 2320 and 2325 . Therefore, the network decomposes, transmits, and composes variable length data in four-bit packets.

FIG. 24 includes a flow diagram representing a write sequence. At 2400 the master controller decomposes a message to be communicated to the microprocessor 1505 into a plurality of nibbles (or creates a nibble if a message is less than a nibble). At 2403 , the AS-i master issues a “write_parameter” message to the AS-i slave, which is then communicated to the microprocessor 1505 on channels P 0 -P 3 . The “write_parameter” includes a two-bit value for selecting a data block, a one-bit value for informing the processor 1503 a write operation is beginning, and a one-bit value for the current compressor state.

At block 2405 , the AS-i master issues a “data_exchange” message to the AS-i slave 1520 , which is then communicated to the microprocessor 1505 on channels DO 0 to DO 3 . The “data_exchange” message includes a four-bit value pointing to one of the sixteen nibbles of the selected block. The slave responds with a dummy value, which is ignored (block 2405 ).

At block 2410 , the AS-i master issues a second “data_exchange” message to the AS-i slave 1520 , which is then communicated to the microprocessor 1505 on channels DO 0 to DO 3 . The second “data_exchange” message includes a four-bit value that is written to the selected nibble. The slave responds with a dummy value, which is ignored (block 2418 ). At block 2420 , the master controller determines whether all nibbles for the requested parameter have been communicated. If the result is affirmative, the master controller exits the write routine. If the result is not affirmative, then the network repeats blocks 2405 , 2408 , 2415 , 2418 and 2420 . Therefore, the network decomposes, transmits, and writes variable length data in four-bit packets.

Referring again to the constructions shown in FIGS. 1, 2 , and 15 , when one or more of the inputs from the sensors 50 - 62 (or 1525 - 1555 ) to the processor 49 (or 1503 ) traverses a safety limit value, the processor 49 , for these constructions, loads a safety exception message for the master controller 70 and immediately shuts down the compressor (e.g., compressor 14 B). The safety exception message is loaded into the top of the stack of information to be sent to the master controller. When the processor 49 receives a message from the master controller 70 , it responds by including the safety exception message for the master controller. The master controller 70 knows not only that one of the safety limit values for a particular compressor was traversed, but which safety parameter or parameters were traversed and in most instances the actual values of those parameters. An alarm can be activated by the master controller 70 to alert the appropriate persons that a problem exists. The information can be accessed by a technician via a suitable HMI in the system (located, for example, at the controller 70 ), or remotely such as through an Internet connection. The information regarding the operating parameters of the properly functioning compressors (e.g., 14 A, 14 C) can also be accessed in this manner.

In some constructions, the BCCSCM 1503 (or 48 ) includes digital sensors. If a sensor is a digital sensor, the digital sensor can communicate a code indicating a fault has occurred at the sensor. Alternatively, the digital value or voltage received from the sensor can indicate faulty wiring (e.g., an open or short circuit) or a faulty transducer. Similar to what was discussed above, the processor 1503 (or 49 ) can load a message for the master controller 70 informing the controller of the sensor error. The message is loaded into the top of the stack of information to be sent to the master controller 90 . When the processor 1503 receives a message from the master controller 70 , it responds by including the message for the master controller. An alarm can be activated by the master controller 70 to alert the appropriate persons that a problem exists. Other control modules (discussed below) can operate similarly.

In some constructions, the compressor having a faulty sensor may continue to operate. For example, in one construction, each BCCSCM 1500 includes sensors that sense, among other things, suction pressure. Theoretically, the suction pressure for each compressor 14 attached to the same suction header should have the same pressure (but practically, may slightly differ due to filters and pipe length). If one of the compressors (e.g., compressor 14 A) has a faulty suction pressure sensor, the master controller 70 can use the sensed suction pressure of the other compressors (e.g., 14 B and/or 14 C) attached to the same suction header (e.g., suction header 16 ) as the compressor (e.g., 14 A) having the faulty sensor to control that compressor (e.g., 14 A). Alternatively, the system can include a pressure sensor coupled to the suction header 16 (or piping in communication with the suction header) to control operation of a compressor having a faulty sensor. In addition to using the redundant value at the master controller 70 , the master controller can communicate the redundant value to the BCCSCM having the faulty suction pressure sensor. Therefore, the refrigeration system can use the redundancy of the attached sensing devices to continue operation of a compressor (or other subsystem) having a faulty sensor, even though the compressor (or other subsystem) includes the faulty sensor.

Before proceeding further, it should be noted that, although the failed sensor was a sensor that measures suction pressure, the system can perform similarly for other sensors (e.g., suction temperature, discharge pressure, discharge temperature, etc.) and for other sensors attached to other control modules (discussed below). Additionally, the master controller 70 can compare values acquired from sensors that should have similar or substantially similar values to determine whether one of the sensors is faulty (e.g., a faulty sensor due to drift). Continuing the above example, the master controller 70 can compare the sensed suction pressure for compressors 14 A, 14 B, and 14 C. If one of the sensed values (e.g., the suction pressure for compressor 14 A) is significantly different than the values of the other compressors (or different than a sensor attached to the suction header 16 ), then the master controller 70 can mark the suction pressure sensor having the significantly different value as faulty. An alarm can be activated by the master controller 70 to alert the appropriate persons that a problem exists. Additionally, the master controller can communicate the fault to the compressor having the faulty sensor.

As discussed herein, the master controller 70 receives information concerning operation parameters of the compressors 14 A, 14 B, and 14 C. A primary control parameter is suction pressure. The controller 70 is programmed so that it manipulates (e.g., such as by averaging) the suction pressure readings from the BCCSCMs 48 to determine the refrigeration level produced by the multiplexed compressors 14 A, 14 B, and 14 C. The controller 70 uses this information to strategize cycling compressors in the system to achieve the desired refrigeration capacity level.

One exemplary method of dynamically controlling a plurality of multiplexed compressors (e.g., compressors 14 A, 14 B, and 14 C) is schematically shown in FIGS. 16A-16F. The flowcharts represent one or more software modules that are continuously called by the CPU 72 to dynamically control the multiplexed compressors. Before proceeding further, it should be noted that the blocks of FIGS. 16A-16F represent software instructions received, interpreted, and executed by the CPU 72 , resulting in the CPU 72 (and the master controller 70 ) performing the operations of the blocks. It should also be noted that FIGS. 16A to 16F is one exemplary method. Other acts can be included with the method shown in FIGS. 16A-16F, one or more acts shown in FIGS. 16A-16F can be removed, and the order or sequence of the acts shown in FIGS. 16A-16F can vary. Furthermore, while the method shown in FIGS. 16A-16F will be described in connection with software, the method can be implemented by other means (e.g., an ASIC).

As discussed earlier, the refrigeration system includes one or more multiple suction groups, where each suction group has one or more compressors. If a suction group has a plurality of compressors, the compressors are multiplexed in an arrangement (typically a parallel arrangement). Referring to FIG. 16A, the master controller 70 performs a capacity calculation for each suction group and each compressor of each suction group. At blocks 1600 , the master controller 70 initializes the loop counters. At blocks 1605 , the master controller 70 determines (e.g., calculates by adding capacities for each compressor (as shown in FIG. 16A), obtain previous calculations from storage, etc.) the total capacity for the suction group at a given operating point. The master controller 70 uses known equations for determining the capacity of each compressor at the current operating pressures when performing the capacity calculations. At blocks 1610 , the master controller 70 determines the capacity of each individual compressor as a percentage of the total capacity. By way of example, if a first suction group has three compressors (e.g., 14 A, 14 B, and 14 C), the first compressor (e.g., 14 A) may have a 50% capacity, a second compressor (e.g., 14 A) may have a 25% capacity, and a third compressor (e.g., 14 A) may have a 25% capacity. At block 1615 , the master controller determines whether the capacity calculations were performed for all of the suction groups. If the answer is affirmative, then the master controller proceeds to block 1620 (FIG. 16B). Otherwise, the master controller returns to block 1605 .

At FIG. 16B, the master controller determines a current compressor run pattern, current run capacity, and current % total capacity. At blocks 1620 , the software initializes the loop counters. At blocks 1625 , the master controller 70 builds a binary image of the status of the compressors 14 and determines the current run capacity of each suction group. More specifically, the master controller 70 determines which compressors 14 are currently on, and adds the capacity of each activated compressor 14 to the current run capacity for the respective suction group(s). At block 1630 , the master controller 70 determines the current run capacity of each suction group as a percentage of the total capacity of each suction group. Continuing the earlier example, if the second and third compressors 14 B and 14 C are ON, then the current run capacity is 50% of the total capacity. At block 1635 , the master controller determines whether the capacity calculations were performed for all of the suction groups. If the answer is affirmative, then the master controller proceeds to block 1640 (FIG. 16C). Otherwise, the master controller returns to block 1620 .

In FIGS. 16C-16F, the master controller 70 determines the control pattern for the next cycle. At block 1645 , the master controller 70 determines whether an increase in run capacity is required. If the answer is affirmative, then the master controller proceeds to block 1650 (FIG. 16D). Otherwise, the master controller proceeds to block 1655 (FIG. 16E).

With reference to FIG. 16D, the master controller 70 determines the next control pattern, which requires an increase in run capacity. Increasing the run capacity of a suction group typically requires activating an inactive compressor. At block 1650 , the master controller determines whether all compressors are ON. If the answer is affirmative, then the master controller proceeds to block 1660 (FIG. 16C). Otherwise, the master controller proceeds to blocks 1665 (FIG. 16E). At blocks 1665 , the master controller 70 determines each available capacity percentage combination for each suction group. Continuing the earlier example, the percentage combinations for compressors 14 A, 14 B, and 14 C include 25%, 25%, 50%, 50%, 75%, 75%, and 100%. However, if one of the compressors has an alarm condition, that compressor is removed from the possible combinations (block 1665 E). At blocks 1670 , the master controller 70 determines the next capacity increment. Revisiting the earlier example, the second and third compressors 14 B and 14 C were ON resulting in a 50% run capacity. The next available run capacity is 75% (i.e., activating the first compressor 14 A with either the second or third compressors 14 B or 14 C). At block 1670 F, the master controller 70 performs a “FIFO test.” The FIFO test (shown in detail in FIG. 16F) determines the next compressor run pattern when multiple possible combinations have an equivalent run capacity. That is, if blocks 1665 and 1670 result in multiple combinations for the next available capacity, the FIFO test determines the next compressor run pattern. Continuing the earlier example, the next available run capacity for the three compressors 14 A, 14 B, and 14 C is 75%, and there are two combinations that result in that run capacity (i.e., compressors 14 A and 14 B, or compressors 14 B and 14 C). In the configuration shown in FIG. 16F, the master controller 70 selects the most optimal run pattern for the compressors 14 . For example, the most optimal run pattern can include compressor run time as a variable. Optimizing the run pattern with compressor run time attempts to equitably distribute compressor run time over the compressors of the suction group. However, other tests can be included in selecting the next compressor run pattern.

Returning to block 1645 , the master controller determines whether an increase in run capacity is required. If the answer is negative, then the master controller 70 proceeds to block 1655 (FIG. 16E). In general, the control scheme of FIG. 16E corresponds to FIG. 16D; however, the master controller 70 decreases the run capacity of the suction group. Decreasing the run capacity typically requires deactivating an active compressor.

At block 1655 , the master controller 70 determines whether all compressors 14 are OFF. If the answer is affirmative, then the master controller 70 proceeds to block 1660 (FIG. 16C). Otherwise, the master controller 60 proceeds to blocks 1675 (FIG. 16E). At blocks 1675 , the master controller 70 determines each available percentage combination for each suction group. Blocks 1675 generally correspond to blocks 1665 (FIG. 16D). At blocks 1680 , the master controller determines the next capacity decrease. Revisiting the earlier example, the first and second compressors were ON resulting in a 50% run capacity. The next available run capacity decrement is 25% (i.e., activating the second or third compressors 14 B or 14 C). Similar to 1670 discussed above, at block 1680 F, the master controller 70 performs a “FIFO test.” The FIFO test (shown in detail in FIG. 16F) determines the next compressor run pattern when multiple possible combinations have an equivalent capacity. That is, if blocks 1675 and 1680 result in multiple combinations for the next available capacity, the FIFO test determines the next compressor run pattern. Continuing the earlier example, the next available capacity for the three compressors 14 A, 14 B, and 14 C is 25%, and there are two combinations that result in that capacity (i.e., activating the second or third compressors 14 B or 14 C). In the configuration shown in FIG. 16E, the master controller selects the next compressor run pattern.

Returning back to blocks 1660 (FIG. 16C), the master controller 70 updates sequence status information in view of FIFO calculations. More specifically, the master controller keeps a continuous runtime for each compressor 14 A, 14 B, and 14 C. This information is used in the FIFO calculations when multiple capacities are possible. At block 1685 , the master controller 70 exits the software routine, resulting in a pattern for each suction group.

In one construction, the routine shown in FIG. 16 is called when a change in capacity for a suction group is required. More specifically, in one construction of the refrigeration system, a PID error signal is used for controlling the operation of the compressors 14 . If the error signal requires a change in capacity, the CPU 72 invokes the routine in FIG. 16, resulting in a new run pattern.

In one construction, should the master controller 70 (and in particular the CPU 72 ) fail, the BCCSCMs 48 and 1500 are capable of performing the controller functions for the compressors 14 A, 14 B, and 14 C. A flowchart of the one operation of the processors 49 (or 1503 ) in the master fail mode is shown in FIG. 5. As stated above with reference to FIG. 4, the processor 49 of each BCCSCM 48 waits a predetermined time period for a message from the master controller 70 . If the period times out with no message, the processor 49 defaults to a master fail operation mode.

In the operation shown in FIG. 5, the BCCSCMs 48 (and/or 1500 ) communicate with each other over the communication and power line of the bus 80 , in addition to communicating with the controller 70 . In the failure mode, each processor 49 (or 1503 ) determines whether it is to have primary control. One processor of the BCCSCMs will have previously been programmed with a certain identification or address, e.g., ID=1. Typically, this would be the BCCSCM 48 of the first compressor 14 A in the system. Any BCCSCM 48 not having this identification will continue to operate only responsively to commands received over the field bus network (i.e., it resumes standard operation as a slave). It is also envisioned that the slave processors (i.e., processors associated with compressors 14 B, 14 C) would start a second timer once entering the failure mode to look for a message from the processor of the BCCSCM 48 designated for primary system control in the failure mode (i.e., the processor 49 associated with compressor 14 A). If the other processors 49 do not receive such a message, a second BCCSCM 48 would be pre-selected (e.g., the BCCSCM having ID=2 associated with compressor 14 B) to control the operation of the system in the failure mode. Thus, the system is highly granular, allowing for multiple failures while maintaining operation.

In one method of operation, the processor 49 (or 1503 ) of the BCCSCM 48 (or 1500 ) of compressor 14 is identified as the primary control or master, in case of failure of the master controller 70 , and will execute a master control function involving at least basic compressor cycling. In that regard, the primary control processor 49 is capable of determining the collective suction pressure of the operating compressors 14 A, 14 B, and 14 C and providing control commands for itself and the other slave processors to turn compressors on and off to maintain the refrigeration capacity requirements of the system. After performing this function, the “primary” processor 49 resumes a slave presence on the network which allows it to again look for a message from the master controller 70 for a period of time before returning again to perform a system control function. Once the master controller 70 is detected, the primary control processor 49 returns to its standard (slave) mode of operation.

In general, the distributed intelligence control provides for ease of assembly and installation and enhances control. The compressors 14 A, 14 B, and 14 C are configured with one or more sensors to optimize uniformity of measurement of operation parameters and to minimize installation variances as well as provide protection of such sensor devices. The modularity and intelligence of the compressor controllers interface with the master controller 70 to assure optimum compressor performance, as well as granularity of the system.

For the constructions utilizing a two wire bus that provides power and communication to the control modules (e.g., via an AS-i bus), assembly of a refrigeration system is made easier by simplification of the wiring which is normally done upon installation. The high voltage lines 44 A, 44 B, and 44 C are still used to run the compressors 14 A, 14 B, and 14 C for primary operation. According to electrical codes, it is typically required to shield these lines such as by placing them in conduit. However, for the construction shown in FIG. 1, no separate power lines other than three phase high voltage lines 44 must be run to the compressor motors 32 . Additionally, it is unnecessary to run additional high voltage lines to the BCCSCM's. Instead, a single high voltage feed line 69 supplies the power supply 74 for the CPU 72 and communication module 76 and also the network power supply 78 .

Power for all of the BCCSCMs 48 (and/or 1500 ) is supplied through the same two wire bus 80 extending from the communications module 76 to the control and safety modules 48 . The bus 80 does not need to be shielded because it carries only 30 VDC power. Preferably, the wiring of the BCCSCMs 48 to the master controller 70 is done at the factory where the compressors 14 A, 14 B, and 14 C are mounted together with the controller on a compressor rack (not shown) so that no power wiring of any kind for the BCCSCMs is required at the building site. The number of BCCSCMs 48 attached to the bus 80 up to some upper limit of the controller 70 (e.g., 31) is immaterial and requires no special re-configuration of the controller.

As stated above, the connection of the BCCSCMs 48 (and/or 1500 ) to the communication bus 80 achieves not only power, but communications for the control and safety modules. No separate feedback wiring from the individual sensors is necessary. The processor 49 (or 1503 ) of the BCCSCM executes commands from the master controller 70 and is capable of reporting back to the controller 70 that the command has been executed. The processor 49 reports the readings from all of the sensors 50 - 58 or 1525 - 1555 , and not only whether a safety limit value has been exceeded, but exactly which one it is and what the exact value was. This enables the master controller 70 to provide specific information to a repair technician without any additional wiring between the controller 70 and the BCCSCM 48 . In addition to permitting refrigeration level control by the controller 70 , the system allows the controller 70 to make other adjustments in the system and to monitor trends for use in failure prediction/avoidance.

The processors 49 (and/or 1503 ) of the BCCSCMs also, in one construction, have the embedded intelligence to operate the refrigeration system in case the master controller 70 fails. In that regard, the BCCSCMs 48 (and/or 1500 ) are capable of communicating with each other as well as the master controller 70 over the two wire bus 80 . In case of failure of the master controller, one of the BCCSCMs will take over as master or “primary” and can perform at least the function of averaging the measured suction pressure readings from the operating compressors to determine refrigeration level and determine how to cycle the compressors to maintain a predetermined capacity.

Referring still to FIG. 1, the commercial refrigeration system may also optionally include one or more liquid subcoolers 15 and an oil separation and return subsystem 17 . The general operation of liquid subcoolers is known in the art. An exemplary embodiment of a control system for controlling such a subcooler and/or such an oil separation and return system, in accordance with aspects of the present invention, is described in further detail below with respect to FIGS. 10 and 10A. Examples of oil separation systems are included in U.S. Pat. Nos. 4,478,050, 4,503,685, and 4,506,523, which are incorporated herein by reference.

For purposes of disclosure and simplicity, the refrigeration so far described herein has been, primarily, a vapor phase evaporative cooling system. The invention, however, is not to be so limited in its application. For example, FIG. 1A is a schematic diagram of one exemplary form of a modular secondary refrigeration system 200 which could also be modified to be implemented and controlled by an integrated distributed intelligence control system. Such a secondary cooling system is described in exacting detail in U.S. Pat. No. 5,743,102, the entire disclosure of which is incorporated herein by reference.

Referring to FIG. 1A, the refrigeration system 200 comprises a primary vapor phase refrigeration system including a plurality of parallel, multiplexed compressors 202 . The compressors deliver liquid refrigerant at high temperature and pressure to a first condenser 204 and a second condenser 206 from which the liquid refrigerant passes to an expansion valve 208 feeding the refrigerant into an evaporator 210 . Vaporous refrigerant is drawn from the evaporator 210 back to the compressors 202 to complete a conventional vapor phase refrigeration cycle. However, the evaporator 210 is incorporated as part of a first heat exchanger including a first reservoir 212 holding a coolant liquid (e.g., glycol). Typically, this reservoir 212 is located close to the compressors and condensers so that the vapor phase refrigerant loop is short, requiring minimal refrigerant. The first reservoir 212 is part of a secondary refrigeration system including pumps 214 which drive coolant fluid through the reservoir to second heat exchangers 216 located in respective fixtures 218 , which may constitute refrigerated merchandisers in the shopping arena of a supermarket. The coolant liquid absorbs heat from items (not shown) in the fixtures 218 , while remaining in a liquid state, and then is forced by the pumps 214 back to the first reservoir 212 where that heat is removed to the vapor phase refrigeration system. The vapor phase refrigeration system may beneficially be, but is not necessarily, located adjacent to the fixtures 218 . The temperature of the fixtures 218 may be maintained through the use of sensors (e.g., sensors 220 ) which control valves 222 and the pumps 214 . The control system, in one construction, may be beneficially used to control the operation of the primary vapor phase and secondary liquid refrigeration systems according to the principles set forth herein.

The refrigeration system 200 further includes a coolant liquid defrost system comprising a second coolant liquid reservoir 224 that contains the first condenser 204 . The coolant liquid system pumps 214 are valved to divert some of the coolant liquid to the reservoir 224 where it is heated by the hot refrigerant passing through the first condenser 204 . At a predetermined interval or when it is sensed that frost has built up on the second heat exchangers 216 , valves including defrost valves 226 are controlled to stop the flow of cold coolant liquid from the first reservoir 212 to the second heat exchangers 216 and to permit flow of heated coolant liquid to the second heat exchangers for defrosting. Again, the control system can be beneficially employed to control operation of the defrost of the system 200 . Additional aspects of secondary cooling systems, including specific valving and flow control structures, are disclosed in U.S. Pat. No. 5,743,102. Accordingly, one skilled in the art having the benefit of the present disclosure could adapt the teachings herein for use with secondary cooling systems by providing similar distributed, modular control and monitoring of the compressors, valves, set points, and other components/sensors associated with such secondary cooling systems.

FIG. 7 is a system block diagram illustrative of an integrated distributed intelligence control system 700 for use in a refrigeration application, such as a commercial refrigeration application. As depicted therein, the system 700 preferably includes several field bus communication networks that cooperate to provide distributed intelligence system monitoring and control. A local network server 702 , a local workstation 704 , and a remote workstation 706 provide top-level control. In one construction, the local network server 702 and the local workstation 704 will be installed near the refrigeration system (e.g., inside the facility containing the refrigeration system). In one construction, the remote workstation 706 is constructed and configured to communicate via a wide-area network such as the Internet 708 . Other network levels are preferably connected to the top-level via a communications interface, such as, for example, an Ethernet hub 712 .

A first field bus control network 716 , which preferably comprises an AS-i bus as previously described herein, is connected to the Ethernet hub 712 via a gateway interface device 714 and a rack PLC 720 (also referred to as the system controller). It is to be understood and appreciated that the rack PLC 720 illustrated in FIG. 7 corresponds to the CPU associated with master controller 70 , which is illustrated and described with respect to FIGS. 1 and 2 above. Accordingly, the rack PLC 720 may also be referred to as the CPU or even as the master controller. One construction of the gateway interface device 714 is a Siemens IPC, which is a Windows NT® based computer. As explained in greater detail below, gateway interface device 714 is constructed and arranged to provide a gateway between similar and dissimilar field bus networks having similar and dissimilar network protocols. In other constructions, one or more operations described in connection with the remote workstation 706 , the local workstation 704 , and/or the local network server 702 can be performed by the gateway interface device 714 and vice-versa. For one exemplary construction, the device 714 can function as both the local workstation and the gateway interface. As another example, in some constructions that are discussed below, the device 714 includes one or more tables for use by the rack PLC 720 . However, these tables can be located at the remote workstation 706 or the local workstation 704 .

A wireless hub 713 may optionally be included to allow access to the control network by a work station over a wireless interface (e.g., a wireless Ethernet link), such as between a wireless computing device 715 (e.g., a Windows CE® compatible computer) and the Ethernet hub 712 .

Local workstation 704 , remote workstation 706 , and wireless computer 715 can be used to access system information such as, for example, set points, defrost schedules, alarm logs, current system conditions (e.g., temperatures), and other system status and set point information. Likewise, these devices may be used to input system information such as set points or system schedules (e.g., defrost schedules or maintenance schedules).

The first field bus control network 716 also includes an AS-i master interface 722 which serves as a communication interface between rack PLC 720 and various control modules. The AS-i master interface 722 corresponds to the communication module 76 discussed above with respect to FIG. 1. The devices associated with the first field bus control network 716 may be generally referred to as “rack devices,” or as being “located at the rack.” This nomenclature is used because in the embodiment illustrated in FIG. 7, rack PLC 720 is installed at or near the rack of compressors for which it provides system integration and control. For example, a rack will typically include between two and thirty-one compressors, and a given installation may include multiple racks. Thus, a large system might have thirty-two racks of compressors, each controlled by a separate rack PLC that interfaces with a common processor or gateway device. In one construction, each rack PLC interfaces with computer/gateway interface device 714 . The gateway device 714 accommodates for set point control, status monitoring, fault logging, data storage, and the like for each rack PLC (and the devices integrated by such rack PLC) in the system. For simplicity, FIG. 7 depicts an installation having only a single rack, and, accordingly, a single rack PLC 720 .

Before proceeding further, it should be noted that aspects of the refrigeration system discussed herein are not limited to a refrigeration system having compressors located on a rack. Rather, one or more aspects discussed herein can be applied to systems having a single compressor unit and to systems having multiple single compressor units not located on a rack.

The control modules illustrated in FIG. 7 preferably include one or more compressor controllers (e.g., Bus Compatible Compressor Safety and Control Modules or BCCSCMs 48 or 1500 ), one or more branch controllers 724 (also referred to herein as Bus Compatible System Branch Modules 724 or BCSBMs), and one or more valve controllers 726 (also referred to herein as Bus Compatible Valve Control Modules or BCVCMs). The one or more compressor controllers 48 (or 1500 ), one or more branch controllers 724 , and the one or more valve controllers 726 will also be generically referred to herein as device controllers and subsystem controllers. When connected to the first field bus control network 716 , each of these modules 48 , 724 , and 726 communicates with rack PLC 720 , via an AS-i compatible bus 728 and AS-i master 722 . The operation of BCCSCM 48 has previously been described. The operational aspects of the BCSBM 724 and the BCVCM 726 are described in greater detail below. Of course, other constructions for the first field bus control network 716 can by used with the refrigeration system. For example, other field bus types can be used in place of the AS-i compatible bus 728 .

A second field bus control network 730 , which can also comprise another AS-i bus as previously described herein, is connected to gateway interface 714 and the master controller (rack PLC 720 ) over a relatively longer distance network 731 (e.g., a twisted pair network, such as, for example, a Siemens' MPI compatible interface or ProfiBUS). In one construction, the second field bus control network 730 is slaved to the rack PLC 720 . However, other configurations are possible. Second field bus control network 730 includes a condenser PLC 732 (also referred to as condenser controller), another AS-i master 734 , and one or more fan control modules 736 (also referred to as Bus Compatible Fan Control Modules or BCFCMs). For FIG. 1, the condenser PLC 732 corresponds to condenser controller 84 , and may also be referred to as providing a network gateway between BCFCM 736 and rack PLC 720 . Operational aspects of the condenser PLC 732 , AS-i master 734 , and BCFCM 736 were also described above with regard to FIG. 1. Of course, other constructions for the second field bus control network 730 can by used with the refrigeration system. For example, other field bus types can be used in place of the AS-i compatible bus.

A third field bus control network 740 communicates with rack PLC 720 over another relatively longer distance communication bus 741 , such as, for example, a LonWorks® network (also referred to as a LonWorks® bus or an Echelon network). LonWorks® information and network components are available from the Echelon Corporation of Palo Alto, Calif. The third field bus control network 740 is used to facilitate communications between the master controller (rack PLC 720 ) and one or more refrigeration cases, which are controlled by one or more case/fixture controllers 744 (also referred to as Bus Compatible Modular Case Controls, BCMCCs, case controllers, or display case controllers), the operation of which is described below. Similar to the other device controller introduced earlier, the one or more case/fixture controllers 744 will also be generically referred to herein as device controllers and subsystem controllers. Communications between the BCMCC 744 and rack PLC 720 occurs via interface gateway 714 and the communication bus 741 . The type of gateway device used will typically depend upon the bus/communication protocols employed. In the system illustrated in FIG. 7, BCMCC 744 operates on a LonWorks®/Echelon compatible bus, thus interface gateway 714 is constructed and arranged to integrate communications between such a bus and rack PLC 720 . Of course, other constructions for the third field bus control network 740 can by used with the refrigeration system.

Also, as illustrated in FIG. 7, third party controls 746 and 748 (e.g., HVAC, fire, and rack/case controls) can optionally interface to, and become part of, system 700 , via communication bus 741 .