HK1137214B - Refrigerant system and operating method thereof - Google Patents

Description

Refrigeration system and method of operating the same

Technical Field

The present application relates to a refrigeration system having enhanced features and extended functionality. Further, the present application relates to a refrigeration system including a plurality of compressors (e.g., tandem compressors) that may include an economizer cycle, a bypass circuit, and a variable speed drive; the present application also relates to refrigerant systems that include a reheat function, wherein a control algorithm is used to provide diagnostic and prognostic information related to these enhancement features.

Background

Heating, ventilation, air conditioning and refrigeration (HVAC & R) systems are used to condition different environments. Such HVAC & R systems typically use a refrigerant that circulates throughout a closed loop circuit and are used as air conditioners, heat pumps, refrigeration units, and the like. Various enhanced techniques and system configurations are known and have been implemented to provide the required performance over a wide range of environmental conditions, meeting a variety of thermal load requirements.

In a very basic refrigeration system, a compressor compresses a refrigerant and delivers the refrigerant downstream to a condenser. The refrigerant passes through the condenser to an expansion device, from which it passes to an evaporator. From the evaporator, the refrigerant returns to the compressor. Such basic systems are often supplemented and enhanced by a number of different options and features to meet the needs of the application.

One such enhancement is the use of tandem compressors. Tandem compressors include a plurality of compressors, each compressor receiving refrigerant from a common suction manifold, each compressor independently compressing refrigerant and delivering refrigerant to a common discharge manifold. Each of these compressors can be independently turned on or off to vary the refrigeration capacity of the refrigeration system. In this manner, the capacity provided by the compressor subsystem to the overall refrigeration system can be tailored to the thermal load requirements of the conditioned space. Often, tandem compressor arrangements include oil and vapor equalization lines for enhanced functionality and reliability.

Another option that may be used in tandem compressor arrangements to vary the capacity of the refrigerant system is the use of a compressor unloading function. One common compressor unloading function selectively delivers at least a portion of the compressed (partially or fully) refrigerant back to the suction line. In this manner, when only partial load capacity is required, the amount of compressed refrigerant being passed through the refrigeration system is reduced. Other compressor unloading schemes are also known in the art. As is known, compressor unloading can also be used outside tandem compressor applications.

Another performance enhancement feature that may be used in tandem compressor arrangements is the use of a variable speed drive to vary the speed of the compressor motor. By providing variable frequency control for varying the speed of the compressor motor, the amount of compressed refrigerant delivered throughout the system can be varied accordingly. In addition, this enables the refrigerant system designer to customize the provided capacity to the desired capacity requirements. As noted above, the variable speed compressor may also be used outside of a tandem compressor arrangement.

Another option that may be used in tandem compressor arrangements to improve refrigerant system performance is to use an economizer cycle. The economizer cycle selectively taps a portion of the refrigerant downstream of the condenser and upstream of the expansion device and delivers the tapped refrigerant to a separate economizer expansion device. The tapped, partially expanded refrigerant is then used to cool the refrigerant circulating through the main circuit in an economizer heat exchanger. By providing this additional localized cooling, the capacity and/or efficiency of the refrigeration system is increased. As is known, an economizer cycle can use a single compressor or multiple compression stages operating in sequence. Also, the performance enhancement feature may be used outside tandem compressors.

Another optional refrigerant system that may or may not be used in conjunction with tandem compressors features a reheat function. In the reheat cycle system, refrigerant warmer than refrigerant flowing through the evaporator is directed through a reheat heat exchanger positioned on a refrigerant path upstream of the evaporator. The air to be conditioned may be cooled (and dried) in the evaporator to a temperature below the desired temperature. The air then passes through a reheat heat exchanger where it is heated back to the target temperature. However, since it has been subcooled in the evaporator, the air will have a lower moisture content than if it had been cooled only to the target temperature. Various reheat system configurations are known in the HVAC & R industry and the present invention is not intended to refer to any particular scheme, but rather to the general mechanical dry reheat concept, which uses a main refrigerant circulating throughout a refrigeration system. Further, the reheat function can be used outside tandem compressor applications.

Various diagnostic features are known in the art. However, the prior art has not provided a system for performing diagnostic and prognostic features based on the staged operation of compressors and other associated system components when any one of a plurality of tandem compressors or other associated system components may be experiencing problems. In addition, controls for optimizing refrigerant system operation when one of the tandem compressors may be operating in an undesirable manner (e.g., outside of specified limit data) have not been provided.

Disclosure of Invention

In one aspect of the present invention, the present invention discloses a refrigeration system comprising: a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold; a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online.

In another aspect of the invention, a method of operating a refrigeration system is disclosed, comprising: providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online.

In some embodiments of the present disclosure, the refrigeration system includes tandem compressors and may also include additional performance enhancement features such as an economizer cycle, a bypass circuit, a variable speed drive, or combinations thereof. In other embodiments, the refrigerant system may include a reheat function enhancement feature, which may be associated with a single compressor or multiple compressors. In the disclosed embodiments, control algorithms are used to provide diagnostic and prognostic information related to these enhanced features. In one disclosed embodiment, a refrigerant system having tandem compressors is operated and controlled in a manner to independently operate at least one of the tandem compressors. When each tandem compressor is turned on, various system operating parameters are monitored. These parameters may include pressures and temperatures measured in the compressor system suction and discharge manifolds. For example, when another tandem compressor is turned on, the suction pressure is expected to decrease and the discharge pressure is expected to increase. If the system operating conditions do not vary beyond the error band, as would be expected when each particular compressor is brought online, then that particular compressor is identified (or identified) as a faulty compressor. The present invention may also update the control algorithm when a warning signal is issued for maintenance to be performed, causing a particular compressor to be removed from the control sequence in order to operate the tandem compressors to provide the required capacity.

Similar diagnostic features are implemented by additionally providing an unloading function to the tandem compressors, and/or a variable speed drive for the compressor motor, and/or an energy saving function. All of these features can be used alone or in combination with one another. In the disclosed embodiment, when the unloading function is activated, the suction pressure is expected to rise, the discharge pressure is expected to fall, and the discharge temperature is expected to rise. Therefore, a sensor placed at any of these locations should detect a respective change that exceeds a predetermined error band. If this does not occur, the offload function is considered to be malfunctioning. It is apparent that more than one compressor of the tandem compressors may be provided with the unloading function.

In another embodiment, when the economizer function is activated, the suction pressure should be decreased, the discharge pressure should be increased, and the discharge temperature should be decreased. Furthermore, if these changes in the operating parameters do not occur, a component of the energy saving branch fails. It should also be noted that more than one compressor may be equipped with an economizer function, and that these compressors may or may not share other auxiliary economizer branches, such as economizer heat exchangers and economizer expansion devices.

In another embodiment, a variable speed compressor fault should be identified if the suction pressure does not drop and/or the discharge pressure does not rise while the compressor speed is increasing smoothly.

In another embodiment, the initiation of a reheat function, which may or may not be associated with a tandem compressor, will generally correspond to both a reduction in discharge and suction pressures. If no such change is observed, the heating branch has a faulty component.

Furthermore, if the respective system operating parameters and changes in these parameters are monitored over time as the respective refrigeration systems are turned on or off, conclusions can be drawn as to the degradation of each of the above-described components, features or options, and preventive maintenance can be performed to avoid malfunctions. In addition, if a function is activated (e.g., another tandem compressor is turned on) and the refrigerant system is operating outside of the specified envelope, corrective measures (e.g., activating the unload function or deactivating the economizer function) may be performed to bring the refrigerant system back within a "safe" range.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Drawings

FIG. 1 is a schematic diagram of the inventive refrigeration system.

Fig. 2 is a partial view of a portion of a refrigeration system of a second embodiment.

Fig. 3 is another schematic of the inventive refrigeration system.

Fig. 4 is a basic flow diagram of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

FIG. 1 illustrates a refrigerant system 20 showing tandem compressors incorporating the present invention. It should be noted that as shown in this figure, the system has optional features including: an economized cycle (economized heat exchanger, economized expansion device and associated piping), an unloader option (unloader valve and associated piping), a reheat function (reheat heat exchanger and piping), and a variable speed option with variable frequency drive. All of these features can be selectively added to the main embodiment with tandem compressors, either independently or in combination with other options. Combinations of these options are shown in fig. 1, but many of them can be eliminated as desired. The compressors 22, 24 and 26 all deliver refrigerant from a common suction manifold 27 to a common discharge manifold 29. As shown, the compressor 26 may be provided with an optional variable frequency drive 28 for operating the compressor motor at different speeds. In this manner, the overall capacity provided by the combination of compressors 22, 24 and 26 can be precisely tailored to the desired capacity to meet the comfort conditions of the indoor environment.

A suction pressure sensor 32 and a discharge pressure sensor 34 are illustrated as being located on manifolds 27 and 29, respectively, and typically have been incorporated into refrigeration system 20 for other control purposes. Alternatively, temperature sensors 53 and 39 may be used to measure saturation temperatures corresponding to suction and discharge pressures, respectively. Further, an exhaust temperature sensor 49 may also be used. Refrigerant compressed by the tandem compressor bank is delivered downstream to a condenser 38, as is known. A temperature sensor 39 is shown in the two-phase region of the condenser 38. The valve 36 selectively allows or blocks the flow of refrigerant toward the condenser 38. In addition, a bypass line 42 and a bypass valve 40 allow at least a portion of the refrigerant to bypass the condenser 38. The condenser 38 is air-cooled and driven by a condenser fan 47. The condenser bypass and reheat functions (explained below) are typically activated to dehumidify with little or no cooling of the air being delivered to the environment to be conditioned.

An economizer heat exchanger 46 is positioned downstream of the condenser 38. As shown, a tap line 58 selectively taps a portion of the refrigerant to an economizer expansion device 60 and then through the economizer heat exchanger 46. The majority of the flow of refrigerant in fluid line 43 exchanges heat with the tapped refrigerant. Since the tapped refrigerant in line 58 is passed through the economizer expansion device 60 and expanded to a low pressure, which is also at a relatively low temperature, the refrigerant in the fluid line 43 can be further cooled. This provides a greater cooling potential when the main circuit refrigerant reaches the downstream evaporator 50. Refrigerant from the tap line 58 passes through a line 62, into a vapor high pressure line 64, and to an intermediate compression point of the compressor 22. It should also be noted that various configurations and flow configurations exist for an energy efficient circulation system and would likewise benefit from the present invention. Further, more than one tandem compressor may be provided with economizer function, which may or may not share the same economizer branch components, such as economizer heat exchanger 46 and economizer expansion device 60.

The refrigeration system 20 also includes a reheat circuit. As is known, a three-way valve 48 (which may be replaced, for example, by a pair of solenoid valves, as is known) selectively directs refrigeration through the reheat heat exchanger 52 and a check valve 59. The reheat heat exchanger 52 is positioned in the path of air that has been removed from the evaporator 50 by the evaporator fan 51. The evaporator fan 51 moves air out of the evaporator 50 and out of the reheat heat exchanger 52. As is known, the use of a reheat heat exchanger with a refrigerant that is hotter than the refrigerant passing through the evaporator 50 allows the reheat circuit to have a significantly higher drying capacity, with a concomitant cooling, heating or naturally perceptible volume of air delivered into the conditioned space. Generally, in any reheat mode of operation, the evaporator is used to subcool air to a temperature that is below the desired temperature in the environment conditioned by the refrigerant system 20. This enables more moisture to be removed than if the air was cooled only to the target temperature. The air then passes through the reheat heat exchanger 52 where the air is heated to return to the target temperature. The refrigerant that has passed through the reheat heat exchanger 52 is returned to the main refrigerant circuit in fluid line 43 at point 54. The refrigerant then passes through a main expansion device 56 and to the evaporator 50. From the evaporator 50, the refrigerant returns to the compressor suction manifold 27.

The controller 30 receives input signals from various pressure and/or temperature sensors and controls various components in the refrigeration system 20.

In one embodiment of the disclosed invention, the controller is operable to selectively bring any one or any combination of the compressors 22, 24 and 26 and various operational enhancement features online to achieve a desired perceived and potential capacity. In a principal feature of the present invention, each of the tandem compressors 22, 24 and 26 is brought on-line independently and in time to meet the thermal load requirements in the conditioned space. If the suction pressure detected by pressure sensor 32 does not decrease while the next tandem compressor is brought on-line, the compressor is flagged as having a problem. Similarly, if the discharge pressure detected by pressure sensor 32 does not decrease when the next tandem compressor is brought on-line, then the compressor fails. As is known, temperature sensors 53 and 39, respectively, positioned in the two-phase region of the evaporator 50 and in the condenser 38 may alternatively be used. The controller 30 may issue a warning signal to indicate that maintenance of the corresponding compressor is required. Further, the controller 30 is operable to make its control algorithm independent of the compressors 22, 24 or 26 that have been identified as potentially malfunctioning or requiring service. Thus, the present invention is not only capable of diagnosing malfunctioning tandem compressors, but is also capable of varying the control for the refrigerant system 20, thereby removing any potentially problematic compressors in the tandem compressor bank from the operational control sequence.

As is known, tandem compressors need to have at least one common manifold. For example, if the tandem compressors 22, 24 and 26 have only a common suction manifold 27 and separate discharge manifolds connected to separate condensers, only the suction pressure sensor 32 (or temperature sensor 53) may be used for diagnostic and control purposes. On the other hand, if the tandem compressors 22, 24 and 26 only have a common discharge manifold 29 and separate suction manifolds connected to separate evaporators, the controller 30 can only use the discharge pressure sensor 34 (or temperature sensor 39) for diagnostic and operational control.

An unloader line 68 including a bypass valve 66 selectively connects the vapor high pressure line 64 to a suction line 67 leading to a suction port of the compressor 22. Further, the tandem compressor 26 may be a variable speed compressor with a motor controlled by a Variable Frequency Drive (VFD)28, with the VFD 28 being controlled by a controller 30. While only one compressor is shown with a variable frequency drive and only one compressor is shown receiving refrigerant from the economizer cycle and being provided with an unloader function, it should be understood that more than one compressor could be provided with any one or combination of these features. Further, the economizer cycle may include multiple sequential compression stages instead of a single compound compressor. Further, the tandem compressors equipped with the economizer function may or may not share other auxiliary economizer branch components, such as an economizer heat exchanger and an economizer expansion device.

When the unloader valve 66 is activated, an expected increase in suction pressure, as recorded by the suction pressure sensor 32 (or temperature sensor 53), and a decrease in discharge pressure, as recorded by the discharge pressure sensor 34 (or temperature sensor 39), should be observed. If the desired change has not occurred, a determination may be made that the offload function is not operating properly.

Similar conclusions can be drawn when using the energy saving function. When the economizer function is operating, the expected increase in discharge pressure recorded by the discharge pressure sensor 34 (or the temperature sensor 39) and the decrease in suction pressure recorded by the suction pressure sensor 32 (or the temperature sensor 53) should be observed. Furthermore, if the desired change does not occur, a conclusion can be drawn that the energy saving function is not functioning properly. In addition, if an economizer line pressure sensor 63 is available, it can also be used to determine whether the economizer and unloader functions are functioning properly. The economizer pressure should drop when the unloader function is engaged and increase when the economizer function is engaged. Further, a current sensor or an electric power sensor may be used to determine whether any compressor or any of the above functions has been used or has been operating normally. For example, if the compressor is not brought online as desired, the current sensor or the electrical power sensor will not detect the desired change in current or power draw. Further, as described above, the discharge temperature sensor 49 may be used to determine whether the energy saving and unloading function is operating normally. The discharge temperature, recorded by the discharge temperature sensor 49, is expected to decrease when the energy saving function is used and increase when the unloading function is activated.

It is expected that the discharge pressure measured by the discharge pressure sensor 34 (or the temperature sensor 39) will increase if the bypass line around the condenser is operated. If this does not occur, it may be assumed that the condenser bypass function may not be operating properly. Similarly, when the reheat cycle system is activated by opening the three-way valve 48, it is expected that the suction pressure and the discharge pressure recorded by the suction pressure sensor 32 and the discharge pressure sensor 34 (or the temperature sensors 53 and 39), respectively, will be changed according to the selected operation drying mode. Furthermore, if this does not occur, the reheat function may be considered to be malfunctioning.

Similarly, when using any of these functions, a change in current or power draw is desired. If such a change does not occur, this is an indication that the reheat function is not functioning properly. It should be noted that if the system is not equipped with the optional features described above, such as reheat, economizer cycle, bypass unloading, and VFD, then in the simplest configuration, when one of these compressors is called on-line by the controller, a fault in any of the tandem compressors 22, 24, and 26 can be determined by monitoring changes in system parameters; if the system operating conditions do not change, this indicates that the reference compressor is not operating properly. The controller performs an action to remove the compressor from the working tandem compressor sequence.

Fig. 2 shows another embodiment 80 in which tandem compressors 82 deliver refrigerant from a suction manifold 85 to an intermediate manifold 86. The refrigerant is delivered from the intermediate manifold 86 to the second stage compressor 84 and then to a discharge line 88. These compressors may be provided with a steam high pressure or fluid high pressure line 90, similar to the steam high pressure line 64 in the first embodiment. Fig. 2 is illustrative and many variations on the design structure and number of levels are possible. For example, each compression stage may include tandem, economized and variable speed compressors, and an unloading function.

In addition, system current, power draw, or various pressures and temperatures within the compression system 80, such as discharge pressure recorded by discharge pressure sensor 92, may be detected to ensure proper operation of the compression system; also, the controller can modify the operating schedule by detecting the discharge pressure to determine if any of compressor stages 82 and 84 are faulty.

Fig. 3 depicts another embodiment 120 of the invention, the refrigeration system solution including a single compressor 120 and hot gas reheat function. As with the embodiment of fig. 1, the suction and discharge pressure sensors 132 and 134 (or temperature sensors 153 and 139) monitor changes in suction and discharge pressure, respectively. In addition, a current or power draw sensor 171 monitors compressor power consumption and a supply air temperature sensor 173 monitors the temperature of the air delivered to the conditioned space. All sensors are connected to the controller 130 and communicate with the controller 130. The operation and control of the refrigeration system 120 is similar to the operation and control of the refrigeration system 20. When the reheat function is activated, some variation in the system operating parameters monitored by the above-described sensors is expected by switching the three-way valve 148 to allow refrigerant to flow through the reheat coil 152. When the reheat function is used, the discharge and suction pressures recorded by the discharge and suction pressure sensors 134 and 132 (or the temperature sensors 139 and 153), respectively, should increase, the current or power draw recorded by the sensor 171 should generally decrease, and the temperature of the supply air recorded by the sensor 173 should increase. If no such change is observed, the reheat function does not work properly and corrective action needs to be performed. It is clear that not all of these sensors need to be included in the refrigeration system design, as their role may be redundant, and only one sensor can be adapted sufficiently well for the purpose. The three-way valve 148 is positioned upstream of the condenser 138, however, it may be positioned at an alternative location downstream of the condenser 138, as shown at 199. It is evident that in the latter case, the return line from the reheat branch to the main refrigeration cycle should also be positioned downstream of the condenser 138.

By way of example, fig. 4 shows a very basic flow diagram of the invention in relation to tandem compressors. The compressors in the tandem compressor configuration are sequentially operated at periodic intervals, such as during system startup or shutdown, and the actual changes in the corresponding operating parameters are compared to expected changes. Alternatively, when the conditioned space requires additional capacity and the next compressor is to be brought online, the corresponding operating parameters are monitored and the associated changes are observed. Other components may also be operated, although this is optional. The current, and/or power draw, and/or pressure, and/or temperature at certain locations within the refrigerant system are monitored and a diagnostic process is performed. If any of the tandem compressors is identified as not functioning properly or any of the above system components is identified as malfunctioning, the control program is updated to not rely on and "bypass" the malfunctioning component and an alarm signal is issued. It should also be noted that the tandem compressors shown in fig. 1 are for descriptive purposes only, as these systems may be modified to make them more complex, e.g., including additional condensers and/or evaporators, having more than three compressors, etc. On the other hand, the tandem compressors shown in fig. 1 can be simplified by eliminating certain components and functions, such as a reheat function, a steam injection function, a bypass unloading, a variable speed function or reducing the number of compressors from three to two.

Furthermore, if the corresponding system parameters are monitored over time and stored in a database or control memory, conclusions can be drawn regarding the degradation of the refrigeration system components and preventive maintenance can be performed to avoid malfunctions. In addition, if a function is activated (e.g., another tandem compressor is turned on) and the refrigerant system is operating outside of the specified envelope, corrective measures (e.g., activating the unload function or deactivating the economizer function) may be performed to bring the refrigerant system back within a "safe" range.

The present invention thus provides a simple method of improving the control of a refrigerant system, and in particular a refrigerant system having tandem compressors and a reheat function, to eliminate any fault factors from the control algorithm. It is apparent that the recorded changes should exceed a specified error threshold, including (but not limited to) sensor variability, system operating fluctuations, part manufacturing errors, and the like.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (42)

1. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online.

2. The refrigerant system as set forth in claim 1, wherein at least one of a suction manifold or a discharge manifold is common to said tandem compressor bank.

3. The refrigerant system as set forth in claim 1, wherein said refrigerant system fault is a compressor fault.

4. The refrigerant system as set forth in claim 1, wherein each of said tandem compressors is brought online sequentially and expected changes in operating conditions are compared to detected changes.

5. The refrigerant system as set forth in claim 1, wherein said operating condition is one of a suction pressure and a suction temperature.

6. The refrigerant system as set forth in claim 1, wherein said operating condition is one of a discharge pressure and a discharge temperature.

7. The refrigerant system as set forth in claim 1, wherein said operating condition is one of current and power draw.

8. The refrigerant system as set forth in claim 1, wherein said tandem compressor bank includes two compressors.

9. The refrigerant system as set forth in claim 1, wherein said tandem compressor bank includes more than two compressors.

10. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the working condition is one of an energy-saving pressure and an energy-saving temperature.

11. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the refrigerant system further has a variable speed drive for at least one of the tandem compressors, an operating condition being monitored when the variable speed drive changes the speed of the motor for at least one of the tandem compressors, the monitored condition being compared to an expected condition to identify the fault of the variable speed compressor when the speed changes.

12. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein a bypass line is provided around the condenser, and the controller monitors a cooling condition when the bypass line is operated, and determines whether the malfunction is a malfunction of a bypass function by comparing the detected cooling condition with an expected cooling condition.

13. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the refrigeration system includes an economizer cycle, the economizer cycle being operated, and an operating condition being detected and provided to the controller, the controller comparing the detected operating condition to an expected operating condition while the economizer cycle is operating, and identifying the fault in the economizer function if the expected condition and the detected condition differ by more than a predetermined threshold.

14. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the refrigerant system includes an unloader function, the unloader function being operated and an operating condition being detected and provided to the controller, the controller comparing the detected operating condition to an expected operating condition while the unloader function is operating and identifying the fault in the unloader function if the expected condition and the detected condition differ by more than a predetermined threshold.

15. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the refrigerant system includes a reheat circuit, the reheat circuit being operated, and an operating condition being detected and provided to the controller, the controller comparing the detected operating condition to an expected operating condition while the reheat circuit is operating, and identifying the fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold.

16. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the controller updates the control algorithm such that the control algorithm is no longer dependent on the malfunctioning refrigerant system component or function.

17. A refrigeration system comprising:

a tandem compressor bank including a plurality of compressors, said compressors receiving refrigerant from a suction manifold, compressing said refrigerant, and delivering said refrigerant to a discharge manifold;

a condenser positioned downstream of the compressor train, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and then back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller operable to monitor the operating condition when each of the tandem compressors is brought online, and to identify a refrigeration system fault based on an expected change in the operating condition when each of the tandem compressors is brought online,

wherein the controller updates the control algorithm such that the control algorithm is no longer dependent on the malfunctioning refrigerant system component or function, the malfunctioning refrigerant system component being a compressor.

18. A refrigeration system comprising:

at least one compressor delivering refrigerant from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor, to a condenser positioned downstream of the compressor, to an expansion device positioned downstream of the condenser, and to an evaporator positioned downstream of the expansion device; and

a reheat circuit included in the refrigerant system, an operating condition of the reheat circuit being detected and provided to a controller, the controller comparing the detected condition to an expected condition while the reheat circuit is operating, and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold.

19. A refrigeration system comprising:

at least one compressor delivering refrigerant from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor, to a condenser positioned downstream of the compressor, to an expansion device positioned downstream of the condenser, and to an evaporator positioned downstream of the expansion device; and

a reheat circuit included in the refrigerant system, an operating condition of the reheat circuit being detected and provided to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is operating and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold,

wherein the reheat coil is positioned upstream of the condenser.

20. A refrigeration system comprising:

at least one compressor delivering refrigerant from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor, to a condenser positioned downstream of the compressor, to an expansion device positioned downstream of the condenser, and to an evaporator positioned downstream of the expansion device; and

a reheat circuit included in the refrigerant system, an operating condition of the reheat circuit being detected and provided to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is operating and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold,

wherein the reheat coil is positioned downstream of the condenser.

21. A refrigeration system comprising:

at least one compressor delivering refrigerant from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor, to a condenser positioned downstream of the compressor, to an expansion device positioned downstream of the condenser, and to an evaporator positioned downstream of the expansion device; and

a reheat circuit included in the refrigerant system, an operating condition of the reheat circuit being detected and provided to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is operating and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold,

wherein a bypass line around the condenser is included in the system design.

22. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online.

23. The method as set forth in claim 22, wherein at least one suction or discharge manifold is common to said tandem compressor bank.

24. The method as set forth in claim 22, wherein said refrigerant system fault is a compressor fault.

25. The method as set forth in claim 22, wherein each of said tandem compressors is brought online sequentially and expected changes in operating conditions are compared to detected changes.

26. The method of claim 22, wherein the operating condition is one of a suction pressure and a suction temperature.

27. The method of claim 22, wherein the operating condition is one of a discharge pressure and a discharge temperature.

28. The method of claim 22, wherein the operating condition is one of current and power draw.

29. The method as set forth in claim 22, wherein said tandem compressor bank includes two compressors.

30. The method as set forth in claim 22, wherein said tandem compressor bank includes more than two compressors.

31. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the working condition is one of an energy-saving pressure and an energy-saving temperature.

32. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the refrigeration system further has a variable speed drive for at least one of the tandem compressors, operating conditions being monitored when the variable speed drive changes the speed of the motor for the at least one of the tandem compressors, the monitored conditions being compared to expected conditions when the speed changes to identify the fault in the variable speed compressor.

33. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein a bypass line is provided around the condenser, and the controller monitors a cooling condition when the bypass line is operated, and determines whether the malfunction is a malfunction in a bypass function by comparing the detected cooling condition with an expected cooling condition.

34. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the refrigeration system includes an economizer cycle, the economizer cycle being operated, and an operating condition being detected and provided to the controller, the controller comparing the detected operating condition to an expected operating condition while the economizer cycle is operating, and identifying a fault in an economizer function if the expected condition and the detected condition differ by more than a predetermined threshold.

35. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the refrigerant system includes an unloader function, the unloader function being operated, and an operating condition being detected and provided to the controller, the controller comparing the detected operating condition to an expected operating condition when the unloader function is operating, and identifying a fault in the unloader function if the expected condition and the detected condition differ by more than a predetermined threshold.

36. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the refrigerant system includes a reheat circuit, the reheat circuit being operated, and an operating condition being detected and provided to the controller, the controller comparing the detected operating condition to an expected operating condition when the reheat circuit is operating, and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold.

37. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the controller updates the control algorithm such that the control algorithm is no longer dependent on the malfunctioning refrigerant system component or function.

38. A method of operating a refrigeration system comprising:

providing a tandem compressor bank including a plurality of compressors receiving refrigerant from a suction manifold, compressing the refrigerant, and delivering the refrigerant into a discharge manifold; a condenser positioned downstream of the compressor package; an expansion device positioned downstream of the condenser; and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor train to the condenser, through the expansion device to the evaporator, and back to the suction manifold; and

at least one sensor for detecting an operating condition of the refrigeration system, and a controller for monitoring the operating condition while each of the tandem compressors is brought online and identifying a refrigeration system fault based on the expected change and the detected change in the operating condition while each of the tandem compressors is brought online,

wherein the controller updates the control algorithm such that the control algorithm is no longer dependent on the malfunctioning refrigerant system component or function, the malfunctioning refrigerant system component being a compressor.

39. A method of operating a refrigeration system comprising the steps of:

providing at least one compressor, a condenser positioned downstream of the set of compressors, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor; and

providing a reheat circuit included in the refrigerant system, detecting an operating condition of the reheat circuit and providing the operating condition to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is operating, and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold.

40. A method of operating a refrigeration system comprising the steps of:

providing at least one compressor, a condenser positioned downstream of the set of compressors, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor; and

providing a reheat circuit included in the refrigerant system, detecting an operating condition of the reheat circuit and providing the operating condition to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is in operation and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold,

wherein the reheat coil is positioned upstream of the condenser.

41. A method of operating a refrigeration system comprising the steps of:

providing at least one compressor, a condenser positioned downstream of the set of compressors, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor; and

providing a reheat circuit included in the refrigerant system, detecting an operating condition of the reheat circuit and providing the operating condition to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is in operation and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold,

wherein the reheat coil is positioned downstream of the condenser.

42. A method of operating a refrigeration system comprising the steps of:

providing at least one compressor, a condenser positioned downstream of the set of compressors, an expansion device positioned downstream of the condenser, and an evaporator positioned downstream of the expansion device, the refrigerant passing from the compressor to the condenser, through the expansion device to the evaporator, and back to the compressor; and

providing a reheat circuit included in the refrigerant system, detecting an operating condition of the reheat circuit and providing the operating condition to a controller, the controller comparing the detected condition to an expected condition when the reheat circuit is in operation and identifying a fault in the reheat circuit if the expected condition and the detected condition differ by more than a predetermined threshold,

wherein a bypass line around the condenser is included in the system design.