COOLING SYSTEM WITH DUAL REFRIGERANT CONDENSING ZONES

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. Application Number 63/716,071 filed November 4, 2024, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0001] The present disclosure relates generally to refrigerant based cooling systems for data centers and the like, and more particularly, to a cooling system including dual pressure zones for precise ambient temperature control.

BACKGROUND

[0002] Traditional refrigerant based cooling systems operate by repeatedly pressurizing and depressurizing a refrigerant to reject and absorb heat. In a traditional cooling circuit, refrigerant is pressurized in a compressor, rejects heat in a condenser, is depressurized by a metering agent, and absorbs heat in an evaporator.

[0003] Cooling systems that utilize a cooling circuit can be used to transfer heat from one location to another. For example, in a data center, a cooling circuit can be used to cool electronic equipment by transferring heat from inside a building to outside a building, from one space to another, etc. Cooling system performance depends on the relatedness of pressure, volume, and temperature. As such, optimal cooling system performance requires precise pressure and temperature control. In outside environments where ambient temperature may be low and in some cases below freezing, it becomes necessary to control supply temperature to within a target range to ensure good evaporator performance. Controlling supply temperature during low ambient conditions becomes exceedingly difficult in large component and large capacity cooling systems.

[0004] Therefore, what is needed is a cooling system with precise ambient temperature control.

SUMMARY

[0005] According to one aspect, the present disclosure is directed to a cooling system including a cooling circuit configured to circulate a refrigerant. In embodiments, the cooling circuit includes a first refrigerant condensing line including a condenser, a second refrigerant condensing line bypassing the condenser, and a remix chamber disposed in the cooling circuit at a junction of the first and second refrigerant condensing lines. In a first operating mode of the cooling system, liquid refrigerant is supplied to the remix chamber from the first refrigerant condensing line. In a second operating mode of the cooling system, liquid refrigerant and vapor refrigerant are supplied to the remix chamber from the respective first and second refrigerant condensing lines and remix in the remix chamber to increase pressure/temperature of liquid refrigerant supplied to at least one evaporator.

[0006] In some embodiments, the first operating mode corresponds to a normal ambient temperature operating mode in which ambient temperature is within a predefined ambient temperature range, the second operating mode corresponds to a low ambient temperature operating mode in which ambient temperature is below the predefined ambient temperature range, and refrigerant supplied from the second refrigerant condensing line is at higher pressure and temperature than refrigerant supplied from the first refrigerant condensing line.

[0007] In some embodiments, the cooling system further includes a directional valve (e.g., 3-way valve) disposed in the cooling circuit at a division of the first and second refrigerant condensing lines, the directional valve configured to control refrigerant flow through each of the first and second refrigerant condensing lines.

[0008] In some embodiments, the cooling system further includes a compressor disposed in the cooling circuit upstream of the first and second refrigerant condensing lines, the compressor configured to pressurize the refrigerant.

[0009] In some embodiments, the cooling system further includes at least one pump disposed in the cooling circuit.

[0010] In some embodiments, the cooling system further includes at least one metering device disposed in the cooling circuit downstream of the remix chamber, and at least one evaporator disposed in the cooling circuit downstream of the at least one metering device.

[0011] In some embodiments, the first refrigerant condensing line is sub-divided into first and second flow lines entering the remix chamber wherein each of the first and second flow lines includes a flow control valve, the first flow line is open and the second flow line is closed when the cooling system is operating in the first operating mode, and the first flow line is closed and the second flow line is open when the cooling system is operating in the second operating mode.

[0012] In some embodiments, the cooling system further includes a pump disposed in the first refrigerant condensing line downstream of the condenser, and a bypass flow line disposed in the first refrigerant condensing line bypassing the pump, the bypass flow line including a check valve.

[0013] In some embodiments, the cooling system further includes a controller for operating the cooling system in the first operating mode or the second operating mode depending on ambient temperature.

[0014] According to another aspect, the present disclosure is directed to a cooling system including a cooling circuit configured to circulate a refrigerant and including a first refrigerant condensing line and a second refrigerant condensing line, a compressor disposed in the cooling circuit upstream of the first and second refrigerant condensing lines and configured to pressurize the refrigerant, a condenser disposed in the first refrigerant condensing line, a remix chamber disposed in the cooling circuit at a junction of the first and second refrigerant condensing lines, at least one metering device disposed in the cooling circuit downstream of the remix chamber, and at least one evaporator disposed in the condensing circuit downstream of the at least one metering device. In a first operating mode of the cooling system, liquid refrigerant is supplied to the remix chamber from the first refrigerant condensing line. In a second operating mode of the cooling system, liquid refrigerant and vapor refrigerant are supplied to the remix chamber from the respective first and second refrigerant condensing lines and remix in the remix chamber.

[0015] According to a further aspect, the present disclosure is directed to a cooling system including a cooling circuit configured to circulate a refrigerant and including a first refrigerant condensing line and a second refrigerant condensing line, a condenser disposed in the first refrigerant condensing line, at least one pump disposed in the cooling circuit, a remix chamber disposed in the cooling circuit at a junction of the first and second refrigerant condensing lines, at least one metering device disposed in the cooling circuit downstream of the remix chamber, and at least one evaporator disposed in the condensing circuit downstream of the at least one metering device. In a first operating mode of the cooling system, liquid refrigerant is supplied to the remix chamber from the first refrigerant condensing line. In a second operating mode of the cooling system, liquid refrigerant and vapor refrigerant are supplied to the remix chamber from the respective first and second refrigerant condensing lines and remix in the remix chamber.

[0016] This summary is provided solely as an introduction to subject matter that is fully described in the following detailed description and drawing figures. This summary should not be considered to describe essential features nor be used to determine the scope of the claims. Moreover, it is to be understood that both the foregoing summary and the following detailed description are explanatory only and are not necessarily restrictive of the subject matter claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Implementations of the present disclosure disclosed herein may be better understood when consideration is given to the following detailed description thereof. Such description refers to the included drawings, which are not necessarily to scale, and in which some features may be exaggerated and some features may be omitted or may be represented schematically in the interest of clarity. Like reference numerals in the drawings may represent and refer to the same or similar element, feature, or function. In the drawings:

[0018]FIG. 1A is a schematic diagram of a compressor-based cooling system shown in a first operating mode, in accordance with an example embodiment of the present disclosure;

[0019]FIG. 1B is a schematic diagram of the compressor-based cooling system of FIG. 1A shown operating in a second operating mode, in accordance with an example embodiment of the present disclosure;

[0020]FIG. 2A is a schematic diagram of a pump-based cooling system shown operating in a first operating mode, in accordance with an example embodiment of the present disclosure;

[0021]FIG. 2B is a schematic diagram of the pump-based cooling system of FIG. 2A shown operating in a second operating mode, in accordance with an example embodiment of the present disclosure;

[0022]FIG. 3A is a schematic diagram of a further pump-based cooling system shown operating in a first operating mode, in accordance with an example embodiment of the present disclosure;

[0023]FIG. 3B is a schematic diagram of the further pump-based cooling system of FIG. 3A shown in a second operating mode, in accordance with an example embodiment of the present disclosure; and

[0024]FIG. 4 is a flow diagram illustrating methodology for operating the cooling system, in accordance with an example embodiment of the present disclosure.

DETAILED DESCRIPTION

[0025] Before explaining one or more embodiments of the disclosure in detail, it is to be understood that the embodiments are not limited in their application to the details of construction and the arrangement of the components or steps or methodologies set forth in the following description or illustrated in the drawings. In the following detailed description of embodiments, numerous specific details may be set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art having the benefit of the instant disclosure that the embodiments disclosed herein may be practiced without some of these specific details. In other instances, well-known features may not be described in detail to avoid unnecessarily complicating the instant disclosure.

[0026] As used herein a letter following a reference numeral is intended to reference an embodiment of the feature or element that may be similar, but not necessarily identical, to a previously described element or feature bearing the same reference numeral (e.g., 1, 1a, 1b). Such shorthand notations are used for purposes of convenience only and should not be construed to limit the disclosure in any way unless expressly stated to the contrary.

[0027] Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present), and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0028] In addition, the use of “a” or “an” may be employed to describe elements and components of embodiments disclosed herein. This is done merely for convenience and “a” and “an” are intended to include “one” or “at least one,” and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0029] Finally, as used herein any reference to “one embodiment” or “embodiments” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment disclosed herein. The appearances of the phrase “in embodiments” in various places in the specification are not necessarily all referring to the same embodiment, and embodiments may include one or more of the features expressly described or inherently present herein, or any combination or sub-combination of two or more such features, along with any other features which may not necessarily be expressly described or inherently present in the instant disclosure.

[0030] Broadly, the present disclosure is directed to refrigerant based cooling systems with operating modes for normal ambient and low ambient conditions. System variants include, but are not limited to, compressor-based and pump-based cooling systems. Each cooling system generally includes a cooling circuit including a first refrigerant condensing line including a condenser, and a second refrigerant condensing line bypassing the condenser. The two refrigerant condensing lines may be arranged in parallel such that, when the cooling system is operating in the first operating mode corresponding the normal ambient condition, refrigerant condenses along the first refrigerant condensing line, and when the cooling system is operating in the second operating mode corresponding to a low ambient condition, refrigerant condenses along each of the first and second refrigerant condensing lines and remixes at a junction of the two condensing lines. In embodiments, remix of liquid refrigerant supplied from the first condensing line and vapor refrigerant supplied from the second condensing line can be used to condition (e.g., increase pressure and temperature) the liquid refrigerant supplied to at least one downstream evaporator. In embodiments, refrigerant flow through the first and second refrigerant condensing lines is controllable via a directional valve and control methodology.

[0031] In embodiments, the first refrigerant condensing line may correspond to a first pressure zone, and the second condensing line may correspond to a second pressure zone. In embodiments, the first pressure zone including the condenser may be considered the ‘low’ pressure zone, whereas the second pressure zone bypassing the condenser may be considered the ‘high’ pressure zone, wherein the terms ‘low’ and ‘high’ are comparative and not determinative of any quantified pressure or pressure range. The remixed refrigerant can be infinitely condition controlled by actuating the control valve to adjust the flow of vapor refrigerant supplied to the remix chamber.

[0032] The term “normal” as used herein in connection with ambient condition may mean an ambient condition (e.g., temperature) within a predefined target range in which the liquid refrigerant supplied by the first refrigerant condensing line has a saturation pressure and temperature sufficient for good evaporator control. The term “low” as used herein in connection with ambient condition may mean an ambient condition (e.g., temperature) below the predefined target range in which the liquid refrigerant supplied by the first refrigerant condensing line has a saturation pressure and temperature insufficient for good evaporator control, and therefore requires conditioning (e.g., pressure and temperature increase) from a remix of liquid refrigerant from the first refrigerant condensing line and vapor refrigerant from the second refrigerant condensing line. In embodiments, the mixture of refrigerant in the remix chamber from the first and second refrigerant condensing lines equilibrates to a liquid refrigerant at the ideal saturation pressure and temperature for good evaporator control.

[0033]FIGS. 1A and 1B illustrate a compressor-based cooling system 100 according to a first embodiment of the present disclosure. The cooling system 100 includes a cooling circuit 102 configured to circulate refrigerant. Suitable refrigerants may include, but are not limited to, R22, R410A, R407C, R744, R134a, R1234yf, R290, R600a, R718, and R454B, among other refrigerants. The cooling circuit 102 generally includes at least one compressor 104 configured to pressurize the refrigerant, at least one condenser 106 configured to reject heat from the refrigerant, at least one metering device 108 configured to depressurize the refrigerant, and at least one evaporator 110 configured to absorb heat in the refrigerant. The directional arrows shown in the drawing depict the flow of refrigerant through the various line set and supply lines of the cooling circuit 102. In use, the circulated refrigerant is repeatedly pressurized and depressurized to respectively release and absorb heat.

[0034] The cooling circuit 102 includes separate pressure zones implemented as a first refrigerant condensing line 112 (or path) including the at least one condenser 106, and a second refrigerant condensing line 114 (or path) bypassing the at least one condenser 106. In embodiments, the first and second refrigerant condensing lines 112, 114 are arranged in parallel, and the division of the first and second refrigerant condensing lines 112, 114 is provided by a flow divider 116 (e.g., directional flow control valve) disposed in the cooling circuit 102 downstream of the at least one compressor 104 and upstream of the at least one condenser 106. The flow divider 116 may be, for example, a 3-way valve including an inlet for entering high pressure/high temperature vapor refrigerant supplied by the at least one compressor 104, a first outlet for exiting the high pressure/high temperature vapor refrigerant to the first refrigerant condensing line 112, and a second outlet for exiting the high pressure/high temperature vapor refrigerant to the second refrigerant condensing line 114.

[0035] In embodiments, the flow divider 116 may function as a flow controller for each of the first and second refrigerant condensing lines 112, 114, or as a flow controller for the second refrigerant condensing line 114 and a pass-thru for the first refrigerant condensing line 112. In other words, in embodiments, the first refrigerant condensing line 112 is maintained open to continuously generate supply of condensed liquid refrigerant while the second refrigerant condensing line 112 is selectively opened or closed depending on the operating mode of the cooling system 100 as described in detail below.

[0036] The cooling system 100 further includes a remix chamber 118 disposed in the cooling circuit 102 at a junction of the first and second refrigerant condensing lines 112, 114. The remix chamber 118 includes at least one inlet for entering high pressure/high temperature liquid refrigerant supplied from the first refrigerant condensing line 112, and at least one inlet for entering high pressure/high temperature vapor refrigerant supplied from the second refrigerant condensing line 114. The remix chamber 118, which may be implemented as a tank, a pipe, or other structure, is configured to receive a supply of refrigerant from one or more of the first and second refrigerant condensing lines 112, 114 depending on the operating mode of the cooling system 100.

[0037] In embodiments, the cooling system 100 is configured to operate in a first operating mode or a second operating mode depending on ambient conditions and/or the need to condition the liquid refrigerant for good evaporator control (e.g., increase pressure and temperature). In the first operating mode illustrated in FIG. 1A, when ambient conditions are such that the pressure and temperature of the high pressure/high temperature liquid refrigerant supplied from the at least one condenser 106 are ideal for good evaporator control, the directional flow control valve 116 may be actuated to close the outlet to the second refrigerant condensing line 114 such that no vapor refrigerant is supplied to the remix chamber 118. In the first operating mode, the remix chamber 118 may fill with liquid refrigerant from the first refrigerant condensing line 112 to be supplied to the downstream at least one metering device 108.

[0038] In the second operating mode illustrated in FIG. 1B, when ambient conditions are such that the pressure and temperature of the high pressure/high temperature liquid refrigerant supplied from the at least one condenser 106 are less than ideal or unsuitable for good evaporator control, the directional flow control valve 116 is actuated to open the outlet to the second refrigerant condensing line 114 such that both liquid refrigerant from the first refrigerant condensing line 112 and vapor refrigerant from the second refrigerant condensing line 114 are supplied to the remix chamber 118 where the liquid refrigerant is equilibrated to an ideal pressure and temperature at the higher pressure zone. In embodiments, the ratio of liquid refrigerant to vapor refrigerant is precisely controlled by the flow divider 116 to achieve an ideal saturation pressure and temperature depending on the liquid temperature. For example, the flow of vapor refrigerant along the second refrigerant condensing line 114 may be increased as the ambient temperature decreases further below a predefined ambient temperature range (e.g., target ambient temperature range), and may be decreased as the ambient temperature increases from a low level toward the predefined ambient temperature range.

[0039] In embodiments, the cooling system 100 may further include at least one pump 120 disposed in the first refrigerant condensing line 112, and at least one pump bypass line 122 for bypassing the at least one pump 120 when the at least one pump 120 is turned off. As shown in FIG. 1A, when the cooling system 100 is operating in the first operating mode with the second refrigerant condensing line 114 ‘closed,’ the at least one pump 120 may be turned off causing the high pressure/high temperature liquid refrigerant from the at least one condenser 106 to bypass the at least one pump 120 via the bypass line 122. In embodiments, a check valve 124 may be disposed in the bypass line 122 for preventing backflow of the liquid refrigerant. As shown in FIG. 1B, when the cooling system 100 is operating in the second operating mode with the second refrigerant condensing line 114 ‘open,’ the at least one pump 120 may be turned on as needed to increase pressure to mitigate the decrease in system pressure resulting from opening the second refrigerant condensing line 114.

[0040] In embodiments, the first refrigerant condensing line 112 may further include a division upstream of the remix chamber 118 including a valve-controlled standard line 126 and valve-controlled backpressure line 128. When the cooling system 100 is operating in the first operating mode as illustrated in FIG. 1A, the standard line 126 may be open and the backpressure line 128 may be closed considering the at least one pump 120 is turned off. When the cooling system 100 is operating in the second operating mode as illustrated in FIG. 2B, the standard line 126 may be closed and the backpressure line 128 may be opened considering the at least one pump 120 is turned on. In other words, when the directional flow control valve 116 opens the second refrigerant condensing line 114, a pressure differential is created between the inlet flow to the second refrigerant condensing line 114 and the inlet flow to the first refrigerant condensing line 112. The bypass refrigerant flow along the second refrigerant condensing line 114, in vapor state, proceeds to the remix chamber 118. At the same time, the at least one pump 120 is now on and the backpressure valve disposed in the backpressure line 128 operates. The flow along the first refrigerant condensing line 112 may see normal low ambient fan control utilized. The ‘colder’ liquid from the first refrigerant condensing line 112 with a sub-cool if at the bypass flow pressure (i.e., colder than the bypass flow saturation pressure/temperature) is mixed with the bypass vapor flow from the second refrigerant condensing line 114. The mixture of liquid refrigerant and vapor refrigerant equilibrates to the ideal saturation pressure and temperature for good evaporator control.

[0041] The liquid refrigerant supplied from the remix chamber 118 flows to and is depressurized by the at least one metering device 108, such as an electronic expansion valve (EEV), thermostatic expansion valve, fixed-bore piston, capillary tube, etc. In use, the at least one metering device 108 depressurizes the liquid refrigerant and delivers a cooled liquid/vapor mixture to the at least one evaporator 110 which then absorbs heat from the surrounding environment, for example from an environment containing heat generating electronic equipment. As shown, the cooling system 110 may include at least two parallel metering devices 108 and evaporators 110 depending on the application.

[0042] The cooling system 100 operates in the first operating mode (FIG. 1A) when the supply fluid temperature at the at least one evaporator 110 is at a target value or within a target range (e.g., normal ambient temperature), and operates in the second operating mode when the supply fluid temperature at the at least one evaporator 110 is below the target value or target range (e.g., low ambient temperature). In the second operating mode, the condenser fans may be off or cycle on and off as needed. In embodiments, most of the flow is through the first refrigerant condensing line 112 and the system pressure is maintained similar to the compressor discharge target range by the at least one pump 120 configured to increase flow pressure with the use of the backpressure valve disposed in the liquid line.

[0043]FIGS. 2A and 2B illustrate a pump-based cooling system 200 according to a second embodiment of the present disclosure. The pump-based cooling system 200 is like the compressor-based cooling system 100 described above with the difference being that the refrigerant flow is pumped without lift from a compressor. In this configuration, ambient conditions may be low enough such that refrigerant is condensed by economization. Much of the cooling circuit 102 is the same as that described above and therefore is not repeated in this section.

[0044] In the cooling system 200, when operating in the first operating in the first operating mode as illustrated in FIG. 2A, liquid refrigerant formed in the at least one condenser 106 is pumped through the at least one pump 120 to pressurize and move the liquid refrigerant through the standard line 126 and into the remix chamber 118. The liquid refrigerant exiting the remix chamber 118 travels along a valve-controlled standard line 130 bypassing at least one lift pump 132 that may be utilized in the second operating mode and /or where at least one lift pump 132 is needed to raise the pressure of the liquid refrigerant exiting the remix chamber 118 to a pressure sufficient to drive the flow of liquid refrigerant through the at least one metering device 108. For example, at least one lift pump 132 may be needed when the at least one evaporator 110 and metering devices 108 are elevated above the remix chamber 118.

[0045] The cooling system 200 may operate in the second operating mode, as illustrated in FIG. 2B, when the ambient air temperature is low enough that refrigerant temperatures and saturation pressures at the at least one evaporator 110 (e.g., heat sink) is out of target range. In the second operating mode, condenser fans may be low and/or cycled off. In this operating mode, the flow divider 116 directs at least a portion of the refrigerant flow to the second refrigerant condensing line 114 such that vapor refrigerant supplied from the second refrigerant condensing line 114 mixes with ‘cold’ liquid refrigerant supplied from the lower pressure first refrigerant condensing line 112. When the ambient temperature is too low, the liquid refrigerant flowing through first refrigerant condensing line 112 condenses and cools at a lower saturation pressure and temperature than ideal for good evaporator control, and therefore the at least one pump 120 is turned on to increase liquid pressure sufficiently to remix with the vapor refrigerant from the second refrigerant condensing line 114. In the second operating mode, as mentioned above, at least one lift pump 132 may be turned on to increase the pressure of the remixed liquid refrigerant flowing to the at least one metering device 108. By utilizing the at least one lift pump 132 to increase the pressure, substantially the same pressure upstream and downstream of the remix chamber 118 can be maintained.

[0046]FIGS. 3A and 3B illustrate a further pump-based cooling system 300 according to a third embodiment of the present disclosure. The pump-based cooling system 300 is like the pump-based cooling system 200 described above but does not include a lift pump to increase pressure. This further pump-based cooling system 300 may be utilized, for example, when the remix chamber 118 is positioned elevated above the at least one evaporator 110 and metering device 108.

[0047] Each of the cooling systems 100, 200, 300 may further include a controller 150 configured to control one or more of the directional valves and pumps. In embodiments, the controller 150 may be a secondary controller or part of the primary system controller and communicatively coupled to at least one temperature sensor configured to sense and report at least one of ambient temperature and liquid temperature entering the at least one evaporator 108. Based on the inputs received, the controller 150 may be configured to operate the cooling systems 100, 200, 300 according to the first or second operating mode depending on the condition of the condensed refrigerant. In some embodiments, the controller 150 may be configured to operate the cooling systems 100, 200, 300 in the first operating mode when the liquid temperature is within a predefined target range, and operate the cooling systems 100, 200300 in the second operating mode when the liquid temperature falls below the predefined target range.

[0048] In embodiments, the controller 150 may include one or more processors and a memory device, or memory. For example, the one or more processors may be configured to execute a set of program instructions maintained in the memory device. The one or more processors may include any processor or processing element known in the art. For the purposes of the present disclosure, the term “processor” or “processing element” may be broadly defined to encompass any device having one or more processing or logic elements (e.g., one or more micro-processor devices, one or more application specific integrated circuit (ASIC) devices, one or more field programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, the one or more processors may include any device configured to execute algorithms and/or instructions (e.g., program instructions stored in memory). Moreover, different subsystems of the present disclosure may include a processor or logic elements suitable for carrying out at least a portion of the steps described herein. Further, the steps described herein may be carried out by a single controller or, alternatively, multiple controllers. Further, the controller may analyze or otherwise process data received from the sensors and feed the data to additional components or external to the system.

[0049] The memory device may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors. For example, the memory device may include a non-transitory memory medium. As an additional example, the memory device may include, but is not limited to, a read-only memory, a random-access memory, a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid-state drive and the like. It is further noted that the memory device may be housed in a common controller housing with the one or more processors.

[0050]FIG. 4 illustrates a control methodology 400 for operating the cooling systems 100, 200, 300 in the first or second operating modes. In Step 402, the method includes providing a cooling system 100, 200, 300 including the first and second refrigerant condensing lines 112, 114, remix chamber 118, etc. In Step 404, a system controller receives data (e.g., continuously or according to a predefined time interval) pertaining to at least one of ambient temperature and temperature of the condensed liquid supplied to the at least one evaporator 110. In Step 406, based on the received temperature data, the system controller 150 actuates the flow divider 116 to control the supply of vapor refrigerant supplied to the remix chamber 118 to operate the cooling system in the first or second operating mode. In Step 408, the controller 150 cycles the at least one pump 120 ‘on’ or ‘off’ depending on the operating mode and/or liquid pressure in the system. In an optional Step 410, the controller 150 controls further valves and pumps depending on the system configuration and operating mode.

[0051] From the above description, it is clear that the present disclosure disclosed herein is well adapted to achieve the objectives and to attain the advantages mentioned herein as well as those inherent in the present disclosure disclosed herein. While exemplary embodiments of the present disclosure disclosed herein has been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the broad scope and coverage of the present disclosure disclosed and claimed herein.