Apparatus and method for hybrid water heating and air cooling and control thereof

MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY

APPARATUS AND METHOD FOR WATER HEATING AND COOLING OF

HYBRID AIR AND CONTROL

BACKGROUND OF THE INVENTION

Various apparatus and methods have been previously proposed for preheating water in a water heater or water storage tank using refrigerant from an air conditioner such as an air conditioner with a non-reversible refrigerant circuit, a heat pump for a of residential air conditioning that has a reversible refrigerant circuit, and a commercial rooftop unit (RTU) system that operates in an air-cooled-only mode but has a setting to alternately direct refrigerant flow from a compressor to an air-cooled condenser or to an air-cooled condenser. water/heat exchanger that exchanges heat from a refrigerant used to provide cooled air to an interior of a commercial building to the water in the commercial building's water heating system.

BRIEF DESCRIPTION OF THE INVENTION

The present invention recognizes and addresses several disadvantages of prior art constructions and methods.

In one embodiment, a system for conditioning air and

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY for heating water includes a first refrigerant path and a second refrigerant path that is independent of the first refrigerant path. A first condenser in the first refrigerant path and the second refrigerant path is arranged in an air flow such that the first condenser transfers heat to the air in the air flow path from the refrigerant in the first refrigerant path which is moves through the first condenser and transfers heat to the air from the refrigerant in the second refrigerant path moving through the first condenser. A second condenser in the first refrigerant path defines a water flow path such that the second condenser transfers heat to the water in the water flow path from the refrigerant in the first refrigerant path moving through the second condenser . A control system in operative communication with the first refrigerant path is configured to direct refrigerant in the first refrigerant path, in a first state of the first refrigerant path, to the first condenser and not to the second condenser and, in a second state of the first refrigerant path, to the second condenser. The control system is configured to determine a condition under which the system activates the first coolant path and deactivates the second coolant path, and to move the first coolant path from the second state to the first state in response to the condition. .

In another embodiment, an air conditioning and water heating system includes a first refrigerant path and a second refrigerant path that is independent of the first refrigerant path. A first condenser in the first refrigerant path and the second refrigerant path is arranged in a first airflow path such that the first condenser transfers heat to the air in the airflow path from the refrigerant in the first airflow path. refrigerant moving through the first condenser and transferring heat to the air from the refrigerant in the second path of refrigerant moving through the first condenser. An evaporator in the first refrigerant path and the second refrigerant path is arranged in a second airflow path so that the air in the second airflow path transfers heat to the refrigerant moving through the evaporator; A second condenser in the first refrigerant path defines a water flow path so

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MEXICAN INSTITUTE

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INDUSTRIAL that the second condenser transfers heat to the water in the water flow path from the refrigerant in the first refrigerant path moving through the second condenser. A control system has a controllable valve in the first refrigerant path in communication with the first condenser and the second condenser such that the controllable valve selectively directs the refrigerant in the first refrigerant path to either the first condenser or the second condenser.

The control system is configured to actuate the controllable valve in at least a first state and a second state. The controllable valve, in the first state, directs the refrigerant in the first refrigerant path to the first condenser and not to the second condenser and, in the second state, directs the refrigerant in the first refrigerant path to the second condenser. The control system is configured to determine a condition that requires refrigerant movement in the first refrigerant path and does not require refrigerant movement in the second refrigerant path, and to control the controllable valve to move from a second state to the first state in response to the condition.

In yet another embodiment, a system for conditioning air

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL and for heating water has a first refrigerant path, a second refrigerant path that is independent of the first refrigerant path, and a first condenser in the first refrigerant path and the second refrigerant path. A first fan is arranged with respect to the first condenser to move the first air through the first condenser so that the first condenser transfers heat to the first air from the refrigerant in the first path of refrigerant moving through the first condenser and transferring heat to the first air from the refrigerant in the second refrigerant path moving through the first condenser. An evaporator is located in the first refrigerant path and the second refrigerant path. A second fan is arranged with respect to the evaporator to move the second air through the evaporator so that the evaporator transfers heat from the second air to the refrigerant in the first path of refrigerant moving through the evaporator and to the refrigerant in the second. path of refrigerant moving through the evaporator. A first compressor is located in the first refrigerant path and is configured to move refrigerant in the first refrigerant path. A second compressor is located in the second

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY coolant path and is configured to move the coolant in the second coolant path. A second condenser in the first refrigerant path defines a water flow path such that the second condenser transfers heat to the water in the water flow path from the refrigerant in the first refrigerant path moving through the second condenser . A control system has a controllable valve in the first refrigerant path in communication with the first compressor, the first condenser and the second condenser such that the controllable valve selectively directs refrigerant from the first compressor to the first condenser or the second condenser. second capacitor. A sensor is disposed with respect to the first coolant path such that the sensor produces a signal corresponding to the pressure in the first coolant path. The control system is in operational communication with the first compressor to turn the first compressor on and off, the second compressor to turn the second compressor on and off, and the sensor. The control system is configured to actuate the controllable valve in at least a first state and a second state. The controllable valve, in the first state, directs the refrigerant from the first compressor to the

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MEXICAN INSTITUTE

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INDUSTRIAL first condenser and not to the second condenser and, in the second state, directs the refrigerant from the first compressor to the second condenser and not to the first condenser. The control system is set to, when the first compressor turns on and the second compressor turns on, and when the controllable valve is in the second state, turn off the first compressor when the pressure sensor signal indicates that the refrigerant pressure in the first refrigerant path is greater than a first pressure. The control system is also configured to, when the first compressor turns on and the second compressor turns off, and when the controllable valve is in the second state, to control the controllable valve to move from the second state to the first state. when the pressure sensor signal indicates that the refrigerant pressure in the first refrigerant path is greater than a second pressure that is less than the first pressure.

Other objects, features, and aspects of the present invention may be achieved by various combinations and subcombinations of the described elements, which are discussed in greater detail below.

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL

BRIEF DESCRIPTION OF THE FIGURES

Aspects of the present invention can be better understood with reference to the following drawings. Components in the drawings are not necessarily to scale. A facilitating description of the present invention, including a best mode thereof, is set forth in the specification, which makes reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of a building having a water storage, heating, and usage system, an indoor space, and an air conditioning system in communication with the indoor space for supplying air conditioning thereto, according to an embodiment of the present invention.

Figure 2 is a schematic illustration of one embodiment of the air conditioning system illustrated in Figure 1.

Figure 3 is a schematic illustration of an air conditioning system illustrated in Figure 2.

Figure 4 is a schematic illustration of an air conditioning system illustrated in Figure 2.

Figure 5 is a schematic illustration of an air conditioning system illustrated in Figure 2.

Figure 6 is a schematic illustration of an air conditioning system as shown in Figure 1.

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY

Figure 7 is a flow chart illustrating the operation of the air conditioning systems illustrated in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6.

Figure 8 is a flow diagram illustrating the operation of air conditioning systems as illustrated in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6; Y

Figure 9A and Figure 9B are a flow chart illustrating the operation of air conditioning systems as illustrated in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6.

Repeated use of reference characters in this specification and drawings is intended to represent the same or analogous features or elements of embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. Indeed, it will be apparent to those of skill in the art that modifications and variations may be made to such examples without departing from the scope or spirit thereof. For example, features illustrated or described as part of one embodiment may be used in another embodiment to produce an additional embodiment. Thus, it is intended that the present invention cover such modifications and variations as fall within the scope of the appended claims and their equivalents.

As used herein, the terms apparatus, air conditioning system, etc., encompass apparatus suitable for changing the temperature of air delivered to a conditioned space and having an associated refrigerant circuit. Thus, an air conditioning appliance or system may comprise, without limitation, (1) an air conditioning unit or (air conditioner) having a nonreversible refrigerant circuit that can be used to cool air supplied to a space conditioned space, or (2) a heat pump that has a reversible refrigerant circuit that can be used to heat or cool air supplied to a conditioned space.

Furthermore, the term or as used in this application and the appended claims is intended to mean an inclusive or rather than an exclusive or. That is, to

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL unless otherwise specified, or is clear from the context, the phrase X employing A or B is intended to mean any of the natural inclusive permutations. That is, the sentence X employs A or B is satisfied by any of the following cases. X employs A; X uses B, or X uses both A and B. Furthermore, the items one and one used in this application and the appended claims should generally be construed to mean one or more unless otherwise specified or it is clear from the context that a singular form is intended. Throughout the specification and claims, the following terms take on at least the meanings explicitly associated therein, unless the context dictates otherwise. The meanings identified below do not necessarily limit the terms, but only provide illustrative examples for the terms. The meaning of one, an, and the may include plural references, and the meaning of in may include in and on. The phrase in a mode, as used herein, does not necessarily refer to any mode, although it could.

Various aspects or features will be presented in terms of systems which may include a number of devices, components, modules and the like. will be understood

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL and you will appreciate that various systems may include additional devices, components, modules, etc., and/or may include all of the devices, components, modules, etc., discussed in conjunction with the figures. A combination of these procedures can also be used.

Air conditioning systems capture heat at some point in the continuous refrigerant cycle and transfer heat to or remove heat from a structure, depending on whether the system operates in a cooling mode or, if it is capable of both modes, in a heating mode. To carry out the principles of one or more embodiments of the present invention, a portion of the heat may be captured and used to heat water that is supplied for end uses in a structure, such as a building, to which the system also provides air conditioning. In certain embodiments, the air conditioning system may provide hot water in a preliminary phase of the building's water heating system, at a temperature at or below a high set point temperature used by the water heater to maintain the water temperature. One or more electric elements or gas burners in the water heating system may provide additional heat to raise the water temperature to full flash point temperature.

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY high reference of the system.

An air conditioning/water heater system 10 incorporating the principles of one or more embodiments of the present invention is shown schematically in Figure 1 and includes an air conditioning system 12 which, in presently described embodiments, is a ceiling mounted type air conditioning system that can be used, for example, to condition the air in an interior space of a structure 18 such as a commercial building. Air conditioning system 12 is disposed on a roof 20 of building 18 and has a duct 22 extending from a main housing 24 of system 12 through roof 20 and into interior space 16. A fan 21 (FIG. 6) within housing 24 draws air 23 through duct 22 from space 16 to an evaporator coil 54 (FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6) which is disposed within of the housing 24 and which transfers heat from the hot air 23 from the interior space 16 to the refrigerant in the refrigerant circuit of the system, thus cooling the air which the air conditioning system then returns (as indicated at 25) to the interior space 16 through a second duct 26 extending from the housing 24 through the ceiling 20. As described in more detail below system 12 then cools

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MEXICAN INSTITUTE

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INDUSTRIAL subsequently the refrigerant into an air-cooled evaporator coil 4 6 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6), where the refrigerant transfers heat to ambient air 27 (Figure 6) drawn through the evaporator coil. evaporator by a second fan 29 (Figure 6).

At certain times when the system 10 requires hot water, the air conditioning system 12 switches the refrigerant cooling function from the air-cooled condenser to a heat exchanger coil 50 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) receiving water from a water storage tank 30 within a water heating system 38 of the building 18, so that the refrigerant transfers the heat to the water instead of the ambient air 27. In this way, the heat exchanger 50 can be considered as a water-cooled condenser. Tank 30 initially receives cold water (for example, ground temperature) from a cold water pipe 14 via a fitting 32 from a cold water source 31. Fitting 32 is a tee fitting that allows cold water to flow with based on pressure differences. When pump 52 is idle, and when water is drawn from storage tank 30, cold water flows into tank 30 from source 31. When pump 52 is active, and

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL When there is no request for cold water from source 31, the water in storage tank 30 flows through fitting 32 to pump 52 via line 14. When there is a request for cold water, pump 52 can draw all the ' cold water from source 31 or a combination of cold water from source 31 and tank 30 through pipe 14.

Upon activation, pump 52 draws initially cold water from tank 30 and/or source 31 via fitting 32 and directs the water to water-cooled condenser 50. After transferring refrigerant heat to water, the system 12 produces the now heated water from the heat exchanger through a second pipe 28 which supplies the heated water to the water storage tank 30 via a fitting 33. As described in more detail below, this cycle, of drawing water from tank 30 to the water-cooled condenser 50 which helps to heat the water, and returning the water to tank 30, is repeated, thereby increasing the temperature of the water in the condenser. tank to a target temperature. Although the construction of tank 30 may vary, in this example tank 30 may be a 115-gallon capacity porcelain-enameled tank having two-inch five-point-zero rigid foam insulation and a

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MEXICAN INSTITUTE

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INDUSTRIAL baked enamel steel sleeve, supplied under the model name STA 120 by Rheem Manufacturing, Inc., of Atlanta, Georgia.

When a dishwasher 34, faucets 36, or other fixtures or devices of the building 18 require hot water from one or more tankless water heater phases of the water heating system 38, a control circuit of the water heating system 35 controls relays (not shown) that open respective valves that allow preheated water from tank 30 to flow into respective tankless water heating phases of system 38, through line 40. As should be understood, the illustrated valves between expansion tank 41 and line 40 are normally closed. The tankless water heating system 38 heats the water to a final threshold temperature, for example, 60°C (140°F) or 79.4°C (185°F) and produces the final heated water to the water lines. heaters 42 that direct the heated water to the building 18, for example, the dishwasher or the taps. Since the water heating stages 38 draw water from the tank 30, the cold water source 31 refills the tank 30. This lowers the water temperature in the tank 30, but the heating function of the water-cooled condenser 50 continues to heat the tank water as

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL that the cycle described above is repeated. As indicated in Figure 1, the fitting 32 is located near the bottom of the tank 30. Since the coldest water in the tank is usually closer to the bottom of the tank, this allows the system to 12 contribute to the heating of the coldest water in the tank. As should be understood, an expansion tank 41 may be provided in the system to receive the tank water as it heats, and thus expands, in its normal operation without disrupting the pressure relief valves of the system.

Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6 schematically illustrate embodiments of an air conditioning system 12 incorporating one or more of the principles of the present invention. As seen from the foregoing, the system 12 includes an air-cooled condensing coil 46, a compressor (i.e., a pump) 48, and an evaporator coil 54. With the additional use of a plate-type heat exchanger (water-cooled condenser) 50 and water pump 52, the system 12 is arranged to operate in an air-cooled mode while providing refrigerant-based supplemental heat to the water. stored in the water tank 30 (FIG. 1). An electronic control system 56 (shown as

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MEXICAN INSTITUTE

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INDUSTRIAL schematic (shown only in Figure 2, but present in the systems of Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) controls the various functions of the air conditioning/water preheating system 12 and operates various subsequently described components thereof.

As should be understood, an air conditioning system may comprise, from a refrigerant flow standpoint, a closed loop of refrigerant flowing between the compressor, the condenser, and the evaporator. In so-called split systems, the evaporator is typically disposed within an enclosure that receives conditioned air from the conditioned space (eg, an interior building space such as space 16, shown in Figure 1), such as inside an air handler that draws recirculating indoor air through the evaporator. Because the evaporator is associated with indoor air, it is often referred to as an indoor coil, even though, as in currently described embodiments, its physical location may be either inside or outside the building the system serves. The condenser coil is typically located outside the conditioned space structure, where a fan draws ambient air through the condenser coil.

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MEXICAN INSTITUTE

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INDUSTRIAL condenser to remove heat from the refrigerant. In the outdoor ceiling-mounted system shown in these figures, both coils are arranged outside the conditioned space, but air from inside the space is directed, for example, through one or more ducts such as ducts 22 and 26. shown in Figure 1, from the interior space to the evaporator coil, and then back to space 16. However, regardless of physical location, the evaporator contributes to the heating of the refrigerant while the condenser produces heat gained from the refrigerant.

As will be understood, the refrigerant acquires heat in part from the air inside the evaporator as the liquid refrigerant evaporates in response to the influence of an expansion valve at the evaporator coil inlet. As the system's air handler fan moves recirculating building air through the evaporator coils, a change in phase of the refrigerant from liquid to gas removes energy (i.e., heat) from the indoor air, cooling thus the air as it is forced back into the conditioned space of the building. The hot refrigerant gas then flows from the evaporator coil to the compressor, which receives

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY the gas and pumps it back to the condenser, adding pressure and heat. The condenser cools the refrigerant thereby dissipating the heat gained from the refrigerant (from the evaporator and compressor) to the environment by the airflow that the fan moves through the coil, and the cooled refrigerant flows back to the evaporator. That is, the refrigerant flows from the compressor, to the condenser, to the evaporator, and back to the compressor.

As the condenser cools the refrigerant, the refrigerant phase changes from vapor to liquid, and its pressure drops due to friction within the heat exchanger. However, the refrigerant flow path length and tubing dimensions, and the size and resistance of the compressor, are selected so that sufficient positive and negative pressure remains at the condenser outlet and inlet to maintain refrigerant flow. in the evaporator and return it from the same to the compressor. The selection of such components and system and operating parameters to allow for the desired heat transfer and recirculating refrigerant flow through the flow loop must be understood in the art. Although it should be understood that the air conditioning systems described below are designed to

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provide sufficient heat transfer and pressure to maintain system operation, these variables are not further discussed herein.

One or more embodiments described herein are inserted toward the refrigerant path, the plate-type heat exchanger 50 which receives water from, or water that is otherwise intended for, the water heating system storage tank 30 of way that the heat exchanger transfers heat from the refrigerant to the water in the tank. In system operation, the water-cooled heat exchanger replaces the air-cooled condenser 46 in the air conditioning system's underlying compressor-condenser-evaporator-compressor sequence, but it should be understood that the partial bypass of refrigerant to the heat exchanger water-cooled heat is within the scope of the present description. Thus, although the present description mainly provides examples having an air-cooled condenser and a wholly water-cooled condenser in alternative to each other, it is to be understood that other arrangements fall within the present description.

Furthermore, although the embodiments currently described are discussed in the context of an air conditioning system

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY ceiling type, in which the condensers and the evaporator are located in the same housing, it should be understood that this description covers other air conditioning systems, for example, where the air-cooled condenser is arranged outside of the building or inside the building (with outside ambient air being supplied to the condenser), and where each of the water-cooled condenser and evaporator are located inside or outside the building.

Control system 56 may comprise a programmable logic controller (PLC) or other computer that operates as a general system controller for system 12. Housed, for example, within enclosure 24 (FIG. 1) of system 12, the PLC communicates with and controls (via appropriate wired or wireless electrical connections, relays, power supplies, and other electromechanical connections, as should be understood). in that art, the drive and operation of the components described herein, including but not limited to, compressors, air-cooled condenser fan, evaporator fan, the water pump, the three-way valve and all other electrically controlled valves and relays. As such, the control system communicates with and controls the operating components of the air conditioning system 12, which includes the valve system within the refrigerant flow path which, along with the compressors (also controlled by the control system ), control the flow of refrigerant. Reference to the connections between control system 56 and each of the components of air conditioning system 12, tank 30 (FIG. 1), and water heating system 38 (FIG. 1) encompass such communications and control. Such communication may also encompass communication between the control system and an ambient temperature sensor in system 12 that provides a signal to the control system that corresponds to the temperature of the surrounding environment of system 12. In addition, control system 56 receives input signals from one or more thermostats in the building's conditioned space that provide instructions (i.e., requests for cooling) regarding the decision to activate the air conditioning system in an operating mode. air cooling mode, turn off the air conditioning system from an air cooling mode, and operate the air handler. The thermostats, which are located in the conditioned space and which include a temperature sensor, can also produce a signal corresponding to the temperature of the conditioned space 16 (FIG. 1) to the control system. The operation of thermostats in generating instructions should be well understood and is therefore not discussed further here. The thermostats may be considered as part of the control system 56, and, in either case, the control system may share or perform functions typically performed by thermostats. Accordingly, reference herein to the various functions performed by the control system 56 may encompass the communications between the control system and the thermostats, as well as the communications between the control system and the system compressor 12, the condenser and evaporator fans, the water pump, valves and sensors, and between the control system and the water heating system. The control system activates and deactivates the system of its system components 12 based on the programming of the air conditioning system in response to signals from the thermostats, as it should be understood, and optionally signals from the sensors of the system 12 and /or the water heating system indicating the operating parameters of the system, as described herein. As discussed herein, actuation of the air conditioning system can refer to activation of the compressor to move refrigerant through the refrigerant path, activation of the condenser fan, and activation of the evaporator fan, in certain situations. modalities.

It will be understood from this description that the functions attributed to control system 56 may be embodied by computer-executable instructions from a program that runs on one or more PLCs or other computers that operate as the overall system controller for system 12. . Program modules generally include routines, programs, components, data structures, etc., that perform particular tasks and/or implement particular abstract data types. Furthermore, those skilled in the art will appreciate that the systems/methods described herein can be practiced with various controller configurations, including programmable logic controllers, simple logic circuits, single or multi-processor systems, as well as personal computers. , portable computing devices, microprocessor-based or programmable consumer or industrial electronic devices, and the like. Aspects of these functions can also be practiced in distributed computing environments, for example, in so-called intelligent systems and arrangements, where tasks are performed by remote processing devices that are linked via

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MEXICAN INSTITUTE

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INDUSTRIAL of a local or wide area communications network with components otherwise illustrated in the Figures. In a distributed computing environment, programming modules can be located in local and remote memory storage devices. Thus, the control system 56 may comprise a computer system that communicates with the system components described herein via local or remote wired or wireless networks.

A controller that could perform the functions described herein could include a processing unit, system memory, and a system bus. The system bus couples system components including, but not limited to, system memory to the processing unit. The processing unit may be any of a number of available programmable devices, including microprocessors, and it will be appreciated that dual microprocessors, multi-core architectures, and other multiprocessors may be employed as the processing unit.

Software applications may act as an intermediary between users and/or other computers and the basic computer resources of electronic control system 56, as described, in suitable operating environments. Such software applications include one or

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY both of the system and application software. The application software may include an operating system that acts to control and allocate resources of the control system 56. The application software takes advantage of resource management by the system software through program models and data stored in memory. of system.

Control system 56 may also, but need not, include one or more interface components that are communicatively coupled via the bus and facilitate interaction with the control system. By way of example, the interface component may be a port (eg, serial, parallel, PCMCIA, USC, or FireWare) or an interface card, or the like. The interface component can receive input and provide output (wired or wireless). For example, input may be received from devices including, but not limited to, a pointing device such as a mouse, trackball, stylus, trackpad, keypad, touchscreen, keyboard, microphone, joystick, video game controller, satellite dish, scanner, camera, or other component. The output may also be provided by the control system 56 to output devices via the interface component. output devices can

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MEXICAN INSTITUTE

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INDUSTRIAL include displays (eg, cathode ray tubes, liquid crystal displays, all light emitting, or plasma) whether touch screen or otherwise, speakers, printers, and other components. In particular, by such means, control system 56 receives inputs from, and directs outputs to, the various components with which control system 56 communicates, as described herein.

In general, the control system receives signals from the building thermostats 18 (directly or indirectly, for example, via the water system control circuit 35), the components of the air conditioning system 12, and optionally, the sensors. temperature or other operating parameter sensors that are not part of the thermostats or system 12. The control system turns the air conditioning system on or off to provide or stop supplying conditioned air to a conditioned space 16 in response to thermostat signals.

This decides whether to transition system 12 to a water heating mode of operation in response to conditions, as described herein, and decides when to return to an air cooled/chilled single condensing mode. over the air or when disabling system 12 as a whole. The device to carry out

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL those functions, and the manner of their operation, are described below.

Still referring to Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6, the air conditioning system includes a refrigerant circuit 58 having refrigerant line portions 60 and 62 that are operatively coupled. to condenser coil 46, compressor 48, evaporator coil 54 and heat exchanger (water cooled condenser) 50. The refrigerant circuit 58 also includes a low ambient control sensor 64, a refrigerant liquid line pressure sensor 66, a heat exchanger refrigerant drain line solenoid valve 68, a line solenoid valve air-cooled condenser refrigerant drain valve 7 0, a pump 52, a water pressure sensor 72, a three-way valve 74, a high pressure switch 76, a compressor 48, an inlet water temperature sensor 152 (Figure 3), an outlet water temperature sensor 150 (Figure 3), a low pressure sensor 78, and a low refrigerant pressure switch 80 (the low pressure switch 80 is redundant to sensor 78 and may be omitted in other embodiments; their operation is reflected by the discussion of sensor 78 herein), all are operatively linked to control system 56 except, in the case of binary switches, when a switch is directly connected to its controlled device. Fans 21 and 29 are also linked to and controlled by control system 56. Control system 56 controls three-way valve 74 to selectively direct refrigerant from the compressor to either the air-cooled condenser or the water-cooled condenser.

Sensor 64 is a pressure sensor that controls system 56 monitors for low ambient temperature conditions. If the system 12 is left in an operating condition in the presence of a low ambient temperature, there is a risk that water vapor in the ambient air will freeze on the evaporator coils. Such a condition can be identified by a low pressure at the evaporator inlet, the control system 586 deactivates the system 12, and the control system detects a pressure from sensor 64 below a predetermined threshold. The operation of air conditioning systems to prevent coil freeze-up should be well understood and is therefore not discussed further herein.

As illustrated in Figure 2, the water to be heated

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MEXICAN INSTITUTE

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INDUSTRIAL flows into heat exchanger 50 via water line 14, as it is driven by pump 52, and out of heat exchanger 50 into tank 30 via outlet line 28.

An expansion valve 82 is disposed in a portion of refrigerant line 62 at an inlet to evaporator coil 54. As explained above, an expansion valve receives an inlet of fluid refrigerant at a high pressure and, depending on configurations inside the valve, produce the fluid at a lower pressure. This allows the pressurized refrigerant in evaporator 54 to lower its pressure in the coil and change phase from liquid to gas.

In the embodiment illustrated in Figure 2, Figure 3, Figure 4, and Figure 5, system 12 includes a single refrigerant circuit, or phase, 58. However, in some embodiments, system 12 includes two or more refrigerant phases. . For example, commercial air conditioning systems can be used to provide air conditioning to relatively large indoor areas 16 and/or indoor areas in which heat-generating equipment is operated that can add significant amounts of heat to the conditioned space in a short period of time. time, thus causing large differences between the actual temperature

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL indoor area and air conditioning system setpoint temperature (ie, if desired). In other words, the load that the air conditioning system can be asked to handle (i.e., the amount of heat that the air conditioning system can be asked to remove from the conditioned space, as defined by the difference between actual and set temperatures). set point for a given volume of air) can vary over a wide range during normal system use. Regardless of load level, it is desired that the air conditioning system rapidly drive the conditioned space toward set point, thereby maintaining the conditioned space at a generally consistent temperature. Therefore, the system selectively couples and decouples additional refrigerant phases correspondingly with load, adding phases as load increases and removing phases as load decreases. The building thermostat system 18 determines the need for air conditioning in the conditioned space, thus providing the control system 56 with a load measurement, and the control system 56 controls the air conditioning system to operate a number of appropriate phases for a given load at a given time. The construction and operation of the thermostat/control system for the control of multi-stage air conditioning systems is to be understood in the art and, therefore, is not discussed in further detail herein.

As will also be understood, a given refrigerant flow path 58 has a limited ability to remove heat from the recirculating air, as defined by the type of refrigerant, the volume of refrigerant in the refrigerant loop, and the rate at which the refrigerant can circulate through the circuit while effectively receiving heat from the recirculating air. As seen from the foregoing, the particular capacity design of the refrigerant circuit is not itself a part of the present invention, but as seen, a refrigerant circuit will have a heat removal capacity. A given circuit can be designed so that it can effectively remove heat from a given interior area of ​​the building through its normal load variation at a desired or acceptable rate, and systems having only a single circuit or phase are within scope. of the present description. However, as will also be understood, the cost of operating a refrigerant circuit varies directly with the capacity of the refrigerant circuit, for example, due to

<img file="MX388293B_D0026.tif" />

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MEXICAN INSTITUTE

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INDUSTRIAL to the size of the compressor needed to operate the circuit and the work done by the compressor in operating the circuit. Consequently, it is known to build air conditioning systems with multiple different refrigerant circuits of standard capacity, such that a given air conditioning system can be built with a particular number of stages to accommodate the particular heat load variation of the system. building that the air conditioning system is expected to supply. As a building heat load rises and falls, individual refrigerant phases can turn on and off. The air conditioning system can selectively turn individual refrigerant phases on and off to adjust the level of compressor operation (and therefore cost) to meet, but not greatly exceed, the capacity needed to handle the load of heat required. Such an arrangement not only enables construction efficiencies, in that air conditioning systems can be configured using standard equipment rather than requiring specially designed components on a case-by-case basis, but also increases operation efficiency. through single phase systems where building heat loads vary significantly.

Figure 6 schematically illustrates a system of

<img file="MX388293B_D0027.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY multi-stage air conditioning 12. Although Figure 6 illustrates a two-stage system, it will be understood that this is for example purposes only and that the system 12 may influence more than two phases. In this example, a first refrigerant circuit 58a defines a first stage, encompassing air-cooled condenser 4 6, compressor 4/8, and evaporator 54. A second refrigerant circuit 58b also passes through the air-cooled compressor 46 and evaporator 54, but includes a compressor 154 that is different from the compressor 48 of the first stage. Refrigerant circuits 58a and 58b share condenser 46 and evaporator 54 for purposes of mechanical convenience, but the refrigerant circuits remain separate from one another, with no refrigerant mixing between them. That is, in condenser 46 and evaporator 54, the two refrigerant paths form two distinct sets of coils within the total coil structure. A single fan 29 moves air 27 through refrigerant circuits 58a and 58b in air-cooled condenser 46, and a single fan 21 moves air 23 through refrigerant circuits 58a and 58b in evaporator 54. Although Figure 6 illustrates a single fan 29 and a single fan 21, it will be understood that multiple fans may be used, for example to allow the use of smaller, less expensive fans to create a single airflow that may otherwise be required. an inordinately more expensive single fan, but because the fans create a single airflow, Representations of a single fan are illustrated in Figure 6 and discussed herein for ease of explanation. Being located close to each other in the same condenser/evaporator structures, i.e. parallel to each other from the perspective of airflows, each of the airflows 27 and 23 simultaneously pass through both circuits in the respective condenser/evaporator, allowing more effective heat transfer than arrangements in which the coil assemblies are arranged sequentially. However, it should be understood that conventional sequential air-cooled condensers, and/or respective sequential evaporators, for multiple phases of refrigerant are encompassed within the present description.

Accordingly, refrigerant circuit 58b includes a refrigerant line 156 that transports refrigerant from air-cooled condenser 46 through an expansion valve 158 to evaporator 54, under the force of compressor 154. Compressor 154 draws refrigerant from heated gas from evaporator 54 to compressor

<img file="MX388293B_D0028.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY through a refrigerant line 157, and then returns to the air-cooled condenser 46, in a circulation pattern as described above. Water-cooled condenser 50 is used in the refrigerant phase defined by refrigerant path 58a. Although the refrigerant path 58b does not include a water heating component circuit, it should be understood that the system must be configured to operate multiple water heating circuits in respective refrigerant phases. Thus, it is to be understood that the currently described embodiments are provided by way of example only and without limitation of the present description. In that regard, the operation of the air conditioning system 12 will now be described with reference to the stages illustrated in Figure 7, Figure 8, Figure 9A and Figure 9B, and with respect to a single-stage example (Figure 2, Figure 3, Figure 4 and Figure 5) and an example of multiple phase (Figure 6).

In one embodiment and with reference to Figure 1, Figure 2 and Figure 6, the tank 30 includes a temperature sensor mounted in or through the tank housing to measure the temperature of water within the tank. In another embodiment, the temperature of the water is measured within the flow path of the water entering or leaving the water-cooled condenser 50 within the housing 24 of the system 12, rather than

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL inside the tank 30 by itself, and therefore the temperature sensor is arranged along the water inlet line 14 or the water outlet line 28. In any assumption, the temperature sensor produces a signal corresponding temperature sensor to control circuit 56. The control circuitry compares a temperature represented by the temperature sensor signal to a predetermined threshold related to the high set point temperature of the water heating system. If the measured temperature is below the threshold, and if the system 12 is currently operating in an air-cooling mode (i.e., the control system, in response to thermostat signals from the interior space of the building 16, operated compressor 48 to circulate refrigerant through the refrigerant path, and operated fans 21 and 29, to provide air conditioning to space 16), control circuit 56 drives a relay (not shown) that switches three-way valve 74 to direct refrigerant flow from the compressor to water-cooled condenser 50. The control system also drives a relay (not shown) that drives pump 52 to draw water from tank 30 (and/or depending on the existence of a request for cold water within the cold water source 31 of the water system of the

<img file="MX388293B_D0030.tif" />

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MEXICAN INSTITUTE

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INDUSTRIAL building) through fitting 32 and pipe 14 and transports the water to the water-cooled condenser 50, where the refrigerant circuit transfers heat to the water, which returns to tank 30 through pipe 28 and fitting 33. System 12 operates in water heating mode until the call for cooling air in space 16 ends, or a temperature sensor in the water line 28 or tank 30 indicates that the heated water provided by system 12 has reached a temperature close to the target temperature for tank 30, or a pressure sensor in the refrigerant line indicates a high pressure condition. Regardless of the reason, once the water heating ends, the system 12 will switch back to a water heating mode if there is a request for air cooling and if the water temperature in the tank 30 falls below the threshold. default temperature. Therefore, repetition of this cycle tends to increase the temperature of the water in the tank 30 towards the target temperature of the tank.

With reference more specifically to the operation of the system 12 in conjunction with the water heating system 38 and the building 18, and with reference to Figure 1, Figure 2, Figure 6 and Figure 7, assume in 7 01 that the air conditioning system 12 is in an idle state or that a transition from a water heating mode has taken place but that the control system 56 receives a signal from the building thermostat (not shown) or an intermediate building control system 18 that requires the air conditioning system to provide cold air to the conditioned space 16. In response, at 702, control system 56 initially operates system 12 in an air-cooled condensing and air-cooling mode, regardless of whether conditions might also exist to warrant a water-heating mode, for a period of time (in this example, two minutes) sufficient to remove any refrigerant that may remain in the heat exchanger 50 from its previous operation. Control system 56 initiates this process by activating compressor 48. When system 12 operates multiple lines/stages of refrigerant 58b, and depending on the cooling request requirements, control system 56 may also instruct system 12 to to activate one or more additional stage compressors 154. By activating compressors 48 and 154, control system 56 activates each corresponding compressor refrigerant circuit, or stage. The control system sets the three-way valve 74 of the primary stage 58/58a through an electromechanical relay (not shown) to direct refrigerant from the compressor 48 to the air-cooled condenser 46 through the portion of line of refrigerant 60. The phases of refrigerant 58b have a direct path between the compressor 154 and the air-cooled condenser. Therefore, with the air conditioning system 12 in an air-cooled/air-cooled condensing-only mode, without the need for the control system to also select and drive the water-cooled condenser 50 in the primary stage 58/58a , gaseous refrigerant flows from evaporator coil 54 to compressor 48/154 via refrigerant line sections 60. Compressor 48/154 pumps the gaseous refrigerant forward, increasing refrigerant pressure and temperature and causing the now hotter refrigerant gas to flow to condenser 46 directly from compressor 154 and via three-way valve 74 from the compressor. 48. Control system 56 drives fan 29 (shown only in Figure 6 but present in the embodiment of Figure 2, Figure 3, Figure 4 and Figure 5) at a constant speed or speed selected from a plurality of possible speeds. , to thus push or pull air through the condenser coils, causing the gaseous refrigerant to cool on the coils 46 and change

<img file="MX388293B_D0031.tif" />

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MEXICAN INSTITUTE

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INDUSTRIAL thus the phase from gas to liquid. This draws heat energy from the coolant into the moving air, thus dissipating heat from the coolant to the surrounding environment. Since the refrigerant carries heat contributed to the refrigerant in the evaporator by the air drawn from the interior space 16 through the conduit 22, this transfers the heat from the conditioned space to the ambient environment.

Still under pressure provided by compressor 48/154, the now liquid refrigerant flows from condenser outlet 46 back to evaporator 54 and expansion valve 158, if in refrigerant path 58b and, if in refrigerant path 58a, to a partition 88 connecting refrigerant line portion 62 with refrigerant line portion 92 from a refrigerant outlet of heat exchanger 50. A check valve 94 in line 92 at partition 88 prevents the flow of refrigerant from coil 46 from flowing to heat exchanger 50, and thus refrigerant continues through the refrigerant line portion 62 to the coil. evaporator 54 and expansion valve 82. A filter 63 filters and removes moisture from the refrigerant upstream from the expansion valves.

82/158 expansion valves lower pressure

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY of the liquid refrigerant as it enters the respective coil portions of the evaporator 54. Inside the evaporator, the refrigerant undergoes the transition to the gas phase, extracting heat energy from the air driven by the fan 21 (shown only in Figure 6 but present in the embodiment shown in Figure 2, Figure 3, Figure 4 and Figure 5) flowing through coils 54. The evaporator fan draws air from the interior space 16 (Figure 1) through the return duct 22 and moves the air, which passed through the evaporator, back to the space 16 through the supply duct 26.

In this way, the recirculated air from the interior space of the building 16 contributes the heat needed by the refrigerant in the evaporator 54, cooling the interior air that is recirculated by the evaporator fan and thus cooling the conditioned interior space 16. Thereafter, the Now hotter gaseous refrigerant discharged from evaporator coils 54 returns to compressor 48/154 via line sections 60, and the cycle repeats.

When the control system 56 initializes the air conditioning system 12, or transitions the air conditioning system 12 from a water-cooled condensing mode (Figure 3 and Figure 4) to an air-cooled condensing mode ( Figure 2), in 702, so that

<img file="MX388293B_D0033.tif" />

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL If the system enters the operational mode discussed with respect to Figure 2, some refrigerant may remain in heat exchanger 50 and line 92 which, if not recovered, could be omitted from the refrigerant flow circuit discussed above. previous. The 58/58a refrigerant circuit is designed to accommodate a given maximum heat load by utilizing all of the refrigerant in the circuit. To the extent that the system operates in an air-cooled/air-cooled condenser mode with unused refrigerant remaining in the heat exchanger, the heat load capacity of the refrigerant circuit 58/58a decreases, thus increasing the temperature of the refrigerant remaining in the system as it tries to handle the load and in turn increases the compressor load. Therefore, at 702, upon activation of the compressors and fans from an idle state, or upon transition of the system from the water heating mode to the Figure 2 mode, the control system 56 also actuates a solenoid valve 68 which opens a refrigerant drain line 110/102 between the refrigerant outlet line 92 of the water-cooled condenser 50 and a point in the refrigerant path in the evaporator, which can be considered to include portions of the refrigerant path

<img file="MX388293B_D0034.tif" />

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL downstream from expansion valve 82 that has a low pressure comparable to and caused by low pressure in the evaporator coils, even if it is upstream of the same evaporator coil. Since the three-way valve 74, in the mode shown in Figure 2, directs the compressor output to the air-cooled condenser 46 but not to the heat exchanger 50, the refrigerant line in the heat exchanger 50 and the Line 92 is depressurized, except for the effect of ambient heat and any residual heat from previous operation of the heat exchanger. However, the pressure in the refrigerant line to the evaporator is at a lower pressure, and the opening of valve 68 therefore creates a differential pressure that draws refrigerant from the heat exchanger and line 92 to the evaporator, and thus returns in the refrigerant flow circuit. Although this drained refrigerant bypasses the expansion valve, thus bypassing the pressure-reducing function that the expansion valve performs, the pressure of the drained refrigerant is already at a relatively low pressure. Control system 56 holds valve 68 open only long enough to draw trapped refrigerant out of heat exchanger 50 and line 92. The length of this time can vary.

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MEXICAN INSTITUTE

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INDUSTRIAL be determined through testing, calibration, and storage in control system programming 56, and in the modes currently described this duration is two minutes. Accordingly, control system 56 maintains valve 68 in the open state for this predetermined period of time immediately following entry into the air conditioning (air-cooled condensing) mode of Figure 2.

Referring to Figure 1, Figure 3, Figure 6, and Figure 7, at 704, control system 56 deactivates valve 68 upon expiration of the two-minute time window, and activates water pump 52 for a moment, for example, one minute in the present examples, sufficient to draw the water from the tank (and/or source 31) through fitting 32 and into pipe 14, upstream and downstream from pump 52, so that a temperature sensor 152 fixed on or in the water inlet pipe 14 can obtain an accurate detection of the water temperature at the inlet to the heat exchanger. The time period depends on the time needed to acquire an accurate temperature of the water in view of the variations in the temperature of the water from the tank. Temperature sensor 152 outputs a corresponding signal to control system 56, thereby providing a signal to the control system that

<img file="MX388293B_D0036.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY corresponds to the temperature of the water in the tank 30 and/or the source 31. Alternatively, a temperature sensor may be provided in the tank 30 that outputs a temperature signal to the control system 56. In addition , the pressure sensor 72 is arranged in the water inlet pipe 14 and emits a signal to the control system indicating the pressure of the water pumped in the pipe 14, in kilogram-force per square centimeter (kgf/cm²) (pound-force per square inch gauge (psig).

The control system checks the water pressure indicated by sensor 72 against a predetermined threshold water pressure value that corresponds to a minimum pressure necessary to ensure that water flow is present for flat plate heat exchanger 50. . As will be apparent from the present description, the threshold minimum pressure can be determined through calibration, and in the currently described examples it is at a predetermined value of kgf/cm² (psig).

The control system also checks the temperature indicated by the temperature sensor signal to determine if it is below a threshold temperature that corresponds to a level sufficient to prevent pressure spikes in the refrigerant path, or

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY

35°C (95°F) in the currently described examples. As should be understood, the water heating system 38 of the building 18 operates at a high set point temperature where the water heating system is intended to supply water to the building's hot water fixtures. Traditional and commercial water heating systems that provide hot water to dishwashers, for example, maintain a high set point temperature of 85°C (185°F) or thereabouts, while newer systems, in which dishwashers use chemical washing techniques, provide water at or above 60°C (140°F). In an environment of 85°C (185°F) or 60°C (140°F), a desirable temperature for maintaining the water in tank 30 may be within a range at or about 48.8°C (120°F). ) to at or about 51.6°C (125°F), but it will be understood that the target water tank temperature depends on the requirements for the particular water system. To maintain the temperature of water in tank 30 at or near the target range, system 12 may be configured to provide water to tank 30 through line 28 at a temperature greater than the target range of 48.8°C - 51.6°C (120 °F 125°F), in this example at a high threshold at or around 58.8°C (138°F). In a system where 60°C (140°F) may be the highest temperature at which it is intended that the

<img file="MX388293B_D0038.tif" />

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL system supplies water, the target of 58.8°C (138°F) in the currently described examples provides heat to the tank 30 without risk of the water in the tank becoming too hot. The target of 58.8°C (138°F) is therefore the actuator temperature at which control system 56 turns off heating of water in system 12.

As seen, the low threshold water temperature at which the control system 56 triggers the heating of water in the system 12 (i.e., the temperature below which the water in the tank 30 will drop in the examples currently described above that the control system 56 triggers the water heating in the system 12 from a state without water heating) is less than the high/off threshold water temperature (58.8°C (138°F, in this example)) and the desired water temperature range for tank 30 (48.8° - 51.6°C (120^pF - 125°F, in this example)), and in the embodiments described herein it is 35°C (95°F). In such embodiments, the low water temperature threshold is selected to prevent excessive switching of system 12 between heating water and air-cooled condensing modes but also to prevent pressure spikes within the refrigerant circuit of system 12. As described herein, the transition from air-cooled condensation to

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL water-cooled condensing (i.e. heating water) changes the medium that removes heat from the refrigerant from the ambient air to the water in the tank 30. To the extent that the low water temperature threshold is greater than the ambient air temperature, there may be an instantaneous increase in the average heat removal temperature when the system 12 transitions to the water heating mode. , leading to an instantaneous decrease in the system's ability to remove heat from the coolant and therefore an increase in coolant temperature. Because heat corresponds to pressure in the refrigerant line, this relatively quick transition can create a pressure spike in the refrigerant circuit. In this mode, therefore, the low water temperature threshold is selected near an expected high ambient air temperature at building location 18, or otherwise through system calibration to determine a threshold temperature. low that prevents pressure changes within a range, as desired. However, it should be understood that other arrangements are possible, and for example, that the system may control the low pressure threshold to vary with the ambient temperature measured in the system 12/housing 24.

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY

If, at 706, the inlet water pressure is less than 0.35 kgf/cm² (five psig), or if the entering water temperature is greater than 35°C (95°F), then the control system maintains the system in an air-cooled mode, which uses the air-cooled condenser 46 but not the water-cooled condenser 50, for a period of time programmed into the control system 56, for example, ten minutes, as indicated at 708. Control system 56 may provide an option through its user interface to allow the user of the system to select the hold time, thus allowing the hold period at 708 to vary as desired. Therefore, the air conditioning system 12 continues its air-cooled condensing operation, as started at 702, for ten minutes, and then checks the temperature and pressure again at 706.

It should be understood that the control system 56 may perform other functions as the system is operated. For example, when the yes decision occurs at 706 due to a water inlet pressure threshold breach, the control system may initiate an error notification to a central computer system in building 18 or via the control system user. In addition, the control system 56 repeatedly monitors

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY the production of a pressure switch 7 6, which is configured to change state when/if the pressure in line 58 exceeds a predetermined threshold (for example, 42.8 kgf/cm² (610 psig) or otherwise as established by the manufacturer's regulatory registration, and/or testing and/or component classification. If, at any time, the signal produced from the switch 76 indicates that the pressure in the refrigerant line has exceeded the threshold, the control system 56 immediately deactivates the compressor 48 and initiates an alarm/error notification via a computer system. central building and/or the user interface of the control system. Alternatively, or in addition, the output of switch 76 may directly power the compressor and/or its power source, directly deactivating the compressor when the pressure switch threshold is exceeded. A similar binary pressure switch is provided at the refrigerant outlet of each compressor 154 of each, if any, additional refrigerant stage, and if the respective switch detects a high pressure condition on any stage, the control system and/or the switch deactivates the corresponding compressor. Still further, the control system 56 continuously monitors the instruction signals from the building's thermostat. If the signal (i.e. call for cooling) indicates conditions

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY changed, indicating that the entire air conditioning system must terminate operation, or that one or more phases of a multi-phase system is no longer needed, or that the heat load has decreased so that one or more more stages are no longer needed, the control system deactivates the corresponding compressors. Thus, although not indicated in the operational loop illustrated in steps 706/708, it is to be understood that the control system may monitor and control various aspects of system operation as the air conditioning system 12 continues to operate. air-cooled/air-cooled condensing mode and air-cooled/water-cooled condensing mode.

During the hold time, and as long as the deactivation does not occur as a result of a high pressure condition or a change in cooling request, the control system 56 operates the air conditioning system 12 in the air-cooled condensing mode. air/air-cooled, as illustrated in Figure 5. Gaseous refrigerant flows from evaporator coils 54 to compressor 58/154 via refrigerant line sections 60. The 48/154 compressor pumps the gaseous refrigerant forward, increasing the refrigerant pressure and temperature, and causing

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY that the now hotter refrigerant gas flows into condenser 46 directly from compressor 154 and via three-way valve 74. Fan 29 moves air through the condenser, extracting the air and condensing the refrigerant . Still under pressure from compressor 48/154, the now liquid refrigerant flows from condenser outlet 46 back to evaporator 54 via expansion valve 158, if in refrigerant path 58b and, if in refrigerant path refrigerant 58a, to partition 88 and refrigerant line 62 to the evaporator via expansion valve 82. Expansion valves 82/158 lower the pressure of the liquid refrigerant as it enters the respective coil portions of evaporator 54. Fan 21 moves air through the evaporator, and the refrigerant undergoes the gas phase transition, extracting heat energy from the fluid air. In this way, recirculating air from the interior building space 16 contributes the heat needed by the refrigerant in coil 54, thereby cooling the interior air flowing back into the conditioned interior space 16. The now hotter gaseous refrigerant discharged from evaporator coils 54 it then returns to compressor 48/154 via line sections 60, and the cycle repeats.

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MEXICAN INSTITUTE

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INDUSTRIAL

Still referring to Figure 1, Figure 2, Figure 3, Figure 6 and Figure 7, if at 706 the inlet water pressure is greater than 0.35 kgf/cm² (five psig) and the inlet water temperature is less than 35°C (95°F), then the water heating system 38 in building 18 is considered to need heat from the refrigerant to heat the water in tank 30 . In this mode, switching from the air-cooled/air-cooled condensing mode to the air-cooled/water-cooled condensing mode involves moving the three-way valve 74 so that the three-way valve directs the refrigerant from compressor 48 to water-cooled condenser/heat exchanger 50 and not to air-cooled condenser 46. This change in the refrigerant path circuit 58/58a depressurizes that portion of the refrigerant path from compressor 48 to (and through) condenser 46 and into partition 88. The refrigerant path from heat exchanger 50, through production line portion 92 and the portion of refrigerant line portion 62 downstream from partition 88, is pressurized, thus preventing remaining refrigerant in the The now depressurized part of the path drains downstream to the evaporator 54. Therefore, a refrigerant drain line 112/102 connects

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MEXICAN INSTITUTE

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INDUSTRIAL smoothly the portion of the main refrigerant line 62, downstream of the split 88, with a point in the refrigerant line at the evaporator 54, which can be considered to include the portion of the refrigerant line proximate to the portion evaporator coil but downstream from the expansion valve 82, as discussed above. Typically, the pressure in the evaporator is less than the pressure in the depressurized portion of line portion 62, which maintains some pressurization due to residual heat, so that when control system 56 actuates a relay to open the solenoid valve 70 (which is normally closed), to open the drain line 112/102, drain line 112/102 drains the evaporator where refrigerant remains in the refrigerant path extending from compressor 48 to partition 88 via condenser 46. In the embodiments illustrated in Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6, the drain line is coextensive in part with the drain line between the heat exchanger refrigerant output and the evaporator, and thereon , a check valve 108 prevents refrigerant from flowing between the depressurized condenser 46 and the evaporator from flowing into the heat exchanger production line.

However, if the ambient air in system 12 is cold enough, residual heat in the now depressurized portion of the refrigerant line through condenser 46 (particularly since condenser 46 is air-cooled and therefore therefore sensitive to ambient air temperature) may be insufficient to generate a sufficient pressure differential to drain refrigerant from compressor 46 to the evaporator. Similar to the situation described above, with respect to the need to drain the refrigerant from the heat exchanger after entering the condition illustrated in Figure 2, the residual refrigerant in the compressor 46 is required to circulate in the portion active refrigerant path during air-cooled/water-cooled condensing mode (i.e., air cooling/water heating mode) to support the heat load the system is expected to support. Accordingly, at 710 and before transitioning the system to the air-cooled/water-cooled condensing mode, the control system 56 checks the signal produced from a thermistor (not shown) mounted on or otherwise next to system 12 to measure the ambient air temperature to system 12. By testing system 12 in the given configuration, you can

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY determine (a) that there is a minimum pressure differential between the depressurized portion of the refrigerant path through the condenser 46 and the refrigerant path in the evaporator that is needed to drain the refrigerant from the refrigerant path depressurized to the evaporator and (b) that, regardless of the refrigerant line pressure in the evaporator, the actual differential pressure will always be at least as large as this desired differential pressure above a given ambient air temperature. Although it should be understood that this threshold temperature may vary with configuration variations of the system 12, in the currently described embodiments the initial threshold ambient air temperature is 26.6°C (80°F). Thus, if at 710, control system 56 determines that the signal emitted from the ambient thermistor indicates a temperature at or above 26.6°C (80°F), control system 56 proceeds to convert system 12 so from air-cooled/air-cooled condensing to air-cooled/water-cooled condensing mode on 712.

However, even if the ambient air temperature indicated by the ambient temperature sensor signal is below 26.6°C (80°F), the desired differential pressure may still exist, mainly due to possible variations in pressure. of refrigerant line in the evaporator 54. Therefore, if the ambient air temperature sensor indicates an ambient temperature below 26.6°C (80°F), the control system 56 in 710 checks the status of the following relationship:

0.0202(Room**2) + 0.5188(Room) - 20.071 > Evaporator Pressure, where 0.0202(Room**2) + 0.5188(Room) describes the normal pressure curve for the refrigerant in the 58/58a refrigerant line, Ambient is the temperature indicated by the signal from the ambient temperature sensor to system 12, 20.071 is the desired differential pressure between portions of the refrigerant path in the unpressurized condenser 46 and the evaporator, and Evaporator Pressure is the pressure indicated by the output of a pressure sensor 78 in the refrigerant line downstream from but proximate evaporator 54 (i.e., a point in the refrigerant line that can be considered part of the evaporator portion of the refrigerant line, or in the evaporator, in terms of refrigerant pressure). As should be understood, the pressure of a refrigerant in an enclosed line depends on the given refrigerant and the ambient temperature at the line and can be described by a specific formula for those variables. Typically, the refrigerant manufacturer publishes the formula for a refrigerant they sell, and in the case of the refrigerant used in the examples currently described (R410A), the pressure curve formula is 0.0202(Ambient**2) +

0.5188(Ambient). For a given construction of system 12, and given the formula and variations in temperature as measured by the ambient temperature sensor, system 12 can be tested for displacement, in this example 20,071.

The control system 56 performs the ratio check when the system 12 is in the air-cooled/air-cooled condensing mode, before transitioning the system 12 to the air-cooled/air-cooled condensing mode. by water. If, at 710, the ambient temperature is less than 80°F (26.6°C), and the above relationship status is true, then the control system 56 proceeds to convert the system 12 from the air-cooled condensing mode /air-cooled to air-cooled/water-cooled condensing mode, in 712. If, however, the ratio state is false, the control system 56, at 714, deactivates the fan 29, and in the event that multiple refrigerant phases are present, deactivates the compressors 154, but maintains the compressor 48.

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY and the fan 21 active, so that the recirculating air and the compressor supply heat to the circulating refrigerant, which is directed to the condenser 46 without heat removal by an air flow in the condenser, increasing thus the heat and pressure of the refrigerant.

By testing a given configuration of system 12, the user can determine a previously measured pressure at pressure sensor 66 to transition to air-cooled/water-cooled condensing mode (i.e., in the air-cooled condensing mode), which will always provide the desired differential pressure after transition to air-cooled/water-cooled condensing mode that is sufficient to drain refrigerant from the unpressurized portion of the refrigerant path. In the currently described embodiments, for example, the control system 5 6 operates the system 12 in an air-cooled condensing mode (with the fan 29 off) until detecting, at 716, a pressure of 38.3 kgf/cm² (545 psig), as indicated by the signal produced from pressure sensor 66.

When the check at 716 indicates that the pressure reached 38.3 kgf/cm² (545 psig), or if the test passed at 710, then at 712, the control system 56 deactivates the

<img file="MX388293B_D0048.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY condenser fan 29 and changes the configuration of the three-way valve 7 4 so that the refrigerant flows from the compressor 48 through the outlet fitting 86 to an inlet of the flat plate heat exchanger 50 through from a refrigerant connector line 96 and does not flow to the air-cooled condenser 46. Although other types of heat exchangers may be used, a flat plate exchanger is used in the embodiments described herein due to the compact size of the heat exchanger and its resistance to unintentional mixing of water and refrigerant. As seen from the above, refrigerant production line 92 connects the refrigerant outlet of heat exchanger 50 with refrigerant flow line 62 via check valve 94 and partition 88. A check valve 98 blocks the refrigerant flow from partition 88 back to condenser coil 46. Thus, liquid refrigerant leaving heat exchanger 50 flows through the portion of refrigerant line 62 downstream of partition 88 to expansion valve 82 and thus to evaporator coil 54. . As discussed above with respect to Figure 5, the control unit 56 drives the evaporator fan to thereby move recirculating air through the evaporator coils to energize the refrigerant within the evaporator 54 and to cool correspondingly the recirculating air. The now hotter gaseous refrigerant discharged from evaporator 54 then returns to compressor 48 via refrigerant line portion 60, and the cycle repeats. When only one phase of refrigerant 58 is present in system 12, condenser fan 29 may be disabled during this mode of operation. However, if one or more stages of additional refrigerant are present, and if the then pending call for cooling requires its operation, the control system keeps its compressors active during this mode and therefore keeps the condenser fan 29 running. active.

Simultaneously, control system 56 drives pump 52 to draw water from inlet line 14 from tank 30 via fitting 32. Pump 52 moves the water to heat exchanger 50, where refrigerant gas supplied to the heat exchanger from the compressor 48 transfers heat to the water. Heat exchanger 50 produces the now hotter water at outlet fitting 100 into outlet water pipe 28 and thus back to tank 30 (FIG. 1). The flow capacity and the capacity of

<img file="MX388293B_D0049.tif" />

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL heat exchanger 50 heat exchanger are such that heat exchanger 50 removes enough energy from the condenser outlet refrigerant to gaseous refrigerant into a liquid. Thus, as should be apparent from the present disclosure, the capacity and operational specifications of heat exchanger 50 may be selected so that the heat exchanger, when operated to heat water, functionally replaces the condenser coil. 46. Thus, the water-cooled condenser 50 replaces the air-cooled condenser 46 by performing the function of the condenser, but instead of rejecting the heat removed from the refrigerant into the ambient environment, the heat exchanger (water-cooled condenser) 50 transfers the rejected heat to the water in the building's water heating system.

As discussed above, at the time the control system transitions the air conditioning system 12 from air-cooled/air-cooled condensing mode to air-cooled/cooled condensing mode by water, the condensed refrigerant remains in the condenser 46 which is necessary for the full air conditioning function. Therefore, simultaneously with the switching of the

<img file="MX388293B_D0050.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY three-way valve 74 to direct the refrigerant from the compressor 48 to the water-cooled condenser 50 instead of the air-cooled condenser 46, the control system 56 actuates the solenoid valve 70, which opens thus refrigerant drain line 112/102 between the portion of refrigerant line 62 upstream from partition 88 and evaporator 54.

Control system 56 holds valve 70 open long enough to remove residual refrigerant from condenser coil 46 and the upstream portion of line 62. In the embodiments described above, this time period is approximately two minutes, but it will be understood that the amount of time will depend on the particular configuration of the air conditioning system 12 and that the time period can be determined through testing. and system calibration and can be programmed into the control system 56. At the end of this predetermined time period, control system 56 sends a signal to a relay that controls solenoid valve 70 to cause the valve to close. After this point, refrigerant flows from compressor 48 to heat exchanger 50 to evaporator 54, and back to compressor 48, as described above and illustrated in Figure 4.

<img file="MX388293B_D0051.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY

With respect to the operation of the system 12 in the water heating mode, as shown in Figure 4, the transition from air to water as the heat removal medium can decrease the ability of the system to remove heat from the refrigerant flowing through the refrigerant path, wherein as the water cycled through the water-cooled condenser 50 and tank 30 increases in temperature, the ability of the water to remove heat from the coolant may decrease. This can increase the pressure at the outlet of the compressor 48. Therefore, when the pressure sensor 66 provides a signal to the control system 56 indicating a pressure level of 39.7 kgf/cm² (565 psig), or that a high pressure condition has been reached (for example, 38.3 kgf/cm² (545 psig) ) within one minute of transitioning to water heating mode, the control system opens a port within the three-way valve 7 4 to a refrigerant bypass path 97 to the return refrigerant line 60 from the line at the three-way valve that receives the outlet of compressor 48. This causes hot refrigerant gas from compressor 48 to bypass heat exchanger 50 and evaporator 54 and flow directly back to compressor 48.

With reference to Figure 8, and as seen in the

<img file="MX388293B_D0052.tif" />

MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY above, the control system 56 regularly checks the signals from the building thermostat for a request for cooling and the output of the temperature sensor 76. If at any time (802) during the air-cooled/air-cooled condensing mode, the control system 56 receives a signal from the building thermostat 18 (Figure 1) indicating which cooling cycle of the refrigerant circuit 58 /58a/58b (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) should end, then at 804, the control system turns off the compressors of the corresponding refrigerant phases. If the call for cooling ends for all refrigerant phases (if it is a multi-phase arrangement), the control system also deactivates condenser fan 29 and evaporator fan 21 at 804. If at 802 the cooling requests are still in effect, at 806, the control system checks to determine if the refrigerant pressure sensor 76 for any refrigerant phase changed state, indicating a refrigerant line pressure for that phase greater than the high level pressure threshold, in this case, 42.8 kgf/cm² (610 psig). If so, the control system turns off the corresponding refrigerant phase, at 804. If the pressure at 806 did not reach the shutdown threshold, the control system returns to

<img file="MX388293B_D0053.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY check the request for cooling in 802.

Referring to Figure 9A and Figure 9B, the system management routine iteration of Figure 8 expands when the system operates in air-cooled/water-cooled condensing mode. For example, if the system 12 operates multiple refrigerant loop phases while one of the phases operates in a water heating mode, and if the cooling call for one of the other phases expires, the system may experience an increased probability of a pressure spike. The probability may arise when one of the refrigerant phases stops circulating through the evaporator, in which the remaining refrigerant paths, including the refrigerant path that is in water heating mode, may have one or more responsibilities for remove heat from the air passing through the evaporator coils. As seen from the above, a refrigerant path that is in water heating mode depends on the water in the tank 30 removing heat from the condenser side of the circuit, but as the temperature of the tank increases, the capacity of the tank 30 increases. water to remove heat can decrease. In short, therefore, this process can cause an increase in coolant temperature, increasing

<img file="MX388293B_D0054.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY the probability of a rapid rise in pressure. Through the system test, a refrigerant pressure can be determined above which this probability arises. In the present examples, this threshold is 36.5 kgf/cm² (520 psig) at pressure sensor 66 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6), but it should be understood that this threshold may vary with system configuration. It should be understood that a binary pressure switch, such as switch 76, could be used for a similar purpose. Additionally, although the pressure sensor 66 is located in the evaporator (and in particular close to the expansion valve) because a pressure change is likely to be evident at that point in the refrigerant path, it should be understood that pressure can be measured for that purpose at other points in the refrigerant path. Accordingly, if at 902, the system 12 is operating in a multiple refrigerant loop mode, the control system checks at 904 for the request for cooling from the building thermostat 18 (FIG. 1). If at 904 a cooling request for any of the non-water heating phases ends, then at 906, the control system 56 checks the signal produced from the pressure sensor 66 in the water heating refrigerant phase. If in 906 this pressure is greater than 36.5 kgf/cm² (520

<img file="MX388293B_D0055.tif" />

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL psig), the control system switches three-way valve 74 (Figure 2, Figure 3, Figure 4, Figure 5, and Figure 6) at 907 to direct refrigerant from compressor 48 (Figure 2, Figure 3, Figure 4 , Figure 5 and Figure 6) to the air-shipped condenser and not to the water-cooled condenser, and returns to step 702 (Figure 7). If system 12 is not in multi-stage refrigerant circuit mode in 902, or there is no secondary refrigerant phase cooling request completion in 904, or pressure at sensor 66 is less than 36.5 kgf/ cm² (520 psig) at 906, control system operation proceeds to 908.

If at 908, control system 56 receives a signal from building thermostat 18 (FIG. 1) indicating that the cooling cycle of water heating refrigerant circuit 58/58a (FIG. 2, FIG. 3, FIG. 4, FIG. 5 and Figure 6) should terminate, then, at 910, the control system deactivates compressor 48 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6). If the call for cooling is over for all refrigerant phases (if a multi-phase arrangement), condenser fan 29 and evaporator fan 21 are also deactivated at 910, unless the system is operated in a mode ( typically controlled from that thermostat) in which the fan continues operation regardless of compressor activation. If at 908 the request for cooling is still in effect, at 912 the control system checks to determine if the refrigerant pressure switch 76 changed state, indicating a refrigerant line pressure greater than the high level pressure threshold, in this case 42.8 kgf/cm² (610 psig) . If so, the control system disables the coolant phase at 910.

If the pressure at 912 did not reach the shutdown threshold, the control system checks the temperature of the water leaving the heat exchanger 50 in the water outlet line 28, as indicated by the signal produced from a temperature sensor. water 150 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) in line 28. As described above, the control system 56 executes the water heating mode to heat the water in the water storage tank 30 to a target temperature to be used in the building water heating system 18, in these modes within a range of about 48.8°C (120°F) to about 51.6°C (125°F). Therefore, the control system checks at 914 whether the temperature of the water leaving the heat exchanger is at a maximum temperature indicating that the water in the tank 30 (which is recirculated back through the heat exchanger) heat as the control system draws

<img file="MX388293B_D0056.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY repeatedly water from tank 30 for heating) probably reached the target range, in this example at or about 58.8°C (138°F). As seen from the foregoing, the system can be tested to determine the particular threshold water temperature for a given configuration of the system 12. If at 914 the control system 56 receives a signal from the temperature sensor 150 indicating that the temperature of the water leaving the heat exchanger exceeded the water heating threshold of 58.8°C (138°F), then the system control switches three-way valve 74 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) at 907 to direct refrigerant from compressor 48 (Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) from the water-cooled condenser to the air-cooled condenser, and returns to step 702 (Figure 7).

If at 914 the leaving water temperature is below the water temperature threshold, the control system checks the output of the refrigerant circuit pressure sensor 66 to determine if the refrigerant line pressure in the evaporator is below the threshold. at a level approaching a point where the pressure sensor 7 6 can change state and thereby trigger a pressure based system shutdown. As discussed in

<img file="MX388293B_D0057.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY above, the refrigerant line pressure may be higher in the water-cooled condensing mode relative to the pressure that may occur in an air-cooled condensing mode under similar circumstances because the water in the tank 30, as it recirculates through the heat exchanger and increases in temperature, it becomes less capable of removing heat from the refrigerant than the ambient air moved through the air-cooled condenser. Therefore, if the control system detects that the refrigerant line is approaching a pressure failure level, the control system transitions the system 12 from air-cooled/water-cooled condensing mode to water-cooled condensing mode. air-cooled/air-cooled condensing, which immediately allows the system 12 to remove more heat from the refrigerant than in the water-cooled condensing mode and possibly moves the system away from pressure failure.

The control system determines the refrigerant line pressure from pressure sensor 66, in the evaporator upstream from the expansion valve. Because pressure sensor 66 travels in the refrigerant line from pressure switch 76, and is further downstream from the compressor, there is an inherent pressure drop from switch 76 to sensor 66, which can be determined through testing a given system configuration 12. Having performed such a test and having determined the inherent pressure drop, and having included an additional pressure offset corresponding to a pressure at a level below the High Pressure Fault level to allow sufficient time for the system, once transition to air-cooled condensing mode takes place, initiate the lowest refrigerant pressure movement before a pressure rise causes pressure switch 76 to detect a fault level pressure (for example one point four kgf/cm² (twenty psig)), the control system 56 checks the output of the pressure sensor 66 at 916 to determine if the preliminary threshold refrigerant pressure level has been met or exceeded. In the embodiments described herein, the preliminary threshold coolant level is 40.0 kgf/cm² (570 psig), although it should be understood that the threshold level may vary with varying system 12 settings. Alternatively, the control system may monitor the refrigerant pressure at the outlet of compressor 48, and in this case the preliminary threshold refrigerant pressure level is the actuator level (48.8 kgf/cm² (610 psig)), less than the displacement of

<img file="MX388293B_D0058.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY additional pressure. If the control system detects that the refrigerant line pressure at 66 exceeds the preliminary fault level, the control system transitions the system 12 from air-cooled/water-cooled condensing mode to condensing mode. air-cooled/air-cooled

907.

One possible cause of refrigerant pressure rising in system 12 to a level sufficient to cause the system to transition from water-cooled condensing to air-cooled condensing at 916, is a drop in temperature at the conditioned space 16 of the building 18 (Figure 1). As the air conditioning temperature in space 16 drops, the recirculating air moving through evaporator 54 is correspondingly less able to contribute heat to refrigerant moving through the evaporator. This, in turn, increases the pressure in the refrigerant line to the point that the refrigerant does not completely evaporate. As described above, the threshold pressure to move refrigerant circuit 58 from air-cooled condensing mode to water-cooled condensing mode at 706 (FIG. 7) is determined based on the assumption about the normal system operation 12, on

<img file="MX388293B_D0059.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY particular, the temperature of the recirculating air that passes through the evaporator. If the recirculating air temperature is now less than the basis for this assumption, the water temperature trigger threshold at step 706 may need to change. Accordingly, before checking the pressure at sensor 66 at step 916 for the preliminary threshold refrigerant pressure level, the control system checks, at 918, the pressure level at sensor 66 and determines whether the refrigerant line reached a level (in this example, one point forty kgf/cm² (twenty psig) below preliminary threshold refrigerant pressure level, or 38.6 kgf/cm² (550 psig) indicating a probability that the control system will need to transition system 12 from water-cooled condensing to air-cooled condensing at 918. If the refrigerant line pressure at 66 does not exceed this level at 918, control system 56 proceeds directly to step 916.

However, if the refrigerant line pressure does not exceed the anticipated pressure level at 918, then at 920, the control system 56 acquires the entering water temperature from the water temperature sensor 152 (FIG. 2, FIG. 3). , Figure 4, Figure 5 and Figure 6). Because the temperature of the water in the tank 30 and therefore

<img file="MX388293B_D0060.tif" />

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MEXICAN INSTITUTE OF INDUSTRIAL PROPERTY that flows into the system 12 through pipe 14, tends to vary directly with the temperature of the air in space 16, the control system 56 measures the water temperature as an alternate server of the temperature of air. However, it should be understood that the control system 56 may alternatively measure the temperature of the interior space 16 directly from a temperature sensor or thermostat that is located in the space 16 and is in communication with the control system. 56. If pressure sensed at 916 then triggers the transition of system 12 from an air-cooled condensing mode to a water-cooled condensing mode, control system 56 adjusts the water temperature trigger threshold to be used at step 706 , at step 922. If the water temperature measured at step 920 is below 40.5°C (105°F), the control system changes the water temperature trigger threshold for use at 706 to 29.4° C (85°F). If the water temperature measured in step 920 is between 40.5°C (105°F) and 43.3°C (110°F), the water temperature trigger threshold is 32.2°C (90°F) at 922. If the measured water temperature in step 920 is between 43.3°C (110°F) to 46.1°C (115°F), the temperature trigger threshold for step 706 is 35°C (95 °F). If the water temperature measured in step 920 is

<img file="MX388293B_D0061.tif" />

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL is between 46.1°C (115°F) and 48.8°C (120°F), the water temperature trigger threshold is 36.1°C (97°F) at 922. If the measured water temperature in the stage 920 is greater than 48.8°C (120°F), the water temperature trigger threshold is 37.7°C (100°F). These actuator level temperatures can be determined, for example, by trial and error. After resetting the actuator threshold at 922, the control system proceeds to transition system 12 from air-cooled condensing mode to water-cooled condensing mode, at 907.

Modifications and variations to the particular embodiments of the present invention may be practiced by those skilled in the art, without departing from the spirit and scope of the present invention, one or more embodiments of which are set forth with particularity in the appended claims. Furthermore, it is to be understood that aspects of the various embodiments may be interchanged in whole or in part. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention which is further described in the appended claims.