Heat pump system

Abstract

The invention relates to a heat pump system for heating and / or cooling fluid, wherein the system comprises at least first and second heat pump units each configured for heating and / or cooling fluid; at least one temperature sensor related to / in connection with at least the first heat pump unit for determining the inlet temperature and / or outlet temperature of the fluid at the first heat pump unit, and a master control unit for (common or joint) control of the first and second heat pump units on the basis of the determined inlet and / or outlet temperature of the at least one temperature sensor, wherein the master control unit is configured such that the master control unit selects a primary heat pump unit from the at least first or second heat pump unit to meet a heat and / or cooling demand and wherein the master control unit is configured such that it selects the at least one temperature sensor of the primary heat pump unit for determining the inlet and / or outlet temperature of the fluid at or in the primary heat pump unit to meet said heat and / or cooling demand.

Description

[0001] Heat pump system

[0002] Technical field

[0003] The present invention relates to a heat pump system and a method for operating a heat pump system. Additionally, the invention relates to a data processing device comprising means for carrying out the method, a computer program product, computer readable data carrier and a data carrier signal. In addition, the invention relates to a combustion appliance with such a data processing device .

[0004] Background

[0005] Heat pump systems may comprise a plurality of heat pump units, which are fluidly connected and may operate in cascade. To control the plurality of heat pump units and in particular the compressor speeds at which the heat pump units operate, an external temperature sensor may be installed in the fluid circuit to determine the temperature of the fluid, e.g. in a manifold or collector tank. However, known controls often turn out to be prone to failure and implementation thereof may have drawbacks. The external sensor, also called a temperature probe can be far away from heat pump units, thus electrical cables are needed between the temperature probe and the heat pump units. Indeed, it is necessary that the signal of the temperature measured usually by the temperature probe in the manifold area is transferred by a physical / electric system such as a wire. The use of wire is not desired because installing the wire requires additional work and potentially civil engineering work to modify the building to allow the wire or cable to pass through. This is expensive, uncomfortable, detracts from the aesthetics and visual integration and may even be impossible in some cases such as due to, for example architectural constraints, or co-ownership of the building. It is conceivable to use a wireless connection, but this would require wireless elements, in other words an emitter and a receptor, and wireless compatibility. Wireless capability is not always possible due to for example several walls or floors between emitter and receptor. Using a wireless connection thus also creates additional cost and there is a strong risk regarding the reliability if there is any reconnection such as due to damage, or internet loss. For these reasons, wire is preferred even if there are several drawbacks.

[0006] EP0204521A2 is directed to providing a system controller for controlling one or more heat pumps in a 4-pipe configuration, which can provide hot and cold water simultaneously. EP0204521A2 addresses the problem of controlling heating and cooling systems, particularly those incorporating heat pumps or refrigeration units, in an efficient and effective manner. Specifically, it aims to optimize the operation of multiple heating and cooling sources, such as heat pumps, to meet the heating or cooling demand of a system while minimizing energy waste and operating costs. In order to achieve this goal EP0204521A2 discloses a heating and / or cooling system including a system controller and at least two heating and / or cooling sources for delivering heated or cooled working medium, in response to a demand on the system for heating or cooling, wherein the heating and / or cooling sources are arranged to operate in flow parallel with respect to the delivery of the heated or cooled working medium, and the system controller is arranged to generate command signals for the heating and / or cooling sources to instruct an increase or decrease in heating and / or cooling capacity depending on the temperature of mixed working medium from parallel outlets of the heating and / or cooling sources. EP0204521 A2 further discloses individual controllers of the one or more heat pumps. EP0204521A2 further discloses the conventional temperature probe by way of which the system controller monitors the temperature of the mixed water from the outputs of the heat pump by means of a temperature sensor associated with the mixed supply water conduit. When the temperature sensor indicates that the water temperature is outside the set-point dead-band and an increase in capacity is required, a load signal is transmitted to the lead unit as set by the lead-lag sequence determining logic of the system controller.

[0007] EP3136013A1 is directed to providing a heat pump chilling system and method of controlling said system so that the system can activate a plurality of heat pump chilling devices quickly and efficiently, without either overwhelming the system with too many devices or requiring a long activation time and discloses a heat pump chilling system . The heat pump chilling system comprises a plurality of heat pump chilling devices connected in parallel with a load by using an inlet pipe and an outlet pipe, and a heat medium, such as water and an antifreeze solution, serving as a medium for exchanging heat energy circulates between the plurality of heat pump chilling devices and the load. The inlet pipe starts from the load and branches off toward the plurality of heat pump chilling devices and allows the heat medium to flow therethrough. The outlet pipe causes the heat medium that has exchanged heat in the plurality of heat pump chilling devices to merge and flow toward the load. Furthermore, the heat pump chilling system includes an inlet temperature sensor that detects the temperature of water, as an inlet temperature Ti, in the inlet pipe immediately before the water is distributed to the plurality of heat pump chilling devices, and also includes an outlet temperature sensor that detects the temperature of water, as an outlet temperature To, in the outlet pipe immediately after the water is merged from the plurality of heat pump chilling devices. In other words, the inlet temperature sensor detects the temperature of the heat medium that is to flow into the load as the inlet temperature Ti, and the outlet temperature sensor detects the temperature of the heat medium flowing out from the load as the outlet temperature To. In other words, EP3136013A1 discloses a conventional temperature probe.

[0008] EP3995763A1 is directed to providing a refrigeration cycle apparatus that can prevent temperature decrease of a heat medium, while avoiding overlapping of defrosting periods of multiple refrigeration cycle units that control the temperature of the heat medium. In order to achieve this, EP3995763A1 discloses an air conditioning apparatus including a heat source device, a load device, pipes, and a pump. The heat source device is a refrigeration cycle apparatus including a first refrigeration cycle unit and a second refrigeration cycle unit. In each of the first refrigeration cycle unit and the second refrigeration cycle unit, a circulation path for refrigerant is formed. A heat medium is circulated between heat source device and load device, through pipes and pump. In the following description, water is exemplified as a heat medium. The heat medium, however, may be brine or the like. The temperature of the heat medium is measured by way of a temperature sensor which is not shown or further described in EP3995763A1 .

[0009] US20110315093A1 is directed to properly distributing the capacity of heat pump units, of a hot water system using multiple heat pump units, based on the required capacity, resulting in highly efficient operation. Additionally, US20110315093A1 is directed to allowing for the flexible use of heat pump units with low minimum operating capacity, further enhancing the flexibility of the fluid heating system. In order to achieve this goal US20110315093A1 discloses a hot water system including a fluid circuit in which water circulates and three heat pump cycles in which refrigerant circulates. The hot water system further comprises a tank, a pump and a system control apparatus for controlling operations and detecting the states. The control apparatus includes a detecting part, a determining part, and a controlling part. The detecting part measures the temperature of the water stored in the upper and lower parts of the tank using a thermometer. The determining part compares the temperature of the water measured by the detecting part with temperature required by a user through an operation panel and calculates the heating capacity which is necessary for the hot water system as a whole (i.e., the heating capacity required by the tank). The determining part determines the heating capacity of each unit in such a way that the total heating capacity of the heat pump units reaches the necessary heating capacity, and further, in such a way that the total COP of the heat pump units satisfies a predetermined condition. The controlling part controls each water quantity regulating valve in such a way that the heating capacity of each unit reaches the heating capacity determined by the determining part.

[0010] CN113883579A is directed at providing a water system air conditioner, which solves the problem of hydraulic imbalance. The hydraulic imbalance resulting from the hydraulic power being relatively balanced by manually adjusting the manual water valve of each heat pump unit. In case of a large number of heat pump units in parallel, and each heat pump unit may be turned on and off, there are many possible combinations for starting up the heat pump units, and manual adjustment of the water valve cannot take into account all operating conditions. Thus, CN113883579A discloses a water system air conditioner, comprising a plurality of heat pump units, each of which has a water inlet pipe, a water outlet pipe, a water pump and a water flow control valve, the water inlet pipes of the plurality of heat pump units are connected in parallel, and the water outlet pipes of the plurality of heat pump units are connected in parallel. The controller is configured to determine the opening of the water flow control valve of each heat pump unit in the on-state according to the ratio of the water pump capacity of each heat pump unit in the on-state to the sum of the water pump capacities of all the heat pump units in the on-state when the water system air conditioner is turned on or the on / off state of any heat pump unit changes. The water flow control valve opening of each heat pump unit in the on-state is determined according to the ratio of the water pump capacity of each heat pump unit in the on-state to the sum of the water pump capacities of all the heat pump units in the on-state. The controller is further configured to when the on / off state of each heat pump unit does not change, the opening of the water flow control valve of each heat pump unit in the on state is controlled according to the actual temperature difference between the inlet and outlet water of each heat pump unit in the on state and the target temperature difference. Furthermore, the water flow control valve opening of each heat pump unit in the startup state is controlled according to the actual temperature difference between the inlet and outlet water of each heat pump unit in the startup state and the target temperature difference . The water system air conditioner further comprises a flow detection device is provided on the water inlet pipe or the water outlet pipe of each heat pump unit for detecting the water flow in the water inlet pipe or the water outlet pipe. The heat pump units can communicate with each other, and one of the heat pump units is selected as a master unit, and the other heat pump units are slave units, and the master unit controls the operation of each slave unit. When the water system air conditioner is turned on, the controller starts to work and first executes control (1 ), then detects the on / off status of each heat pump unit. Control (1 ) refers to determining the opening of the water flow control valve of each heat pump unit in the on-state according to the ratio of the water pump capacity of each heat pump unit in the on-state to the sum of the water pump capacities of all the heat pump units in the on-state. If it is detected that the on / off status of any heat pump unit has changed, control (1 ) is executed; if the on / off status of all heat pump units has not changed, control (2) is executed. After control (2) is executed, if the water system air conditioner is not shut down, the on / off status of each heat pump unit is rechecked. Control (2) refers to controlling the opening of the water flow control valve of each heat pump unit in the on-state according to the actual temperature difference between the inlet and outlet water of each heat pump unit in the on- state and the target temperature difference. In other words, each heat pump has its own temperature probe installed in its water inlet (connected to the manifold outlet). This sensor measures the water temperature entering inside the heat pump, before the waters reach the heat exchanger and then goes out of the heat pump and reaching back the manifold (manifold inlet).

[0011] JP2004340533A is directed to providing a heat pump hot water supply and air conditioning system that can achieve simultaneous operation of hot water supply and air conditioning with high efficiency, while also achieving a smaller hot water tank capacity by increasing the temperature and capacity during hot water supply operation and discloses a heat pump hot water supply air conditioning system comprising a heat pump hot water supply means (1 1) with a hot water supply function, a heat pump hot water supply air conditioning means (17) with a hot water supply function and a cooling and heating function, a hot water storage tank (22) for storing hot water heated by the heat pump hot water supply means (11 ) and the heat pump hot water supply air conditioning means (17), and an indoor unit. The hot water supply air conditioning system further comprises a temperature control means (28), which controls a circulation pump (27) so that the detection signal of a water temperature sensor (29) at the outlet of a water heat exchanger a (25) and a water heat exchanger b (26) becomes a predetermined signal. The water heat exchanger a (25) is in a heat exchange relationship with a hot water supply heat exchanger a (13) of the heat pump hot water supply means (1 1 ), through which water from the bottom of the hot water storage tank (22) or water that has passed through a water supply pipe flows. The water heat exchanger b (26) is in a heat exchange relationship with a hot water supply heat exchanger b (19) of the heat pump hot water supply air conditioning means (17), through which water from the bottom of the hot water storage tank (22) or water that has passed through a water supply pipe flows. The circulation pump (27) controls the flow rate of water flowing through the water heat exchanger a (25) and the water heat exchanger b (26).

[0012] W02017086870A1 is directed to providing a flexible and simple heat pump system that can optimally distribute thermal energy between a building and its environment at high average efficiency, while also monitoring the system for damage at an early point before more severe damage results. Existing heat pump systems can be complex and costly, with numerous valves and other components that are difficult to detect and repair. In order to reach this goal, WO2017086870A1 discloses a heat pump system that selectively directs the heat medium to only the primary heat sources or sinks with the highest temperature, or to several of them, based on the temperature sensor readings.

[0013] WO2015155543A1 is directed to a system for heating and cooling fluids using a heat pump. The system includes a heat exchanger with a primary inlet and a secondary outlet, a temperature sensor, and a controller. The controller uses the temperature sensor to control the heat pump to maintain the fluid at a desired temperature. The system can efficiently heat and cool the fluid, and the energy input to the system is greater than the energy output. The system has a higher Coefficient of Performance (COP) and is disclosed to use less carbon dioxide (CO2) than traditional systems.

[0014] EP4375589A1 is direct to providing a more effective solution for creating a high temperature gradient and achieving the desired temperature. The connection is applicable for both heating and cooling. EP4375589A1 discloses a connection between heat pumps that allows for efficient heating and cooling. The connection is made through a common fluid circuit, which is connected to a hydraulic pump. The hydraulic pump circulates the fluid in the common circuit, and temperature sensors are installed before and after the connection to monitor the temperature. The connection is controlled by a controller that communicates with the temperature sensors to ensure the desired temperature is achieved.

[0015] The object of the invention is to provide a heat pump system which does not require a wired or wireless connection of the heat pump units of such a system with a separate temperature probe. In addition, it is an object of the invention to provide a more versatile heat pump system compared to the prior art which allows for addition or replacement of a heat pump unit without the need to plan for such an occurrence prior to initial installation to account for wire-compatibility and / or wireless-compatibility of the heat pump system and the installation site. Summary of the invention

[0016] The invention relates to a heat pump system for heating and / or cooling fluid, wherein the system comprises at least first and second heat pump units each configured for heating and / or cooling fluid; at least one temperature sensor related to / in connection with each of the at least the first and second heat pump unit for determining the inlet temperature and / or outlet temperature of the fluid at or in the at least first or second heat pump unit, and a master control unit for common (or joint) control of the at least first and second heat pump units on the basis of the determined inlet and / or outlet temperature of the at least one temperature sensor, in particular at or in the first or second heat pump unit, wherein the master control unit is configured such that the master control unit selects a primary heat pump unit from the at least first or second heat pump unit to meet a heat and / or cooling demand (also in short referred to as a heating requirement in the application) and wherein the master control unit is configured such that it selects the at least one temperature sensor of the primary heat pump unit for determining the inlet and / or outlet temperature at or in the primary heat pump unit to meet said heat and / or cooling.

[0017] The primary heat pump unit can be selected based on a set of pre-defined parameters. In particular the selection can be based on working hours of the at least first or second heat pump unit in order to ensure that the heat pump system uses the heat pump units in a balanced manner and thus ensuring the lifetime of the heat pump units and heat pump system are optimized and thus that the total cost of ownership and optimizes the overall reliability of the heat pump system. Further parameters that can be taken into account for the selection can be efficiency of the heat pump unit to meet the heat and / or cooling demand, such as the energy efficiency ratio which relates to the cooling efficiency of a heat pump unit, the heating seasonal performance factor which relates to the overall heating efficiency of a heat pump during the heating season, the seasonal energy efficiency ratio, or the temperature efficiency; and / or a noise limitation parameter, and / or the COP (Coefficient of Performance), or the maximum COP (COPmax), and / or the load distribution of the heat and / or cooling demand, and / or the capacity of the respective heat pump unit.

[0018] The energy efficiency ratio (EER) is the ratio of the cooling output (in watts) to the electrical energy input (in watts).

[0019] The heating season performance factor is the ratio of the total heat output (in joules) to the total electrical energy input (in kilowatt-hours) over the heating season.

[0020] The seasonal energy efficiency ratio measures the cooling efficiency of a heat pump over an entire cooling season. It is similar to the energy efficiency ratio (EER) but takes into account varying temperature conditions throughout the season.

[0021] The temperature efficiency is related to the heat pump unit efficiency which can vary with outdoor temperatures. At lower temperatures, heat pumps can become less efficient. This relationship can be defined as the heat pump efficiency vs. the outdoor temperature.

[0022] The coefficient of performance of a heat pump unit is a measure of its efficiency, It is defined as the ratio of the heat energy provided (or removed) by the heat pump unit to the electrical energy consumed to do so. The COP is expressed as COP=Q / W where Q is the amount of heat energy transferred (in Joules) and W is the work input or electrical energy consumed by the heat pump (in Joules).

[0023] The Maximum COP relates to the maximum theoretical efficiency for a heating process and is calculated using the temperatures on the hot and cold sides of the heat pump. The formula is COPheating = Th / Th-Tc where Th is the absolute temperature on the hot side and Tc is the absolute temperature on the cold side.

[0024] According to the invention, the temperature is determined in connection with the primary heat pump unit, wherein the temperature as determined is not only used for control of the primary heat pump unit, for example the first heat pump unit, but also for control of the heat pump unit not selected as the primary heat pump unit and any further heat pump unit, for example the second heat pump unit. Specifically, the temperature in connection with / related to the primary heat pump unit may refer to the temperature in (inside) the primary heat pump and / or the temperature in a port of the primary heat pump unit, e.g. its direct piping connection, which may be outside the housing of the first heat pump. In other words, the temperature determined in connection with the primary heat pump unit is used to control the heat pump system in response to the respective heat and / or cooling demand. To illustrate the principle by way of example, in response to a heat and / or cooling demand the master control unit selects e.g. the first heat pump unit as the primary heat pump unit to meet said heat and / or cooling demand. There is at least one temperature sensor present in each of the first and second heat pump units. In case of additional heat pump units at least one temperature sensor is present also in any further heat pump unit in the heat pump system. As a consequence of the selection of the first heat pump unit as the primary heat pump unit to meet said heat and / or cooling demand, at least one temperature sensor which is related to the first heat pump is selected and used by the master control unit to monitor and control (directly or indirectly) the operation of the first and the second heat pump units and any further heat pump unit to meet the heat and / or cooling demand. The master control unit is in other words configured to use the temperature measured in relation to the selected primary heat pump unit, in particular in or at the inlet and / or outlet of the primary heat pump unit for controlling the heat pump system in response to a heat and / or cooling demand .

[0025] As another example to explain the principle of the invention, the heat pump system allows that when only one of the heat pump units is working as the primary heat pump unit and the primary heat pump unit has to go into a defrost mode, the master control unit can select the secondary heat pump unit to start by demand based on the temperature sensor data of the primary heat pump unit. Thus, a common probe in a collector is not needed to regulate the two heat pump units, as is usual in the known systems.

[0026] The invention allows easily adding a further heat pump unit to an existing heat pump unit or to a plurality of existing heat pump units. This addition is even possible if the extension was not planned initially. It is also possible to introduce heat pump units with different performance to the other heat pump units without initial planning of such an addition or exchange being needed. This is constructively and from an installation point of view easily possible as it is not needed to add further wiring or wireless connectivity, As an example it is easily possible to install a heat pump system comprising for example a first and second heat pump unit initially and then, as for example a building is later expanded, to add a further unit years later as part of such a building expansion.

[0027] Thus, in comparison to a heat pump system requiring a separate temperature probe, a heat pump system according to the invention allows for the control of the system without requiring a wired or wireless connection of the heat pump units to the separate temperature probe. Thus, such a heat pump system according to the invention allows for installation without the need to install the wiring which requires additional work and potentially civil engineering work to modify the building to allow the wire or cable to said separate temperature probe to pass through. The common kind of installation of a heat pump system requiring a separate temperature probe is expensive, uncomfortable, and detracts from the aesthetics and visual integration and may even be impossible in some cases such as due to, for example, architectural constraints, or co-ownership of the installation site or building. The heat pump system according to the invention also does not require a wireless connection of the heat pump units and the temperature probe. The wireless connection would require wireless elements, in other words an emitter and a receptor, and wireless compatibility. Wireless capability is not always possible due to for example several walls or floors between emitter and receptor. Using a wireless connection thus also creates additional cost and there is a strong risk regarding the reliability if there is any reconnection such as due to damage, or internet loss.

[0028] In addition, such a heat pump system according to the invention allows for more versatility compared to a wired or wireless system with a temperature probe. Such a heat pump system according to the invention therefore allows the addition or replacement of a heat pump unit without the need to plan for this in advance and without the need to ensure wire-compatibility or wireless-compatibility of the system or the installation site. In other words, the heat pump system according to the invention thus allows for an improved and more versatile installation avoiding the drawbacks of known heat pump systems requiring a separate temperature probe.

[0029] The corresponding common control unit using the determined temperature is referred to as the master control unit, wherein the second heat pump unit (and any further heat pump unit) have a control unit acting as a (individual) slave control unit (for the individual heat pump unit). For illustrating the invention by way of example in other words, the master control unit is a central control unit that manages and coordinates the operation of the at least first and second heat pump units and of any additional heat pump unit of the heat pump system. The master control unit ensures that all heat pump units in the system work together, in particular efficiently together, to meet the respective heat and / or cooling demand. The master control unit is for example further capable of controlling the distribution of the load among the heat pump units, ensuring that each heat pump unit operates within its performance range, in particular in its more efficient or even optimal performance range. The master control unit communicates with each heat pump unit, sending control signals / commands and optionally receiving information. The master control unit can monitor and adjust the operation of each heat pump unit (directly or indirectly) and can optimize the overall system efficiency. The master control unit can optionally further detect and diagnose faults or inefficiencies in an individual heat pump of the overall system.

[0030] In an embodiment, the heat pump system comprises a slave control unit in connection with / related to the second heat pump unit for (individual) control of the operation of the second heat pump unit and wherein the master control unit and the slave control unit are configured such that the master control unit sends control signals for the second heat pump unit on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit to the slave control unit, and the slave control unit receives said control signals and controls the operation of the second heat pump unit according to the received control signals.

[0031] The individual (slave) control unit may handle the internal control of the respective second heat pump unit(s). The slave control unit in other words is configured to execute the control signals / commands of the master control unit. The slave control unit follows the instructions received from the master control unit, such as adjusting settings or turning on / off. The salve control unit can optionally be configured to send updates to the master control unit, such as performance metrics data and / or operational status. The slave control unit manages the local operation of its heat pump unit, ensuring that it operates within the designated parameters received from the master control unit, such as the load distribution parameters received by the master control unit. The slave control unit can monitor its heat pump for any faults or inefficiencies and can be configured to alert the master control unit.

[0032] Suitable control signals / commands the master control unit can send to the slave control unit for execution are for example an on / off control signal / command, a standby control signal / command, a monitoring control signal / command, a mode control signal / command, a temperature control signal / command or time control signal / command an activation or initializing control signal / command, and a change control signal / command, such as changing the compressor speed to change the operation of a heat pump unit which is active.

[0033] Hence, the plurality of heat pump units of the heat pump system shares a common control unit, namely the master control unit. The common control unit of the invention may control switching on / off of the first and second heat pump units and the associated speed management / request of the respective compressor. Thus, the master control unit can control the heat pump system according to the invention efficiently and consistently.

[0034] Optionally, the master control unit can send control signals / commands to the heat pump unit controlled by the master control unit (directly) or to the (indirectly controlled) heat pump unit controlled by the slave control unit to switch the respective heat pump unit into a monitoring mode, or a standby mode or the on / off mode.

[0035] The standby mode of the heat pump unit means that the heat pump unit is temporarily inactive but powered on. This mode can be activated based on certain parameters directed to ensure protecting the heat pump system and / or to conserve energy when full operation of the heat pump system is not needed. The standby mode selection can be based on one or more of the parameters. Suitable parameters comprise for example energy conservation, frost protection, overheating protection and system reset. The energy conservation parameter means that the heat pump unit is not actively heating or cooling. Thus, said heat pump unit can enter the standby mode to save energy while still being ready to resume operation quickly. The frost protection parameter is particularly relevant in colder climates, in those climate conditions standby mode can help prevent the respective heat pump unit from freezing by periodically running a defrost cycle . The overheating protection means that if the system detects excessively high temperatures, it may enter standby mode to prevent damage. System reset means that the standby mode can also be a part of the system's reset process after events like power outages or circuit breaker trips.

[0036] The monitoring mode refers to a state of the respective heat pump unit where the heat pump unit checks and optionally records operational parameters to ensure optimal performance, efficiency and safety. The monitoring mode selection can be based on one or more of the parameters. Suitable parameters include performance tracking, temperature monitoring, system health, energy usage and remote access.

[0037] Performance tracking means that the heat pump unit monitors its performance metrics, such as energy consumption, heat output, efficiency, and Coefficient of Performance (COP). Temperature monitoring means that the heat pump unit keeps track of temperatures at different points, such as the water flow and return temperatures, the outside air temperature (e.g. for air-source heat pumps), and the source inlet and / or outlet temperatures (e.g. for ground-source heat pumps). System health means that the heat pump unit detects any anomalies or malfunctions in the heat pump unit, allowing for timely maintenance and repairs.

[0038] As an example, the monitoring mode can comprise the respective heat pump unit checking security parameters such as temperature of the heat pump unit. Energy usage means that the heat pump unit records the electricity consumption and heat production, providing data for analyzing energy usage patterns and optimizing efficiency. Remote access means that in case the heat pump unit offers remote monitoring capabilities, the monitoring mode allows access to performance data and to send alerts via for example a wireless or internet connected system.

[0039] Optionally, the master control unit can send temperature control signals / commands and / or time control signa Is / commands and / or mode control signals / commands to the heat pump unit controlled by the slave control unit or to the heat pump unit controlled by the master control unit.

[0040] Optionally, the control signals / commands of the master control unit can comprise further data, depending on additional factors such power availability, noise reduction, environmental performance, risk of icing and / or de-icing ongoing. The master control unit can in other words send a control signal / command defining the mode to operate to the heat pump unit other than cooling or heating. For example, the master control unit can send a control signal / command to the primary heat pump, for example the first heat pump unit, and / or to the heat pump unit not chosen to be the primary heat pump unit, for example the second heat pump unit, which is a control signal / command defining the mode to operate other than cooling or heating.

[0041] Optionally, the master control unit can take noise or energy limitations of the heat pump units of the heat pump systems into account. In such an embodiment, the master control unit can select to meet the heat and / or cooling demand using the primary and the secondary heat pump unit based on noise parameters. The master control unit can for example take a silent mode of the respective heat pump unit into account. The silent mode of a heat pump unit means that the noise limitation parameters of the heat pump unit limit the actual performance of the heat pump unit. In particular the compressor and the fan are noise emitters and the limitation of noise emitted by the heat pump unit leads to a reduced power output compared to the power output the heat pump unit could provide if the noise limitation parameters are not taken into account. In an example the silent mode only allows the heat pump unit to provide 70% of the power it could provide to stay within one or more predefined noise limitation parameters. In other words, the rpm of the compressor and the fan can be limited by the master control unit compared to their maximum capacity to stay within said predefined one or more noise limitation parameters. Thus, the master control unit can incorporate the silent mode, for example in the evening and / or at night to ensure that the noise of the heat pump system stays within acceptable levels. The master control unit can thus choose a primary heat pump unit and a secondary heat pump unit in silent mode to meet the respective heat and / or cooling demand as the silent mode will limit the power of each heat pump unit to stay within the noise limitations of the silent mode.

[0042] Optionally, the master control unit can select more than one heat pump unit to meet the respective heat and / or cooling demand based on a first and a second selection: The first selection of the primary heat pump unit is preferably based primarily or fully on the working hours of the heat pump units of the heat pump system and is in particular aimed at balancing the heat pump unit working hours to optimize the lifetime of the heat pump system. However, the first selection can also take additional parameters into account such as the COP, load distribution, maintenance status, zone parameters, noise limitation parameters. The second selection can be based on the working hours of the remaining heat pump units in the heat pump system and can further include additional parameters such as the COP, efficiency, silent mode / noise limitation; capacity of the respective heat pump units.

[0043] The slave control unit in connection with the second heat pump unit may be a control unit e.g. in a control box, inside the housing of the second heat pump unit or a control unit outside the housing of the second heat pump unit, for control of the second heat pump unit.

[0044] The master control unit can in other words send control signals / commands to the slave control unit. This can be described as only the master control sends control signals / commands to the slave control unit and the slave control unit only receives control signals / commands from the master control unit. The master control unit does not receive any feedback or status updates from the slave control unit unless explicitly requested by the master control unit. The communication of the master control unit is thus a unidirectional communication where the master control unit sends control signals / commands to the slave control unit and the slave control unit only responds to the control signals / commands. This requires only limited communication overhead and can be achieved with a relatively simple protocol and setup.

[0045] Suitable protocols allow communication via a local connection, bus, or network, in particular using a bus communication protocol in particular the OpenTherm protocol, or the Modbus protocol, or the EEBus protocol, or the CAN protocol, including the CANopen protocol or the DeviceNet protocol, or the BACNet protocol. Bus communication protocols, such as OpenTherm, or Modbus, or EEBus (energy efficient bus), or BACNet or CAN protocol allow for a temperature adaptive demand.

[0046] According to the invention, by way of a temperature sensor in connection with (e.g. in or at) the first heat pump unit, the inlet or outlet temperature of the fluid (to be) heated / cooled in the first heat pump unit is determined, in particular at the inlet pipe or at the outlet pipe of the first heat pump unit. Optionally, a temperature sensor for determining the inlet temperature and a temperature sensor for determining the outlet temperature is provided in the first heat pump unit. The at least one temperature sensor is located close to / at / in the primary heat pump unit, e.g. the first heat pump unit, and may, additionally, be used for further purposes, such as for other control aspects. No extra temperature sensor for the common control in terms of the present invention may need to be installed (somewhere else) in the system, as no extra temperature sensor may be necessary for the common control. Thus, hardware and installation costs may be lowered, as fewer components, in particular no additional temperature sensor and corresponding communication hardware may be needed. However, it is by no means excluded that further temperature sensors are provided in the system. E.g. for the internal control of the heat pump unit(s), additional temperature sensors may be needed.

[0047] For the invention, it is preferred to base the control on the input temperature at the first heat pump unit. However, additionally or alternatively, the control may be based on the output temperature of the first heat pump unit. Hence, one of the temperature sensors of the first heat pump unit is optional for the present invention; however, is understood that often both temperature sensors may be provided in the first heat pump unit.

[0048] Compared to measuring the temperature of the fluid e.g. in a collector tank or manifold for the control of the plurality of heat pump units, a specific advantage may be that no communication, let alone connection from a temperature sensor in the collector tank (which is typically installed in a building) to the heat pump units (which are often installed outside the building) is needed. It is evident that such connection, e.g. by way of a wire or wireless, is intricate in view of the building wall to be crossed and a relatively large distance. As such potential drawbacks may be avoided by the present invention, the present invention may be more reliable and less prone to failure. This increases the reliability and accuracy to achieve the heating and / or cooling target.

[0049] Compared to an external and separate common control unit installed to drive all the units, according to the invention, all heat pump units may have their own control unit so each heat pump unit may run on its own if installed alone. And, when several units are connected, e.g. to the same HM I, the control of one heat pump unit may become the master and the other ones may become the slaves. A heat pump system of the invention is seen as versatile in that further heat pump units (with further control units) may be added even after installation of the initial heat pump system, in particular after installation of the master control unit. The control units of further heat pump units may serve as further slave control units.

[0050] The present invention allows for parallel installation of a plurality of heat pump units (i.e. of at least two heat pump units), i.e. in cascade, and a common master control. More specifically, the master control unit may adjust operation of the plurality of heat pump units based on various parameters, e.g. aiming at optimizing the coefficient of performance of the plurality of heat pump units as a whole and / or ensuring that the power and temperature requirement is fulfilled . Additionally, an attempt may be to prolong the overall lifetime of the heat pump system in its entirety by equalizing the running hours of the individual heat pump units amongst the plurality of heat pump units. This supports to extend the lifetime of the installation as a whole. Additionally, the heat pump system is more versatile compared to the prior art; the present invention allows for the addition or exchange of a heat pump unit in an existing heat pump system without the need to plan the installation to allow for this extension or replacement in advance. It further removes the need of having sensor wiring or connectivity from the heat pumps to a hydraulic separator or having the proper communication protocol for a replacement or extension heat pump which allows for determining each temperature of each heat pump unit separately for meeting a heat and / or cooling demand.

[0051] It is acknowledged that the temperature as measured by the temperature sensor in the first heat pump unit may slightly differ from the actual temperature of the fluid at other location in the fluid circuit, e.g. such as in a tank, due to potential thermal loss with ambient air in the pipe (reduction of temperature in case of heating mode, because the fluid of the system is hotter than ambient air). A corrective may be used to compensate for this thermal loss, depending of the insulation performance, the external conditions and the length of the connection between the circuitry, tank etc. and the first heat pump unit. In general, heat pump units of the present invention may be ground source or air source heat pump units. It is possible that different heat pumps are comprised in the plurality of heat pump units. For example, the first heat pump unit may be an air source heat pump unit, while the second heat pump unit is a ground source heat pump unit. However, it is preferable that the same type of heat pumps is present in the system. More preferably, the heat pumps have the same nominal (heating / cooling) capacity.

[0052] A heat pump unit of the invention may have its entire refrigerant circuit of the heat pump included in a single unit, representing a so-called monobloc unit. Alternatively, the heat pump unit may be divided into two separated sub-units, representing a so-called split system. In case of a split system, the heat pump unit may comprise a sub-unit (to be) installed indoor, and a sub-unit (to be) installed outdoor. For monobloc units, the single unit may be installed indoor or outdoor. The invention concerns both monobloc and split units. However, the invention may be of particular relevance when the heat pump unit is an outdoor monobloc unit, as the distance travelled by the heated fluid to the (indoor) tank is long, including passing through the wall(s) of the building in which the tank is installed.

[0053] It is conceivable that at least one of the heat pump units is for centralized heating / cooling, and at least another one of plurality of heat pump units is for decentralized heating / cooling. For example, a central heat pump unit may cover the base load and one or more decentralized heat pump units may cover peak loads.

[0054] The fluid heated / cooled by the heat pump system may be a liquid.

[0055] The fluid heated / cooled by the heat pump system may be used for central heating, e.g. emitting heating / cold to a building and may be preferably primary water in a closed loop circuit. Alternatively, the fluid may be the refrigerant of the frigorific circuit of the heat pump units.

[0056] In general, the present invention relates to a plurality of heat pump units i.e. to at least two heat pump units. If more than two heat pump units are provided, these further heat pump units (such as a third, fourth, fifth... heat pump unit) may correspond to the second heat pump unit as disclosed herein. In other words, the disclosure provided herein with respect to the second heat pump unit may extend to any third, fourth, fifth ... heat pump units, i.e. the remaining heat pump units of the plurality of heat pump units. In particular, each of these further heat pump units comprises a slave control unit as disclosed. Optionally, the master control unit and the slave control unit are configured to communicate with each other. This may mean that the master control unit and the slave control unit are configured to exchange signals. Hence, the reliability as to the control may be improved. In other words, master control unit and slave control unit are configured for two-way communication also referred to as bidirectional communication or two-way data exchange. To illustrate the principle, both the master control unit and the slave control unit can send and receive data. The slave control unit can for example send status updates, error messages and / or other information to the master control unit without being explicitly prompted. This allows for further enhanced feedback. This requires a more complex communication protocol to handle the two-way data exchange.

[0057] Suitable protocols allow communication via a local connection, bus, or network, in particular using a bus communication protocol in particular the OpenTherm protocol, or the Modbus protocol, or the EEBus protocol, or the CAN protocol, including the CANopen protocol or the DeviceNet protocol, or the BACNet protocol. Bus communication protocols, such as OpenTherm, or Modbus, or EEBus (energy efficient bus), or BACNet or CAN protocol allow for a temperature adaptive demand.

[0058] Optionally, the heat pump system comprises at least a further heat pump unit.

[0059] Optionally, the primary heat pump unit is selected based on a set of predefined parameters, in particu lar the numberof working hours of the selected primary heat pump unit and / or the capacity of the primary heat pump unit and / or heat load distribution and / or a zone parameter of the installation and / or the COP of the selected primary heat pump unit. In other words, values for the set of predefined parameters of the at least first and second heat pump unit are considered by the master controller, and the selection of the primary heat pump unit is based on the set of predefined parameters. Suitable parameters are the capacity of the heat pump unit and / or the heat load distribution and / or the zone parameter of the installation and / or the COP.

[0060] A zone parameter within the meaning of the application refers to settings or conditions assigned to different areas or zones within the area or building to be heated or cooled by way of the heat pump system. This allows for customized heating or cooling based on the unique requirements of each defined zone, such as temperature preferences, occupancy patterns and insulation levels or exposure to sunlight or the like.

[0061] Taking said parameters into consideration, alone or in combination, has the advantage that the heat pump system according to the invention can be even more optimally balanced taking the performance of the heat pump units, the working hours and / or the life span of the heat pump units into consideration, the system can be additionally optimized to require lower overall maintenance and replacement costs, contributing to long-term savings and further optimized reliability. In particular taking the COP into consideration further has the advantage of a reduced carbon footprint and additional optimization of the heat pump system in view of sustainability goals. Thus, the total cost of ownership, the overall performance and the sustainability can be further optimized by considering said parameters.

[0062] Optionally, the master control unit is configured such that the temperature sensor of the primary heat pump unit is used for controlling the secondary heat pump unit in case the master control unit selects at least a secondary heat pump unit to meet the heat and / or cooling demand. In other words, the temperature sensor of the primary heat pump unit is used for controlling the secondary heat pump unit, in particular for controlling the operation of the secondary heat pump unit to meet the heat and / or cooling demand.

[0063] Optionally, the master control unit is, at the same time, configured for individual control - in other words controlling the operation - of the first heat pump unit, and is optionally located in the first heat pump unit. In this case, the master control unit is not only responsible for the joint control of the first and second heat pump units, but also for control of the first heat pump unit with respect to individual control aspects. In this case, no separate control unit for individual control of the first heat pump unit needs to be provided. From a different perspective, this means that no additional control unit may need to be provided for the master control unit, but a control unit for the first heat pump unit may specifically be configured as (master) control unit also for control pertaining to the second heat pump unit. If the master control unit is also used to (individually) control the first heat pump unit, this may mean that the first heat pump unit also controls the second heat pump unit (and any further heat pump unit). In other words, the (master) first heat pump unit may be seen as imposing control on the remaining (slave) heat pump units. As heat pump units are often located (relatively) close to one another, transmission of control signals from the first heat pump unit comprising the master control unit to the second heat pump unit(s) can often be implemented with lower efforts. However, the present invention is not limited to a master control unit located in the same heat pump unit in which the temperature of the fluid is measured. It is conceivable that a master control unit is located outside any heat pump unit.

[0064] Optionally, the system comprises a tank for circulation of (primary) fluid, the fluid preferably being water-based (e.g. containing glycol), preferably water, wherein the tank has a tank supply pipe for supply with fluid from the first and / or second heat pump units, and a tank return pipe for return of fluid to the first and / or second heat pump units. The tank may be configured to heat and / or cool liquid (e.g. water) fora circuit in a building by way of the fluid heated and / or cooled by the first and / or second heat pump units, based on heat exchange between the fluid and the liquid in the tank. The circuit may be an open loop domestic circuit (e.g. sanitary water for tap water) or a closed loop circuit (e.g. for radiators). The tank may be free of a temperature sensor. In particular, the temperature of the fluid in the tank does not need to be measured for the control of the plurality of heat pump units.

[0065] Optionally, the at least first and second heat pump units are configured to operate in parallel. This means, that the heat pump units are in cascade. In particular, there may be a fluid connection providing fluid communication between the first and second heat pump units for joint heating and / or cooling of fluid and allowing for heating and / or cooling in parallel. E.g. a liquid circuit connects the heat pump units in parallel. The connection may be realized by at least two common pipes each going from the heat pump units to the liquid tank. Alternatively, each heat pump may be connected directly to the same liquid tank without common pipes.

[0066] Optionally, the mast control unit is configured such that the master control unit can communicate with the at least first and second heat pump units via a local connection, bus, or network, in particular using a bus communication protocol in particular the OpenTherm protocol, or the Modbus protocol, or the EEBus protocol, or the CAN protocol, including the CANopen protocol or the DeviceNet protocol, or the BACNet protocol.

[0067] The OpenTherm protocol of the OpenTherm Association is a communication protocol used in central heating systems to enable digital, bi-directional communication between for example a thermostat (controller) and a boiler. Using the thermostat example forexplaining the principle: OpenTherm uses a traditional untwisted 2-wire cable to connect the thermostat and the boiler. This cable is not polarity sensitive, meaning the wires can be connected in any order (Digital Communication). The thermostat (primary) sends a 32 -bit signal to the boiler (secondary) every second . This signal includes various control signals / commands and information, such as the desired water temperature. The boiler responds with its own data, such as its current temperature and status (Bi-Directional Data Exchange). Unlike traditional on / off thermostats, OpenTherm allows for more precise control. The thermostat can instruct the boiler to modulate its output, adjusting the water temperature gradually rather than simply turning on or off. This helps in maintaining a consistent temperature and improves energy efficiency (Modulating Boiler Control). OpenTherm is designed to be manufacturerindependent, meaning a thermostat from one manufacturer can, in principle, control a boiler from another. However, some manufacturer-specific features might affect compatibility (Compatibility and Flexibility). In smart home setups, OpenTherm can be integrated with other systems for more advanced control, such as room-by-room temperature management and remote monitoring via mobile apps (Enhanced Smart Home Integration).

[0068] The BACnet (Building Automation and Control Network) protocol uses a four-layer collapsed architecture that corresponds to the physical, data link, network, and application layers of the OS I model. The physical layer defines the physical means of data transmission. The physical layer supports various physical media, including Ethernet, RS-232, RS-485, ARCNET, and LonTalk. BACnet can be implemented over different network types, ensuring broad compatibility. The data link layer manages device-to-device communication within a network. BACNet includes several data link layer protocols such as MS / TP (Master-Slave / Token- Passing) which is used over RS-485 for reliable communication in smaller networks; BACnet / IP which encapsulates BACnet messages in UDP / IP packets for use over IP networks; or LonTalk which is used for communication over LonWorks networks. BACNet provides mechanisms for error detection and correction to ensure reliable data transmission. The network layer handles network-to-network communication and routing. The BACNet protocol manages addressing and routing of messages between different network segments. The BACNet protocol ensures that devices on different network segments can communicate effectively, even if they use different physical media. The application layer provides communication services and defines the data exchanged between devices. The BACNet protocol uses an object-oriented approach with standard objects (e.g., analog input, binary output) and services (e.g., read property, write property) to facilitate interoperability. The BACNet protocol defines how data is represented and exchanged, via data representation, thus ensuring that devices from different manufacturers can understand and process the information. The BACNet protocol allows for scalability and is thus suitable for both small and large building automation systems. The BACNet protocol allows for flexibility. The layered architecture makes BACnet a versatile and widely adopted protocol for building automation, enabling efficient and reliable control of HVAC, lighting, access control, and other building systems.

[0069] Modbus has become a widely adopted standard for industrial communication, allowing various devices to communicate over serial lines, ethernet, or the internet protocol suite. It’s known for its simplicity, reliability, and ease of implementation, making it a popular choice in many industrial environments. Modbus is designed to allow communication between devices like sensors, actuators, and controllers. Modbus operates on a master-slave (or client-server for Ethernet) architecture. The master device initiates communication, and the slave devices respond to the master's requests. Modbus supports both serial communication (RS-232, RS- 485) and Ethernet communication. This flexibility allows for Modbus to be used in a variety of network setups. The communication is based on a simple requestresponse model. The master sends a request to a slave device, specifying the action to be performed (e.g., reading or writing data), and the slave responds with the requested data or acknowledgment. Modbus defines a set of function codes that specify different types of operations, such as reading or writing data registers, reading input status, etc. These function codes are included in the request messages to indicate the desired action. Data exchanged between devices in Modbus is typically encoded in a simple binary format, with numerical values represented in 16-bit or 32-bit formats. Modbus includes error checking mechanisms to ensure data integrity during transmission, such as CRC (Cyclic Redundancy Check) or LRC (Longitudinal Redundancy Check) checksums. Each slave device on a Modbus network is assigned a unique address ranging from 1 to 247. The master uses these addresses to identify and communicate with specific slave devices on the network. The Modbus communication protocol is a communication standard in the sense that the protocol definitions are standardized. However, the Modbus protocol always needs to be implemented for the individual use case. This means that the control signals / commands to be transmitted between the individual devices in each individual use case need to be coordinated with each other. EEBus is a communication protocol designed to standardize the interface between various energy-relevant devices and systems, facilitating seamless interaction and interoperability. EEBus aims to enable efficient energy management by connecting and coordinating devices such as household appliances, electric vehicles, heat pumps, energy producers, and storage systems. EEBus is used in smart homes, buildings, and the broader energy grid to ensure that all connected devices can communicate effectively. EEBus is structured according to the Smart Grid Architecture Model (SGAM) and consists of several layers. The component layer comprises all physical devices in the respective system. The communication layer handles the communication protocols used to connect devices. EEBus primarily uses IP-based communication, including TCP / IP and UDP, to ensure compatibility with existing network infrastructures. The information layer defines data models and formats used for communication. EEBus uses the SPINE (Smart Premises Interoperable Neutral-message Exchange) specification to standardize the data exchanged between devices. The function layer specifies the services and functions that devices can perform. It includes the definition of use cases and the functional requirements for energy management, such as load control, energy storage management, and demand response, and energy monitoring. The organizational layer encompasses the standards, policies, and regulatory frameworks that govern the implementation and operation of EEBus. The SPINE specification is a core component of EEBus, providing a standardized way to represent and exchange data between devices. The Smart Home IP (SHIP) specification defines how EEBus messages are transmitted over IP networks, ensuring secure and reliable communication. EEBus is flexible, scalable, and interoperable, making it suitable for a wide range of applications in smart homes, buildings, and the broader energy grid .

[0070] The Controller Area Network (CAN) protocol is designed to facilitate efficient communication between multiple nodes in a network, primarily used in automotive and industrial applications. The physical layer of CAN uses a twisted-pair cable to reduce electromagnetic interference. The two lines are known as CAN-High (CANH) and CAN-Low (CANL). The data-link layer, medium access control MAC, manages how devices access the network and includes mechanisms for error detection and handling. CAN uses a non-destructive bitwise arbitration method to resolve conflicts when multiple nodes attempt to transmit simultaneously. The message with the highest priority (lowest identifier) wins. CAN includes several error-checking mechanisms such as cyclic redundancy checks (CRC), acknowledgment checks, and bit stuffing. Logical link control (LLC) manages the data link layer’s logic, including flow control, error handling and frame formatting. The frame structure comprises: the primary frame used for data transmission, consisting of fields such as: Start of Frame (SOF) which indicates the beginning of a frame. The identifier which specifies the priority of the message. A control field which contains information about the data length. A data Field which carries the actual data (up to 8 bytes). A CRC Field which is used for error checking. An ACK Field which indicates successful reception of the frame. The End of Frame (EOF) which marks the end of the frame. The remote frame requests data from another node. The error frame signals an error detected by a node. The overload frame which is used to inject a delay between data or remote frames. There are further protocols based on CAN such as CANopen protocol and DeviceNet protocol. CAN has the advantage of real-time communication ensuring timely data transmission, robustness due to high immunity to electrical interference and reliable error detection mechanisms. CAN is suitable for both small and large networks with multiple nodes. The CAN protocol allows devices to send selfanalysis data. The CAN protocol further allows real-time diagnostics and monitoring.

[0071] The CANopen protocol is a high-level communication protocol and device profile specification designed for embedded systems. The CANopen protocol is based on the Controller Area Network (CAN) protocol and is widely used in various industries, including industrial automation, medical equipment, and automotive applications. Each CANopen device has an object dictionary, which is a structured collection of all parameters that can be accessed via the network. This includes configuration parameters, process data, and diagnostic information. CANopen supports several communication models, including master / slave, client / server, and producer / consumer. These models facilitate different types of data exchange and control mechanisms. CANopen includes protocols for network management, allowing for the configuration, monitoring, and control of devices within the network. This includes handling device states such as initialization, pre- operational, operational, and stopped. CANopen defines device profiles for various types of devices, ensuring interoperability between products from different manufacturers. Examples include profiles for I / O modules (CiA 401 ) and motion control (CiA 402). CANopen can accommodate networks of varying sizes and complexities. The modular structure of CANopen allows for easy integration and expansion of additional nodes. CANopen ensures seamless interoperability between devices from different manufacturers due to standardized device profiles. CANopen supports real-time data exchange allows for implementation in applications requiring timely coordination. CANopen has inbuilt diagnostic and monitoring capabilities which facilitate efficient troubleshooting, reduction of downtime and enhances system reliability. CANopen further allows for reduced wiring capacity by supporting multi-device communication on a single bus. This allows for cost reduction and easier maintenance. CANopen further supports a wide range of data types, which includes integers, floats, strings and arrays. CANopen includes network management services such as dynamic node addressing and device state monitoring, simplifying the management and maintenance of the network. CANopen further allows for time-stamping messages, which makes CANopen suitable for applications requiring precise time measurements and synchronization.

[0072] The DeviceNet protocol DeviceNet is a network protocol used in industrial automation to facilitate communication between control devices such as sensors, actuators, and programmable logic controllers (PLCs). DeviceNet is built on the Controller Area Network (CAN) technology. DeviceNet uses the Common Industrial Protocol (CIP) for its application layer. DeviceNet follows a trunklinedropline topology, which simplifies wiring and allows for easy addition or removal of devices without disrupting the network. DeviceNet supports three data rates: 125 kbit / s, 250 kbit / s, and 500 kbit / s. The maximum network length varies with the data rate. One of the advantages of DeviceNet is that DeviceNet combines power and signal in a single cable, reducing the need for multiple cables and simplifying installation. DeviceNet supports both master-slave and peer-to-peer communication models. The protocol defines various device profiles, ensuring interoperability between devices from different manufacturers. This standardization helps in creating flexible and scalable systems. DeviceNet includes features for network management, such as node addressing and duplicate address detection, which help maintain network integrity and simplify troubleshooting. DeviceNet is reliable and cost effective. DeviceNet efficiently uses network bandwidth, ensuring that data transmission is optimized, and delays are minimized. The DeviceNet protocol supports a large number of nodes and high data rates, making it suitable for complex applications. DeviceNet includes features for easy network management, such as node addressing and duplicate address detection, which help maintain network integrity and simplify troubleshooting.

[0073] Optionally, the first and second heat pump units each have a heat pump capacity, wherein the master control unit is configured to (jointly) control the heat pump capacity of each of the first and second heat pump units based on the determined input and / or output temperature. If the control of the first and second heat pump units relates to the capacity of the heat pump units, operation of the heat pump system may effectively be improved and optimized.

[0074] Optionally, at least one of the first and second heat pump units comprises a compressor for compressing refrigerant and an inverter for modifying the capacity, in particular the speed of the compressor, and is configured such that the speed of the compressor is adjustable. More specifically, the inverter adapts the frequency of the alternating current so as to increase or decrease the frequency of the rotation. Preferably, the first and second heat pump units (and any further heat pump units of the plurality of heat pump units) comprises an inverter in addition to the compressor, so that the speed of the compressor of each of the heat pump units can be adjusted, i.e. is variable. Specifically, the speed of the compressor can be reduced, so that the compressor does not have to run at full speed when in operation. This means that the heat pump units may be modulated heat pump units, allowing for modulated operation. This is in contrast to a heat pump unit which merely allows for on / off-operation, wherein operation is only possible at full speed. Adjusting the speed of the compressor so that the compressor runs at a reduced speed is preferable compared to repeatedly or intermittently stopping the compressor, as this may help to increase the lifetime of the compressor and, hence, of the heat pump unit. Further, by adjusting the speed of the compressor, the workload of the heat pump unit to achieve the heat and or cooling demand may more accurately be met. This may help to save energy and, thus, costs.

[0075] Optionally, the master control unit is configured to control the compressor speed of each of the first and second heat pump units based on the determined input and / or output temperature, optionally such that the speed of at least one compressor does not exceed 90%, preferably not exceed 85% of the maximum speed of said compressor, and is more preferably between 40 and 85% of the maximum speed of said compressor. Depending on the heating and / or cooling target, the contribution of the plurality of heat pump units to achieve the target may be chosen accordingly. In particular, operation of the compressors at full speed may want to be avoided, which means that the speed of the compressor is preferably less than 100%. For example, if the heating and / or cooling target can be met by operation of one of the heat pump units, wherein the compressor runs at less than 80% of the maximum speed of said compressor, the other heat pump unit(s) may be stopped, meaning that the speed of the other heat pump unit(s) is zero. In other examples, one compressor may run at 60% of its maximum speed and the other compressor may run at 40% of its maximum speed rather than one compressor running at its maximum speed. Various controls which may aim at an optimized coefficient of performance are conceivable. It is noted that the heat pump units amongst the plurality of heat pump units may differ from each other as to their maximum speed of the compressor.

[0076] Preferably, all the heat pump units of the system have the same maximum capacity.

[0077] Optionally, the master control unit is configured to base the selection of the primary heat pump unit and / or the at least secondary heat pump unit and / or control on at least one of: the total running time, the remaining lifetime, the heat pump capacity, the noise level, status as to error or warning, and the icing and de-icing requirements of the first and / or second heat pump units. Determination of an appropriate control may relate to considerations pertaining to the entirety of the heat pump units or may relate to individual heat pump units. This may improve the lifetime of the individual heat pump units and / or of the entirety of the heat pump system.

[0078] Optionally, the master control unit is configured to control the at least first and second heat pump units such that, if the at least first and second heat pump units are each available to produce the heating requirement, in particular at 40 to 85% of its maximum speed, the heat pump unit with the lower / lowest total running time amongst the first and second heat pump units is chosen as only heat pump unit producing the heating requirement. Hence, if running one heat pump only is sufficient to produce the heating or cooling requirement and several heat pump are able to produce such requirement, the control may choose the unit with the lowest total running time. Thus, the control may aim at balancing the operating times of the heat pumps as much as possible.

[0079] If there are more than two heat pump units, the master control unit is configured to control the heat pump units such that, if one or more heat pump units are available to produce the heating requirement, in particular at 40 to 85% of its maximum speed, the heat pump unit(s) with the lowest total running time amongst the heat pump units is / are chosen as heat pump unit(s) producing the heating or cooling requirement. For example, if three heat pump units are provided, the master control unit may control the heat pump units such that, if the second and third heat pump units are available to produce the heating requirement, in particular at 40 to 85% of its respective maximum speed, the heat pump unit(s) with the lowest total running time amongst the second and third heat pump units is / are chosen as (sole) heat pump unit(s) producing the heating or cooling requirement. Hence, the heat pump which is / are used will be the one(s) with the lowest total running time and being able to produce the heating requirement by being between 40 and 85% of the maximum speed.

[0080] Optionally, the temperature sensor is located on an (outer) surface of a heat pump unit inlet pipe for determination of the inlet temperature of the first heat pump unit and / or on an (outer) surface of a heat pump unit outlet pipe for determination of the outlet temperature of the first heat pump unit. This may be seen as an indirect temperature measurement, as the sensor is not in direct contact with the fluid, but in contact with a pipe, in particular an outer surface of the pipe, in which the fluid flows. An advantage is that potential leakage through a pipe is avoided if the sensor crosses the pipe wall. Also, maintenance may be simplified. A copper pipe may support the accuracy of the measurement of the temperature of the fluid, as copper has a high thermal conductivity. A correction of the temperature as measured indirectly, which corrective is reflective of implications of indirect measurement, may optionally be applied. An alternative to the indirect measurement of the temperature of the fluid is a direct measurement of the temperature of the fluid, in particular inside the pipe.

[0081] Optionally, a supplementary temperature sensor is provided in the second heat pump unit for determining an inlet and / or outlet temperature of the fluid in at least one of a heat pump unit inlet pipe and a heat pump unit outlet pipe of the second heat pump unit, respectively, wherein optionally the master control unit is configured to control the first and second heat pump units based on the input and / or output temperature of the second heat pump unit. If a temperature sensor is not only provided in the first heat pump unit, but also in the second heat pump unit, this may be preferable in terms of safety and reliability. If the temperature sensor in the first heat pump unit were broken, determination of the temperature may, for the control of the master control unit, be provided based on the determination of the temperature in the second heat pump unit.

[0082] Optionally, the first and second heat pump units, and / or optionally the master control unit and the slave control unit, are physically connected to each other for communication of the control signals, preferably by way of a signal wire, for instance via a Modbus cable between the heat pump units. The communication between the master control unit and the slave control unit may be wireless or by way of a wire. A wire allows for direct and reliable connection. As heat pump units are often located (relatively) close to one another, a transmission via a wire may often be realized without undue efforts. In particular, the wire may not need to pass through building walls, which may otherwise be the case if the heat pump unit is installed outdoor and the temperature sensor for the common control is in the tank (which is inside the building). The invention also relates to a method of operating a heat pump system, wherein fluid is heated and / or cooled by at least one of first and second heat pump units, wherein at least first and second heat pump units are provided, wherein the at least first and second heat pump units each comprise at least one temperature sensor related to the at least first or second heat pump unit for determining the inlet temperature and / or outlet temperature of the fluid at or in the at least first or second heat pump unit. A master control unit is provided which is configured for common control of the at least first and second heat pump units on the basis of the determined inlet and / or outlet temperature received from the at least one temperature sensor, in particular at or in the at least first or second heat pump unit. The method comprising the steps of:

[0083] - selecting from the at least first and second heat pump unit, by way of the master control unit, a primary heat pump unit for meeting a heat and / or cooling demand; selecting based on the selection of the primary heat pump unit, by way of the master control unit, at least one temperature sensor of the primary heat pump; and and commonly controlling the at least first and second heat pump unit on the basis of the determined inlet and / or outlet temperature of the at least one temperature sensor of the fluid at or in the primary heat pump unit to meet said heat and / or cooling demand .

[0084] In other words, to explain the principle, the master control unit receives a heat and / or cooling demand (also referred to in the application as a heat and / or cooling request). The master control unit selects - in response to said heat and / or cooling demand - the primary heat pump unit from the at least first and second heat pump unit to meet said heat and / or cooling demand. The master control unit further selects the temperature sensor of the primary heat pump for controlling the heat pump system, in particular the at least first and second heat pump units, to meet said heat and / or cooling demand. So, in other words, the master control unit is configured for common control of the at least first and second heat pump unit on the basis of the determined inlet and / or outlet temperature received from the at least one temperature sensor of the fluid at or in the primary heat pump unit selected by the master controller unit to meet said heat and / or cooling demand.

[0085] The method according to the invention allows for a heat pump system setup which does not require a wired or wireless connection of the heat pump units of such a heat pump system with a separate temperature probe for the control of the heat pump system. In addition, a heat pump system applying the method according to the invention allows for a more versatile heat pump system compared to the prior art which allows for addition or replacement of a heat pump unit without the need to plan for such an occurrence prior to initial installation to account for wirecompatibility and / or wireless-compatibility of the heat pump system and the installation site. In addition, the method allows for selecting the heat pump units of the heat pump system in a balanced manner, in particular taking specific parameters into account for each heat and / or cooling demand and thus allowing for an optimization of total cost of ownership, maintenance and repair and replacement costs and overall lifespan optimization of the heat pump units of the system. The method according to the invention further allows to take sustainability goals into account in an easy manner which does not require complex heat pump system designs and installations.

[0086] Optionally, at least in connection with / at the primary heat pump unit, the temperature of the fluid is determined before and / or after the fluid is heated / cooled by at least the primary heat pump unit. The primary heat pump unit can for example be for example the first or the second heat pump unit. The temperature is determined via the at least one temperature sensor related to the primary heat pump unit for determining the inlet temperature and / or outlet temperature of the fluid, in particular at or in the primary heat pump unit, and the master control unit is configured for controlling the operation of the at least first and second heat pump units via the master control unit - either directly or indirectly - and the master control unit is configured to control the operation of the at least first and second heat pump unit based on the determined temperature.

[0087] Optionally, the master control unit sends control signals for the second heat pump unit on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit to a slave control unit. The slave control unit is provided in connection with or related to and / or in the second heat pump unit, and the slave control unit receives said control signals and controls the operation of the second heat pump unit accordingly.

[0088] Optionally, the master control unit controls the operation of the at least first heat pump unit by way of the master control unit either directly or indirectly, in particular directly, on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit. In case the master control unit controls the first heat pump unit indirectly, it controls the first heat pump unit via a slave control unit.

[0089] In other words, the master control unit is commonly controlling the operation of the at least first and second heat pump units either directly or indirectly, wherein the control is based on the determined temperature of the at least one temperature sensor of the primary heat pump unit for the respective heat and / or cooling demand. So, as an example to explain the principle, the master control unit receives a heat and / or cooling demand. The master control unit selects a primary heat pump unit, for example the first heat pump unit, for meeting said heat and / or cooling demand. The master control unit selects at least one temperature sensor of the primary heat pump unit to determine the inlet and / or outlet temperature related to the primary heat pump unit. The master control unit sends control signals / commands to any heat pump unit not selected as the primary heat pump unit, e.g. the at least second heat pump unit, on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit either directly or indirectly by sending the control signal / command to the respective slave control unit. For example, the master control unit sends the control signals / commands to the slave control unit of the second heat pump unit, and the slave control unit receives said control signals and controls the operation of the second heat pump unit accordingly.

[0090] Suitable control signals / commands the master control unit can send to the slave control unit for execution are for example an on / off control signal / command, a standby control signal / command, a monitoring control signal / command, a mode control signal / command, a temperature control signal / command or time control signal / command an activation or initializing control signal / command, and a change control signal / command, such as changing the compressor speed to change the operation of a heat pump unit which is active. This has the advantage that the master control unit servs as the brain of the heat pump system, ensuring that the respective slave operates harmoniously within the heat pump system. This allows for maintaining consistency in the operation of the heat pump system. In addition, the heat pump system can be set up with a straightforward installation using the controls of the heat pump units within a streamlined communication which is directed by the master control unit based on the selection of the respective primary heat pump unit to meet the respective heat and / or cooling demand.

[0091] Optionally, the master control unit selects a secondary heat pump unit to meet the heat and / or cooling demand . The secondary heat pump unit can be the first or the second heat pump unit or a further heat pump unit of the heat pump system. The first heat pump unit can be controlled by the master control unit directly or indirectly, in particular directly. The second heat pump unit and any further heat pump unit can be controlled directly or indirectly, in particular indirectly, by the master control unit via respective slave control units.

[0092] The operation of the secondary heat pump unit can in other words be controlled by the main control unit directly or indirectly via the respective slave control unit. In other words, the master control unit can select more than one of the at least first and second heat pump units to meet the respective heat and / or cooling demand. The master control unit can for example select the secondary heat pump unit to support the primary heat pump unit in meeting the respective heat and / or cooling demand. The secondary heat pump unit can support the first heat pump unit from the start. The secondary heat pump unit can support the first heat pump unit in one or more intervals of the operation of the heat pump system to meet the heat and / or cooling demand.

[0093] So, by way of example, the first heat pump unit can operate alone as the primary heat pump unit to meet the heat and / or cooling demand in a first (time) interval. In a second (time) interval the selected secondary heat pump unit can support the first heat pump unit, this can be e.g. the second heat pump unit. In a third (time) interval a further, thus third heat pump unit could be added or replace the secondary heat pump unit in supporting the primary heat pump unit. The third heat pump unit can for example replace the secondary heat pump unit in case the secondary heat pump unit would need to be defrosted, shows an error code or to further balance the working hours of the heat pump units of the heat pump system. This makes the response of the heat pump system to the respective heat and / or cooling demand even more versatile and efficient and can take parameters of operation into account while controlling meeting the heat and / or cooling demand based on the at least one temperature sensor of the primary heat pump unit. This configuration further streamlines the communication within the heat pump system according to the invention. The multiple heat pump units are managed via the master control unit based on the selection of the primary heat pump which leads to an optimized communication and operation efficiency of the heat pump system. This makes it easy to add or remove a heat pump unit during meeting the heat and / or cooling demand. The setup allows even more efficiently accommodating changes and dynamically assigning and reassigning operational tasks between the heat pump units allowing for an optimized performance of the heat pump system based on the overall control via the temperature sensor of the selected primary heat pump unit.

[0094] The master control unit controls the secondary heat pump unit by way of the temperature sensor of the primary heat pump unit, in particular for control of the operation of the secondary heat pump unit, to meet the heat and / or cooling demand. In other words, the master control unit is configured such that the temperature sensor of the primary heat pump unit is used to control the secondary heat pump unit, in particular the operation of the secondary heat pump unit, to meet the heat and / or cooling demand. The master control unit can control the secondary heat pump unit directly or indirectly via the slave control unit.

[0095] Optionally, the master control unit individually controls the at least first heat pump unit and is optionally located in the first heat pump unit. Hence, the master control unit may not only be responsible for the common control of the plurality of heat pump units, but also for the individual control of the first heat pump unit.

[0096] The method of the invention may relate to the system of the invention. In particular, the method of the invention may be based on the control units of the system of the invention. Vice versa, the control unit(s) of the system of the invention may realize the method of the invention.

[0097] According to an aspect of the invention a data processing device comprising means for carrying out an inventive method is provided. The data processing device can comprise at least one processor or be a processor. The data processing device can be part of a printed circuit board, in particular a printed circuit board assembly. The processor can have an internal memory. Additionally, a computer program product is provided, which, when the program is executed by a computer, in particular a data processing unit, cause the computer, in particular the data processing unit, to carry out the inventive method. Furthermore, a computer readable data carrier having stored thereon the computer program product or data carrier signal carrying the computer program product is provided.

[0098] The invention is described in the following with reference to the drawings, which should, however, not be understood as limiting the invention in any respect.

[0099] Brief description of the drawings

[0100] Figure 1 schematically shows a heat pump system of the invention.

[0101] Figure 2 shows capacity-related diagrams for a first embodiment in figure

[0102] 2(a), and for a second embodiment in figure 2(b).

[0103] Figure 3 schematically shows control and heating constellations for a first embodiment in figure 3(a), and for a second embodiment in figure 3(b).

[0104] Detailed description

[0105] Figure 1 shows a heat pump system 1 for heating and / or cooling fluid in a common fluid circuit. The heat pump system 1 comprises a first heat pump unit 2 and a second heat pump unit 2’. Each of the heat pump units 2, 2’ has a heat pump unit inlet pipe 6, 6’ and a heat pump unit outlet pipe 7, 7’. In the embodiment of figure

[0106] 1 , fluid flows in a tank 3 for heat exchange with a liquid not in fluid communication with the fluid, for example water of a domestic water tank. Fluid enters the tank 3 via the tank supply pipe 4 and exits the tank via the tank return pipe 5. The pump inlet pipe 6, 6’ supplies fluid to the respective heat pump unit 2, 2’ and is connected to the tank return pipe 5. The pump outlet pipe 7, T returns fluid from the respective heat pump unit 2, 2’ to the tank 3 via the tank supply pipe 4. However, in other embodiments, no tank 3 may be present. In embodiments, further devices may be present, such as a hydraulic separator (not shown).

[0107] The heat pump units 2, 2’ and the tank 3 are part of a fluid circuit, in which the heat pump units 2, 2' represent parallel fluid flows. As such, the heat pump units

[0108] 2, 2’ are operational in parallel in that they share a fluid circuit. In other words, the heat pump units 2, 2' are in cascade. However, it is not necessary that all heat pump units 2, 2’ are indeed operating. How operation is actually controlled is explained below.

[0109] The fluid circuit in figure 1 shows further details: Pressure gauges 15, (water) filters 16, check valve / one-way valves 17 and manual valves 18 may be provided. The master control unit 9 is located in the first heat pump unit 2 and serves for joint control of both the first and second heat pump units 2, 2’ and also for individual control of the first heat pump unit 2. Fluid in the tank 3 is in heat-exchange with consumption liquid (separately from the fluid) accommodated in the tank 3. The liquid is used in a circuit 12 which is connected to the tank 3 via a consumption circuit supply pipe 13 and a consumption circuit return pipe 14. Consumption may relate to consumption of the energy delivered by the consumption liquid (heat or cold) e.g. by emitters, and / or to the consumption of the domestic liquid.

[0110] According to the invention, a temperature sensor 8a, 8b is provided in the first heat pump unit 2. This temperature sensor 8a, 8b determines the inlet temperature or outlet temperature of the fluid. In figure 1 , a temperature sensor 8a for detecting the outlet temperature of the fluid is located at the heat pump outlet pipe 7 inside the heat pu mp unit 2 and a temperature sensor 8b for detecting an inlet temperature of the fluid is located at the heat pump inlet pipe 6 inside the heat pump unit 2. In the embodiment of figure 1 , corresponding temperature sensors 8a’, 8b’ are provided in the second heat pump unit 2’. These sensors 8a’, 8b’ are supplementary for the invention and may be provided for safety purposes, just in case the temperature sensors 8a, 8b are out of function.

[0111] A master control unit 9 is comprised in the first heat pump unit 2, and controls not only the first heat pump unit 2, but also the second heat pump unit 2’, based on the determination of the temperature by the temperature sensor(s) 8a, 8b in the first heat pump unit 2. The first heat pump unit 2 is thus selected by the master control unit 9 as the primary heat pump unit to meet a specific heat and / or cooling demand. The master control unit 9 communicates with the second heat pump unit 2’ in that it sends control signals / commands to the slave control unit 9’ of the second heat pump unit 2’. Such control signals / commands relate to the operation of the second heat pump unit 2’. The slave control unit 9’ receives the signals from the master control unit 9 and controls the operation of the second heat pump unit 2’ accordingly. The master control unit 9 and the slave control unit 9’ are in communication with each other and exchange signals. As shown in figure 1 , a wire 11 physically connects the master control unit 9 and the slave control unit 9’. As the first heat pump unit 2 and the second heat pump unit 2’ may be located relatively close to each other and, e.g. on the same side of a building, a relatively short wire 11 may be sufficient.

[0112] In figure 1 , it is indicated that the temperature sensors 8a, 8b, 8a’, 8b’ are located on the respective heat pump inlet pipe or heat pump outlet pipe for indirect measurement of the temperature of the fluid.

[0113] Turning to figure 2, the first and second heat pump units 2, 2’ each have a heat pump capacity, wherein the master control unit 9 controls the heat pump capacity of each of the first and second heat pump units 2, 2'. The control is based on the determined input and / or output temperature and considers various factors such as the total running time, the remaining lifetime, the heat pump capacity, the noise level, icing and de-icing requirements. On this basis, the capacity at which the plurality of pump units runs is chosen. This is possible if the plurality of heat pump units comprises inverters for modifying the capacity of the compressor. More specifically, the speed of the compressor can be adjusted for each heat pump unit 2, 2’. In the example of figure 2(a), first and second heat pump units operate in cascade. The total request - in other words heat and / or cooling demand - increases with time, wherein initially, during interval a, only the first heat pump unit 2 operates and is thus selected as the primary heat pump unit. During interval b, the second heat pump unit 2’ supports the first heat pump unit 2 to meet the heating and / or cooling target, the second heat pump unit 2’ is thus selected as the secondary heat pump unit. More specifically, in interval b, the capacity of the first heat pump unit 2 is continuously reduced while the capacity of the second heat pump unit 2’ is continuously increased. During interval c, the first and second heat pump units 2, 2’ run with continuously increasing capacities in order to meet the increasing total request, in other words heat and / or cooling demand. As is evident from figure 2(a), when the capacity of the first heat pump unit 2 reaches 50% of the maximum capacity at the end of interval a, the second heat pump unit 2’ starts operating so as to reduce the workload of the first heat pump unit 2. Thus, instead of having the first heat pump unit 2 working at a high rate of frequency which is not optimal regarding reliability and performance of the heat pump unit 2, both first and second heat pump units 2, 2' are working in a preferred and more efficient frequency rate range. The master control unit 9 controls both the first and second heat pump units 2, 2’, thus the primary and the secondary heat pump units to meet the heat and / or cooling demand on the basis of the temperature sensors 8a, 8b in the first heat pump unit 2 as the primary heat pump. The master control unit 9 can use the temperature of the temperature sensor 8a, and / or of the temperature sensor 8b.

[0114] In figure 2(b), three heat pump units 2, 2’, 2” are part of the heat pump system and in cascade, wherein the third heat pump unit 2” is provided in addition to first 2 and second 2’ heat pump units. During interval a, the first heat pump unit 2 can meet the total request in other words heat and / or cooling demand alone. The first heat pump unit 2 is thus chosen as the primary heat pump to meet said heat and / or cooling demand . In interval b, the second heat pump unit 2’ becomes active while the first heat pump 2 is also active. The second heat pump unit 2’ is thus selected as the secondary heat pump unit by the master control unit 9. The master control unit 9 controls the operation of the secondary heat pump unit, thus the second heat pump unit 2’, on the basis of the temperature received from the temperature sensors 8a, 8b of the primary heat pump unit for said heat and / or cooling demand. The master control unit 9 can use the temperature of the temperature sensor 8a, and / or of the temperature sensor 8b. In interval c, all three heat pump units are working, wherein the capacity of the third heat pump unit 2” continuously increases and the capacities of the first and second heat pump units 2, 2’ decreases. The third heat pump unit 2” is also controlled by the master control unit 9 on the basis of the temperature sensor 8a, 8b of the primary heat pump unit to meet said heat and / or cooling demand. The master control unit 9 can use the temperature of the temperature sensor 8a, and / or of the temperature sensor 8b. The operation of the second heat pump unit 2’ and of third heat pump unit 2” is controlled via the respective slave control unit 9’ which receives the control signals from the master control unit 9. At the end, in interval d, all three heat pump units are in operation, with continuously and equally increasing capacities. Thanks to associated management of the heat pump units 2, 2’, the more optimal frequency range of the compressor of each unit may be preferred.

[0115] Figure 3 is directed to various constellations with a master control unit 9 and a slave control unit 9’ of the present invention. Figure 3(a) shows two different situations. In situation (1 ), the target temperature is 60°C. The temperature of the fluid in the tank 3 is 50°C, which is seen as corresponding to the pump inlet temperature at the first and second heat pump units 2, 2’. Here, the second heat pump unit 2’ is not working, as the request of power of 20 kW can be met by the first heat pump unit 2 alone, see the outlet temperature of the first heat pump unit 2 of 55°C. Thus, the first heat pump unit 2 is selected by the master control unit 9 as the primary heat pump unit for meeting the heat and / or cooling demand. The master control unit 9 sends control signals to the slave control unit 9’ of the second heat pump unit 2’ to not respond to the heat and / or cooling demand. Thus, the master control unit 9 sends for example the control signals / command to the slave control unite 9’ of the second heat pump unit 2’ to deactivate the heating mode or to switch or remain in a standby mode or to remain in a monitoring status and await further instructions from the master control unit 9. In situation (2), the target temperature is also 60°C and the inlet temperature is 50°C. Here, the first heat pump unit 2 is not operating, but the second heat pump unit 2’ is operating. The master control unit 9 may decide whether situation (1 ) or (2) is to be realized depending on the remaining lifetime of the first and second heat pump units, for example. Thus, the master control unit 9 selects the primary heat pump unit from the first and second heat pump units 2, 2’ , or any further heat pump unit, based on the remaining lifetime, or working hours and / or further parameters such as the capacity of the selected primary heat pump unit and / or the heat load distribution and / or a zone parameter and / or the COP of the first heat pump unit 2 and / or of the second heat pump 2’, and sends corresponding control signals to control the first and second heat pump units 2, 2’. In other words, the master control unit 9 considers values relating to a set of predefined parameters of the at least first and second heat pump units 2, 2’. The master control unit 9 selects the primary heat pump unit based on the set of predefined parameters.

[0116] Figure 3(b) shows two further constellations, which are close to those of figure 3(a), but in which the power request is higher, namely 40 kW, for the same target temperature of 60°C. In situation (1 ), the master control unit 9 has decided to let both first and second heat pump units 2, 2’ operate. It is indicated in figure 2(b)(1 ) that the outlet temperature of the first and second heat pump units is 55°C each. The master control unit 9 selects either the first or the second heat pump unit 2, 2’ to be the primary heat pump unit to meet the heat and / or cooling demand and the other heat pump unit to be the secondary heat pump unit and will select the temperature sensor 8a, 8b of the primary heat pump to control both the primary and the secondary heat pump units. Situation (2) reflects that the first heat pump unit 2 is defrosting and is, therefore, not available for heating. The master control unit 9 is about to initiate operation of the second heat pump unit 2’ so as to meet the heat demand - in other words heating request. The second heat pump unit 2’ is therefore selected by the master control unit 9 as the primary heat pump unit to meet the heat and / or cooling demand. As long as defrosting of the first heat pump unit 2 is ongoing, only the second heat pump unit 2’ will be available for heating. By doing so, the second heat pump unit 2’ is able to at least partially compensate for the temperature loss during defrosting of the first heat pump unit 2. Reference signs

[0117] 1 heat pump system

[0118] 2, 2’, 2” heat pump unit

[0119] 3 tank

[0120] 4 tank supply pipe

[0121] 5 tank return pipe

[0122] 6, 6’ heat pump unit inlet pipe

[0123] 7, T heat pump unit outlet pipe

[0124] 8a, 8a’ (outlet) temperature sensor

[0125] 8b, 8b’ (inlet) temperature sensor

[0126] 9, 9’ control unit

[0127] 10, 10’ compressor

[0128] 1 1 signal wire

[0129] 12 consumption circuit

[0130] 13 consumption circuit supply pipe

[0131] 14 consumption circuit return pipe

[0132] 15 pressure gauge

[0133] 16 filter

[0134] 17 check valve / one-way valve

[0135] 18 manual valve

Claims

Claims1. Heat pump system (1) for heating and / or cooling fluid, the system comprising: at least first and second heat pump units (2, 2') each configured for heating and / or cooling fluid, at least one temperature sensor (8a, 8b) related to each of the at least first and second heat pump unit (2, 2’) for determining the inlet temperature and / or outlet temperature of the fluid at or in the at least first or second heat pump unit (2, 2’), and a master control unit (9) for common control of the at least first and second heat pump units (2, 2 ) on the basis of the determined inlet and / or outlet temperature of the at least one temperature sensor (8a, 8b), wherein the master control unit (9) is configured such that the master control unit (9) selects a primary heat pump unit from the at least first or second heat pump unit to meet a heat and / or cooling demand and wherein the master control unit (9) is configured such that it selects the at least one temperature sensor (8a, 8b) of the primary heat pump unit for determining the inlet and / or outlet temperature of the fluid at or in the primary heat pump unit to meet said heat and / or cooling demand.

2. Heat pump system of claim 1 , further comprising a slave control unit (9’) of the second heat pump unit (2’) for control of the operation of the second heat pump unit (2’), and wherein the master control unit (9) and the slave control unit (9’) are configured such that the master control unit (9) sends control signals for the second heat pump unit (2’) on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit to the slave control unit (9’), and the slave control unit (9’) receives said control signals and controls operation of the second heat pump unit (2’) accordingly.

3. Heat pump system of claim 1 or 2, wherein the master control unit (9) and the slave control unit (9’) are configured to communicate with each other.

4. Heat pump system of any of the preceding claims, wherein the heat pump system comprises at least a further heat pump unit (2”).

5. Heat pump system of any of the preceding claims, wherein the primary heat pump unit is selected based on a set of predefined parameters, in particular the number of working hours of the selected primary heat pump unit and / or the capacity of the primary heat pump unit and / or heat load distribution and / or a zone parameter and / or the COP of the selected primary heat pump unit.

6. Heat pump system of any of the preceding claims, wherein the master control unit (9) is configured such that the master control unit (9) selects asecondary heat pump unit to meet the heat and / or cooling demand, in particular based on a set of predefined parameters and wherein the master control unit (9) is configured such that the temperature sensor (8a, 8b) of the primary heat pump unit is used for controlling the secondary heat pump unit in case the master control unit (9) selects the secondary heat pump unit to meet the heat and / or cooling demand.

7. Heat pump system of any of the preceding claims, wherein the master control unit (9) is further configured for individual control of the first heat pump unit (2) and is optionally located in the first heat pump unit (2).

8. Heat pump system of any of the preceding claims, wherein the system further comprises a tank (3), preferably a water tank, wherein the tank has at least a tank supply pipe (4) for supply with fluid from the first and / or second heat pump units (2, 2’), and a tank return pipe (5) for return of fluid to the first and / or second heat pump units (2, 2’).

9. Heat pump system of any of the preceding claims, wherein the at least first and second heat pump units (2, 2’) are configured to operate in cascade.

10. Heat pump system of any of the preceding claims, wherein the master control unit (9) is configured such that the master control unit (9) can communicate with the at least first and second heat pump units (2, 2’) via a local connection, bus, or network, in particular using a bus communication protocol in particular the OpenTherm protocol, or the Modbus protocol, or the EEBus protocol, or the CAN protocol, including the CANopen protocol or the DeviceNet protocol, or the BACNet protocol.11 . Heat pump system of any of the preceding claims, wherein the first and second heat pump units (2, 2’) each have a heat pump capacity, wherein the master control unit (9) is configured to control the heat pump capacity of each of the first and second heat pumps (2, 2’) based on the determined input and / or output temperature.

12. Heat pump system of any of the preceding claims, wherein at least one of the first and second heat pump units (2,2’) comprises a compressor (10, 10’) for compressing refrigerant and an inverter for modifying the capacity, in particular, the speed of the compressor, wherein said at least one heat pump unit (2, 2’) is configured such that the speed of the compressor (10, 10’) is adjustable.

13. Heat pump system of claim 12, wherein the master control unit (9) is configured to control the compressor speed of each of the first and second heat pump units (2, 2’) based on the determined input and / or output temperature, optionally such that it is prioritized that the speed of the compressor (10, 10’) of each of the first and second heat pump units (2,2’) does not exceed 90%, preferably not exceed 85% of the maximum speed of the respective compressor (10, 10’), and is more preferably between 40 and 85% of the maximum speed of the respective compressor (10, 10’) as far as possible in view of the target cooling / heating requirement to be met.

14. Heat pump system of any of the preceding claims, wherein the master control unit (9) is configured to base the selection of the primary heat pump unitand / or the at least secondary heat pump unit and / or control on at least one of: the total running time, the remaining lifetime, the heat pump capacity, the noise level, status as to error or warning, and icing and de-icing requirements of the first and / or second heat pump units (2, 2’).

15. Heat pump system of any of the preceding claims, wherein the master control unit (9) is configured to control the at least first and second heat pump units (2, 2’) such that, if the at least first and second heat pump units (2, 2’) are each available to produce a heating requirement, in particular at 40 to 85% of its maximum speed, the heat pump unit (2, 2’) with the lower total running time amongst the first and second heat pump units (2, 2’) is chosen as the primary heat pump unit producing the heat and / or cooling demand16. Heat pump system of any of the preceding claims, wherein the temperature sensor (8a, 8b) is located on an outer surface of a heat pump inlet pipe (6) for determination of the inlet temperature of the first heat pump unit (2) and / or on an outer surface of a heat pump outlet pipe (7) for determination of the outlet temperature of the first heat pump unit (2).

17. Heat pump system of any of the preceding claims, wherein a supplementary temperature sensor (8a’, 8b’) is provided in the second heat pump unit (2’) for determining an inlet and / or outlet temperature of the fluid in at least one of a heat pump unit inlet pipe (6’) and a heat pump outlet pipe (7’) of the second heat pump unit (2’), respectively, wherein optionally the master control unit (9) is configured to control the first and second heat pump units (2, 2’) based on the input and / or output temperature of the second heat pump unit (2’).

18. Heat pump system of any of the preceding claims, wherein the first and second heat pump units (2, 2’), and / or the master control unit (9) and the slave control unit (9') are physically connected to each other for communication of the control signals, preferably by way of a signal wire (11).

19. Method of operating a heat pump system, optionally the heat pump system of any of the preceding claims, comprising heating and / or cooling fluid by at least one of first and second heat pump units (2, 2’), wherein the at least first and second heat pump units (2, 2’) are provided, wherein the at least first and second heat pump units each comprise at least one temperature sensor (8a, 8b) related to the at least first or second heat pump unit (2, 2’) for determining the inlet temperature and / or outlet temperature of the fluid at or in the at least first or second heat pump unit (2, 2’); a master control unit (9) is provided which is configured for common control of the at least first and second heat pump units on the basis of the determined inlet and / or outlet temperature received from the at least one temperature sensor, the method comprising the steps of: selecting from the at least first and second heat pump unit (2, 2’) by way of the master control unit (9) a primary heat pump unit for meeting a heat and / or cooling demand;selecting based on the selection of the primary heat pump unit, by way of the master control unit (9), at least one temperature sensor (8a, 8b) of the primary heat pump unit; and commonly controlling the at least first and second heat pump unit (2, 2’) on the basis of the determined inlet and / or outlet temperature received from the at least one temperature sensor (8a, 8b) of the fluid at or in the primary heat pump unit to meet said heat and / or cooling demand.

20. Method according to claim 19, further comprising the step of: determining at least in connection with the first heat pump unit (2) the temperature of the fluid before or after the fluid is heated or cooled by the primary heat pump unit via the at least one temperature sensor (8a, 8b) related to the primary heat pump unit for determining the inlet temperature and / or outlet temperature of the fluid, and commonly controlling operation of the first and second heat pumps units (2, 2’) by way of the master control unit (9) based on the determined temperature.

21. Method according to claim 19 or 20, wherein the master control unit (9) sends control signals for the second heat pump unit (2’) on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit to a slave control unit (9’) of the second heat pump unit (2’), and the slave control unit (9’) receives said control signals and controls the operation of the second heat pump unit (2’) accordingly22. Method according to any of claims 19 to 21 , comprising controlling the operation of the at least first heat pump unit (2) by way of the master control unit (9) on the basis of the determined inlet and / or outlet temperature of the primary heat pump unit.

23. Method of any of claims 19 to 22, wherein the master control unit (9) selects at least a secondary heat pump unit to meet the heat and / or cooling demand and wherein the master control unit (9) controls the secondary heat pump unit by ay of the temperature sensor of the primary heat pump unit, in particular for control of the operation of the secondary heat pump unit, to meet the heat and / or cooling demand.

24. Method of any of claims 19 to 23, wherein the master control unit (9) individually controls the first heat pump unit (2), and is optionally located in the first heat pump unit (2).

25. Data processing device (9) comprising means for carrying out the method of at least one of the claims 19 to 24.

26. A computer program product comprising instructions to cause the heat pump system of any one of claims 1 to 18 to execute the steps of the method of any of the preceding claims 19 to 24.

27. A computer readable data carrier having stored thereon the computer program product according to claim 26.

28. A data carrier signal carrying the computer program product according to claim 26.

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