Adapting an operation of a pump of a hot water system

Abstract

The invention relates to a method (10) for adapting an operation of a pump (40) of a hot water system (20). The method comprises the steps of: directly or indirectly obtaining (11) a temperature of a fluid in the hot water system; starting (12) the pump (40) with a given pump setting when the temperature reaches a lower threshold value while the pump (40) is stopped, or when the pump (40) is stopped for a predetermined off-time; and stopping (13) the pump (40) again if at least one of a number of stop criteria is detected, wherein the number of stop criteria comprises the following criteria: a) the temperature reaches an upper threshold value, and b) a predetermined amount of time has lapsed since the start of the pump (40). The method (10) further comprises: adapting (14) the pump setting for a subsequent start of the pump (40) based on the detected stop criteria.

Description

[0001]Grundfos Holding A / S Adapting an operation of a pump of a hot water system TECHNICAL FIELD OF THE INVENTION 5 The invention relates to a method for adapting an operation of a pump of a hot water system. The invention further relates to a pump for use in a hot water system. BACKGROUND OF THE INVENTION 10 A domestic hot water system delivers hot water via pipes to various fixtures in a building, such as sinks, showers or other appliances. If no hot water is withdrawn from the system for a longer amount of time, the water in the pipes cools down. If 15 there is an extensive piping, it may take a relatively long amount of time to replace this cooled down water with hot water from a hot water supply (e.g., a boiler), which can cause long waiting times at a tap. 20 Circulation pumps can be used to generate a flow inside the pipes of the system and to circulate the water back to a heat source (e.g., the boiler), even if no hot water is withdrawn. This ensures that the water in the pipes is always relatively hot and the waiting time for hot water is reduced. 25 The operating conditions (e.g., runtimes) of the circulation pump should be selected to minimize the flow rate of the water, while at the same time maintaining the comfort of having hot water available at the tap at all times. In simple terms, 30 increasing the runtime enhanced the comfort, while decreasing the runtime enhances efficiency. Grundfos Holding A / S In addition, it should be considered that high flow rates can increase the tear on the system and cause acoustic noise throughout the system. In contrast, low flow rates can result in discomfort, as it might not activate all heaters or transport 5 the hot water fast enough through the system. Most conventional recirculation systems are operated based on fixed conditions, such as fixed runtime settings. However, these fixed conditions can diverge from the optimum operating points 10 for a certain hot water system causing some of the above mentioned disadvantages. Thus, it is an objective to provide an improved pump for a domestic hot water system and an improved method for adapting 15 an operation of such a pump which avoid the above mentioned disadvantages. SUMMARY OF THE INVENTION 20 The object of the present invention is achieved by the solution provided in the enclosed independent claims. Advantageous implementations of the present invention are further defined in the dependent claims. 25 According to a first aspect, the invention relates to a method for adapting an operation of a pump of a hot water system. The method comprises the steps of: measuring a temperature value which represents a temperature of the fluid that is pumped through the hot water system; starting the pump with a given 30 pump setting when the temperature value reaches a lower threshold value while the pump is stopped, or when the pump is stopped for a predetermined off-time; and stopping the pump Grundfos Holding A / S again if at least one of a number of stop criteria is detected, wherein the number of stop criteria comprises at least one of the following criteria: a) the temperature value reaches an upper threshold value, and b) a predetermined amount of time has 5 lapsed since the start of the pump. The method further comprises: adapting the pump setting for a subsequent start of the pump based on the detected stop criteria. This achieves the advantage that the pump can be dynamically 10 adjusted to the requirements of the hot water system. For instance, the efficiency of the system can be increased in this way. The number of stop criteria can comprise both of the stop 15 criteria a and b. For example, if the pump is stopped due to the temperature value reaching the upper threshold value, this indicates that the flow rate generated by the pump is too high. In contrast, if the pump 20 is stopped due to the determined amount of time having passed since the start of the pump, this can indicate that the flow rate generated by the pump is too low. The pump can then adjust the pump setting accordingly for its subsequent run(s). 25 Preferably, the pump is configured to operate in a cyclical manner to periodically pump the fluid through the system or more specifically through a hot water recirculation line of the system. 30 In particular, the pump operating in a cyclical manner means that the pump runs periodically or more specifically that it periodically starts and stops to run. In other words, its pump Grundfos Holding A / S drive is periodically turned on an off. Thereby, the turning on and off of the pump drive can define a pump cycle. The “subsequent start of the pump” thus refers to the start of the pump in a subsequent pump cycle. 5 In particular, adapting the pump setting for the subsequent run means that during the subsequent run, the pump operates with the adapted pump setting (e.g., with an adapted flow set point). 10 For example, the at least one of the number of stop criteria is detected while the pump is running. In particular, the fluid is water or more specifically hot water. 15 The hot water system can be a domestic hot water system. The hot water system can comprise a hot water recirculation line, wherein the pump is connected to the hot water recirculation line and is configured to pump the fluid through the hot water recirculation line when started. 20 The predetermined amount of time can be a maximum on-time of the pump during a pump cycle. This can provide a fallback for stopping the pump in case the upper threshold value cannot be reached. 25 In an embodiment, the number of stop criteria further comprises the following criteria: c) the temperature value has increased by a predetermined amount since the start of the pump. 30 For instance, the number of stop criteria can comprise all three criteria a, b and c. Alternatively, the number of stop criteria could comprise only stop criteria b and c. Grundfos Holding A / S In an embodiment, the pump setting is adapted for the subsequent start of the pump based on which of the number of stop criteria is detected first. This achieves the advantage that the pump can 5 be dynamically adjusted to the requirements of the hot water system. In particular, this is relevant, if the number of stop criteria comprises more than one stop criteria (e.g., stop criteria a and b, or stop criteria b and c, or stop criteria a and b and c). 10 In an embedment, the pump setting is a flow set point of the pump. For instance, the flow set point determines a flow rate through the pump and / or the system when the pump is running. The flow set point can be correlated to a pump speed. Thus, adapting 15 the flow set point can result in an adaption of the pump speed. For example, an internal control unit of the pump can regulate the pump speed in relation to flow set point and / or an estimated flow rate. 20 In an embodiment, the adaption of the pump setting comprises an increase of the flow set point for the subsequent start of the pump if the detected stop criteria is the lapsing of the determined amount of time. This achieves the advantage that the 25 pump can increase the (recirculation) flow rate if it is too low to achieve a certain temperature increase. This can enhance the comfort of the system (i.e., the availability of hot water). During this reduction of the flow set point, any further adaption 30 of the flow set point can be blocked. In an embodiment, the adaption of the pump setting comprises a Grundfos Holding A / S reduction of the flow set point for the subsequent start of the pump if the detected stop criteria is the reaching of the upper threshold value. This achieves the advantage that the pump can decrease the flow rate if it is too high. This can enhance the 5 efficiency of the system. In an embodiment, the adaption of the pump setting comprises a reduction of the flow set point for the subsequent start of the pump if the detected stop criteria is the increase of the 10 temperature value by the predetermined amount. This achieves the advantage that the pump can decrease the flow rate if it is too high. This can enhance the efficiency of the system. In an embodiment, the flow set point is reduced by a 15 predetermined reduction rate if the detected stop criteria is the reaching of the upper threshold value or the increase of the temperature by the predetermined amount, and if a previous adaption of the flow set point was an increase of the flow set point. 20 For instance, if the temperature stop conditions are met (i.e., stop criteria a or c) the pump decreases the flow rate by a certain amount (e.g., 0.1 GPM). This can be limited by a predefined reduction rate after a (first) increase has occurred. 25 For example, without any previous flow rate increase, the flow rate would decrease with 0.1 GPM at a temperature stop (criteria a or c). But if an increase has occurred, the decrease flow rate would be limited by the predefined reduction rate. In an example, 30 the algorithm would try to decrease by 0.1 GPM but is limited by the reduction rate. The reduction rate is designed such that it requires x hours (e.g., 4 hours) to forget / decrease from the Grundfos Holding A / S increased flow rate (e.g., 0.2 GPM). In an embodiment, the given pump setting is maintained for the subsequent start of the pump if the detected stop criteria is 5 the lapsing of the determined amount of time and the temperature is within a lower and an upper temperature threshold. This achieves the advantage that the pump setting (e.g., flow set point) can be maintained at ideal flow conditions. 10 The upper and / or the lower temperature threshold can be identical to the upper and / or the lower threshold value, respectively. However, the upper and / or the lower temperature threshold can 15 also be a fraction of the upper and lower threshold value, respectively. For example, the upper and the lower temperature thresholds can be within a temperature range between the upper threshold value and the lower threshold value. 20 For example, the upper temperature threshold is identical to the upper threshold value and the lower temperature threshold is in- between the upper and the lower threshold values (e.g., roughly in the middle between these threshold values), or vice versa. 25 There can be further temperature thresholds defined, wherein the flow adaption can depend on whether the temperature at stop criteria b is above or below the further temperature thresholds. For example, the maximum runtime (5 minutes) has been reached 30 while the temperature is above the lower threshold and below the upper threshold; therefore the current flow rate set point can be maintained. Grundfos Holding A / S In an embodiment, the temperature of the fluid is estimated based on a temperature of a pump component which relates to the temperature of the fluid, or the temperature of the fluid is 5 measured in a fluid carrying element of the pump or in a hot water recirculation line of the hot water system. For example, the temperature value is measured continuously while the pump is running and while the pump is stopped. 10 In an embodiment, the method is carried out continuously during a regular operation of the pump. According to a second aspect, the invention relates to a pump, 15 in particular a circulation pump, for a hot water system. The pump comprises: a measurement unit configured to directly or indirectly obtain a temperature of a fluid in the system; and a control unit configured to start the pump with a given pump setting when the temperature reaches a lower threshold value 20 while the pump is stopped, or when the pump is stopped for a predetermined off-time; wherein the control unit is configured to stop the pump again if at least one of a number of stop criteria is detected by the control unit, wherein the number of stop criteria comprises at least one of the following criteria: 25 a) the temperature reaches an upper threshold value, and b) a predetermined amount of time has lapsed since the start of the pump. The control unit is further configured to adapt the pump setting for a subsequent start of the pump based on the detected stop criteria. 30 This achieves the advantage that the pump can be dynamically adjusted to the requirements of the hot water system. For Grundfos Holding A / S instance, the efficiency of the system can be increased in this way. The pump can be configured to operate in a cyclical manner to 5 periodically pump the fluid through the system. In an embodiment, the pump setting is a flow set point of the pump. 10 The pump can comprises a drive, wherein the pump setting can control a speed of the drive. The pump speed can be directly correlated to the flow set point and thus the pump flow rate. The drive can be an electrical drive. 15 In particular, the pump setting determines a flow rate while the pump is running. In an embodiment, the pump further comprises a flow sensor and / or a flow estimator configured to detect a flow rate of the fluid. 20 The flow estimator can be configured to estimate the flow based on a model of the pump which considers a number of operating parameters of the pump to estimate the flow (e.g., power, speed, etc.). The flow sensor can be a sensor which is configured to 25 directly sense the flow. In an embodiment, the number of stop criteria further comprises the following criteria: c) the temperature has increased by a predetermined amount since the start of the pump. 30 In an embodiment, the control unit is configured adapted the pump setting for the subsequent start of the pump based on which Grundfos Holding A / S of the number of stop criteria is detected first. In an embodiment, the adaption of the pump setting comprises an increase of the flow set point for the subsequent start of the 5 pump if the detected stop criteria is the lapsing of the determined amount of time. In an embodiment, the adaption of the pump setting comprises a reduction of the flow set point for the subsequent start of the 10 pump if the detected stop criteria is the reaching of the upper threshold value. In an embodiment, the adaption of the pump setting comprises a reduction of the flow set point for the subsequent start of the 15 pump if the detected stop criteria is the increase of the temperature value by the predetermined amount. In an embodiment, the flow set point is reduced by a predetermined reduction rate if the detected stop criteria is 20 the reaching of the upper threshold value or the increase of the temperature by the predetermined amount, and if a previous adaption of the flow set point was an increase of the flow set point. 25 In an embodiment, the control unit is configured to maintain the given pump setting for the subsequent start of the pump if the detected stop criteria is the lapsing of the determined amount of time and the temperature is within a lower and an upper temperature threshold. 30 In an embodiment, the measurement unit is configured to estimate the temperature based on a temperature of a pump component which Grundfos Holding A / S relates to the temperature of the fluid; or the measurement unit is configured to measure the temperature in a fluid carrying element of the pump or in a hot water recirculation line of the hot water system. 5 For example, in the first case (temperature estimation), the measurement unit can calculate the temperature of the fluid from the temperature of the component based on a known relation; and in the second case, the measurement unit can comprise a 10 temperature sensor to directly measure the temperature of the fluid. According to a third aspect, the invention relates to a hot water system which comprises the pump according to the first 15 aspect of the invention, a hot water recirculation line which is connected to the pump. The hot water system can be a domestic hot water system For instance, the hot water system is a residential or a commercial 20 domestic hot water system. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in the following together with 25 the figures. Fig. 1 shows a flow chart of a method for adapting an operation of a pump of a hot water system according to an embodiment; 30 Figs. 2A-2C show temperature profiles in a hot water system according to an embodiment; Grundfos Holding A / S Fig. 3 show temperature profiles in a hot water system according to an embodiment; 5 Fig. 4 shows different operating conditions over time in a simulated hot water system according to an embodiment; Fig. 5 shows a temperature profile in a hot water system 10 according to an embodiment Fig. 6 shows a schematic diagram of a hot water system according to an embodiment; and 15 Fig. 7 shows a schematic diagram of a pump for a hot water system according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 20 Fig. 1 shows a flow chart of a method 10 for adapting an operation of a pump of a hot water system according to an embodiment. The pump can be configured to operate in a cyclical manner to periodically pump a fluid through the system. The hot water system can be a domestic hot water system. 25 The method 10 comprises the steps of: directly or indirectly obtaining 11 a temperature of a fluid in the hot water system; starting 12 the pump with a given pump setting when the temperature reaches a lower threshold value while the pump is30 stopped, or when the pump is stopped for a predetermined off- time; stopping 13 the pump again if at least one of a number of stop criteria is detected, wherein the number of stop criteria Grundfos Holding A / S comprises at least one of the following criteria: a) the temperature reaches an upper threshold value, and b) a predetermined amount of time has lapsed since the start of the pump. The method 10 further comprises the step of: adapting 14 5 the pump setting for a subsequent start of the pump based on the detected stop criteria. The pump can be a circulation pump or a recirculation pump. The pump can also be a water transfer pump. The pump can be connected 10 to a hot water recirculation line and can be configured to pump the fluid through the hot water recirculation line a periodic manner. The pump setting can be a flow set point of the pump. The flow 15 set point can determine a flow rate of the fluid (e.g., water). Hereby, the flow rate can refer to the volume of fluid that is moving through the pump or through (at least a part of) the hot water system (e.g., the water recirculation line) in a given time period. The flow rate can be a recirculation flow rate of 20 the system. The flow set point can be correlated to the pump speed (i.e., the speed of a pump drive). For instance, adjusting the flow set point can result in an adjustment of the pump speed. 25 The number of stop criteria can further comprise the following criteria: c) the temperature has increased by a determined amount since the start of the pump. 30 For instance, the pump starts with a given flow set point and stops due to one of the stop criteria a-c. This flow set point is then adapted (e.g., increased or decreased) for a subsequent Grundfos Holding A / S start of the pump based on the stop criteria which caused the pump to stop. In particular, the pump setting is adapted 14 based on which of 5 the number of stop criteria, e.g. which of criteria a-c, is detected first. For example, if the pump is stopped due to the temperature reaching the upper threshold value or due to the temperature 10 increasing by the predetermined amount first, this indicates that the flow rate generated by the pump is too high. In contrast, if the pump is stopped due to the predetermined amount of time having lapsed since the start of the pump, this can indicate that the flow rate generated by the pump is too low. 15 The pump can then adjust the pump setting, e.g. the flow set point, accordingly for its subsequent run(s). For example, the method 10 comprises the further step of: starting to run the pump again with the adapted pump setting 20 when the temperature reaches the lower threshold value, or when the pump was stopped for the predetermined off-time. In this way, the pump setting can be adapted 14 from cycle-to- cycle to an optimal flow set point. 25 For instance, a temperature of the fluid can be (indirectly) estimated from a temperature of a pump component and at least one further pump parameter (e.g., a power of the pump). In this example, the temperature of the pump component can be measured. 30 Alternatively, the temperature of the fluid can be directly measured in a fluid carrying element of the pump or in a hot Grundfos Holding A / S water recirculation line of the hot water system, e.g. by a temperature sensor. In particular, the fluid is water or hot water. 5 For example, the temperature is obtained 11 continuously while the pump is running and while the pump is stopped. The temperature can be obtained in discrete time steps. 10 In general, the method 10 aims to achieve optimal flow conditions for a hot water recirculation system by dynamically adjusting the flow set point of the pump to a value which is high enough to maintain availability of hot water at the tap(s) of the system, while being low enough to achieve high efficiency and 15 avoid unnecessary flows. To achieve this goal, the method 10 can utilize information of time measurements (e.g., off-time and determined time since start of pump) and temperature measurements (e.g., lower 20 threshold and upper threshold). The method 10 can be carried out continuously during a regular operation of the pump. In this way, the operation of the pump can be continuously adjusted to optimize the flow based on the individual requirements and constraints of the hot water system. 25 For example, in a domestic hot water system with a tankless heater, the recirculation flow should be high enough for the heater to deliver its minimum heat output without overheating. This can be determined by the temperature difference between the 30 inlet and outlet, as well as the system flow rate, as shown in the following formula: Grundfos Holding A / S ^^^^^ ^^^^^^^^ ^^ ^^^^^^ =^^^^^^^^^^^^ ^^^^^^ ^^^ ( ) [ ]^^ ^^^^^^^^ ^^^^^^^^^^^^(^^)[ 500 ⋅ ∆^^ [℉]ℎ ] ^^^^^^^^^^^^^^ ^^^^^^^^ ^^^^^^^^^^^^(^^ [ ^^^^^^ ] →)ℎ 500 ⋅ (^^^௨^ [℉] − ^^^^௧ [℉])The method 10 can solve this issue by dynamically adjusting the water flow rate Q. In addition or alternatively, it is also possible to reduce the minimum heat output H or to increase the temperature difference ∆T by increasing the supply set point Tsup or decreasing the return temperature Tret. However, these approaches are less desirable as they could lead to reduced comfort or reduced efficiency. Furthermore, the method 10 has the advantage of not requiring the pump to have access to internal heat source calculations of a heat source in the hot-water recirculation system. Thus, with the method 10 the flow rate may be automatically detected without any external input to the pump. The steps of 12-14 of the method can be carried out by a control unit of the pump (e.g., a controller) and / or by an external computing device. For instance, the control unit thereby executes an algorithm which can implement a control mode for the domestic hot water system. The algorithm can utilize the internal media temperature estimate to adjust its operation and runtime. The algorithm can analyze the temperature and the time it takes for the pump to recirculate hot water from a supply. Grundfos Holding A / S Figs. 2A-C show temperature profiles in the hot water system according to an embodiment. In particular, each of Figs. 2A-C shows a change of temperature over time during two pump cycles, wherein in each of the figures a different stop criteria causes the stopping of the pump. The temperature (y-axis) may thereby refer to the temperature of the fluid which is obtained (e.g., estimated) by the pump. In Fig. 2A, the pump starts when the temperature value Tmedia reaches the lower threshold value (here referred to as: minimum temperature limit), and stops after the determined amount of time has lapsed (stop criteria b). In Fig. 2B, the upper threshold value (maximum temperature limit) is set to a lower value. As a consequence, the pump reaches this upper threshold value first and consequently stops to run (stop criteria a). In Fig. 2C, the pump starts to run when the temperature value Tmediareaches the lower threshold value (Tmin) or when the pump is stopped for the predetermined off-time. Compared to e.g. Fig. 2A or 2B, the flow rate is much higher and also the upper threshold value is set to a higher temperature. As a consequence, the temperature reaches the stop criteria c) first, i.e. the temperature increases by the determined amount (MaxDeltaTemp). As can be seen in Figs. 2A-C, the pump can start each time a start criteria (or start condition) is met. This start criteria can be the reaching of the lower threshold value (Tmin), which is a minimum temperature value (e.g., 95 °F / 35 °C), or (as a fallback option) a maximum off time (e.g., 60 min). Grundfos Holding A / S In summary, the stop criteria (or stop conditions) for stopping the pump in each cycle can comprise: - the reaching of the upper threshold value (also referred 5 to as: maximum temperature limit; e.g., 102 °F / 38.9 °C); - the maximum temperature increase while the pump is running (e.g., 10 °F / 5,56 °C); - or, as a fallback, the passing of the determined amount of time since the start of the pump (also referred to as: 10 maximum ON time; e.g., 5 minutes). As shown in Fig. 2C, the temperature might not drop immediately when the pump is stopped and can thus “overshoot” the MaxDeltaTemp threshold. This effect can depend on how the 15 temperature is obtained and can be considered or compensated when controlling the pump. There can be further constraints to this temp / time control of the pump. For instance, the minimum settable off-time can be 15 20 min and the minimum settable on-time can be 2 minutes. Fig. 3 shows further temperature profiles in the hot water system according to an embodiment. Thereby, the on-time threshold (i.e., the stop criteria for the amount of time which has lapsed 25 since the start of the pump) is set to the exemplary value of 5 minutes. The different temperature profiles in Fig 3 demonstrate how the stop conditions of the pump can be utilized to determine if a 30 flow set point is too low or too high. Grundfos Holding A / S For instance, the flow set point being too high can be detected when the pump is stopped due to a temperature stop conditions (e.g., the reaching of the upper threshold value or the 5 temperature increase by the predetermined amount), and the flow set point being too low can be detected when the pump is stopped due to a runtime stop condition (e.g., passing of predetermined on-time since the start of the pump). 10 In the left diagram a) of Fig. 3, the temperature reaches the upper threshold value (indicated by the upper dashed line) well before the on-time threshold (here: 5 min). This indicates a flow rate which is too high, e.g. caused by an excessive flow set point. As a consequence, the pump can reduce the flow set 15 point in the next cycle. For instance, in case of such a “temperature stop”, the flow set point can be decreased by 0.1 GPM in the next cycle. In the middle diagram b) of Fig. 3, the temperature reaches the 20 upper temperature threshold at about the same time as the predetermined on-time. This indicates an optimal flow. In this situation, the flow rate or more specifically the flow set point might not be adapted in the next cycle (i.e., the flow set point can be maintained). 25 For instance, this optimal condition can be detected, if the on- time is reached while the temperature is within the upper and lower threshold value. 30 In the right diagram c) of Fig. 3, the temperature is significantly below the lower threshold value indicated by the lower dashed line and the starting of the pump has no effect on Grundfos Holding A / S the temperature. This indicates that the flow may be too low to even activate a heat source of the hot water system. Due to the temperature not increasing, the pump runs until the predetermined on-time is reached (i.e., the pump is stopped due 5 to the maximum runtime stop criteria a) and then stops for the off-time (e.g., 15 min) until the start of the next cycle. In this situation, the pump can increase the flow rate in the next cycle (e.g., by increasing the flow set point). For instance, in case of such a “time stop”, the flow set point can be 10 increased by 0.2 GPM in the next cycle. With this approach, the flow set point of the hot water system can be adjusted dynamically to achieve optimal flow conditions. For instance, the flow set point can be adjusted between a 15 minimum flow set point of 1 GPM and a maximum flow set point of 4 GPM. An initial flow set point can be 3.5 GPM. Fig. 4 shows different operating conditions over time in a simulated hot water system according to an embodiment. 20 The top diagram in Fig. 4 shows the change of flow set point (“flow reference”, bold line 53) and a pump flow parameter over time, the middle diagram shows the corresponding fluid (or media) temperature and the bottom diagram shows different 25 algorithm trigger. In the middle diagram, the zigzagging line 54 is the obtained temperature of the fluid, the top horizontal line is the media supply temperature (Tsup), the upper dashed line is the upper 30 threshold value and the lower dashed line is the lower threshold value. The temperature 54 overshooting the upper threshold value in most cycles can at least partially be caused by a thermal Grundfos Holding A / S delay which can be considered or compensated when adapting the pump setting. In a first phase (until ca. 18 hours), the temperature during 5 each subsequent run of the pump strongly exceeds the upper threshold value due to the flow rate being too high. This causes the pump to stepwise reduce the flow set point (in Fig. 4: flow reference point) from cycle to cycle. In the indicated region 51, the flow rate is so far reduced that the temperature does 10 not longer reach the upper threshold value while the pump is running (stop condition: max runtime exceeded). As a consequence, the pump increases the flow set point again. This can be caused by a “runtime stop” algorithm trigger which is executed when the “runtime stop” is detected. 15 After the sharp increase, the flow set point can be decreased with a predefined decay rate. This results in the flow set point slowly decaying over time (as can be seen in indicated region 52). This can prevent the algorithm from getting stuck at a too 20 high flow set point. For instance, the flow set point is reduced with the predefined decay rate if a temperature stop criteria is reached after a previous increase of the flow set point. There can be additional temperature drops due to tapping events 25 (not shown in Fig. 4). The pump can be configured to ignore such tapping events. For instance, the flow set point is not adapted if a temperature drop is caused by a tapping event. Thus, the flow set point can be adjustment dynamically and in a 30 continuous manner to minimize the flow set point while ensuring a reaching of a desired temperature in the system (and thus a certain comfort). An advantage of this approach is that it Grundfos Holding A / S requires no input from a user or from a heat source providing a signal for the flow set point. It can be as simple as installing the pump and let it continuously optimize the flow set point over time, based on a monitoring of temperatures values and time 5 during the pump operation cycles. Fig. 5 shows another example of a typical temperature profile. Thereby, two activation phases of the pump (e.g., at two different days) are shown. During each activation phase, the 10 pump is operated in the cyclical manner, causing the temperature to fluctuate between the lower threshold value (Tmin) and the upper threshold value (Tmax). Between the activation phases, there can be inactivity phases (e.g., at night) during which the pump does not operate causing the temperature to fall below the 15 lower threshold value. Fig. 6 shows a schematic diagram of a hot water system 20 according to an embodiment. The system 20 can be a domestic hot water system. 20 The hot water system 20 can comprise a hot water supply, such as a supply line and / or a hot water production system 22 (e.g. a boiler, a heat tank or a heat exchanger) at location A. The hot water supply can supply hot water to a hot water 25 recirculation line 21 from which several fixtures 23 (i.e., consumers) along the line 21, such as sinks, can withdraw hot water. After passing the fixtures 23, the hot water recirculation line 21 can lead back to the hot water supply. 30 The pump 40 can be arranged on and / or connected to the hot water recirculation line 21 downstream of the fixtures 23 (e.g., at location C downstream of location B in Fig. 6), and can be Grundfos Holding A / S configured to circulate the hot water back to the production system 22 The system 20 may further comprise a cold water supply line 24 5 and a return line. The hot water system 20 can be a residential or a commercial domestic hot water system. The hot water system 20 can be a hot water recirculation system. 10 Fig. 7 shows a schematic diagram of the pump 40 for use in the hot water system 20 according to an embodiment. The pump 40 can be configured to operate in a cyclical manner to periodically pump a fluid through the system 20. For example, the pump 40 can 15 be configured to carry out the method 10 as shown in Fig. 1. The pump 40 comprises: a measurement unit 42 configured to directly or indirectly obtain a temperature of a fluid in the system 20; and a control unit 43 configured to start the pump 20 40 with the given pump setting when the temperature reaches a lower threshold value while the pump 40 is stopped, or when the pump 40 is stopped for the predetermined off-time; wherein the control unit 43 is configured to stop the pump 40 again if at least one of the number of stop criteria is detected by the 25 control unit 43, wherein the number of stop criteria comprises at least one of the following criteria: a) the temperature reaches the upper threshold value, and b) the predetermined amount of time has lapsed since the start of the pump 40. The control unit 43 is further configured to adapt the pump setting 30 for the subsequent start of the pump based on the detected stop criteria. Grundfos Holding A / S The number of stop criteria can further comprise: c) the temperature having increased by the predetermined amount since the start of the pump 40. 5 The control unit 43 can comprise a detection unit configured to detect if a stop criteria is reached. The detection unit can be implemented by hardware and / or software. The pump 40 can be a circulation pump or a recirculation pump. 10 The pump 40 can also be a water transfer pump. In particular, the pump 40 is configured to circulate water through the hot water recirculation line 21 of the hot water system 20. Therefore, the pump 40, in particular the pump body, 15 can be connected to the hot water recirculation line 21 of the system 40, e.g. a hot water pipe of the system. The pump setting can be a flow set point of the pump. This flow set point can determine a flow rate when the pump is running. 20 For instance, the pump setting can comprise setting a pump speed of a drive of the pump. The measurement unit 42 can be configured to estimate the temperature based on a temperature of a pump component which 25 relates to the temperature of the fluid in a known way. Alternatively, the measurement unit is configured to measure the temperature value in a fluid carrying element of the pump 40 or in a hot water recirculation line 21 of the hot water system 20. 30 The pump 40 can comprise a flow sensor and / or a flow estimator 44 configured to detect the flow rate of the fluid. This allows the pump to approximate the flow rate. Grundfos Holding A / S The pump can also have a communication interface which allows forwarding pump status information and / or receiving configuration commands. 5

Claims

Grundfos Holding A / S Claims 1. A method (10) for adapting an operation of a pump (40) of a hot water system (20), the method (10) comprising the steps of: directly or indirectly obtaining (11) a temperature of a fluid in the hot water system (20); starting (12) the pump (40) with a given pump setting when the temperature reaches a lower threshold value while the pump (40) is stopped, or when the pump (40) is stopped for a predetermined off-time; stopping (13) the pump (40) again if at least one of a number of stop criteria is detected, wherein the number of stop criteria comprises at least one of the following criteria: - a) the temperature reaches an upper threshold value, - b) a predetermined amount of time has lapsed since the start of the pump (40); adapting (14) the pump setting for a subsequent start of the pump (40) based on the detected stop criteria.

2. The method (10) of claim 1, wherein the number of stop criteria further comprises the following criteria: - c) the temperature has increased by a predetermined amount since the start of the pump (40).

3. The method (10) of any one of the preceding claims, wherein the pump setting is adapted (14) for the subsequent start of the pump (40) based on which of the number of stop criteria is detected first.

4. The method (10) of any one of the preceding claims,Grundfos Holding A / S wherein the pump setting is a flow set point of the pump (40).

5. The method (10) of claim 4, wherein the adaption (14) of the pump setting comprises an increase of the flow set point for the subsequent start of the pump (40) if the detected stop criteria is the lapsing of the determined amount of time.

6. The method (10) of any one of claims 4 to 5, wherein the adaption (14) of the pump setting comprises a reduction of the flow set point for the subsequent start of the pump (40) if the detected stop criteria is the reaching of the upper threshold value.

7. The method (10) of claim 2 and of any one of claims 4 to 6, wherein the adaption (14) of the pump setting comprises a reduction of the flow set point for the subsequent start of the pump (40) if the detected stop criteria is the increase of the temperature by the predetermined amount.

8. The method (10) of claim 6 or 7, wherein the flow set point is reduced by a predetermined reduction rate if the detected stop criteria is the reaching of the upper threshold value or the increase of the temperature by the predetermined amount, and if a previous adaption of the flow set point was an increase of the flow set point.

9. The method (10) of any one of the preceding claims, wherein the given pump setting is maintained for the subsequent start of the pump if the detected stop criteria isGrundfos Holding A / S the lapsing of the determined amount of time and the temperature is within a lower and an upper temperature threshold.

10. The method (10) of any one of the preceding claims, wherein the temperature of the fluid is estimated based on a temperature of a pump component which relates to the temperature of the fluid, or wherein the temperature of the fluid is measured in a fluid carrying element of the pump (40) or in a hot water recirculation line (21) of the hot water system (20).

11. The method (10) of any one of the preceding claims, wherein the method (10) is carried out continuously during a regular operation of the pump (40).

12. A pump (40), in particular a circulation pump, for a hot water system (20), wherein the pump (40) comprises: a measurement unit (42) configured to directly or indirectly obtain a temperature of a fluid in the system; and a control unit (43) configured to start the pump with a given pump setting when the temperature reaches a lower threshold value while the pump (40) is stopped, or when the pump (40) is stopped for a predetermined off-time; wherein the control unit (43) is configured to stop the pump (40) again if at least one of a number of stop criteria is detected by the control unit (43), wherein the number of stop criteria comprises at least one of the following criteria: - a) the temperature reaches an upper threshold value, - b) a predetermined amount of time has lapsed since the start of the pump (40); wherein the control unit (43) is further configured to adapt the pump setting for a subsequent start of the pump (40)Grundfos Holding A / S based on the detected stop criteria.

13. The pump (40) of claim 12, further comprising: wherein the pump setting is a flow set point of the pump (40).

14. The pump (40) of claim 12 or 13, further comprising: a flow sensor and / or a flow estimator (44) configured to detect a flow rate of the fluid.

15. A hot water system (20), comprising: the pump (40) of any one of claims 12 to 14; and a hot water recirculation line (21) which is connected to the pump (40).

Images