Hot water supply system

Abstract

Provided is a hot-water supply system capable of accurately determining whether a hot-water supply terminal is in an open state during an instant hot-water operation with a simple configuration. The hot-water supply system is capable of performing temporary determination control and determination confirmation control with respect to whether the hot-water supply terminal is in an open state during the instant hot-water operation. In the temporary determination control, flow rate constant control is performed in which the rotational speed of a pump for hot-water circulation is controlled so that the total flow rate is maintained at a prescribed first command flow rate during the instant hot-water operation. At this time, in a case where the rotational speed is lower than a first determination value, it is temporarily determined that the hot-water supply terminal is in the open state. In the determination confirmation control, control is performed in which the rotational speed of the pump is gradually reduced with the total flow rate being targeted at a prescribed second command flow rate. At this time, in a case where the rotational speed is lower than a prescribed second determination value, it is determined that the hot-water supply terminal is in the open state.

Description

Technical Field

[0001] This invention relates to a hot water supply system capable of providing instant hot water. Here, "instant hot water operation" in this specification refers to the following action: heated hot water at a specified temperature or above circulates in a hot water circulation path connected to a hot water supply terminal, so that when the hot water supply terminal in the hot water supply system is set to the open state (meaning that hot water at a minimum operating flow rate MOQ or above is output from the hot water supply terminal), hot water at a specified temperature or above can immediately flow from the hot water supply terminal. Background Technology

[0002] As a hot water supply system, there are, for example, the hot water supply systems described in Patent Document 1 and Patent Document 2.

[0003] The hot water supply systems described in Patent Documents 1 and 2 can supply hot water heated by a heat exchanger to a hot water supply terminal via a hot water outlet path. On the other hand, a return flow path including a pump is connected to the hot water outlet path to form a hot water circulation path that allows the hot water in the hot water outlet path to circulate in a certain path by driving the pump.

[0004] In this type of hot water supply system, when the hot water supply terminal is closed and the outflow of hot water from the hot water supply terminal stops, instantaneous hot water operation can be performed, circulating the hot water heated by the heat exchanger in the hot water circulation path. If this instantaneous hot water operation is performed, then when the hot water supply terminal is opened, hot water at a specified temperature or higher will immediately flow out from the hot water supply terminal in the hot water circulation path, which is very convenient.

[0005] However, as described below, there is room for improvement in the prior art.

[0006] That is, in the hot water supply systems of Patent Document 1 and Patent Document 2, when the hot water supply terminal is in the open state during instant hot water operation, it is necessary to appropriately detect this situation and switch from instant hot water operation to normal hot water supply operation.

[0007] Here, in Patent Document 1, as a means, two flow sensors are used, capable of detecting the circulating flow rate of the return flow path of the hot water circulation path and the so-called tank flow rate at different locations. When the relationship (tank flow rate - circulating flow rate) ≥ a predetermined threshold is met, it can be determined that the hot water supply terminal is in the open state. However, according to this structure, the two flow sensors must be used. For example, if the flow sensor for detecting the circulating flow rate is omitted, it is difficult to determine whether the hot water supply terminal is set to the open state.

[0008] On the other hand, Patent Document 2 describes a structure that omits the flow sensor used to detect the circulating flow rate, thus simplifying the structure. Furthermore, in that document, the hot water supply terminal is determined to be open by detecting the hot water flow rate when the pump for hot water circulation is running or stopped, and comparing it to a predetermined threshold. However, the hot water flow rate varies depending on individual pump differences or the conditions of the hot water supply system's installation site, and is a parameter that changes over the years. Therefore, there are concerns about the accuracy of the determination unit, and there is room for improvement in this regard.

[0009] [Existing Technical Documents]

[0010] [Patent Literature]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2021-103027

[0012] [Patent Document 2] Japanese Patent No. 3171979 Summary of the Invention

[0013] [The problem the invention aims to solve]

[0014] The present invention was conceived based on the aforementioned situation, and its objective is to provide a hot water supply system that can accurately determine whether the hot water supply terminal is in the open state during real-time hot water operation through a simple structure.

[0015] [Technical means to solve the problem]

[0016] To address the aforementioned issues, the following technical means are employed in this invention.

[0017] A hot water supply system according to a first aspect of the present invention includes: an inlet passage capable of introducing externally supplied hot water into an inlet of a hot water heating unit; a hot water outlet passage capable of introducing the hot water that has passed through the hot water heating unit into a hot water supply terminal; a hot water circulation passage including a return flow passage branching from a midpoint of the hot water outlet passage and connecting the midpoint to the inlet passage, and equipped with a pump for hot water circulation, the pump for hot water circulation being capable of performing instant hot water operation to circulate the hot water from the hot water outlet passage back to the inlet of the hot water heating unit; a flow sensor disposed at a different location in the hot water circulation passage from the return flow passage; and a control unit for determining whether the hot water supply terminal is in an open state during the instant hot water operation, wherein the control unit is capable of performing temporary judgment control and judgment determination control, and is configured such that: in the temporary judgment control, based on... The instant hot water operation uses the hot water flow rate detected by the flow sensor to calculate the total flow rate Qt, which is obtained by adding the hot water flow rate in the return flow path to the inlet flow rate entering the inlet path from the outside. The pump speed N is controlled to maintain the total flow rate Qt at a predetermined first command flow rate Q1. If the pump speed N is lower than a first judgment value N1 during the flow rate control, the hot water supply terminal is temporarily determined to be in an open state. This determination control is executed after the temporary determination. Furthermore, the determination control gradually reduces the pump speed N to a second command flow rate Q2 that is less than the first command flow rate Q1. If the pump speed N is lower than a predetermined second judgment value N2 during its execution, the hot water supply terminal is determined to be in an open state.

[0018] Based on this structure, the following effect is achieved.

[0019] The temporary judgment control considers the following situation: when the pump is controlled to maintain the total flow rate Qt at a predetermined first command flow rate Q1 during instantaneous hot water operation, if the hot water supply terminal is open and hot water is flowing out, water will enter from the outside, and therefore the pump speed N will decrease accordingly. According to the temporary judgment control, it is possible to detect that the hot water supply terminal is open based on the pump speed N being lower than a first judgment value N1.

[0020] However, relying solely on the aforementioned temporary judgment control may lead to false detections. Specifically, the relationship between pump speed N and flow rate largely depends on the piping resistance (piping length) of the hot water circulation path. For example, if a first judgment value N1 is set under conditions of long piping length, there is still a concern about judgment errors even with short piping lengths. Furthermore, false detections may also occur when pump characteristics change due to pump replacement, debris blockage, or changes in piping length.

[0021] According to the present invention, after the temporary judgment control, a judgment confirmation control is executed. This judgment confirmation control is based on the following situation: when the pump speed N is gradually reduced so that the total flow rate Qt becomes the second commanded flow rate Q2, when the hot water supply terminal is open and hot water is flowing out, water will flow in from the outside, so the pump speed N is lower than the original speed N. According to this judgment confirmation control, the judgment of whether the hot water supply terminal is open is performed at a different time and in a different pump speed range than the temporary judgment control. Therefore, the judgment based on a series of controls, including the temporary judgment control and the judgment confirmation control, can achieve a judgment with high accuracy and reliability. When it is determined that the hot water supply terminal is open, the instantaneous hot water operation is stopped and switched to normal hot water supply operation, but according to the present invention, this switching operation can be performed appropriately.

[0022] Since there is no need for a flow sensor for detecting hot water flow in the return flow path, cost reduction can also be achieved.

[0023] In this invention, it is preferable that the hot water heating unit is configured to perform hot water heating under the condition that the hot water flow rate in the hot water heating unit is a minimum working flow rate MOQ or above, and the second command flow rate Q2 is set to the minimum working flow rate MOQ or above.

[0024] Based on this structure, when the pump speed N is reduced in the control, the total flow rate Qt can be made not less than the minimum operating flow rate MOQ, thus avoiding the undesirable situation where the hot water heating unit cannot be used for hot water heating during instantaneous hot water operation.

[0025] In this invention, it is preferred that, in the determination control, if the pump speed N is reduced from a state that is not lower than the second determination value N2 to a state where the flow target of the total flow rate Qt becomes the second command flow rate Q2, and the total flow rate Qt is less than a predetermined third determination value Q3, it is determined that the hot water supply terminal is not in the open state.

[0026] Based on this structure, even if the hot water supply terminal is mistakenly detected as being open in the temporary judgment control, the subsequent judgment determination control can accurately determine that the hot water supply terminal is not open.

[0027] In this invention, it is preferable that, in the determination control, if it is determined that the hot water supply terminal is not in the open state, the temporary determination control is repeated, and when it is repeated, the first determination value N1 is set to a low speed value compared with the previous temporary determination control.

[0028] This structure is preferred because it continuously determines whether the hot water supply terminal is in the open state during instant hot water operation. Furthermore, if the first determination value N1 is the same as the previous temporary determination control when a new temporary determination control is performed, it would result in the same determination as the previous temporary determination control, raising concerns about potential deviation. However, this concern can be avoided with the aforementioned structure.

[0029] In this invention, the first determination value N1 is preferably obtained by subtracting a predetermined threshold Th from the predicted value β of the pump speed N for maintaining the total flow rate Qt at the first commanded flow rate Q1.

[0030] Based on this structure, an appropriate value can be set as the first judgment value N1, which improves the accuracy of the judgment result of the temporary judgment control, and is preferred in this respect.

[0031] In this invention, it is preferable that the predicted value β is obtained by learning using an exponential smoothing method in the instantaneous hot water operation, and the learning period is set to a short period when the predicted value β is on an increasing trend, compared with the case where it is not.

[0032] Based on this structure, the predicted value β can be set to an appropriate value corresponding to actual conditions such as pump deterioration or annual changes in the hot water circulation circuit, and thus be optimized.

[0033] Additionally, as referenced Figure 4 , Figure 5As described later, when the flow resistance of the hot water circulation path increases due to changes over the years, the predicted value β becomes higher. In this case, unlike the previous structure, if the learning period for the predicted value β becomes longer and there is no progress in updating the predicted value β, it becomes difficult to generate the difference between the pump speed N and the first judgment value N1 in the temporary judgment control, making it difficult to make an appropriate judgment. In contrast, according to the previous structure, in this case, since the learning period for the predicted value β is set to a short period, this situation can be appropriately eliminated. When the flow resistance of the hot water circulation path decreases and the predicted value β is on a decreasing trend, the learning period for the predicted value β is set to a long period, but the decrease in the flow resistance of the hot water circulation path only occurs at a rare frequency, such as when replacing the pump. Therefore, assuming that such a situation is tracked and the predicted value β is updated immediately, this predicted value β is not very suitable. In contrast, according to the previous configuration, this situation can also be appropriately avoided.

[0034] A hot water supply system according to a second aspect of the present invention includes: an inlet passage capable of introducing externally supplied hot water into the inlet of a hot water heating unit; a hot water outlet passage capable of introducing the hot water that has passed through the hot water heating unit into a hot water supply terminal; a hot water circulation passage including a return flow passage branching from a midpoint of the hot water outlet passage and connecting the midpoint to the inlet passage, and equipped with a pump for hot water circulation, the pump for hot water circulation capable of performing instant hot water operation to circulate the hot water from the hot water outlet passage back to the inlet of the hot water heating unit; a flow sensor disposed at a different location in the hot water circulation passage from the return flow passage; and a control unit capable of determining whether the hot water supply terminal is in an open state during the instant hot water operation, wherein the control unit is capable of performing temporary determination control and determination confirmation control, and is configured such that: In the temporary judgment control, based on the hot water flow detection value detected by the flow sensor during the instant hot water operation, the total flow rate Qt, obtained by adding the hot water flow rate of the return flow path and the inlet flow rate from the outside into the inlet path, is calculated. Then, a flow rate constantization control is performed to control the pump speed N so that the total flow rate Qt is maintained at a predetermined first command flow rate Q1. If the speed N is lower than a first determination value N1 during the flow rate constantization control, it is temporarily judged that the hot water supply terminal is in an open state. The judgment determination control is executed after the temporary judgment. Furthermore, the judgment determination control is executed to reduce the pump speed N. If, even though the pump speed N is reduced to a predetermined speed, the total flow rate Qt is still greater than the predetermined flow rate, it is determined that the hot water supply terminal is in an open state.

[0035] According to this structure, similar to the hot water supply system provided according to the first aspect of the present invention, it is possible to accurately determine whether the hot water supply terminal is in the open state during real-time hot water supply operation through a series of controls including temporary judgment control and judgment determination control.

[0036] Furthermore, in the judgment determination control of the hot water supply system provided in the second aspect, the hot water supply terminal is judged to be in the open state based on the situation that the total flow rate Qt is greater than the specified flow rate even though the pump speed N is reduced to the specified speed. This judgment can be set to an accurate judgment.

[0037] Other features and advantages of the invention will become more apparent from the accompanying drawings and from the following description of embodiments of the invention. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating an example of the hot water supply system of the present invention.

[0039] Figure 2 It means in Figure 1 The flowchart shows an example of the sequence of actions performed in a hot water supply system.

[0040] Figure 3 This is a graph showing an example of the relationship between pump speed N and flow rate.

[0041] Figure 4 This is a graph showing an example of the relationship between pump speed N and flow rate.

[0042] Figure 5 This is a graph showing an example of the relationship between pump speed N and flow rate.

[0043] Figure 6 It means in Figure 1 A flowchart illustrating another example of the sequence of actions performed in a hot water supply system.

[0044] Explanation of icon numbers

[0045] SY: Hot water supply system

[0046] A: Hot water supply device

[0047] C: Hot water circulation circuit

[0048] P: Pump

[0049] Sa: Flow sensor

[0050] 1: Water inlet

[0051] 2: Hot water supply line

[0052] 3: Return Flow Path

[0053] 4: Heat exchanger (hot water heating unit)

[0054] 6: Control Unit (Control Unit) Detailed Implementation

[0055] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0056] Figure 1 The hot water supply system SY shown includes: a hot water supply device A, an inlet water path 1, a hot water outlet water path 2, a return flow path 3, and a hot water circulation path C equipped with a pump P for hot water circulation. The hot water supply device A is configured to house a heat exchanger 4 for hot water heating, a burner 5, a control unit 6, etc., within an outer casing 7. The burner 5 is, for example, a gas burner or an oil burner. The heat exchanger 4 is a specific example of the hot water heating unit described in this invention, and is constructed, for example, using finned tubes. Hot water fed into the heat exchanger 4 from its inlet 4a can be heated by the combustion gases generated by the burner 5 and flows out from the outlet 4b. However, hot water heating based on the heat exchanger 4 is performed under the condition that the flow rate of the hot water flowing in the heat exchanger 4 is at least a predetermined minimum operating flow rate MOQ.

[0057] The water inlet path 1 is divided into an internal water inlet path 1a and an external water inlet path 1b located inside and outside the outer casing 7, respectively. Hot water, such as tap water, is supplied to the water inlet path 1 from outside the hot water supply system SY at a specified water pressure. The hot water supplied to the water inlet path 1 is then introduced into the inlet 4a of the heat exchanger 4.

[0058] Hot water outlet path 2 connects the outlet 4b of heat exchanger 4 to hot water supply terminal 8, supplying hot water to the hot water supply terminal 8. It is divided into an internal hot water outlet path 2a and an external hot water outlet path 2b, located inside and outside the outer casing 7, respectively. The internal hot water outlet path 2a is connected to the internal inlet path 1a via a bypass path 18 and a flow regulating valve Va, which acts as a distribution valve. For the hot water flowing in the internal hot water outlet path 2a, unheated hot water mixed with the hot water from the internal inlet path 1a is supplied via the bypass path 18, thereby adjusting the hot water temperature. The flow regulating valve Va controls the hot water flow rate Qc to the heat exchanger 4 and the hot water flow rate Qd to the bypass path 18. A flow sensor Sa is installed downstream of the flow regulating valve Va.

[0059] Return flow path 3 is a flow path that connects the midpoint of the hot water outlet path 2 near the hot water supply terminal 8 to the midpoint of the internal inlet water path 1a upstream of the flow rate regulating valve Va. It is divided into an internal return flow path 3a and an external return flow path 3b, located inside and outside the outer casing 7, respectively. A hot water circulation pump P is installed in the internal return flow path 3a.

[0060] Pump P can be driven by, for example, a direct current (DC) motor whose speed N can be controlled by pulse width modulation and by adjusting the control voltage. Driving pump P causes hot water flowing from the outlet 4b of heat exchanger 4 to the hot water outlet path 2 to return via the return path 3 to the middle section of the inlet path 1, and then back to the inlet 4a of heat exchanger 4. These heat exchanger 4, hot water outlet path 2, return path 3, and a portion of the inlet path 1 constitute the hot water circulation path C.

[0061] The control unit 6 is an example of the control unit described in this invention, and is constructed using a microcomputer or the like. The control unit 6 performs operation control of each part of the hot water supply device A, but as will be described later, in addition to controlling the instant hot water operation, it also performs temporary judgment control and judgment determination control for determining whether the hot water supply terminal 8 is in the open state during instant hot water operation.

[0062] The control unit 6 is connected to a remote control 60, for example, installed in a bathroom or kitchen. The remote control 60 includes multiple operation switches 60a for setting various action commands or data inputs, and a display unit 60b for displaying data.

[0063] Next, refer to Figure 2 The flowchart illustrates an example of the action control of the hot water supply system SY, and also explains its function.

[0064] First, when the instant hot water operation start conditions are met, the flow regulating valve Va performs control to fully open the heat exchanger 4 side and fully close the bypass flow path 18 side (making the flow rate Qd zero), and then the pump P starts operating (S1: YES, S2, S3). Specific examples of instant hot water operation start conditions include situations such as when a switch operation for starting instant hot water operation is performed or the timer setting time arrives, the instant hot water operation start period has arrived, no hot water supply operation is currently in progress, and the temperature detected by the temperature sensor (not shown) in the hot water outlet path 2 is not above a specified high temperature. By starting the operation of the pump P, hot water circulates in the hot water circulation path C.

[0065] When pump P starts operating, control unit 6 performs temporary judgment control to determine whether hot water supply terminal 8 is in the open state.

[0066] In the temporary judgment control, the flow rate constant control (S4) is first performed to control the speed N of pump P so that the total flow rate Qt is maintained at the specified first command flow rate Q1.

[0067] Here, the total flow rate Qt is the sum of the hot water flow rate Qb returning to flow path 3 and the inlet water flow rate Qa entering the inlet water path 1 from the outside. Since the flow rate Qd on the bypass flow path 18 side of the flow regulating valve Va is initially set to 0, the flow rate Qc detected by the flow sensor Sa is directly equivalent to the total flow rate Qt. Furthermore, even when the flow rate Qd is not zero, the total flow rate Qt can be calculated based on the flow rate Qc detected by the flow sensor Sa and the distribution ratio of the flow regulating valve Va.

[0068] The first instruction flow rate Q1 is the target flow rate, for example, 7 [L / min].

[0069] Next, after a predetermined standby time (e.g., about 5 seconds) from the start of pump P's operation, a determination is made as to whether the pump P's rotational speed N is lower than a predetermined first determination value N1 (S5: Yes, S6). The standby time is to prevent the determination from being made before pump P has fully started operating. The first determination value N1 is set to, for example, the following value.

[0070] N1 = (β - Th)

[0071] Here,

[0072] β: is the predicted value of the rotational speed N of pump P used to maintain the total flow rate Qt at the first commanded flow rate Q1.

[0073] Th: is the threshold, for example, 400 (rpm).

[0074] The predicted value β was obtained by learning using exponential smoothing during instantaneous hot water operation, the details of which will be described later.

[0075] In step S6, if the pump P's rotational speed N is lower than the first determination value N1 and this condition persists for more than a first predetermined time, a temporary determination is made that the hot water supply terminal 8 is in the open state (S6: Yes, S7). The first predetermined time is, for example, about 0.5 seconds, but is not limited to this. The second predetermined time, described later, is the same.

[0076] When pump P is controlled to maintain the total flow rate Qt at the first commanded flow rate Q1, and hot water supply terminal 8 is set to the open state and hot water flows out, water enters the inlet circuit 1 from the outside, increasing the inlet flow rate Qa. Pump P correspondingly reduces its speed to decrease the jet volume, making it lower than the first judgment value N1. Based on this phenomenon, the open state of hot water supply terminal 8 can be appropriately detected according to the temporary judgment control.

[0077] If reference Figure 3The temporary judgment control is as follows: when the original pump speed N shown on line L1 deviates to line L1' due to the increase of the inlet water flow Qa from the outside, and the deviation is above the threshold Th, it is temporarily judged that the hot water supply terminal 8 is in the open state.

[0078] However, relying solely on the temporary judgment control may lead to erroneous judgments; therefore, the judgment is set to be temporary. That is, the relationship between the pump P's rotational speed N and the hot water flow rate largely depends on the piping resistance (piping length) of the hot water circulation path C. Therefore, the first judgment value N1 is, for example, suitable for cases with short piping lengths. Conversely, if the first judgment value N1 is used directly when the piping length is long, erroneous judgments may occur. Erroneous judgments can also occur when pump characteristics change due to pump P replacement, blockage, or changes in piping length. In contrast, according to this embodiment, to eliminate such erroneous judgments, judgment determination control is further executed as described below.

[0079] In the determination control, control is performed to gradually (in stages, in units of a specified speed) reduce the speed N of pump P so that the total flow rate Qt is less than the first commanded flow rate Q1 by a second commanded flow rate Q2. The second commanded flow rate Q2 is, for example, a value obtained by adding an appropriate margin value to the minimum operating flow rate MOQ (or it can be set to the minimum operating flow rate MOQ). If such a value is set, the total flow rate Qt will not be lower than the minimum operating flow rate MOQ, thus avoiding the undesirable situation where it becomes difficult to heat the hot water using heat exchanger 4.

[0080] As described above, during the process of gradually reducing the speed N of pump P, if the speed N of pump P is lower than the predetermined second determination value N2 and the state continues for more than the second predetermined time, the hot water supply terminal 8 is determined to be in the open state (S9: Yes, S10).

[0081] During the stage of reducing the pump P's rotational speed N to make the total flow rate Qt reach the second commanded flow rate Q2, if the hot water supply terminal 8 is in the open state, the pump P's rotational speed N should eventually be zero and lower than the second determination value N2. Based on this phenomenon, the above-mentioned content can be appropriately determined when the hot water supply terminal 8 is in the open state. The second determination value N2 only needs to be set to a value greater than zero (e.g., 600 [rpm]), thereby allowing the determination control to end without waiting for the pump P's rotational speed N to become zero, and stopping the immediate hot water operation (in Figure 3 omitted).

[0082] Based on the aforementioned temporary judgment control and judgment determination control, the determination of whether the hot water supply terminal 8 is in the open state is performed at different times and at different speed ranges of the pump P. Therefore, the judgment based on this series of controls can be set to a judgment with high accuracy and reliability. When it is determined that the hot water supply terminal 8 is in the open state, the instantaneous hot water operation is stopped and switched to normal hot water supply operation as described above, but this switch can be performed at an appropriate time.

[0083] Unlike the previous case, if step S9 is NO, and the total flow rate Qt reaches the second commanded flow rate Q2, and the total flow rate Qt is less than the third determination value Q3, then the determination that the hot water supply terminal 8 is in the open state is uncertain (S12: Yes, S13: Yes). The third determination value Q3 is set to a value greater than the second commanded flow rate Q2. Although the pump P speed N is reduced, if the total flow rate Qt is sufficiently low, it can be determined that the hot water supply terminal 8 is not in the open state, and this determination corresponds to this situation. Furthermore, when the total flow rate Qt reaches a stage that is approximately consistent with the second commanded flow rate Q2, the reduction of the pump P speed N slows down. If there is a certain period of standby, the pump P speed N will be lower than the second determination value N2, but this would waste standby time and raise concerns about incorrect judgments due to previous judgment processing. According to S12 and S13, this concern can also be eliminated.

[0084] If the hot water supply terminal 8 is not determined to be in the open state during the determination control, the threshold Th is set to a value greater than only the value corresponding to the predetermined value λ (first determination value N1 (N1=β-(Th+λ))), and the temporary determination control is performed again (S13: Yes, S14, S4). Thus, the determination of whether the hot water supply terminal 8 is in the open state is continuously executed. However, unlike setting the threshold Th to only the value corresponding to the value λ, if the threshold Th is the same, the same determination will be performed in the re-performed temporary determination control, which may lead to deviation. This embodiment also avoids this concern.

[0085] The previously delayed prediction β was the predicted value of the pump P rotational speed N required to eject the first commanded flow rate Q1 (e.g., 7 [L / min]), and the latest prediction β (the prediction β at the current moment) is the prediction value. 〔n〕 It is calculated by learning and using the exponential smoothing method. Specifically, it is calculated using the following Equation 1.

[0086] β 〔n〕 =(La·β 〔n-1〕 +N 〔n〕 ) / (La+1) ···Equation 1

[0087] Here,

[0088] β〔n-1〕 The previous predicted value. Furthermore, the initial value of β was pre-set based on experiments and other factors.

[0089] N 〔n〕 : Pump speed N at the current moment (actual speed).

[0090] La: A coefficient used to account for the flow path resistance of the hot water circulation path, compared to (N) 〔n〕 ≧β 〔n-1〕 When the condition is met, in (N) 〔n〕 <β 〔n-1〕 When the condition is met, set it to a larger value.

[0091] Learning is performed only when the total flow Qt is close to the first instruction flow Q1.

[0092] In addition, the learning period for the predicted value β is preferably set to short when the predicted value β is on an increasing trend, and to long when the predicted value β is on a decreasing trend.

[0093] That is, if the flow resistance of the hot water circulation path C increases due to changes over the years, the predicted value β will become higher. In this case, if it is assumed that the learning period for the predicted value β becomes longer and the update of the predicted value β does not progress, it will be difficult to generate the difference between the pump P speed N and the first judgment value N1 in the temporary judgment control, making it difficult to make an appropriate judgment. Figure 4 In the original characteristics of pump P, line L2 represents the deviation as line L2' increases when the flow path resistance increases. Within line L2', when the hot water supply terminal 8 is open and water enters the inlet path 1, the deviation is line L2''. In this state, the deviation between lines L2 and L2'' in the predicted value β is small, making it difficult to detect the open state of the hot water supply terminal 8.

[0094] In contrast, according to the structure described in this embodiment, since the learning period of the predicted value β is set to a short period, the aforementioned situation can be appropriately eliminated.

[0095] Conversely, when the flow resistance of the hot water circulation path C decreases and the predicted value β shows a decreasing trend, the learning period for the predicted value β is set to a long period. The decrease in the flow resistance of the hot water circulation path C occurs only at a rare frequency, such as when pump P is replaced. Therefore, if the predicted value β is updated immediately assuming this situation is followed, it would be inappropriate. In contrast, the structure described in this embodiment can appropriately avoid this situation.

[0096] If the learning period of the above predicted value β is referenced Figure 5To explain, when the line L3 represents the original characteristics of pump P, the learning cycle becomes shorter when the line is biased towards L3', and conversely, the learning cycle becomes longer when the line is biased towards L3''.

[0097] In the hot water supply system SY, it can also be configured as an execution Figure 6 The motion control shown replaces Figure 2 The motion control shown.

[0098] also, Figure 6 Steps S20 to S22 in the flowchart are related to Figure 2 Different parts, and in addition to Figure 2 Same as above, repeated descriptions omitted.

[0099] exist Figure 6 In step S7, after temporarily determining that the hot water supply terminal 8 is in the open state, as a control for determining the determination, the control that causes the speed N of pump P to be reduced in stages in fixed speed units is first executed (S20). As a result, if the total flow rate Qt is greater than the specified flow rate when the speed N of pump P is reduced to the specified speed, the determination is that the hot water supply terminal 8 is in the open state (S21: Yes, S22: Yes, S10).

[0100] The specified rotational speed can be set to zero, and the speed can be reduced until the pump P stops. However, it can also be set to a speed other than zero.

[0101] Based on the aforementioned judgment and control, although the pump P's rotational speed N is significantly reduced or reduced to zero, the total flow rate Qt is greater than the specified flow rate. Therefore, it is determined that the hot water supply terminal 8 is set to the open state. Thus, this judgment is considered accurate, and combining it with the judgment from the previously executed temporary judgment and control improves the reliability of the final judgment.

[0102] This invention is not limited to the embodiments described herein. Various design changes can be freely made to the specific structure of each part of the hot water supply system of this invention within the scope of the invention's intent.

[0103] The various values ​​used in the control can be changed appropriately.

[0104] Of course, the hot water supply terminal is not limited to one; it can also be configured to have multiple terminals.

[0105] There are no restrictions on the specific type of pump, as long as its speed is variable.

[0106] This invention is also applicable to hot water supply systems that include a hot water storage tank. In this case, a liquid-liquid / heat exchanger can be used as a heat exchanger for heating the hot water, for example, to use the high-temperature hot water flowing from the hot water storage tank as the medium for heating the hot water.

Claims

1. A hot water supply system, comprising: The water inlet passage is capable of guiding hot water supplied from the outside to the inlet of the hot water heating unit; The hot water outlet can guide the hot water that has passed through the hot water heating unit to the hot water supply terminal; The hot water circulation path includes a return flow path that branches off from the middle of the hot water outlet path and connects the middle of the path to the inlet path, and is equipped with a hot water circulation pump that can perform instant hot water operation to circulate the hot water from the hot water outlet path back to the inlet of the hot water heating unit. A flow sensor is installed at a different location in the hot water circulation path than in the return flow path. as well as The control unit determines whether the hot water supply terminal is in an "on" state during the instant hot water operation. The hot water supply system is characterized by... The control unit is capable of performing temporary judgment control and judgment determination control, and is configured as follows: In the aforementioned temporary judgment control, Based on the hot water flow rate detected by the flow sensor during the instant hot water operation, the total flow rate (Qt) is calculated by adding the hot water flow rate in the return flow path to the inlet flow rate entering the inlet path from the outside. Then, the pump speed (N) is controlled to maintain the total flow rate (Qt) at a predetermined first command flow rate (Q1). Furthermore, if the pump speed (N) is lower than a first determination value (N1) during the flow rate control, it is temporarily determined that the hot water supply terminal is in an open state. The determination control is executed after the temporary determination is made. In the determination control, the pump speed (N) is gradually reduced with the goal of making the total flow (Qt) less than the first command flow (Q1) by a second command flow (Q2). If the pump speed (N) is lower than a predetermined second determination value (N2) during its execution, the hot water supply terminal is determined to be in the open state.

2. The hot water supply system according to claim 1, wherein, The hot water heating unit is configured to perform hot water heating when the hot water flow rate in the hot water heating unit is at least a predetermined minimum operating flow rate (MOQ). The second instruction flow (Q2) is set to be greater than or equal to the minimum working flow (MOQ).

3. The hot water supply system according to claim 1, wherein the system comprises: In the determination control, if the pump speed (N) is reduced from a state that is not lower than the second determination value (N2) to a state where the total flow rate (Qt) becomes the second command flow rate (Q2), and the total flow rate (Qt) is less than the predetermined third determination value (Q3), it is determined that the hot water supply terminal is not in the open state.

4. The hot water supply system according to claim 3, wherein, In the determination control, if it is determined that the hot water supply terminal is not in the open state, the temporary determination control is performed again, and when it is performed again, the first determination value (N1) is set to a low speed value compared with the previous temporary determination control.

5. The hot water supply system according to claim 1, wherein, The first determination value (N1) is obtained by subtracting a predetermined threshold (Th) from the predicted value (β) of the pump speed (N) used to maintain the total flow rate (Qt) at the first commanded flow rate (Q1).

6. The hot water supply system according to claim 5, wherein, The predicted value (β) is obtained by learning using exponential smoothing during the instantaneous hot water operation. When the predicted value (β) is on an increasing trend, the learning period is set to a shorter period compared to when it is not.

7. A hot water supply system, comprising: The water inlet passage is capable of guiding hot water supplied from the outside to the inlet of the hot water heating unit; The hot water outlet can guide the hot water that has passed through the hot water heating unit to the hot water supply terminal; The hot water circulation path includes a return flow path that branches off from the middle of the hot water outlet path and connects the middle of the path to the inlet path, and is equipped with a hot water circulation pump that can perform instant hot water operation to circulate the hot water from the hot water outlet path back to the inlet of the hot water heating unit. A flow sensor is installed at a different location in the hot water circulation path than in the return flow path. as well as The control unit determines whether the hot water supply terminal is in an "on" state during the instant hot water operation. The hot water supply system is characterized by... The control unit is capable of performing temporary judgment control and judgment determination control, and is configured as follows: In the aforementioned temporary judgment control, Based on the hot water flow rate detected by the flow sensor during the instant hot water operation, the total flow rate (Qt) is calculated by adding the hot water flow rate in the return flow path to the inlet flow rate entering the inlet path from the outside. Then, the pump speed (N) is controlled to maintain the total flow rate (Qt) at a predetermined first command flow rate (Q1). Furthermore, if the pump speed (N) is lower than a first determination value (N1) during the flow rate control, it is temporarily determined that the hot water supply terminal is in an open state. The determination control is executed after the temporary determination is made. In the determination control, the control that reduces the speed (N) of the pump is executed. And if the total flow rate (Qt) is greater than the specified flow rate even though the speed (N) of the pump is reduced to a specified speed, the determination that the hot water supply terminal is in the open state is made.

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