JP5063486B2 - Heat pump hot water heating system - Google Patents

Description

  The present invention relates to a heat pump hot water heating system in which heat is exchanged between a refrigerant of a heat pump cycle and a hydrothermal medium through a heat exchanger, and the hydrothermal medium is conveyed to an indoor radiator to perform heating.

  In a heating system, also called a heat pump hot water heating system, which generates heat from the heat collected by the heat pump cycle, generates a water heating medium for heating, and sends water to the indoor radiator for heating. In general, a circulating pump driven by an AC power source is used as the conveying unit. Conventionally, this circulation pump is generally operated at a constant head regardless of the number of indoor radiators to be operated and the size of the indoor heating load.

  In the heating system as described above, since the flow rate is set so as to secure the necessary heat dissipation when the indoor heating load is maximum, if the flow rate is higher than necessary when the high-temperature hydrothermal medium is generated, the return water temperature Becomes a high temperature, the refrigerant pressure of the heat pump cycle rises, the life of the heat pump cycle decreases, and in the worst case, the heat pump cycle breaks. Further, when the indoor heating load is small, the amount of heat released from the indoor radiator is reduced, the return water temperature is increased, and the condensation temperature is increased, thereby deteriorating the efficiency of the heat pump cycle. In addition, when the indoor heating load is small, there is a problem that energy is consumed by the circulation pump by flowing the flow rate more than necessary, and the rotation speed of the circulation pump is controlled according to the operating situation, and the appropriate condensation temperature Therefore, it was necessary to secure an appropriate water temperature difference and suppress an increase in the refrigerant pressure.

  As a technique for controlling the number of rotations of the circulation pump and changing the flow rate, for example, there is a technique disclosed in Patent Document 1. In this technique, the number of revolutions of the circulation pump is controlled so that the return water temperature that fluctuates depending on the size of the heat radiation load of the indoor radiator becomes a predetermined temperature, thereby optimizing the exhaust heat recovery.

JP 2002-318007 A

  The technique disclosed in the above-mentioned patent document controls the rotation speed of the circulation pump so that the return water temperature that fluctuates depending on the size of the heat radiation load of the indoor radiator becomes a predetermined temperature, and is applied to a heat pump hot water heating system. In this case, a control technique is required for suppressing the increase of the refrigerant pressure in the heat pump cycle so that the refrigerant pressure becomes a predetermined value or less. Also, when focusing on the efficiency of the heat pump cycle, if the temperature of the generated hydrothermal medium is constant, the rotation speed of the circulation pump should be controlled so that the return water temperature becomes a predetermined temperature as in the above technique. For example, in a heating system that automatically changes the temperature of the generated water heating medium according to the indoor heating load or a system that can be arbitrarily set by an indoor controller, Regardless of the temperature of the heat medium, if the circulation pump rotation speed is controlled so as to be a predetermined return water temperature, for example, if the target return water temperature is too low, the rotation speed of the circulation pump needs to be lowered more than necessary. As a result, the amount of circulating water heat medium to the indoor radiator is reduced, and a necessary amount of heat radiation cannot be secured. Moreover, if the target return water temperature is too high, the efficiency of the heat pump cycle is deteriorated. In addition, there is a problem that wasteful energy is consumed by the circulation pump, and it has been difficult to sufficiently increase the refrigerant pressure in the heat pump cycle and improve the performance of the heat pump hot water heating system.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a heat pump hot water heating system capable of realizing an improvement in the efficiency of the heat pump cycle without incurring a shortage of heat radiation of the indoor radiator due to a decrease in flow rate. And

  In order to solve the above problem, the heat pump hot water heating system of the present invention comprises a circulation pump for exchanging heat between the refrigerant of the heat pump cycle and the hydrothermal medium via the heat exchanger, and conveying the hydrothermal medium to the indoor radiator. In a heat pump hot water heating system comprising: a heat source device having a control unit that controls the head of the circulation pump; and an indoor radiator that is connected to the heat source device and is heated by a water heat medium conveyed from the heat source device. The return water temperature detection detects the difference between the return water temperature, which is the difference between the temperature of the water heat medium (outward water temperature) from the interior to the indoor radiator and the temperature of the water heat medium (return water temperature) returning from the indoor radiator to the heat source unit And the control unit controls the head of the circulation pump so that the difference in the return water temperature is within a predetermined range.

  Further, the control unit is characterized in that the head of the circulation pump is lowered as the return water temperature difference decreases, and the head of the circulation pump is raised as the return water temperature difference increases. That is, when the difference in the return water temperature is less than the lower limit of the return water temperature difference, the head of the circulation pump is lowered, and when the difference in the return water temperature is greater than or equal to the upper limit of the return water temperature difference, the head of the circulation pump is increased. .

  By controlling the head of the circulation pump so that the difference between the return and return temperatures is within a certain range, the efficiency of the heat pump cycle can be improved without causing a shortage of heat from the indoor radiator due to a decrease in flow rate. Can do.

  Embodiments of a heat pump hot water heating system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a system configuration diagram of Embodiment 1 of a heat pump hot water heating system according to the present invention. In FIG. 1, the heat pump hot water heating system of the present embodiment includes a heat pump heat source device 21 that generates a water heat medium used for heating, and an indoor radiator 22 that performs a heating operation using a water heat medium supplied from the heat pump heat source device 21. It is comprised including. The heat pump heat source unit 21 generates a water heat medium used for heating with the heat collected by the heat pump cycle. The heat pump heat source unit 21 includes a buffer tank 5 that stores a water heat medium, a circulation pump 6 that serves as a water supply unit that circulates the water heat medium in the buffer tank 5, and the water heat medium via the refrigerant-water heat exchanger 4. It comprises a heat pump cycle 11 for heating.

  The heat pump cycle 11 includes a heat source side heat exchanger 2 that collects heat from outdoor air, a compressor 3 that compresses a refrigerant that circulates in the heat pump cycle 11 and conveys heat, and a refrigerant flow rate adjustment that adjusts the flow rate of the refrigerant. It is a heat medium circulation closed circuit comprised with the valve 10 and the primary flow path of the refrigerant | coolant-water heat exchanger 4 which performs heat exchange of a refrigerant | coolant and a water heat medium. The refrigerant of the heat pump cycle 11 and the hydrothermal medium of the indoor radiator circulation cycle are independent of each other and are not thermally mixed but are thermally connected by the refrigerant-water heat exchanger 4. The heat pump heat source unit 21 having the above configuration is housed in a single casing and installed outside the room.

  The buffer tank 5 is provided with a forward connection port 5a and a return connection port 5b. The forward connection port 5a is connected to the suction side of the circulation pump 6, and the return connection port 5b is a heat pump. A return side pipe from the indoor radiator 22 that performs the heating operation by the water heat medium supplied from the heat source unit 21 is connected. On the discharge side of the circulation pump 6, an inlet side (return pipe side connection port) 4 a of the secondary flow path of the refrigerant-water heat exchanger 4 for heat collection is pipe-connected, and an outlet side of the refrigerant-water heat exchanger 4. The forward piping to the indoor radiator 22 is connected to the (forward piping side connection port) 4b. An outgoing water temperature detection unit 7 that detects the temperature of the water heating medium at the outlet of the refrigerant-water heat exchanger 4 is provided in the outgoing piping to the indoor radiator 22. In addition, a return water temperature detection unit 8 that detects a return water temperature from the indoor radiator 22 is provided in the return side pipe from the indoor radiator 22. The forward water temperature detection unit 7 and the return water temperature detection unit 8 are the temperature of the water heat medium (forward water temperature) from the heat pump heat source unit 21 toward the indoor radiator 22 and the water heat that returns from the indoor radiator 22 to the heat pump heat source unit 21. A forward / backward water temperature detection unit that detects a forward / backward water temperature difference that is a difference from the temperature of the medium (return water temperature) is configured.

  The control unit 9 is mainly composed of a microcomputer, and controls the circulation pump 6, the compressor 3, the heat source side blower fan 1 that collects the heat of the outdoor air, and the like. The circulation pump 6 has an impeller. By rotating the impeller, the water heat medium in the circulation circuit is forcibly circulated, and the water heat medium is circulated through the indoor radiator 22. In the present embodiment, the circulation pump 6 is a pump that includes a motor that is PWM-controlled by the control unit 9 and that is driven by a DC power source that can arbitrarily change the rotation speed of the impeller by a speed command voltage.

  While the heat pump heat source unit 21 is installed outside the room, one or more indoor radiators 22 and a controller 23 are provided in the room. The indoor radiator 22 performs a heating operation with a hydrothermal medium supplied from the heat pump heat source unit 21. The indoor radiator 22 is, for example, a floor heating panel that is installed under the floor and performs radiant heating, a panel heater that is installed on the indoor wall surface and performs radiant heating, a blower for circulating indoor air, a heat exchanger that performs indoor air and a water heat medium Equipped with a fan convector that heats by forced convection.

  The controller 23 includes a room temperature detecting means (not shown) for detecting the room temperature, a room temperature setting means (not shown) for setting the target room temperature, and a hydrothermal medium temperature setting means for setting the temperature of the hydrothermal medium. (Not shown). The water heating medium temperature setting means operates at a high water temperature when the heating load is high, depending on the set temperature and the heating load estimated from the current room temperature. When the load is small, a water temperature automatic operation switching means for automatically changing the water temperature is configured so as to operate at a low water temperature.

  The control unit 9 is installed so as to be capable of bidirectional communication with the controller 23 installed in the room, and the controller 23 sets the set room temperature, the current room temperature, the set water temperature information, and the outlet of the refrigerant-water heat exchanger 4. The output of the return water temperature detection unit 7 for detecting the temperature of the water heat medium and the return water temperature detection unit 8 for detecting the return water temperature from the indoor radiator 22 are the circulation pump 6 and the compressor 3 of the heat pump heat source device 21 and the heat source side ventilation. It is taken in as control information for controlling the fan 1 and the like.

  Next, the operation of the heat pump heating system will be described. FIG. 2 is a flowchart showing the control operation of the heat pump hot water heating system of the present embodiment. In FIG. 2, first, when any of the controllers 23 of the indoor radiator 22 is operated to start operation in step S <b> 1, the operation start information, the set room temperature, the current temperature are sent from the controller 23 to the control unit 9 of the heat pump heat source unit 21. Room temperature and set water temperature information (arbitrary water temperature set by the controller 23 in the case of the water temperature fixed operation, information that the water temperature automatic operation is selected in the water temperature automatic operation) is transmitted.

  Next, in step S2, the control unit 9 gives a speed command voltage so that the circulation pump 6 operates at the initial rotational speed stored in advance in the control unit 9, and performs a heat pump cycle so that the outgoing water temperature becomes the target water temperature. Control. The target water temperature is the water temperature set by the controller 23 when the water temperature is fixed, the set room temperature when the water temperature is automatic, and the water temperature calculated from the current room temperature information. Note that the initial rotational speed is not constant and may be varied according to the target outgoing water temperature.

  Next, in step S <b> 3, the outgoing water temperature detection unit 7 detects the outgoing water temperature. Next, in step S <b> 4, the return water temperature detection unit 8 detects the return water temperature and stores the detected return water temperature in the microcomputer of the control unit 9.

  Next, in step S5, it is determined whether or not the return water temperature difference (ΔTa) (forward water temperature−return water temperature) is equal to or greater than the return water temperature difference lower limit 4 ° C. (ΔTaL). If the return water temperature difference ΔTa is less than the return water temperature difference lower limit 4 ° C. (ΔTaL), the process proceeds to step S8, and a process of lowering the rotational speed of the circulation pump 6 by 300 rpm, that is, a process of lowering the head of the circulation pump 6 is performed. After that, the process proceeds to step S10, and the current rotational speed is maintained for 3 minutes (step S7), and after 3 minutes, the process returns to step S3. Here, the lower limit of the return water temperature difference 4 ° C. (ΔTaL) is the minimum temperature difference necessary to improve the efficiency of the heat pump.

  On the other hand, if it is determined in step S5 that the return water temperature difference (ΔTa) is equal to or larger than the return water temperature difference lower limit 4 ° C. (ΔTaL), the process proceeds to step S6, where the return water temperature difference (ΔTa) is the upper limit of the return water temperature difference. It is judged whether it is 20 ° C. (ΔTaH) or less. If the return water temperature difference (ΔTa) exceeds the return water temperature difference upper limit 20 ° C. (ΔTaH), the process proceeds to step S9, and the process of increasing the rotational speed of the circulation pump 6 by 300 rpm, that is, the process of increasing the head of the circulation pump 6 Then, the process proceeds to step S10, and the current rotational speed is maintained for 3 minutes (step S7). After 3 minutes, the process returns to step S3.

  If it is determined in step S6 that the return water temperature difference (ΔTa) is equal to or less than the return water temperature difference upper limit 20 ° C. (ΔTaH), the process proceeds to step S7, and the current rotational speed of the circulation pump 6 is maintained. The process returns to step S3 after 3 minutes. Here, the upper limit of the return water temperature difference 20 ° C. (ΔTaH) is the maximum temperature difference that can be tolerated in order that the indoor radiator 22 does not have a shortage of heat dissipation due to a decrease in flow rate.

  The lower limit of the return water temperature difference 4 ° C. (ΔTaL) and the upper limit of the return water temperature difference 20 ° C. (ΔTaH) are determined by the heat dissipation characteristics of the indoor radiator 22, and the above values are different for various types of indoor radiators 22. However, when the type of indoor radiator 22 to be used is limited, an optimal value may be set according to the heat dissipation characteristics of the indoor radiator 22.

  The time for maintaining the rotation speed of the circulation pump 6 in step S7 is 3 minutes, and the variable rotation speed in steps S8 and S9 is 300 rpm. However, the rotation speed variable amount of the circulation pump 6 and the current rotation speed are maintained. If the rotational speed variable amount of the circulation pump 6 is increased, it takes time to stabilize the heat pump cycle and the return water temperature. Therefore, the time for maintaining the current rotational speed is lengthened, and the rotational speed variable amount of the circulation pump 6 is decreased. For example, since it does not take time to stabilize the heat pump cycle and the return water temperature, the time for maintaining the current rotational speed may be shortened.

  As described above, in the heat pump hot water heating system of the present embodiment, the control unit 9 controls the number of rotations of the circulation pump 6 so that the temperature difference between the return and return temperatures is within a certain range. The efficiency improvement of the heat pump cycle can be realized without causing a shortage of heat radiation of the indoor radiator 22 due to a decrease in the flow rate.

Embodiment 2. FIG.
Although the present embodiment is the same in configuration and control flow of the heat pump hot water heating system as in the first embodiment, the return water temperature difference lower limit (ΔTaL) and the return water temperature difference upper limit (ΔTaH) in the first embodiment are set to the forward water temperature. It is set according to. FIG. 3 shows the relationship between the incoming water temperature and the appropriate water temperature difference. As shown in FIG. 3, the appropriate water temperature difference is proportional to the incoming water temperature. And with respect to the appropriate water temperature difference, the return water temperature difference lower limit (ΔTaL) is set to a value of an appropriate water temperature difference of −1 ° C., and the return water temperature difference upper limit (ΔTaH) is set to a value of an appropriate water temperature difference of + 1 ° C.

  In this way, by providing a temperature range of 2 ° C. between the return water temperature difference lower limit (ΔTaL) and the return water temperature difference upper limit (ΔTaH), it becomes possible to stabilize the control convergence of the heat pump hot water heat source machine. .

  Although the temperature difference between the return water temperature difference lower limit (ΔTaL) and the return water temperature difference upper limit (ΔTaH) is 2 ° C., the temperature difference between the return water temperature difference lower limit (ΔTaL) and the return water temperature difference upper limit (ΔTaH) is The larger the control convergence of the heat pump hot water heat source machine, the higher the control convergence of the heat pump hot water heat source machine. In addition, when the control convergence of the heat pump hot water heat source device is fast, the temperature difference between the return water temperature difference lower limit (ΔTaL) and the return water temperature difference upper limit (ΔTaH) may be reduced.

  The appropriate water temperature difference is obtained from the heat dissipation characteristics of the indoor radiator 22 and is a water temperature difference when a rated flow rate is passed through the indoor radiator 22. That is, when the outgoing water temperature is high, the amount of heat dissipation in the indoor radiator 22 is large, so the appropriate water temperature difference is large, and when the outgoing water temperature is low, the amount of heat dissipation in the indoor radiator 22 is small, so the appropriate water temperature difference is small. In the case of the floor heating panel, as shown in FIG. 3, when the outgoing water temperature is 60 ° C., the appropriate water temperature difference is 10 ° C., and when the outgoing water temperature is 40 ° C., the appropriate water temperature difference is 6 ° C.

  In addition, the control part 9 is comprised so that it can set arbitrary appropriate water temperature differences, and when using it in combination with the indoor radiator 22 whose heat dissipation characteristic is unknown, it sets arbitrary appropriate water temperature differences. Thus, combinations with various indoor radiators 22 are possible.

  Note that if the flow rate is higher than necessary when generating high-temperature water, the return water temperature becomes high, the refrigerant condensing temperature rises, and the refrigerant becomes high pressure.Therefore, it is necessary to lower the return water temperature and ensure an appropriate water temperature difference. is there. That is, it is necessary to ensure a water temperature difference that satisfies the pressure-resistant life of the refrigerant circuit with respect to the refrigerant pressure repeatedly applied to the heat pump cycle. The appropriate water temperature difference of 10 ° C. when the outgoing water temperature is 60 ° C. is a water temperature difference that enables operation satisfying the pressure-resistant life of the refrigerant circuit.

  As described above, by setting the target return temperature difference according to the going water temperature, and controlling the rotational speed of the circulation pump 6 so as to be the target return temperature difference, the indoor radiator 22 It is possible to ensure an optimal back and forth temperature difference according to the heat dissipation characteristics. As a result, the efficiency of the heat pump cycle can be improved over that of the first embodiment. In addition, it is possible to extend the life of the equipment by suppressing the increase in the refrigerant pressure in the heat pump cycle.

Embodiment 3 FIG.
Although the present embodiment is the same as the first embodiment in the configuration and control flow of the heat pump hot water heating system, the variable number of rotations in steps S8 and S9 of the control flow in the first embodiment is stored in the control unit 9. It is made variable by a return water temperature change amount (ΔTb) (previous time return water temperature−current return water temperature) which is a difference between the previous time return water temperature and the current return water temperature.

  As shown in FIG. 4, the variable amount of rotation speed of the present embodiment increases the rotation speed change amount as ΔTb decreases when processing for decreasing the rotation speed of the circulation pump 6 is performed. The variable amount of rotation of the circulating pump 6 when the current return water temperature falls below 2 ° C. with respect to the previous time return water temperature (ΔTb> 2), such as when the number of indoor radiators 22 is increased, is −100 rpm. When the change in the current return water temperature is within 2 ° C. (2 ≧ ΔTb ≧ −2) with respect to the previous time return water temperature, such as when there is no change in the number of operating indoor radiators 22, the rotational speed variable amount of the circulation pump 6 is -300 rpm, when the number of operating indoor radiators 22 is decreased, etc. When the current return water temperature rises by more than 2 ° C. relative to the previous time return water temperature (ΔTb <−2), the rotation speed of the circulation pump 6 is variable. The amount is -500 rpm.

  On the contrary, when the process of increasing the rotation speed of the circulation pump 6 is performed, the rotation speed change amount is increased as the return water temperature change amount (ΔTb) is larger. When the number of operating indoor radiators 22 is increased or the like, when the current return water temperature falls below 2 ° C. relative to the previous time return water temperature (ΔTb> 2), the rotation speed variable amount of the circulation pump 6 is +500 rpm, If the change in the current return water temperature is within 2 ° C. (2 ≧ ΔTb ≧ −2) with respect to the previous time return water temperature, such as when there is no change in the number of indoor radiators 22 operating, the rotation speed variable amount of the circulation pump 6 is +300 rpm. And the variable amount of rotation of the circulating pump 6 when the current return water temperature exceeds 2 ° C. with respect to the previous time return water temperature (ΔTb <−2), such as when the number of operating indoor radiators 22 decreases. +100 rpm.

  Although an example of the above-described rotation speed variable amount has been shown, an optimal value for the rotation speed variable amount may be selected according to the rotation speed and flow rate characteristics of the circulation pump 6.

  As described above, in the heat pump hot water heating system of the present embodiment, the rotation speed variable amount is determined by the return water temperature change amount (ΔTb) that is the difference between the previous time return water temperature stored in the control unit 9 and the current return water temperature. As a result, the followability to a sudden load fluctuation due to a change in the number of operating units of the indoor radiator 22 or the like is improved.

Embodiment 4 FIG.
The configuration of the heat pump hot water heating system of the present embodiment is the same as that of the first embodiment. However, in step S5 of the control flow of the first embodiment, the return water temperature difference (ΔTa) is the lower limit of the return water temperature difference (ΔTaL). In this case, a process for confirming whether or not the target outgoing water temperature is secured (whether the target outgoing water temperature has been reached) in step S11 is added.

  If the target outgoing water temperature is not ensured in step S11, the process proceeds to step S8, a process for lowering the rotational speed of the circulation pump 6 by 300 rpm is performed, then the process proceeds to step S10, and after 3 minutes, the process returns to step S3.

  When the target outgoing water temperature is secured in step S11, the process proceeds to step S6, and thereafter the same processing as in the first embodiment is performed.

  As described above, in the heat pump hot water heating system according to the present embodiment, when the target outgoing water temperature is not secured, the heat pump hot water heating system is When the number of operating radiators 22 increases, the flow rate increases, and when the outgoing water temperature decreases, the rising of the outgoing water temperature can be accelerated.

Embodiment 5 FIG.
The configuration of the heat pump hot water heating system of the present embodiment is the same as that of the first embodiment. However, in step S11 of the control flow of the fourth embodiment, when the target outgoing water temperature is not ensured, the defrosting operation of step S12 is performed. This is a process to check whether it is inside.

  If the defrosting operation is being performed in step S12, the process proceeds to step S7, where the rotational speed of the circulation pump 6 is maintained, and thereafter the same processing as in the fourth embodiment is performed.

  If the defrosting operation is not being performed in step S12, the process proceeds to step S8 to perform a process for lowering the rotational speed of the circulation pump 6 by 300 rpm, and thereafter the same process as in the fourth embodiment is performed.

  The defrosting operation is performed in order to prevent the heating capacity from being reduced by frost adhering to the heat source side heat exchanger 2, and the heat pump cycle is switched to the cooling operation and the frost is melted by the heat of the water heat medium. . Therefore, the temperature of the hydrothermal medium is temporarily lowered by performing the defrosting operation.

  Whether or not the defrosting operation is in progress is determined even if the defrosting operation is finished, it is desirable to maintain the current rotational speed for the time until the water temperature rises to the target forward water temperature. It is determined that the defrosting operation is in progress for a minute.

  As described above, in the heat pump hot water heating system of the present embodiment, during the defrosting operation, by maintaining the rotation speed of the circulation pump 6 without changing, unnecessary rotation due to the water temperature change due to the defrosting operation. It becomes possible to eliminate the number change.

  As described above, the present invention is a heat pump hot water heating system including a heat source device having a circulation pump that exchanges heat between a refrigerant of a heat pump cycle and a hydrothermal medium via a heat exchanger and conveys the hydrothermal medium to an indoor radiator. It is useful for the system.

It is a system configuration figure of Embodiment 1 of the heat pump hot water heating system concerning the present invention. 3 is a flowchart showing a control operation of the first embodiment. It is a figure which shows the relationship between the going water temperature of Embodiment 2, and appropriate water temperature. It is a figure which shows the rotation speed variable amount of the circulation pump of Embodiment 3. 10 is a flowchart illustrating a control operation according to the fourth embodiment. 10 is a flowchart illustrating a control operation according to the fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat source side ventilation fan 2 Heat source side heat exchanger 3 Compressor 4 Refrigerant-water heat exchanger 4a Inlet side (return piping side connection port)
4b Outlet side (outward piping side connection port)
5 Buffer tank 5a Outward side connection port 5b Return side connection port 6 Circulating pump 7 Outward water temperature detection part (forward return water temperature detection part)
8 Return water temperature detector (Return water temperature detector)
9 Control Unit 10 Refrigerant Flow Rate Control Valve 11 Heat Pump Cycle 21 Heat Pump Heat Source Machine (Heat Source Machine)
22 Indoor radiator 23 Controller

Claims (9)

A heat source device that exchanges heat between the refrigerant of the heat pump cycle and the hydrothermal medium via a heat exchanger, and an indoor radiator that is connected to the heat source machine and that is heated by the hydrothermal medium conveyed from the heat source machine In the heat pump hot water heating system,
A circulation pump for circulating the water heating medium between the heat exchanger and the indoor radiator;
Forward / return water temperature difference which is a difference between the temperature of the water heat medium (forward water temperature) from the heat source unit toward the indoor radiator and the temperature of the water heat medium (return water temperature) from the indoor radiator to the heat source unit A return water temperature detector for detecting
A heat pump hot water heating system comprising: a control unit that controls a head of the circulation pump so that the difference in the return water temperature falls within a predetermined range in accordance with a detection value of the return water temperature detection unit. system. The said control part lowers the head of the said circulation pump with the reduction | decrease of the said return water temperature difference, and raises the head of the said circulation pump with the increase of the said return water temperature difference. Heat pump hot water heating system. The control unit lowers the head of the circulation pump when the difference in the return water temperature is less than the lower limit of the return water temperature difference, and reduces the head of the circulation pump when the difference in the return water temperature is equal to or higher than the upper limit of the return water temperature difference. The heat pump hot water heating system according to claim 2, wherein the heat pump is heated. The heat pump hot water heating system according to claim 1, wherein the control unit changes a target return temperature difference according to a hydrothermal medium temperature. The control unit increases the target return water temperature difference when the outgoing water temperature is high, and reduces the target return water temperature difference when the outgoing water temperature is low, according to the hydrothermal medium temperature. The heat pump hot water heating system according to claim 4. The control unit changes the return water temperature difference lower limit and the return water temperature difference upper limit based on an appropriate water temperature difference proportional to the forward water temperature, and sets a value obtained by subtracting a predetermined value from the appropriate water temperature difference as the forward water temperature difference lower limit. The heat pump hot water heating system according to claim 5, wherein a value obtained by adding a predetermined value to the appropriate water temperature difference is set as the upper limit of the return water temperature difference. When performing the process of reducing the rotation speed of the circulation pump, the control unit increases the rotation speed change amount as the return water temperature change amount is smaller, and performs the process of increasing the rotation speed of the circulation pump. The heat pump hot water heating system according to claim 1, wherein the rotational speed change amount is increased as the change amount is larger. 2. The heat pump hot water heating system according to claim 1, wherein when the temperature of the hydrothermal medium does not reach a target, the control unit reduces the rotational speed of the circulation pump. The said control part does not change the rotation speed of the said circulation pump, even when the temperature of the said hydrothermal medium has not reached the target, during the defrost operation of the said heat pump cycle. The heat pump hot water heating system according to claim 1.

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