Hot water heating device

Abstract

It is configured such that, when at least one of water temperatures (Twi) of first to third indoor terminal units (4i (i = a to c)) where operation stops is equal to or less than a predetermined water temperature (Tw2) or when room temperatures (Tki) of first to third rooms (3i) are equal to or less than a predetermined room temperature (Tks) at the time when an outdoor air temperature (To) has become equal to or less than a predetermined temperature (Tos), an indoor opening / closing valve (12i) of the relevant indoor terminal unit (4i) performs opening operation.

Description

Technical Field

[0001] The present invention relates to a hot water heating device preventing freezing of a water circulation circuit making water flow to a plurality of indoor terminal units in a cold season.Background Art

[0002] There is a hot water heating device performing heating by making water heated by a heat source unit flow to a plurality of indoor terminal units installed in a plurality of rooms. The hot water heating device has a risk that, when there is an indoor terminal unit where operation stops, water in a pipe of a water circulation circuit, which is a path through which water flows to the indoor terminal unit, is frozen in a cold season.

[0003] The hot water heating device of PTL 1 has a water circulation circuit where a heat source unit heating water, a pump, and a plurality of indoor terminal units and opening / closing valves connected in parallel to the heat source unit are connected by a pipe. In PTL 1 above, when the outdoor air temperature becomes equal to or less than the predetermined temperature (e.g., 3°C) during stop of heating operation of all of the indoor terminal units, the pump is operated and one opening / closing valve or two or more opening / closing valves of all of the indoor terminal units are opened at a time in turn to thereby make water flow throughout the water circulation circuit and prevent the water in the pipe of the water circulation circuit from freezing.Citation ListPatent Literature

[0004] PTL 1: JP 2003-240381 ASummary of InventionTechnical Problem

[0005] The hot water heating device of PTL 1 is configured such that, when the outdoor air temperature becomes equal to or less than the predetermined temperature, water is made to flow to all of the indoor terminal units to prevent freezing, and therefore low temperature water flows also to the indoor terminal unit, which is installed in a room where the room temperature is such that people do not feel cold. When the low temperature water flows to the indoor terminal unit in such a room, the room temperature of the room decreases, which pose a risk that the room temperature becomes such a room temperature that people feel cold.

[0006] Thus, the present invention has been made to solve such a problem. It is an object of the present invention to provide a hot-water heating device preventing freezing of the water circulation circuit when the outdoor air temperature has become equal to or less than the predetermined temperature and suppressing a decrease in the room temperature of the room where the room temperature is such that people do not feel cold.Solution to Problem

[0007] One aspect of the invention is a hot water heating device including: a water circulation circuit where a heat source unit configured to heat water, a pump, and a plurality of indoor terminal units and a plurality of opening / closing valves connected in parallel to the heat source unit are connected by a pipe and where water circulates between the plurality of indoor terminal units and the heat source unit; an outdoor air temperature detection means configured to detect the outdoor air temperature; a plurality of terminal unit water temperature detection means configured to detect the terminal unit water temperature, the terminal unit water temperature being the temperature of water flowing through each of the plurality of indoor terminal units; a plurality of room temperature detection means configured to detect the room temperature of a room where each of the plurality of indoor terminal units is installed; and a freeze prevention control means configured to perform freeze prevention control by opening the opening / closing valve corresponding to the indoor terminal unit where operation stops by closing the corresponding opening / closing valve to make water flow to the indoor terminal unit; in which the freeze prevention control means is configured such that, when the outdoor air temperature is equal to or less than the predetermined temperature, the freeze prevention control means performs the freeze prevention control to the opening / closing valve corresponding to the indoor terminal unit satisfying at least one of states in which the terminal unit water temperature of water flowing through the indoor terminal unit is equal to or less than a first water temperature and in which the room temperature of the room where the indoor terminal unit is installed is equal to or less than the predetermined temperature among the indoor terminal units where the operation stops.Advantageous Effects of Invention

[0008] The hot-water heating device of the present invention can prevent freezing of the water circulation circuit when the outdoor air temperature has become equal to or less than the predetermined temperature and can suppress a decrease in the room temperature of the room where the temperature is such that people do not feel cold.Brief Description of Drawings

[0009] FIG. 1 is a circuit diagram illustrating a heat pump-type hot-water heating device according to the present invention; FIG. 2 is a flowchart showing the main routine of freeze prevention control performed by the heat pump-type hot-water heating device according to the present invention; FIG. 3 is a flowchart showing specific operation of freeze prevention specification processing in the flowchart in FIG. 2; and FIG. 4 is a flowchart showing specific operation of indoor opening / closing valve control processing in the flowchart in FIG. 3. Description of Embodiments

[0010] Next, embodiments according to the present invention are described with reference to the drawings. The embodiments described below exemplify devices or methods for embodying the technical idea of the present invention. The technical idea of the present invention does not specify the materials, shapes, structures, arrangement, and the like of constituent components to the materials, shapes, structures, arrangement, and the like described below. The technical idea of the present invention can be variously altered in the technical scope defined by claims.[Heat pump-type hot-water heating device]

[0011] FIG. 1 is a circuit diagram illustrating a heat pump-type hot-water heating device 1 of a first embodiment according to the present invention.

[0012] The heat pump-type hot-water heating device 1 includes an outdoor unit 2 and a plurality of indoor terminal units 4a, 4b, 4c (referred to as a first indoor terminal unit 4a, a second indoor terminal unit 4b, a third indoor terminal unit 4c) installed in a plurality of rooms 3a, 3b, 3c (referred to as a first room 3a, a second room 3b, a third room 3c), respectively.

[0013] The outdoor unit 2 includes a refrigerant circuit 10 formed by sequentially connecting a compressor 5, a four-way valve 6, a water-refrigerant heat exchanger 7 exchanging heat between water and a refrigerant, an expansion valve 8, and an outdoor heat exchanger 9 by a pipe. The outdoor unit 2 further includes a pump 15 and a fourth water temperature sensor 21 described later. The water-refrigerant heat exchanger 7 corresponds to the heat source unit of the present invention.

[0014] The first indoor terminal unit 4a has a first indoor opening / closing valve 12a and a first indoor heat exchanger 13a. The pump 15, the water-refrigerant heat exchanger 7, the first indoor opening / closing valve 12a, and the first indoor heat exchanger 13a are sequentially connected by a pipe, forming a first water circulation circuit 16. The first indoor terminal unit 4a further has a first room temperature sensor 19a and a first water temperature sensor 20a. The first room temperature sensor 19a detects the room temperature of the first room 3a. The first water temperature sensor 20a is arranged between the pump 15 and the first indoor heat exchanger 13a of the first water circulation circuit 16 and detects the temperature of water that has passed through the first indoor heat exchanger 13a.

[0015] The second indoor terminal unit 4b has a second indoor opening / closing valve 12b and a second indoor heat exchanger 13b. One end of a pipe is connected to the first water circulation circuit 16 between the water-refrigerant heat exchanger 7 and the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the other end of the pipe is connected to the first water circulation circuit 16 between the pump 15 and the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and the second indoor opening / closing valve 12b and the second indoor heat exchanger 13b are connected in series between the one end and the other end of the pipe. This forms a second water circulation circuit 17 where the pump 15, the water-refrigerant heat exchanger 7, the second indoor opening / closing valve 12b, and the second indoor heat exchanger 13b are sequentially connected by the pipe. The second indoor terminal unit 4b further has a second room temperature sensor 19b and a second water temperature sensor 20b. The second room temperature sensor 19b detects the room temperature of the second room 3b. The second water temperature sensor 20b is arranged between the pump 15 and the second indoor heat exchanger 13b of the second water circulation circuit 17 and detects the temperature of water that has passed through the second indoor heat exchanger 13b.

[0016] The third indoor terminal unit 4c has a third indoor opening / closing valve 12c and a third indoor heat exchanger 13c. One end of a pipe is connected to the first water circulation circuit 16 between the water-refrigerant heat exchanger 7 and the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the other end of the pipe is connected to the first water circulation circuit 16 between the pump 15 and the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and the third indoor opening / closing valve 12c and the third indoor heat exchanger 13c are connected in series between the one end and the other end of the pipe. This forms the third water circulation circuit 18 where the pump 15, the water-refrigerant heat exchanger 7, the third indoor opening / closing valve 12c, and the third indoor heat exchanger 13c are sequentially connected by the pipe. The third indoor terminal unit 4c further has a third room temperature sensor 19c and a third water temperature sensor 20c. The third room temperature sensor 19c detects the room temperature of the third room 3c. The third water temperature sensor 20c is arranged between the pump 15 and the third indoor heat exchanger 13c of the third water circulation circuit 18 and detects the temperature that has passed through the third indoor heat exchanger 13c.

[0017] Thus, the first indoor terminal unit 4a and the first indoor opening / closing valve 12a connected to the first water circulation circuit 16, the second indoor terminal unit 4b and the second indoor opening / closing valve 12b connected to the second water circulation circuit 17, and the third indoor terminal unit 4c and the third indoor opening / closing valve 12c connected to the third water circulation circuit 18 are connected in parallel to the water-refrigerant heat exchanger 7.

[0018] Further, between the water-refrigerant heat exchanger 7 and the first indoor opening / closing valve 12a of the first water circulation circuit 16, the fourth water temperature sensor 21 is arranged which detects the temperature of water before diverting to the second water circulation circuit 17 and the third water circulation circuit 18 through the water-refrigerant heat exchanger 7. Outside the rooms, an outdoor air temperature sensor 22 detecting the outdoor air temperature is arranged.

[0019] The first indoor terminal unit 4a to the third indoor terminal unit 4c correspond to the indoor terminal units of the present invention. The first water circulation circuit 16 to the third water circulation circuit 18 correspond to the water circulation circuits of the present invention. The first room temperature sensor 19a to the third room temperature sensor 19c correspond to the room temperature detection means of the present invention. The first water temperature sensor 20a to the third water temperature sensor 20c correspond to the terminal unit water temperature detection means of the present invention. The fourth water temperature sensor 21 corresponds to the heat source unit water temperature detection means of the present invention. The outdoor air temperature sensor 22 corresponds to the outdoor air temperature detection means of the present invention.

[0020] When the first indoor opening / closing valve 12a of the first indoor terminal unit 4a is opened and the pump 15 is driven, water circulates through the first water circulation circuit 16, the water is supplied to the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and the water returns from the first indoor heat exchanger 13a to the water-refrigerant heat exchanger 7. Similarly, when the second indoor opening / closing valve 12b of the second indoor terminal unit 4b is opened and the pump 15 is driven, water circulates through the second water circulation circuit 17, the water is supplied to the second indoor heat exchanger 13b of the second indoor terminal unit 4b, and the water returns from the second indoor heat exchanger 13b to the water-refrigerant heat exchanger 7. Similarly, when the third indoor opening / closing valve 12c of the third indoor terminal unit 4c is opened and the pump 15 is driven, water circulates through the third water circulation circuit 18, the water is supplied to the third indoor heat exchanger 13c of the third indoor terminal unit 4c, and the water returns from the third indoor heat exchanger 13c to the water-refrigerant heat exchanger 7.

[0021] When the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the second indoor opening / closing valve 12b of the second indoor terminal unit 4b, and the third indoor opening / closing valve 12c of the third indoor terminal unit 4c are all opened and the pump 15 is driven, water circulates through all of the first water circulation circuit 16, the second water circulation circuit 17, and the third water circulation circuit 18, the water is supplied in parallel to the first indoor heat exchanger 13a of the first indoor terminal unit 4a, the second indoor heat exchanger 13b of the second indoor terminal unit 4b, and the third indoor heat exchanger 13c of the third indoor terminal unit 4c, and the water returns from the first indoor heat exchanger 13a to the third indoor heat exchanger 13c to the water-refrigerant heat exchanger 7.

[0022] The heat pump-type hot-water heating device 1 of this embodiment has a control means 25 controlling each device. More specifically, the control means 25 performs various kinds of control related to the operation of the heat pump-type hot-water heating device 1, such as drive control of the compressor 5, switching control of the four-way valve 6, opening degree control of the expansion valve 8, drive control of the pump 15, and opening / closing control of the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c, based on the detected values detected by the first room temperature sensor 19a to the third room temperature sensor 19c, the first water temperature sensor 20a to the third water temperature sensor 20c, the fourth water temperature sensor 21, and the outdoor air temperature sensor 22. The control means 25 further includes a timer unit measuring time and a storage unit storing a control program of the heat pump-type hot-water heating device 1.

[0023] The control means 25 of the heat pump-type hot-water heating device 1 of this embodiment has a freeze prevention control means 26 as illustrated in FIG. 1. The freeze prevention control means 26 can be realized by software as a function of the control means 25.

[0024] The heat pump-type hot-water heating device 1 of this embodiment is configured such that freeze prevention control is automatically started during stop of the heating operation of the outdoor unit 2, the first indoor terminal unit 4a installed in the first room 3a, the second indoor terminal unit 4b installed in the second room 3b, and the third indoor terminal unit 4c installed in the third room 3c. The first indoor opening / closing valve 12a of the first indoor terminal unit 4a where the heating operation stops, the second indoor terminal unit 4b where the heating operation stops, and the third indoor opening / closing valve 12 of the third indoor terminal unit 4c where the heating operation stops are brought into a closed state.[Freeze prevention control]

[0025] Next, the freeze prevention control performed by the freeze prevention control means 26 in the heat pump-type hot-water heating device 1 of this embodiment is described with reference to FIGS. 2 to 4. FIG. 2 illustrates the main routine of the freeze prevention control. FIG. 3 illustrates indoor terminal unit specification processing included in the main routine in FIG. 2. FIG. 4 illustrates indoor opening / closing valve control processing included in the indoor terminal unit specification processing in FIG. 3.

[0026] First, in Step ST1 in FIG. 2, it is determined whether stop time (pump stop time) PT of the pump 15 is equal to or more than a first set time PTs (e.g., 3 hours). Herein, the first set time PTs is set to time during which water in the water circulation circuit is supposed not to freeze without the freeze prevention control. In this determination, when the pump stop time PT is equal to or more than the first set time PTs (Step ST1 : YES), the process proceeds to Step ST2, and when the pump stop time PT falls below the first set time PTs (Step ST1: NO), Step ST1 is repeated. In Step ST2, an outdoor air temperature To detected by the outdoor air temperature sensor 22 is read.

[0027] Then, in Step ST3, it is determined whether the outdoor air temperature To is equal to or less than a predetermined temperature Tos (e.g., 5°C). Herein, the predetermined temperature Tos is set to a temperature at which water in the water circulation circuit is supposed not to freeze. In this determination, when the outdoor air temperature To is equal to or less than the predetermined temperature Tos (Step ST3: YES), the process proceeds to Step ST4, and when the outdoor air temperature To exceeds the predetermined temperature Tos (Step ST3: NO), the process proceeds to Step ST1. In Step ST4, the drive of the pump 15 is started.

[0028] Then, in Step ST5, opening operation of the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the second indoor opening / closing valve 12b of the second indoor terminal unit 4b, and the third indoor opening / closing valve 12c of the third indoor terminal unit 4c is performed.

[0029] Then, in Step ST6, it is determined whether a second set time Nv1 (e.g., 15 minutes) has elapsed from the opening operation of the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c. Herein, the second set time Nv1 is set to time sufficient for solving a local temperature decrease in the water circulation circuit. The second set time Nv1 corresponds to the predetermined time during which the freeze prevention control means opens the opening / closing valves of all of the indoor terminal units and performs the drive control of the pump before performing the freeze prevention control in the present invention.

[0030] When the second set time Nv1 has elapsed (Step ST6: YES), the process proceeds to Step ST7, and when the second set time Nv1 has not elapsed (Step ST6: NO), ST6 is repeated. In Step ST7, closing operation of the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c is performed.

[0031] Then, in Step ST8, a water temperature Twa detected by the first water temperature sensor 20a, a water temperature Twb detected by the second water temperature sensor 20b, and a water temperature Twc detected by the third water temperature sensor 20c are read. Then, in Step ST9, a water temperature Twd detected by the fourth water temperature sensor 21 is read. The water temperature Twa, the water temperature Twb, and the water temperature Twc correspond to the terminal unit water temperature of the present invention and the water temperature Twd corresponds to the heat source unit water temperature of the present invention.

[0032] Then, in Step ST10, it is determined whether at least one of the water temperature Twa, the water temperature Twb, the water temperature Twc, and the water temperature Twd is equal to or less than a predetermined water temperature Tw1. Herein, the predetermined water temperature Tw1 is a temperature determined by considering a possibility that water freezes, and is set to 0°C, which is the freezing point of water, for example. The predetermined water temperature Tw1 may also be set to 2°C with a margin, in which the possibility that water freezes is low, set for the freezing point of water to further lower the possibility that water freezes. The predetermined water temperature Tw1 corresponds to the second water temperature of the present invention.

[0033] In the determination in Step ST10, when at least one of the water temperature Twa, the water temperature Twb, the water temperature Twc, and the water temperature Twd is equal to or less than the predetermined water temperature Tw1 (Step ST10: YES), the process proceeds to Step ST11, and when all of the water temperature Twa, the water temperature Twb, the water temperature Twc, and the water temperature Twd exceed the predetermined water temperature Tw1 (Step ST10: NO), the main routine ends.

[0034] In Step ST11, freeze prevention specification processing illustrated in FIG. 3 is performed.

[0035] In the freeze prevention specification processing in FIG. 3, the subscript i of a processing flag Fi is any of a, b, c. More specifically, a processing flag Fa denotes a processing flag of the first indoor terminal unit 4a, a processing flag Fb denotes a processing flag of the first indoor terminal unit 4b, and a processing flag Fc denotes a processing flag of the third indoor terminal unit 4c (hereafter, similarly using the subscript i, the water temperature Twa, the water temperature Twb, and the water temperature Twc are sometimes referred to as a water temperature Twi, the first indoor terminal unit 4a to the third indoor terminal unit 4c are sometimes referred to as an indoor terminal unit 4i, a room temperature Tka, a room temperature Tkb, and a room temperature Tkc are sometimes referred to as a room temperature Tki, the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c are sometimes referred to as an indoor opening / closing valve 12i, the first room temperature sensor 19a to the third room temperature sensor 19c are sometimes referred to as a room temperature sensor 19i, and the first room 3a to the third room 3c are sometimes referred to as a room 3i). Fa = "0" indicates that the first indoor terminal unit 4a is not subjected to the freeze prevention processing, Fa = "1" indicates that the first indoor terminal unit 4a has not yet been subjected to the freeze prevention processing, and Fa = "2" indicates that the first indoor terminal unit 4a has already been subjected to the freeze prevention processing. A processing flag Fb is a processing flag of the second indoor terminal unit 4b. Fb = "0" indicates that the second indoor terminal unit 4b is not subjected to the freeze prevention processing, Fb = "1" indicates that the second indoor terminal unit 4b has not yet been subjected to the freeze prevention processing, and Fb = "2" indicates that the second indoor terminal unit 4b has already been subjected to the freeze prevention processing. A processing flag Fc is a processing flag of the third indoor terminal unit 4c. Fc = "0" indicates that the third indoor terminal unit 4c is not subjected to the freeze prevention processing, Fc = "1" indicates that the third indoor terminal unit 4c has not yet been subjected to the freeze prevention processing, and Fc = "2" indicates that the third indoor terminal unit 4c has already been subjected to the freeze prevention processing.

[0036] In the freeze prevention specification processing, the processing flag Fa, the processing flag Fb, and the processing flag Fc are set to "0" in Step ST12 in FIG. 3.

[0037] Then, in Step ST13, the room temperature Tka detected by the first room temperature sensor 19a, the room temperature Tkb detected by the second room temperature sensor 19b, and the room temperature Tkc detected by the third room temperature sensor 19c are read.

[0038] Then, in Step ST14, it is determined whether at least one of the water temperature Twa detected by the first water temperature sensor 20a, the water temperature Twb detected by the second water temperature sensor 20b, and the water temperature Twc detected by the third water temperature sensor 20c is equal to or less than a predetermined water temperature Tw2. In this determination, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2 (Step ST14: YES), the process proceeds to Step ST15, and when all of the water temperature Twa, the water temperature Twb, and the water temperature Twc exceed the predetermined water temperature Tw2 (Step ST14: NO), the process proceeds to Step ST16. Herein, the predetermined water temperature Tw2 is a temperature determined considering a possibility that water freezes, and may be the same temperature as the predetermined water temperature Tw1 or a temperature having a margin larger than that of the predetermined water temperature Tw1. More specifically, the predetermined water temperature Tw1 is a temperature equal to or less than the predetermined water temperature Tw2. The predetermined water temperature Tw2 corresponds to the first water temperature of the present invention.

[0039] In Step ST16, it is determined whether at least one of the room temperature Tka detected by the first room temperature sensor 19a, the room temperature Tkb detected by the second room temperature sensor 19b, and the room temperature Tkc detected by the third room temperature sensor 19c is equal to or less than a predetermined room temperature Tks. The predetermined room temperature Tks corresponds to the predetermined temperature to be compared with the room temperature Tka detected by the first room temperature sensor 19a, the room temperature Tkb detected by the second room temperature sensor 19b, and the room temperature Tkc detected by the third room temperature sensor 19c to decide the indoor opening / closing valve where the freeze prevention control means performs the freeze prevention control in the present invention.

[0040] In this determination, when at least one of the room temperature Tka, the room temperature Tkb, and the room temperature Tkc is equal to or less than the predetermined room temperature Tks (Step ST16: YES), the process proceeds to Step ST15, and when the room temperature Tka, the room temperature Tkb, and the room temperature Tkc all exceed the predetermined room temperature Tks (Step ST16: NO), the process proceeds to Step ST25.

[0041] In Step ST15, the processing flag Fi is set to "1" for the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks or the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks. Specifically, in Step ST14, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2, so that the process proceeds to Step ST15, the processing flag Fi is set to "1" for the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks. In Step ST16, when at least one of the room temperature Tka, the room temperature Tkb, and the room temperature Tkc is equal to or less than the predetermined room temperature Tks, so that the process proceeds to Step ST15, the processing flag Fi is set to "1" for the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks.

[0042] Then, in Step ST17, it is determined whether at least one of the processing flag Fa of the first indoor terminal unit 4a, the processing flag Fb of the second indoor terminal unit 4b, and the processing flag Fc of the third indoor terminal unit 4c is "1". In this determination, when at least one of the processing flags Fa, Fb, Fc is "1" (Step ST17: YES), the process proceeds to Step ST18. On the other hand, when none of the processing flags Fa, Fb, Fc is "1", i.e., all of the processing flags Fa, Fb, Fc are "0" or "2" (Step ST17: NO), the process proceeds to Step ST25.

[0043] In Step ST18, it is determined whether there are two or more of the processing flags Fa, Fb, Fc set to "1". In this determination, when there are two or more of the processing flags Fa, Fb, Fc set to "1" (Step ST18: YES), the process proceeds to Step ST19, and when one of the processing flags Fa, Fb, Fc is set to "1" (Step ST18: NO), the process proceeds to Step ST20.

[0044] In Step ST19, when there are two or more of the indoor terminal units 4i to which the freeze prevention processing is to be performed, the indoor terminal unit to which the freeze prevention processing is preferentially performed is specified. In Step ST14, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2, so that the process proceeds to Step ST15, the indoor terminal unit 4i with the lowest water temperature Twi among the two or more of the indoor terminal units is specified as the indoor terminal unit to which the freeze prevention processing is preferentially performed. In Step ST16, when at least one of the room temperatures Tka, Tkb, Tkc is equal to or less than the predetermined room temperature Tks, so that the process proceeds to Step ST15, the indoor terminal unit 4i with the lowest room temperature Tki among the two or more of the indoor terminal units is specified as the indoor terminal unit to which the freeze prevention processing is preferentially performed.

[0045] On the other hand, in Step ST20, there is one indoor terminal unit 4i to which the freeze prevention processing is to be performed, and therefore the indoor terminal unit is specified as the indoor terminal unit to which the freeze prevention processing is preferentially performed.

[0046] Then, in Step ST21, the indoor opening / closing valve control processing illustrated in FIG. 4 is performed.

[0047] In the indoor opening / closing valve control processing, opening operation of the indoor opening / closing valve 12i of the specified indoor terminal unit 4i is first performed in Step ST30 in FIG. 4, so that water is made to flow to the indoor terminal unit 4i.

[0048] Then, in Step ST31, the room temperature Tki detected by the room temperature sensor 19i of the specified indoor terminal unit 4i is read. Then, in Step ST32, it is determined whether a predetermined room temperature measurement time n1 (e.g., 60 seconds) has elapsed after the room temperature Tki was read. When the room temperature measurement time n1 has elapsed (Step ST32: YES), the process proceeds to Step ST33, and when the room temperature measurement time n1 has not elapsed (Step ST32: NO), ST32 is repeated. In Step ST33, the room temperature Tki detected by the room temperature sensor 19i is read. Then, in Step ST34, the room temperature decrease amount from a room temperature Tki0 at the start of the measurement to a current room temperature Tkin is calculated and the room temperature decrease amount is divided by the room temperature measurement time n1, thereby calculating a room temperature decrease amount ΔT per unit time.

[0049] Then, in Step ST35, it is determined whether the room temperature decrease amount ΔT per unit time is equal to or more than the decrease amount threshold or it is determined whether a third set time Nv2 (e.g., 15 minutes) has elapsed from the opening operation of the indoor opening / closing valve 12i. When the room temperature decrease amount ΔT per unit time is equal to or more than the decrease amount threshold or when the third set time Nv2 has elapsed from the opening operation of the indoor opening / closing valve 12i (Step ST35: YES), the process proceeds to Step ST36. When the room temperature decrease amount ΔT per unit time is less than the decrease amount threshold and when the third set time Nv2 has not elapsed from the opening operation of the indoor opening / closing valve 12i (Step ST35: NO), the process proceeds to Step ST31.

[0050] In Step ST36, closing operation of the indoor opening / closing valve 12i is performed, the indoor opening / closing valve control processing is ended, the process returns to the indoor terminal unit specification processing in FIG. 3, and the processing in Step ST22 is carried out.

[0051] In Step ST22 in FIG. 3, the processing flag Fi of the indoor terminal unit 4i is set to "2" and the indoor terminal unit 4i is set such that the indoor terminal unit 4i has already been subjected to the freeze prevention processing.

[0052] Then, in Step ST23, the outdoor air temperature To detected by the outdoor air temperature sensor 22 is read.

[0053] Then, in Step ST24, it is determined whether the outdoor air temperature To is equal to or less than the predetermined temperature Tos. In this determination, when the outdoor air temperature To is equal to or less than the predetermined temperature Tos (Step ST24: YES), the process proceeds to Step ST17, and when the outdoor air temperature To exceeds the predetermined temperature Tos (Step ST24: NO), the process proceeds to Step ST25.

[0054] In Step ST25, the drive of the pump 15 is stopped, and then the process returns to the main routine in FIG. 2, so that the processing of the main routine ends.[Action of freeze prevention control method of heat pump-type hot-water heating device]

[0055] Next, the action of the freeze prevention control performed by the freeze prevention control means 26 in the heat pump-type hot-water heating device 1 is described with reference to FIGS. 2 to 4.

[0056] When the outdoor air temperature To has become equal to or less than the predetermined temperature Tos, at least one of the water temperatures Twi of the plurality of indoor terminal units 4i where the operation stops is equal to or less than the predetermined water temperature Tw2 (Step ST14 in FIG. 3: YES) or when at least one of the room temperatures Tki of the rooms 3i is equal to or less than the predetermined room temperature Tks (Step ST16 in FIG. 3: YES), the indoor opening / closing valve 12i of the relevant indoor terminal unit 4i is opened so that water flows to the indoor terminal unit 4i (Step ST30 in FIG. 4). For example, when the water temperature Twa of the first indoor terminal unit 4a of this embodiment is equal to or less than the predetermined water temperature Tw2, the room temperature Tkb of the second indoor terminal unit 4b is equal to or less than the predetermined room temperature Tks, and the water temperature Twc of the third indoor terminal unit 4c exceeds the predetermined water temperature Tw2 and the room temperature Tkc also exceeds the predetermined room temperature Tks, the first indoor opening / closing valve 12a of the first indoor terminal unit 4a and the second indoor opening / closing valve 12b of the second indoor terminal unit 4a are opened and the freeze prevention control is performed for the third set time Nv2. By performing the freeze prevention control as described above, even when the outdoor air temperature To is equal to or less than the predetermined temperature Tos, water circulates to the first water circulation circuit 16 and the second water circulation circuit 17, and therefore the water in the water circulation circuits can be prevented from freezing. The third room 3c, in which the heating operation is stopped and the room temperature Tkc exceeds the predetermined room temperature Tks, is supposed to be set to a room temperature where people do not feel cold, and the freeze prevention control of the third indoor opening / closing valve 12c installed in the third room 3c is not performed and the decrease in the room temperature of the third room 3c is suppressed, and therefore a feeling of discomfort is not given to people using the third room 3c.

[0057] When there are two or more of the indoor terminal units 4i where the freeze prevention control is performed, the freeze prevention control is performed to the two or more of the indoor terminal units 4i one by one in turn (repeat Step ST17 to Step ST24 in FIG. 3). Thus, a significant decrease in the room temperature of a specific room among the first room 3a to the third room 3c can be suppressed and the comfort of users in the first room 3a to the third room 3c can be maintained. The freeze prevention control is performed to the two or more of the indoor terminal units 4i one by one in turn, and therefore the number of rooms where the temperature decreases can be minimized.

[0058] When the freeze prevention control is performed to the two or more of the indoor terminal units 4i in turn, the freeze prevention control is preferentially performed in turn from the indoor terminal unit with the lowest water temperature Twi or the indoor terminal unit with the lowest room temperature Tki (Step ST19 in FIG. 3). For example, in a case where the water temperature Twa of the first indoor terminal unit 4a and the water temperature Twb of the second indoor terminal unit 4b of this embodiment are equal to or less than the predetermined water temperature Tw2, when the water temperature Twa of the first indoor terminal unit 4a is lower than the water temperature Twb of the second indoor terminal unit 4b, the freeze prevention control of the first indoor terminal unit 4a is first started. Thus, the freeze prevention control is preferentially performed to the first water circulation circuit 16 having a risk of freezing, and therefore freezing can be reliably prevented.

[0059] Even when the outdoor air temperature To is equal to or less than the predetermined temperature Tos, the freeze prevention control is not performed when the water temperature Twa of the first indoor terminal unit 4a, the water temperature Twb of the second indoor terminal unit 4b, the water temperature Twc of the third indoor terminal unit 4c, and the water temperature Twd of the water-refrigerant heat exchanger 7 exceed the predetermined water temperature Tw1 that is the water temperature having a possibility of freezing (Step ST10: NO in FIG. 2). Thus, even when the outdoor air temperature is low, the freeze prevention control is not performed when the water temperature is high and there is less risk of freezing. Therefore, the decrease in the room temperatures of the first room 3a to the third room 3c is suppressed, so that the comfort of users in the first room 3a to the third room 3c can be maintained.

[0060] Further, when the decrease amount per unit time of the room temperature of the room 3i where the indoor terminal unit 4i, to which the freeze prevention control is performed, is installed has become equal to or more than the decrease amount threshold, the freeze prevention control is stopped (Step ST35 and Step ST36 in FIG. 4) and when the room temperature of the room 3i sharply decreases, the freeze prevention control is stopped, and thus a further decrease in the room temperature of the room 3i can be prevented and the comfort of a user in the room 3i can be maintained.

[0061] Further, before the freeze prevention control is performed, the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the first indoor opening / closing valve 12b of the second indoor terminal unit 4b, and the third indoor opening / closing valve 12c of the third indoor terminal unit 4c are opened and the drive control of the pump 15 is performed during the second set time Nv1, so that water is circulated throughout the first water circulation circuit 16 to the third water circulation circuit 18 (Step ST4 to Step ST7 in FIG. 2). Thus, even when a place having a risk of freezing arises in places other than places where the water temperatures are detected by the water temperature sensors 20a to 20c among the first water circulation circuit 16 to the third water circulation circuit 18, the risk of freezing can be reliably avoided.

[0062] Although this embodiment describes the heat pump-type hot-water heating device 1 having the water-refrigerant heat exchanger 7 exchanging heat between water and a refrigerant, the same effects can be obtained even when water is heated by a boiler in place of the water-refrigerant heat exchanger 7.

[0063] Further, although this embodiment describes that, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2, the freeze prevention control is performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks and when all of the water temperature Twa, the water temperature Twb, and the water temperature Twc exceed the predetermined water temperature Tw2 and at least one of the room temperatures Tka, Tkb, Tkc is equal to or less than the predetermined room temperature Tks, the freeze prevention control is performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks, the present invention is not limited thereto. For example, the freeze prevention control may be performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks, regardless of whether at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2. Alternatively, the freeze prevention control may be performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks and the room temperature Tki is equal to or less than the predetermined room temperature Tks.

[0064] Further, although this embodiment describes that, when there are two or more of the indoor terminal units 4i to which the freeze prevention control is performed, the freeze prevention control is performed to the two or more of the indoor terminal units 4i one by one in turn, the freeze prevention control may be performed to the two or more of the indoor terminal units 4i at a time for the two or more of the indoor terminal units 4i. For example, when there are four or more of the indoor terminal units 4i, two indoor terminal units of the indoor terminal unit with the lowest water temperature Twi and the indoor terminal unit with the second lowest water temperature Twi are specified as the indoor terminal units to which the freeze prevention control is preferentially performed, and the freeze prevention control may be performed to the two indoor terminal units at a time.Reference Signs List

[0065] 1: heat pump-type hot-water heating device 2: outdoor unit 3a: first room 3b: second room 3c: third room 4a: first indoor terminal unit 4b: second indoor terminal unit 4c: third indoor terminal unit 5: compressor 6: four-way valve 7: water-refrigerant heat exchanger 8: expansion valve 9: outdoor heat exchanger 10: refrigerant circuit 12a: first indoor opening / closing valve 12b: second indoor opening / closing valve 12c: third indoor opening / closing valve 13a: first indoor heat exchanger 13b: second indoor heat exchanger 13c: third indoor heat exchanger 15: pump 16: first water circulation circuit 17: second water circulation circuit 18: third water circulation circuit 19a: first room temperature sensor 19b: second room temperature sensor 19c: third room temperature sensor 20a: first water temperature sensor 20b: second water temperature sensor 20c: third water temperature sensor 21: fourth water temperature sensor 22: outdoor air temperature sensor 25: control means 26: freeze prevention control means

Examples

Embodiment Construction

[0010]Next, embodiments according to the present invention are described with reference to the drawings. The embodiments described below exemplify devices or methods for embodying the technical idea of the present invention. The technical idea of the present invention does not specify the materials, shapes, structures, arrangement, and the like of constituent components to the materials, shapes, structures, arrangement, and the like described below. The technical idea of the present invention can be variously altered in the technical scope defined by claims.

[Heat pump-type hot-water heating device]

[0011]FIG. 1 is a circuit diagram illustrating a heat pump-type hot-water heating device 1 of a first embodiment according to the present invention.

[0012]The heat pump-type hot-water heating device 1 includes an outdoor unit 2 and a plurality of indoor terminal units 4a, 4b, 4c (referred to as a first indoor terminal unit 4a, a second indoor terminal unit 4b, a third indoor terminal unit 4...

Technical Field

[0001] The present invention relates to a hot water heating device preventing freezing of a water circulation circuit making water flow to a plurality of indoor terminal units in a cold season.Background Art

[0002] There is a hot water heating device performing heating by making water heated by a heat source unit flow to a plurality of indoor terminal units installed in a plurality of rooms. The hot water heating device has a risk that, when there is an indoor terminal unit where operation stops, water in a pipe of a water circulation circuit, which is a path through which water flows to the indoor terminal unit, is frozen in a cold season.

[0003] The hot water heating device of PTL 1 has a water circulation circuit where a heat source unit heating water, a pump, and a plurality of indoor terminal units and opening / closing valves connected in parallel to the heat source unit are connected by a pipe. In PTL 1 above, when the outdoor air temperature becomes equal to or less than the predetermined temperature (e.g., 3°C) during stop of heating operation of all of the indoor terminal units, the pump is operated and one opening / closing valve or two or more opening / closing valves of all of the indoor terminal units are opened at a time in turn to thereby make water flow throughout the water circulation circuit and prevent the water in the pipe of the water circulation circuit from freezing.Citation ListPatent Literature

[0004] PTL 1: JP 2003-240381 ASummary of InventionTechnical Problem

[0005] The hot water heating device of PTL 1 is configured such that, when the outdoor air temperature becomes equal to or less than the predetermined temperature, water is made to flow to all of the indoor terminal units to prevent freezing, and therefore low temperature water flows also to the indoor terminal unit, which is installed in a room where the room temperature is such that people do not feel cold. When the low temperature water flows to the indoor terminal unit in such a room, the room temperature of the room decreases, which pose a risk that the room temperature becomes such a room temperature that people feel cold.

[0006] Thus, the present invention has been made to solve such a problem. It is an object of the present invention to provide a hot-water heating device preventing freezing of the water circulation circuit when the outdoor air temperature has become equal to or less than the predetermined temperature and suppressing a decrease in the room temperature of the room where the room temperature is such that people do not feel cold.Solution to Problem

[0007] One aspect of the invention is a hot water heating device including: a water circulation circuit where a heat source unit configured to heat water, a pump, and a plurality of indoor terminal units and a plurality of opening / closing valves connected in parallel to the heat source unit are connected by a pipe and where water circulates between the plurality of indoor terminal units and the heat source unit; an outdoor air temperature detection means configured to detect the outdoor air temperature; a plurality of terminal unit water temperature detection means configured to detect the terminal unit water temperature, the terminal unit water temperature being the temperature of water flowing through each of the plurality of indoor terminal units; a plurality of room temperature detection means configured to detect the room temperature of a room where each of the plurality of indoor terminal units is installed; and a freeze prevention control means configured to perform freeze prevention control by opening the opening / closing valve corresponding to the indoor terminal unit where operation stops by closing the corresponding opening / closing valve to make water flow to the indoor terminal unit; in which the freeze prevention control means is configured such that, when the outdoor air temperature is equal to or less than the predetermined temperature, the freeze prevention control means performs the freeze prevention control to the opening / closing valve corresponding to the indoor terminal unit satisfying at least one of states in which the terminal unit water temperature of water flowing through the indoor terminal unit is equal to or less than a first water temperature and in which the room temperature of the room where the indoor terminal unit is installed is equal to or less than the predetermined temperature among the indoor terminal units where the operation stops.Advantageous Effects of Invention

[0008] The hot-water heating device of the present invention can prevent freezing of the water circulation circuit when the outdoor air temperature has become equal to or less than the predetermined temperature and can suppress a decrease in the room temperature of the room where the temperature is such that people do not feel cold.Brief Description of Drawings

[0009] FIG. 1 is a circuit diagram illustrating a heat pump-type hot-water heating device according to the present invention; FIG. 2 is a flowchart showing the main routine of freeze prevention control performed by the heat pump-type hot-water heating device according to the present invention; FIG. 3 is a flowchart showing specific operation of freeze prevention specification processing in the flowchart in FIG. 2; and FIG. 4 is a flowchart showing specific operation of indoor opening / closing valve control processing in the flowchart in FIG. 3. Description of Embodiments

[0010] Next, embodiments according to the present invention are described with reference to the drawings. The embodiments described below exemplify devices or methods for embodying the technical idea of the present invention. The technical idea of the present invention does not specify the materials, shapes, structures, arrangement, and the like of constituent components to the materials, shapes, structures, arrangement, and the like described below. The technical idea of the present invention can be variously altered in the technical scope defined by claims.[Heat pump-type hot-water heating device]

[0011] FIG. 1 is a circuit diagram illustrating a heat pump-type hot-water heating device 1 of a first embodiment according to the present invention.

[0012] The heat pump-type hot-water heating device 1 includes an outdoor unit 2 and a plurality of indoor terminal units 4a, 4b, 4c (referred to as a first indoor terminal unit 4a, a second indoor terminal unit 4b, a third indoor terminal unit 4c) installed in a plurality of rooms 3a, 3b, 3c (referred to as a first room 3a, a second room 3b, a third room 3c), respectively.

[0013] The outdoor unit 2 includes a refrigerant circuit 10 formed by sequentially connecting a compressor 5, a four-way valve 6, a water-refrigerant heat exchanger 7 exchanging heat between water and a refrigerant, an expansion valve 8, and an outdoor heat exchanger 9 by a pipe. The outdoor unit 2 further includes a pump 15 and a fourth water temperature sensor 21 described later. The water-refrigerant heat exchanger 7 corresponds to the heat source unit of the present invention.

[0014] The first indoor terminal unit 4a has a first indoor opening / closing valve 12a and a first indoor heat exchanger 13a. The pump 15, the water-refrigerant heat exchanger 7, the first indoor opening / closing valve 12a, and the first indoor heat exchanger 13a are sequentially connected by a pipe, forming a first water circulation circuit 16. The first indoor terminal unit 4a further has a first room temperature sensor 19a and a first water temperature sensor 20a. The first room temperature sensor 19a detects the room temperature of the first room 3a. The first water temperature sensor 20a is arranged between the pump 15 and the first indoor heat exchanger 13a of the first water circulation circuit 16 and detects the temperature of water that has passed through the first indoor heat exchanger 13a.

[0015] The second indoor terminal unit 4b has a second indoor opening / closing valve 12b and a second indoor heat exchanger 13b. One end of a pipe is connected to the first water circulation circuit 16 between the water-refrigerant heat exchanger 7 and the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the other end of the pipe is connected to the first water circulation circuit 16 between the pump 15 and the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and the second indoor opening / closing valve 12b and the second indoor heat exchanger 13b are connected in series between the one end and the other end of the pipe. This forms a second water circulation circuit 17 where the pump 15, the water-refrigerant heat exchanger 7, the second indoor opening / closing valve 12b, and the second indoor heat exchanger 13b are sequentially connected by the pipe. The second indoor terminal unit 4b further has a second room temperature sensor 19b and a second water temperature sensor 20b. The second room temperature sensor 19b detects the room temperature of the second room 3b. The second water temperature sensor 20b is arranged between the pump 15 and the second indoor heat exchanger 13b of the second water circulation circuit 17 and detects the temperature of water that has passed through the second indoor heat exchanger 13b.

[0016] The third indoor terminal unit 4c has a third indoor opening / closing valve 12c and a third indoor heat exchanger 13c. One end of a pipe is connected to the first water circulation circuit 16 between the water-refrigerant heat exchanger 7 and the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the other end of the pipe is connected to the first water circulation circuit 16 between the pump 15 and the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and the third indoor opening / closing valve 12c and the third indoor heat exchanger 13c are connected in series between the one end and the other end of the pipe. This forms the third water circulation circuit 18 where the pump 15, the water-refrigerant heat exchanger 7, the third indoor opening / closing valve 12c, and the third indoor heat exchanger 13c are sequentially connected by the pipe. The third indoor terminal unit 4c further has a third room temperature sensor 19c and a third water temperature sensor 20c. The third room temperature sensor 19c detects the room temperature of the third room 3c. The third water temperature sensor 20c is arranged between the pump 15 and the third indoor heat exchanger 13c of the third water circulation circuit 18 and detects the temperature that has passed through the third indoor heat exchanger 13c.

[0017] Thus, the first indoor terminal unit 4a and the first indoor opening / closing valve 12a connected to the first water circulation circuit 16, the second indoor terminal unit 4b and the second indoor opening / closing valve 12b connected to the second water circulation circuit 17, and the third indoor terminal unit 4c and the third indoor opening / closing valve 12c connected to the third water circulation circuit 18 are connected in parallel to the water-refrigerant heat exchanger 7.

[0018] Further, between the water-refrigerant heat exchanger 7 and the first indoor opening / closing valve 12a of the first water circulation circuit 16, the fourth water temperature sensor 21 is arranged which detects the temperature of water before diverting to the second water circulation circuit 17 and the third water circulation circuit 18 through the water-refrigerant heat exchanger 7. Outside the rooms, an outdoor air temperature sensor 22 detecting the outdoor air temperature is arranged.

[0019] The first indoor terminal unit 4a to the third indoor terminal unit 4c correspond to the indoor terminal units of the present invention. The first water circulation circuit 16 to the third water circulation circuit 18 correspond to the water circulation circuits of the present invention. The first room temperature sensor 19a to the third room temperature sensor 19c correspond to the room temperature detection means of the present invention. The first water temperature sensor 20a to the third water temperature sensor 20c correspond to the terminal unit water temperature detection means of the present invention. The fourth water temperature sensor 21 corresponds to the heat source unit water temperature detection means of the present invention. The outdoor air temperature sensor 22 corresponds to the outdoor air temperature detection means of the present invention.

[0020] When the first indoor opening / closing valve 12a of the first indoor terminal unit 4a is opened and the pump 15 is driven, water circulates through the first water circulation circuit 16, the water is supplied to the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and the water returns from the first indoor heat exchanger 13a to the water-refrigerant heat exchanger 7. Similarly, when the second indoor opening / closing valve 12b of the second indoor terminal unit 4b is opened and the pump 15 is driven, water circulates through the second water circulation circuit 17, the water is supplied to the second indoor heat exchanger 13b of the second indoor terminal unit 4b, and the water returns from the second indoor heat exchanger 13b to the water-refrigerant heat exchanger 7. Similarly, when the third indoor opening / closing valve 12c of the third indoor terminal unit 4c is opened and the pump 15 is driven, water circulates through the third water circulation circuit 18, the water is supplied to the third indoor heat exchanger 13c of the third indoor terminal unit 4c, and the water returns from the third indoor heat exchanger 13c to the water-refrigerant heat exchanger 7.

[0021] When the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the second indoor opening / closing valve 12b of the second indoor terminal unit 4b, and the third indoor opening / closing valve 12c of the third indoor terminal unit 4c are all opened and the pump 15 is driven, water circulates through all of the first water circulation circuit 16, the second water circulation circuit 17, and the third water circulation circuit 18, the water is supplied in parallel to the first indoor heat exchanger 13a of the first indoor terminal unit 4a, the second indoor heat exchanger 13b of the second indoor terminal unit 4b, and the third indoor heat exchanger 13c of the third indoor terminal unit 4c, and the water returns from the first indoor heat exchanger 13a to the third indoor heat exchanger 13c to the water-refrigerant heat exchanger 7.

[0022] The heat pump-type hot-water heating device 1 of this embodiment has a control means 25 controlling each device. More specifically, the control means 25 performs various kinds of control related to the operation of the heat pump-type hot-water heating device 1, such as drive control of the compressor 5, switching control of the four-way valve 6, opening degree control of the expansion valve 8, drive control of the pump 15, and opening / closing control of the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c, based on the detected values detected by the first room temperature sensor 19a to the third room temperature sensor 19c, the first water temperature sensor 20a to the third water temperature sensor 20c, the fourth water temperature sensor 21, and the outdoor air temperature sensor 22. The control means 25 further includes a timer unit measuring time and a storage unit storing a control program of the heat pump-type hot-water heating device 1.

[0023] The control means 25 of the heat pump-type hot-water heating device 1 of this embodiment has a freeze prevention control means 26 as illustrated in FIG. 1. The freeze prevention control means 26 can be realized by software as a function of the control means 25.

[0024] The heat pump-type hot-water heating device 1 of this embodiment is configured such that freeze prevention control is automatically started during stop of the heating operation of the outdoor unit 2, the first indoor terminal unit 4a installed in the first room 3a, the second indoor terminal unit 4b installed in the second room 3b, and the third indoor terminal unit 4c installed in the third room 3c. The first indoor opening / closing valve 12a of the first indoor terminal unit 4a where the heating operation stops, the second indoor terminal unit 4b where the heating operation stops, and the third indoor opening / closing valve 12 of the third indoor terminal unit 4c where the heating operation stops are brought into a closed state.[Freeze prevention control]

[0025] Next, the freeze prevention control performed by the freeze prevention control means 26 in the heat pump-type hot-water heating device 1 of this embodiment is described with reference to FIGS. 2 to 4. FIG. 2 illustrates the main routine of the freeze prevention control. FIG. 3 illustrates indoor terminal unit specification processing included in the main routine in FIG. 2. FIG. 4 illustrates indoor opening / closing valve control processing included in the indoor terminal unit specification processing in FIG. 3.

[0026] First, in Step ST1 in FIG. 2, it is determined whether stop time (pump stop time) PT of the pump 15 is equal to or more than a first set time PTs (e.g., 3 hours). Herein, the first set time PTs is set to time during which water in the water circulation circuit is supposed not to freeze without the freeze prevention control. In this determination, when the pump stop time PT is equal to or more than the first set time PTs (Step ST1 : YES), the process proceeds to Step ST2, and when the pump stop time PT falls below the first set time PTs (Step ST1: NO), Step ST1 is repeated. In Step ST2, an outdoor air temperature To detected by the outdoor air temperature sensor 22 is read.

[0027] Then, in Step ST3, it is determined whether the outdoor air temperature To is equal to or less than a predetermined temperature Tos (e.g., 5°C). Herein, the predetermined temperature Tos is set to a temperature at which water in the water circulation circuit is supposed not to freeze. In this determination, when the outdoor air temperature To is equal to or less than the predetermined temperature Tos (Step ST3: YES), the process proceeds to Step ST4, and when the outdoor air temperature To exceeds the predetermined temperature Tos (Step ST3: NO), the process proceeds to Step ST1. In Step ST4, the drive of the pump 15 is started.

[0028] Then, in Step ST5, opening operation of the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the second indoor opening / closing valve 12b of the second indoor terminal unit 4b, and the third indoor opening / closing valve 12c of the third indoor terminal unit 4c is performed.

[0029] Then, in Step ST6, it is determined whether a second set time Nv1 (e.g., 15 minutes) has elapsed from the opening operation of the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c. Herein, the second set time Nv1 is set to time sufficient for solving a local temperature decrease in the water circulation circuit. The second set time Nv1 corresponds to the predetermined time during which the freeze prevention control means opens the opening / closing valves of all of the indoor terminal units and performs the drive control of the pump before performing the freeze prevention control in the present invention.

[0030] When the second set time Nv1 has elapsed (Step ST6: YES), the process proceeds to Step ST7, and when the second set time Nv1 has not elapsed (Step ST6: NO), ST6 is repeated. In Step ST7, closing operation of the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c is performed.

[0031] Then, in Step ST8, a water temperature Twa detected by the first water temperature sensor 20a, a water temperature Twb detected by the second water temperature sensor 20b, and a water temperature Twc detected by the third water temperature sensor 20c are read. Then, in Step ST9, a water temperature Twd detected by the fourth water temperature sensor 21 is read. The water temperature Twa, the water temperature Twb, and the water temperature Twc correspond to the terminal unit water temperature of the present invention and the water temperature Twd corresponds to the heat source unit water temperature of the present invention.

[0032] Then, in Step ST10, it is determined whether at least one of the water temperature Twa, the water temperature Twb, the water temperature Twc, and the water temperature Twd is equal to or less than a predetermined water temperature Tw1. Herein, the predetermined water temperature Tw1 is a temperature determined by considering a possibility that water freezes, and is set to 0°C, which is the freezing point of water, for example. The predetermined water temperature Tw1 may also be set to 2°C with a margin, in which the possibility that water freezes is low, set for the freezing point of water to further lower the possibility that water freezes. The predetermined water temperature Tw1 corresponds to the second water temperature of the present invention.

[0033] In the determination in Step ST10, when at least one of the water temperature Twa, the water temperature Twb, the water temperature Twc, and the water temperature Twd is equal to or less than the predetermined water temperature Tw1 (Step ST10: YES), the process proceeds to Step ST11, and when all of the water temperature Twa, the water temperature Twb, the water temperature Twc, and the water temperature Twd exceed the predetermined water temperature Tw1 (Step ST10: NO), the main routine ends.

[0034] In Step ST11, freeze prevention specification processing illustrated in FIG. 3 is performed.

[0035] In the freeze prevention specification processing in FIG. 3, the subscript i of a processing flag Fi is any of a, b, c. More specifically, a processing flag Fa denotes a processing flag of the first indoor terminal unit 4a, a processing flag Fb denotes a processing flag of the first indoor terminal unit 4b, and a processing flag Fc denotes a processing flag of the third indoor terminal unit 4c (hereafter, similarly using the subscript i, the water temperature Twa, the water temperature Twb, and the water temperature Twc are sometimes referred to as a water temperature Twi, the first indoor terminal unit 4a to the third indoor terminal unit 4c are sometimes referred to as an indoor terminal unit 4i, a room temperature Tka, a room temperature Tkb, and a room temperature Tkc are sometimes referred to as a room temperature Tki, the first indoor opening / closing valve 12a to the third indoor opening / closing valve 12c are sometimes referred to as an indoor opening / closing valve 12i, the first room temperature sensor 19a to the third room temperature sensor 19c are sometimes referred to as a room temperature sensor 19i, and the first room 3a to the third room 3c are sometimes referred to as a room 3i). Fa = "0" indicates that the first indoor terminal unit 4a is not subjected to the freeze prevention processing, Fa = "1" indicates that the first indoor terminal unit 4a has not yet been subjected to the freeze prevention processing, and Fa = "2" indicates that the first indoor terminal unit 4a has already been subjected to the freeze prevention processing. A processing flag Fb is a processing flag of the second indoor terminal unit 4b. Fb = "0" indicates that the second indoor terminal unit 4b is not subjected to the freeze prevention processing, Fb = "1" indicates that the second indoor terminal unit 4b has not yet been subjected to the freeze prevention processing, and Fb = "2" indicates that the second indoor terminal unit 4b has already been subjected to the freeze prevention processing. A processing flag Fc is a processing flag of the third indoor terminal unit 4c. Fc = "0" indicates that the third indoor terminal unit 4c is not subjected to the freeze prevention processing, Fc = "1" indicates that the third indoor terminal unit 4c has not yet been subjected to the freeze prevention processing, and Fc = "2" indicates that the third indoor terminal unit 4c has already been subjected to the freeze prevention processing.

[0036] In the freeze prevention specification processing, the processing flag Fa, the processing flag Fb, and the processing flag Fc are set to "0" in Step ST12 in FIG. 3.

[0037] Then, in Step ST13, the room temperature Tka detected by the first room temperature sensor 19a, the room temperature Tkb detected by the second room temperature sensor 19b, and the room temperature Tkc detected by the third room temperature sensor 19c are read.

[0038] Then, in Step ST14, it is determined whether at least one of the water temperature Twa detected by the first water temperature sensor 20a, the water temperature Twb detected by the second water temperature sensor 20b, and the water temperature Twc detected by the third water temperature sensor 20c is equal to or less than a predetermined water temperature Tw2. In this determination, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2 (Step ST14: YES), the process proceeds to Step ST15, and when all of the water temperature Twa, the water temperature Twb, and the water temperature Twc exceed the predetermined water temperature Tw2 (Step ST14: NO), the process proceeds to Step ST16. Herein, the predetermined water temperature Tw2 is a temperature determined considering a possibility that water freezes, and may be the same temperature as the predetermined water temperature Tw1 or a temperature having a margin larger than that of the predetermined water temperature Tw1. More specifically, the predetermined water temperature Tw1 is a temperature equal to or less than the predetermined water temperature Tw2. The predetermined water temperature Tw2 corresponds to the first water temperature of the present invention.

[0039] In Step ST16, it is determined whether at least one of the room temperature Tka detected by the first room temperature sensor 19a, the room temperature Tkb detected by the second room temperature sensor 19b, and the room temperature Tkc detected by the third room temperature sensor 19c is equal to or less than a predetermined room temperature Tks. The predetermined room temperature Tks corresponds to the predetermined temperature to be compared with the room temperature Tka detected by the first room temperature sensor 19a, the room temperature Tkb detected by the second room temperature sensor 19b, and the room temperature Tkc detected by the third room temperature sensor 19c to decide the indoor opening / closing valve where the freeze prevention control means performs the freeze prevention control in the present invention.

[0040] In this determination, when at least one of the room temperature Tka, the room temperature Tkb, and the room temperature Tkc is equal to or less than the predetermined room temperature Tks (Step ST16: YES), the process proceeds to Step ST15, and when the room temperature Tka, the room temperature Tkb, and the room temperature Tkc all exceed the predetermined room temperature Tks (Step ST16: NO), the process proceeds to Step ST25.

[0041] In Step ST15, the processing flag Fi is set to "1" for the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks or the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks. Specifically, in Step ST14, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2, so that the process proceeds to Step ST15, the processing flag Fi is set to "1" for the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks. In Step ST16, when at least one of the room temperature Tka, the room temperature Tkb, and the room temperature Tkc is equal to or less than the predetermined room temperature Tks, so that the process proceeds to Step ST15, the processing flag Fi is set to "1" for the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks.

[0042] Then, in Step ST17, it is determined whether at least one of the processing flag Fa of the first indoor terminal unit 4a, the processing flag Fb of the second indoor terminal unit 4b, and the processing flag Fc of the third indoor terminal unit 4c is "1". In this determination, when at least one of the processing flags Fa, Fb, Fc is "1" (Step ST17: YES), the process proceeds to Step ST18. On the other hand, when none of the processing flags Fa, Fb, Fc is "1", i.e., all of the processing flags Fa, Fb, Fc are "0" or "2" (Step ST17: NO), the process proceeds to Step ST25.

[0043] In Step ST18, it is determined whether there are two or more of the processing flags Fa, Fb, Fc set to "1". In this determination, when there are two or more of the processing flags Fa, Fb, Fc set to "1" (Step ST18: YES), the process proceeds to Step ST19, and when one of the processing flags Fa, Fb, Fc is set to "1" (Step ST18: NO), the process proceeds to Step ST20.

[0044] In Step ST19, when there are two or more of the indoor terminal units 4i to which the freeze prevention processing is to be performed, the indoor terminal unit to which the freeze prevention processing is preferentially performed is specified. In Step ST14, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2, so that the process proceeds to Step ST15, the indoor terminal unit 4i with the lowest water temperature Twi among the two or more of the indoor terminal units is specified as the indoor terminal unit to which the freeze prevention processing is preferentially performed. In Step ST16, when at least one of the room temperatures Tka, Tkb, Tkc is equal to or less than the predetermined room temperature Tks, so that the process proceeds to Step ST15, the indoor terminal unit 4i with the lowest room temperature Tki among the two or more of the indoor terminal units is specified as the indoor terminal unit to which the freeze prevention processing is preferentially performed.

[0045] On the other hand, in Step ST20, there is one indoor terminal unit 4i to which the freeze prevention processing is to be performed, and therefore the indoor terminal unit is specified as the indoor terminal unit to which the freeze prevention processing is preferentially performed.

[0046] Then, in Step ST21, the indoor opening / closing valve control processing illustrated in FIG. 4 is performed.

[0047] In the indoor opening / closing valve control processing, opening operation of the indoor opening / closing valve 12i of the specified indoor terminal unit 4i is first performed in Step ST30 in FIG. 4, so that water is made to flow to the indoor terminal unit 4i.

[0048] Then, in Step ST31, the room temperature Tki detected by the room temperature sensor 19i of the specified indoor terminal unit 4i is read. Then, in Step ST32, it is determined whether a predetermined room temperature measurement time n1 (e.g., 60 seconds) has elapsed after the room temperature Tki was read. When the room temperature measurement time n1 has elapsed (Step ST32: YES), the process proceeds to Step ST33, and when the room temperature measurement time n1 has not elapsed (Step ST32: NO), ST32 is repeated. In Step ST33, the room temperature Tki detected by the room temperature sensor 19i is read. Then, in Step ST34, the room temperature decrease amount from a room temperature Tki0 at the start of the measurement to a current room temperature Tkin is calculated and the room temperature decrease amount is divided by the room temperature measurement time n1, thereby calculating a room temperature decrease amount ΔT per unit time.

[0049] Then, in Step ST35, it is determined whether the room temperature decrease amount ΔT per unit time is equal to or more than the decrease amount threshold or it is determined whether a third set time Nv2 (e.g., 15 minutes) has elapsed from the opening operation of the indoor opening / closing valve 12i. When the room temperature decrease amount ΔT per unit time is equal to or more than the decrease amount threshold or when the third set time Nv2 has elapsed from the opening operation of the indoor opening / closing valve 12i (Step ST35: YES), the process proceeds to Step ST36. When the room temperature decrease amount ΔT per unit time is less than the decrease amount threshold and when the third set time Nv2 has not elapsed from the opening operation of the indoor opening / closing valve 12i (Step ST35: NO), the process proceeds to Step ST31.

[0050] In Step ST36, closing operation of the indoor opening / closing valve 12i is performed, the indoor opening / closing valve control processing is ended, the process returns to the indoor terminal unit specification processing in FIG. 3, and the processing in Step ST22 is carried out.

[0051] In Step ST22 in FIG. 3, the processing flag Fi of the indoor terminal unit 4i is set to "2" and the indoor terminal unit 4i is set such that the indoor terminal unit 4i has already been subjected to the freeze prevention processing.

[0052] Then, in Step ST23, the outdoor air temperature To detected by the outdoor air temperature sensor 22 is read.

[0053] Then, in Step ST24, it is determined whether the outdoor air temperature To is equal to or less than the predetermined temperature Tos. In this determination, when the outdoor air temperature To is equal to or less than the predetermined temperature Tos (Step ST24: YES), the process proceeds to Step ST17, and when the outdoor air temperature To exceeds the predetermined temperature Tos (Step ST24: NO), the process proceeds to Step ST25.

[0054] In Step ST25, the drive of the pump 15 is stopped, and then the process returns to the main routine in FIG. 2, so that the processing of the main routine ends.[Action of freeze prevention control method of heat pump-type hot-water heating device]

[0055] Next, the action of the freeze prevention control performed by the freeze prevention control means 26 in the heat pump-type hot-water heating device 1 is described with reference to FIGS. 2 to 4.

[0056] When the outdoor air temperature To has become equal to or less than the predetermined temperature Tos, at least one of the water temperatures Twi of the plurality of indoor terminal units 4i where the operation stops is equal to or less than the predetermined water temperature Tw2 (Step ST14 in FIG. 3: YES) or when at least one of the room temperatures Tki of the rooms 3i is equal to or less than the predetermined room temperature Tks (Step ST16 in FIG. 3: YES), the indoor opening / closing valve 12i of the relevant indoor terminal unit 4i is opened so that water flows to the indoor terminal unit 4i (Step ST30 in FIG. 4). For example, when the water temperature Twa of the first indoor terminal unit 4a of this embodiment is equal to or less than the predetermined water temperature Tw2, the room temperature Tkb of the second indoor terminal unit 4b is equal to or less than the predetermined room temperature Tks, and the water temperature Twc of the third indoor terminal unit 4c exceeds the predetermined water temperature Tw2 and the room temperature Tkc also exceeds the predetermined room temperature Tks, the first indoor opening / closing valve 12a of the first indoor terminal unit 4a and the second indoor opening / closing valve 12b of the second indoor terminal unit 4a are opened and the freeze prevention control is performed for the third set time Nv2. By performing the freeze prevention control as described above, even when the outdoor air temperature To is equal to or less than the predetermined temperature Tos, water circulates to the first water circulation circuit 16 and the second water circulation circuit 17, and therefore the water in the water circulation circuits can be prevented from freezing. The third room 3c, in which the heating operation is stopped and the room temperature Tkc exceeds the predetermined room temperature Tks, is supposed to be set to a room temperature where people do not feel cold, and the freeze prevention control of the third indoor opening / closing valve 12c installed in the third room 3c is not performed and the decrease in the room temperature of the third room 3c is suppressed, and therefore a feeling of discomfort is not given to people using the third room 3c.

[0057] When there are two or more of the indoor terminal units 4i where the freeze prevention control is performed, the freeze prevention control is performed to the two or more of the indoor terminal units 4i one by one in turn (repeat Step ST17 to Step ST24 in FIG. 3). Thus, a significant decrease in the room temperature of a specific room among the first room 3a to the third room 3c can be suppressed and the comfort of users in the first room 3a to the third room 3c can be maintained. The freeze prevention control is performed to the two or more of the indoor terminal units 4i one by one in turn, and therefore the number of rooms where the temperature decreases can be minimized.

[0058] When the freeze prevention control is performed to the two or more of the indoor terminal units 4i in turn, the freeze prevention control is preferentially performed in turn from the indoor terminal unit with the lowest water temperature Twi or the indoor terminal unit with the lowest room temperature Tki (Step ST19 in FIG. 3). For example, in a case where the water temperature Twa of the first indoor terminal unit 4a and the water temperature Twb of the second indoor terminal unit 4b of this embodiment are equal to or less than the predetermined water temperature Tw2, when the water temperature Twa of the first indoor terminal unit 4a is lower than the water temperature Twb of the second indoor terminal unit 4b, the freeze prevention control of the first indoor terminal unit 4a is first started. Thus, the freeze prevention control is preferentially performed to the first water circulation circuit 16 having a risk of freezing, and therefore freezing can be reliably prevented.

[0059] Even when the outdoor air temperature To is equal to or less than the predetermined temperature Tos, the freeze prevention control is not performed when the water temperature Twa of the first indoor terminal unit 4a, the water temperature Twb of the second indoor terminal unit 4b, the water temperature Twc of the third indoor terminal unit 4c, and the water temperature Twd of the water-refrigerant heat exchanger 7 exceed the predetermined water temperature Tw1 that is the water temperature having a possibility of freezing (Step ST10: NO in FIG. 2). Thus, even when the outdoor air temperature is low, the freeze prevention control is not performed when the water temperature is high and there is less risk of freezing. Therefore, the decrease in the room temperatures of the first room 3a to the third room 3c is suppressed, so that the comfort of users in the first room 3a to the third room 3c can be maintained.

[0060] Further, when the decrease amount per unit time of the room temperature of the room 3i where the indoor terminal unit 4i, to which the freeze prevention control is performed, is installed has become equal to or more than the decrease amount threshold, the freeze prevention control is stopped (Step ST35 and Step ST36 in FIG. 4) and when the room temperature of the room 3i sharply decreases, the freeze prevention control is stopped, and thus a further decrease in the room temperature of the room 3i can be prevented and the comfort of a user in the room 3i can be maintained.

[0061] Further, before the freeze prevention control is performed, the first indoor opening / closing valve 12a of the first indoor terminal unit 4a, the first indoor opening / closing valve 12b of the second indoor terminal unit 4b, and the third indoor opening / closing valve 12c of the third indoor terminal unit 4c are opened and the drive control of the pump 15 is performed during the second set time Nv1, so that water is circulated throughout the first water circulation circuit 16 to the third water circulation circuit 18 (Step ST4 to Step ST7 in FIG. 2). Thus, even when a place having a risk of freezing arises in places other than places where the water temperatures are detected by the water temperature sensors 20a to 20c among the first water circulation circuit 16 to the third water circulation circuit 18, the risk of freezing can be reliably avoided.

[0062] Although this embodiment describes the heat pump-type hot-water heating device 1 having the water-refrigerant heat exchanger 7 exchanging heat between water and a refrigerant, the same effects can be obtained even when water is heated by a boiler in place of the water-refrigerant heat exchanger 7.

[0063] Further, although this embodiment describes that, when at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2, the freeze prevention control is performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks and when all of the water temperature Twa, the water temperature Twb, and the water temperature Twc exceed the predetermined water temperature Tw2 and at least one of the room temperatures Tka, Tkb, Tkc is equal to or less than the predetermined room temperature Tks, the freeze prevention control is performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks, the present invention is not limited thereto. For example, the freeze prevention control may be performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the room temperature Tki is equal to or less than the predetermined room temperature Tks, regardless of whether at least one of the water temperature Twa, the water temperature Twb, and the water temperature Twc is equal to or less than the predetermined water temperature Tw2. Alternatively, the freeze prevention control may be performed to the indoor opening / closing valve 12i corresponding to the indoor terminal unit 4i where the water temperature Twi is equal to or less than the predetermined room temperature Tks and the room temperature Tki is equal to or less than the predetermined room temperature Tks.

[0064] Further, although this embodiment describes that, when there are two or more of the indoor terminal units 4i to which the freeze prevention control is performed, the freeze prevention control is performed to the two or more of the indoor terminal units 4i one by one in turn, the freeze prevention control may be performed to the two or more of the indoor terminal units 4i at a time for the two or more of the indoor terminal units 4i. For example, when there are four or more of the indoor terminal units 4i, two indoor terminal units of the indoor terminal unit with the lowest water temperature Twi and the indoor terminal unit with the second lowest water temperature Twi are specified as the indoor terminal units to which the freeze prevention control is preferentially performed, and the freeze prevention control may be performed to the two indoor terminal units at a time.Reference Signs List

[0065] 1: heat pump-type hot-water heating device 2: outdoor unit 3a: first room 3b: second room 3c: third room 4a: first indoor terminal unit 4b: second indoor terminal unit 4c: third indoor terminal unit 5: compressor 6: four-way valve 7: water-refrigerant heat exchanger 8: expansion valve 9: outdoor heat exchanger 10: refrigerant circuit 12a: first indoor opening / closing valve 12b: second indoor opening / closing valve 12c: third indoor opening / closing valve 13a: first indoor heat exchanger 13b: second indoor heat exchanger 13c: third indoor heat exchanger 15: pump 16: first water circulation circuit 17: second water circulation circuit 18: third water circulation circuit 19a: first room temperature sensor 19b: second room temperature sensor 19c: third room temperature sensor 20a: first water temperature sensor 20b: second water temperature sensor 20c: third water temperature sensor 21: fourth water temperature sensor 22: outdoor air temperature sensor 25: control means 26: freeze prevention control means

Examples

Embodiment Construction

[0010]Next, embodiments according to the present invention are described with reference to the drawings. The embodiments described below exemplify devices or methods for embodying the technical idea of the present invention. The technical idea of the present invention does not specify the materials, shapes, structures, arrangement, and the like of constituent components to the materials, shapes, structures, arrangement, and the like described below. The technical idea of the present invention can be variously altered in the technical scope defined by claims.

[Heat pump-type hot-water heating device]

[0011]FIG. 1 is a circuit diagram illustrating a heat pump-type hot-water heating device 1 of a first embodiment according to the present invention.

[0012]The heat pump-type hot-water heating device 1 includes an outdoor unit 2 and a plurality of indoor terminal units 4a, 4b, 4c (referred to as a first indoor terminal unit 4a, a second indoor terminal unit 4b, a third indoor terminal unit 4...

Claims

1. A hot water heating device comprising: a water circulation circuit where a heat source unit configured to heat water, a pump, a plurality of indoor terminal units and a plurality of opening / closing valves connected in parallel to the heat source unit are connected by a pipe and where water circulates between the plurality of indoor terminal units and the heat source unit; an outdoor air temperature detection means configured to detect an outdoor air temperature; a plurality of terminal unit water temperature detection means configured to detect a terminal unit water temperature, the terminal unit water temperature being a temperature of water that has passed through each of the plurality of indoor terminal units; a plurality of room temperature detection means configured to detect a room temperature of a room where each of the plurality of indoor terminal units is installed; and a freeze prevention control means configured to perform freeze prevention control by opening the opening / closing valve corresponding to the indoor terminal unit where operation stops by closing the corresponding opening / closing valve to make water flow to the indoor terminal unit; wherein the freeze prevention control means is configured such that, when the outdoor air temperature is equal to or less than a predetermined temperature, the freeze prevention control means performs the freeze prevention control to the opening / closing valve corresponding to the indoor terminal unit satisfying at least one of states in which the terminal unit water temperature of water that has passed through the indoor terminal unit is equal to or less than a first water temperature and in which the room temperature of the room where the indoor terminal unit is installed is equal to or less than a predetermined temperature among the indoor terminal units where the operation stops.

2. The hot water heating device according to claim 1, wherein the freeze prevention control means is configured such that, when there are two or more of the indoor terminal units to which the freeze prevention control is performed, the freeze prevention control means performs the freeze prevention control to the two or more of the indoor terminal units in turn.

3. The hot water heating device according to claim 2, wherein, for the two or more of the indoor terminal units to which the freeze prevention control is performed, the freeze prevention control means is configured to preferentially perform the freeze prevention control in turn from the indoor terminal unit where the terminal unit water temperature is lowest, the terminal unit water temperature being a temperature of water that has passed through the indoor terminal unit, or the indoor terminal unit where the room temperature of the room where the indoor terminal unit is installed is lowest.

4. The hot water heating device according to any one of claims 1 to 3, comprising: a heat source unit water temperature detection means configured to detect a heat source unit water temperature, the heat source unit water temperature being a temperature of water that has passed through the heat source unit, wherein the freeze prevention control means is configured to perform the freeze prevention control when at least one of the heat source unit water temperature and the terminal unit water temperatures of the plurality of indoor terminal units is equal to or less than a second water temperature, the second water temperature being a temperature equal to or less than the first water temperature, during stop of heating operation of all of the indoor terminal units.

5. The hot water heating device according to any one of claims 1 to 3, wherein the freeze prevention control means is configured to stop the freeze prevention control when a decrease amount per unit time of the room temperature of the room where the indoor terminal unit, to which the freeze prevention control is performed, is installed has become equal to or more than a decrease amount threshold.

6. The hot water heating device according to any one of claims 1 to 3, wherein the freeze prevention control means is configured to perform, before performing the freeze prevention control, drive control of the pump by opening the opening / closing valves of all of the indoor terminal units for a predetermined period of time.

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