JP7655336B2 - Hot water heating system - Google Patents

Description

The present invention relates to a hot water heating device that prevents freezing of a water circulation circuit that supplies water to multiple indoor terminal units during cold seasons.

There is a hot water heating system that provides heating by circulating water heated by a heat source unit to multiple indoor terminal units installed in multiple rooms. In this hot water heating system, if any of the indoor terminal units are not operating during the cold season, there is a risk that the water in the piping of the water circulation circuit, which is the path through which water flows to the indoor terminal units, will freeze.

The hot water heating device in Patent Document 1 has a heat source unit that heats water, a pump, multiple indoor terminal units that are connected in parallel to the heat source unit, and a water circulation circuit to which on-off valves are connected by piping. In Patent Document 1, when the heating operation of all indoor terminal units is stopped and the outside air temperature falls below a predetermined temperature (e.g., 3°C), the pump is operated and the on-off valves of all indoor terminal units are opened one by one or multiple by one in sequence, causing water to flow throughout the water circulation circuit and preventing the water in the piping of the water circulation circuit from freezing.

JP 2003-240381 A

The hot water heating device in Patent Document 1 prevents freezing by flowing water through all indoor terminal units when the outside air temperature falls below a predetermined temperature, so low-temperature water also flows through indoor terminal units installed in rooms where the room temperature is low enough that people do not feel cold. If low-temperature water flows through the indoor terminal unit in such a room, the room temperature will drop, and there is a risk that it will become so high that people will feel cold.

The present invention was made to solve these problems, and aims to provide a hot water heating device that prevents the water circulation circuit from freezing when the outside air temperature falls below a specified temperature, while at the same time suppressing the drop in room temperature when the room temperature is low enough that people do not feel cold.

One aspect of the invention is a hot water heating device that includes a water circulation circuit in which a heat source unit that heats water, a pump, a plurality of indoor terminal units that are connected in parallel to the heat source unit, and a plurality of on-off valves are connected by piping, and water circulates between the plurality of indoor terminal units and the heat source unit; outdoor air temperature detection means that detects outdoor air temperature; a plurality of terminal unit water temperature detection means that detects the terminal unit water temperature, which is the temperature of the water flowing through each of the plurality of indoor terminal units; a plurality of room temperature detection means that detects the room temperature of the room in which each of the plurality of indoor terminal units is installed; and anti-freeze control means that closes the corresponding on-off valve to open the on-off valve corresponding to the indoor terminal unit that is not operating, and flows water into the indoor terminal unit to perform anti-freeze control, and the anti-freeze control means performs anti-freeze control on the on-off valve corresponding to the indoor terminal unit that is not operating and satisfies at least one of the following conditions when the outdoor air temperature is below a predetermined temperature: the terminal unit water temperature of the flowing water is below a first water temperature, and the room temperature of the room in which the terminal unit is installed is below a predetermined temperature.

The hot water heating device of the present invention can prevent the water circulation circuit from freezing when the outside air temperature falls below a specified temperature, while at the same time suppressing the drop in room temperature in a room where the temperature is low enough that people do not feel cold.

1 is a circuit diagram showing a heat pump type hot water heating device according to the present invention. 4 is a flowchart showing a main routine of anti-freeze control performed by the heat pump type hot water heating device according to the present invention. 3 is a flowchart showing a specific operation of the anti-freezing specific process in the flowchart of FIG. 2 . 4 is a flowchart showing a specific operation of the indoor opening/closing valve control process in the flowchart of FIG. 3 .

Next, an embodiment of the present invention will be described with reference to the drawings. The embodiments shown below are examples of devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, shapes, structures, arrangements, etc. of the components to be described below. The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims.
[Heat pump type hot water heating system]

Figure 1 is a circuit diagram showing a heat pump type hot water heating device 1 according to a first embodiment of the present invention.

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

The outdoor unit 2 includes a compressor 5, a four-way valve 6, a water-refrigerant heat exchanger 7 that exchanges heat between water and a refrigerant, an expansion valve 8, and an outdoor heat exchanger 9. The outdoor unit 2 also includes a pump 15 and a fourth water temperature sensor 21, which will be described later. The water-refrigerant heat exchanger 7 corresponds to the heat source unit of the present invention.

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 connected in sequence by piping to form a first water circulation circuit 16. The first indoor terminal unit 4a also 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 disposed between the pump 15 and the first indoor heat exchanger 13a of the first water circulation circuit 16 to detect the temperature of the water that has passed through the first indoor heat exchanger 13a.

The second indoor terminal unit 4b has a second indoor opening/closing valve 12b and a second indoor heat exchanger 13b. In addition, one end of the 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, and 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. As a result, a second water circulation circuit 17 is formed in which the pump 15, the water-refrigerant heat exchanger 7, the second indoor opening/closing valve 12b, and the second indoor heat exchanger 13b are connected in sequence by piping. The second indoor terminal unit 4b also 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 disposed between the pump 15 of the second water circulation circuit 17 and the second indoor heat exchanger 13b, and detects the temperature of the water that has passed through the second indoor heat exchanger 13b.

The third indoor terminal unit 4c has a third indoor opening/closing valve 12c and a third indoor heat exchanger 13c. In addition, one end of the 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, and 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. As a result, a third water circulation circuit 18 is formed in which the pump 15, the water-refrigerant heat exchanger 7, the third indoor opening/closing valve 12c, and the third indoor heat exchanger 13c are connected in sequence by piping. The third indoor terminal unit 4c also 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 disposed between the pump 15 of the third water circulation circuit 18 and the third indoor heat exchanger 13c, and detects the temperature of the water passing through the third indoor heat exchanger 13c.

As a result, 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.
Furthermore, a fourth water temperature sensor 21 is disposed between the water-refrigerant heat exchanger 7 of the first water circulation circuit 16 and the first indoor on-off valve 12a, for detecting the temperature of the water that passes through the water-refrigerant heat exchanger 7 and before it branches into the second water circulation circuit 17 and the third water circulation circuit 18. And, an outside air temperature sensor 22 is disposed outside the room, for detecting the outside air temperature.

The first indoor terminal unit 4a to the third indoor terminal unit 4c correspond to the indoor terminal unit of the present invention, and the first water circulation circuit 16 to the third water circulation circuit 18 correspond to the water circulation circuit 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, and the outdoor air temperature sensor 22 corresponds to the outdoor air temperature detection means of the present invention.

When the first indoor on-off 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, water is supplied to the first indoor heat exchanger 13a of the first indoor terminal unit 4a, and water returns from the first indoor heat exchanger 13a to the water-refrigerant heat exchanger 7. Similarly, when the second indoor on-off 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, water is supplied to the second indoor heat exchanger 13b of the second indoor terminal unit 4b, and 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 opens and the pump 15 is driven, water circulates through the third water circulation circuit 18, water is supplied to the third indoor heat exchanger 13c of the third indoor terminal unit 4c, and water returns from the third indoor heat exchanger 13c to the water-refrigerant heat exchanger 7.
In addition, 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 the first water circulation circuit 16, the second water circulation circuit 17, and the third water circulation circuit 18, and 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 water returns to the water-refrigerant heat exchanger 7 from these first indoor heat exchangers 13a to third indoor heat exchangers 13c.

The heat pump type hot water heating device 1 of this embodiment is equipped with a control means 25 that controls each device. That is, the control means 25 performs various controls 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 control of the expansion valve 8, drive control of the pump 15, and opening and closing control of the first indoor opening and closing valve 12a to the third indoor opening and closing valve 12c, based on the detection 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 outside air temperature sensor 22. The control means 25 also includes a timer unit that measures time, and a memory unit that stores the control program for the heat pump type hot water heating device 1.

The control means 25 of the heat pump hot water heating device 1 of this embodiment has a freeze prevention control means 26, as shown in FIG. 1. The freeze prevention control means 26 can be realized by software as a function of the control means 25.

In the heat pump type hot water heating device 1 of this embodiment, when 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 is stopped, the anti-freeze control is automatically started. Note that the first indoor opening/closing valve 12a of the first indoor terminal unit 4a, the second indoor terminal unit 4b, and the third indoor opening/closing valve 12 of the third indoor terminal unit 4c are closed when the heating operation is stopped.
[Anti-freeze control]

Next, the anti-freeze control performed by the anti-freeze control means 26 in the heat pump hot water heating device 1 of this embodiment will be described with reference to Figures 2 to 4. Figure 2 shows the main routine of the anti-freeze control, Figure 3 shows the indoor terminal device identification process included in the main routine of Figure 2, and Figure 4 shows the indoor opening/closing valve control process included in the indoor terminal device identification process of Figure 3.

First, in step ST1 of FIG. 2, it is determined whether the stop time (pump stop time) PT of the pump 15 is equal to or longer than a first set time PTs (e.g., 3 hours). Here, the first set time PTs is set to a time at which it is considered that the water in the water circulation circuit will not freeze even if anti-freeze control is not performed. If this determination shows that the pump stop time PT is equal to or longer than the first set time PTs (step ST1: YES), the process proceeds to step ST2, and if the pump stop time PT is shorter than the first set time PTs (step ST1: NO), step ST1 is repeated. In step ST2, the outside air temperature To detected by the outside air temperature sensor 22 is read.

Next, in step ST3, it is determined whether the outside air temperature To is equal to or lower than a predetermined temperature Tos (e.g., 5°C). Here, the predetermined temperature Tos is set to a temperature at which the water in the water circulation circuit is not expected to freeze. If this determination shows that the outside air temperature To is equal to or lower than the predetermined temperature Tos (step ST3: YES), the process proceeds to step ST4, and if the outside air temperature To is higher than the predetermined temperature Tos (step ST3: NO), the process proceeds to step ST1. In step ST4, the operation of the pump 15 is started.

Next, in step ST5, 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 opened.

Next, in step ST6, it is determined whether or not a second set time Nv1 (e.g., 15 minutes) has elapsed since the opening operation of the first indoor on-off valve 12a to the third indoor on-off valve 12c. Here, the second set time Nv1 is set to a time sufficient for a local drop in temperature in the water circulation circuit to be eliminated. Note that the second set time Nv1 corresponds to a predetermined time during which the freeze prevention control means in the present invention opens the on-off valves of all indoor terminal units and controls the drive of the pump before performing freeze prevention control.
If the second set time Nv1 has elapsed (step ST6: YES), the process proceeds to step ST7, and if the second set time Nv1 has not elapsed (step ST6: NO), ST6 is repeated. In step ST7, the first indoor opening/closing valve 12a to the third indoor opening/closing valve 12c are closed.

Next, in step ST8, 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 are read. Next, in step ST9, the water temperature Twd detected by the fourth water temperature sensor 21 is read. Note that the water temperatures Twa, Twb, and Twc correspond to the terminal device water temperature of the present invention, and the water temperature Twd corresponds to the heat source device water temperature of the present invention.

Next, in step ST10, it is determined whether at least one of the water temperatures Twa, Twb, Twc, and Twd is equal to or lower than a predetermined water temperature Tw1. Here, the predetermined water temperature Tw1 is a temperature that is determined taking into consideration the possibility of water freezing, and is set to, for example, 0°C, which is the freezing point of water. In addition, in order to further reduce the possibility of water freezing, the predetermined water temperature Tw1 may be set to 2°C above the freezing point of water, which provides a margin of error for water freezing. The predetermined water temperature Tw1 corresponds to the second water temperature of the present invention.

If it is determined in step ST10 that at least one of the water temperatures Twa, Twb, Twc, and Twd is equal to or lower than the predetermined water temperature Tw1 (step ST10: YES), the process proceeds to step ST11. If all of the water temperatures Twa, Twb, Twc, and Twd are higher than the predetermined water temperature Tw1 (step ST10: NO), the main routine ends.

In step ST11, the anti-freeze specific process shown in Figure 3 is performed.

In the freeze prevention specific process in Fig. 3, the subscript i of the process flag Fi is one of a, b, and c. That is, the process flag Fa indicates the process flag of the first indoor terminal unit 4a, the process flag Fb indicates the process flag of the first indoor terminal unit 4b, and the process flag Fc indicates the process flag of the third indoor terminal unit 4c (hereinafter, the subscript i may be used to indicate the water temperatures Twa, Twb, and Twc as the water temperatures Twi, the first indoor terminal unit 4a to the third indoor terminal unit 4c as the indoor terminal unit 4i, the room temperatures Tka, Tkb, and Tkc as the room temperatures Tki, the first indoor opening/closing valve 12a to the third indoor opening/closing valve 12c as the indoor opening/closing valve 12i, the first room temperature sensor 19a to the third room temperature sensor 19c as the room temperature sensor 19i, and the first room 3a to the third room 3c as the room 3i). Fa="0" indicates that the first indoor terminal unit 4a has not undergone antifreeze processing, Fa="1" indicates that the first indoor terminal unit 4a has not yet undergone antifreeze processing, and Fa="2" indicates that the first indoor terminal unit 4a has undergone antifreeze processing. The processing flag Fb is the processing flag of the second indoor terminal unit 4b, Fb="0" indicates that the second indoor terminal unit 4b has not undergone antifreeze processing, Fb="1" indicates that the second indoor terminal unit 4b has not yet undergone antifreeze processing, and Fb="2" indicates that the second indoor terminal unit 4b has undergone antifreeze processing. The processing flag Fc is the processing flag of the third indoor terminal unit 4c, Fc="0" indicates that the third indoor terminal unit 4c has not undergone antifreeze processing, Fc="1" indicates that the third indoor terminal unit 4c has not yet undergone antifreeze processing, and Fc="2" indicates that the third indoor terminal unit 4c has undergone antifreeze processing. In this antifreeze specific process, in step ST12 of FIG. 3, the process flags Fa, Fb, and Fc are set to "0."

Next, 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.

Next, 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 lower than the predetermined water temperature Tw2. If at least one of the water temperatures Twa, Twb, and Twc is equal to or lower than the predetermined water temperature Tw2 (step ST14: YES), the process proceeds to step ST15. If all of the water temperatures Twa, Twb, and Twc are higher than the predetermined water temperature Tw2 (step ST14: NO), the process proceeds to step ST16. Here, the predetermined water temperature Tw2 is a temperature determined in consideration of the possibility of water freezing, and may be the same temperature as the predetermined water temperature Tw1, or may be a temperature with a larger margin than the predetermined water temperature Tw1. In other words, the predetermined water temperature Tw1 is a temperature equal to or lower than the predetermined water temperature Tw2. The predetermined water temperature Tw2 corresponds to the first water temperature in the present invention.

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 lower than a predetermined room temperature Tks. Note that the predetermined room temperature Tks corresponds to a predetermined temperature that is 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 in order for the freeze prevention control means in the present invention to determine the indoor opening/closing valve for performing freeze prevention control.
If this determination indicates that at least one of the room temperatures Tka, Tkb, and Tkc is below the predetermined room temperature Tks (step ST16: YES), the process proceeds to step ST15. If all of the room temperatures Tka, Tkb, and Tkc are above the predetermined room temperature Tks (step ST16: NO), the process proceeds to step ST25.

In step ST15, the processing flag Fi of the indoor terminal unit 4i whose water temperature Twi is equal to or lower than the predetermined room temperature Tks, or whose room temperature Tki is equal to or lower than the predetermined room temperature Tks, is set to "1". Specifically, in step ST14, if at least one of the water temperatures Twa, Twb, and Twc is equal to or lower than the predetermined water temperature Tw2 and the process proceeds to step ST15, the processing flag Fi of the indoor terminal unit 4i whose water temperature Twi is equal to or lower than the predetermined room temperature Tks is set to "1". In addition, in step ST16, if at least one of the room temperatures Tka, Tkb, and Tkc is equal to or lower than the predetermined room temperature Tks and the process proceeds to step ST15, the processing flag Fi of the indoor terminal unit 4i whose room temperature Tki is equal to or lower than the predetermined room temperature Tks is set to "1".

Next, in step ST17, it is determined whether at least one of the processing flags Fa of the first indoor terminal unit 4a, Fb of the second indoor terminal unit 4b, and Fc of the third indoor terminal unit 4c is "1". If this determination indicates that at least one of the processing flags Fa, Fb, and Fc is "1" (step ST17: YES), the process proceeds to step ST18. On the other hand, if none of the processing flags Fa, Fb, and Fc is "1", i.e., if all of the processing flags Fa, Fb, and Fc are "0" or "2" (step ST17: NO), the process proceeds to step ST25.

In step ST18, it is determined whether or not there are multiple processing flags Fa, Fb, Fc set to "1." If there are multiple processing flags Fa, Fb, Fc set to "1" (step ST18: YES), the process proceeds to step ST19. If there is only one processing flag Fa, Fb, Fc set to "1" (step ST18: NO), the process proceeds to step ST20.

In step ST19, when there are multiple indoor terminal units 4i that should undergo antifreeze processing, the indoor terminal unit that will undergo antifreeze processing is identified as the one that will undergo antifreeze processing with priority. In step ST14, if at least one of the water temperatures Twa, Twb, and Twc is equal to or lower than the predetermined water temperature Tw2 and the process proceeds to step ST15, the indoor terminal unit 4i with the lowest water temperature Twi among the multiple indoor terminal units is identified as the indoor terminal unit that will undergo antifreeze processing with priority. In addition, in step ST16, if at least one of the room temperatures Tka, Tkb, and Tkc is equal to or lower than the predetermined room temperature Tks and the process proceeds to step ST15, the indoor terminal unit 4i with the lowest room temperature Tki among the multiple indoor terminal units is identified as the indoor terminal unit that will undergo antifreeze processing with priority.

On the other hand, in step ST20, since there is only one indoor terminal unit 4i that should undergo anti-freezing processing, that indoor terminal unit is identified as the indoor terminal unit that will be given priority for performing anti-freezing processing.

Next, in step ST21, the indoor opening/closing valve control process shown in FIG. 4 is performed.

In this indoor on-off valve control process, first, in step ST30 of FIG. 4, the indoor on-off valve 12i of the identified indoor terminal unit 4i is opened to allow water to flow through the indoor terminal unit 4i.

Next, in step ST31, the room temperature Tki detected by the room temperature sensor 19i of the specified indoor terminal unit 4i is read. Next, in step ST32, it is determined whether a predetermined room temperature measurement time n1 (for example, 60 seconds) has elapsed since the room temperature Tki was read. If the room temperature measurement time n1 has elapsed (step ST32: YES), the process proceeds to step ST33, and if 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. Next, in step ST34, the amount of room temperature decrease from the room temperature Tki ₀ at the start of measurement to the current room temperature Tki _n is calculated, and this amount of room temperature decrease is divided by the room temperature measurement time n1 to calculate the amount of room temperature decrease ΔT per unit time.

Next, in step ST35, it is determined whether the amount of room temperature drop ΔT per unit time is equal to or greater than the drop threshold, or whether the third set time Nv2 (e.g., 15 minutes) has elapsed since the opening operation of the indoor opening/closing valve 12i. If the amount of room temperature drop ΔT per unit time is equal to or greater than the drop threshold, or the third set time Nv2 has elapsed since the opening operation of the indoor opening/closing valve 12i (step ST35: YES), the process proceeds to step ST36. If the amount of room temperature drop ΔT per unit time is less than the drop threshold, and the third set time Nv2 has not elapsed since the opening operation of the indoor opening/closing valve 12i (step ST35: NO), the process proceeds to step ST31.

In step ST36, the indoor opening/closing valve 12i is closed, and then the indoor opening/closing valve control process is terminated and the process returns to the indoor terminal device identification process in FIG. 3, where the process of step ST22 is executed.

In step ST22 of FIG. 3, the processing flag Fi of the indoor terminal unit 4i is set to "2," and the indoor terminal unit 4i is deemed to have completed the anti-freeze processing.

Next, in step ST23, the outside air temperature To detected by the outside air temperature sensor 22 is read.

Next, in step ST24, it is determined whether the outside air temperature To is equal to or lower than a predetermined temperature Tos. If this determination determines that the outside air temperature To is equal to or lower than the predetermined temperature Tos (step ST24: YES), the process proceeds to step ST17, and if the outside air temperature To is higher than the predetermined temperature Tos (step ST24: NO), the process proceeds to step ST25.

In step ST25, the driving of the pump 15 is stopped, and then the process returns to the main routine of FIG. 2, whereupon the process of the main routine ends.
[Function of the anti-freezing control method for a heat pump type hot water heating device]

Next, the operation of the anti-freeze control performed by the anti-freeze control means 26 in the heat pump hot water heating device 1 will be described with reference to Figures 2 to 4.

When the outside air temperature To falls below a predetermined temperature Tos, if at least one of the water temperatures Twi of the multiple indoor terminal units 4i that are not operating is below a predetermined water temperature Tw2 (step ST14 in Figure 3: YES), or at least one of the room temperatures Tki of the rooms 3i is below a predetermined room temperature Tks (step ST16 in Figure 3: YES), the indoor opening/closing valve 12i of the corresponding indoor terminal unit 4i opens and water flows into the indoor terminal unit 4i (step ST30 in Figure 4). For example, in this embodiment, when the water temperature Twa of the first indoor terminal unit 4a is equal to or lower than the predetermined water temperature Tw2, the room temperature Tkb of the second indoor terminal unit 4b is equal to or lower than the predetermined room temperature Tks, 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 to perform anti-freezing control for the third set time Nv2. By performing anti-freezing control in this manner, even if the outside air temperature To is equal to or lower than the predetermined temperature Tos, water circulates in the first water circulation circuit 16 and the second water circulation circuit 17, so that the water in the water circulation circuit can be prevented from freezing. In addition, the heating operation is stopped, and the room temperature Tkc in the third room 3c is higher than the predetermined room temperature Tks, so it is considered that the room temperature in the third room 3c is low enough that people do not feel cold. However, the third room opening/closing valve 12c installed in the third room 3c is not subjected to anti-freeze control, and the drop in the room temperature in the third room 3c is suppressed, so people using the third room 3c do not feel uncomfortable.

Furthermore, when there are multiple indoor terminals 4i that perform anti-freeze control, the anti-freeze control is performed on each of the multiple indoor terminals 4i in sequence (steps ST17 to ST24 in FIG. 3 are repeated). In this manner, it is possible to prevent a significant drop in the room temperature of a specific room among the first room 3a to the third room 3c, and it is possible to maintain the comfort of the users in the first room 3a to the third room 3c. Furthermore, since the anti-freeze control is performed on each room in sequence, it is possible to minimize the number of rooms whose room temperatures drop.
In addition, when performing anti-freezing control for the indoor terminal units 4i in sequence, the anti-freezing control is performed in sequence starting 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 this embodiment, when the water temperature Twa of the first indoor terminal unit 4a and the water temperature Twb of the second indoor terminal unit 4b are equal to or lower than the predetermined water temperature Tw2, if 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 anti-freezing control of the first indoor terminal unit 4a is started first. In this way, the first water circulation circuit 16 that is at risk of freezing is given priority in the anti-freezing control, so that anti-freezing can be reliably performed.

Even if the outside air temperature To is equal to or lower than the predetermined temperature Tos, anti-freeze control is not performed if 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, which is the water temperature at which freezing may occur (step ST10 in FIG. 2: NO). Therefore, even if the outside air temperature is low, anti-freeze control is not performed if the water temperature is high and there is little risk of freezing. This prevents the room temperature in the first to third rooms 3a to 3c from decreasing, thereby maintaining the comfort of the users in the first to third rooms 3a to 3c.

In addition, when the rate of decrease per unit time of the room temperature of the room 3i in which the indoor terminal unit 4i performing the anti-freeze control is installed reaches or exceeds the decrease amount threshold, the anti-freeze control is stopped (steps ST35 and ST36 in FIG. 4), and when the room temperature of the room 3i drops suddenly, the anti-freeze control is stopped to prevent a further decrease in the room temperature of the room 3i, thereby maintaining the comfort of the user in the room 3i.

Furthermore, before performing anti-freeze control, 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 for the second set time Nv1 to control the operation of the pump 15, thereby circulating water throughout the first water circulation circuit 16 to the third water circulation circuit 18 (steps ST4 to ST7 in FIG. 2). This ensures that the risk of freezing can be avoided even if there are any locations among the first water circulation circuit 16 to the third water circulation circuit 18 that are at risk of freezing other than the locations where the water temperature is detected by the water temperature sensors 20a to 20c.

In this embodiment, the heat pump type hot water heating system 1 has been described as having a water-refrigerant heat exchanger 7 that exchanges heat between water and a refrigerant. However, the same effect can be obtained by heating water in a boiler instead of the water-refrigerant heat exchanger 7.
In the present embodiment, when at least one of the water temperatures Twa, Twb, and Twc is equal to or lower than the predetermined water temperature Tw2, the anti-freezing control is performed on the indoor opening/closing valve 12i corresponding to the indoor terminal unit 4i whose water temperature Twi is equal to or lower than the predetermined room temperature Tks, and when all of the water temperatures Twa, Twb, and Twc exceed the predetermined water temperature Tw2 and at least one of the room temperatures Tka, Tkb, and Tkc is equal to or lower than the predetermined room temperature Tks, the anti-freezing control is performed on the indoor opening/closing valve 12i corresponding to the indoor terminal unit 4i whose room temperature Tki is equal to or lower than the predetermined room temperature Tks, but the present invention is not limited to this. For example, regardless of whether at least one of the water temperatures Twa, Twb, and Twc is equal to or lower than the predetermined water temperature Tw2, the anti-freezing control may be performed on the indoor opening/closing valve 12i corresponding to the indoor terminal unit 4i whose room temperature Tki is equal to or lower than the predetermined room temperature Tks. Alternatively, anti-freeze control may be performed on the indoor opening/closing valve 12i corresponding to the indoor terminal unit 4i whose water temperature Twi is equal to or lower than the predetermined room temperature Tks and whose room temperature Tki is equal to or lower than the predetermined room temperature Tks.
In addition, in the present embodiment, when there are multiple indoor terminal units 4i that perform anti-freezing control, the anti-freezing control is performed for each of the multiple indoor terminal units 4i in sequence, but the anti-freezing control may be performed for multiple indoor terminal units 4i at a time. For example, when there are four or more indoor terminal units 4i, the indoor terminal unit with the lowest water temperature Twi and the indoor terminal unit with the second lowest water temperature Twi may be specified as the indoor terminal units that are given priority for anti-freezing control, and the anti-freezing control may be performed for two indoor terminal units at a time.

1 Heat pump type hot water heating device 2 Outdoor unit 3a First chamber 3b Second chamber 3c Third chamber 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 Anti-freeze control means

Claims (3)

a water circulation circuit in which a heat source unit for heating water, a pump, a plurality of indoor terminal units connected in parallel to the heat source unit, and a plurality of on-off valves are connected by piping, and water circulates between the indoor terminal units and the heat source unit;
An outside air temperature detection means for detecting an outside air temperature;
A plurality of terminal water temperature detection means for detecting the water temperatures of the plurality of indoor terminals;
a plurality of room temperature detection means for detecting room temperatures in the rooms in which the plurality of indoor terminals are installed;
and a freeze prevention control means for opening the on-off valve corresponding to the indoor terminal unit that has been stopped by closing the corresponding on-off valve, and flowing water into the indoor terminal unit to perform freeze prevention control,
the anti-freezing control means, when the outdoor temperature is equal to or lower than a predetermined temperature, performs the anti-freezing control on the on-off valve corresponding to the indoor terminal that satisfies at least one of the following conditions: the water temperature of the indoor terminal is equal to or lower than a first water temperature, and the room temperature of the room in which the indoor terminal is installed is equal to or lower than a predetermined temperature, among the indoor terminals that are stopped in operation;
When there are a plurality of indoor terminals that perform the anti-freezing control, the anti-freezing control means sequentially performs the anti-freezing control on the plurality of indoor terminals, and
The hot water heating device is characterized in that the anti-freeze control means performs the anti -freeze control on the multiple indoor terminal units performing the anti-freeze control in order of priority, starting with the indoor terminal unit with the lowest water temperature or the indoor terminal unit with the lowest room temperature in the room in which it is installed. a water circulation circuit in which a heat source unit for heating water, a pump, a plurality of indoor terminal units connected in parallel to the heat source unit, and a plurality of on-off valves are connected by piping, and water circulates between the indoor terminal units and the heat source unit;
An outside air temperature detection means for detecting an outside air temperature;
A plurality of terminal water temperature detection means for detecting the water temperatures of the plurality of indoor terminals;
a plurality of room temperature detection means for detecting room temperatures in the rooms in which the plurality of indoor terminals are installed;
a freeze prevention control means for opening the on-off valve corresponding to the indoor terminal unit that has been stopped by closing the corresponding on-off valve, and flowing water into the indoor terminal unit to perform freeze prevention control;
A heat source unit water temperature detection means for detecting the water temperature of the heat source unit is provided.
The hot water heating device is characterized in that the anti-freeze control means performs the anti-freeze control on the opening/closing valve corresponding to the indoor terminal unit that satisfies at least one of the following conditions: the water temperature of the indoor terminal unit is below the first water temperature and the room temperature of the room in which it is installed is below a predetermined temperature, when the heating operation of all of the indoor terminal units is stopped and at least one of the water temperatures of the heat source unit and the plurality of indoor terminal units is below a second water temperature that is below a first water temperature, and when the outside air temperature is below a predetermined temperature. a water circulation circuit in which a heat source unit for heating water, a pump, a plurality of indoor terminal units connected in parallel to the heat source unit, and a plurality of on-off valves are connected by piping, and water circulates between the indoor terminal units and the heat source unit;
An outside air temperature detection means for detecting an outside air temperature;
A plurality of terminal water temperature detection means for detecting the water temperatures of the plurality of indoor terminals;
a plurality of room temperature detection means for detecting room temperatures in the rooms in which the plurality of indoor terminals are installed;
and a freeze prevention control means for opening the on-off valve corresponding to the indoor terminal unit that has been stopped by closing the corresponding on-off valve, and flowing water into the indoor terminal unit to perform freeze prevention control,
When the outdoor temperature is equal to or lower than a predetermined temperature, the freeze prevention control means performs the freeze prevention control on the on-off valve corresponding to the indoor terminal that satisfies at least one of the following conditions: the water temperature of the indoor terminal is equal to or lower than a first water temperature, and the room temperature of the room in which the indoor terminal is installed is equal to or lower than a predetermined temperature, among the indoor terminals that are not in operation;
The hot water heating device is characterized in that the anti-freeze control means stops the anti-freeze control when the amount of decrease per unit time of the room temperature in the room in which the indoor terminal device performing the anti-freeze control is installed becomes equal to or greater than a decrease amount threshold.

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