JP2002295851A - Freeze proofing method of heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the freeze proofing method of a heating apparatus which has improved energy-saving properties in freeze prevention. SOLUTION: The freeze proofing method of a heating apparatus for heating by circulating heating medium water (6) to a plurality of systems of hot water terminals (2, 4, and the like) comprises the determining processing of freeze prevention operation time, a processing for determining whether heating operation is being made, a processing for determining a system requiring a freeze preventing operation, by measuring returned heating medium water temperature of each system by circulating hearing medium water for each system, when all hot water terms are not performing hearing operation, and a water passage processing for passing heating medium water at a specific temperature to each system, that is selected from systems requiring a freezing prevention operation for specific time, or until the returned heating medium water reached a specific temperature, thus improving energy-saving properties in freeze prevention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preventing freezing of a heating device such as a floor heating panel or a fan convector using heating water.

[0002]

2. Description of the Related Art Conventionally, a heating device using hot water or the like as a heat medium has
For example, as shown in FIG. 6, a hot water terminal 100 such as a floor heating panel and a cistern 102 on the side of the heat source device are connected to a circulation path 104.
And heat medium water 106 as a heat medium is connected to the hot water terminal 10.
It circulates to 0 and performs necessary heating.

[0003]

By the way, the heat source unit including the cistern 102 is often installed outdoors or the like.
Heat medium water 1 in the circulation path 104 due to cold regions or cold at night
If 06 freezes, the heating operation may not be possible. Conventionally, in order to prevent such inconvenience due to freezing, when there is a risk of freezing, control is performed to heat the heat transfer water 106 and circulate it through the circulation path 104.

[0004] However, when the operation is stopped, for example, by shutting off the power supply of the heat source unit, the control for preventing freezing also stops, and there is a disadvantage that freezing cannot be avoided. In order to prevent freezing, it is effective to use an antifreeze solution. However, if the concentration of the antifreeze solution is not adjusted, algae may be generated in the heat transfer water or the function of the antifreeze solution may be reduced to cause freezing.

A circulation path 10 for circulating the heat transfer water 106
In some cases, a temperature sensor is installed on the side of the heat source 4 or the heat source device, and the temperature sensor performs an antifreeze operation. The flowchart of FIG. 7 shows the example. In this freeze prevention control, it is determined whether or not the detected temperature of the temperature sensor is equal to or lower than 3 ° C. in step S41. If the detected temperature is equal to or lower than 3 ° C., the process proceeds to step S42 to perform heating combustion. This heating combustion burns a burner and operates a circulation pump. As a result of this heating combustion, it is determined in step S43 whether or not the detected temperature of the temperature sensor is equal to or higher than 7 ° C.
Then, the heating pump is stopped. That is, in the anti-freezing control, the operation shifts to the anti-freezing operation when the temperature detected by the temperature sensor is 3 ° C. or less, and the heating operation is performed until the detected temperature reaches 7 ° C.

In such anti-freezing control using the detected temperature of the temperature sensor as control information, the detected temperature has a large effect on the control, and when the sensitivity of the temperature sensor is low or depending on the location of the temperature sensor, the anti-freezing control is performed. Failure may occur, and reliability becomes an issue.

Meanwhile, in a heating device having a plurality of systems of hot water terminals, it is expected that the hot water terminals that are expected to freeze will vary, and there are some that have no fear of freezing.
If the anti-freezing operation is performed on all the systems of such a plurality of hot water terminals at once, a considerable loss of heat energy occurs, which is uneconomical. To prevent freezing, there are a method of heating the heat transfer water with a heater or a boiler and a method of operating a pump. However, any of these methods tends to increase energy consumption.

In a heating system for a plurality of systems of hot water terminals, when any one of the hot water terminals is in a heating operation and the temperature of the heating medium is adjusted by the temperature detected by the temperature sensor, the temperature is not frozen at the detected temperature. It is impossible to judge.

Accordingly, an object of the present invention is to provide a method for preventing freezing of a heating device in which the energy saving of freezing is improved.

[0010]

According to the method for preventing freezing of a heating device according to the present invention, the freezing of a heating device for heating by circulating a heating medium water (6) to a plurality of hot water terminals (2, 4, etc.) is performed. The prevention method, a process of determining the arrival of the time to perform the antifreeze operation, and when the time has arrived, a process of determining whether the hot water terminal is performing a heating operation, and any hot water terminal When the heating operation is not performed, the heat medium water is circulated for each system, the return heat medium water temperature of each system is measured, and a process for determining a system requiring the antifreeze operation is performed. A process of passing the heat transfer water at a predetermined temperature for a predetermined time for each system selected from necessary systems. That is, the time required for the anti-freezing operation is monitored, and based on the arrival of the time, it is determined whether or not any of the hot water terminals is performing the heating operation. this is,
This is because if the heating operation is performed, the heat transfer water can be used to prevent freezing. However, if none of the hot water terminals is performing the heating operation, freezing is expected, but since the situation is expected to be different in each system, the heating medium water is circulated for each system, The temperature of the return heat medium water is measured for each system, a system that requires a heating operation to prevent freezing is selected, and a heat medium at a predetermined temperature is passed through each system for a predetermined time to prevent freezing. ing. As described above, by selectively supplying the heating medium water, it is possible to reduce the consumption of heat energy required for the antifreezing operation, and to improve energy saving.

In the method for preventing freezing of a heating device according to the present invention, a method for preventing freezing of a heating device for heating by circulating heat transfer water to a plurality of hot water terminals, wherein the heat source device The determination as to whether or not the hot water terminal composed of a plurality of systems that receives the supply of the heat transfer water from (8) is being performed. The method includes a process of circulating the heat transfer water for a predetermined time for each system selected from each system that has not been performed. That is, when the heating operation is being performed in any of the hot water terminals, it is not possible to confirm or predict the possibility of freezing of the hot water terminal of the system in which the heating operation is not performed. When the temperature sensor installed in the circulation path is used for adjusting the temperature of the outgoing heat transfer water, the detected temperature becomes high, so that it is impossible to determine the freezing from the value. Further, if the heat transfer water, which is thermally necessary for heating, is used to prevent freezing of the system in which the heating operation is not performed, the heat energy of the heat transfer water can be reused. Therefore, if water is passed for a predetermined time to the hot water terminal for which the anti-freezing operation is required, it is possible to prevent the freezing. As a result, it is possible to reduce the consumption of heat energy required for the antifreezing operation, and to improve energy saving.

In the method for preventing freezing of a heating device according to the present invention, a method for preventing freezing of a heating device for heating by circulating heating medium water to a plurality of hot water terminals, wherein the heat source device The determination as to whether or not the hot water terminal including a plurality of systems receiving the supply of the heat transfer water is being operated, and when performing the heating operation with any of the hot water terminals, the hot water terminal is not operating. The method is characterized by including a process of circulating the heating medium water for each system selected from the respective systems and causing the temperature of the returning heating medium water to reach a predetermined temperature. That is, when the heating operation is being performed at any of the hot water terminals, the heating medium having the temperature necessary for heating is returned to the hot water terminal of the system where the heating operation is not performed, and the heating medium water temperature is reduced. Since the water is passed until the temperature reaches the predetermined temperature, the reliability of the prevention of freezing can be improved. As a result, it is possible to reduce the consumption of heat energy required for the antifreezing operation, and to improve energy saving.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention and embodiments thereof will be described below in detail with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of a method for preventing freezing of a heating device according to the present invention. In the heating device according to the present invention, a plurality of hot water terminals are installed in addition to the hot water terminal 2 which is a low-temperature required load such as a floor heating panel, the hot water terminal 4 which is a high-temperature required load such as a fan convector. In this example,
For ease of explanation, two systems of hot water terminals 2 and 4 are installed, and the heating medium 6
A heat source device 8 such as a gas water heater for supplying water is used.
The heat source for heating the heat medium water 6 includes, in addition to the combustion heat of the fuel gas,
Kerosene combustion heat, electric heat, heat pump, solar heat, etc. can be used.

In the heat source unit 8, a burner 10 as a combustion means is provided in a combustion chamber 12, and the burner 10 is provided with a fuel gas G via a valve 14, 16 or a valve 18 as a gas adjusting means or a switching means. Is supplied. Burner 10
A fan 20 as an air supply means for supplying air necessary for gas combustion is installed below the gas supply line.

The heat source unit 8 includes a heat exchanger 2 as a heating means for applying the heat of combustion of the burner 10 to the heat medium water 6.
2 is installed in the combustion chamber 12. The heat exchanger 22 is provided with a circulation path 24 as means for circulating the heat transfer water 6 to the hot water terminal 2. The circulation path 24 of this embodiment is
A circulation path 24A for circulating the low-temperature water LW to the hot water terminal 2 side;
A circulation path 24B for circulating the high-temperature water HW to the hot water terminal 4 side is constituted by these two circulation paths 24A and 24B.
Is provided with a circulation pump 26 and a cistern 28 as a heat medium water tank for storing the heat medium water 6. Circulation pump 26
For example, an AC motor or a DC motor can be used as the drive source. For example, when a DC motor is used, the number of rotations can be controlled widely.

The circulation path 24 is provided with a pipe 36 on the hot water terminal 2 side and a pipe 38 on the hot water terminal 4 side, as well as a low-temperature side pipe 30, a high-temperature side pipe 32 and a return pipe 34.
A bypass pipe 4 is provided between the hot side outgoing pipe 32 and the return pipe 34.
0 is provided, and the high-temperature water HW flows toward the return pipe 34 via the bypass pipe 40. The pipes 36, 38 are connected to the low-temperature side pipe 30,
The high temperature side outgoing pipe 32 is connected via a forward side header 44 which is a connecting means, and the return pipe 34 is connected via a return side header 46 which is a connecting means. Also, the pipe 4 has a valve 4
8. A valve 50 is installed in the pipe 38.

A temperature sensor 51 for detecting the temperature of the outgoing heat transfer medium of the low-temperature side system is provided on the low-temperature side outgoing pipe 30, and a temperature sensor 53 for detecting the temperature of the outgoing heat transfer medium water of the high-temperature side system is provided on the high-temperature side outgoing pipe 32. , Return side header 4 of piping 36, 38, 39
Temperature sensor 5 for detecting the temperature of the return heat transfer water of each system on the 6 side
5, 57 and 59 are provided.

The cistern 28 is provided with a water supply pipe 5 as a replenishing means for replenishing water W used for the heat medium water 6 from outside.
2. A valve 54 is provided as an opening / closing valve for controlling the supply. The cistern 28 is provided with level sensors 56 and 58 as means for detecting the level of the heat transfer water 6. The level sensor 56 has a low level L ₁ as a low level, and the level sensor 58 has a high level L ₂ as a high level. Are detected, and these detection results are taken out as electric signals. Further, the cistern 28 is provided with an overflow pipe 60 for discharging the heat transfer water 6 when the heat transfer water 6 has an abnormally high level.

A control unit 62 is provided as control means for performing antifreezing control, heating control, and the like.
Is constituted by a microcomputer or the like, has a CPU as arithmetic means, a ROM and a RAM as storage means, and a timer 64 as time setting means. The control unit 62 includes temperature sensors 51, 53, 5
The detection outputs of 5, 57, 59, level sensors 56, 58, etc. are input as control information, and a switch 66 is connected as instruction means for instructing antifreeze operation. The control unit 62 obtains various control outputs, and obtains control outputs for the circulation pump 26, the valves 48, 50, 54, and the like.
Control output V for actuators such as 4, 16, and 18
n is obtained. The timer 64 has a calendar function for displaying a date and a clock function for displaying time.

A remote controller 68 may be provided as another control means for such a controller 62. That is, the remote control device 68 is a remote control unit that is installed near the hot water terminals 2 and 4 and that exchanges a control signal with the control unit 62 by wire or wirelessly, and performs time control similarly to the control unit 62. A timer 70 is provided as a means for performing the operation, and a switch 72 is connected as an instruction means for instructing the anti-freezing operation. The timer 70 has a calendar function for displaying a date and a clock function for displaying time. When such a remote control device 68 is installed, the timer 64 of the control unit 62 can be omitted.

In such a heating device, in a normal heating operation, the heating medium water 6 heated by the heat exchanger 22 flows as high-temperature water HW to the pipe 38 by opening and closing the valve 50 through the high-temperature side pipe 32. While flowing to the hot water terminal 4 side, it flows to the return pipe 34 side through the bypass pipe 40 and merges with the heat transfer water 6 passing through the hot water terminal 4 side, and the cistern 28
Leads to. The heat transfer water 6 that has exited the cistern 28 is supplied to the circulation pump 2
6, branching in the directions of arrows A and B, and opening and closing the valve 48 causes the low-temperature water LW to flow to the piping 36 on the hot water terminal 2 side, circulate through the hot water terminal 2, and return to the return pipe 34. Due to the circulation of the low-temperature water LW, the heat of the low-temperature water LW is radiated through the hot water terminal 2.

In such a heating apparatus, the cistern 28 is supplied with the heating medium water 6. That is, after the pump operation is performed, when the level sensor 56 detects the low water level L ₁ of the heat medium water 6, the level sensor 58 is high level L
Water supply is performed until ₂ is detected. That is, the high water level L ₂
Is detected, the valve 54 is closed and the supply of the water W is completed.

Next, the freeze prevention control will be described with reference to the flowcharts shown in FIGS. 2 and 3, reference numerals A and B indicate connectors.

When the power is turned on, the mode shifts to the freeze prevention control mode, and the timer 64 is reset in step S1. The timer 64 sets the date and time on the calendar function and sets the start time and end time as the period or date of the antifreeze operation and the operation time in advance. When the remote control device 68 is installed, the date and time of the calendar function are set to the timer 72, and the start time and the end time are set in advance as the period or date of the antifreeze operation and the operation time. Set.

After resetting the timer, in step S2, it is determined whether or not the time until the anti-freezing operation has elapsed. If not, the process waits in step S2 until the time has elapsed. That is, in this step S2, it is determined whether or not the date and time of the anti-freezing operation set in the timer 64 or 70 have arrived. If not, the operation stops at step S2. Shifts to step S3.

After a lapse of a predetermined time, in step S3, it is determined whether or not the hot water terminals such as the hot water terminals 2 and 4 are operating. If the hot water terminals are operating, the process returns to step S1 to be operated. If not, the process proceeds to step S4.

In step S4, one of the hot water terminals 2, 4, etc.
Pump circulation is performed for each system to measure the temperature of the heat transfer water. That is, since the valves 48 and 50 are provided in the hot water terminals 2 and 4, if the valves 48 and 50 are selectively opened and closed, the temperature of the return heat medium water is measured by the temperature sensors 55, 57 and 59.
Can be measured individually. In step S5,
After storing the system to be subjected to the antifreeze operation in the RAM or the like of the control unit, the process proceeds to step S6. It is determined whether or not such processing has been completed for all the systems. If the processing has not been completed, the process returns to step S4, completes the measurement processing of each system, and proceeds to step S7.

In step S7, water is passed through each system. That is, if the valves 48 and 50 are selectively opened and the circulation pump 26 is operated, in this embodiment, the hot water terminals 2, 4
The water can be individually passed through.

Then, in step S8, heating combustion is executed, that is, after the burner 10 is burned to perform the heating operation, the process proceeds to step S9. In step S9, a heating operation is performed for a predetermined time, for example, 2 minutes at a predetermined outgoing temperature, for example, 40 ° C., and in step S10, it is determined whether or not the heating combustion in each system, that is, the heating operation has ended. After all the heating operations are completed, the process proceeds to step S11,
The operation of the circulation pump 26 is stopped, and the process returns to step S1.
That is, the heating operation as the freezing prevention operation is executed for each system.

If any of the hot water terminals is operating in step S3, for example, if the hot water terminal 2 is operating, the process proceeds to step S12, where the hot water terminal 4 of the system that is not operating is transferred to step S12. Start water flow. In this case, the valve 50 is opened to perform water passage, and the water passage time is, as shown in step S13, a predetermined time, for example, two minutes, and then the process proceeds to step S14.

In step S14, it is determined whether or not the flow of water through the system in which the hot water terminal is not operating has been completed.
After water is supplied to all the non-operating systems that require freezing prevention, the process returns to step S1.

As described above, when hot water terminals are installed in a plurality of systems, freezing is prevented by supplying water to the system where heating operation is not performed and the hot water terminals. Irrespective of this, heat loss is small, energy consumption efficiency can be increased, and economic freezing prevention can be performed, as compared to the case where the anti-freezing operation is performed.

Next, another freeze prevention control will be described with reference to the flowcharts shown in FIGS. 4 and 5
, Symbols C and D indicate connectors.

When the power is turned on, the mode shifts to the freeze prevention control mode, and in steps S21 to S31, FIG.
The same processing as the freeze prevention control shown in FIG.
If the hot water terminal is operating at 23, step S3
Move to 2. That is, in step S32, water flow is started to the hot water terminal 4 of the system that is not operating. In this case, the valve 50 is opened to perform water flow, and the water flow is performed in step S3.
As shown in FIG. 3, the return temperature is set to a predetermined temperature, for example, 30 ° C.
, And the process proceeds to step S34.

In step S34, it is determined whether or not the flow of water through the system in which the hot water terminal is not operating has been completed.
After water is supplied to all the non-operating systems that require freezing prevention, the process returns to step S21.

As described above, when the hot water terminals are installed in a plurality of systems, water is supplied to the system where the heating operation is not performed and the hot water terminals. In the above-described embodiment, time control is performed. On the other hand, in other embodiments, since the return temperature is monitored to prevent freezing, compared to the case where the antifreezing operation is performed regardless of the presence or absence of the heating operation, the heat loss is small,
Energy consumption efficiency can be improved, and economic freezing prevention can be performed.

The period and time required for such an antifreeze operation are set in advance in the timer 64 or 70. If it is confirmed by the switch 66 or the switch 72 whether or not the antifreeze operation instruction is issued, The antifreeze operation can be selected, and malfunction can be prevented when an error occurs in the time setting. Then, heating combustion is performed according to the arrival of the period and time, so that the freeze prevention management becomes easy.

By the way, in the anti-freezing control, the respective operation patterns will be summarized and explained. When the temperature sensors 51 and 53 for detecting the temperature of the outgoing heat medium are used, and for detecting the temperature of the return heat medium water. In some cases, the temperature sensors 55, 57, 59, etc. are used. The former includes, firstly, when the hot water terminals of all the systems are not operating, and secondly, some of the hot water terminals in all the systems. Thirdly, there is an operation pattern when the hot water terminals of all the systems are operating.

A When all the hot water terminals are not operating After a predetermined time set in the timer 64 or the timer 70 elapses, the control output from the control unit 62 of the heat source unit 8 causes the circulation path 24 of the heat medium water 6 to pass. Can be opened for each system, that is, in this case, since each system can be selectively selected by the valves 48 and 50, the heat medium water 6 is circulated one system at a time,
Measure the temperature. That is, by opening the valve 48, the temperature sensor 55 measures the temperature of the return heat medium on the pipe 36 side, and by opening the valve 50, the temperature sensor 57 measures the temperature of the return heat medium water on the side of the pipe 38. If a detected temperature that requires freezing prevention is measured based on such a temperature detection, the antifreezing operation is performed, and after that, the timer 64 is reset. In this case, for example, the heating medium water 6 of the heat source unit 8 can be used for additional heating of the bath through another heat exchanger. If the combustion of the burner 10 is stopped, the temperature sensor 51 on the outgoing side can be used. Since the temperature of the return heat medium water can be detected even with 53, the measurement of the temperature of the return heat medium water is not limited to the temperature sensors 55, 57, and 59.

In this case, the same freezing prevention operation can be performed even when the temperature sensors 55, 57, and 59 for detecting the temperature of the return heat medium water are used.

B When Some Hot Water Terminals are Operating When at least one hot water terminal is used, for example, when the hot water terminal 4 is operating, the temperature sensor 53 adjusts the temperature of the outgoing heat carrier water. Therefore, it cannot be determined whether or not the hot water terminal 2 that is not used is likely to freeze. Then, after a predetermined time has elapsed by the timer 64 or the timer 70, the valve 48 is opened by an output signal of the control unit 62 of the heat source device 8, and the heating medium water 6 is discharged for a predetermined amount or for a predetermined time.
And circulation to the circulation path 24 side.

In this case, when the temperature sensors 55, 57, 59 for detecting the temperature of the return heat medium water are used, the timer 6
4 or a predetermined time set in the timer 70, the valves 48 and 50 are selectively opened by the output signal of the control unit 62 of the heat source device 8 to circulate the heat medium water 6 one system at a time. When the water temperature reaches a predetermined temperature, for example, 40 ° C., which is a condition for stopping the antifreeze operation, the operation shifts to the hot water terminal. After all unused hot water terminals are supported, timer 6
4. Reset 70.

C When all the hot water terminals are operating When the heating operation is being performed in all the systems such as the hot water terminals 2 and 4, there is no possibility of freezing, so the start of the heat medium water temperature detection is started. To stop the timer operation. In this case, if even one of the hot water terminals 2, 4 etc. stops operating, the timer 6
4 is reset and restarted.

In this case, the same operation can be performed when the temperature sensors 55, 57, and 59 for detecting the temperature of the return heat medium are used.

In the heating apparatus of this embodiment, a switch 66 or switch 72 for performing a calendar function for time control or an anti-freezing operation, and temperature sensors 55 to 59 as heat medium temperature detecting means are provided in parallel. By executing the anti-freezing operation based on the detection of the temperature of the heat medium water only in the cold season, and executing the anti-freeze operation only when the temperature of the heat medium water is low, the energy saving can be improved.

The heat source device 8 of the embodiment is
Although it is not shown that is used for reheating a bath through another heat exchanger, the present invention can also be applied to a case where a heat source device that enables reheating of a bath is used. In that case, the reheating operation can be performed as an antifreeze operation assuming that the terminal is a hot water terminal.

[0048]

As described above, according to the present invention,
The following effects can be obtained. a In a heating device having a hot water terminal composed of a plurality of systems, together with time management of the antifreeze operation, it is determined whether or not there is a system in which the heating operation is being performed, and then a system that requires antifreeze is selected and predetermined. Since the anti-freezing operation of circulating the heat medium water at a predetermined temperature for a predetermined time is performed, the heat energy required for the anti-freezing can be reduced, and the energy saving can be improved. b When the heating operation is performed in any system,
The heating medium used for the heating operation is selected for a system that requires the anti-freezing operation and is allowed to flow for a predetermined time, so that the heat energy required for the anti-freezing can be reduced and the energy saving can be improved. c When the heating operation is performed in any system,
The heating medium used for the heating operation is selected and passed back until the temperature of the heating medium reaches the predetermined temperature by selecting a system that requires antifreeze operation. Energy can be achieved, and the reliability of freezing prevention can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a method for preventing freezing of a heating device according to the present invention.

FIG. 2 is a flowchart illustrating freeze prevention control.

FIG. 3 is a flowchart showing the freeze prevention control continued from FIG. 2;

FIG. 4 is a flowchart showing another freeze prevention control.

FIG. 5 is a flowchart showing another freeze prevention control following FIG. 4;

FIG. 6 is a diagram showing a conventional heating device.

FIG. 7 is a flowchart showing conventional freeze prevention control.

[Explanation of symbols]

 2, 4 Hot water terminal 6 Heat medium water 8 Heat source unit 24 Circulation path 26 Circulation pump 62 Control unit (control means) 64, 70 Timer

 ──────────────────────────────────────────────────続 き The continuation of the front page F term (reference) 3L070 BB01 DE07 DF07 DG01 DG05

Claims (3)

[Claims] 1. A method for preventing freezing of a heating device for heating by circulating heat transfer water to a hot water terminal comprising a plurality of systems, comprising: a process of determining a time for performing an antifreeze operation; When doing, processing to determine whether the hot water terminal is performing heating operation, If none of the hot water terminal is performing heating operation, while circulating the heat transfer water for each system, A process of measuring the temperature of the return heat medium water and determining a system requiring the antifreeze operation; and passing the heat medium water at a predetermined temperature for a predetermined time for each system selected from the systems requiring the antifreeze operation. A method for preventing freezing of a heating device, comprising: 2. A method for preventing freezing of a heating device for heating by circulating heat medium water to a hot water terminal comprising a plurality of systems, wherein when the time comes, the heat medium water is supplied from a heat source unit. By the determination whether or not the hot water terminal consisting of a plurality of systems is operated, when performing heating operation in any of the hot water terminals, for each system selected from each system in which the hot water terminal is not operating The method for preventing freezing of a heating device according to claim 1, further comprising a process of circulating the heating medium water for a predetermined time. 3. A method for preventing freezing of a heating device for heating by circulating heating medium water to a plurality of hot water terminals, wherein the heating medium is supplied from a heat source unit when the time comes. By the determination whether or not the hot water terminal consisting of a plurality of systems is operated, when performing heating operation in any of the hot water terminals, for each system selected from each system in which the hot water terminal is not operating Circulating the heating medium water,
The method for preventing freezing of a heating device according to claim 1 or 2, further comprising a process of causing a temperature of the return heat medium to reach a predetermined temperature.