Heat source machine

Abstract

The present invention provides a heat source unit that can properly perform freeze prevention even when the temperature detected by the outside air temperature sensor is affected by burner combustion. [Solution] The heat source unit 1 includes a burner 3, a fan 4 that supplies combustion air to the burner 3 from outside the housing 2, heat exchangers 5 and 6 that recover the heat from the combustion exhaust gas generated by the burner 3 and heat the hot water, piping through which the hot water flows to the heat exchangers 5 and 6, an anti-freeze heater 50 that heats predetermined points in the hot water flow path, an outside air temperature sensor 70 for measuring the temperature outside the housing 2, and a control unit that performs an anti-freeze operation that operates the anti-freeze heater 50 at a predetermined heating capacity so that the heating capacity of the anti-freeze heater 50 can be changed according to the temperature detected by the outside air temperature sensor 70. The control unit is configured to restrict changes that would reduce the heating capacity of the anti-freeze heater 50 even if the temperature detected by the outside air temperature sensor 70 rises while the burner is burning.

Description

Technical Field

[0001] The present invention relates to a heat source machine having an anti-freezing function.

Background Art

[0002] Conventionally, as a heat source machine having an anti-freezing function, there is one that varies the heating capacity of an anti-freezing heater that heats a hot water flow path according to the detected temperature of an outside air temperature sensor in each of the hot water supply operation, the heating operation, and the operation standby state (Patent Document 1). In this heat source machine, when the detected temperature of the outside air temperature sensor becomes low, the heating capacity of the anti-freezing heater is increased, and when the detected temperature of the outside air temperature sensor becomes high, the heating capacity of the anti-freezing heater is decreased.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional heat source machine, not only when the burner is in a non-combustion state, but also in a combustion state where combustion air is supplied from the outside of the heat source machine and the burner is burning during the hot water supply operation or the heating operation, the heating capacity of the anti-freezing heater is changed according to the detected temperature of the outside air temperature sensor to perform anti-freezing operation. However, when the burner is in a combustion state, the detected temperature of the outside air temperature sensor may rise due to the influence of the heat accompanying burner combustion. In this case, although the temperature of the outside air supplied into the heat source machine from the outside does not change, the heating capacity of the anti-freezing heater is decreased due to the rise in the detected temperature of the outside air temperature sensor, so there is a problem that freezing may occur in a part of the hot water flow path.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a heat source unit that can appropriately exhibit freeze prevention performance even when the temperature detected by the outside air temperature sensor is affected by burner combustion. [Means for solving the problem]

[0006] The heat source according to aspect 1 of the present invention is A heat source unit comprising: a burner; a fan that supplies combustion air to the burner from outside the enclosure; a heat exchanger that recovers heat from the combustion exhaust gas generated by the burner and heats hot water; piping through which hot water flows to the heat exchanger; an anti-freeze heater that heats predetermined points in the hot water flow path; an outside air temperature sensor for measuring the temperature outside the enclosure; and a control unit that performs an anti-freeze operation to change the heating capacity of the anti-freeze heater according to the temperature detected by the outside air temperature sensor, thereby operating the anti-freeze heater at a predetermined heating capacity. The control unit is configured to restrict changes that would reduce the heating capacity of the anti-freeze heater even if the temperature detected by the ambient temperature sensor rises while the burner is burning.

[0007] According to the above configuration, even if the temperature detected by the ambient air temperature sensor rises during burner combustion, the current heating capacity of the antifreeze heater can be maintained without reducing its heating capacity, as changes that would reduce the heating capacity of the antifreeze heater are restricted. In other words, in the burner combustion state, the temperature detected by the ambient air temperature sensor may be higher than the actual temperature of the outside air supplied to the heat source unit, so even if the temperature detected by the ambient air temperature sensor rises, the heating capacity of the antifreeze heater is not reduced. Therefore, even in the burner combustion state, the antifreeze performance can be properly maintained.

[0008] The heat source machine according to aspect 2 of the present invention, in aspect 1, The system has a configuration that allows the fan to continue operating for a certain period of time after the burner has stopped burning. The control unit can be configured to restrict changes that would reduce the heating capacity of the anti-freeze heater, even if the temperature detected by the ambient temperature sensor rises, for a predetermined period of time after the burner has stopped burning.

[0009] With this configuration, even when the burner is stopped, the temperature detected by the ambient temperature sensor may rise above the actual ambient air temperature due to the heat generated during burner combustion caused by the fan's operation until a predetermined time has elapsed after the burner has stopped. Therefore, even if the temperature detected by the ambient temperature sensor rises during this period, the heating capacity of the anti-freeze heater can be prevented from decreasing. Accordingly, the anti-freeze performance can be properly maintained even when the burner is stopped and until a predetermined time has elapsed after the burner has stopped. In addition, since the hot and cold water circulation path may cool down due to the fan's operation for a certain period after the burner has stopped, the anti-freeze heater's heating capacity can be prevented from decreasing, so that the anti-freeze performance can be properly maintained even when the hot and cold water circulation path is cooled by the fan's operation.

[0010] The heat source according to embodiment 3 of the present invention is, in embodiment 1 or 2, The control unit can be configured to control the heating capacity of the anti-freeze heater by changing the ON / OFF time of the anti-freeze heater per predetermined period of time.

[0011] This configuration makes it easy to control the heating capacity of the anti-freeze heater according to the temperature detected by the ambient temperature sensor.

[0012] The heat source according to embodiment 4 of the present invention is, in any one of embodiments 1 to 3 above, The ambient temperature sensor can be housed within the enclosure.

[0013] With this configuration, by housing and installing the ambient temperature sensor inside the enclosure, there is no need to modify the enclosure's structural walls at the sensor mounting area, as would be necessary when the ambient temperature sensor is installed exposed outside the enclosure, making it easy to install the ambient temperature sensor. [Brief explanation of the drawing]

[0014] [Figure 1]This is a schematic diagram showing the configuration of the bath water heating system according to the embodiment. [Figure 2] This is a flowchart explaining the operation of the anti-freezing function. [Figure 3] This table shows an example of how heater heating capacity is set. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the accompanying drawings. The heat source unit shown in Figure 1 is a bath water heater 1 with an antifreeze function as an embodiment. The bath water heater 1 has an outer enclosure made of a rectangular housing 2 and includes a burner 3 that generates combustion exhaust gas, a fan 4 that supplies combustion air to the burner 3, and a hot water heat exchanger 5 and a bath heat exchanger 6 that absorb heat from the combustion exhaust gas to heat the hot water. A gas supply pipe 7 that supplies fuel gas is connected to the burner 3. The gas supply pipe 7 is equipped with a main gas solenoid valve 8, a gas proportional valve 9, and a switching gas solenoid valve 10 in order from the upstream side. The hot water heat exchanger 5 and the bath heat exchanger 6 include a primary heat exchanger 11 that recovers sensible heat from the combustion exhaust gas and a secondary heat exchanger 12 that recovers latent heat from the combustion exhaust gas. The bath water heater 1 also includes a neutralizer 13 for neutralizing the drain generated in the secondary heat exchanger 12, and the neutralizer 13 has a neutralization treatment tank for neutralizing the drain. The neutralizer 13 is connected to a drain inlet pipe 15 that is drawn out from a drain collection pan 14 installed in the secondary heat exchanger 12.

[0016] The hot water heat exchanger 5 is connected to an inlet pipe 16 and an outlet pipe 17. The hot water heat exchanger 5 is provided with a connecting pipe 18 that circulates hot water between the primary heat exchanger 11 and the secondary heat exchanger 12. A bypass pipe 19 that bypasses the hot water heat exchanger 5 is connected between the inlet pipe 16 and the outlet pipe 17. A hot water filling pipe 20 for filling the bathtub 34 is connected downstream of the outlet pipe 17. The inlet pipe 16 is equipped with a water volume sensor 21, a water volume servo 22, and a bypass water volume servo 23 located at the connection point of the bypass pipe 19, in order from the upstream side. The outlet pipe 17 is equipped with a hot water high limit sensor 24 near the outlet of the hot water heat exchanger 5, a heat exchanger temperature sensor 25 upstream of the outlet pipe 17, and a hot water temperature sensor 26 located downstream of the outlet pipe 17 at the connection point of the hot water filling pipe 20. The hot water supply pipe 20 is equipped with a hot water supply solenoid valve 27, check valves 28a and 28b, and a hot water volume sensor 29, in that order from the outlet pipe 17 side.

[0017] The bath heat exchanger 6 is connected to a bath circulation return pipe 31 and a bath circulation supply pipe 32, which constitute the bath circulation circuit 30. The bath heat exchanger 6 is provided with a connecting pipe 33 that connects the primary heat exchanger 11 and the secondary heat exchanger 12 and allows hot water to flow through. The bathtub-side ends of the bath circulation return pipe 31 and the bath circulation supply pipe 32 are connected to a circulation adapter 35 of the bathtub 34. The bath circulation return pipe 31 is connected to a hot water supply pipe 20 drawn from the hot water outlet pipe 17. The bath circulation supply pipe 32 is provided with a bath high limit sensor 36 near the outlet of the bath heat exchanger 6, and a bath supply temperature sensor 37 closer to the bathtub side. The bath circulation return pipe 31 is provided with a bath return temperature sensor 38, a pump P, and a bath water flow switch 39 in order from the bathtub 34 side. The bath return temperature sensor 38 is located at the connection point of the hot water supply pipe 20. Furthermore, a water level sensor for detecting the water level in the bathtub 34 may be provided between the pump P and the bath water flow switch 39 in the bath circulation return pipe 31.

[0018] In this embodiment, a path including a hot water supply heat exchanger 5, a water inlet pipe 16, a hot water outlet pipe 17, a bypass pipe 19, and a connecting pipe 18 is referred to as a hot water supply circuit, and a path including a bath heat exchanger 6 and a bath circulation circuit 30 is referred to as a bath circuit. Also, a path through which hot water and drain flow, including the heat exchangers 5 and 6 and the pipes in the housing 2, is referred to as a hot water and drain flow path.

[0019] A plurality of freeze prevention heaters (hereinafter referred to as "heaters") for performing a freeze prevention operation by heating a predetermined location of the hot water and drain flow path are provided in the hot water and drain flow path. The plurality of heaters are collectively referred to as heater 50. In this embodiment, heater 50 is installed at the following attachment positions, but is not limited to these attachment positions. In the hot water supply circuit, in the water inlet pipe 16, there are provided heater 51 installed upstream of the water volume servo 22, heater 52 installed downstream of the water volume servo 22, and heater 53 installed near the secondary heat exchanger 12 of the hot water supply heat exchanger 5. In the hot water outlet pipe 17, there are provided heater 54 installed downstream of the hot water supply temperature sensor 26, heater 55 installed upstream of the connection portion of the bypass pipe 19, heater 56 installed downstream of the heat exchange temperature sensor 25, and heater 57 installed near the primary heat exchanger 11 of the hot water supply heat exchanger 5. Also, heaters 58 and 59 are provided in the connecting pipe 18 that connects the primary heat exchanger 11 and the secondary heat exchanger 12 of the hot water supply heat exchanger 5. A heater 60 is provided in the primary heat exchanger 11 of the hot water supply heat exchanger 5.

[0020] In the bath circuit, a heater 61 is provided in the pump P connected to the bath circulation return pipe 31. Also, in the water filling pipe 20, a heater 62 is provided near the connection portion with the bath circulation return pipe 31. Also, in the neutralizer 13, a heater 63 is provided in the neutralization treatment tank.

[0021] The bath hot water supply device 1 includes a control unit (not shown) that controls the operations of each part of the bath hot water supply device 1. The control unit executes operations such as hot water supply operation, water filling operation, and reheating operation in the bath hot water supply device 1, and also controls the freeze prevention operation.

[0022] In the hot water supply operation, the burner 3 on the hot water supply circuit side is ignited, and the water supplied to the water inlet pipe 16 is heated in the hot water heat exchanger 5 to produce hot water, which is then supplied to the hot water outlet pipe 17 and to the hot water outlet, such as a faucet. In the bath filling operation, the burner 3 on the hot water supply circuit side is ignited, and the bath filling solenoid valve 27 is opened, supplying the hot water produced in the hot water heat exchanger 5 from the bath outlet pipe 17 through the bath filling pipe 20 to the bath circulation return pipe 31 of the bath circulation circuit 30, and this hot water is supplied to the bathtub 34 from the circulation adapter 35 through the bath circulation circuit 30. In the reheating operation, the burner 3 on the bath circuit side is ignited, and the pump P is driven to draw the bathtub water in the bathtub 34 from the circulation adapter 35, heat it in the bath heat exchanger 6 via the bath circulation return pipe 31 of the bath circulation circuit 30, and return this heated bathtub water to the bathtub 34 from the circulation adapter 35 via the bath circulation supply pipe 32 of the bath circulation circuit 30.

[0023] When starting the hot water supply, bath filling, and reheating operations, the burner 3 is activated by rotating the fan 4 to draw in combustion air from outside the housing 2 through the air intake 80 and supply it to the burner 3. When ending the hot water supply, bath filling, and reheating operations, after stopping the combustion of the burner 3, the fan 4 continues to rotate for a specified time (post-purge time) to discharge the combustion exhaust gas inside the housing 2 to the outside, performing a post-purge.

[0024] The bath water heater 1 is equipped with an outside air temperature sensor 70 inside the housing 2 for measuring the temperature outside the housing 2. The outside air temperature sensor 70 is positioned near an air intake port 80 located at the bottom of the front panel of the housing 2, and detects the temperature of the air taken into the housing 2 from the air intake port 80 as the temperature of the outside air. Based on the temperature detected by this outside air temperature sensor 70, the control unit controls the operation of the freeze prevention operation, which activates the heater 50. In this embodiment, the outside air temperature sensor 70 is installed on the bottom surface inside the housing 2 so that the entire unit, including the temperature sensing part, is housed inside the housing 2. This eliminates the need to process the structural wall of the housing 2 at the sensor mounting portion, as would be necessary if the temperature sensing part of the outside air temperature sensor 70 were exposed outside the housing 2 and the outside air temperature sensor 70 were installed inside the housing 2, making it easy to install the outside air temperature sensor 70. Note that the installation position of the outside air temperature sensor 70 is not limited to the bottom surface of the housing 2, but can be installed at any position inside the housing 2 so as to detect the temperature of the outside air.

[0025] Incidentally, while the fan 4 is rotating during or after the burner 3 has stopped burning, the actual temperature of the outside air does not change, but the combustion exhaust gas inside the housing 2 and the heat from the burner combustion may affect the temperature detected by the outside air temperature sensor 70. On the other hand, after the burner has stopped burning and a predetermined time has elapsed, it is assumed that there is no effect of the burner combustion on the temperature detected by the outside air temperature sensor 70. The predetermined time is, for example, the sum of the specified time for rotating the fan 4 after the burner has stopped burning (post-purge time) and a certain period of time (1 minute).

[0026] Conventionally, in freeze prevention operation, the heating capacity of the heater 50 is increased when the temperature detected by the outside air temperature sensor 70 is low, and decreased when the temperature detected by the outside air temperature sensor 70 is high. However, if the temperature detected by the outside air temperature sensor 70 is high due to the effects of burner combustion, there is a risk that part of the hot water flow path may freeze if the heating capacity of the heater 50 is reduced even though part of the hot water flow path is at a low temperature. For example, even during hot water supply operation, the inlet pipe 16 may be at a low temperature, and if either the burner 3 on the hot water supply circuit side or the burner 3 on the bath circuit side is burning, as in the bath water supply device 1, the hot water flow path on the non-burning burner side will be at a low temperature and may be further cooled by the rotation of the fan 4. In this embodiment, it is possible to appropriately perform freeze prevention performance even when the temperature detected by the outside air temperature sensor 70 is affected by burner combustion during freeze prevention operation.

[0027] The operation of the anti-freezing function is described below. The anti-freeze operation is performed by the control unit according to the flowchart shown in Figure 2. Referring to Figure 2, in step S1, when the temperature detected by the ambient temperature sensor 70 falls below 3°C, the anti-freeze operation is started. Once the anti-freeze operation is started, in steps S2, S3, and S4, the heater 50 is operated to repeat a heater cycle (control period) in which the ON time and OFF time of the heater 50 per predetermined time (for example, 30 minutes) are set. The heating capacity of the heater 50 is determined by the length of the ON time and OFF time of the heater 50 in the heater cycle. In other words, the heating capacity of the heater 50 is controlled by changing the ratio of the ON time and OFF time of the heater 50 in the heater cycle. This makes it easy to control the heating capacity of the heater 50 according to the temperature detected by the ambient temperature sensor 70.

[0028] In step S4, once the heater OFF time of the heater cycle has elapsed, the process proceeds to step S5. In step S5, it is determined whether the temperature detected by the ambient temperature sensor 70 has risen and reached a temperature range that reduces the heating capacity of the heater 50. In step S5, if the temperature detected by the ambient temperature sensor 70 has risen and reached a temperature range that reduces the heating capacity of the heater 50 (No in step S5), the process proceeds to step S8. If the temperature detected by the ambient temperature sensor 70 has risen and reached a temperature range that reduces the heating capacity of the heater 50 (Yes in step S5), the process proceeds to step S6.

[0029] In step S6, it is determined whether burner 3 is burning or not. If burner 3 is burning in step S6 (Yes in step S6), the process proceeds to step S10; if burner 3 is not burning (No in step S6), the process proceeds to step S7.

[0030] In step S7, it is determined whether a predetermined time has elapsed since the burner 3 stopped burning. Here, the predetermined time is, for example, the sum of the post-purge time of the fan 4 and a fixed period of time (for example, 1 minute). In step S7, if the predetermined time has elapsed since the burner 3 stopped burning (Yes in step S7), the process proceeds to step S8. If the predetermined time has not elapsed since the burner 3 stopped burning (No in step S7), the process proceeds to step S10.

[0031] In step S10, a control process is performed that does not change the heating capacity of the heater 50, and the process is returned to step S2. In other words, the control process in step S10 maintains the current heater heating capacity without reducing the heating capacity of the heater 50.

[0032] In step S8, it is determined whether the temperature detected by the outside air temperature sensor 70 is 7°C or higher. If it is not 7°C or higher (No in step S8), the process returns to step S2. If it is 7°C or higher (Yes in step S8), the anti-freeze operation is terminated in step S9.

[0033] As described above, the anti-freeze operation starts when the ambient temperature sensor 70 detects a temperature of 3°C or lower (step S1), and continues until the ambient temperature sensor 70 detects a temperature of 7°C or higher (step S8 "Yes" → step S9) when the burner 3 is in a non-combustion state (step S7 "Yes") and the burner 3's combustion no longer affects the ambient temperature sensor 70's detection temperature. In other words, the anti-freeze operation is not terminated while the burner 3 is burning. This ensures that the anti-freeze function can be properly performed without terminating the anti-freeze operation, even if the ambient temperature sensor 70 detects a temperature rise due to the combustion of the burner 3.

[0034] In the operation of the freeze prevention operation in this embodiment, the ON time and OFF time of the heater 50 in the heater cycle (for example, a 30-minute control cycle) in steps S2 to S4 are set using a table. As shown in Figure 3, the table has the following items: a status No. indicating the state of the appliance, the temperature detected by the ambient temperature sensor 70 (Th temperature), and the ON time and OFF time of the heater 50 in the heater cycle (min). That is, the table sets multiple temperature ranges in stages for the temperature detected by the ambient temperature sensor 70, with a status No., and the ON time and OFF time of the heater 50 in the heater cycle are set corresponding to each temperature range. The ON time and OFF time of the heater 50 in the heater cycle are set separately for when the burner 3 is not burning and when it is burning. Note that in the temperature range of the temperature detected by the ambient temperature sensor 70 (Th temperature) shown in the table, the upper limit of "~" is "less than", and the lower limit is "greater than or equal to".

[0035] In this table, the setting is such that as the value of the state number increases, the temperature detected by the ambient temperature sensor 70 decreases, and a heater cycle with a longer ON time for the heater 50 is set. In other words, the heating capacity of the heater 50 increases as the temperature detected by the ambient temperature sensor 70 decreases, and decreases as the temperature detected by the ambient temperature sensor 70 increases.

[0036] For example, if the ambient temperature sensor 70 detects a temperature of 0°C at the start of the anti-freeze operation, the state No. becomes "2," and the heater 50's heating capacity is set to a heater cycle with an ON time of 15 minutes and an OFF time of 15 minutes, regardless of whether the burner 3 is in a non-combustion or combustion state. Then, if the ambient temperature sensor 70 detects a temperature during the anti-freeze operation that falls within the temperature range that increases the heater 50's heating capacity, the heater 50 switches to a heater cycle that increases its heating capacity, regardless of whether the burner 3 is in a non-combustion or combustion state, as soon as the ambient temperature sensor 70 detects a temperature within the temperature range that increases the heater 50's heating capacity. For example, if the heater 50 was operating at the heater heating capacity for state No. "2," and the ambient temperature sensor 70 detects a temperature that falls within the temperature range corresponding to state No. "3," the heater heating capacity is increased to that of state No. "3" at that point. In other words, the heater heating capacity (state No. "2") changes from a heater 50 ON time of 15 minutes and OFF time of 15 minutes to a heater heating capacity (state No. "3") where the heater 50 ON time is 20 minutes and OFF time is 10 minutes when burner 3 is not burning, and the heater heating capacity (state No. "3") changes to a heater 50 ON time of 25 minutes and OFF time is 5 minutes when burner 3 is burning. In this case, for example, when burner 3 is not burning, if the change (heater cycle transition) occurs when a certain amount of time has elapsed since the heater 50 was turned ON during the 15-minute ON time of heater 50 in state No. "2", the count for the 20-minute ON time of heater 50 in state No. "3" will be extended by the insufficient time so that the ON time from when the heater 50 was turned ON becomes 20 minutes. Note that even if the heater cycle is changed during the OFF time of heater 50, the OFF time count is not reset, but continues to be counted and the heater cycle is transitioned. Thus, when increasing the heating capacity of the heater 50, regardless of whether the burner 3 is in a non-combustion or combustion state, and regardless of the progress of the heater cycle, the heating capacity of the heater 50 is immediately increased in accordance with the temperature detected by the ambient temperature sensor 70. This ensures that the increase in the heating capacity of the heater 50 does not lag behind the decrease in temperature inside the housing 2, and that the antifreeze performance is properly achieved.

[0037] On the other hand, if the temperature detected by the outside air temperature sensor 70 rises during the anti-freeze operation and falls into a temperature range that reduces the heating capacity of the heater 50 (Yes in step S5), if the burner 3 is burning (Yes in step S6), or if the burner 3 is not burning but a predetermined time has not elapsed since combustion stopped (No in step S7), the heating capacity of the heater 50 is not changed (a change that reduces the heating capacity of the heater 50), and the current heater heating capacity is maintained (step S10).

[0038] In other words, when burner 3 is in combustion, the temperature detected by the ambient temperature sensor 70 may be higher than the actual ambient temperature, and the temperature of part of the hot and cold water flow path or the side of the hot and cold water flow path where hot and cold water is not flowing may be lower. Furthermore, even when burner 3 is stopped burning, for a predetermined time after burner combustion stops, the temperature detected by the ambient temperature sensor 70 may be higher than the actual ambient temperature due to the heat generated during burner combustion caused by the rotation of fan 4. In addition, it is possible that the hot and cold water flow path may cool down due to the rotation of fan 4 for a certain period of time after burner combustion stops (post-purge).

[0039] Therefore, even if the temperature detected by the outside air temperature sensor 70 rises during antifreeze operation and falls into a temperature range that reduces the heating capacity of the heater 50, the heating capacity of the heater 50 is not reduced, and the current heater heating capacity is maintained, as long as the burner 3 is burning, or even if the burner 3 is not burning but a predetermined time has not elapsed since combustion stopped. Consequently, the antifreeze performance can be properly maintained even during the combustion state of the burner 3 and until a predetermined time has elapsed after the burner has stopped burning. Furthermore, the antifreeze performance can be properly maintained even when the hot water flow path is cooled by the rotation of the fan 4 after the burner has stopped burning.

[0040] On the other hand, even if the temperature detected by the ambient temperature sensor 70 rises during antifreeze operation and falls into a temperature range that reduces the heating capacity of the heater 50, if the burner is not burning for a predetermined time after the burner has stopped burning (Yes in step S7), the heater heating capacity will be reduced to the state No. corresponding to the temperature detected by the ambient temperature sensor 70 when the OFF time for the heater 50 has elapsed (step S4). Therefore, it is possible to prevent unnecessary power consumption and to properly perform antifreeze performance. In addition, by making a change to reduce the heating capacity of the heater 50 when the OFF time for the heater 50 has elapsed, it is possible to prevent the OFF time for the heater 50 from becoming temporarily longer when changing the heater cycle, and to properly perform antifreeze performance.

[0041] The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. For example, in freeze prevention operation, while the burner is not burning, the control may change the heating capacity of the freeze prevention heater 50 according to the temperature detected by the outside air temperature sensor 70. In other words, the operation process of step S7 in the flowchart of Figure 2 may not be performed. Furthermore, the heat source may be a heating and hot water supply system equipped with a heating circuit, or a hot water supply system that only provides hot water. [Explanation of symbols]

[0042] 1. Bath water heating system 2 cabinets 3 burners 4 Fans 5. Hot water heat exchanger 6. Bath heat exchanger 7. Gas supply pipe 8. Main gas solenoid valve 9. Gas proportional valve 10 Switching gas solenoid valve 11 Primary heat exchanger 12 Secondary heat exchanger 13 Neutralizer 14 Drain collection pan 15 Drain inlet pipe 16 Inlet pipe 17. Hot water outlet pipe 18 Connecting pipe 19 Bypass pipe 20 Hot water supply pipe 21 Water volume sensor 22 Water volume servo 23 Bypass water flow servo 24 Hot water supply high limit sensor 25 Heat exchanger temperature sensor 26 Hot water temperature sensor 27. Solenoid valve for filling hot water 28a, 28b Check valve 29. Water volume sensor 30 Bath circulation circuit 31 Bath circulation return pipe 32 Bath circulation supply pipe 33 Connecting pipes 34 Bathtub 35 Circulation Adapter 36 Bath High Limit Sensor 37 Bath temperature sensor 38 Bath return temperature sensor 39 Bath water flow switch 50, 51~63 Anti-freeze heater 70 Outdoor temperature sensor 80 Air supply port P Pump

Claims

1. A heat source unit comprising: a burner; a fan that supplies combustion air to the burner from outside the enclosure; a heat exchanger that recovers heat from the combustion exhaust gas generated by the burner and heats hot water; piping through which hot water flows to the heat exchanger; an anti-freeze heater that heats predetermined points in the hot water flow path; an outside air temperature sensor for measuring the temperature outside the enclosure; and a control unit that performs an anti-freeze operation to change the heating capacity of the anti-freeze heater according to the temperature detected by the outside air temperature sensor, thereby operating the anti-freeze heater at a predetermined heating capacity. The control unit is configured to restrict changes that would reduce the heating capacity of the anti-freeze heater even if the temperature detected by the outside air temperature sensor rises while the burner is burning, thus providing a heat source unit.

2. In the heat source machine according to claim 1, The system has a configuration that allows the fan to continue operating for a certain period of time after the burner has stopped burning. The control unit is configured to restrict changes that would reduce the heating capacity of the anti-freeze heater, even if the temperature detected by the outside air temperature sensor rises, for a predetermined period of time after the burner combustion stops.

3. In the heat source machine according to claim 1 or 2, The control unit is a heat source unit that controls the heating capacity of the anti-freeze heater by changing the ON / OFF time of the anti-freeze heater per predetermined period of time.

4. In the heat source machine according to claim 1 or 2, The outside air temperature sensor is housed within the heat source unit.

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