COMBUSTION HEAT SOURCE DEVICE

Abstract

A combustion heat source device may include: a housing; a burner housed within the housing; a combustion fan configured to supply air for combustion to the burner; a heat exchanger configured to be heated by combustion of the burner; a temperature sensor configured to detect a temperature of fluid flowing into or out of the heat exchanger; and a controller configured to operate the fan when the burner is operating. A rotation speed of the fan when the burner is operating may correspond to a heating amount by the burner. The controller may be configured to increase the heating amount by the burner when the heating amount is within a first heating amount range and the temperature detected by the temperature sensor exceeds a first reference temperature corresponding to the first range, so that the heating amount enters a second heating amount range that is higher than the first range.

Claims

1. A combustion heat source device comprising: a housing; a burner housed within the housing; a combustion fan configured to supply air for combustion to the burner; a heat exchanger configured to be heated by combustion of the burner; a temperature sensor configured to detect a temperature of fluid flowing into or out of the heat exchanger; and a controller, wherein the controller is configured to operate the combustion fan when the burner is operating, a rotation speed of the combustion fan when the burner is operating corresponds to a heating amount by the burner, and the controller is configured to increase the heating amount by the burner when the heating amount by the burner is within a first heating amount range and the temperature detected by the temperature sensor exceeds a first reference temperature corresponding to the first heating amount range, so that the heating amount by the burner enters a second heating amount range that is higher than the first heating amount range.

2. The combustion heat source device according to claim 1, wherein the controller is configured to extinguish the burner when an extinguishing condition that the temperature detected by the temperature sensor exceeds an upper limit temperature higher than the first reference temperature is satisfied, and to continue operating the combustion fan even after the extinguishing condition is satisfied and the burner is extinguished.

3. The combustion heat source device according to claim 2, wherein the controller is configured to re-ignite the burner when a predetermined time elapses after the extinguishing condition is satisfied and the burner is extinguished.

4. The combustion heat source device according to claim 3, wherein the controller is configured not to re-ignite the burner even if the predetermined time elapses after the extinguishing condition is satisfied and the burner is extinguished, unless a re-ignition condition that the temperature detected by the temperature sensor falls below a lower limit temperature lower than the first reference temperature is satisfied.

5. The combustion heat source device according to claim 2, further comprising a circulation pump configured to deliver the fluid to the heat exchanger, wherein the controller is configured to operate the circulation pump when the burner is operating, and to continue operating the circulation pump even after the extinguishing condition is satisfied and the burner is extinguished.

6. The combustion heat source device according to claim 1, wherein the controller is configured to increase the heating amount by the burner when the heating amount by the burner is within the second heating amount range and the temperature detected by the temperature sensor exceeds a second reference temperature corresponding to the second heating amount range and being higher than the first reference temperature, so that the heating amount by the burner enters a third heating amount range higher than the second heating amount range.

7. The combustion heat source device according to claim 4, further comprising a circulation pump configured to deliver the fluid to the heat exchanger, wherein the controller is configured to operate the circulation pump when the burner is operating, and to continue operating the circulation pump even after the extinguishing condition is satisfied and the burner is extinguished, and the controller is configured to increase the heating amount by the burner when the heating amount by the burner is within the second heating amount range and the temperature detected by the temperature sensor exceeds a second reference temperature corresponding to the second heating amount range and being higher than the first reference temperature, so that the heating amount by the burner enters a third heating amount range higher than the second heating amount range.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0016] FIG. 1 schematically illustrates how a combustion heat source device 2 performs a space heating operation.

[0017] FIG. 2 schematically illustrates how the combustion heat source device 2 according to the embodiment performs a hot water supply operation.

[0018] FIG. 3 illustrates a part of a flow chart of a burner heating amount increasing process executed by a controller 86 in the combustion heat source device 2 according to the embodiment.

[0019] FIG. 4 illustrates a remaining part of the flow chart of the burner heating amount increasing process executed by the controller 86 in the combustion heat source device 2 according to the embodiment.

[0020] FIG. 5 illustrates a graph for describing a situation in which a burner heating amount is increased in the combustion heat source device 2 according to the embodiment.

DESCRIPTION

[0021] Representative, non-limiting examples of the present disclosure will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the disclosure. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved combustion heat source devices.

[0022] Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the disclosure in the broadest sense, and are instead taught merely to particularly describe representative examples of the disclosure. Furthermore, various features of the above-described and below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0023] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

[0024] (EMBODIMENT) A combustion heat source device 2 illustrated in FIG. 1 comprises a housing 4, a combustion chamber 6, a burner 8, an exhaust duct 10, a primary heat exchanger 12, a secondary heat exchanger 14, a burner onward path 16, a burner return path 18, and a circulation pump 20. An air supply pipe 22 into which air enters from outside the housing 4 and an air exhaust pipe 24 out of which exhaust gas flows to the outside of the housing 4 are arranged at a top of the housing 4. The combustion chamber 6 is arranged inside the housing 4. The burner 8 is arranged to generate combustion flame downward at an uppermost part inside the combustion chamber 6. The primary heat exchanger 12 is disposed below the burner 8 inside the combustion chamber 6. The secondary heat exchanger 14 is disposed below the primary heat exchanger 12 inside the combustion chamber 6. The exhaust duct 10 connects a lowermost part of the combustion chamber 6 and the air exhaust pipe 24.

[0025] A space heating onward piping 26 and a space heating return piping 28 through both of which heat medium for space heating (water or antifreeze) flows are coupled to a bottom of the housing 4. The combustion heat source device 2 delivers the heat medium of high temperature through the space heating onward piping 26 to space heating terminal(s) (not illustrated). Also, the combustion heat source device 2 receives the heat medium having its temperature lowered due to heat dissipation at the space heating terminal(s) through the space heating return piping 28 from the space heating terminal(s). An upstream end of the burner onward path 16 is coupled to the space heating return piping 28. A downstream end of the burner onward path 16 is coupled to an upstream end of the secondary heat exchanger 14. A downstream end of the secondary heat exchanger 14 is coupled to an upstream end of the primary heat exchanger 12. A downstream end of the primary heat exchanger 12 is coupled to an upstream end of the burner return path 18. A downstream end of the burner return path 18 is coupled to the space heating onward piping 26. The circulation pump 20 is disposed on the burner onward path 16. The circulation pump 20 causes the heat medium in the burner onward path 16 to flow toward the secondary heat exchanger 14. A space heating return thermistor 30 configured to detect the temperature of the heat medium flowing into the secondary heat exchanger 14 is disposed near the downstream end of the burner onward path 16. A space heating onward thermistor 32 configured to detect the temperature of the heat medium flowing out of the primary heat exchanger 12 is disposed near the upstream end of the burner return path 18.

[0026] The combustion heat source device 2 further comprises a fuel gas flow path 34, a zero governor 36, a flow rate adjusting valve 38, a mixer 40, and a combustion fan 42. A fuel gas supply pipe 44 is coupled to the bottom of the housing 4. The combustion heat source device 2 is supplied with fuel gas such as city gas through the fuel gas supply pipe 44. An upstream end of the fuel gas flow path 34 is coupled to the fuel gas supply pipe 44. A downstream end of the fuel gas flow path 34 is coupled to the mixer 40. The zero governor 36 is disposed on the fuel gas flow path 34 and adjusts a pressure of the fuel gas to an atmospheric pressure. The flow rate adjusting valve 38 is arranged on the fuel gas flow path 34 downstream of the zero governor 36. The flow rate adjusting valve 38 adjusts a flow rate of the fuel gas flowing in the fuel gas flow path 34 by adjusting an opening degree of the fuel gas flow path 34. The mixer 40 is coupled to the combustion fan 42. The mixer 40 suctions air inside the housing 4 when the combustion fan 42 operates. Also, the mixer 40 suctions the fuel gas from the fuel gas flow path 34 by utilizing a negative pressure of the air flowing inside the mixer 40 and thus mixes the air and the fuel gas. When the combustion fan 42 operates, mixture gas constituted of the mixed air and fuel gas is supplied from the mixer 40 to the burner 8 through the combustion fan 42. A mixture ratio of the mixture gas between the air and the fuel gas has been adjusted to a suitable mixture ratio that suits a gas type of the fuel gas by the flow rate adjusting valve 38 adjusting the opening degree of the fuel gas flow path 34.

[0027] An ignition plug 46 and a flame rod 48 are disposed near the burner 8 in the combustion chamber 6. The ignition plug 46 is electrically connected to an igniter 50 disposed outside the combustion chamber 6. The burner 8 starts to operate (i.e., starts combustion, generates heat) when the ignition plug 46 discharges electricity due to the igniter 50 with the combustion fan 42 operating and the mixture gas being supplied to the burner 8. The flame rod 48 is configured to detect presence/absence of combustion by the burner 8.

[0028] The combustion heat source device 2 further comprises a liquid-liquid heat exchanger 52, an internal circulation path 54, a three-way valve 56, a heat exchange onward path 58, a heat exchange return path 60, a heat exchange bypass path 62, a water amount servo valve 64, and a bypass servo valve 66. The liquid-liquid heat exchanger 52 comprises a heat medium flow path 52a and a water flow path 52b, and exchanges heat between the heat medium flowing in the heat medium flow path 52a and water flowing in the water flow path 52b. The heat medium flow path 52a is disposed on the internal circulation path 54. An upstream end of the internal circulation path 54 is coupled to the burner return path 18. A downstream end of the internal circulation path 54 is coupled to the burner onward path 16 upstream of the circulation pump 20. The three-way valve 56 is disposed at a connection between the internal circulation path 54 and the burner onward path 16. The three-way valve 56 is configured to switch between a state under which a side thereof on the space heating return piping 28 is fully open and a side thereof on the internal circulation path 54 is fully closed (see FIG. 1) and a state under which the internal circulation path 54 side is fully open and the space heating return piping 28 side is fully closed (see FIG. 2). Here, the three-way valve 56 is also configured to be in a state under which both the space heating return piping 28 side and the internal circulation path 54 side are half open.

[0029] A water supply pipe 68 and a hot water supply pipe 70 in which water for supplying hot water flows are coupled to the bottom part of the housing 4. The combustion heat source device 2 is configured to heat the water flowing in from the water supply pipe 68 and delivers the high-temperature water to the hot water supply pipe 70. An upstream end of the heat exchange onward path 58 is coupled to the water supply pipe 68. A downstream end of the heat exchange onward path 58 is coupled to an inlet of the water flow path 52b. An upstream end of the heat exchange return path 60 is coupled to an outlet of the water flow path 52b. A downstream end of the heat exchange return path 60 is coupled to the hot water supply pipe 70. An upstream end of the heat exchange bypass path 62 is coupled to the heat exchange onward path 58. A downstream end of the heat exchange bypass path 62 is coupled to the heat exchange return path 60. The water amount servo valve 64 is disposed on the heat exchange onward path 58 upstream of a connection to the heat exchange bypass path 62. The water amount servo valve 64 adjusts a flow rate of the water flowing in the heat exchange onward path 58 by adjusting the opening degree of the heat exchange onward path 58. A water supply flow rate sensor 72 and a water supply thermistor 74 are disposed on the heat exchange onward path 58. The water supply flow rate sensor 72 detects the flow rate of the water flowing inward from the water supply pipe 68. The water supply thermistor 74 detects the temperature of the water flowing inward from the water supply pipe 68. The bypass servo valve 66 is disposed at a connection between the heat exchange bypass path 62 and the heat exchange return path 60. The bypass servo valve 66 is configured to adjust a ratio between the flow rate of the water flowing from the water flow path 52b of the liquid-liquid heat exchanger 52 into the heat exchange return path 60 and the flow rate of the water flowing from the heat exchange bypass path 62 into the heat exchange return path 60. A heat exchanger outlet thermistor 76 which detects the temperature of the water flowing out of the water flow path 52b of the liquid-liquid heat exchanger 52 is disposed on the heat exchange return path 60 upstream of the bypass servo valve 66. A hot water supply thermistor 78 which detects the temperature of the water flowing outward to the hot water supply pipe 70 is disposed on the heat exchange return path 60 downstream of the bypass servo valve 66.

[0030] The combustion heat source device 2 further comprises a drain pan 80 and a drain flow path 82. A drain piping 84 is coupled to the bottom part of the housing 4. Condensation formed on an outer surface of the secondary heat exchanger 14 drips to the drain pan 80. An upstream end of the drain flow path 82 is coupled to the drain pan 80. A downstream end of the drain flow path 82 is coupled to the drain piping 84. The condensation which dripped on the drain pan 80 is drained through the drain flow path 82 to the drain piping 84.

[0031] The combustion heat source device 2 further comprises a controller 86. The controller 86 comprises a CPU, ROM, RAM, etc. The ROM stores various operation programs therein. The RAM temporarily stores various signals inputted to the controller 86 and/or various types of data generated while the CPU executes processes. The controller 86 controls operations of respective components of the combustion heat source device 2 by the CPU executing processes based on the information stored in the ROM and/or RAM.

[0032] As illustrated in FIG. 1, when the controller 86 executes a space heating operation, the controller 86 switches the three-way valve 56 to the state under which the space heating return piping 28 side is fully open and the internal circulation path 54 side is fully closed and also operates the circulation pump 20. Also, the controller 86 operates the combustion fan 42 to supply the mixture gas of the fuel gas and the air to the burner 8, and operates the igniter 50 to cause the burner 8 to operate. Due to this, the heat medium flowing from the space heating return piping 28 into the burner onward path 16 sequentially passes through the secondary heat exchanger 14 and the primary heat exchanger 12, and then the heat medium flows out from the burner return path 18 to the space heating onward piping 26.

[0033] As illustrated in FIG. 2, when the controller 86 executes a hot water supply operation, the controller 86 switches the three-way valve 56 to the state under which the space heating return piping 28 side is fully closed and the internal circulation path 54 side is fully open and also operates the circulation pump 20. Also, the controller 86 operates the combustion fan 42 to supply the mixture gas of the fuel gas and air to the burner 8, and operates the igniter 50 to cause the burner 8 to start the combustion. Due to this, the heat medium in the burner onward path 16 is heated by passing sequentially through the secondary heat exchanger 14 and the primary heat exchanger 12, and then the heat medium dissipates its heat by flowing from the burner return path 18 to pass through the heat medium flow path 52a of the liquid-liquid heat exchanger 52, and returns to the burner onward path 16. Also, the water flowing from the water supply pipe 68 into the heat exchange onward path 58 branches into the water flow path 52b of the liquid-liquid heat exchanger 52 and the heat exchange bypass path 62, and after the water that has passed through the water flow path 52b and thereby been heated merge with the water that has passed through the heat exchange bypass path 62, the merged water then flows from the heat exchange return path 60 out to the hot water supply pipe 70.

[0034] Here, the combustion heat source device 2 is also configured to perform the space heating operation and the hot water supply operation at the same time. In this case, the controller 86 switches the three-way valve 56 to the state under which both of the space heating return piping 28 side and the internal circulation path 54 side are half open, and operates the circulation pump 20. Further, the controller 86 operates the combustion fan 42 to supply the mixture gas of the fuel gas and air to the burner 8, and operates the igniter 50 to cause the burner 8 to start the combustion.

[0035] (Burner Heating Amount Increasing Process) In the space heating operation, the temperature of the heat medium to be delivered to the space heating onward piping 26 is preset based on a space heating set temperature. On the other hand, in the space heating operation, if heat dissipation is not performed at a high level in the space heating terminal(s), such as when the outside air temperature is high, the heat medium of a relatively high temperature may return to the space heating return piping 28. In this case, because a temperature increasing degree of the heat medium passing through the secondary heat exchanger 14 and the primary heat exchanger 12 needs to be made small in the combustion heat source device 2, a process of decreasing the flow rate of the fuel gas supplied to the burner 8 and decreasing the heating amount by the burner 8 is executed.

[0036] In the combustion heat source device 2 according to the present embodiment, when the flow rate of the fuel gas supplied to the burner 8 is to be decreased, a rotation speed of the combustion fan 42 is also to be decreased correspondingly. The respective components inside the housing 4 are cooled by the airflow generated by the operation of the combustion fan 42 even when the temperature of the combustion chamber 6 becomes high due to the combustion of the burner 8. Due to this, when the heating amount by the burner 8 is great, since the airflow generated by the operation of the combustion fan 42 also becomes strong, the respective components inside the housing 4 are sufficiently cooled. However, when the heating amount by the burner 8 is small, since the airflow generated by the operation of the combustion fan 42 becomes weak, the respective components inside the housing 4 may not be sufficiently cooled. To address this, in the present embodiment, the controller 86 executes a burner heating amount increasing process illustrated in FIGS. 3 and 4 to perform a process of increasing the heating amount by the burner 8 (accordingly increasing the rotational speed of the combustion fan 42) when the temperature of the heat medium returning to the space heating return piping 28 is high and also the heating amount by the burner 8 is small (accordingly the rotational speed of the combustion fan 42 is small).

[0037] Here, when the controller 86 is to start the burner heating amount increasing process of FIGS. 3 and 4, a timer count value (see S16, S18, S22, S28 for example) is reset, and a heating amount increasing flag (see S20, S24, S42 for example) is off.

[0038] As illustrated in FIG. 3, in S2, the controller 86 determines whether the temperature detected at the space heating return thermistor 30 (hereafter, also called a space heating return temperature) is equal to or higher than an upper limit temperature Tmax or not. When the space heating return temperature falls below the upper limit temperature Tmax (in case of NO), the process proceeds to S4.

[0039] In S4, the controller 86 determines whether the heating amount by the burner 8 enters a first heating amount range or not. The first heating amount range is a range of the heating amount falling below a first threshold heating amount Q1 (see FIG. 5). When the heating amount by the burner 8 enters the first heating amount range (in case of YES), the process proceeds to S6.

[0040] In S6, the controller 86 determines whether the space heating return temperature is equal to or higher than a first reference temperature T1 or not. The first reference temperature T1 is lower than the upper limit temperature Tmax, and is preset in accordance with the first heating amount range (see FIG. 5). When the space heating return temperature is equal to or higher than the first reference temperature T1 (in case of YES), the process proceeds to S16. When the space heating return temperature falls below the first reference temperature T1 (in case of NO), the process proceeds to S18.

[0041] When the heating amount by the burner 8 does not enter the first heating amount range (in case of NO) in S4, the process proceeds to S8. In S8, the controller 86 determines whether the heating amount by the burner 8 enters a second heating amount range or not. The second heating amount range is a range of the heating amount being equal to or more than the first threshold heating amount Q1 and also falling below the second threshold heating amount Q2, and the second threshold heating amount Q2 is greater than the first threshold heating amount Q1 (see FIG. 5). When the heating amount by the burner 8 enters the second heating amount range (in case of YES), the process proceeds to S10.

[0042] In S10, the controller 86 determines whether the space heating return temperature is equal to or higher than a second reference temperature T2. The second reference temperature T2 is present in accordance with the second heating amount range, and the second reference temperature T2 is higher than the first reference temperature T1 (see FIG. 5). When the space heating return temperature is equal to or higher than the second reference temperature T2 (in case of YES), the process proceeds to S16. When the space heating return temperature falls below the second reference temperature T2 (in case of NO), the process proceeds to S18.

[0043] When the heating amount by the burner 8 does not enter the second heating amount range (in case of NO) in S8, the process proceeds to S12. In S12, the controller 86 determines whether the heating amount by the burner 8 enters a third heating amount range or not. The third heating amount range is a range of the heating amount being equal to or higher than the second threshold heating amount Q2 and also falling below a third threshold heating amount Q3, and the third threshold heating amount Q3 is greater than the second threshold heating amount Q2 (see FIG. 5). When the heating amount by the burner 8 does not enter the third heating amount range (in case of NO), the process proceeds to S18. When the heating amount by the burner 8 enters the third heating amount range (in case of YES), the process proceeds to S14.

[0044] In S14, the controller 86 determines whether the space heating return temperature is equal to or higher than a third reference temperature T3 or not. The third reference temperature T3 is preset in accordance with the third heating amount range, and the third reference temperature T3 is higher than the second reference temperature T2 (see FIG. 5). When the space heating return temperature is equal to or higher than the third reference temperature T3 (in case of YES), the process proceeds to S16. When the space heating return temperature falls below the third reference temperature T3 (in case of NO), the process proceeds to S18.

[0045] The process proceeds to S16 as a result of S4 to S14 when, in the graph of FIG. 5, the heating amount by the burner 8 and the space heating return temperature enter a gray area, while the process proceeds to S18 as a result of S4 to 14 when, in the graph of FIG. 5, the heating amount by the burner 8 and the space heating return temperature enter a white area.

[0046] As illustrated in FIG. 3, in S16, the controller 86 starts timer counting if the timer counting is not being performed. Due to this, the timer count value increases hereon. After S16, the process proceeds to S20.

[0047] In S18, the controller 86 stops the timer counting if the timer counting is ongoing. Due to this, the timer count value does not increase thereafter, but is maintained as-is. After S18, the process returns to S2.

[0048] In S20, the controller 86 determines whether the heating amount increasing flag is ON or not. When the heating amount increasing flag is OFF (in case of NO), the process proceeds to S22.

[0049] In S22, the controller 86 determines whether the timer count value has reached a first predetermined value (e.g., 10 minutes) or not. When the timer count value has not reached the first predetermined value (in case of NO), the process returns to S2. When the timer count value has reached the first predetermined value (in case of YES), the process proceeds to S24.

[0050] In S24, the controller 86 switches the heating amount increasing flag from OFF to ON.

[0051] In S26, the controller 86 resets the timer count value. After S26, the process returns to S2.

[0052] When the heating amount increasing flag is ON (in case of YES) in S20, the process proceeds to S28. In S28, the controller 86 determines whether the timer count value has reached a second predetermined value (e.g., 30 seconds) or not. When the timer count value has not reached the second predetermined value (e.g., 30 seconds) (in case of NO), the process returns to S2. When the timer count value has reached the second predetermined value (e.g., 30 seconds) (in case of YES), the process proceeds to S30.

[0053] In S30, the controller 86 increases the heating amount by the burner 8 by a predetermined heating amount degree.

[0054] In S32, the controller 86 resets the timer count value. After S32, the process returns to S2.

[0055] When the space heating return temperature is equal to or higher than the upper limit temperature Tmax in S2 (in case of YES), the controller 86 determines that an extinguishing condition has been satisfied, and the process proceeds to S34 illustrated in FIG. 4. Here, if the timer counting has been ongoing at this time, the controller 86 stops the timer counting.

[0056] In S34, the controller 86 extinguishes the burner 8 by closing the flow rate adjusting valve 38 and shutting down the supply of the fuel gas to the burner 8. Here, in S34, although the controller 86 extinguishes the burner 8, the controller 86 continues to rotate the combustion fan 42, by which the controller 86 cools the respective components inside the housing 4 by so-called post purge.

[0057] In S36, the controller 86 stands by until a predetermined time (e.g., 3 minutes) elapses after the burner 8 has been extinguished in S34. When the predetermined time (e.g., 3 minutes) elapses after the burner 8 has been extinguished (when it becomes YES), the process proceeds to S38.

[0058] In S38, the controller 86 stands by until the space heating return temperature falls below a lower limit temperature Tmin. The lower limit temperature Tmin is lower than the first reference temperature T1. When the space heating return temperature has fallen below the lower limit temperature Tmin in S38 (when it becomes YES), the controller 86 determines that a re-ignition condition has been satisfied, the process proceeds to S40.

[0059] In S40, the controller 86 opens the flow rate adjusting valve 38 to re-start supplying the fuel gas to the burner 8 and operates the igniter 50 to re-ignite the burner 8.

[0060] In S42, the controller 86 switches the heat amount increasing flag to OFF if the flag is ON.

[0061] In S44, the controller 86 resets the timer count value. After S44, the process returns to S2 shown in FIG. 3.

[0062] In the combustion heat source device 2, once the burner heating amount increasing process has been started, when the heating amount by the burner 8 enters the first heating amount range and also the space heating return temperature is equal to or higher than the first reference temperature T1, timekeeping using the timer count value is performed (see S4, S6, S16). Then, when the timer count value has reached the first predetermined value (e.g., 10 minutes), the heating amount increasing flag is switched from OFF to ON (see S20, S22, S24, S26). After that also, when the heating amount by the burner 8 further remains within the first heating amount range and the space heating return temperature remains equal to or higher than the first reference temperature T1, the timekeeping using the timer count value is performed (S4, S6, S16), and each time the timer count value reaches the second predetermined value (e.g., 30 seconds), the heating amount by the burner 8 is increased (see S20, S28, S30, S32). When the heating amount by the burner 8 enters the second heating amount range as a result of the increase of the heating amount by the burner 8, if the space heating return temperature falls below the second reference temperature T2, the timekeeping using the timer count value is stopped (see S4, S8, S10, S18). When the heating amount by the burner 8 enters the second heating amount range and also the space heating return temperature is equal to or higher than the second reference temperature T2, the timekeeping using the timer count value is restarted (see S4, S8, S10, S16). Then, each time the timer count value reaches the second predetermined value (e.g., 30 seconds), the heating amount by the burner 8 is further increased (see S20, S28, S30, S32). When the heating amount by the burner 8 enters the third heating amount range as a result of further increasing the heating amount by the burner 8, if the space heating return temperature falls below the third reference temperature T3, the timekeeping using the timer count value is stopped (see S4, S8, S12, S14, S18). When the heating amount by the burner 8 enters the third heating amount range and also the space heating return temperature is equal to or higher than the third reference temperature T3, the timekeeping using the timer count value is restarted (see S4, S8, S12, S14, S16). Then, each time the timer count value reaches the second predetermined value (e.g., 30 seconds), the heating amount by the burner 8 is further increased (see S20, S28, S30, S32). When the heating amount by the burner 8 enters a fourth heating amount range as a result of further increasing the heating amount by the burner 8, the timekeeping using the timer count value is stopped (see S4, S8, S12, S18). The fourth heating amount range is a range of the heating amount being equal to or higher than the third threshold heating amount Q3 (see FIG. 5).

[0063] As described above, while the heating amount by the burner 8 is being increased, when the space heating return temperature becomes equal to or higher than the upper limit temperature Tmax and the extinguishing condition is satisfied, the burner 8 is extinguished, and the cooling by the post purge of the combustion fan 42 is performed (see S2, S34). Due to this, the respective components inside the housing 4 can be sufficiently cooled. After the burner 8 has been extinguished, when the predetermined time elapses and also the space heating return temperature has fallen below the lower limit temperature Tmin such that the re-ignition condition is satisfied, the burner 8 is re-ignited (see S36, S38, S40).

[0064] There may be a case where, even if the heating amount by the burner 8 keeps increased, the heating amount by the burner 8 enters the fourth heating amount range without the space heating return temperature becoming equal to or higher than the upper limit temperature Tmax (i.e., without the burner 8 being extinguished). In this case, since the heating amount by the burner 8 is high and also the airflow generated by the operation of the combustion fan 42 is strong, the respective components inside the housing 4 are sufficiently cooled.

[0065] (Modifications) In the combustion heat source device 2, the fuel gas flow path 34 which supplies the fuel gas to the burner 8 and the combustion fan 42 which supplies the air for combustion to the burner 8 may be arranged independently and separately from each other, and the flow rate of the fuel gas supplied to the burner 8 and the flow rate of the air for combustion supplied to the burner 8 may be adjusted separately from each other. In this case, the controller 86 may be configured to adjust the mixture ratio between the air and the fuel gas in the mixture gas to a suitable mixture ratio that suits a gas type of the fuel gas by specifying the flow rate of the fuel gas supplied through the fuel gas flow path 34 to the burner 8 and also specifying the flow rate of the air for combustion which corresponds to the flow rate of the fuel gas and thus controlling the rotational speed of the combustion fan 42.

[0066] The combustion heat source device 2 may not comprise the liquid-liquid heat exchanger 52, the internal circulation path 54, the three-way valve 56, the heat exchange onward path 58, the heat exchange return path 60, the heat exchange bypass path 62, the water amount servo valve 64, and the bypass servo valve 66. In this case, the combustion heat source device 2 is able to perform the space heating operation but is unable to perform the hot water supply operation.

[0067] The combustion heat source device 2 may comprise another burner configured to heat water for supplying hot water which is separated from the burner 8 for heating the space heating heat medium. In this case, the combustion heat source device 2 may not comprise the liquid-liquid heat exchanger 52, the internal circulation path 54, and the three-way valve 56.

[0068] The combustion heat source device 2 may not comprise the secondary heat exchanger 14. In this case, the downstream end of the burner onward path 16 is coupled to the upstream end of the primary heat exchanger 12. Also, in this case, since condensation is not generated, the drain pan 80, the drain flow path 82, and the drain piping 84 may not be provided.

[0069] In the burner heating amount increasing process shown in FIGS. 3 and 4, the determination in S2, S6, S10, S14, S38 may be performed based on the temperature detected by the space heating onward thermistor 32 (space heating onward temperature), rather than being not based on the temperature detected by the space heating return thermistor 30 (the space heating return temperature). When the control based on the space heating onward temperature is performed, one or more of the upper limit temperature Tmax used in the determination of S2, the first heating amount range used in the determination of S4, the first reference temperature T1 used in the determination of S6, the second heating amount range used in the determination of S8, the second reference temperature T2 used in the determination of S10, the third heating amount range used in the determination of S12, the third reference temperature T3 used in the determination of S14, the predetermined heating amount degree used in the process of S30, and the lower limit temperature Tmin used in the determination of S38 may suitably be set different from the values thereof when the control based on the space heating return temperature is performed.

[0070] (Correspondence Relationships) The primary heat exchanger 12 and/or the secondary heat exchanger 14 are examples of a heat exchanger. The heat medium for space heating is an example for fluid. The space heating return thermistor 30 or the space heating onward thermistor 32 is an example for a temperature sensor.