JP2017026280A - Water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water heater that measures temperature of a combustion exhaust gas from which sensible heat is recovered to reliably determine if scale is clogged.SOLUTION: The water heater includes: a fin-and-tube-type heat exchanger for heating clean water by a combustion gas; temperature detection means for detecting exhaust gas temperature of which heat has been exchanged by the heat exchanger; and determination means for determining that scale is deposited inside a heat transfer pipe of the heat exchanger when detection temperature detected by the temperature detection means is equal to or higher than preset temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hot water supply apparatus, and more particularly to a hot water supply apparatus having a function of determining scale clogging caused by scale accumulation in a heat transfer tube of a heat exchanger.

  Conventionally, various hot water supply apparatuses according to heat sources such as a gas hot water supply apparatus, an electric hot water supply apparatus, and an oil hot water supply apparatus have been widely used in general households. In particular, a gas hot water supply device exchanges heat between a blower fan that takes in combustion air from the outside, a burner unit that mixes and burns combustion air and fuel gas, and high-temperature combustion gas and water flowing through a heat transfer tube. A heat exchanger for heating the water, an exhaust pipe for discharging the exhaust gas after the heat exchange to the outside.

  As the heat exchanger, a heat exchanger tube and a fin-and-tube heat exchanger composed of a plurality of fins fixed to the heat exchanger tube so as to be able to conduct heat are generally adopted. What consists of is widely used.

  By the way, when tap water with high hardness is used as the tap water supplied to the heat exchanger, calcium and magnesium contained in the tap water are combined with carbonate ions, sulfate ions, etc., so that the scale is deposited. . This scale tends to precipitate when the temperature of hot water rises, and builds up in the heat exchanger tubes of the heat exchanger, causing scale clogging, resulting in poor heat exchange efficiency in the heat exchanger, and the temperature of the heat exchanger tubes and fins. There is a problem of rising.

  If you continue to use the hot water supply device with the above scale clogging, thermal stress will be repeatedly applied to the heat exchanger, causing cracks in the heat transfer tubes and the joints between the heat transfer tubes and the fins, damaging the heat exchanger There is a fear. For this reason, when scale clogging occurs, it is necessary to remove the scale. Conventionally, a hot water supply apparatus has been provided with a function of detecting scale clogging while avoiding damage even if scale clogging occurs.

  For example, Patent Document 1 discloses an apparatus that determines scale clogging based on a rise in temperature of hot water due to post-boiling after combustion stops. Patent Document 2 discloses a hot water heater that determines scale clogging based on a change in heat exchange efficiency in a heat exchanger. In Patent Document 3, the temperature of the flue gas from which sensible heat has been recovered by the flue gas temperature estimating means is estimated, and even if the estimated temperature of the flue gas rises due to clogging of the scale, the estimated temperature of the flue gas has a predetermined temperature. There has been disclosed a hot water supply apparatus that notifies scale clogging while performing combustion control so as not to exceed or stopping combustion to avoid damage to the heat exchanger. Patent Document 4 discloses a hot water supply apparatus that performs combustion control and mixes exhaust gas so that the temperature of hot water in a heat exchanger that absorbs latent heat of combustion exhaust gas does not exceed a set value.

Japanese Patent No. 4854020 JP 2008-215657 A Japanese Patent No. 5370807 Japanese Patent No. 3970332

  However, in the case of determining scale clogging based on the rise in the temperature of hot water due to post-boiling after stopping combustion as in the device of Patent Document 1, it cannot be determined during the combustion operation, and the position to be heated and the attachment of the temperature sensor Depending on the position, it may be difficult to detect a temperature increase due to post-boiling in the case of a combustion pattern with a low combustion amount or a hot water heater with a large capacity. Further, it is necessary to check the relationship between scale clogging and post-boiling for each combustion pattern, and there is a problem that it is not easy to set the criteria for determining scale clogging.

  Moreover, in the apparatus of Patent Document 2, since the scale clogging is determined by changing the combustion amount during the combustion operation, there is a problem that the hot water supply amount and the hot water supply temperature are unintended by the user. In the apparatus of Patent Document 3, the temperature of combustion exhaust gas after heat exchange is estimated by the exhaust gas temperature estimation means from the remaining hot water temperature and the tapping temperature, and therefore there is a risk of erroneous detection. In the apparatus of Patent Document 4, combustion control is performed by measuring the temperature of combustion exhaust gas after heat exchange, but scale clogging cannot be determined.

  An object of the present invention is to provide a hot water supply apparatus capable of accurately determining scale clogging by measuring the temperature of combustion exhaust gas from which sensible heat has been recovered.

  The hot water supply apparatus according to claim 1 includes a fin-and-tube heat exchanger for heating clean water with combustion gas, and temperature detecting means for detecting an exhaust temperature after heat exchange in the heat exchanger. And a judging means for judging that a scale is accumulated in the heat transfer tube of the heat exchanger when the detected temperature detected by the temperature detecting means is equal to or higher than a set temperature. .

  According to a second aspect of the present invention, there is provided a hot water supply apparatus according to the first aspect of the invention, wherein the temperature detecting means is a downstream of the heat transfer tube portion closest to the combustion portion that always burns during the hot water supply operation in the heat transfer tube constituting the heat exchanger. It is characterized in that it is provided in the vicinity of the fin from which the combustion gas passing around the side is exhausted.

  According to a third aspect of the present invention, there is provided the hot water supply apparatus according to the first or second aspect, wherein the heat exchanger is a sensible heat recovery heat exchanger for recovering sensible heat of combustion exhaust, The latent heat recovery type hot water supply apparatus includes a latent heat recovery heat exchanger for recovering latent heat of combustion exhaust gas on the downstream side of the exhaust passage of the exchanger.

  When scale clogging occurs, heat cannot be transferred efficiently from the combustion gas to the water flowing through the heat exchanger tubes, so the temperature of the heat exchanger tubes and fins rises, and the exhaust temperature after heat exchange in the heat exchanger It rises abnormally. Therefore, according to the first aspect of the present invention, the temperature detecting means for detecting the exhaust gas temperature and the scale in the heat transfer tube of the heat exchanger when the detected temperature detected by the temperature detecting means is equal to or higher than the set temperature. It is possible to detect the exhaust temperature directly during combustion operation, and if the exhaust temperature exceeds the set temperature, the heat exchanger will be clogged with scale. Can be accurately determined.

  That is, the exhaust gas temperature of the combustion gas after the heat exchange in the heat exchanger is directly measured by the temperature detecting means during the combustion operation, and the exhaust gas temperature abnormally generated due to the clogging of the scale and the heat transfer of the heat exchanger being obstructed. By detecting the rise, scale clogging can be determined, so scale clogging can be accurately determined during combustion operation. When determining scale clogging, the amount of hot water and the hot water temperature that are not intended by the user Fluctuations can be prevented.

  According to the invention of claim 2, the temperature detecting means is a combustion that passes through the downstream side of the heat transfer tube portion that is closest to the combustion portion that always burns during hot water supply operation in the heat transfer tube constituting the heat exchanger. Because it is provided near the fin where the gas is exhausted, it can detect the exhaust temperature of the combustion gas that has passed near the heat transfer tube part where scale clogging is most likely to occur, regardless of the combustion pattern. It can cope with the combustion operation by the amount of combustion.

According to the invention of claim 3, the heat exchanger is a sensible heat recovery heat exchanger that recovers the sensible heat of the combustion exhaust, and the combustion exhaust is disposed downstream of the exhaust passage of the sensible heat recovery heat exchanger. Since the latent heat recovery heat exchanger for recovering latent heat is provided, most of the heat generated by the combustion can be used for heating clean water, and a highly efficient latent heat recovery type hot water supply apparatus can be configured.
Also, within the allowable temperature range, even if the heat exchange efficiency of the sensible heat recovery heat exchanger decreases due to clogging of the scale and the exhaust temperature rises, heat is exchanged in the latent heat recovery heat exchanger and the entire hot water supply system performs heat exchange. Since the decrease in efficiency is small, a highly efficient hot water supply apparatus can be configured, and the exhaust temperature of the sensible heat recovery heat exchanger is directly detected, so that scale clogging can be accurately determined.

It is a schematic block diagram of the hot water supply apparatus which concerns on the Example of this invention. It is a front view of a hot water supply apparatus. (A) is a longitudinal cross-sectional view of a hot-water supply apparatus, (b) is an enlarged longitudinal cross-sectional view of the part provided with the temperature detection means. (A) is a top view of the principal part of the heat exchanger area | region of the lower stage of a heat exchanger part, (b) is a top view of the principal part of the heat exchanger area | region of the upper stage of a heat exchanger part. It is a flowchart of scale clogging determination operation control.

  Hereinafter, modes for carrying out the present invention will be described based on examples.

Initially, the whole structure of the hot water supply apparatus 1 of this invention is demonstrated.
The hot water supply device 1 is applied as a heat source device such as a hot water supply device or a heating device, and as shown in FIG. 1, the heat generated by burning fuel gas is used to heat water or hot water. It constitutes a gas water heater.

  The hot water supply device 1 includes a blower fan 2 for supplying combustion air, a burner unit 3 for burning fuel gas, a heat exchanger unit 4 for exchanging heat between the combustion gas and water by the burner unit 3, A control unit 7 that receives signals from the exhaust port 5 for discharging the combustion gas after heat exchange by the heat exchanger unit 4, various pipes such as the water inlet pipe 6a and the hot water outlet pipe 6b, various sensors, and drives and controls various devices. Etc.

Next, the burner unit 3 will be described.
The burner unit 3 includes a burner unit 11 that burns by mixing fuel gas supplied from a fuel supply pipe (not shown) and combustion air supplied from the blower fan 2, and a burner can body that accommodates the burner unit 11. 12 and a combustion space 13 above the burner unit 11 in the burner can body 12. The burner can body 12 is formed in a rectangular parallelepiped shape having an upper opening. A blower fan 2 is provided at the lower end of the burner can body 12.

  As shown in FIGS. 1, 2, and 4, the burner unit 11 includes a plurality of combustion pipes 14 arranged in parallel in the left-right direction, and is configured in, for example, a multistage system including three combustion stages 11 a to 11 c. ing. Each of the combustion stages 11a to 11c includes, for example, five, two, and three combustion pipes 14, respectively, and is connected to a corresponding fuel supply pipe. Each of the combustion stages 11a to 11c can be controlled by the control unit 7, and the number of combustion stages 11a to 11c and the output thereof are adjusted according to various operations.

  During the hot water supply operation, for example, a one-stage combustion stage in which only the two combustion pipes 14 in the central combustion stage 11b are operated to burn, and a two-stage in which the five combustion pipes 14 in the center and right combustion stages 11b and 11c are operated to burn. Combustion stage, three-stage combustion stage in which seven combustion pipes 14 in the left and center combustion stages 11a and 11b are operated for combustion, and four-stage combustion stage in which ten combustion pipes 14 in all the combustion stages 11a to 11c are operated in combustion. The combustion operation can be performed by switching the combustion stage to four stages. The central combustion stage 11b corresponds to a combustion section that is always combusted during a hot water supply operation.

  As shown in FIGS. 2 and 3A, an igniter 15 and a frame rod 16 are arranged in the combustion space 13 above the portion corresponding to the combustion stage 11b of the burner unit 11, respectively. The igniter 15 and the frame rod 16 are respectively attached from the front side of the burner can body 12, and the frame rod 16 is provided on the right side of the igniter 15.

  The igniter 15 ignites the fuel-air mixture supplied from the burner unit 11 by generating an ignition spark with an ignition target provided in the burner unit 11 so as to protrude into the combustion space 13. And it is attached so that it may extend toward diagonally downward.

  The flame rod 16 detects a current flowing from the flame rod 16 to the flame by applying a voltage between the flames during the combustion operation of the burner unit 11 and using conductivity and rectification action due to the ionization of the flame. It is for detecting the presence or absence of a flame, and is attached so as to extend substantially horizontally so as to protrude into the combustion space 13.

Next, the heat exchanger unit 4 will be described.
As shown in FIG. 1 to FIG. 3A, the heat exchanger unit 4 mainly includes a sensible heat recovery heat exchanger 17 that recovers sensible heat of combustion gas, and a heat exchanger 17 for sensible heat recovery. The latent heat recovery heat exchanger 19 that mainly recovers latent heat from the exchanged combustion gas (exhaust gas), the lower heat exchanger can 18 that houses the sensible heat recovery heat exchanger 17, and the latent heat recovery heat An upper heat exchanger can body 20 or the like that accommodates the exchanger 19 is provided.

  The lower heat exchanger can body 18 is configured in a rectangular frame shape in plan view, and the lower end portion of the lower heat exchanger can body 18 and the upper end portion of the burner can body 12 are joined by caulking or screw fastening. .

  The upper heat exchanger can body 20 is formed in a rectangular parallelepiped shape, and a tray 6d for collecting drain (condensate) generated by the recovery of latent heat at the lower end, which is the bottom of the upper heat exchanger can body, and an exhaust outlet of the lower heat exchanger can body 18 An exhaust outlet 24 that opens toward the inner side of the upper heat exchanger can body 20, and exhausts the heat-exchanged air to the lower front portion of the upper heat exchanger can body 20 corresponding to the front side of the hot water supply device 1. An exhaust port 5 for discharging the hot water supply apparatus 1 to the outside is provided.

  The lower end portion of the upper heat exchanger can body 20 and the upper end portion of the lower heat exchanger can body 18 are joined by caulking or screw fastening. As shown in FIGS. 2 and 3A, a thermal fuse 23 is provided around the lower heat exchanger can 18 so as to detect an abnormally high temperature.

Next, the sensible heat recovery heat exchanger 17 will be described.
As shown in FIGS. 3A and 4, the sensible heat recovery heat exchanger 17 is a fin-and-tube including a heat transfer tube 25 and a plurality of fins 26 fixed to the heat transfer tube 25 so as to be able to transfer heat. It constitutes a mold heat exchanger. The plurality of fins 26 are brazed to the inner peripheral surface of the lower heat exchanger can 18 respectively. The heat transfer tubes 25 and the fins 26 are made of copper, but are not particularly limited to this material, and may be made of stainless steel.

  As shown in FIG. 1, FIG. 3A, and FIG. 4, the heat exchange region 21 of the sensible heat recovery heat exchanger 17 in the lower heat exchanger can 18 is a lower stage facing the combustion space 13. This is a two-stage structure including a lower heat exchange region 21A on the side and an upper heat exchange region 21B on the upper stage side (downstream side of the combustion gas flow).

  As shown in FIG. 4, the heat transfer tube 25 includes a plurality of straight tube portions 27 arranged substantially in parallel over two stages, and a plurality of connection tubes that connect ends of the plurality of straight tube portions 27 to each other. Part 28. Four straight pipe portions 27 are arranged in the lower heat exchange area 21A shown in FIG. 4A, and four straight pipe portions 27 are arranged in the upper heat exchange area 21B shown in FIG. 4B. In each of the lower heat exchange region 21A and the upper heat exchange region 21B, the heat transfer tubes 25 are each configured in a meandering shape in plan view. The downstream end of the straight pipe portion 27b on the downstream side of the lower heat exchange region 21A is connected to the upstream end of the straight pipe portion 27c on the upstream side of the upper heat exchange region 21B by the connecting pipe portion 28.

  Fuel gas is supplied to the burner unit 11 from the fuel supply pipe and combustion air is supplied from the blower fan 2, and a fuel-air mixture in which fuel gas and air are mixed is burned in the combustion space 13. The combustion gas generated at this time is introduced into the inside of the lower heat exchanger can 18 above the combustion space 13 and heats the water in the sensible heat recovery heat exchanger 17 while lowering the temperature, and the lower heat exchanger can. It is exhausted from the exhaust outlet 24 of the body 18 and introduced into the upper heat exchanger can body 20.

  The clean water that has entered the sensible heat recovery heat exchanger 17 flows through the lower heat exchange region 21A of the heat transfer tube 25, and then flows through the upper heat exchange region 21B. As described above, the sensible heat recovery heat exchanger 17 The hot water is heated by the sensible heat of the combustion gas while passing through the hot water and discharged from the hot water supply pipe 6b to the outside of the hot water supply apparatus 1.

Next, the latent heat recovery heat exchanger 19 will be described.
As shown in FIG. 3A, the latent heat recovery heat exchanger 19 includes a plurality of heat transfer tubes 29 in a spiral shape, a meandering shape, and the like inside an upper heat exchanger can body 20.

  Inside the upper heat exchanger can body 20, there are provided rectifying plates 31 a, 31 b, 31 c that form a flow path for the combustion gas introduced into the upper heat exchanger can body 20 from the exhaust outlet 24 and rectify it. The combustion gas after the heat exchange is discharged to the outside of the hot water supply apparatus 1 from the exhaust port 5 provided on the front side of the upper heat exchanger can body 20. At this time, the combustion gas heats the water supplied from the water source to the inlet pipe 6a in the latent heat recovery heat exchanger 19 and lowers the temperature, and the water vapor contained in the combustion gas is condensed to become drain (condensed water). They are collected in the tray 6d, sent to the neutralizer (not shown) through the drain pipe 6c, neutralized, and discharged to the outside of the hot water supply apparatus 1. The heated clean water enters the straight pipe portion 27a on the upstream side of the lower heat exchange region 21A of the sensible heat recovery heat exchanger 17.

Next, the temperature detection sensor 32 will be described with reference to FIGS.
As shown in FIG. 3 (a), the hot water supply device 1 is a temperature detection sensor that is a temperature detection means for detecting the temperature (exhaust temperature) of the combustion gas after heat exchange in the sensible heat recovery heat exchanger 17. 32. The temperature detection sensor 32 in the heat transfer tube 25 of the sensible heat recovery heat exchanger 17 shown in FIG. 4 is a combustion that passes through the downstream side of the heat transfer tube portion closest to the combustion stage 11b that always burns during hot water supply operation. It is provided in the vicinity of the fin 26 from which gas is exhausted.

  As shown in FIG. 3B, the temperature detection sensor 32 is inserted in the vicinity of the fin 26 fixed to the portion directly above the combustion stage 11b in the straight pipe portion 27b on the most downstream side of the lower heat exchange region 21A. The upper heat exchanger can body 20 is inserted from the rear side and fixed to the upper heat exchanger can body 20 by brazing or the like.

  The temperature detection sensor 32 includes a known temperature detection sensor including a thermocouple 32a and a pair of lead wires 32b extending from the thermocouple 32a. The pair of lead wires 32 b are connected to the control unit 7, and the exhaust gas temperature at which the combustion gas is discharged from the lower heat exchanger can 18 is transmitted to the control unit 7 by the detection signal of the temperature detection sensor 32.

Next, the control unit 7 will be described.
The control unit 7 shown in FIGS. 1 and 2 controls the hot water supply apparatus 1 and is configured such that various sensors are electrically connected to receive detection signals from the various sensors. The control unit 7 controls driving of the blower fan 2, the burner unit 11 and the like based on the hot water temperature set by the operation remote controller, the amount of hot water supplied to the hot water tap, and detection signals received from various sensors, and hot water supply operation Execute.

Next, scale clogging determination operation control will be described.
As shown in FIG. 5, when the exhaust temperature detected by the temperature detection sensor 32 becomes equal to or higher than the set temperature, the control unit 7 corresponding to the determination means is in the heat transfer tube 25 of the sensible heat recovery heat exchanger 17. It is possible to execute scale clogging determination operation control that determines that scale has accumulated on the surface. A control program for the scale clogging determination operation control is stored in the control unit 7 in advance. In the figure, the symbol Si (i = 1, 2,...) Indicates each step.

  First, in S1, the control unit 7 determines whether or not the hot water supply apparatus 1 is in a hot water supply operation. When the hot water supply apparatus 1 is in the hot water supply operation, that is, when the control unit 7 receives a signal based on the hot water supply operation, the determination of S1 is Yes, the process proceeds to S2, and the determination of S1 is No while the determination is S1. repeat.

  Next, in S2, the control unit 7 reads the detection signal of the temperature detection sensor 32 that measures the exhaust temperature, acquires the exhaust temperature, and proceeds to S3.

  Next, in S3, it is determined whether or not the exhaust temperature exceeds a set temperature (for example, about 180 to 200 ° C.). If the exhaust temperature exceeds the set temperature, the determination in S3 is Yes, and the process proceeds to S4. Transition. If the exhaust temperature is equal to or lower than the set temperature, the determination in S3 is No, it is determined that the heat exchanger 21 is normal, and the process returns. The set temperature need not be limited to the above temperature, and can be changed as appropriate.

  Here, at the time of the hot water supply operation, as described above, the burner unit 11 is operated by adjusting the combustion stage in four stages according to the required heat quantity, but the two combustion pipes 14 in the central combustion stage 11b are Combustion operation is possible with the minimum combustion amount, and combustion is always performed during hot water supply operation.

  On the other hand, in the sensible heat recovery heat exchanger 17, the clean water heated by the latent heat recovery heat exchanger 19 and supplied to the heat transfer tubes 25 flows downstream from the straight pipe portion 27 a on the upstream side of the lower heat exchange region 21 </ b> A. Since the water temperature of the straight pipe part 27b is higher than the water temperature of the straight pipe part 27a, the temperature of the heat transfer pipe is lower than the burner unit 11 in the lower heat exchange region 21A. The straight pipe portion 27b is the highest.

  For this reason, the portion of the straight pipe portion 27b immediately above the combustion stage 11b that always burns is more likely to deposit scale than the other portions. When scale clogging occurs in the straight pipe portion 27b, the exhaust temperature discharged from the lower heat exchanger can 18 abnormally rises to about 180 to 200 ° C. due to the heat transfer failure of the sensible heat recovery heat exchanger 17. To do. If the sensible heat recovery heat exchanger 17 is normal, the exhaust temperature is normally maintained at about 120 ° C., so that scale clogging can be accurately determined by utilizing this increase in the exhaust temperature.

  In S4, the control unit 7 determines that scale clogging has occurred in the sensible heat recovery heat exchanger 17, and notifies the user of the scale clogging via the operation remote control display or voice, and then Return. In addition, after notifying scale clogging, the hot water supply operation may be continued, immediately after notifying scale clogging, the hot water supply operation may be stopped, or when the scale clogging is notified and a predetermined time has elapsed, The operation may be stopped.

Next, the operation and effect of the hot water supply apparatus 1 of the present invention will be described.
The hot water supply apparatus 1 of the present invention includes a temperature detection sensor 32 for detecting the exhaust temperature, and a sensible heat recovery heat exchanger 17 when the detected temperature detected by the temperature detection sensor 32 is equal to or higher than a set temperature. Since the control unit 7 that determines that the scale is accumulated in the heat transfer tube 25 is provided, it is possible to detect a rise in the exhaust temperature that is generated when the heat exchange of the heat exchanger 17 for sensible heat recovery is hindered due to clogging of the scale. When the exhaust gas temperature is equal to or higher than the set temperature, it can be accurately determined that scale clogging has occurred in the sensible heat recovery heat exchanger 17.

  That is, the exhaust gas temperature is directly detected by the temperature detection sensor 32 during the combustion operation, and the control unit 7 determines that the scale is clogged by detecting an abnormal increase in the exhaust gas temperature. Unlike hot water supply devices that determine scale clogging based on changes in heat exchange efficiency during combustion operation and devices that estimate scale clogging by estimating exhaust temperature, scale clogging can be accurately determined even during combustion operation. When determining scale clogging, it is possible to prevent fluctuations in the hot water supply amount and hot water temperature that are not intended by the user.

  Further, the temperature detection sensor 32 is a combustion that passes through the downstream side of the heat transfer tube portion closest to the combustion stage 11b that always burns during the hot water supply operation in the heat transfer tube 25 constituting the sensible heat recovery heat exchanger 17. Since it is provided in the vicinity of the fin 26 where the gas is exhausted, the exhaust temperature of the combustion gas that has passed through the portion where scale clogging is most likely to occur can be detected regardless of the combustion pattern of the burner unit 11, and the burner unit It is possible to cope with a combustion operation with a minimum combustion amount of 11.

  Further, since a latent heat recovery heat exchanger 19 for recovering the latent heat of the combustion gas is provided on the downstream side of the exhaust flow path of the sensible heat recovery heat exchanger 17, most of the heat generated by the combustion is heated to the clean water. The heat exchange efficiency of the sensible heat recovery heat exchanger 17 is reduced by adhesion of the scale within the allowable exhaust temperature range, but the latent heat recovery is possible. Even if the heat exchanger 19 heats the clean water and the heat exchange efficiency decreases as a whole, the exhaust temperature after the heat exchange in the sensible heat recovery heat exchanger 17 is directly detected. Therefore, scale clogging can be accurately determined.

Next, a mode in which the above embodiment is partially changed will be described.
[1] Although the temperature detection sensor 32 of the above-described embodiment is inserted substantially horizontally, it is brought closer to the fins in order to reduce the influence of the exhaust from the combustion section other than the combustion section that always burns when hot water is supplied. May be inserted and fixed obliquely downward, or may be inserted and fixed in a state bent downward so that the tip of the temperature detection sensor 32 approaches the fin.

[2] Although the thermocouple 32a is used as the temperature detection sensor 32 of the above-described embodiment, the present invention is not limited to this, and a thermistor may be employed.

[3] The burner unit 11 of the above-described embodiment includes ten combustion pipes 14 and is configured in a multistage system including three combustion stages 11a to 11c. However, the present invention is not particularly limited to this structure. The number of combustion stages in the burner unit and the number of combustion tubes in each combustion stage can be changed as appropriate.

[4] The hot water supply apparatus 1 of the above embodiment is an upward combustion type hot water supply apparatus in which the heat exchanger section 4 is provided above the burner section 3, but the downward combustion type hot water supply apparatus in which the top and bottom are substantially inverted. Can also be implemented.

[5] In addition, those skilled in the art can implement the present invention in various forms with various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. It is.

DESCRIPTION OF SYMBOLS 1 Hot-water supply apparatus 2 Blower fan 5 Exhaust port 7 Control unit (determination means)
11 Burner unit 17 Sensible heat recovery heat exchanger 18 Lower heat exchanger can body 19 Latent heat recovery heat exchanger 20 Upper heat exchanger can body 24 Exhaust outlet 25 Heat transfer tube 26 Fin 32 Temperature detection sensor (temperature detection means)

Claims (3)

A water heater provided with a fin-and-tube heat exchanger for heating clean water with combustion gas,
Temperature detecting means for detecting the exhaust temperature after heat exchange in the heat exchanger, and when the detected temperature detected by the temperature detecting means is equal to or higher than a set temperature, in the heat transfer tube of the heat exchanger A hot water supply apparatus comprising: determination means for determining that scale has accumulated on the surface.   The temperature detecting means is in the vicinity of the fin where the combustion gas passing through the downstream side of the heat transfer tube portion closest to the combustion portion that always burns during hot water supply operation in the heat transfer tube constituting the heat exchanger is exhausted. The hot water supply device according to claim 1, wherein the hot water supply device is provided.   The heat exchanger is a sensible heat recovery heat exchanger for recovering sensible heat of combustion exhaust, and recovers the latent heat of the combustion exhaust downstream of the exhaust flow path of the sensible heat recovery heat exchanger. The hot water supply device according to claim 1, wherein the hot water supply device is a latent heat recovery type hot water supply device provided with a latent heat recovery heat exchanger.