JPH02223765A - Temperature control device for hot water supply equipment - Google Patents

Abstract

PURPOSE:To improve an output hot water rise characteristic by estimating the flow rate of water which passes through a heat exchanger based on a falling state of a detected temperature of an output hot water temperature sensor when a specified time has passed since the start of hot water supply. CONSTITUTION:A control device 30 estimates the flow rate of water which passes through a heat exchanger based on a falling state of a detected temperature by an output hot water temperature thermistor 25 when a specified time by a timer section 33a has passed in an initial stage water capacity estimation section 33 if the start of hot water supply is detected by a water flow switch 19. A temperature conditioning control section 34 performs feed-forward control of a heating value based on an estimated initial stage water capacity, the deviation between a preset temperature by a controller 40 and a detected temperature and an estimated input water temperature memory value by a input water temperature estimation section 31. Then, a water capacity estimation section 32 compares a total heating value obtained from a detected temperature and a stored input water temperature estimated value with an integrated value of heating value output information in a memory section 32a. It is, therefore, possible to estimate the flow rate of water in an early stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a water heater that does not include a flow rate sensor for detecting the flow rate of water passing through a heat exchanger.
In particular, the temperature of hot water flowing out from the heat exchanger is detected without providing an incoming water temperature sensor that detects the temperature of water flowing into the heat exchanger. It is effective in a water heater with a simple structure that includes only an outflow temperature sensor.

[Prior art] In order to simplify the structure of the water heater, simplify the manufacturing process, and reduce manufacturing costs, a temperature control device that performs feedback control only using a hot water temperature thermistor has been designed to reduce the amount of water entering the heat exchanger. Since there is no inlet water temperature thermistor to detect the temperature or a flow rate sensor to detect the flow rate of water passing through the heat exchanger, a device with a function to improve the outlet temperature characteristics is used. It is being

In addition, in such a feedback control temperature control device, if the heating amount is directly controlled based on the unheated outflow temperature at the initial stage of hot water supply, if the amount of hot water to be supplied is small or there is after-boiling due to reheating, There is a possibility that the hot water temperature may become too high due to excessive heating. Therefore, to avoid danger, the heating amount is set to a small amount on the assumption that the amount of hot water supply is small or that the water in the heat exchanger is being heated by post-boiling, and then the feedback control system With a certain time delay due to a time constant, the amount of heating is gradually changed according to the temperature detected by the hot water temperature sensor.

[Problems to be solved by the invention] As described above, in the conventional feedback control water heater,
Information for controlling the amount of heating is provided only by the outlet hot water temperature sensor, and there is no information regarding the flow rate of water passing through the heat exchanger, so if the amount of hot water is large at the beginning of hot water supply, the amount of heating will be insufficient. Therefore, the rising temperature of the hot water is delayed, and it takes a long time for the hot water temperature to rise to the target temperature and stabilize. In particular, at the beginning of hot water reheating,
Since the amount of hot water supplied and the actual temperature of the water remaining in the heat exchanger are mutually affected, if you try to prevent overheating in such cases, the amount of heating may be insufficient when the amount of hot water supplied is large, and the temperature may be insufficient. Since the amount of heating is not applied, there is a problem that the response delay becomes even larger.

The present invention provides a water heater that performs feedback control without a flow rate sensor, and has a good rise characteristic of the outlet temperature at the initial stage of hot water supply in the case of reheating, and particularly has an excellent rise characteristic when a large amount of hot water is supplied. The purpose is to provide a temperature control device.

[Means for Solving the Problems] The present invention includes a water flow detection means for detecting water flowing into a heat exchanger, and heats the heat exchanger by a heating means in accordance with a water flow detection state of the water flow detection means. In a temperature control device for a water heater, the temperature control device controls the start and stop of the water heater, and controls the heating amount of the heating means based on temperature information detected by a temperature sensor provided at the outlet of the heat exchanger. comprising a timer for measuring a subsequent predetermined time and a flow rate estimating unit for estimating the flow rate of water passing through the heat exchanger,
The technical means of the flow rate estimating means is to estimate the flow rate based on a falling state of the temperature detected by the temperature sensor when the predetermined time has elapsed after the start of hot water supply.

[Function] Generally, in a water heater, there is a time delay between when water is detected flowing into the heat exchanger and when heating starts. on the other hand,
There is a time delay before the result of heating by the heating means appears in the tapped water temperature. This time delay varies depending on the flow rate through the heat exchanger.

Therefore, when restarting hot water supply after once stopping the hot water supply, even if the water in the heat exchanger is heated by residual heat from the heat exchanger, etc., the water flowing out from the heat exchanger must be The temperature drops once, and then the thermometer starts heating up.
Noboru appears. In this case, the downward change state of the outflow temperature changes according to the flow l passing through the heat exchanger, and when the flow rate is large, the degree of fall (gradient) is large, and when the flow rate is small, the degree of fall (gradient) is large. The present invention detects a falling state as a falling slope of the outflow temperature at a predetermined time before the temperature rise due to heating appears, and estimates the flow rate based on this.

[Effects of the Invention] According to the present invention, the flow rate is estimated based on the falling state of the detected temperature as the outflow temperature when a predetermined time has elapsed after the start of hot water supply. This state of decrease in the outflow temperature usually occurs earlier than the temperature rise associated with the start of heating, so when hot water is reheated, the flow rate decreases earlier than when hot water is normally heated without heating due to residual heat. Estimates can be made.

Therefore: Since the amount of heating can be controlled according to the flow rate at an early stage of heating, the temperature of the tapped water can be increased quickly. In particular, when the flow rate is large, a large amount of heating can be applied in accordance with the flow rate, so that the rise in the tapping temperature at a large flow rate is greatly improved compared to the conventional method.

[Example] Next, a temperature control device for a water heater according to the present invention will be described based on an example shown in the drawings.

A burner group 11 including a plurality of burners is provided in a combustor case 10 of the gas combustion water heater 1 shown in FIG. A burner group 11 is located below the combustor case 10.
A blower 12 is provided for supplying combustion air to the combustion chamber. A water tube type heat exchanger 13 is provided on one side of the burner group 11 in the combustor case 10, and water passing through the inside is heated by combustion heat from the burner group 11. In the vicinity of the burner group 11 in the combustor case 10, a sparker 14 for igniting the burner group 1] and a flame rod 15 for detecting ignition of the burner group 11 are provided. Furthermore, an exhaust port 2 is provided above the combustor case 10 for discharging combustion exhaust gas to the outside.

A nozzle pipe [6] for supplying fuel gas is provided below the burner group 11.
A plurality of fuel injection ports 46a for ejecting fuel gas are provided respectively corresponding to the respective burners.

The fuel pipe 20 that guides the fuel gas to the nozzle pipe 16 includes two electromagnetic valves 21 and 22 that allow the fuel gas to pass when energized, and adjust the amount of fuel gas supplied by controlling the supply pressure according to the energized current. Governor proportional valves 23 are provided in order from the upstream side.

A water supply pipe 17 that leads water from a water supply source (not shown) to the heat exchanger 13 is equipped with an electric water flow control device 18 for adjusting the amount of hot water supply, and a water flow switch 19 for detecting water passing through the heat exchanger 13. The heat exchanger 1 is provided in order from the upstream side.
Hot water pipe 1 that leads hot water flowing out from 3 to a hot water supply port (not shown)
7a shows the outlet temperature of hot water flowing out from the heat exchanger 13.
A hot water temperature thermistor 25 for detecting t'out is provided.

The control device 30 has a control circuit centered on a microcomputer, starts and stops combustion in a predetermined sequence according to the water flow detection state of the water flow switch 19, and has a functional configuration shown in FIG. The temperature of the hot water is controlled using only the hot water temperature thermistor 25 as a sensor.

Here, since a water inlet temperature thermistor to the heat exchanger 13 and a flow rate sensor for detecting the amount of water passing through the heat exchanger 13 are not provided, the control device 30 controls the temperature detected by the outlet water temperature thermistor 25. Inlet water temperature Tin based on T
and the amount of water W are estimated respectively.

The incoming water temperature estimating section 31 estimates the incoming water temperature 1'1n based on the temperature T detected by the outlet hot water temperature thermistor 25, and stores it in the memory 31a.

Next, a method for estimating the water inlet temperature Tin will be explained based on FIG. 3.

When the start of hot water supply is detected by the water flow switch 19 (YES in step 1), the hot water temperature thermistor 2
If the detected temperature T in step 5 changes by °C, it is possible that hot water is being reheated. Therefore, if there is a temperature gradient in the detected temperature T (NO in step 2), the inlet water temperature] 10 is not estimated.

If the temperature gradient is not detected when the start of hot water supply is detected (YES in step 2), the detected temperature T of the hot water temperature thermistor 25 and the inlet water temperature "l" are already stored in the memory 31a. Memory temperature T se
In step 3), if the detected temperature] is lower than the stored temperature TI (+-), then in step 3, YE
S) The detected temperature T is estimated as the new water inlet temperature Tin.Step 4) The stored contents of the memory 3] and a are updated (Step 5).

If the detected temperature T is higher than the stored temperature T1lel (No in step 3), a part of the temperature information of the detected temperature T is incorporated into the stored temperature Tle- to create a new water inlet temperature T.
Step 6) to estimate in, and store it at the memory temperature Tle-
(Step 5).

In step 6, the new water inlet temperature]゛tn is determined from a part of the temperature information of the stored temperature T lea and a part of the temperature information of the detected temperature T.
), a new inlet water temperature q゛+n is calculated.

The water amount estimating unit 32 estimates the amount of water Wp1 passing through the heat exchanger 13 in a steady state.

Generally, the temperature rise ΔT of hot water flowing out from the heat exchanger 13
is the result of the water being heated by the burner group 11 from the time it flows into the heat exchanger 13 to the time it flows out. Now, if we assume that it takes time for the amount of water Wu per unit time to pass through the heat exchanger 13, at this time, the total heat loss involved in the temperature rise ΔT of the hot water flowing out from the heat exchanger 13 Generally, ff1Qi can be expressed as, for example, the product of heating amount QU per unit time and heating time t (time t required for passing through the heat exchanger 13). That is, it is expressed as Qt=QuXt-(i).

Here, QuXt indicates the integration of the heating amount Qu per unit time during the heating time.

Therefore, if the total amount of heat disintegration QT is shown including the case where the heating amount changes during the heating time from time t1 to time tn and the heating amount Qu per unit time is not constant, QT = Qn + Qn-x + Qn- z+-+Qz +Qt
:Σ? Qt ■.

Here, Qn, Qn-,,Qn-,,...Q2,Q
l is each unit time tn, tn-t, tn-, ..., t
2 shows the amount of heating at t.

In addition, the total amount of heat dissipated QT by the burner group 11 is
It can be considered that the temperature increase Δ]゛ of the total amount of water U in the heat exchanger 13 according to the volume of From, ΔTXU=Σ?Qt =Qn+Qn-x+Qn-z+-+Qz +Q...
■ As a result, when the amount of heating for each unit time is integrated with time being clouded, the amount of heating is equal to the total amount of heat dissipation Qa which gives a temperature rise of ΔT to the total amount of water U in the heat exchanger 13. By calculating the total unit time until .

Furthermore, this heating time t is the time required for water to pass through the heat exchanger 13, and between the total water amount U and the water amount W in the heat exchanger 13, U=WXt...
Since there is the relationship (2), the amount of water W can be determined by W=U/l... (2).

In this case, a delay time constant due to a heating response delay may be taken into consideration.

The water amount estimating section 32 calculates the temperature "-rise ΔT" from the detected temperature T of the outlet hot water temperature thermistor 25 and the inlet water temperature Tin stored in the memory 31a of the inlet water temperature estimating section 31, and further calculates the temperature "-rise ΔT" Calculate the total amount of heat dissipation Q from the water amount U using the above formula.

On the other hand, the heating amount output information ΔQ for each predetermined unit time Δ by the temperature adjustment control unit 34, which will be described later, is stored in areas El, E2, . . . , E of the heating amount storage unit 32a shown in FIG.
Do not store the information in x sequentially and continuously, accumulate it for a predetermined period of time, and delete the information after the predetermined period of time has passed each time new information is provided.

That is, for example, the heating amount output information ΔQ for each predetermined unit time Δ by the temperature control unit 34 is as shown in FIG.
With time......, ΔQn-a, ΔQn->
, ΔQn-*, ΔQn-t, ΔQn, ΔQn+1, ΔQ
n, 2, .
However, in area E2, ΔQn-t at time Δtn-t
However, in area E3, ΔQn-z at time Δtn-2
However, in area E4, ΔQn at time Δtn-3,
However, each heating amount output information ΔQ before time Δtn is stored corresponding to each area E up to area Ex.

Then, at the next time Δtn, , as shown in B in FIG. 4, the heating amount output information ΔQn+ at the time Δtn, .
t is stored in area E1, and ΔQn is stored in area E2 below.
, ΔQn,-, is shifted to area E3, ΔQn-z is shifted to area E4, etc., and the heating amount output information ΔQ of each area E at time Δtn is similarly shifted to area Ex. be remembered.

Thereafter, similarly, the newest heating amount output information ΔQ is always stored in area E1, and the stored information in area Ex is deleted, so that the heating amount output information ΔQ for every predetermined unit time Δ is continuously stored. Memory is stored.

The water amount estimating unit 32 integrates the heating amount output information ΔQ stored in this way in order from the newest information, and calculates the sum of the predetermined unit time Δt when it becomes equal to the calculated total heat disintegration amount QT using the above formula (■). is determined as the heating time t of water flowing out from the heat exchanger 13.

Based on this heating time t, the water JL W p t of the water passing through the heat exchanger 13 is calculated from the above equation (2).

Note that the water amount WP1 estimated here is a numerical value as the average water amount W during the heating time t, and cannot represent the water and IW at each time when the hot water supply water 1w is changed successively.

Further, the water amount estimating unit 32 calculates an effective heating time t only when the stored heating amount output information ΔQ is integrated in order from the newest information to the total amount of heat disintegration QT. Therefore, for example, at the beginning of hot water supply,
Even if we try to integrate the heating amount output information ΔQ until it becomes equal to the total amount of disintegrated heat QT, the water cannot be filled before the start of hot water supply, so the estimated water JiWpt shows a much larger value than the actual water tw. The result is as shown in Figure 6.

In FIG. 6, for example, the solid line C shows the case where the amount of water is large, and the solid line C shows the case where the amount of water is small.

Here, the water amount Wp1 estimated by the water amount estimation unit 32 indicates the effective water amounts Wc and Wd as a substitute for the actual water amount W, respectively, when time tc and time td have passed after the start of hot water supply, respectively. . For this reason, from the start of hot water supply until these times t, c, and time td have passed, an appropriate heating ff1Q cannot be determined by temperature control based on water: lW p 1.

Therefore, in this embodiment, the initial water amount Wp2 passing through the heat exchanger 13 is estimated by the initial water amount estimating section 33 instead of the water amount WPz estimated by the water amount estimating section 32 only at the initial stage of hot water supply.

That is, the hot water temperature 'rout after the start of hot water supply changes in accordance with the water volume W, as shown in FIG. In the case of a small amount of water, as shown by the solid line F, the rise is slower than in the case of a large amount of water.

The initial water amount estimating unit 33 calculates the initial water 1tWp2 based on the fact that the time required for the amount of heat given to the heat exchanger 13 to appear as a change in the outlet temperature TOut differs depending on the water tw passing through. The water Jt W p 2 is estimated by measuring the elapsed time tm until a predetermined amount of heat due to heating is detected by the clock section 33a.

Here, as an indication of the given amount of heat, an integrated value P (integral value with respect to time with respect to the detected temperature) which is obtained by integrating the temperature rise ΔT of the detected temperature T with the start of hot water supply)
is calculated, and the elapsed time tm until this integrated value P reaches a predetermined fIx value P0 is measured.

This predetermined integrated value P0 is determined by the heat exchanger 13 at the start of combustion.
In Fig. 7, for example, in the case of a large amount of water, it is shown as the amount of heat corresponding to the area S1 up to time te, and in the case of a small amount of water, This is shown as the amount of heat corresponding to the area S2 up to time tf. In particular, here, in order to clearly detect the difference in the water ZW actually passing through the heat exchanger 13, a value corresponding to the amount of heating for a relatively short time after the start of combustion is set.

According to the measured elapsed time tm, the amount of water W p2 is estimated, as shown in FIG. 8.

As a result, each time measurement can be completed at a relatively early stage before the tapped water temperature becomes stable for each water amount W. In particular, in the case of a large amount of water, as shown in Figure 7, the time measurement ends much earlier than the time td when the hot water temperature stabilizes in the case of a small amount of water, and as a result, it is possible to detect a large amount of water. Can be done.

Furthermore, time 1 in Figure 7? fltc and td indicate the same times as times tc and td in FIG. 6, respectively.

Therefore, for reference, the times te and tf at which time measurement ends at each water volume in FIG. 7 are as follows:
These times are the same as times te and tf in FIG. 6, and as is clear here, these times rWJte and tf indicate that the water 31 wp estimated by the water amount estimating section 32 is at a certain level. It can be seen that this is the time taken to indicate the water amount value Wx.

Furthermore, in the initial water amount estimating section 33, in order to estimate the water amount W at the time of re-heating hot water more quickly, a time measuring section 33a that measures the elapsed time tm after the start of hot water supply is configured to estimating the amount of water before the temperature "-rise" occurs due to the start of heating. The initial time t. When measuring the temperature, it is determined whether a downward slope appears in the change in the detected temperature T, and if there is a downward slope, the water amount W is estimated based on the downward slope G and the initial water supply time is determined. The water amount W po is assumed, and the above-mentioned initial water amount WP2 is not estimated.

As shown in Fig. 9, the temperature downward slope G changes according to the water volume W, so here, the larger the downward slope G, the greater the water volume W, and the smaller the downward slope G, the lower the water volume W. , and estimate the initial water amount WPo, respectively.

The temperature control unit 34 controls the target temperature '1' Set set by the controller 40 , the outlet hot water temperature Tout detected by the outlet hot water temperature thermistor 25 , and the inlet water temperature estimation unit 3 .
1, the water amount W estimated by the water 1 estimating unit 32 and the initial water amount estimating unit 33, respectively.
pI, initial water amount WP2. W.P. The heating amount Q is determined from .

Here, immediately after the start of hot water supply, the water flow rate Ws at which the water flow switch 19 starts operating is the water volume W passing through the heat exchanger 13, the estimated water inlet temperature rtn, and the target temperature of the controller 40.
The heating amount Q is determined based on i'set.

After that, a downward slope G of the detected temperature T appears, or the integrated value reaches the predetermined integrated value P. Then, the initial water amount estimator 3
The heating amount Q is determined by using the initial water MWp2 or the initial water amount WPo estimated in step 3 as water iW, and when the time tp determined based on these water amounts Wp x and Wpo has elapsed, the water amount estimating unit 32 estimates water g,
The heating amount Q is determined by setting Wp1 to water iW.

Furthermore, when the detected temperature T of the outlet hot water temperature thermistor 25 rises to a constant temperature, feedback control is performed based on the detected temperature T.

In this feedback control, by setting the time constant of the feedback control system each time based on the water volume WPI estimated by the water volume estimating section 32 described above, stable temperature control is performed and hunting etc. are prevented from occurring. There is. Therefore, even if the time constant of the feedback control system changes due to a change in the amount of water, stable temperature control can be achieved.

Note that the heating amount Q of the temperature control section 34 is based on the heating amount output information Δ
As Q, the above-mentioned heating amount storage unit 3 is
2a.

The drive unit 35, based on the heating amount Q of the temperature control unit 34,
The blower 12 and the governor proportional valve 23 are driven and controlled. Here, a voltage based on the heating amount Q by the temperature control unit 34 is applied to the blower 12 to drive it, and the blower 12 is detected.
The current value to the governor proportional valve 23 is controlled based on the rotation speed of the governor proportional valve 23.

Furthermore, in order to prevent the water supply amount from exceeding the heating capacity, the control device 30 adjusts the opening degree of the electric water flow control device 18 based on the temperature 1' detected by the outlet hot water temperature thermistor 25 to control the passing flow rate. Restrict.

Note that the controller 40, which allows the user to arbitrarily set the target temperature Tset, is installed according to the specifications of the water heater, and when the controller 40 is provided, the target temperature TS13t can be set according to the user's operation. is set and the controller 40 is not installed, a constant temperature (for example, 60° C.) is set as the target temperature 'rset.

Next, temperature control in the gas combustion type water heater 1 of this embodiment having the above configuration will be explained with reference to FIG. 10, focusing on estimation of water iW.

When a user opens a hot water tap (not shown) provided downstream of the hot water supply pipe 17a, water passes through the water supply pipe 17 and flows into the heat exchanger 13.

When hot water supply is detected by the water flow switch 19 (YES in step 11), ignition control is performed in a predetermined sequence to start combustion, and at the same time, the timer 33a starts measuring the elapsed time tm (step 12). ,
At this time, only when the outlet water temperature TOut does not change, the inlet water temperature Tin is estimated according to the temperature T detected by the outlet hot water temperature thermistor 25, and the temperature 'l'me stored in the memory 31a is
- is updated.

After the start of time measurement, when the initial time t0 has elapsed (step 13
YES in step 14), it is determined whether or not there is a downward slope G of the detected temperature T, and if there is a downward slope G, YES in step 14), it is assumed that hot water is being reheated, and based on the downward slope G, the initial The water amount W po is estimated (step 15).

If there is no downward slope G (NO in step 14)
), the temperature rise ΔT of the detected temperature T of the outlet hot water temperature thermistor 25 every predetermined unit time Δ is integrated to calculate the integrated value P (step 16), and when the integrated value P becomes equal to or greater than the predetermined integrated value P0 (step 17: YES), timekeeping section 33a
The time measurement ends at the elapsed time t, m (step 18).
, the initial water amount WP 2 based on the measured elapsed time tm
is estimated (step 19).

When the initial water amount W po or the initial water amount W p2 is estimated, an initial time tp is set based on each initial water amount wp, wp2 (step 20).

When the initial time tp has elapsed (step 21), control using the water amount WP1 estimated by the water amount estimating section 32 is started (step 22), and thereafter the heating amount Q is determined based on the water amount Wpl.

The water amount Wr)i obtained here is used as a time constant in feedback control, so if, for example, the outlet temperature changes due to a change in flow rate, the heating amount Q is corrected by the time constant according to the change in flow rate. Therefore, hunting and the like associated with correction of the heating amount are less likely to occur.

If the hot water tap is closed to stop the hot water supply (YES in step 23), combustion will stop.

As described above, according to this embodiment, the amount of water is quickly estimated at the initial stage of hot water supply, so that an appropriate amount of heating is determined.

In particular, in the case of reheating hot water, water production is estimated earlier than in the case of starting normal hot water supply, so the larger the amount of water, the earlier the temperature control is started based on the estimated amount of water. Therefore,
The rising temperature of hot water is improved compared to the conventional case.

In addition, in this embodiment, only the outlet hot water temperature thermistor is provided as a sensor, and no sensor is provided at the inflow part of the heat exchanger, so the structure of the water heater is simplified and the manufacturing process can be simplified. At the same time, although the structure is equivalent to that of a simple feedback control water heater, extremely stable hot water temperature characteristics similar to feedforward control can be obtained.

In the above embodiment, a water heater using a burner that uses gas as fuel is shown, but a burner that uses other fuel such as oil may be used. It can also be a vessel.

[Brief Description of the Drawings] Figure 1 is a functional block diagram showing the functional configuration of the control device for the gas combustion water heater of this embodiment, and Figure 2 is a schematic diagram of the gas combustion water heater of this embodiment. A schematic configuration diagram, FIG. 3 is a flowchart for explaining the process of estimating the inlet water temperature in the control device of this embodiment, FIG. 4 is an area map showing the storage area of the heating amount storage unit of this embodiment, and FIG. FIG. 6 is a time chart showing changes in the heating amount output information in the control device of this embodiment. FIG. 6 is a time chart 1 showing changes in the estimated water amount by the water amount estimation unit of this embodiment. FIG. Time chart 1 showing changes in temperature with respect to water volume
8 is a characteristic diagram showing the relationship between the elapsed time tm measured by the timer in the initial water amount estimating section of this embodiment and the estimated initial water amount W p2, and FIG. 9 is a characteristic diagram showing the change in outlet temperature during refilling. Time chart shown corresponding to water volume, No. 10
The figure is a flowchart showing the process of estimating the amount of water in this embodiment. In the figure, 11... burner group (heating means), 13... heat exchanger, 19... water flow switch (water flow detection means), 2
5... Hot water temperature thermistor (temperature sensor), 30...
Control device W (temperature control device for water heater), 33... initial water amount estimating section (flow rate estimating means), 33a... time measuring section (time measuring means).

Claims (1)

[Scope of Claims] 1) Water flow detection means for detecting water flowing into the heat exchanger is provided, and heating of the heat exchanger by the heating means is started and stopped according to the water flow detection state of the water flow detection means. In the temperature control device for a water heater, the temperature control device controls the heating amount of the heating means based on temperature information detected by a temperature sensor provided at an outflow portion of the heat exchanger. The flow rate estimating unit includes a timer for measuring time and a flow rate estimating unit for estimating the flow rate of water passing through the heat exchanger, and the flow rate estimating unit is configured to measure the temperature detected by the temperature sensor when the predetermined period of time has elapsed after the start of hot water supply. A temperature control device for a water heater, characterized in that the flow rate is estimated based on a falling state of the water heater.