Direct pressure water heater

Abstract

To provide a direct pressure water heater capable of performing hot water filling at a low temperature lower than a lower limit hot water supply temperature with a simple structure.SOLUTION: A direct pressure water heater includes: a burner 2 capable of adjusting a heating power; a heat exchanger 6 heating water in a water supply pipe 7 and sending to a hot-water supply pipe 8; a bypass pipe 9 bypassing the heat exchanger 6; a mixing valve 10 supplying hot water as hot water at a hot water supply temperature; hot water filling setting means 19 for setting a hot water filling set temperature Tb as a temperature after hot water filling in a bathtub 50, and a hot water filling set amount Lb; and a control section 22 for controlling the burner 2 and the mixing valve 10. When the hot water filling set temperature Tb is lower than a lower limit hot water supply temperature TL at which continuous hot water supply is enabled by combustion of a minimum heating power of the burner 2, the control section 22 pours water of a predetermined water filling amount Lw in a water supply operation mode through the bypass pipe 9 without through the heat exchanger 6, and pours hot water of a predetermined hot water supply amount Lh into the bathtub 50 in a hot water supply operation mode of heating to the lower limit hot water supply temperature TL through the heat exchanger 6.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a direct-pressure water heater.

Background Art

[0002] Conventionally, this type of device includes a heat exchanger for heating water in a water supply pipe by the combustion heat of a burner for hot water supply or bath hot water supply, a bypass pipe that bypasses the heat exchanger from the water supply pipe and is connected to a hot water supply pipe, and a mixing valve that mixes high-temperature hot water from the hot water supply pipe and low-temperature water from the bypass pipe to adjust the temperature to an appropriate temperature. When the hot water supply faucet provided at the end of the hot water supply pipe is opened, hot water adjusted to the temperature specified by the user is discharged. (For example, Patent Document 1)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, on a hot day such as in summer, when it is desired to fill a bathtub with hot water at a low set temperature (for example, 30°C), if this set temperature is too low, when the supply water temperature is high (for example, 28°C), the amount of heat required to heat to the set temperature is small, so the flow rate flowing through the heat exchanger is small, and it becomes difficult to adjust the combustion power. Therefore, if the combustion power of the burner is reduced and the set temperature of the outlet temperature of the heat exchanger is reduced (for example, 30°C), almost the entire amount of water in the water supply pipe flows through the heat exchanger, and the surface temperature of the heat exchanger becomes lower than the outside air temperature (for example, 30°C), and there is a risk that condensation will occur on the outer wall of the heat exchanger, leading to corrosion and damage of the heat exchanger, and there is a problem that it is difficult to supply hot water or fill the bathtub at a low set temperature. Therefore, a normal direct-pressure water heater sets a lower limit hot water supply temperature (for example, 38°C), which is the lowest temperature at which continuous hot water supply is possible based on the minimum combustion power of the burner and a predetermined water supply amount. Therefore, it was not possible to fill the bath with water at a temperature lower than the lower limit hot water supply temperature.

[0005] The present invention has been made in view of such a background, and an object thereof is to provide a direct pressure type water heater that can fill the bath with water at a temperature lower than the lower limit hot water supply temperature with a simple configuration.

Means for Solving the Problems

[0006] The present invention has been made to achieve the above object. In claim 1, a burner capable of adjusting the combustion power, a water supply pipe, a water supply temperature detection means for detecting the water temperature of the water flowing through the water supply pipe, a hot water supply pipe, a hot water supply temperature detection means for detecting the water temperature of the hot water flowing through the hot water supply pipe, a heat exchanger for heating the water from the water supply pipe by the combustion of the burner and sending it to the hot water supply pipe, a bypass pipe branched from the water supply pipe, bypassing the heat exchanger and merging into the hot water supply pipe, a mixing valve for mixing the high-temperature water from the heat exchanger and the water supply from the bypass pipe to supply hot water as warm water having a hot water supply temperature higher than the water supply temperature from the bypass pipe, a flow rate detection means provided in the water supply pipe upstream of the bypass pipe or in the hot water supply pipe downstream of the mixing valve, a hot water filling setting means for setting a hot water filling set temperature which is the temperature after filling the bath with hot water and a hot water filling set amount to be filled into the bath, and a control unit for controlling the burner and the mixing valve to perform a hot water filling operation for the bath. The control unit, when the hot water filling set temperature is lower than the lower limit hot water supply temperature at which continuous hot water supply is possible by the combustion of the minimum combustion power of the burner, injects a predetermined amount of water into the bath in a water supply operation mode passing through the bypass pipe without passing through the heat exchanger, and then injects a predetermined amount of hot water into the bath in a hot water supply operation mode heating the water from the water supply pipe to the lower limit hot water supply temperature through the heat exchanger.

[0007] In claim 2, the sum of the predetermined water filling amount and the predetermined hot water supply amount is the hot water filling set amount, and the control unit divides the predetermined water filling amount and the predetermined hot water supply amount into a plurality of times and alternately repeats the water supply operation mode and the hot water supply operation mode.

[0008] In claim 3, in the water supply operation mode, when the temperature of the water detected by the water supply temperature detection means changes, the control unit performs a correction to increase the predetermined water filling amount in the water supply operation mode according to the change, or performs a correction to change the lower limit hot water supply temperature in the hot water supply operation mode to a first hot water supply temperature higher than the lower limit hot water supply temperature.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a direct pressure type water heater that can fill hot water at a temperature lower than the lower limit hot water supply temperature with a simple configuration.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0011] The first embodiment according to the present invention will be described with reference to FIGS. 1 to 4.

[0012] Reference numeral 1 denotes a direct pressure type water heater according to the first embodiment, 2 denotes a burner as a heating means that burns kerosene as fuel to generate a flame and can adjust the heating power, 3a denotes a hot water supply faucet for pouring hot water into a bathtub, 3b denotes a hot water supply faucet provided in a kitchen, a washroom, etc., 4 denotes an operation remote control as an operation means for remotely operating the direct pressure type water heater 1 installed outside the bathroom, 5 denotes an operation remote control installed in the bathroom, and 50 denotes a bathtub.

[0013] Reference numeral 6 denotes a fin-and-tube heat exchanger having heat exchange fins 44. A water supply pipe 7 connected to a water pipe is provided upstream of the heat exchanger 6, and a hot water supply pipe 8 terminating at hot water supply faucets 3a and 3b is provided downstream of the heat exchanger 6.

[0014] Reference numeral 9 denotes a bypass pipe branched from the water supply pipe 7 for connecting the water supply pipe 7 and the hot water supply pipe 8 and bypassing the heat exchanger 6. A mixing valve 10 for mixing the high-temperature water heated by the heat exchanger 6 and the water from the bypass pipe 9 is provided at the connection portion between the hot water supply pipe 8 and the bypass pipe 9. By adjusting the valve opening degree of the valve body inside, the mixing valve 10 adjusts the mixing ratio of hot water and water, and supplies hot water at a temperature higher than the temperature of the water supplied from the bypass pipe 9 as warm water having a hot water supply temperature.

[0015] Reference numeral 11 denotes water supply temperature detection means such as a thermistor provided in the water supply pipe 7 for detecting the temperature of the water flowing through the water supply pipe 7. Reference numeral 12 denotes water supply flow rate detection means such as a flow sensor provided in the water supply pipe 7 upstream of the bypass pipe 9 for detecting the water supply flow rate. Reference numeral 13 denotes heat exchange outlet temperature detection means provided in the hot water supply pipe 8 upstream of the mixing valve 10. Reference numeral 14 denotes hot water supply temperature detection means such as a thermistor for detecting the temperature of the hot water mixed by the mixing valve 10. Reference numeral 15 denotes a hot water supply pipe branched from the hot water supply pipe 8 on the downstream side of the mixing valve 10 for supplying hot water to the bathtub 50. Reference numeral 38 denotes a heat exchange temperature sensor for detecting the temperature of the heat exchanger 6.

[0016] The operation remote controller 4 is provided with a hot water supply setting means 19 for setting the temperature and the hot water supply amount after filling the bathtub 50 with hot water. The hot water supply setting means 19 includes a hot water supply temperature setting switch 20 for setting the hot water supply setting temperature Tb and a hot water supply amount setting switch 21 for setting the hot water supply amount Lb to be filled in the bathtub 50. Further, the operation remote controller 4 is provided with a hot water supply switch 21a as a hot water supply instruction means for instructing the start of the hot water supply operation to the bathtub 50, a display unit 4a for notification, and a buzzer 4b. The operation remote controller 5 is also provided with the same switches as those of the operation remote controller 4.

[0017] 22 is a control unit 22 that controls the burner 2 and the mixing valve 10 to perform a hot water filling operation into the bathtub 50. The control unit 22 is connected to the operation remote control 4 and the operation remote control 5 wirelessly or by wire to communicate with each other, and receives signals from each sensor of the direct pressure type water heater 1 and signals from the operation remote control 4 and the operation remote control 5, and controls the driving of each actuator. Furthermore, the control unit 22 has a target temperature setting means 23 for setting the target temperature of the heat exchange outlet of the hot water flowing out from the heat exchanger 6. When discharging hot water at the set temperature set by the hot water supply temperature setting switch 20, the temperature of the hot water detected by the heat exchange outlet temperature detection means 13 is the target temperature of the heat exchange outlet set by the target temperature setting means 23. The combustion amount of the burner 2 is controlled so as to be. Furthermore, the heating amount given to the water flowing through the heat exchanger 6 by the burner 2 is controlled, and the opening degree of the mixing valve 10 is controlled so that the temperature of the hot water detected by the hot water outlet temperature sensor 14 becomes the set temperature set by the hot water supply temperature setting switch 20.

[0018] 42 is a storage unit for storing the number of hot water filling times and the like.

[0019] Next, the low-temperature hot water filling operation of this first embodiment will be described.

[0020] In the present invention, when there is an instruction for the hot water filling operation by the hot water filling switch 21a, if the hot water filling set temperature Tb is lower than the lower limit hot water supply temperature TL (for example, 38°C) at which continuous hot water supply is possible by the combustion of the minimum firing power of the burner 2, after filling the bathtub 50 with water of a predetermined water filling amount Lw in a water supply operation mode passing through the bypass pipe 9 without passing through the heat exchanger 6, the water from the water supply pipe 7 is heated to the lower limit hot water supply temperature TL (38°C) through the heat exchanger 6. Then, hot water of a predetermined hot water supply amount Lh is poured into the bathtub 50 in a hot water supply operation mode. Here, the sum of the predetermined water filling amount Lw and the predetermined hot water supply amount Lh is set to be the hot water filling set amount Lb.

[0021] Referring to FIG. 3, when there is an instruction for the water filling operation at a water filling set temperature Tb lower than the lower limit hot water supply temperature TL, if the water filling set temperature Tb set by the water filling setting means is, for example, 30°C and the water filling set amount Lb is, for example, 150 L, first, water with a water supply temperature Tw (for example, 28°C) detected by the water supply temperature detection means 11 is poured into the bathtub 50. When supplementing the necessary amount of heat (300 kcal) insufficient to reach the water filling set temperature Tb (for example, 30°C) from this water supply temperature Tw by adding hot water at the lower limit hot water supply temperature TL (for example, 38°C), after supplying water with a predetermined water filling amount Lw (120 L by calculation) obtained by the calculation described later, hot water with a predetermined hot water supply amount Lh (30 L by calculation) is supplied to complete the water filling.

[0022] Here, assuming the hot water supply temperature for water filling is Th, the relationship among the water filling set amount Lb, the water filling set temperature Tb, the water supply temperature Tw, and the predetermined hot water supply amount Lh can be expressed by the following formula (1). Lb(Tb - Tw) = Lh(Th - Tw) ··· Formula (1) Note that the relationship among the predetermined water filling amount Lw, the predetermined hot water supply amount Lh, and the water filling set amount Lb is given by the following formula (2). Lb = Lw + Lh ··· Formula (2) From the following formula (3) derived therefrom, the predetermined hot water supply amount Lh is calculated by multiplying the water filling set amount Lb by the quotient of the difference between the water filling set temperature Tb and the water supply temperature Tw and the difference between the hot water supply temperature Th and the water supply temperature Tw. Lh = (Tb - Tw)Lb / (Th - Tw) ··· Formula (3) Here, the lower limit hot water supply temperature TL is substituted for the hot water supply temperature Th. And the predetermined water filling amount Lw is calculated as the value obtained by subtracting the predetermined hot water supply amount Lh from the water filling set amount Lb according to Formula (2).

[0023] In the present invention, the predetermined water filling amount Lw and the predetermined hot water supply amount Lh are divided into a number of divisions N (for example, N = 3 times), and the water supply operation mode and the hot water supply operation mode are alternately repeated to fill the bathtub 50 with water. When the water filling of the water filling set amount Lb is finally completed, the hot water temperature in the bathtub 50 becomes the water filling set temperature Tb. For example, when the total hot water filling quantity Lba, which is the total quantity for hot water filling for convenience, is set to 150 L and the number of divisions N = 3, 150 L is divided into three times, and the hot water filling quantity Lb for each time is 50 L, and the water supply operation mode and the hot water supply operation mode are alternately performed three times.

[0024] Furthermore, in the present invention, even when the water supply temperature Tw changes during the water supply operation mode, by controlling as follows, the hot water filling set temperature Tb and the hot water filling quantity Lb set by the hot water filling setting means 19 are achieved. That is, the control unit 22 sets the temperature of the water detected by the water supply temperature detection means 11 at the start point of the water supply operation mode as the first detection temperature Tw1, and sets the temperature of the water detected by the water supply temperature detection means 11 at the time when the predetermined water filling quantity Lw is filled up at the end point of the water supply operation mode before the start of the hot water supply operation mode as the second detection temperature Tw2. When changing from the first detection temperature Tw1 to the second detection temperature Tw2, in response to this change, for example, when the water supply temperature rises and Tw2 > Tw1, a correction for increasing the predetermined water filling quantity Lw in the water supply operation mode is implemented. Conversely, when the water supply temperature drops and Tw2 < Tw1, a correction for changing the lower limit hot water supply temperature TL in the hot water supply operation mode to the first hot water supply temperature T1 higher than the lower limit hot water supply temperature TL is implemented.

[0025] This will be described with reference to FIG. 4.

[0026] In step S1, the hot water filling set temperature Tb (for example, 30°C) and the total hot water filling quantity Lba (for example, 150 L) are set by the hot water filling setting means 19. In step S2, in response to the setting in step S1, the number of divisions N is set. Here, the number of divisions N is an integer of 1 or more, and is set according to the hot water filling quantity Lb. The larger the hot water filling quantity Lb, the larger the number of divisions N is set. Here, N = 3 will be described. That is, from the total hot water filling quantity Lba (150 L) and the number of divisions N = 3, the hot water filling quantity Lb for each divided time is 50 L, and this is performed three times. Then, the number counter n of the number of divisions N is set to the initial value (n = 1), and the user is notified to open the hot water supply faucet 3a for pouring hot water into the bathtub 50. In step S3, when the flow rate detection means 12 detects a flow rate equal to or higher than the minimum flow rate, water injection into the bathtub 50 is started, and the process proceeds to steps after S3.

[0027] In step S4, as the initial water supply temperature Tw in the water supply operation mode, the first detected temperature Tw1 (assuming summer, for example, 28°C) of the water flowing into the water supply pipe 7 by the water supply temperature detection means 11 is stored in the storage unit 42. In step S5, when the first detected temperature Tw1 (28°C) is set as Tw, the hot water filling set temperature Tb (30°C), the hot water filling set amount Lb (50L), and the lower limit hot water supply temperature TL (for example, 38°C), the predetermined water filling amount Lw (40L) and the predetermined hot water supply amount Lh (10L) are calculated from equations (2) and (3). In step S6, the flow rate counter is reset, and the angle of the mixing valve 10 is set to 100% toward the bypass pipe 9 (step S7) so that no water flows to the heat exchanger 6 side.

[0028] In step S8, it is confirmed whether the predetermined water filling amount Lw (40L) has been injected into the bathtub 50. If the predetermined water filling amount Lw (40L) has been injected, the second detected temperature Tw2 of the water flowing into the water supply pipe 7 by the water supply temperature detection means 11 is detected (step S9).

[0029] In step S10, it is determined whether the second detected temperature Tw2 is lower than the first detected temperature Tw1. If it is lower (for example, Tw2 = 27°C), since the water supply temperature has dropped and the predetermined water filling amount Lw (40L) has already been injected, if the lower limit hot water supply temperature TL (38°C) is used to inject the predetermined hot water supply amount Lh (10L) in the hot water supply operation mode as it is, the heat quantity calculated in step S5 will be insufficient and the temperature after hot water filling will not reach the hot water filling set temperature Tb (30°C). Therefore, in steps S11 and S12, the necessary heat quantity is recalculated using the following equation (4) under the condition of the predetermined hot water supply amount Lh (10L), the hot water supply temperature Th is calculated, and the hot water temperature to be injected in the hot water supply operation mode is determined. Th = (Tb - Tw)Lb / Lh + Tw ··· Equation (4) If the second detected temperature Tw2 is 27°C, substituting Tw2 for Tw, the hot water supply temperature Th will be 42°C. Thus, when the second detected temperature Tw2 becomes lower than the first detected temperature Tw1, the predetermined hot water supply amount Lh (10 L) is not changed, and correction is performed to change the temperature of the hot water to be supplied to a hot water supply temperature Th (42 °C) higher than the lower limit hot water supply temperature TL, and the process proceeds to the hot water supply operation mode after step S17.

[0030] In step S13, it is determined whether the second detected temperature Tw2 is higher than the first detected temperature Tw1. If it is higher (for example, Tw2 = 29 °C), since the hot water supply temperature has increased, if the lower limit hot water supply temperature TL (38 °C) is used to pour the predetermined hot water supply amount Lh (10 L) in the hot water supply operation mode, the temperature after filling will exceed the heat quantity calculated in step S5 and the temperature after filling will exceed the filling set temperature Tb (30 °C). Therefore, in step S14, the required heat quantity is recalculated, and the predetermined water filling amount Lw and the predetermined hot water supply amount Lh are calculated using equations (2) and (3) so that the filling set temperature Tb (30 °C) is reached when pouring the hot water at the lower limit hot water supply temperature TL (38 °C) in the hot water supply operation mode. Correction is performed to increase the predetermined water filling amount Lw and decrease the predetermined hot water supply amount Lh. If the second detected temperature Tw2 is 29 °C, by calculation, the predetermined hot water supply amount Lh is 5.6 L and the predetermined water filling amount Lw is 44.4 L. Thus, when the second detected temperature Tw2 becomes higher than the first detected temperature Tw1, the lower limit hot water supply temperature TL (38 °C), which is the temperature of the hot water to be supplied, is not changed, correction is performed to increase the predetermined water filling amount Lw and decrease the predetermined hot water supply amount Lh, and it is confirmed whether the predetermined water filling amount Lw (44.4 L) changed in step S15 has been reached. If the predetermined water filling amount Lw (44.4 L) has been reached, the process proceeds to step S16.

[0031] In step S13, if there is no difference between the second detected temperature Tw2 and the first detected temperature Tw1, the correction is not performed and the process proceeds to step S16.

[0032] In step S16, the hot water temperature for hot water supply in the hot water supply operation mode is set to the lower limit hot water supply temperature TL (38 °C). In step S17, burner 2 is ignited, and in step S18, the flow counter is reset. In step S19, the predetermined hot water supply amount Lh (10 L or 5.6 L) is poured, and in step S20, burner 2 is stopped.

[0033] In step S21, it is checked whether the loop counter n for the number of divisions N has reached N (3 times). If not, the loop counter n is incremented by +1 in step S22. If the loop counter n has reached the number of divisions N, in step S23, the completion of water filling is notified by the display unit 4a and the buzzer 4b of the operation remote control 4 and the operation remote control 5. In step S24, the user closes the faucet, and the low-temperature water filling is completed.

[0034] Accordingly, when the water filling set temperature Tb is lower than the lower limit water supply temperature TL (for example, 38°C) at which continuous water supply is possible by the combustion of the minimum firing power of the burner 2, after injecting water of a predetermined water filling amount Lw into the bathtub 50 in a water supply operation mode passing through the bypass pipe 9 without passing through the heat exchanger 6, hot water of a predetermined hot water supply amount Lh is injected into the bathtub 50 in a hot water supply operation mode heating the water from the water supply pipe 7 to the lower limit hot water supply temperature TL (38°C) through the heat exchanger 6. Therefore, when the firing power of the burner 2 is reduced and the setting of the heat exchange outlet temperature detection means 13 of the heat exchanger 6 is lowered (for example, to 30°C), substantially all the water volume of the water supply pipe 7 flows into the heat exchanger 6, the surface temperature of the heat exchanger 6 becomes lower than the outside air temperature (for example, 30°C), and dew condensation occurs on the outer wall of the heat exchanger 6 without causing corrosion or damage to the heat exchanger 6, and water filling can be performed.

[0035] Also, since the hot water supply operation mode injects hot water into the bathtub 50 at the lower limit hot water supply temperature TL (for example, 38°C), compared to the case of raising the temperature of the bathtub 50 by a high-temperature hot water pitcher (for example, 43°C), injecting hot water at the lower limit hot water supply temperature TL which is low, heat radiation loss from the hot water supply pipe 8 and the water filling pipe 15 can be minimized.

[0036] Also, even for a dedicated hot water supply machine without a stirring function by the circulation pump of the bathtub water filling circuit, it is possible to perform water filling in a plurality of divisions by alternately repeating the water supply operation mode and the hot water supply operation mode to perform water filling of the water filling set amount Lb. Therefore, the temperature of the hot water in the bathtub 50 is not hotter at the top and colder at the bottom. After water filling, the inside of the bathtub 50 reaches an appropriate and uniform water filling set temperature Tb, and a comfortable bath can be taken.

[0037] In addition, since the hot water supply operation mode is performed after the water supply operation mode is initially performed, when the hot water supply operation mode is initially performed, it is possible to prevent the bathroom from being heated by pouring hot water into the bathtub 50, and comfortable hot water filling can be performed for bathing in summer.

[0038] In addition, when the number of divisions N is 2 or more, even if the second detected temperature Tw2 (for example, 28 ° C) of the first time is lower than the first detected temperature Tw1 (for example, 27 ° C) of the second time, in the calculation of the required heat amount in step S5 of the second time with the number counter n = 2, in the first water supply operation mode and the hot water supply operation mode, the predetermined water filling amount Lw (40 L) and the predetermined hot water supply amount Lh (10 L) are used, and in the second water supply operation mode and the hot water supply operation mode, the predetermined water filling amount Lw is 36.4 L and the predetermined hot water supply amount Lh is 13.6 L, and hot water filling is performed. At the completion of the second hot water supply operation mode, hot water filling can be performed so that the temperature in the bathtub 50 becomes the hot water filling set temperature Tb (30 ° C).

[0039] Similarly, when the number of divisions N is 2 or more, even if the second detected temperature Tw2 (for example, 28 ° C) of the first time is higher than the first detected temperature Tw1 (for example, 29 ° C) of the second time, in the calculation of the required heat amount in step S5 of the second time with the number counter n = 2, in the first water supply operation mode and the hot water supply operation mode, the predetermined water filling amount Lw (40 L) and the predetermined hot water supply amount Lh (10 L) are used, and in the second water supply operation mode and the hot water supply operation mode, the predetermined water filling amount Lw is 44.4 L and the predetermined hot water supply amount Lh is 5.6 L, and hot water filling is performed. At the completion of the second hot water supply operation mode, hot water filling can be performed so that the temperature in the bathtub 50 becomes the hot water filling set temperature Tb (30 ° C).

[0040] Note that the other configurations used in this embodiment are presented as an example and are not intended to limit the scope of the invention. It can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0041] 1: Direct-pressure water heater 2: Burner 6: Heat exchanger 7: Water supply pipe 8: Hot water supply pipe 9: Bypass pipe 10: Mixing valve 11: Water supply temperature detection means 12: Flow rate detection means 19: Hot water filling setting means 22: Control unit 50: Bathtub Lb: Hot water filling set amount Lh: Predetermined hot water supply amount Lw: Predetermined water filling amount T1: First hot water supply temperature TL: Lower limit hot water supply temperature Tb: Hot water filling setting temperature Th: Hot water supply temperature Tw: Water supply temperature

Claims

1. A burner with adjustable firing power, A water supply pipe, Water supply temperature detection means for detecting the temperature of water flowing through the water supply pipe, A hot water supply pipe, Hot water supply temperature detection means for detecting the temperature of hot water flowing through the hot water supply pipe, A heat exchanger that heats the water from the water supply pipe by combustion of the burner and sends it to the hot water supply pipe, A bypass pipe branched from the water supply pipe, bypassing the heat exchanger and merging into the hot water supply pipe, A mixing valve that mixes the high-temperature water from the heat exchanger and the water supply from the bypass pipe, and supplies hot water as warm water with a hot water supply temperature higher than the temperature of the water supply from the bypass pipe, Flow rate detection means provided in the water supply pipe upstream of the bypass pipe or in the hot water supply pipe downstream of the mixing valve, Hot water filling setting means for setting the hot water filling set temperature, which is the temperature after filling the bathtub with hot water, and the hot water filling quantity to the bathtub, A control unit that controls the burner and the mixing valve to perform a hot water filling operation to the bathtub, Comprising, The control unit, When the hot water filling set temperature is lower than the lower limit hot water supply temperature at which continuous hot water supply is possible by combustion of the minimum firing power of the burner, After filling a predetermined amount of water into the bathtub in a water supply operation mode passing through the bypass pipe without passing through the heat exchanger, Hot water of a predetermined hot water supply amount is poured into the bathtub in a hot water supply operation mode of heating the water from the water supply pipe through the heat exchanger to the lower limit hot water supply temperature, A direct pressure type water heater characterized by the above.

2. The sum of the predetermined water filling quantity and the predetermined hot water supply quantity is the hot water filling set quantity, The control unit, Divides the predetermined water filling quantity and the predetermined hot water supply quantity into a plurality of times, and alternately repeats the water supply operation mode and the hot water supply operation mode, The direct pressure type water heater according to claim 1, characterized by the above.

3. The control unit, In the water supply operation mode, when the temperature of the water detected by the water supply temperature detection means changes, according to the change, Implement a correction to increase the predetermined water filling quantity in the water supply operation mode, or, Implement a correction to change the lower limit hot water supply temperature in the hot water supply operation mode to a first hot water supply temperature higher than the lower limit hot water supply temperature, The direct pressure type water heater according to claim 1 or claim 2, characterized by the above.

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