Water heater

Abstract

A water heater includes a burner, a heat exchanger, a passing water quantity control unit, a temperature detection unit, and an operation control unit. The operation control unit performs the output hot water temperature control by configuring the passing water quantity control unit to have a predetermined passing water quantity that is further restricted compared with a predetermined water quantity, and upon confirmation that a predetermined release condition of the passing water restriction is satisfied, executes the passing water control in which the passing water quantity is returned back to the predetermined water quantity by gradually releasing the passing water restriction, and the operation control unit, when a predetermined undershoot factor of the detected temperature is confirmed while the passing water quantity is returned back to the predetermined water quantity, temporarily stops the release of the restriction of the passing water quantity until the undershoot factor is resolved.

Claims

1. A water heater comprising: a burner; a water supply pipe; a hot water outlet pipe; a heat exchanger coupled to the water supply pipe and the hot water outlet pipe, the heat exchanger being heated with the burner; a passing water quantity control unit disposed in the water supply pipe, the passing water quantity control unit controlling a passing water quantity in the heat exchanger; a temperature detection unit that detects a hot water temperature inside the hot water outlet pipe; and an operation control unit that executes an output hot water temperature control in which a detected temperature obtained from the temperature detection unit is caused to match a set temperature by a combustion control of the burner and an operational control of the passing water quantity control unit, wherein the operation control unit, upon confirmation that a predetermined start condition of a passing water restriction is satisfied at a start of a hot water supply, performs the output hot water temperature control by configuring the passing water quantity control unit to have a predetermined passing water quantity that is further restricted compared with a predetermined water quantity, and upon confirmation that a predetermined release condition of the passing water restriction is satisfied, executes the passing water control in which the passing water quantity is returned back to the predetermined water quantity by gradually releasing the passing water restriction, and the operation control unit, when a predetermined undershoot factor of the detected temperature is confirmed while the passing water quantity is returned back to the predetermined water quantity, temporarily stops the release of the restriction of the passing water quantity until the undershoot factor is resolved.

2. The water heater according to claim 1, further comprising: a plurality of the burners; wherein the operation control unit switchingly controls the burners to a predetermined combustion stage during the output hot water temperature control, and the undershoot factor is the switching control of the combustion stages.

3. The water heater according to claim 1, wherein the start condition of the passing water restriction is that the detected temperature is lower than the set temperature by a predetermined temperature by comparing the detected temperature with the set temperature.

4. The water heater according to claim 1, wherein the release condition of the passing water restriction is that a difference between the detected temperature and the set temperature is within a predetermined temperature range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a water heater.

(2) FIG. 2A is a flowchart of an operation control of the water heater.

(3) FIG. 2B is a flowchart of an operation control of the water heater.

(4) FIG. 3 is a graph showing a passing water control and change in output hot water temperature.

(5) FIG. 4 is a graph showing a conventional passing water control and change in output hot water temperature.

(6) FIG. 5A is a graph showing a switching control of combustion stages of burners when passing water is restricted.

(7) FIG. 5B is a graph showing a switching control of combustion stages of burners when the restriction of the passing water is released.

DETAILED DESCRIPTION

(8) The following describes an embodiment of the disclosure based on the drawings.

(9) FIG. 1 is a schematic diagram illustrating an example of water heater. A water heater 1 includes a combustion chamber 2 that is formed within an apparatus main body of the water heater 1 and has an air supply fan 3. The combustion chamber 2 internally includes a plurality (here three units with respective different combustion capacities) of burners 4, 4 . . . and a heat exchanger 5. The burners 4 burn mixed gas of fuel gas and primary air from the air supply fan 3. The heat exchanger 5 is heated with a combustion of the burners 4. The heat exchanger 5 is coupled to a water supply pipe 6 and a hot water outlet pipe 7. A main solenoid valve 9 and a gas proportional valve 10 are disposed in a gas pipe 8 to the burners 4. The gas pipe 8 includes branch pipes to the respective burners 4. The branch pipes branch from the gas pipe 8 and include respective switching solenoid valves 11, 11 . . . . Each of the valves is controllable with a controller 12 as an operation control means. An ignitor 13, an ignition electrode 14, and a flame rod 15 are used.

(10) Between the water supply pipe 6 and the hot water outlet pipe 7, a bypass pipe 16 that bypasses the heat exchanger 5 is coupled. The water supply pipe 6 has an upstream side with respect to a coupling position with the bypass pipe 16. In the upstream side, a water quantity sensor 17 and a water servo 18 are disposed. The water quantity sensor 17 detects a water quantity flowing in a whole apparatus. The water servo 18 serves as a passing water quantity control means. At the coupling position with the bypass pipe 16, a bypass servo 19 that controls the water quantity to the bypass pipe 16 is disposed. The water quantity sensor 17, the water servo 18, and the bypass servo 19 are each electrically coupled to the controller 12. On the other hand, the hot water outlet pipe 7 is coupled to a hot water tap 20. The hot water outlet pipe 7 includes thermistors 21 and 22 that detects temperatures of hot water in a downstream side and an upstream side (a side of outlet from the heat exchanger 5), respectively, with respect to a coupling position of the bypass pipe 16. The thermistors 21 and 22 are electrically coupled to the controller 12. A remote control 23 is configured to perform a setting operation of, for example, a set temperature.

(11) An operation of the water heater 1 will be described based on a flowchart in FIGS. 2A and 2B.

(12) First, the hot water tap 20 is opened to pass water within the apparatus. When the passing water is detected (a signal obtained from the water quantity sensor 17 confirms that the passing water quantity flowing inside the apparatus exceeds an ignition water quantity) at S1, the controller 12 starts an ignition operation at S2. That is, a pre-purge is performed by causing the air supply fan 3 to rotate. The main solenoid valve 9 and the switching solenoid valve 11, and the gas proportional valve 10 are each opened to supply gas to the burner 4 and the ignitor 13 is operated to perform an ignition control of the burner 4. The ignition of the burner 4 is confirmed with the flame rod 15.

(13) Next, at S3, the controller 12 determines whether a restriction operation of the passing water is necessary or not. The restriction operation of the passing water is determined to be necessary when a preliminarily set start condition of the passing water restriction is satisfied. The preliminarily set start condition here is that a difference between an output hot water temperature obtained from the thermistor 21 as a temperature detection means and the set temperature set with the remote control exceeds, for example, 10 C. On the other hand, when it is determined that the restriction operation of the passing water is not necessary here, the operation proceeds to S12.

(14) When it is determined that the restriction operation of the passing water is necessary at S3, the water servo 18 is set to a position where a predetermined water quantity is restricted by a predetermined quantity (for example, 63% of the predetermined water quantity) at S4. The controller 12 continuously changes a gas quantity by controlling a degree of opening of the gas proportional valve 10 in accordance with the difference between the output hot water temperature (detected temperature) detected with the thermistor 21 and the set temperature set with the remote control 23. Thus, the controller 12 performs an output hot water temperature control in order to cause the output hot water temperature to match the set temperature.

(15) Then, at S5, it is determined whether a release condition of the passing water restriction is satisfied or not. Here, it is satisfied when the difference between the output hot water temperature and the set temperature is, for example, within 3 C.

(16) When the release condition of the passing water restriction is satisfied, a release of the passing water restriction is started at S6. In other words, a control to gradually return the water servo 18 back to the predetermined water quantity is performed.

(17) While the release of the passing water restriction is controlled, it is determined whether there is an undershoot factor or not by a determination at S7. The undershoot may occur, for example, when switching of the combustion stages of the burners 4 is performed and a water quantity detected with the water quantity sensor 17 is changed (undershoot factors). When there is no undershoot factor, the operation proceeds to S11.

(18) Here, when the undershoot factor is confirmed, the operation of the water servo 18 is stopped at S8 to temporarily stop the release operation of the passing water restriction. This temporary stop is continued until confirming a resolution of the undershoot factor (a termination of switching of the combustion stages of the burners 4 or a stabilized flow rate) at the subsequent S9.

(19) When the undershoot factor is resolved at S9, the release of the passing water restriction is resumed at S10. At S11, it is determined whether a termination condition of the release of the passing water restriction is satisfied (for example, when the output hot water temperature matches the set temperature and when a predetermined time passes after the start of the hot water supply) or not. Here, when the termination condition of the release of the passing water restriction is satisfied, the controller 12 returns the water servo 18 back to the position of the predetermined water quantity at S12 and continues the output hot water temperature control as it is. When the termination condition of the release of the passing water restriction is not satisfied, the operation returns to S7.

(20) When the passing water is no longer detected at S13 due to a closure of the hot water tap 20, the controller 12 closes each of the main solenoid valve 9, the switching solenoid valve 11, and the gas proportional valve 10 at S14 to extinguish the fire of the burner 4. The air supply fan 3 is caused to rotate for a certain period of time to execute a fire extinguishing operation in which a post-purge is performed.

(21) FIG. 3 is, similarly to FIG. 4, a graph showing a restriction control of the passing water quantity at the start of the hot water supply and change in the output hot water temperature in the above-described configuration. As is apparent here, when switching of the combustion stages of the burners 4 is performed twice between t3 and t4 like FIG. 5B, the release operation of the passing water restriction is temporarily stopped (passing water quantity constant portions A and A in FIG. 3). Accordingly, compared with a case where the release operation of the passing water restriction is not stopped, a relatively large heat amount can be provided to the passing water quantity. Therefore, a fluctuation of the output hot water temperature that is increasing is reduced (a portion T1 in FIG. 3). It is seen that the output hot water temperature is linearly changed with respect to FIG. 4 and an occurrence of the undershoot is inhibited.

(22) Thus, according to the water heater 1 of the above-described configuration, the controller 12 performs the output hot water temperature control by configuring the water servo 18 to have the predetermined passing water quantity restricted compared with the predetermined water quantity upon confirmation that the predetermined start condition of the passing water restriction is satisfied at the start of the hot water supply. The controller 12 executes the passing water control in which the passing water quantity is returned back to the predetermined water quantity by gradually releasing the passing water restriction upon confirmation that the predetermined release condition of the passing water restriction is satisfied. When the predetermined undershoot factor of the output hot water temperature is confirmed while the passing water quantity is returned back to the predetermined water quantity, the release of the restriction of the passing water quantity is temporarily stopped until the undershoot factor is resolved. Thus, even though, for example, switching of the combustion stages of the burners 4 is performed when the restriction of the passing water quantity is released, the undershoot does not occur, thereby ensuring performing a stable output hot water temperature control.

(23) Here in particular, the undershoot factor is the switching control of the combustion stages of the burners 4. Therefore, even in the case where a plurality of stages of the burners 4 are disposed, the undershoot at the start of the hot water supply can be effectively inhibited.

(24) The start condition of the passing water restriction is that the output hot water temperature is lower than the set temperature by 10 C. or more by comparing the output hot water temperature with the set temperature. Therefore, even in the case of what is called the cold start, the reach time to the set temperature can be reduced, thereby leading to the conserved water and gas.

(25) Furthermore, the release condition of the passing water restriction is that the difference between the output hot water temperature and the set temperature is within 3 C. Therefore, the passing water quantity can be returned back to the predetermined water quantity at an appropriate timing.

(26) In the above-described configuration, the start condition of the passing water restriction is that the difference between the output hot water temperature and the set temperature exceeds 10 C. However, the difference can be set to a value other than 10 C. Also, the start condition of the passing water restriction is not limited to this condition but may be when five minutes or more passes after the last termination of the operation. Furthermore, the start condition of the passing water restriction may be determined to be necessary at a first operation after turning on the power or may be when a plurality of these conditions meet.

(27) Similarly, the release condition of the passing water restriction is not limited to the condition that the difference between the output hot water temperature and the set temperature is within 3 C. but the difference can be changed as necessary and other conditions can also be set.

(28) The configuration of the water heater itself is not limited to the above-described content. The disclosure is applicable to a water heater as long as the water heater includes the passing water quantity control means, such as the water servo. The water heater may include not only a water heater with more or less stages of the burners, but also, for example, a water heater of a type without a bypass pipe, a water heater of a type provided with a bath side circuit that is configured to fill hot water in a bath tub and reheat by including a heat exchanger for bath, and a water heater of a type provided with a heat exchanger for a latent heat recovery.

(29) It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.