JP2013181739A - Device and method for controlling water level of feed water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feed water heater water level control device capable of maintaining a water level of a feed water heater to a target water level.SOLUTION: A feed water heater water level control device includes: a plurality of water level detection units 11, 12 for detecting a water level signal of a feed water heater 10; a water level adjustment valve 14 for adjusting a water level of the feed water heater 10; a control signal generation unit for finding an opening command signal of the water level adjustment valve 14, based on the water level signal detected by the water level detection units 11, 12 and a target water level; a multiplication unit 24 for multiplying the opening command signal found by the control signal generation unit for a predetermined acquisition period with a predetermined multiplication period and for acquiring a multiplication value; a drift diagnosis circuit 22 for diagnosing generation of drift in the water level detection units 11, 12, by comparing a normal multiplication value of the opening command signal found when the water level detection units 11 and 12 are normal, with the multiplication value created by the multiplication unit 24; and a switch selection circuit 25 for separating the water level detection unit generating the drift from the acquisition destination of the water level signal when a diagnosis is made that the drift has been generated.

Description

  The present invention relates to a feed water heater water level control device that controls the water level of a feed water heater such as a power plant and a control method therefor.

  A power supply facility such as a nuclear power plant or a thermal power plant is provided with a feed water heater. For example, in a nuclear power plant, a feed water heater is used for the purpose of heating the feed water to a nuclear reactor using extraction (steam) from a steam turbine to improve the thermal efficiency of the turbine plant.

  When the heat exchange with the feed water is finished, the steam becomes drain and is used for heat exchange in the next stage feed water heater. The feed water heater includes a water level control device that controls the water level of the feed water heater. The water level control device is a device that controls the opening of the water level control valve so that the water level of the feed water heater becomes the target water level. The water level control valve is installed until the drain of the feed water heater enters the feed water heater of the next stage (see, for example, Patent Document 1).

  The feed water heater has a plurality (for example, two) of water level transmitters for measuring the water level. The water level signal obtained from each water level transmitter is input to the control circuit. The control circuit derives a valve opening degree command for the water level control valve based on the deviation between the water level signal of the average value of each water level signal and the target water level. The control circuit can maintain the water level of the feed water heater at the target water level by controlling the water level control valve.

Japanese Patent Publication No. 4-23286

  In the water level transmitter of the water level control device, the reference level of the water level signal changes with time, and a drift may occur in which a deviation occurs between the actual water level and the detected water level. When drift occurs, the control circuit controls the water level control valve based on the average value of the erroneous water level signal, and performs control to keep the water level of the feed water heater at the target water level. The water level of the feed water heater is not the target water level, and there is a problem that it cannot be controlled correctly.

  For example, when a drift in which the detected water level shifts in the upward direction occurs in the water level transmitter, a water level larger than the actual water level is detected. The control circuit opens the water level control valve to lower the water level of the feed water heater. This drop in water level can affect the thermal efficiency of the power plant.

  Further, when a drift in which the detected water level shifts in the downward direction occurs in the water level transmitter, a water level smaller than the actual water level is detected. The control circuit closes the water level control valve to raise the water level of the feed water heater. This rise in water level may cause moisture to flow into the turbine.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a feed water heater water level control device and a control method thereof that can maintain the water level of the feed water heater at a target water level.

  In order to solve the above-described problem, the feed water heater water level control device according to the present invention includes a plurality of water level detection units that detect a water level signal related to the water level of the feed water heater, and a water level that adjusts the water level of the feed water heater. A control valve, a control signal generator for obtaining an opening command signal for commanding the opening of the water level control valve based on the water level signal detected by the water level detector and the target water level, and the control signal generator Normalization of the opening command signal obtained when the opening command signal obtained every predetermined acquisition cycle is integrated at a predetermined integration cycle and the integrated value is acquired, and the water level detection unit is normal A drift diagnosis unit that compares the integrated value with the integrated value created by the integrating unit and diagnoses the occurrence of drift in the water level detection unit, and when the drift is diagnosed, the drift is Occur Characterized in that a signal switching unit for disconnecting the water level detection unit from the acquisition source of the water level signal.

  In the feed water heater water level control device and the control method thereof according to the present invention, the water level of the feed water heater can be maintained at the target water level.

The block diagram which shows 1st Embodiment of the feed water heater water level control apparatus which concerns on this invention. The graph which shows the change of a water level signal when the drift in which a detected water level shifts to an ascending direction generate | occur | produces in one water level transmitter. The graph which shows the change of the water level accompanying control of the water level control valve when the change of the detected water level shown in FIG. 2 arises. The graph which shows the time transition of the valve opening degree command signal which an integration circuit acquires, when the drift from which a detected water level shifts to the raise direction generate | occur | produces in one water level transmitter. The graph which shows the time transition of the integration value of the valve opening degree command signal which an integration circuit acquires when the drift from which a detected water level shifts to the raise direction generate | occur | produces in one water level transmitter. The graph which shows the time transition of the integrated value of the valve opening degree command signal preserve | saved in the database previously when the water level transmitter is normal. Explanatory drawing at the time of comparing the integrated value of an actual valve opening command signal, and a reference value. The flowchart explaining the drift diagnostic process implemented by the feed water heater water level control apparatus in 1st Embodiment. The block diagram which shows the modification of 1st Embodiment of a feed water heater water level control apparatus. The block diagram which shows 2nd Embodiment of the feed water heater water level control apparatus which concerns on this invention. The graph which shows the time transition of the integrated value of the valve opening degree command signal before and after the determination circuit estimates the occurrence of drift in which the detected water level shifts in the upward direction. The graph which shows the time transition of the integrated value of the valve opening degree command signal before drift generation. Explanatory drawing at the time of comparing the integrated value of the valve opening degree command signal after drift generation, and a reference value. The flowchart explaining the drift diagnostic process implemented by the feed water heater water level control apparatus in 2nd Embodiment.

[First Embodiment]
A feed water heater water level control device and a control method thereof according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram showing a first embodiment of a feed water heater water level control device according to the present invention.

  The case where the feed water heater water level control device (hereinafter referred to as “water level control device”) 1 in this embodiment is applied to a nuclear power plant will be described as an example. The water level control device 1 is provided in a feed water heater 10 provided in a plurality of stages in a nuclear power plant. The feed water heater 10 is used for the purpose of improving the thermal efficiency of the turbine plant.

  The feed water heater 10 heats the feed water supplied to the nuclear reactor using the extraction (steam) from the steam turbine. The bleed air from the steam turbine is drained when the heat exchange with the feed water is completed, and is used for heat exchange in the next stage feed water heater.

  The water level control device 1 mainly includes water level transmitters 11 and 12, a control circuit 13, a water level control valve 14, and an electropneumatic converter 15.

  The water level transmitters 11 and 12 (water level detection unit) generate a water level signal indicating the water level of the drain 17 detected in the feed water heater 10 and supply it to the average value calculation circuit 21 and the drift diagnosis circuit 22 of the control circuit 13. To do.

  The control circuit 13 includes an average value calculation circuit 21, a drift diagnosis circuit 22, a database 23, an integration circuit 24, and a switch switching circuit 25.

  The average value calculation circuit 21 obtains an average value of the water level based on the water level data of the drain 17 obtained from the water level transmitters 11 and 12. The drift diagnosis circuit 22 diagnoses whether or not a drift has occurred in the water level transmitter 11 or the water level transmitter 12. The integrating circuit 24 (integrating unit) generates a valve opening command signal that is generated based on the difference between the target water level of the feed water heater 10 and the current water level and used to command the valve opening at every period Δt. To do. The integrating circuit 24 acquires the integrated value Y of the valve opening command signal every period t.

  The database 23 is an integrated value (normal integrated value) of a normal valve opening command obtained when there is no drift caused by the water level transmitters 11 and 12 and the device side (change in flow characteristics of the water level control valve 14 or the like). ) In advance.

  The switch switching circuit 25 switches the acquisition source of the water level signal used for obtaining the valve opening degree command signal. Specifically, the switch switching circuit 25 switches the water level signal acquisition source to any one of the average value calculation circuit 21, the water level transmitter 11, and the water level transmitter 12.

  The electropneumatic converter (E / P) 15 converts the valve opening command signal into an air pressure signal and supplies it to the water level control valve 14. The water level control valve 14 is an air-operated valve, and is provided between the feed water heater 10 and the next stage feed water heater. The water level control valve 14 opens and closes while the opening is adjusted based on the valve opening command signal.

  The valve opening command signal is a signal indicating the opening amount of the water level control valve 14. An arithmetic circuit for obtaining a difference between the water level signal output from the switch switching circuit 25 and the target water level is referred to as a valve control signal generator.

  Next, in the water level control device 1, a change in the water level signal when drift occurs in one of the water level transmitters 11 will be described.

  FIG. 2 is a graph showing a change in the water level signal when a drift in which the detected water level shifts in the upward direction occurs in one of the water level transmitters 11.

  FIG. 3 is a graph showing a change in the water level accompanying the control of the water level control valve 14 when the change in the detected water level shown in FIG. 2 occurs.

  When the water level transmitter 12 is normal and the drift in which the detected water level shifts in the upward direction occurs in the water level transmitter 11, the average value of the water level shifts in the upward direction. Accordingly, the control circuit 13 mistakenly recognizes that the water level has risen above the target water level, and opens the water level adjustment valve 14 in order to lower the water level of the feed water heater 10.

  Here, the control circuit 13 suitably performs control to maintain the water level of the feed water heater 10 at the target water level even when drift occurs in the water level transmitter 11.

  FIG. 4 is a graph showing a time transition of the valve opening degree command y acquired by the integrating circuit 24 when a drift in which the detected water level shifts in the upward direction occurs in one of the water level transmitters 11.

  FIG. 5 is a graph showing a time transition of the integrated value Y of the valve opening degree command y acquired by the integrating circuit 24 when a drift in which the detected water level shifts upward occurs in one of the water level transmitters 11.

  The integrating circuit 24 is generated from the difference between the target water level of the feed water heater 10 and the current water level, and acquires a valve opening command signal (valve opening command) for commanding the valve opening every sampling period Δt. . In FIG. 4, the integration circuit 24 acquires a valve opening command signal yn (y1, y2, y3,..., Yn) for each period Δt. Further, the integrating circuit 24 acquires the integrated value Y (y1 + y2 + y3 +... + Yn) of the valve opening command signal for each period t. As shown in FIG. 5, the integration circuit 24 acquires a time transition of the integration value Y for each time t. When a drift occurs in the water level transmitter 11 in which the detected water level shifts upward, the integrated value Y of the valve opening command signal increases in proportion to the passage of time.

  FIG. 6 is data that is stored in the database 23 in advance, and is a graph showing the time transition of the integrated value Y of the valve opening command signal when the water level transmitters 11 and 12 are normal.

  The database 23 stores the time transition of the integrated value Y when the water level transmitters 11 and 12 are normal (when no drift occurs). The drift diagnostic circuit 22 acquires a reference value based on the data stored in the database 23. The reference value is, for example, an integrated value range (Ya ≦ Y ≦ Yb) obtained from the minimum value Ya and the maximum value Yb of the integrated value Y of the valve opening command signal. The drift diagnosis circuit 22 compares the integrated value Y of the valve opening command signal shown in FIG. 5 with this reference value.

  FIG. 7 is an explanatory diagram when comparing the integrated value Y of the actual valve opening command signal with a reference value.

  The drift diagnosis circuit 22 determines whether or not the integrated value Y of the actual valve opening command signal falls within the reference value. When the integrated value Y of the actual valve opening command signal falls within the reference value, the drift diagnosis circuit 22 diagnoses that no drift has occurred in the water level transmitter. On the other hand, when the integrated value Y of the actual valve opening command signal does not fall within the reference value, the drift diagnosis circuit 22 diagnoses that drift has occurred in the water level transmitter.

  When the drift diagnosis circuit 22 determines that the drift in which the detected water level shifts in the upward direction occurs, the drift is generated in the water level transmitter 11 of which the detection result is high among the water level transmitter 11 and the water level transmitter 12. Diagnose that

  The switch switching circuit 25 receives the diagnosis result of the drift diagnosis circuit 22 and uses only the normal (no drift) water level transmitter 12 as the water level acquisition source as data for generating the valve opening command signal. Switch to. That is, the switch switching circuit 25 disconnects the water level transmitter 11 in which the drift has occurred, and uses the water level obtained only from the normal water level transmitter 12 to generate the valve opening command signal.

  In addition, when the drift which the detected water level shifts to the downward direction generate | occur | produces in the water level transmitter 11 or the water level transmitter 12, the integrated value Y of the valve opening degree command signal for every period t preserve | saved at the integration circuit 24 is with time progress. Get smaller. When the integrated value Y of the valve opening command signal deviates in a direction that becomes smaller than the reference value, the drift diagnosis circuit 22 determines that a drift occurs in which the detected water level is shifted downward. Further, the drift diagnosis circuit 22 diagnoses that a drift has occurred in the water level transmitter whose detection result has a low value.

  Next, the drift diagnosis process executed by the water level control device 1 will be described using a flowchart.

  FIG. 8 is a flowchart illustrating the drift diagnosis process performed by the feed water heater water level control device 1 according to the first embodiment.

  In step S1, the integration circuit 24 acquires the integration value Y. The acquired integrated value Y is supplied to the drift diagnosis circuit 22. In step S2, the drift diagnosis circuit 22 compares the integrated value Y obtained in the integrated value acquisition step S1 with the reference value. In step S3, the drift diagnosis circuit 22 determines whether or not the obtained integrated value Y is outside the reference value. That is, the drift diagnosis circuit 22 obtains the integrated value acquisition step S1 from the integrated value range obtained from the minimum value Ya and the maximum value Yb of the integrated value Y of the normal valve opening degree command signal stored in the database 23. It is determined whether or not the integrated value Y is off. If the drift diagnosis circuit 22 determines that the obtained integrated value Y is included in the reference value range (NO in step S3), it determines that no drift has occurred in the water level transmitters 11 and 12 in step S4. .

  On the other hand, if the drift diagnosis circuit 22 determines that the obtained integrated value Y is outside the range of the reference value, does the integrated value Y deviate from the reference value in a direction that increases with time in step S5? Determine whether or not. When the drift diagnosis circuit 22 determines that the integrated value Y deviates from the reference value in the direction in which the integrated value Y increases (YES in step S5), in step S6, the switch switching circuit 25 sets the water level indicating a high value. Disconnect the transmitter. That is, the switch switching circuit 25 switches the water level acquisition source, which is data for generating the valve opening command signal, to a normal water level transmitter.

  On the other hand, when the drift diagnosis circuit 22 determines that the integrated value Y deviates from the reference value in the direction in which the integrated value Y decreases (NO in step S5), the switch switching circuit 25 sets a low value in step S7. Disconnect the water level transmitter shown.

  Thereafter, the water level control device 1 adjusts the water level adjustment valve 14 based on the water level acquired from the normal water level transmitter, and maintains the water level of the feed water heater 10 at the target value.

  The water level control device 1 and the control method thereof according to the first embodiment can diagnose the occurrence of drift by comparing the integrated values of the valve opening degree command signal between the normal time and the time when the drift occurs. Further, the water level control device 1 can preferably diagnose whether the generated drift is a drift that shifts in the upward direction or the downward direction, and thereafter, a water level signal that is used to generate a valve opening command signal Can be switched to only a signal obtained from a normal water level transmitter.

  As a result, the water level control device 1 can maintain the water level of the feed water heater 10 at the target water level.

  The switch switching circuit 25 may switch the acquisition source of the water level signal used for generating the valve opening degree command signal at a rate.

  FIG. 9: is a block diagram which shows the modification of 1st Embodiment of a feed water heater water level control apparatus.

  This water level control device 1a is different from the water level control device 1 of FIG. 1 in that a rate switching circuit 25a is provided instead of the switch switching circuit 25 of the control circuit 13a. Configurations and portions corresponding to the water level control device 1 of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The rate switching circuit 25a is smooth and continuous when switching the water level signal used for generating the valve opening command signal to any one of the signals obtained from the average value calculation circuit 21, the water level transmitter 11 or the water level transmitter 12. Switch. The rate switching circuit 25a can prevent the water level disturbance of the feed water heater due to the rapid opening and closing operation of the water level control valve 14 when switching the acquisition source of the water level signal, and can reduce the influence on the plant thermal efficiency and the turbine body. .

[Second Embodiment]
2nd Embodiment of the feed water heater water level control apparatus and its control method which concern on this invention is described with reference to an accompanying drawing.

  FIG. 10: is a block diagram which shows 2nd Embodiment of the feed water heater water level control apparatus which concerns on this invention.

  The difference between the feed water heater water level control device (water level control device) 51 of the second embodiment and the water level control device 1 of the first embodiment is that a determination circuit 68 is provided before the drift diagnosis circuit 62 of the control circuit 53. is there. Components and parts corresponding to those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The determination circuit 68 compares the deviation between the water level transmitter 11 and the water level transmitter 12 with a predetermined determination value, and if the deviation deviates from the determination value, any of the water level transmitter 11 or the water level transmitter. 12, it is estimated that drift has occurred. The determination value is the maximum value of the water level deviation acquired when the water level transmitters 11 and 12 are functioning normally. The determination circuit 68 stores in advance a deviation when the water level transmitters 11 and 12 are functioning normally, and automatically sets the deviation as a determination value. The determination circuit 68 supplies a drift estimation signal to the drift diagnosis circuit 62 when the occurrence of drift is estimated.

  FIG. 11 is a graph showing the time transition of the integrated value Y of the valve opening command signal before and after the determination circuit 68 estimates the occurrence of drift in which the detected water level shifts in the upward direction.

The drift diagnosis circuit 62 regards the time when the drift estimation signal is supplied to the drift diagnosis circuit 62 as the time when the drift has occurred. For example, the integrated value Y of the valve opening command signal is largely different before and after the drift in which the detected water level shifts in the upward direction.

  FIG. 12 is a graph showing the time transition of the integrated value Y of the valve opening command signal before the occurrence of drift.

  The drift diagnosis circuit 62 determines a device-side factor (change in flow characteristic of the water level control valve 14 or the like) from the tendency of the integrated value Y of the valve opening command signal stored in the integrating circuit 24 before the detection of the drift estimation signal (before the occurrence of drift). ) To set a reference value that excludes the amount of change in the valve opening command signal.

  In FIG. 12, the valve opening command signal gradually rises due to factors on the device side even before the drift occurs. The drift diagnosis circuit 62 obtains an approximate value of the slope of the integrated value Y of the valve opening command signal before the occurrence of drift. The drift diagnosis circuit 62 sets a region within a predetermined range from this inclination as a reference value.

  The drift diagnosis circuit 62 sets the reference value from the maximum value and the minimum value of the integrated value Y of the valve command signal obtained before the occurrence of the drift without considering the change amount of the valve opening command signal as a factor on the equipment side. May be.

  The drift diagnosis circuit 62 compares the set reference value with the integrated value Y of the valve opening command signal stored in the integrating circuit 24 after detection of the drift estimation signal (after the occurrence of drift).

  FIG. 13 is an explanatory diagram when the integrated value Y of the valve opening command signal after the occurrence of the drift is compared with the reference value.

  The drift diagnosis circuit 62 determines whether or not the integrated value Y after the occurrence of drift falls within the reference value. When the integrated value Y of the actual valve opening command signal falls within the reference value, the drift diagnosis circuit 62 diagnoses that the water level transmitters 11 and 12 are not drifting. On the other hand, when the integrated value Y of the actual valve opening command signal does not fall within the reference value, the drift diagnosis circuit 62 diagnoses that drift has occurred in the water level transmitters 11 and 12.

  Since the operation of the water level control device 51 after the drift diagnostic circuit 62 detects the drift is the same as in the first embodiment, the description thereof is omitted here.

  Next, the drift diagnosis process executed by the water level control device 51 will be described using a flowchart.

  FIG. 14 is a flowchart illustrating a drift diagnosis process performed by the feed water heater water level control device 51 according to the second embodiment.

  In step S <b> 11, the determination circuit 68 determines whether or not a drift has occurred in the water level transmitters 11 and 12. In step S12, when the determination circuit 68 determines that no drift has occurred, the determination circuit 68 returns to step S11. In step S <b> 13, when the determination circuit 68 determines that a drift has occurred, the determination circuit 68 generates a drift estimation signal and supplies the drift estimation signal to the drift diagnosis circuit 62.

  In step S <b> 14, the drift diagnosis circuit 62 sets a reference value based on the integrated value Y of the valve opening command signal before the occurrence of drift stored in the integrating circuit 24. In step S15, the drift diagnosis circuit 62 determines whether or not the obtained integrated value Y is outside the reference value. Since the processing after step S15 is substantially the same as steps S2 to S7 of the drift diagnosis processing described in the first embodiment, the same parts as those in FIG.

  The water level control device 51 and its control method according to the second embodiment set a reference value for diagnosing the occurrence of drift from the change in the valve opening command signal before the occurrence of drift, in addition to the effects exhibited by the first embodiment. can do. Thereby, the water level control device 51 can diagnose the occurrence of drift in the water level transmitters 11 and 12 more accurately.

  In addition, the water level control device 51 can set a reference value from which the amount of change in the valve opening command due to equipment-side factors such as a change in the flow rate characteristic of the water level control valve 14 is excluded. The water level control device 51 can more accurately diagnose the occurrence of drift in the water level transmitters 11 and 12, and can eliminate the influence of drift on water level control.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, the method for comparing the actual integrated value of the valve opening command signal with the integrated value at normal time is not limited to the method described above. Further, the number of water level transmitters is not limited to two and can be set as appropriate.

1, 1a, 51 Feed water heater water level control device 10 Feed water heater 11, 12 Water level transmitters 13, 13a, 53 Control circuit 14 Water level control valve 21 Average value calculation circuit 22, 62 Drift diagnosis circuit 23 Database 24 Integration circuit 25 Switch Switching circuit 25a rate switching circuit 68 determination circuit

Claims (5)

A plurality of water level detection units for detecting a water level signal related to the water level of the feed water heater;
A water level control valve for adjusting the water level of the feed water heater;
A control signal generator for obtaining an opening command signal for commanding the opening of the water level control valve based on the water level signal detected by the water level detector and the target water level;
An integration unit that integrates the opening command signal obtained for each predetermined acquisition period by the control signal generation unit at a predetermined integration period and acquires an integrated value;
Drift diagnosis for comparing the normal integrated value of the opening command signal obtained when the water level detecting unit is normal and the integrated value created by the integrating unit to diagnose the occurrence of drift in the water level detecting unit And
A feed water heater water level control device comprising: a signal switching unit that disconnects the water level detection unit in which the drift has occurred from the acquisition source of the water level signal when it is diagnosed that the drift has occurred. Comparing a plurality of deviations of the water level transmitters with a deviation when the water level transmitters are normal, further comprising a determination unit that estimates the occurrence of drift in the water level transmitters,
The drift diagnosis unit sets the normal integrated value based on the integrated value of the opening command signal before estimation of drift occurrence by the determination unit, and the integrated value of the opening command signal after estimation of drift occurrence The feed water heater water level control apparatus according to claim 1, wherein the water level controller of the feed water heater diagnoses occurrence of drift in the water level detection unit by comparing the normal time integrated value. The drift diagnostic unit considers the amount of change in the valve opening command due to a factor of a device other than the water level transmitter based on the integrated value of the valve opening command before the occurrence of drift generation by the determination unit. The feed water heater water level control device according to claim 1, wherein a time reference value is set. The feed water heater water level control device according to claim 1, wherein the signal switching unit switches at a rate when switching the acquisition source of the signal. A water level detection step of detecting a water level signal related to the water level of the feed water heater from a plurality of water level detection units;
A water level adjusting step for adjusting the water level of the feed water heater;
A control signal generation step for obtaining an opening command signal for commanding the opening of the water level control valve based on the water level signal and the target water level;
An integration step of integrating the opening degree command signal obtained for each predetermined acquisition cycle by the control signal generation step at a predetermined integration cycle and acquiring an integrated value;
Drift diagnosis for comparing the normal integrated value of the opening command signal obtained when the water level detecting unit is normal and the integrated value created by the integrating unit to diagnose the occurrence of drift in the water level detecting unit Steps,
A water supply heater water level control method comprising: a signal switching step of disconnecting the water level detection unit where the drift has occurred from the acquisition source of the water level signal when it is diagnosed that the drift has occurred.

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