JPH0158431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a late-night electric water heater that boils water using electric power late at night, keeps it warm, and uses it until the next midnight.

As is well known, water heaters that use cheap late-night electricity have been widely used. Conventional late-night electric water heaters of this type are configured to always heat a specified amount of water in a hot water tank to a constant temperature (for example, 85° C.) using late-night electric power. However, the amount of hot water actually used and the required temperature usually vary greatly depending on whether or not a bath is taken, the season, and the water temperature. However, conventional water heaters that store a fixed amount of hot water at a fixed temperature each day have the following disadvantages. In other words, the amount of heat lost from the hot water tank is a function of the temperature difference between the inside and outside of the hot water tank, and naturally the higher the water temperature, the greater the loss, resulting in a decrease in thermal efficiency. Therefore, in the past, thermal efficiency significantly decreased, especially when the amount of hot water used was small.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to realize that the amount of hot water used and the required temperature of hot water in general households change daily, but these changes are affected by seasonal factors, water temperature, etc. By focusing on the fact that there is a correlation with extremely gradual changes in conditions over time, and by optimizing heating control on a daily basis based on the remaining hot water temperature and water temperature in the hot water tank, the hot water in the hot water tank is being used more than necessary. To provide a control device for a late-night power water heater, which prevents the water heater from being heated to a high temperature, creates a temperature state with little heat loss commensurate with the usage conditions, and improves thermal efficiency.

In order to achieve the above object, the present invention includes a measuring means for measuring the hot water temperature at the upper part of the hot water tank and a water temperature at the lower part of the hot water tank, a setting means for setting the lowest water temperature, and a heating target temperature. and a storage means for storing, and prior to starting heating control using late-night electric power, a predetermined value is stored based on the difference between the set minimum water temperature and the measured water temperature, and the measured water temperature. The calculation is performed and the stored heating target temperature of the previous day is corrected, the corrected heating target temperature is stored again, and the heating is performed so that the heating target temperature and the measured hot water temperature match. It is characterized by controlling.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows the configuration of a late-night electric water heater according to the present invention. The hot water tank 1 is a vertically long tank, with a water supply pipe 2 connected to its bottom and a hot water pipe 3 connected to its top.
The outflow from the hot water tank 1 is supplemented from the water supply pipe 2, so that the hot water tank 1 is always filled with hot water. An electric heater 4 is installed near the bottom of the hot water tank 1.
The electric heater 4 heats the hot water inside, and due to the difference in specific gravity of the hot water, it is substantially separated into hot water in the upper part and water in the lower part. Also hot water tank 1
Inside, a water temperature sensor 5 for detecting the upper water temperature and a water temperature sensor 6 for detecting the lower water temperature are disposed.

The control device 7 is mainly composed of a microcomputer, and controls the outputs of the hot water temperature sensor 5 and the water temperature sensor 6, a mode setting device 8, and a minimum hot water temperature setting device 9.
and 10 settings, and the midnight power switch 11
A signal indicating whether there is late-night power from Heating control is performed. The mode setter 8 is a switch for selecting any one of four control modes: high mode, medium mode, low mode, and off mode. As will be described later, the high mode controls the maximum hot water temperature at full capacity, and the off mode does not substantially heat the water. The control of the present invention is not applied in these two modes. The control according to the invention is applied in medium mode and low mode. The difference between medium mode and low mode is the difference in the above-mentioned minimum hot water temperature set value; in the medium mode, the value set in the minimum hot water temperature setting device 9 is the value set in the minimum hot water temperature setting device 9, and in the low mode, the value is set in the minimum hot water temperature setting device 10. The respective values are adopted.

FIG. 2 is a general flowchart of the control program executed by the control device 7. In the following description, it is assumed that there is no power outage and that the mode setting device 8 is not operated late at night.
In FIG. 2, first in step S1, the presence or absence of late-night power is determined based on a signal from the late-night power switch 11, and the system waits until the late-night power becomes available. When late night power is available, step S2
Then, the outputs of the hot water temperature sensor 5 and the water temperature sensor 6 are taken into the control device 7, and the hot water temperature and water temperature in the hot water tank 1 are measured. In the next step S3, a heating target temperature is calculated based on the measured hot water temperature and water temperature and control data (described later) stored in the control device 7. In the next step S4, the late-night power switch is controlled based on the calculated heating target temperature, and the electric heater 4 is energized until the hot water temperature measured by the hot water temperature sensor 5 matches the target temperature. Heat the hot water in tank 1.

Next, the details from step S2 onward will be explained according to the flowchart shown in FIG. In FIG. 3, step S10 and step S11 correspond to step S2 described above. First, in step S10,
The water temperature measured by the water temperature sensor 5 is transmitted to the control device 7.
Store in register TH within. In step S11, the water temperature measured by the water temperature sensor 6 is stored in the register TW. In the next step S12, the water temperature (TH)
It is determined whether the difference between the temperature and the water temperature (TW) is greater than or equal to a preset value (for example, 10°C). If this temperature difference is less than 10℃, you may not have used hot water at all.
Or it is decided that it has all been used up,
In this case, flag F is set in step S13. In the next step S20, the state of flag FC is checked. As described later, this flag FC is
It is set when the mode setter 8 is set to medium mode or low mode, and reset when it is set to high mode or off mode. i.e. the flag
The control of the present invention is performed when the flag FC is set, and the control of the present invention is not performed when the flag FC is reset.

First, the operation when the mode setter 8 is set to the off mode will be described. in this case,
A negative determination is made in step S20, and the process proceeds to step S42. Step S20 is a routine for determining whether or not the mode selected by the mode setting device 8 is the off mode. In this case, the determination is YES, and the step
Proceed to S43. In step S43, the heating target temperature register TS in the control device 7 is set to an extremely low temperature of, for example, 3°C. In addition, the mode setting device 8
If high mode is set in
Step S20 determines NO, step S42 determines NO, and step S45 determines whether the setting mode is high mode or not.
It is judged as YES. Then, in step S46, the maximum hot water temperature (for example, 85°C) is set in the heating target temperature register TS. After step S43 or step S46, the flag FC is reset in step S44, and the process proceeds to heating control from step S53 onwards. If the setting mode is high mode or off mode, step S53 and step S54 have no meaning, so their explanation will be omitted, and the explanation will be from step S55 onward. In step S55, the flag F is reset, and in the next step S56, it is determined whether the hot water temperature measured by the hot water temperature sensor 5 is higher or lower than the heating target temperature (TS) stored in the heating target temperature register TS. do. If the measured hot water temperature is lower than the heating target temperature (TS), the process proceeds to step S58, and the late-night power switch 11 is controlled to turn on the electric heater 4. Also, if the measured hot water temperature becomes higher than the heating target temperature (TS), step S57
Then, the late-night power switch 11 is controlled to turn off the electric heater 4. next step
At S59, the presence or absence of late-night power is checked again, and while there is late-night power, the process returns to step S56. Also, if the power runs out late at night, the process proceeds to step S60, where control is performed to turn off the electric heater 4. Due to the above,
When set to high mode, the hot water in the hot water tank 1 is set to the temperature measured by the hot water temperature sensor 5.
It will be heated to ℃. Furthermore, when the low mode is set, the water in the hot water tank 1 is heated to 3° C., but this essentially means that it is not heated at all. However, this means heating the water so that it does not drop below 3°C, which prevents the water from freezing.

Next, control according to the present invention when set to medium mode or low mode will be explained.
In this case, the determination in step S20 is YES, and the process proceeds to step S21. In step S21, it is determined whether the flag F is set.
As mentioned above, this flag F is set when the difference between hot water temperature (TH) and water temperature (TW) is abnormally small. This means that the necessary control data cannot be obtained, and therefore, in this case, control from step S22 to step S41 is not performed.

If flag F is reset, step
Proceeding to S22, it is determined whether the flag FL in the control device 7 is set. This flag FL is
As described later, this is set when the low mode is selected by the mode setter 8. First, the operation when the medium mode is selected by the mode setter 8 and the flag FL is reset will be described. In this case, the process proceeds to step S25, and the set value TLM of the lowest water temperature setting device 9 is stored in the calculation register TL in the control device 7. In the next step S26, the control amount (TUM) up to the previous day stored in the register TUM in the control device 7 is stored in the calculation register TU. In the next step S27, the hot water temperature (TH) stored in the register TH is subtracted from the minimum hot water temperature set value (TL) stored in the calculation register TL, and the difference ΔT is obtained. If △T is positive, it means that the water temperature in hot water tank 1 has dropped too much, and on the other hand, if △T is negative, it means that the water temperature in hot water tank 1 has been made too high. . The control amount (TU) is increased or decreased based on the value of ΔT, and control is performed so that ΔT becomes close to 0 on the next day. However, in order to avoid unstable operation due to sudden changes, the absolute value of △T is set to 1 in the next step S28.
℃, and in the next step S29 it is reduced to 1/2 of △T.
is added to the control amount (TU) and the value is stored in the calculation register TU again. If medium mode is set, the next step S30 as described above also
If NO is determined, the process proceeds to step S33. step
In S33, it is confirmed that the above control amount (TU) obtained by calculation is larger than the control amount (TUL) of the register TUL for low mode, and step S34
Set the above control amount (TU) to the register for medium mode.
Store in TUM. Note that this operation is not performed if the determination in step S33 is NO. In the next step S41, the water temperature (TW) in the register TW is
is stored in calculation register TY. Then, if the medium mode is selected, NO in step S42,
It is determined NO in step S45, YES in step S47, and the process advances to step S48. In step S48, the water temperature (TY) in the calculation register TY is subtracted from the control amount (TUM) in the register TUM, and the subtraction result is stored in the heating target temperature (TS) register TS. In the next step S49, the flag FL is reset, in the next step S50, the flag FC is set, and in the next step 53, it is confirmed that the heating target temperature (TS) determined as above is 85°C or less. death,
In the next step S55, flag F is reset. In addition, if the heating target temperature (TS) is 85℃ or higher,
In step S54, set the heating target temperature (TS) register TS.
Bring the contents to 85℃. By executing steps S56 to S59, the hot water in the hot water tank 1 is heated until the hot water temperature detected by the hot water temperature sensor 5 matches the heating target temperature (TS).

Next, the above control operation will be explained using specific numerical values. If the control amount TUM stored in the register TUM until the previous day is, for example, 80°C, and the hot water temperature (TH) measured in step S10 prior to the current heating control is, for example, 50°C, the minimum hot water temperature setting device 9 is set. Suppose the value was 65℃. In this case, the difference between the two △
T is 15°C, and half of the value obtained by subtracting 1°C from this value is 7°C. Therefore, the current control amount (TUM) found in step S29 is 87°C. and,
If the water temperature (TW) measured in step S11 is 10℃, the current heating target temperature (TS) is
The temperature will be 77℃.

As is clear from the above, the larger the above △T, the higher the heating target temperature (TS) is corrected, and the higher the water temperature (TW), the higher the heating target temperature (TS).
will be corrected to be lower. In this way, the heating target temperature (TS) is corrected daily based on the remaining hot water temperature and water temperature in the hot water tank 1, and heating control is optimized in response to slow changes in conditions such as the season and water temperature. It will be done.

Next, the operation when set to low mode will be explained. In the case of the low mode, the same control as in the above medium mode is performed based on the setting value TLL of the lowest water temperature setting device 10 for the low mode and the control amount (TUL) stored in the register TUL for the low mode. It is what is done. That is, step
In step S23, the set value TLL is stored in the calculation register TL, and in step S24, the previous day's control amount (TUL) is stored in the calculation register TU, and a new control amount (TU) is calculated based on these. (TU) is confirmed to be smaller than the control amount (TUM) for medium mode in step S31, and
It is stored again in the low mode register TUL.
Also, if step S47 is determined to be NO, step
The heating target temperature (TS) is obtained by subtracting the water temperature (TY) from the control amount (TUL) in S51, and the step
Flag FL is set in S52, and the process proceeds to steps S50 and thereafter.

In addition, at the initial stage of installing this late-night power water heater, appropriate initial values are set in the register TUM and the register TUL, respectively.

As explained in detail above, according to the control device for a late-night electric water heater according to the present invention, heating control is optimized in response to relatively slow changes in conditions such as season and water temperature, so that the hot water tank The temperature of the hot water in the interior is heated to a temperature that is necessary and sufficient for the usage conditions, but unlike conventional methods, it is heated to a higher temperature than necessary, resulting in large heat loss and reduced thermal efficiency. can be resolved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a late-night electric water heater according to the present invention, FIG. 2 is a general flowchart of a control program executed by a control device, and FIG.
The figure is a flowchart showing detailed contents of the above flowchart. 1... Hot water tank, 2... Water supply pipe, 3... Hot water supply pipe, 4... Electric heater, 5... Hot water temperature sensor, 6...
... Water temperature sensor, 7 ... Control device, 8 ... Mode setting device, 9, 10 ... Minimum hot water temperature setting device, 11 ... Late night power switch.

Claims (1)

[Claims] 1. It has temperature measurement means for measuring the water temperature in the upper part of the hot water tank and the water temperature in the lower part of the hot water tank, a setting means for setting the minimum water temperature, and a storage means for storing the heating target temperature, Prior to starting the heating control, a predetermined calculation is performed based on the difference between the set minimum water temperature and the measured water temperature, and the measured water temperature to determine the previous temperature that was stored. Late-night electric hot water, characterized in that the heating target temperature is corrected, the corrected heating target temperature is stored again, and heating control is performed so that the heating target temperature matches the measured hot water temperature. device control device.