JP3070293B2 - Water heater control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In the present invention, hot water supplied through a heat exchanger is mixed with water as required by using a bypass, and is adjusted to a predetermined hot water supply temperature to supply hot water. The present invention relates to a method for controlling a water heater.

[0002]

2. Description of the Related Art In order to prevent low-temperature corrosion, in recent hot water heaters, the temperature of tap water passing through an instantaneous heat exchanger is increased, and a separate bypass is provided to mix water, thereby adjusting the temperature to a predetermined hot water supply temperature. What you do is provided. For example, in Japanese Patent Application Laid-Open No. 2-183759, when the set hot water supply temperature is equal to or higher than a certain temperature, the mixed water adjustment valve is closed, and the outlet temperature from the heat exchanger is feedback-controlled to the set hot water supply temperature, and the constant temperature is controlled. In the case where the temperature is less than the predetermined value, a water mixing control valve mixes the hot water from the heat exchanger with the hot water and provides a feedback control of the final hot water supply temperature to the set hot water supply temperature.

[0003]

In the above case,
Conventionally, the tapping temperature of the instantaneous heat exchanger is preferably in the range of, for example, 50 to 80 ° C from the viewpoint of low-temperature corrosion prevention and boiling prevention, but conversely, in the range of 50 to 80 ° C. If so, no control method has been adopted that further regulates the condition of tapping temperature by the instantaneous water heater. However, when considering the hot water supply performance at the time of re-hot water supply, even if the final hot water supply temperature can be adjusted to the set hot water supply temperature by mixing water, even if the hot water supply temperature from the instantaneous hot water supply is When the temperature is high, there is a large difference between the temperature and the environment (atmosphere), so that the heat radiation when the hot water supply is stopped is large, and there is a disadvantage that the hot water temperature drops remarkably in the initial stage of re-hot water supply. Particularly when the incoming water temperature is low, the outlet water temperature of the instantaneous water heater tends to be set high, so that the hot water supply temperature in the initial stage of re-hot water supply becomes more severe.

Accordingly, the present invention solves the above-mentioned drawbacks of the prior art, and in a mixed water heater, it is possible to avoid the occurrence of low-temperature corrosion of the heat exchanger, and furthermore, a remarkable decrease in the temperature of the hot water at the initial stage of reheating. It is an object of the present invention to provide a method of controlling a water heater that can prevent the occurrence of water heaters.

[0005]

In order to achieve the above object, a method of the present invention is to heat water from an inlet channel with an instantaneous heat exchanger to supply hot water to a hot water channel, and to bypass a bypass from the water inlet channel. A method for controlling a water heater that is connected to a road so that water can be mixed, and is adjusted to a predetermined set hot water supply temperature T _QS to supply hot water, wherein low temperature corrosion of the instantaneous heat exchanger is avoided. preset as the minimum hot water temperature of the reference temperature T _S required, the reference temperature T for the _S less than set hot water supply temperature T _QS, predetermined said reference set hot water temperature T _KS of the instant heat exchanger with automatically set to a temperature above a lower setting temperature T _F feedforward control burner, set hot water supply temperature T _QS and the fixed temperature T _F with the incoming water temperature T _C distribution ratio of mixing water regulating valve of the bypass and a K by calculating the _BK, mixed so as to be the distribution ratio K _BK The first feature is that feedforward control of the water regulating valve is performed. Further, in addition to the first feature, the method of the present invention closes the bypass water mixing adjustment valve and sets the tap water temperature of the instantaneous heat exchanger for the set hot water supply temperature T _QS that is equal to or higher than the reference temperature T _S. The second feature is that _TKS is set as the set hot water supply temperature _TQS and the burner is feedforward controlled.

[0006]

According to the first feature of the present invention, the reference temperature T
_The minimum tapping temperature required to avoid low-temperature corrosion of the instantaneous heat exchanger is adopted as _S , and the set hot water supply temperature _TQS is equal to the reference temperature Ts.
If the temperature is less than the set temperature T _KS set by the instantaneous heat exchanger
The fixed temperature T _F is automatically set. Since the fixed temperature T _F is equal to or higher than the reference temperature T _S, it is possible to prevent the instantaneous heat exchanger against low-temperature corrosion. And since the fixed temperature T _F is the reference temperature T _S above low temperature, less temperature drop degree by heat radiation of the pouring water remaining in the instant heat exchanger and hot water passage after providing hot water supply is stopped. Therefore, in the initial stage of hot water re-discharge, since the temperature gap with the original hot water is small, the degree of drop in hot water supply temperature after mixing water can be reduced. Therefore, a remarkable operation of the mixed water regulating valve for the correction of the hot water supply temperature in the initial stage of re-water supply is not required. If the original tap water temperature is high and the temperature of the remaining tap water drops significantly due to heat dissipation, the drop in the hot water supply temperature when the water is mixed at the same ratio naturally becomes remarkable. Movement becomes remarkable. The distribution ratio K _BK of the bypass water mixing regulating valve is determined by the set hot water supply temperature T _QS , the set tap water temperature T _KS which is the fixed temperature T _F , and the incoming water temperature T _C.
And feedforward control is performed. According to the second feature of the present invention, when the set hot water supply temperature T _QS is equal to or higher than the reference temperature T _S , the bypass water mixing regulating valve is closed, and the set hot water temperature T _KS of the instantaneous heat exchanger is set. The hot water supply temperature _TQS is set, and the burner is feedforward controlled. In this case as well, the tapping temperature of the heat exchanger is not set higher than necessary, so that the temperature drop due to heat radiation after stopping hot water supply is suppressed to some extent. Further, as long as the water mixing adjustment valve starts from the closed state at the time of re-hot water supply, the degree of drop in hot water supply temperature in the initial stage of re-hot water supply may be small.

[0007]

FIG. 1 is an overall configuration diagram of a water heater in which a method of the present invention is carried out, and FIG. 2 is a flowchart showing a control example.

In the water heater shown in FIG. 1, the water supplied to the water inlet 10 is heated by the instantaneous heat exchanger 20 and discharged to the hot water outlet 30. From the water inlet channel 10, a bypass 40 is connected to the hot water channel 30.
And are adapted to mix water. The inlet channel 10 is provided with an inlet temperature sensor 11 and an inlet flow sensor 12. In addition, the instantaneous heat exchanger 20 has a gas burner 31.
Is provided. In addition, an instantaneous heat exchanger
A tapping temperature sensor 31 for tapping hot water from tapping 20 is provided,
Further, a hot water supply temperature sensor 51 is provided in a hot water supply path 50 of the hot water supply path 30 downstream of a point 32 to which the bypass 40 is connected, and the bypass 40 is provided with a mixed water regulating valve 41 and a drive unit 42 thereof. Reference numeral 60 denotes a controller with a built-in microcomputer for controlling the entire water heater, which inputs information from the sensors 11, 12, 31, and 51 and a command from a remote controller (not shown), performs calculations in accordance with a predetermined program, and performs operations to the respective parts 21 and 41. Output a control signal.

Next, a method of controlling the water heater by the controller 60 will be described with reference to FIG. now,
When a hot water supply curl (not shown) is opened in the water heater and hot water supply (including re-hot water supply) is started (YES in S1), controller 60 first sets set hot water supply temperature T _QS to reference temperature T _S.
It is determined whether or not this is the case (S2). The reference temperature T _S is a value in consideration of low-temperature corrosion of the instantaneous heat exchanger 20, and a minimum tapping temperature necessary to avoid low-temperature corrosion is determined by a preliminary experiment, and is used as a reference temperature. For example, 50 ° C. can be selected as the reference temperature T _S.

When the answer is NO in S2 (when the set hot water supply temperature T _QS is _lower than the reference temperature T _S ), the controller 60 determines a set hot water temperature T _KS to be discharged from the instantaneous heat exchanger 20 in advance. The fixed temperature T _F is automatically set to the fixed temperature T _F
The burner 21 is feed-forward controlled by calculating the amount of combustion heat so as to be _F (S3). Regarding the fixed temperature T _F , a temperature that is higher than or equal to the reference temperature T _S and lower than the reference temperature T _S is determined by a preliminary experiment and is set as the fixed temperature. In this embodiment to match with the reference temperature T _S, eg, 50 ° C..

[0011] Then with the feedforward control of the burner 21, it calculates the distribution ratio K _BK by mixing water adjustment valve 41,
The resulting feedforward control mixing water adjustment valve 41 so that the distribution rate K _BK (S4). The distribution ratio K _BK is determined by the set hot water supply temperature T _QS and the set hot water temperature T _KS of the instantaneous heat exchanger 20.
Computed from the fixed temperature T _F with the incoming water temperature T _C is. now,
The amount of water to the bypass 40 due to the distribution ratio K _BK of the water mixing regulating valve 41 is Q _B , and the amount of water to the heat exchanger 20 is Q _K Then
The following equations 1 and 2 hold.

[0012]

[ _Equation 1] T _QS (Q _B + Q _K ) = T _C · Q _B + T _F · Q _K T _QS : Set hot water supply temperature T _C : Inlet water temperature T _F : Fixed temperature Q _B : Bypass 40 with distribution ratio K _BK Amount of water to the side Q _K : Amount of water to the heat exchanger 20 at the distribution ratio K _BK

[0013]

[Number 2] _{K BK = Q B / Q K} K BK: distribution ratio Q _B of the mixing water regulating valve to be computed: water Q _K to the bypass 40 side in the distribution ratio K _BK: in the distribution ratio K _BK Water flow to heat exchanger 20

From the above equations (1) and (2), the distribution ratio K _BK of the mixed water regulating valve 41 is obtained by the following equation (3).

[0015]

Equation 3] _{K BK = (T F -T QS} ) / (T QS -T C) K BK: distribution ratio T _F of mixing water regulating valve to be computed: the fixed temperature T _QS: set hot water supply temperature T _C: Inlet water temperature

As described above, even when the set hot water supply temperature T _QS is relatively low (lower than the reference temperature T _S ), the set hot water temperature T _KS of the instantaneous heat exchanger 20 is the minimum necessary to avoid low-temperature corrosion. Since the temperature is higher than the tapping temperature (reference temperature T _S ), the problem of low-temperature corrosion is eliminated. And instantaneous heat exchanger
Since the 20 set tapping temperatures T _KS are fixed at a temperature lower than the reference temperature T _S (fixed temperature T _F ), a significant temperature drop due to the radiation of the remaining tapping water when the hot water supply is stopped is also suppressed, and thereafter, it is performed. Thus, it is possible to reduce the drop in hot water supply temperature at the beginning of reheating.

If the determination in S2 is YES (when the set hot water supply temperature T _QS is equal to or higher than the reference temperature T _S ), the controller 60 automatically sets the instantaneous heat exchanger 20 set hot water supply temperature T _KS to the set hot water supply temperature T _QS . The burner 21 is feed-forward controlled by calculating the required combustion amount (S5). At the same time, the water mixing adjustment valve 41 is closed (S6). When the set hot water supply temperature T _QS is equal to or higher than the reference temperature T _S , the hot water itself from the instantaneous heat exchanger 20 is directly adjusted to the set hot water supply temperature without mixing water, so that the instantaneous heat exchanger 20 Is no longer unnecessarily high, and therefore the degree of temperature drop of the remaining tap water when the hot water supply is stopped is also reduced accordingly.

[0018]

According to the water heater control method according to the first aspect of the present invention, the minimum tapping temperature required to avoid low-temperature corrosion of the instantaneous heat exchanger is determined by the reference temperature. preset as T _S, the reference temperature T for the _S less than set hot water supply temperature T _QS, the setting of the instant heat exchanger hot water temperature T _KS a predetermined said reference temperature or more lower fixed temperature T
Automatically set to _F as well as feed-forward control of the burner, by calculating the distribution ratio K _BK of mixing water regulating valve of the bypass from the set hot water supply temperature T _QS wherein the fixed temperature T _F with the incoming water temperature T _C, the since to perform feedforward control of the mixing water regulating valve so that the distribution ratio K _BK, set the hot water temperature T _KS by even momentary heat exchanger in the case of less than the set hot water supply temperature T _QS is the reference temperature T _S is the reference temperature T _S or more, and low-temperature corrosion of the instantaneous heat exchanger can be prevented. Moreover, since the tapping temperature T _KS set by the instantaneous heat exchanger is higher than the reference temperature T _S but is fixed to a low temperature, the tap water remaining in the instantaneous heat exchanger and the tap water after the supply of hot water is stopped. Can be reduced, so that the drop in the hot water supply temperature in the initial stage of re-water supply can be reduced, and the re-water supply characteristics can be improved. Therefore, it is also possible to prevent a short-term remarkable movement of the water mixing regulating valve for temperature adjustment at the initial stage of re-water supply, and to provide a stable hot water supply with little temperature fluctuation by using a water mixing regulating valve which does not require rapid movement. Obtainable. According to the control method of the water heater according to claim 2, in addition to the effects by the configuration recited in claim 1, for the reference temperature T _S above setting the hot water temperature T _QS, mixing water adjustment bypass Since the valve is closed and the burner is feed-forward controlled with the set tap temperature T _KS of the instantaneous heat exchanger as the set hot water supply temperature T _QS , the set hot water supply temperature T _QS
When the temperature is equal to or higher than the reference temperature T _S , by directly adjusting the hot water supply temperature by the hot water from the instantaneous heat exchanger 20 without mixing the water, the hot water temperature by the heat exchanger is raised to an unnecessarily high temperature. Therefore, a decrease in temperature due to heat radiation when the hot water supply is stopped is suppressed to a certain extent, and a decrease in hot water supply temperature during re-hot water supply can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a water heater in which a method of the present invention is performed.

FIG. 2 is a flowchart showing a control example of the method of the present invention.

[Explanation of symbols]

 10 Inlet channel 11 Inlet temperature sensor 20 Instantaneous heat exchanger 21 Burner 30 Outlet channel 31 Outlet temperature sensor 40 Bypass 41 Water mixing regulating valve 42 Drive unit 50 Hot water channel 51 Hot water temperature sensor 60 Controller

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-311039 (JP, A) JP-A-3-191254 (JP, A) JP-A-6-288632 (JP, A) JP-A-2- 183759 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F24H 1/10 302

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the water from the water inlet is heated by an instantaneous heat exchanger to supply the hot water to the hot water outlet, and a bypass from the water inlet is connected to the hot water outlet so that the water can be mixed. A method for controlling a water heater that performs hot water supply by adjusting to a hot water supply temperature T _QS , wherein a minimum tapping temperature required to avoid low-temperature corrosion of the instantaneous heat exchanger is preset as a reference temperature T _S , For the set hot water supply temperature T _QS lower than the reference temperature T _S , the set tap temperature T _KS of the instantaneous heat exchanger is automatically set to a fixed temperature _TF lower than the predetermined reference temperature and the burner is fed. as well as forward control, and calculates the distribution ratio K _BK of mixing water regulating valve of the bypass from the set hot water supply temperature T _QS wherein the fixed temperature T _F with the incoming water temperature T _C, so that the said distribution ratio K _BK water mixture The feedforward control of the regulating valve is performed. Method of controlling a water heater. 2. For a set hot water supply temperature T _QS equal to or higher than the reference temperature T _S , the bypass water mixing adjustment valve is closed, and the set hot water supply temperature T _KS of the instantaneous heat exchanger is set as the set hot water supply temperature T _QS . The method for controlling a water heater according to claim 1, wherein the burner is feed-forward controlled.