JPH0674562A - Control method for hot water supply device - Google Patents

Abstract

PURPOSE:To securely prevent the low temperature corrosion from being caused by setting a minimum hot water temperature required to prevent the low temperature corrosion as a reference temperature and feed forward-controlling a mixing water control valve in such a way that the temperature conforms with a distribution factor related to the reference temperature or the like. CONSTITUTION:Water in a water inlet line 10 is heated with a spontaneous heat exchanger 20 so that hot water is output to a hot water outlet line 30 while the water is mixed with a bypass line 40, thereby controlling the hot water to a specified temperature to supply the hot water. In this case, a controller 60 controls a burner 21 of the spontaneous heat exchanger 20 and a hot water control valve 41 of the bypass line 40 respectively based on each detection signal transmitted from an inlet temperature sensor 11, an inlet water flow rate sensor 12, an outlet hot water temperature sensor 31 and a hot water supply temperature sensor 51. More specifically, a minimum output hot water temperature, which is required to avoid low temperature corrosion of the spontaneous heat exchanger 20 is set. The mixing water control valve 41 is feed forward-controlled based on a setting supply hot water temperature which is lower than the reference temperature and a low fixed temperature which exceeds the reference temperature and a distribution factor of the inlet water temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is designed so that hot water discharged through a heat exchanger is mixed with water as needed using a bypass, and hot water is supplied at a predetermined hot water temperature. 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 the hot water passing through the instant heat exchanger is raised, and a bypass is separately provided to mix water, thereby adjusting the hot water temperature to a predetermined level. What you have done is provided. For example, in Japanese Unexamined Patent Publication No. 2-183759, when the set hot water supply temperature is equal to or higher than a certain temperature, the water mixing adjustment valve is closed, and the hot water discharge temperature from the heat exchanger is feedback-controlled to the set hot water supply temperature to obtain a constant temperature. In the case of less than, there is provided a water heater control method in which water is mixed from the heat exchanger to the hot water by the water mixing adjusting valve, and the final hot water temperature is feedback-controlled to the set hot water temperature.

[0003]

SUMMARY OF THE INVENTION In the above cases,
From the viewpoint of low temperature corrosion prevention and boiling prevention, it is conventionally preferable that the tapping temperature of the instantaneous heat exchanger is in the range of, for example, 50 to 80 ° C, but conversely in the range of 50 to 80 ° C. If so, there is no control method that further regulates the condition of the hot water discharge temperature by the instantaneous water heater. However, when considering hot water supply performance during re-hot water supply, even if the final hot water supply temperature can be adjusted to the set hot water temperature by mixing water, the hot water output temperature from the instantaneous hot water supply device is When the temperature is high, the difference from the environment (atmosphere) temperature is large, so that there is a drawback that the heat radiation is large when the hot water supply is stopped and the hot water supply temperature is significantly lowered at the initial stage of hot water re-supply. Especially when the water inlet temperature is low, there is a tendency to set the hot water outlet temperature of the instantaneous hot water heater to be high, so that the hot water supply temperature lowers more drastically in the initial stage of re-hot water supply.

Therefore, the present invention solves the above-mentioned drawbacks of the prior art, avoids the occurrence of low temperature corrosion of the heat exchanger in a mixed water type water heater, and significantly lowers the hot water temperature at the initial stage of re-hot water supply. It is an object of the present invention to provide a method for controlling a water heater that can prevent the above.

[0005]

In order to achieve the above object, the method of the present invention heats water from an inlet channel with an instantaneous heat exchanger to discharge the hot water to the outlet channel, and also discharges the bypass from the inlet channel. A method of controlling a water heater, which is connected to a passage so that water can be mixed and hot water is supplied by adjusting to a predetermined set hot water temperature T _QS , which avoids low temperature corrosion of the instantaneous heat exchanger. Is set as a reference temperature T _S in advance, and for a set hot water supply temperature T _QS that is lower than the reference temperature T _S , the set hot water temperature T _KS of the instantaneous heat exchanger is set in advance as a reference. The feed rate of the burner is automatically set to a fixed temperature T _F which is lower than the temperature, and the distribution rate K of the bypass water mixing control valve is calculated from the set hot water supply temperature T _QS , the fixed temperature T _F and the incoming water temperature T _{C. BK} is calculated and mixed so as to obtain 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 characteristic, the method of the present invention closes the bypass water mixing adjusting valve and sets the hot water outlet temperature of the instantaneous heat exchanger for the set hot water supply temperature T _QS which is equal to or higher than the reference temperature T _S. The second feature is that the burner is feedforward-controlled with T _KS being the set hot water supply temperature T _QS .

[0006]

According to the first feature of the present invention, the reference temperature T
_The minimum hot water temperature required to avoid low temperature corrosion of the instantaneous heat exchanger is adopted as _S , and the set hot water temperature T _QS is the reference temperature T _S.
In case of less than, set outlet temperature T _KS by the instantaneous heat exchanger
A predetermined fixed temperature T _F is automatically set. Since the fixed temperature T _F is equal to or higher than the reference temperature T _S , first, low temperature corrosion of the instantaneous heat exchanger can be prevented. Since the fixed temperature T _F is a temperature lower than the reference temperature T _{S, the} degree of temperature decrease due to heat radiation of residual hot water in the instantaneous heat exchanger and hot water passage after the hot water supply is stopped is small. Therefore, since the temperature gap between the original hot water and the original hot water is small, the degree of decrease in the hot water supply temperature after mixing water is small. Therefore, no significant operation of the mixed water regulating valve for correcting the hot water supply temperature is required at the initial stage of hot water reflow. If the original hot water temperature is high and the residual hot water temperature drops significantly due to heat radiation, the hot water supply temperature will also drop significantly when mixed at the same ratio, and the mixed water control valve to correct it Also becomes noticeable. The distribution rate K _BK of the mixed water regulating valve of the bypass is set to the set hot water temperature T _QS and the set hot water temperature T _KS which is the fixed temperature T _F and the incoming water temperature T _C.
Is calculated from and feed-forward controlled. Further, 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 mixed water adjusting valve is closed and the set hot water temperature T _KS of the instantaneous heat exchanger is set. The burner is feedforward controlled with the hot water supply temperature T _QS . Even in this case, the hot water outlet temperature of the heat exchanger is not made higher than necessary, so that the temperature drop due to heat radiation after the hot water supply is stopped is suppressed as such. In addition, as long as the water mixing control valve starts from the closed state during re-hot water supply, the degree of decrease in the hot water supply temperature at the initial stage of re-hot water supply can be small.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram of a water heater in which the method of the present invention is implemented, and FIG. 2 is a flow chart showing a control example.

In the water heater shown in FIG. 1, the water supplied through the water inlet 10 is heated by the instantaneous heat exchanger 20 and discharged into the hot water outlet 30. Bypass 40 from the water inlet 10 is a hot water outlet 30
It is connected to and is designed to mix water. An inlet temperature sensor 11 and an inlet flow rate sensor 12 are provided in the inlet passage 10. Further, the instant heat exchanger 20 has a gas burner 31
Is provided. In addition, an instant heat exchanger is provided in the exit passage 30.
A hot water outlet temperature sensor 31 is provided from the hot water outlet 20.
Further, a hot water supply temperature sensor 51 is provided in the hot water supply passage 50 downstream of the point 32 of the hot water discharge passage 30 to which the bypass 40 is connected, and the bypass 40 is provided with a water mixture adjusting valve 41 and a drive unit 42 thereof. 60 is a controller with a built-in microcomputer for controlling the entire water heater, which inputs information from each sensor 11, 12, 31, 51 and a command from a remote controller (not shown), performs a calculation according to a predetermined program, and outputs it to each unit 21, 41. The control signal of is output.

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

When S2 is NO (when the set hot water supply temperature T _QS is _lower than the reference temperature T _S ), the controller 60 presets the set hot water temperature T _KS to be hot water discharged from the instantaneous heat exchanger 20. The fixed temperature T _F is automatically set, and the fixed temperature T _F
The burner 21 is feed-forward controlled by calculating the combustion heat quantity so as to attain _F (S3). Regarding the fixed temperature T _F , a temperature that is equal to or higher than the reference temperature T _S and is low is determined by a preliminary experiment and is set as the fixed temperature. In this embodiment, it is set to, for example, 50 ° C., which is the same as the reference temperature T _S.

Then, together with the feedforward control of the burner 21, the distribution rate K _BK by the water mixing adjusting valve 41 is calculated,
Feed-forward control is performed on the water mixing control valve 41 so that the obtained distribution rate K _BK is obtained (S4). The distribution rate K _BK is the set hot water supply temperature T _QS and the set hot water temperature T _KS of the instantaneous heat exchanger 20.
Is calculated from the fixed temperature T _F and the incoming water temperature T _C. now,
Let Q _{B be} the amount of water to the bypass 40 side and Q _K be the amount of water to the heat exchanger 20 side by the distribution ratio K _BK of the water mixing control valve 41. Then,
The following equations 1 and 2 are established.

[0012]

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

From the above Equations 1 and 2, the distribution rate K _BK of the mixed water regulating valve 41 can be obtained by the following Equation 3.

[0015]

[Formula 3] K _BK = (T _F −T _QS ) / (T _QS −T _C ) K _BK ： Distribution rate of mixed water regulating valve to be calculated _TF ： Fixed temperature T _QS ： Set hot water temperature T _C ： 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 supply temperature T _KS of the instantaneous heat exchanger 20 is the minimum required 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 solved. Moreover, the instant heat exchanger
Since the set hot water discharge temperature T _KS of 20 is fixed to a low temperature equal to or higher than the reference temperature T _S (fixed temperature T _F ), a remarkable temperature decrease due to heat radiation of the residual hot water when the hot water supply is stopped is suppressed, and therefore, is performed thereafter. It is possible to reduce the decrease in hot water supply temperature at the beginning of re-hot water supply.

If YES in S2 (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 set hot water supply temperature T _KS of the instantaneous heat exchanger 20 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 adjusting 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 discharged 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 The temperature of the hot water discharged from the hot water supply does not become higher than necessary, and therefore the degree of decrease in the temperature of the residual hot water when the hot water supply is stopped is reduced to that extent.

[0018]

According to the method of controlling a water heater according to the present invention, the present invention has the above-described structure and operation, and the minimum hot water temperature required to avoid low temperature corrosion of the instantaneous heat exchanger is the reference temperature. For a set hot water supply temperature T _QS that is preset as T _S and is lower than the reference temperature T _S , a fixed hot water temperature T _KS that is equal to or higher than the predetermined reference temperature is set for the hot water supply temperature T _KS of the instantaneous heat exchanger.
_The burner is feed-forward controlled by automatically setting to _F, and the distribution rate K _BK of the mixed water adjusting valve of the bypass is calculated from the set hot water supply temperature T _QS , the fixed temperature T _F, and the incoming water temperature T _C , and Since the feed-forward control of the mixed water regulating valve is performed so that the distribution rate becomes K _BK , even if the set hot water supply temperature T _QS is lower than the reference temperature T _{S, the} set hot water temperature T _KS set by the instantaneous heat exchanger is the reference temperature. It can be set to T _S or more, and low temperature corrosion of the instant heat exchanger can be prevented. Moreover, since the set hot water temperature T _KS set by the instantaneous heat exchanger is fixed to a low temperature which is equal to or higher than the reference temperature T _S , the residual hot water remaining in the instantaneous heat exchanger and the hot water passage after the hot water supply is stopped. It is possible to reduce the decrease in the temperature of the hot water supply, and thus to reduce the decrease in the hot water supply temperature at the initial stage of hot water re-flowing and to improve the hot water supply characteristics. Therefore, it is also possible to prevent a short-term significant movement of the water mixing adjustment valve for temperature adjustment in the initial stage of re-hot water supply, and to provide stable hot water supply with less temperature fluctuations by using a water mixing adjustment valve that does not require sudden movement. Obtainable. According to the hot water heater control method of the second aspect, in addition to the effect of the configuration of the first aspect, for the set hot water temperature T _QS equal to or higher than the reference temperature T _S , the bypass water mixture adjustment is performed. Since the valve is closed and the set hot water temperature T _KS of the instantaneous heat exchanger is set as the set hot water supply temperature T _QS , the burner is feed-forward controlled, so that the set hot water supply temperature T _{QS is} set.
Is higher than the reference temperature T _S , by adjusting the set hot water supply temperature directly from the instantaneous heat exchanger 20 without mixing water, the hot water discharge temperature by the heat exchanger becomes higher than necessary. Therefore, the temperature drop due to heat dissipation when hot water supply is stopped is suppressed to some extent, and the decrease in hot water supply temperature during re-hot water supply can be reduced.

[Brief description of drawings]

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

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 mixture adjusting valve 42 Drive section 50 Hot water channel 51 Hot water temperature sensor 60 Controller

Claims (2)

[Claims] 1. A predetermined setting, wherein water from an inlet is heated by an instantaneous heat exchanger to be discharged to a hot water outlet, and a bypass from the inlet is connected to the hot water outlet so that water can be mixed. A hot water supply control method for hot water supply by adjusting to a hot water supply temperature T _QS , wherein a minimum hot water 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 hot water discharge temperature T _KS of the instantaneous heat exchanger is automatically set to a low fixed temperature T _F which is equal to or higher 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 Characterized by performing feedforward control of the regulating valve Method of controlling a water heater. 2. With respect to the set hot water supply temperature T _QS which is 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 feedforward controlled.