JPH11182934A - Control method of heat insulating operation of hot-water supplier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool a thermistor and improve the durability of the thermistor by a method wherein heat insulating operation is not effected until a flow rate sensor detects the passing of water after deciding that there is no water in a boiler body through the thermistor while the heat insulating operation is started when the passing of water is detected. SOLUTION: A hot-water supplier 1 is provided with an inlet water temperature sensor 6 and a flow rate sensor 7, detecting the total passing amount of water, at the downstream side of the branched position of an inlet water pipe 3 from a bypass pipe 5 while a heat exchanger 2 is provided with a boiler body temperature sensor 8 consisting of thermistors. When an insulating operation switch is put ON, a high voltage is impressed on the boiler body temperature sensor 8 or the thermistor to generate self heat generation in the thermistor. The existence of water in the boiler body is decided at the temperature and when there is water, the heat insulating operation is started. When it is decided that there is no water, the operation is shifted into a waiting condition and after the flow rate sensor 7 has confirmed that the water passing signal is transmitted, the high voltage is impressed on the thermistor again to decide the existence of the water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the warming operation of a water heater which is not mechanically provided with a heat retaining function and which has a function of controlling and keeping the remaining water in the water heater hot. About.

[0002]

2. Description of the Related Art In a conventional hot water heater, for example, a hot water heater of a bypass mixing type, hot water discharged from a heat exchanger and low temperature water from a bypass passage are mixed to form a hot water at a set temperature. The hot water discharged from the heat exchanger is heated to a temperature higher than the set temperature by controlling the amount of combustion of the burner that heats the heat exchanger by feed-forward control with a capacity control valve, and bypassed. By controlling the amount of water passing through the passage by feedback control with a bypass valve, the mixing ratio of high-temperature hot water from the heat exchanger and low-temperature water from the bypass passage is adjusted, and hot water is supplied at a set temperature. There is known a water heater structurally provided with a heat retaining function so that hot water is supplied immediately after hot water supply is stopped and then restarted. However, such a heat retaining function (structure) is known.
There is known a water heater that does not include a water heater that performs a warming operation for heating residual water in the water heater. In the warming operation, generally controlled by a computer, it is confirmed that there is water in the water heater by using a thermistor, and then the burner is ignited to perform low output combustion to raise the temperature of the water in the water heater. In addition, the supply of cold water is prevented when hot water is supplied again, and hot water is supplied.

Here, detection of water by the thermistor is performed as follows. First, when used for normal hot water temperature detection, a low voltage (for example, 5 V) is applied to the thermistor, the voltage of the thermistor is measured, the resistance change of the thermistor is detected, and the temperature is detected. On the other hand, when detecting the presence or absence of water, a high voltage (for example, 15 V) is applied to the thermistor at the start of the water presence determination operation, and the rise of the thermistor voltage is measured to determine the presence or absence of water. In other words, when there is water in the water heater, the thermistor is cooled by water, so the thermistor is unlikely to be heated by self-heating, the resistance value is large because the temperature is low, the thermistor voltage is high, and when there is no water, Since the thermistor is not cooled because it is in the air, the thermistor is easily heated by self-heating, and the temperature is high, so that the resistance value is small and the thermistor voltage is low.

[0004]

However, in the conventional warming operation control of a water heater, as shown in a flowchart of FIG. 2, when an operation button is pressed (step A),
When a high voltage (for example, 15 V) is applied to the thermistor to cause self-heating (Step B), the presence or absence of water due to the level of the thermistor voltage due to the difference in temperature rise of the thermistor is determined (Step C). Starts the warming operation (Step D) and raises the water temperature in the can (Step E). When it is determined in Step C that there is no water, before pressing the operation button (before Step A) Therefore, when the operation button is turned on again, there is a problem that self-heating of the thermistor is performed again. That is, as described above, when the self-heating of the thermistor is repeated, the temperature of the thermistor itself becomes too high, so that the thermistor is deteriorated and the durability of the thermistor is reduced.

[0005] It is an object of the present invention to provide a method for controlling the operation of keeping a hot water heater warm, which can improve the durability of a thermistor for detecting the presence or absence of water.

[0006]

In order to achieve the above object, a method for controlling the temperature of a water heater according to the present invention comprises a flow rate sensor for detecting water flow and a thermistor for detecting the temperature of a can body. In a water heater with a warming operation function,
The presence or absence of water in the can body is determined by the thermistor, and after it is determined that there is no water, the heat insulation operation is not performed when the flow sensor detects water flow, and the heat insulation operation is started when water flow is detected. Thus, it is possible to cool the thermistor and improve the durability of the thermistor by energizing the thermistor after confirming that there is water by passing water.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a water heater to which the present invention is applied will be schematically described with reference to FIG. 3. A water heater 1 is connected to a heat exchanger 2 and an inlet side of the heat exchanger 2. Water inlet 3
And a tap water pipe T connected to the outlet side, a bypass pipe 5 for bypassing the heat exchanger 2, and a water inlet temperature Tc provided at a position downstream of the branch point of the bypass pipe 5 of the water inlet pipe 3. Inlet temperature sensor 6 comprising a thermistor and a flow sensor 7 for detecting the total water flow Q; a canister temperature sensor 8 provided in the heat exchanger 2 for detecting the canister temperature Th; A mixed tapping temperature sensor 10 for detecting a mixed tapping temperature Tm of the hot water from the heat exchanger 2 and the water from the bypass pipe 5 provided in the tapping pipe 4 on the downstream side of the branch position of A bypass valve 9, a burner 12 for heating the heat exchanger 2, and a gas pipe 1.
3 is provided with a proportional control valve 14 and a gas source plug 15 for adjusting the amount of gas to the burner 12, a blower 16, and a control unit 17 including a microcomputer and the like.

In the water heater 1, based on a preset set temperature Ts, an incoming water temperature Tc, a total water flow rate Q and a hot water distribution ratio (bypass ratio), the set temperature when mixed with water from the bypass pipe 5 is set. Mixed tapping temperature Tm equal to Ts
The can body setting temperature Ths at which the hot water is obtained is calculated, and the proportional control valve 14 is driven so that the can body temperature Th, which is the hot water temperature from the heat exchanger 2, becomes equal to the can body setting temperature Ths. While performing the forward (FF) control, the proportional control valve 1 is controlled so that the mixed tapping temperature Tm matches the set temperature Ts.
3 is subjected to feedback (FB) control.

Once the tapping is stopped, as long as the main power switch (not shown) is turned on, the operation shifts to the warming operation.
In the warming operation, when the can body temperature Th detected by the can body temperature sensor 8 falls below the warming combustion start temperature To, the warming combustion is started. After the warming combustion starts, the can body temperature Th rises and the warming combustion starts. If the temperature exceeds the warming stop temperature Te that is higher than the temperature To, the warming stop is stopped. The warming combustion start temperature To is changed in accordance with a change in the incoming water temperature Tc detected by the incoming water temperature sensor 6. When the incoming water temperature Tc is high, the warming interval from the stop of the warming combustion to the start of the next warming combustion is set. When the incoming water temperature Tc is high (for example, in summer), it is long, and when the incoming water temperature Tc is low (for example, in winter), it is short.

Here, the warm combustion start temperature To is calculated by the following equation from the set temperature Ts, the incoming water temperature Tc, and the coefficients a and b. To = Ts + α Note that α = a / Ts + b It is necessary to detect the presence / absence of water in the can body, that is, the heat exchanger 2 before starting the above-mentioned insulated combustion, in order to prevent dry burning. When a high voltage (for example, 15 V) is applied to the thermistor at the start of the work to determine the presence or absence of water, the rise in the voltage generated between both terminals of the thermistor is measured to determine the presence or absence of water.

The warming operation control will be described with reference to the flowchart of FIG. In step S1, when the push button of the heat retention operation switch is pressed, the operation of judging the presence or absence of water is started. In step S2, a high voltage (for example, 15 V) is applied to the thermistor, which is the can body temperature sensor 8, and the thermistor is self-determined. This produces an exotherm. In step S3, when the thermistor (can body temperature sensor 8) becomes high in temperature due to self-heating, the presence or absence of water in the can is determined at that temperature, and if it is determined that there is water, the warming operation is started (step S3).
4) Raise the temperature of the water in the can (Step S)
5).

If it is determined in step S3 that there is no water, the flow shifts to a standby state (step S6), and a flow signal (for example, a pulse generated by rotation of the rotor of the flow sensor 7) is transmitted from the flow sensor 7. After confirming this (step S7), the process proceeds to step S2, where a high voltage (15V) is applied again to the thermistor (can body temperature sensor 8) to cause self-heating of the thermistor (can body temperature sensor 8). Then, the presence or absence of water is determined (step 3). When a flow signal is transmitted from the flow rate sensor 7, it is determined that water has been supplied to the water heater 1 (heat exchanger 2), and the operation shifts to the above operation.

If the flow signal from the flow rate sensor 7 cannot be confirmed, the flow shifts to the standby state of step 6. In the standby state, even if the push button of the warming operation switch is pressed, the high voltage (15 V) is applied to the thermistor (can body temperature sensor 8).
V) is not applied.

When the thermistor self-heats in air,
Since the temperature of the thermistor becomes too high and damages the thermistor, this configuration makes it possible to cool the thermistor and to improve the durability of the thermistor by energizing the thermistor after confirming that there is water by passing water.

Referring to a different embodiment with reference to the flowchart of FIG. 3, the process shifts to a standby state (step S8), and it is confirmed that a flow signal has been transmitted from the flow rate sensor 7 (step S7). Then, the instruction of the warming operation is canceled (step S8), the fact that the instruction of the warming operation is canceled is displayed (step S9), and thereafter, the process returns to step S1 and the push button of the warming operation switch is pressed to operate. Restart the warm-up operation.

According to this configuration, when there is no water in the can body, the instruction of the warming operation is temporarily canceled, so that
Since it is impossible to restart the warming operation without stopping the combustion without pressing the push button of the warming operation switch after that, it is necessary to confirm that there is water in the can body before starting the warming combustion. In addition, it is possible to reliably prevent empty burning.

[0017]

Since the present invention is configured as described above, it has the following effects. If the thermistor self-heats in the air, it will become too hot and damage it. Can be done.

[Brief description of the drawings]

FIG. 1 is a hot water supply performance curve diagram according to an embodiment of the present invention.

FIG. 2 is a hot water supply performance curve diagram according to another embodiment of the present invention.

FIG. 3 is a flowchart showing a conventional heat retaining operation.

FIG. 4 is a schematic configuration diagram showing an example of a water heater to which the present invention is applied.

[Explanation of symbols]

1 water heater, 2 heat exchanger, 3 water supply pipe, 4 tap water pipe,
Reference Signs List 5 bypass pipe 6 inlet water temperature sensor, 7 flow rate sensor, 8 can body temperature sensor 9 bypass valve, 11 mixed hot water temperature sensor, 17 control unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Manabu Shimizu 93, Edo-cho, Chuo-ku, Kobe-shi, Hyogo Pref.

Claims (1)

[Claims] 1. A water heater having a flow rate sensor for detecting water flow and a thermistor for detecting a temperature of a can body and having a control operation having a warming operation function, wherein the presence or absence of water in the can body is determined by the thermistor. And after judging that there is no water, does not perform the warming operation when the flow sensor detects the passage of water, and starts the warming operation when the passage of water is detected. .