JPH03260551A - Controlling device for water heater - Google Patents

Abstract

PURPOSE:To eliminate a change in the quantity of heating with a change in a flow rate and to obtain a stable temperature of hot water from a reduced change in an outflow temperature, by reducing the flow rate when the outflow temperature detected is lower than a set temperature and by increasing the flow rate when the outflow temperature is higher than the set temperature. CONSTITUTION:A feed forward control amount (FF control amount) QFF is taken as a combustion amount Q for an initial control, and a blower 12 is controlled in accordance with the combustion amount Q in a combustion control element 42, while a control of a governor proportional valve 28 is executed therein by detecting the number of revolutions of the blower. A water quantity control device 19 is held in the degree of opening made in the preceding employment, and the water in a flow rate determined in accordance with the degree of opening of a hot water tap 20 and the pressure of a water supply source such as waterworks passes through a heat exchanger 16. Thereafter, the combustion amount Q is determined by adding a feedback control amount (FB control amount) QFB including a temperature detected by a hot water temperature thermistor 21, and it is discriminated whether a hot water temperature Tout detected by the hot water temperature thermistor 21 reaches a set temperature Tset or not. In the case when the combustion amount Q does not yet reach a characteristic combustion amount Qp, a heating capacity has a residual margin, and therefore an operation of increasing the flow rate is conducted for supplying as much hot water as possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention automatically adjusts the flow rate of water passing through a heat exchanger using a water flow control device to supply as much hot water as possible according to a set temperature. The present invention relates to a control device for a water heater that controls the operation of the water heater.

[Conventional technology] In water heaters, the maximum heating capacity of gas burners, etc. for heating water passing through a heat exchanger is limited, so a geared motor is used to drive the valve body in the water circuit that includes the heat exchanger. The heat exchanger is equipped with a water flow control device that regulates the flow rate, and limits the flow rate of water passing through the heat exchanger so that the temperature of the outflowing water reaches a set temperature.

In this case, in addition to simply restricting the flow rate, in order to obtain as much flow rate as possible for the set temperature, it is necessary to adjust the set temperature and the temperature of water entering the heat exchanger to match the maximum heating capacity of the gas burner, etc. Calculate the maximum hot water supply amount,
Some systems control water flow control devices so that the maximum amount of hot water can be supplied.

At this time, the water flow control device is controlled based on the temperature of the hot water flowing out from the heat exchanger (outlet water temperature), and if the outlet temperature does not reach the set temperature, a flow reduction operation is performed to reduce the flow I. If the outlet temperature has reached the set temperature and there is surplus power in the burner, etc., the flow rate increase operation is performed.

[Problem to be solved by the invention] However, when heating is performed near the maximum heating capacity of a burner, etc., the outlet temperature reaches the set temperature.
Furthermore, if an operation to increase the flow rate is performed, there will always be a shortage of heating power, so the outlet temperature will not reach the set temperature, and an operation to decrease the flow rate will be performed.

In this way, when heating is performed near the maximum heating capacity of a burner, etc., if an operation to increase the flow rate is performed, the operation to decrease the flow rate is always required due to insufficient heating capacity. Since the amount of heating is controlled at the same time,
There is a problem in that the temperature of the tapped hot water becomes unstable, and hunting occurs in which the water flow rate control device repeatedly increases and decreases the flow rate, and as a result, the temperature of the tapped hot water becomes unstable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a water heater in which the flow rate is adjusted by a water flow control device, which can provide a stable hot water temperature and supply as much hot water as possible for a set temperature.

[! II! Means for Solving the Problem] The present invention provides a temperature setting means for setting the temperature of hot water flowing out from a water circuit including a heat exchanger heated by a heating means, and an outflow temperature for detecting the temperature of hot water flowing out from the water circuit. a detection means, a flow rate detection means for detecting the flow rate of water passing through the water circuit, and heating I of the heating means based on the temperature difference between the set temperature of the temperature setting means and the detected temperature of the outflow temperature detection means. In a water heater control device that controls a flow rate adjusting means that controls a flow rate passing through the water circuit based on the temperature difference, the heating amount is specified to be a predetermined amount smaller than the maximum heating amount of the heating means. The technical means is to perform a flow rate increasing operation by the flow rate adjusting means only when the heating amount of the heating means is smaller than the specific heating amount.

[Function] In the present invention, the temperature of the hot water flowing out from the water circuit including the heat exchanger is detected by the outflow temperature detection means, and the heating amount of the heating means is controlled based on the temperature difference from the set temperature.

Further, the flow rate of the water circuit is adjusted by the flow rate adjustment means based on the temperature difference, and when the outflow temperature detected by the outflow temperature detection means is lower than the set temperature, the flow rate is reduced and the outflow temperature is set to the set temperature. If higher, the flow rate is increased.

This operation of increasing the flow rate is performed only when the heating amount of the heating means is smaller than the specific heating amount, and only the operation of decreasing the flow rate is performed when the heating amount of the heating means is larger than the specific heating amount.

[Effect of the invention] In the present invention, when the flow rate is adjusted based on the outflow temperature and the heating amount of the heating means is controlled according to the flow rate, if the heating amount of the heating means exceeds the specific heating amount. The flow rate will not increase any further.

Therefore, if the heating amount for the flow rate is insufficient for the set temperature, and the flow rate is once reduced and the outflow temperature becomes higher than the set temperature, if the heating amount exceeds the specific heating amount, Since only the flow rate reduction operation is performed, hunting of the flow rate adjusting means is eliminated and the flow rate is stabilized.

As a result, the amount of heating does not change with the change in flow rate, and the change in outflow temperature is reduced, so that a stable hot water temperature can be obtained. Moreover, at this time, since the heating means operates at a specific heating amount or more close to the maximum heating capacity, as much flow rate as possible can be obtained for the set temperature.

[Example] Next, the present invention will be explained based on examples.

In a gas water heater 1 whose outline is shown in FIG. 2, a burner plate 11 made of ceramics is disposed inside a water heater case 10.
The combustor is divided into a combustion chamber 10a and a mixing chamber 10b, and a blower 12 is provided below the water heater case 10 for supplying combustion air.

The blower 12 includes an impeller 12b inside a scroll casing 12a, and is driven by a DC motor (not shown).
2b is rotated. The scroll casing 12a is provided with a nozzle 13 for ejecting fuel gas.

A large number of flame ports 11a are formed on the burner plate 11,
The water heater case 10 and the burner plate 11 form a total air burner that burns only with primary air supplied by a blower 12, and combustion exhaust gas is discharged to the outside of the water heater case 10 from an exhaust port (not shown). In addition, mixing chamber 10
A rectifier plate 10c provided with a large number of holes is disposed within b in order to equalize the air-fuel mixture supplied by the blower 12 to the burner plate 11.

In the combustion chamber 10a, an ignition electrode 14 for performing spark discharge and a thermocouple 15 for detecting the temperature of the burner plate 11 are provided near the burner plate 11.

A heat exchanger 16 is disposed within the combustion chamber 10a, and a water supply pipe 16 upstream of the heat exchanger 16 is connected to a water supply source (not shown).
A is equipped with a flow rate sensor 17 that detects the amount of incoming water by rotating an impeller with the water flow, an incoming water temperature thermistor 18 that detects the temperature of the incoming water, and a water amount control device 19 that adjusts the amount of incoming water, and is connected to the hot water tap 20. A hot water outlet pipe 16b downstream of the heat exchanger 16 is provided with a hot water outlet temperature thermistor 21 for detecting the temperature of heated hot water.

The water flow control device 19 is a flow rate adjustment means that adjusts the flow rate by a valve body driven by a geared motor.
If the tapped water temperature detected by the controller has reached the set temperature, the opening is increased to increase the flow rate, and if the tapped water temperature does not reach the set temperature, the opening is decreased to increase the flow rate. Perform actions to reduce

On the other hand, in the fuel pipe 25 that guides the fuel gas to the nozzle 13, there are solenoid valves 26.2 and 26.
7, and a governor proportional valve 28 that adjusts the pressure on the downstream side of the fuel gas according to the current value.

The gas water heater 1 having the above configuration includes a control device 40 centered on a microcomputer that performs necessary control operations according to a pre-installed program.
controlled by

As shown in FIG. 3, the control device 40 includes a temperature control section 41.
, a combustion control section 42, a water flow control section 43, and a sequence control section 44 that controls the entire sequence such as ignition control, and is externally equipped with a controller 50 for setting a target hot water temperature. ing.

The functions of each mechanical flow section will be explained below.

The temperature control unit 41 calculates a feedforward control amount (as the burner combustion amount) from the inlet water temperature detected by the hot water supply start waiting water temperature thermistor 18, the set temperature set by the controller 50, and the flow rate detected by the flow rate sensor 17. The combustion amount Q is finally determined by deducing the FF control amounts) Q and F, and further adding the feedback control amount (FB control amount) QFI based on the exit hot water temperature detected by the exit hot water temperature thermistor 21.

In this case, the determined combustion amount Q is determined by comprehensively determining the maximum combustion amount Q based on the shape and volume of the water heater case 10, the size and flame port of the burner plate 11, the diameter of the nozzle 13, the characteristics of the governor proportional valve 28, etc. IaX and minimum combustion amount QlaX
is determined, and the combustion amount Q is determined within that range.

The combustion control section 42 controls the voltage applied to the DC motor of the blower 12 according to the combustion amount Q determined by the temperature control section 41 .

Further, the rotation speed detection unit 42a detects the rotation speed of the motor of the blower 12, and controls the current value to the governor proportional valve 28 in accordance with the detected rotation speed.

Note that the blower 12 does not operate until a predetermined period of time has elapsed after ignition.
In order to supply more fuel gas than the supply amount corresponding to the rotation speed, the current value to the governor proportional valve 28 is increased.

After the predetermined time has elapsed, based on the output voltage of the thermocouple 15, the fuel supply amount for air-fuel ratio correction is calculated based on the excess or deficiency of the combustion temperature with respect to the rotation speed of the blower 12.
A corrected current value corresponding to the corrected fuel gas is applied.

In this case, in order to eliminate sudden changes in the air-fuel ratio,
The current value is changed gradually over a period of, for example, about 10 seconds.

The water flow control unit 43 adjusts the flow rate of water passing through the heat exchanger 16 using the water flow control device 19, and opens the water flow control device 19 according to the outlet temperature so that as much flow as possible can be obtained for the set temperature. As described above, when the hot water temperature detected by the hot water temperature thermistor 21 reaches the set temperature, the opening degree is increased to increase the flow rate, so that the hot water temperature changes to the set temperature. If the amount of combustion is less than q, the opening is made smaller to reduce the flow rate.In particular, here, the specific combustion amount is the combustion amount that is smaller than the maximum combustion amount QIaX as the maximum heating amount of the burner by the predetermined combustion amount q. If the combustion amount Q, which is predetermined as Qp and determined by the temperature control unit 41, is less than the specific combustion amount Qp, both the flow rate increasing operation and the decreasing operation are performed, but the determined combustion amount When Q exceeds the specific combustion amount Qp, the flow rate is not increased but only the flow rate is decreased.

This specific combustion amount Qp is a value set to be smaller than the maximum combustion amount Q by, for example, about 3 to 10%, and is a value very close to the maximum combustion amount Qmax.

As a result, when the flow rate is changed around the specific combustion amount QlaX, if the combustion IQ exceeds the specific combustion amount Qp, the flow rate is only reduced to the flow rate that brings the outlet hot water temperature to the set temperature. , since it is not increased,
There is no change in flow rate caused by the water flow control device 19.

The sequence control unit 44 performs ignition control in a predetermined sequence when the flow rate sensor 17 detects the inflow of water into the heat exchanger 16, and performs extinguishing control when the stoppage of the inflow is detected.

Further, ignition is detected by a thermocouple 15, and if a misfire occurs, the supply of fuel gas is stopped for safety.

Next, the operation of the gas water heater 1 of this embodiment having the above tank bottom will be explained with reference to FIG. 1, focusing on water flow control.

When the user operates the hot water faucet 20 to start hot water supply and the flow of water is detected by the flow rate sensor 17, ignition control is performed in a predetermined sequence, the solenoid valves 26 and 27 are opened, and the ignition is started. A spark discharge occurs at the electrode 14 to ignite.

During this ignition control, the temperature control section 41 sets the feedforward control amount (FF control amount) Q to the combustion amount Q as an initial control (step 4), and the combustion control section 42 sets the feedforward control amount (FF control amount) Q to the combustion amount Q. In addition to controlling the blower 12, the governor proportional valve 28 is controlled by detecting its rotation speed.

At this time, the water flow control device 19 is maintained at the same opening as when it was used last time, and water flows through the heat exchanger 16 at a flow rate determined according to the opening of the hot water tap 20 and the pressure of the water supply source such as the water supply. pass.

After that, the combustion amount Q is determined by adding a feedback control amount (FB control amount) QF8 including the temperature detected by the hot water temperature thermistor 21, and when the hot water temperature TOtlt detected by the hot water temperature thermistor 21 reaches the set temperature T set. It is determined whether or not there is one.

If the outlet temperature Tout has reached the set temperature 'rset (YES in step 2), it is determined whether the combustion amount Q has reached the maximum combustion amount IQlaX, and if the combustion amount Q has reached the maximum combustion amount QlaX. (YES in step 3), heating l control is performed (step 4), and the combustion amount Q is maintained according to the hot water supply state.

If the combustion amount Q has not reached the maximum heating amount QIaX (No in step 3), the combustion amount Q is the specific combustion amount Q.
It is determined whether p has been reached.

If the combustion amount Q has not reached the specific combustion amount Qp (No in step 5), there is surplus heating capacity, so an operation is performed to increase the flow rate in order to supply as much hot water as possible (step 6).

If the combustion amount Q has reached the specific combustion amount Qp (YES in step 5), proceed to step 4 without performing an operation to increase the flow rate, and only perform heating amount control to stabilize the hot water temperature. Plan.

This is because if an operation to increase the flow rate is performed and the combustion amount Q increases accordingly, there will be a case where the hot water temperature 'rout will not reach the set temperature 'rset because there is little remaining heating capacity. This is because if the decreasing operation is performed, the tapped water temperature tends to become unstable.

In some step 2, if the outlet temperature Tout has not reached the set temperature Tset (No), it is determined whether the combustion amount Q has reached the maximum combustion amount Q■aX, and the combustion amount Q is the maximum combustion amount. If the amount QlaX has been reached (YES in step 7), the amount of heating cannot be increased any further, so the opening degree of the water amount control device 19 is reduced to reduce the flow rate passing through the heat exchanger 16. perform an action (
Step 8>.

In step 7, if the combustion amount Q has not reached the maximum combustion amount QIaX (No), proceed to step 4, change the combustion amount Q by heating amount control, obtain an appropriate combustion amount Q, and If there is a surplus in the amount of heating, the flow rate increasing operation in step 6 is performed via steps 3 and 5.

By performing the above operations, the combustion amount Q will always be increased to around the specific heating amount Qq, and it will be possible to demonstrate the ability close to the maximum combustion amount Qwax.
As much hot water as possible can be supplied for the set temperature.

In addition, when the combustion amount Q exceeds the specific combustion amount Qp, there is no shortage of heating power, and the operation to increase the flow rate is not performed, so hunting of the water amount control device 19 does not occur. There is no change in outlet temperature due to flow rate changes, and a stable outlet temperature can be obtained.

In this embodiment, all of the water supplied from the water supply pipe passes through the heat exchanger, but by connecting the water supply pipe and the hot water outlet pipe with a bypass pipe, some of the water supplied from the water supply pipe is connected. A water heater may also have a water circuit with a bypass pipe that prevents the water from passing through the heat exchanger.

In this embodiment, the controller allows the temperature of hot water to be freely set, but the set temperature may be fixed.

In this embodiment, the feedforward control amount (FF control amount) Qa is used, but the heating amount may be determined only by the feedback control amount (FB control 1) Qs.

Although this embodiment shows a combustor with a ceramic burner plate arranged inside the casing, the burner plate may be made of metal, or may be a sheet metal burner or a cast burner other than the burner plate.

In this embodiment, a gas water heater is shown, but the heating source is not limited to gas, and may be an oil burner or an electric water heater.

[Brief explanation of drawings]

Fig. 1 is a flowchart for explaining the operation of the control device of this embodiment, Fig. 2 is a block diagram showing a schematic configuration of a gas water heater according to this embodiment of the present invention, and Fig. 3 is a control diagram of the present embodiment. FIG. 2 is a functional block diagram showing the device. In the figure, 11... burner plate (heating means), 16...
...Heat exchanger, 17...Flow rate sensor (flow rate detection means)
, 19... water flow control device (flow I adjustment means), 21...
・Outlet hot water temperature thermistor (outflow temperature detection means), 40...
Control device (water heater control device), 50... Controller (temperature setting means).

Claims (1)

[Scope of Claims] 1) Temperature setting means for setting the temperature of hot water flowing out from a water circuit including a heat exchanger heated by a heating means, and outflow temperature detection detecting the temperature of hot water flowing out from the water circuit. means,
A flow rate detection means for detecting the flow rate of water passing through the water circuit is provided, and the amount of heating by the heating means is controlled based on a temperature difference between a set temperature of the temperature setting means and a temperature detected by the outflow temperature detection means. In addition, in a water heater control device that controls a flow rate adjusting means that adjusts a flow rate passing through the water circuit based on the temperature difference, a heating amount smaller than a maximum heating amount of the heating means by a predetermined amount is set as a specific heating amount. A control device for a water heater, characterized in that the flow rate increasing operation by the flow rate adjusting means is performed only when the heating amount of the heating means is smaller than the specific heating amount.