JP2021089110A - Water heater - Google Patents

Abstract

To solve a problem that there is the possibility that occurrence of fan clogging might increase the amount of gas jetting out from a burner due to reduction in inner pressure of a combustion casing and thus cause incomplete combustion in a water heater that includes a fan supplying combustion air into the combustion casing with a burner and a hot water supply heat exchanger built therein and a proportional valve interposed in a gas supply passage and that controls fan rotational frequency on the basis of a combustion characteristic line indicating a correlation between a proportional valve electric current value predetermined to perform normal combustion of the burner and the fan rotational frequency.SOLUTION: When an exhaust clogging rate is a predetermined value or greater and a proportional valve electric current value Ip is equal to or greater than a predetermined electric current value YIp close to an upper limit value, actual combustion amount Qj calculated from heating amount in a heat exchanger and a design combustion amount Qs calculated from the proportional valve electric current value are compared with each other. When Qj is larger than Qs by a predetermined rate or greater, a combustion characteristic line used for controlling fan rotational frequency is switched to correction combustion characteristic line L1-L5 in which a change rate of the fan rotational frequency relative to the proportional valve electric current value is set larger than a reference combustion characteristic line L.SELECTED DRAWING: Figure 2

Description

The present invention communicates with a combustion case, a burner provided in the combustion case, a heat exchanger for hot water supply heated by combustion gas generated by combustion in the burner provided in the combustion case, and the combustion case. The present invention relates to a hot water supply device including an exhaust path for discharging combustion gas that has passed through a heat exchanger, a combustion fan for supplying combustion air into a combustion housing, and a proportional valve provided in a gas supply path to a burner. ..

Originally, in this type of hot water supply device, the combustion of the burner is burned with the combustion fan rotation speed as the fan rotation speed, the energizing current value for the combustion fan as the fan current value, and the energizing current value for the proportional valve as the proportional valve current value. The proportional valve current value is controlled so that the amount is the amount of combustion that brings the hot water supply temperature to a predetermined set temperature, and the correlation between the proportional valve current value and the fan rotation speed that is predetermined so that the burner burns normally is maintained. The fan speed is controlled based on the combustion characteristic line shown. Further, when the exhaust passage is blocked, the amount of air blown decreases even if the fan rotation speed is the same, and the fan current value decreases. Therefore, the blockage rate of the exhaust passage can be calculated from the correlation between the fan speed and the fan current value. Then, conventionally, control is performed to correct the fan rotation speed according to the blockage rate of the exhaust passage calculated from the correlation between the fan rotation speed and the fan current value, and the amount of combustion air corresponding to the combustion amount of the burner is generated. A hot water supply device that has been made to be supplied is known (see, for example, Patent Document 1).

By the way, when the hot water supply device is used to some extent, dust or the like may be clogged between the blades of the combustion fan. When such fan clogging occurs, the fan current value decreases due to the decrease in the amount of air blown even if the fan rotation speed is the same. Then, in the above-mentioned conventional example, even when the fan is clogged, it is determined that the exhaust passage is blocked, and the control for correcting the fan rotation speed is performed, and the amount corresponding to the combustion amount at that time is performed. Combustion air is supplied.

However, when the fan is clogged, the internal pressure of the combustion casing decreases. Here, the amount of gas ejected from the burner is determined by the differential pressure between the pressure of the gas supplied to the burner and the pressure inside the combustion casing. Therefore, when the internal pressure of the combustion housing decreases due to the clogging of the fan, the amount of gas ejected from the burner increases, and the actual combustion amount of the burner becomes larger than the design combustion amount obtained from the proportional valve current value. Therefore, even if the fan speed is corrected as described above, the supply amount of combustion air is only the amount corresponding to the design combustion amount, and is smaller than the amount corresponding to the actual combustion amount. Then, in the region where the proportional valve current value is large, the degree of insufficient supply of combustion air with respect to the actual combustion amount becomes large, and incomplete combustion occurs.

Japanese Unexamined Patent Publication No. 8-247452

In view of the above points, it is an object of the present invention to provide a hot water supply device capable of preventing incomplete combustion due to fan clogging.

In order to solve the above problems, the present invention presents the combustion casing, the burner provided in the combustion casing, and the heat for hot water supply heated by the combustion gas generated by the combustion in the burner provided in the combustion casing. It is installed in the exchanger, the exhaust path that communicates with the combustion casing and discharges the combustion gas that has passed through the heat exchanger, the combustion fan that supplies the combustion air into the combustion casing, and the gas supply path to the burner. A hot water supply device equipped with a proportional valve, in which the combustion fan rotation speed is the fan rotation speed, the energizing current value to the combustion fan is the fan current value, and the energizing current value to the proportional valve is the proportional valve current value. The proportional valve current value is controlled so that the amount is the amount of combustion that brings the hot water supply temperature to a predetermined set temperature, and the correlation between the proportional valve current value and the fan rotation speed that is predetermined so that the burner burns normally is maintained. In the case where the fan rotation speed is controlled based on the represented combustion characteristic line, and the fan rotation speed is corrected according to the blockage rate of the exhaust passage calculated from the correlation between the fan rotation speed and the fan current value. , When the calculated exhaust passage blockage rate is equal to or higher than the predetermined value and the proportional valve current value is equal to or higher than the predetermined current value close to the upper limit value, the actual combustion amount of the burner obtained from the heating amount in the heat exchanger. Compare with the design combustion amount of the burner obtained from the proportional valve current value, and when the actual combustion amount is larger than the design combustion amount by a predetermined ratio or more, the combustion characteristic line used for controlling the fan rotation speed becomes the reference. It is characterized by switching to a modified combustion characteristic line in which the rate of change of the fan rotation speed with respect to the proportional valve current value is set larger than that of the combustion characteristic line.

According to the present invention, when a fan is clogged, the proportional valve current value is equal to or higher than a predetermined current value close to the upper limit value, and the actual combustion amount is larger than the design combustion amount by a predetermined ratio or more, that is, it is incomplete as it is. When combustion occurs, the combustion characteristic line used to control the fan speed is switched to the modified combustion characteristic line. Then, in the modified combustion characteristic line, the fan rotation speed is increased at the same proportional valve current value as compared with the reference combustion characteristic line, so that an amount of combustion air corresponding to the actual combustion amount is supplied. Therefore, incomplete combustion due to fan clogging can be prevented.

Further, in the present invention, it is desirable that the larger the rate of increase of the actual combustion amount with respect to the design combustion amount, the larger the rate of change of the fan rotation speed with respect to the proportional valve current value of the modified combustion characteristic line. According to this, as the rate of increase in the actual combustion amount with respect to the design combustion amount increases, the rate of increase in the supply amount of combustion air increases, and incomplete combustion can be prevented more reliably.

By the way, the actual combustion amount is obtained by dividing the heat amount in the heat exchanger obtained by multiplying the deviation between the hot water supply temperature and the water supply temperature to the heat exchanger by the hot water supply flow rate by the heat exchange efficiency of the heat exchanger. .. When the cumulative operating time of the hot water supply device becomes long, the heat exchanger deteriorates, the actual heat exchange efficiency of the heat exchanger decreases, and the actual combustion amount obtained from the heat amount in the heat exchanger is the actual value. Will be lower than. Even so, the actual combustion amount is larger than the design combustion amount because the fan clogging progresses and the amount of gas ejected from the burner increases.

Therefore, in the present invention, it is desirable that the longer the cumulative operating time of the water heater, the larger the rate of change of the fan rotation speed with respect to the proportional valve current value of the modified combustion characteristic line. According to this, even if the actual combustion amount is larger than the actual combustion amount obtained from the heating amount in the heat exchanger due to the deterioration of the heat exchanger, the amount corresponding to the actual combustion amount. It can supply combustion air and contributes to the prevention of incomplete combustion.

Explanatory drawing of the hot water supply apparatus of embodiment of this invention. The flow chart which shows the content of the switching control of the combustion characteristic line performed by the control means of the water heater of an embodiment. The graph which shows the reference combustion characteristic line and each of the 1st to 5th modified combustion characteristic lines.

The hot water supply device of the embodiment of the present invention shown in FIG. 1 includes a combustion casing 2 housed in a housing 1. Inside the combustion casing 2, a burner 3 is provided at the lower part and a heat exchanger 4 for hot water supply is provided at the upper part, and the heat exchanger 4 is heated by the combustion gas generated by the combustion in the burner 3. An exhaust passage 21 communicating with the combustion casing 2 is connected to the upper end of the combustion casing 2, and the combustion gas that has passed through the heat exchanger 4 is discharged to the outside via the exhaust passage 21. Further, a combustion fan 5 for supplying combustion air into the combustion casing 2 is connected to the lower end of the combustion casing 2.

A main valve 7 and a proportional valve 8 are interposed in the gas supply path 6 to the burner 3. Further, the heat exchanger 4 is connected to a water supply channel 9 on the upstream side and a hot water supply channel 10 on the downstream side. The water supply channel 9 is provided with a water amount sensor 11, a water temperature sensor 12, and a water amount servo 13, and the hot water supply channel 10 is provided with a hot water temperature sensor 14.

Further, in the housing 1, a controller 15 which is a control means for controlling a combustion fan 5, a main valve 7, a proportional valve 8, a water amount servo 13, and the like is provided. Then, the controller 15 detects the water amount sensor 11, the water temperature sensor 12, the hot water temperature sensor 14, the fan rotation speed Nf (the rotation speed of the combustion fan 5), and the fan current value (the energization current value to the combustion fan 5), respectively. The omitted sensor detection signal is input.

When the hot water tap (not shown) at the downstream end of the hot water supply passage 10 is opened and water is passed through the heat exchanger 4, the controller 15 sets the main valve when the amount of water detected by the water amount sensor 11 exceeds the predetermined minimum working water amount. The valve 7 is opened and the igniter (not shown) is operated to ignite the burner 3. After that, the required combustion amount, which is the combustion amount required to set the hot water supply temperature to the predetermined set temperature set by the remote control (not shown), is calculated, and the proportional valve current is adjusted so that the combustion amount of the burner 3 becomes the required combustion amount. Combustion shown in FIG. 3 which controls the value Ip (the value of the energizing current to the proportional valve 8) and shows the correlation between the proportional valve current value Ip and the fan rotation speed Nf, which are predetermined so as to normally burn with the burner 3. The fan rotation speed Nf is controlled based on the characteristic line. In the present embodiment, first, the fan rotation speed Nf is controlled so that the rotation speed matches the proportional valve current value Ip required to obtain the required combustion amount on the combustion characteristic line, and then the proportional valve. Fan advance control is performed to control the current value Ip so that the current value matches the fan rotation speed Nf detected by the sensor on the combustion characteristic line. In this case as well, the proportional valve current value Ip is controlled so that the combustion amount of the burner 3 becomes the required combustion amount, that is, the combustion amount that sets the hot water supply temperature to the set temperature.

Further, the required combustion amount is the heat exchange efficiency of the heat exchanger 4 obtained by multiplying the deviation between the set temperature and the water supply temperature detected by the water temperature sensor 12 by the hot water supply flow rate detected by the water amount sensor 11 at the beginning of hot water supply. It is obtained by the feed-forward method by dividing by, and then it is obtained by the feedback method based on the actual hot water supply temperature detected by the hot water temperature sensor 14. When the required combustion amount exceeds the maximum combustion amount of the burner 3 (combustion amount when the proportional valve current value Ip is set as the upper limit value), the amount of water reaches the set temperature at the maximum combustion amount of the hot water supply flow rate. It is reduced by the servo 13.

Here, when the exhaust passage 21 is blocked, the amount of air blown decreases even if the fan rotation speed Nf is the same, and the fan current value decreases. Therefore, the controller 15 calculates the blockage rate of the exhaust passage 21 from the correlation between the fan rotation speed Nf and the fan current value, controls the fan rotation speed Nf to be corrected according to the blockage rate, and controls the burner 3. Make sure that the amount of combustion air corresponding to the amount of combustion is supplied. Specifically, the correction of the fan rotation speed Nf is performed by multiplying the rotation speed obtained based on the combustion characteristic line by the correction coefficient. The correction coefficient is, for example, 1.0 when the blockage rate of the exhaust passage 21 is less than 72%, 1.04 when the blockage rate is 72% or more and less than 81%, and the blockage rate is 81% or more. If it is less than 84%, it is 1.08, if the blockage rate is 84% or more and less than 86%, it is 1.12, if the blockage rate is 86% or more and less than 88%, 1.16, and the blockage rate is 88% or more. If it is less than 90%, it is set to 1.20, and if the blockage rate is 90% or more, combustion is stopped. Since the method for calculating the blockage rate of the exhaust passage 21 is known in Patent Document 1 and the like, the description thereof will be omitted.

When performing fan advance control, by correcting the fan rotation speed Nf, the fan rotation speed Nf detected by the sensor becomes a value obtained by multiplying the rotation speed obtained by the combustion characteristic line by the correction coefficient, and is obtained on the combustion characteristic line. The proportional valve current value Ip corresponding to the fan speed Nf becomes larger than the proportional valve current value Ip required to obtain the required combustion amount. Therefore, when the fan rotation speed Nf is corrected as described above, the proportional valve current value Ip becomes a current value that matches the rotation speed obtained by dividing the fan rotation speed Nf detected by the sensor by the correction coefficient on the combustion characteristic line. To control. As a result, the proportional valve current value Ip is controlled so that the combustion amount of the burner 3 becomes the required combustion amount.

By the way, when a fan is clogged with dust or the like between the blades of the combustion fan 5, the fan current value decreases due to a decrease in the amount of air blown even if the fan rotation speed Nf is the same, as in the case where the exhaust passage 21 is blocked. Then, even when the fan is clogged, it is determined that the exhaust passage 21 is blocked, and control is performed to correct the fan rotation speed Nf. However, when the fan is clogged, the internal pressure of the combustion housing 2 decreases, the amount of gas ejected from the burner 3 increases, and the actual combustion amount of the burner 3 is larger than the design combustion amount obtained from the proportional valve current value Ip. Become. Therefore, even if the fan rotation speed Nf is corrected as described above, the supply amount of combustion air is only the amount corresponding to the design combustion amount, and is smaller than the amount corresponding to the actual combustion amount. Then, in the region where the proportional valve current value Ip is large, the degree of insufficient supply of combustion air with respect to the actual combustion amount becomes large, and incomplete combustion occurs.

Therefore, in the present embodiment, the controller 15 controls the switching of the combustion characteristic line shown in FIG. 2 during the combustion of the burner 3. In this control, first, in STEP 1, the blockage rate of the exhaust passage 21 is calculated from the correlation between the fan rotation speed Nf and the fan current value, and then in STEP 2, the blockage rate is equal to or higher than a predetermined value (for example, 30%). Determine if it exists. If the blockage rate is equal to or higher than a predetermined value, the process proceeds to STEP3 to determine whether or not the cumulative operating time of the water heater from the beginning is 1000 hours or more, and if it is 1000 hours or more, the process proceeds to STEP4 and the cumulative operation time is accumulated. It is determined whether or not the operation time is 2000 hours or more.

If the cumulative operating time of the water heater is less than 1000 hours, the process proceeds from STEP 3 to STEP 5, and the cumulative operating time after switching the combustion characteristic line is 100 hours or more, or the number of times the combustion characteristic line is switched is zero. It is determined whether or not it is. If the determination result is "YES", the process proceeds to STEP6, and it is determined whether or not the proportional valve current value Ip is equal to or greater than a predetermined current value YIp (for example, 80% of the upper limit value) close to the upper limit value. Then, when Ip ≧ YIp, the process proceeds to STEP7, and the actual combustion amount Qj of the burner 3 is calculated. The actual combustion amount Qj of the burner 3 is obtained by multiplying the deviation between the hot water supply temperature detected by the hot water temperature sensor 14 and the water supply temperature detected by the water temperature sensor 12 by the hot water supply flow rate detected by the water amount sensor 11. It can be obtained by dividing the amount of heat in the heat exchanger 4 by the heat exchange efficiency of the heat exchanger 4.

After calculating the actual combustion amount Qj of the burner 3, the next step is STEP8, and the actual combustion amount Qj of the burner 3 is compared with the design combustion amount Qs of the burner 3 obtained from the proportional valve current value Ip, and the actual combustion amount is compared. The rate of increase of Qj with respect to the design combustion amount Qs is calculated. If the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is less than 1%, the process proceeds to STEP9, and the combustion characteristic line used for controlling the fan rotation speed Nf is the reference combustion shown by L in FIG. The process of maintaining the characteristic line (reference combustion characteristic line) is performed, and the process returns to STEP3. On the other hand, if the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 1% or more and less than 4%, the process proceeds to STEP10, and the combustion characteristic line used for controlling the fan rotation speed Nf is set to the upper limit of the fan rotation speed Nf. The upper limit of the proportional valve current value Ip was set to 2% lower than the upper limit of the reference combustion characteristic line L without changing the value Nfmax. Return. If the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 4% or more, the process proceeds to STEP11, and the combustion characteristic line used for controlling the fan rotation speed Nf is not changed by changing the upper limit value Nfmax of the fan rotation speed Nf. The upper limit of the proportional valve current value Ip is set to be 4% lower than the upper limit Ipmax of the reference combustion characteristic line L. The process of switching to the third modified combustion characteristic line shown by L3 in FIG. 3 is performed, and the process returns to STEP3. The first modified combustion characteristic line L1 has a larger rate of change of the fan rotation speed Nf with respect to the proportional valve current value Ip than the reference combustion characteristic line L, and the third modified combustion characteristic line L3 has the fan rotation with respect to the proportional valve current value Ip. The rate of change of several Nf becomes larger than the first modified combustion characteristic line L1. In each modified combustion characteristic line, the lower limit value Ipmin of the proportional valve current value Ip and the lower limit value Nfmin of the fan rotation speed Nf are the same as the reference combustion characteristic line L.

According to the above control, when the fan is clogged, the proportional valve current value Ip is equal to or higher than the predetermined current value YIp close to the upper limit value, and the actual combustion amount Qj is 1% or more larger than the design combustion amount Qs, that is, If incomplete combustion occurs as it is, the combustion characteristic line used for controlling the fan rotation speed Nf is switched to the first modified combustion characteristic line L1. Then, in the first modified combustion characteristic line L1, the fan rotation speed Nf becomes larger at the same proportional valve current value Ip as compared with the reference combustion characteristic line L, so that an amount of combustion air corresponding to the actual combustion amount Qj is supplied. To. Therefore, incomplete combustion due to fan clogging can be prevented. Further, when the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 4% or more, the combustion characteristic line used for controlling the fan rotation speed Nf has a larger change rate of the fan rotation speed Nf with respect to the proportional valve current value Ip. By switching to the third modified combustion characteristic line L3, the rate of increase in the supply amount of combustion air becomes large, and incomplete combustion can be prevented more reliably.

If the cumulative operating time of the hot water supply device is 1000 hours or more and less than 2000 hours, proceed from STEP 4 to STEP 12, and the cumulative operating time after switching the combustion characteristic line is 100 hours or more, or the cumulative operating time is 1000 hours or more. It is determined whether or not the number of times of switching of the combustion characteristic line of is zero. If the determination result is "YES", the process proceeds to STEP13, and it is determined whether or not the proportional valve current value Ip is equal to or greater than the predetermined current value YIp. Then, when Ip ≧ YIp, the actual combustion amount Qj of the burner 3 is calculated in STEP14, and then the design combustion of the burner 3 obtained from the actual combustion amount Qj of the burner 3 and the proportional valve current value Ip in STEP15. The rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is calculated by comparing with the amount Qs. If the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is less than 1%, the process proceeds to STEP 16 to maintain the combustion characteristic line used for controlling the fan rotation speed Nf at the reference combustion characteristic line L. , Return to STEP3. On the other hand, if the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 1% or more and less than 4%, the process proceeds to STEP17 and the combustion characteristic line used for controlling the fan rotation speed Nf is set to the first modified combustion characteristic line L1. The process of switching to STEP3 is performed, and the process returns to STEP3. If the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 4% or more, the process proceeds to STEP18, and the combustion characteristic line used for controlling the fan rotation speed Nf is changed without changing the upper limit value Nfmax of the fan rotation speed Nf. The upper limit of the proportional valve current value Ip is 5% lower than the upper limit Ipmax of the reference combustion characteristic line L. The process of switching to the fourth modified combustion characteristic line shown by L4 in FIG. 3 is performed, and the process returns to STEP3.

If the cumulative operation time of the hot water supply device is 2000 hours or more, proceed from STEP 4 to STEP 19, and the cumulative operation time after switching the combustion characteristic line is 100 hours or more, or the combustion characteristic line when the cumulative operation time is 2000 hours or more. It is determined whether or not the number of times of switching is zero. If the determination result is "YES", the process proceeds to STEP 20, and it is determined whether or not the proportional valve current value Ip is equal to or greater than the predetermined current value YIp. Then, when Ip ≧ YIp, the actual combustion amount Qj of the burner 3 is calculated in STEP21, and then the design combustion of the burner 3 obtained from the actual combustion amount Qj of the burner 3 and the proportional valve current value Ip in STEP22. The rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is calculated by comparing with the amount Qs. If the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is less than 1%, the process proceeds to STEP23 to maintain the combustion characteristic line used for controlling the fan rotation speed Nf at the reference combustion characteristic line L. , Return to STEP3. On the other hand, if the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 1% or more and less than 4%, the process proceeds to STEP24, and the combustion characteristic line used for controlling the fan rotation speed Nf is set to the upper limit of the fan rotation speed Nf. The upper limit of the proportional valve current value Ip was set to be 3% lower than the upper limit of the reference combustion characteristic line L without changing the value Nfmax. Return to. If the rate of increase of the actual combustion amount Qj with respect to the design combustion amount Qs is 4% or more, the process proceeds to STEP25, and the combustion characteristic line used for controlling the fan rotation speed Nf is not changed by changing the upper limit value Nfmax of the fan rotation speed Nf. The upper limit of the proportional valve current value Ip is 6% lower than the upper limit Ipmax of the reference combustion characteristic line L. The process of switching to the fifth modified combustion characteristic line shown by L5 in FIG. 3 is performed, and the process returns to STEP3.

Here, if the cumulative operating time of the hot water supply device becomes long, the heat exchanger 4 deteriorates, the actual heat exchange efficiency of the heat exchanger 4 becomes lower than the design value, and the amount of heat exchanged by the heat exchanger 4 is exchanged. The actual combustion amount Qj obtained by dividing by the design value of efficiency is lower than the actual value. Even so, the actual combustion amount Qj becomes larger than the design combustion amount Qs because the fan clogging progresses and the gas ejection amount from the burner 3 further increases.

According to the above control, when the increase rate of the actual combustion amount Qj with respect to the design combustion amount Qs is 1% or more and less than 4%, and the cumulative operation time is 2000 hours or more, the cumulative operation time is less than 2000 hours. It is switched to the second modified combustion characteristic line L2 in which the rate of change of the fan speed Nf with respect to the proportional valve current value Ip is larger than that of the first modified combustion characteristic line L1 which is sometimes switched, and further, the design combustion amount Qs of the actual combustion amount Qj. If the cumulative operating time is 1000 hours or more and less than 2000 hours, the proportional valve current is larger than the third modified combustion characteristic line L3, which is switched when the cumulative operating time is less than 1000 hours. If the rate of change of the fan speed Nf with respect to the value Ip is switched to the fourth modified combustion characteristic line L4 and the cumulative operating time is 2000 hours or more, the fan with respect to the proportional valve current value Ip is higher than the fourth modified combustion characteristic line L4. It is switched to the fifth modified combustion characteristic line L5 in which the rate of change of the rotation speed Nf is large. In this way, if the rate of change of the fan rotation speed Nf with respect to the proportional valve current value Ip of the modified combustion characteristic line increases as the cumulative operating time of the hot water supply device increases, heat exchange occurs due to deterioration of the heat exchanger 4. Even if the actual combustion amount is larger than the actual combustion amount Qj obtained from the heating amount in the vessel 4, the amount of combustion air corresponding to the actual combustion amount can be supplied, which contributes to the prevention of incomplete combustion. To do.

When it is determined that Ip <YIp in each STEP 6, 13, 20, proceed to each STEP 26, 27, 28, and the combustion characteristic line used for controlling the fan rotation speed Nf is changed to the combustion characteristic line before the previous switching. (For example, if the reference combustion characteristic line L was switched to the first modified combustion characteristic line L1 last time, the reference combustion characteristic line L) is performed, and the process returns to STEPs 6, 13 and 20, respectively. Further, the combustion characteristic lines in STEP10, 11, 17, 18, 24, 25 and STEP 26, 27, 28 described above are gradually switched. Further, when the blockage rate of the exhaust passage 21 becomes 72% or more in a state where the switching to any of the modified combustion characteristic lines is performed, the rotation speed obtained based on the modified combustion characteristic line is described above. The fan speed Nf is corrected by multiplying the correction coefficient.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention.

2 ... Combustion box, 21 ... Exhaust path, 3 ... Burner, 4 ... Heat exchanger, 5 ... Combustion fan, 6 ... Gas supply path, 8 ... Proportional valve, Nf ... Fan rotation speed, Ip ... Proportional valve current value, L ... Reference combustion characteristic line, L1 to L5 ... Corrected combustion characteristic line.

Claims (3)

The combustion case, the burner provided in the combustion case, the heat exchanger for hot water supply heated by the combustion gas generated by the combustion in the burner provided in the combustion case, and the heat exchange by communicating with the combustion case. A hot water supply device including an exhaust passage for discharging combustion gas that has passed through the vessel, a combustion fan for supplying combustion air into the combustion casing, and a proportional valve provided in the gas supply passage to the burner.
The combustion amount of the burner sets the hot water supply temperature to a predetermined set temperature, with the combustion fan rotation speed as the fan rotation speed, the energizing current value for the combustion fan as the fan current value, and the energizing current value for the proportional valve as the proportional valve current value. The proportional valve current value is controlled so as to be the amount of combustion, and the fan rotation speed is set based on the combustion characteristic line showing the correlation between the proportional valve current value and the fan rotation speed, which are predetermined so as to normally burn with the burner. In the control, the fan rotation speed is corrected according to the blockage rate of the exhaust passage calculated from the correlation between the fan rotation speed and the fan current value.
When the calculated exhaust passage blockage rate is equal to or higher than the predetermined value and the proportional valve current value is equal to or higher than the predetermined current value close to the upper limit value, the actual combustion amount of the burner obtained from the heating amount in the heat exchanger Comparing with the design combustion amount of the burner obtained from the proportional valve current value, when the actual combustion amount is larger than the design combustion amount by a predetermined ratio or more, the combustion characteristic line used for controlling the fan rotation speed is used as the reference combustion. A hot water supply device characterized by switching to a modified combustion characteristic line in which the rate of change of the fan rotation speed with respect to the proportional valve current value is set larger than that of the characteristic line. The hot water supply device according to claim 1, wherein the rate of change of the fan rotation speed with respect to the proportional valve current value of the modified combustion characteristic line increases as the rate of increase of the actual combustion amount with respect to the design combustion amount increases. The hot water supply device according to claim 1 or 2, wherein the longer the cumulative operating time of the hot water supply device is, the larger the rate of change of the fan rotation speed with respect to the proportional valve current value of the modified combustion characteristic line.

Images