WATER HEATER

Abstract

Processing executed by a water heater includes: performing a first ignition operation in a first test operation mode; in the case where ignition is detected, determining a combination of gas and an adjustment part to be abnormal; performing a second ignition operation in a second test operation mode; in the case where ignition is detected, determining a combination of gas and an adjustment part to be normal; and, in the case where no ignition is detected, determining a combination of gas and an adjustment part to be abnormal.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan Application No. 2023-211142, filed on Dec. 14, 2023. The entirety of the above-described patent application is hereby incorporated by reference herein and made a portion of the present specification.

BACKGROUND

Technical Field

The disclosure relates to a water heater, and more specifically, to a water heater capable of using multiple types of gas as heat sources.

Related Art

Conventionally, there has been known a water heater capable of accommodating each of different types of gas as a heat source (for example, see Patent Documents 1 to 5).

• • [Patent Document 1] Japanese Patent No. 3070720
  • [Patent Document 2] Japanese Patent Laid-Open No. 2007-24354
  • [Patent Document 3] Japanese Patent Laid-Open No. 2004-61026
  • [Patent Document 4] Japanese Patent No. 2567302
  • [Patent Document 5] Japanese Patent No. 3918550

In the water heater, according to the gas used as fuel for the heat source, a part corresponding to the gas may be used. Since each gas has a different calorific value, it is necessary to use the part corresponding to the gas in order to operate the water heater normally. Accordingly, a technique is required for accurately determining whether a combination of gas and a part is correct.

SUMMARY

A water heater is provided capable of using each of multiple types of gas as fuel. A first type of gas among the multiple types of gas has a greater calorific value than a second type of gas. The water heater includes: a venturi, including an air intake port and a gas intake port, including a supply path of air and gas to a combustion chamber, and where the gas is drawn in response to negative pressure generated by passing air; an adjustment part, replaceably incorporated into a gas supply path, including a flow path that defines a supply amount according to a gas type; a fan, mixing air and gas and supplying the mixed air and gas to the combustion chamber; a burner, for combusting gas; an ignition part, igniting the burner; a sensor, detecting that combustion is being performed in the combustion chamber; and a control device, operating the water heater in multiple test operation modes. In a first test operation mode among the multiple test operation modes, the control device causes the fan to rotate at a rotation speed preset to be lower than a rotation speed during normal ignition. The control device causes the ignition part to ignite the burner. In the case where combustion is detected before a predetermined first time elapses from the ignition of the burner, considering that the first type of gas is being supplied to the combustion chamber and an adjustment part for the second type of gas is incorporated into the water heater, the control device determines a combination of the gas used as fuel and the adjustment part to be erroneous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a portion of a hardware configuration of a water heater 100 according to the present embodiment.

FIG. 2 more specifically illustrates a configuration of a venturi 152 and a venturi fitting 160 in an air supply section 140.

FIG. 3 illustrates a relationship between volume percent concentration (vol %) of CO₂ during ignition and time required for a gas mixture to ignite.

FIG. 4 illustrates a relationship between rotation speed of a fan 154 during ignition and time required for a gas mixture to ignite.

FIG. 5 illustrates a relationship between rotation speed of the fan 154 and time required for a gas mixture to ignite for the same gas.

FIG. 6 illustrates an overview of processing for determining whether an adjustment part 170 corresponding to a gas type is attached to the venturi 152 in the water heater 100.

FIG. 7 is a flowchart illustrating a portion of processing executed by a control circuit 110 of the water heater 100.

DESCRIPTION OF THE EMBODIMENTS

The disclosure provides a water heater in which it can be determined whether a combination of gas and a part that should be used according to the gas is correct.

According to one embodiment, a water heater is provided capable of using each of multiple types of gas as fuel. A first type of gas among the multiple types of gas has a greater calorific value than a second type of gas. The water heater includes: a venturi, including an air intake port and a gas intake port, including a supply path of air and gas to a combustion chamber, and where the gas is drawn in response to negative pressure generated by passing air; an adjustment part, replaceably incorporated into a gas supply path, including a flow path that defines a supply amount according to a gas type; a fan, mixing air and gas and supplying the mixed air and gas to the combustion chamber; a burner, for combusting gas; an ignition part, igniting the burner; a sensor, detecting that combustion is being performed in the combustion chamber; and a control device, operating the water heater in multiple test operation modes. In a first test operation mode among the multiple test operation modes, the control device causes the fan to rotate at a rotation speed preset to be lower than a rotation speed during normal ignition. The control device causes the ignition part to ignite the burner. In the case where combustion is detected before a predetermined first time elapses from the ignition of the burner, considering that the first type of gas is being supplied to the combustion chamber and an adjustment part for the second type of gas is incorporated into the water heater, the control device determines a combination of the gas used as fuel and the adjustment part to be erroneous.

In one aspect, in the case where no combustion is detected in the first test operation mode, the control device ends the first test operation mode and transitions to a second test operation mode different from the first test operation mode. The control device causes the fan to rotate at a rotation speed pre-defined as the rotation speed during normal ignition. The control device causes the ignition part to ignite the burner. In the case where no combustion is detected before a predetermined second time elapses from the ignition of the burner, considering that the second type of gas is being supplied to the combustion chamber and an adjustment part for the first type of gas is incorporated into the water heater, the control device determines a combination of the gas used as fuel and the adjustment part to be erroneous. In the case where combustion is detected before the second time elapses, the control device determines the combination to be correct.

In a water heater according to one embodiment, it can be determined whether a combination of any of multiple types of gas and an adjustment part is correct.

The following describes an embodiment of the disclosure with reference to the drawings. In the following description, identical parts are given identical reference numerals, and their names and functions are also the same. Accordingly, detailed descriptions of these parts will not be repeated.

One combustion method used in a water heater is a totally primary air combustion method. In the totally primary air combustion method, in the water heater, the whole of the air necessary for combustion is drawn as primary air, the primary air is mixed with gas used as fuel, and the mixed air and gas are sent to a combustion chamber. The gas is, for example, liquefied petroleum (LP) gas, natural gas, or the like.

A water heater 100 according to the present embodiment adopts the totally primary air combustion method in which combustion is performed after gas and air are completely mixed together in advance. In this method, there is less excess air compared to other methods (for example, rich-lean combustion method), and an improvement in thermal efficiency can thus be expected. A reduction in emitted NOx (nitrogen oxides) can also be expected.

Referring to FIG. 1, a configuration of the water heater 100 is described. FIG. 1 illustrates a portion of a hardware configuration of the water heater 100 according to the present embodiment. The water heater 100 includes a control circuit 110, a can body 136, an exhaust duct 132, an air supply section 140, a fan 154, and an elbow 156.

The can body 136 includes an ignition plug 120, a safety device 122, a valve 124, a frame rod 126, a thermistor 128, a primary heat exchanger 129, a secondary heat exchanger 130, a rectifying plate 134, and a burner 138.

The air supply section 140 includes a venturi 152, a venturi fitting 160, a pressure equalizing gas valve 162, and an adjustment part 170. The venturi 152 includes an intake port 150 and a gas hole 153. The intake port 150 takes in air. The pressure equalizing gas valve 162 is connected to a gas supply pipe and maintains a constant pressure of gas sent to the venturi fitting 160. When the fan 154 rotates, air flows in from the intake port 150, and in response to the negative pressure generated by the passing air, gas used as fuel flows in from the gas hole 153. The air and the gas that have flowed into the venturi 152 are sent to a mixing section 158 through the elbow 156. In the mixing section 158, the fan 154 mixes the air and the gas. The mixed air and gas are sent as a gas mixture for combustion to a combustion chamber 137.

The control circuit 110 controls an operation of the water heater 100. The ignition plug 120 receives a high voltage emitted by an igniter (not shown) and performs spark discharge. When the burner 138 is ignited by a spark, the gas mixture supplied to the combustion chamber 137 combusts. When combustion begins, a temperature of water flowing into the primary heat exchanger 129 from outside the water heater 100 rises.

The safety device 122 detects that the combustion by the burner 138 has spread in a direction different from a direction in which the primary heat exchanger 129 is provided, and sends a signal indicating this detection to the control circuit 110. When receiving this signal, the control circuit 110 closes the valve 124 and stops the supply of the gas mixture.

The frame rod 126 monitors the occurrence of ignition and combustion in the can body 136. A monitoring result is transmitted to the control circuit 110. In response to the monitoring result, the control circuit 110 may report a result such as combustion failure or normal operation.

The thermistor 128 detects the temperature of the water (hot water) supplied to the primary heat exchanger 129. The secondary heat exchanger 130 collects latent heat from the exhaust gas after primary heat exchange and heats water supplied to the secondary heat exchanger 130.

The exhaust duct 132 is connected to the outside of the water heater 100 and discharges the exhaust gas after heat exchange. The rectifying plate 134 regulates flow of the exhaust gas and efficiently discharges the exhaust gas.

The adjustment part 170 is provided between the venturi 152 and the venturi fitting 160. The venturi fitting 160 is connected to piping provided with the pressure equalizing gas valve 162 for controlling the amount of gas supplied.

The adjustment part 170 is a part for adjusting a supply amount of gas to be supplied to the water heater 100 according to characteristics of the gas. To change the size of the gas hole 153 formed in the venturi 152, it is necessary to remake the venturi 152 itself. On the other hand, by incorporating the adjustment part 170 into the venturi fitting 160, without remaking the venturi 152, substantially, a flow rate corresponding to the gas to be used may be supplied similarly to the case where the size of the gas hole 153 is changed to a size corresponding to the characteristics of the gas.

More specifically, the adjustment part 170 includes a hollow section through which the gas passes. The hollow section includes a narrowing portion. An inner diameter (orifice diameter) of the narrowing portion is determined according to a calorific value of the gas, so as to restrict the supply amount similarly to the gas hole 153. Accordingly, an installer of the water heater 100 may select an appropriate adjustment part 170 according to the type of gas used as fuel for the water heater 100, and incorporate the adjustment part 170 between the venturi 152 and the venturi fitting 160, thereby allowing the gas hole 153 that has an appropriate orifice diameter to be adopted, without machining the venturi 152.

Here, a relationship between the characteristics of the gas used in the water heater 100 and the adjustment part 170 is described. The water heater 100 is capable of using natural gas and LP gas as fuel. The calorific value (approximately 54 MJ/Nm³) of natural gas is less than the calorific value (approximately 81 MJ/Nm³) of LP gas.

Referring to FIG. 2, a configuration of the air supply section 140 is further described. FIG. 2 more specifically illustrates a configuration of the venturi 152 and the venturi fitting 160 in the air supply section 140.

The venturi 152 includes a flange 202. The venturi fitting 160 includes a flange 232. The adjustment part 170 includes a flange 171. The flange 232 of the venturi fitting 160 is joined to the flange 202 of the venturi 152 via a seal ring 210. When the flange 232 of the venturi fitting 160 and the flange 202 of the venturi 152 are joined by a bolt (not shown), the adjustment part 170 functions as the gas hole 153 corresponding to the gas used as fuel.

As an example, a size (for example, orifice diameter) that regulates a flow rate of the adjustment part 170 used in the case where either natural gas or LP gas is supplied as fuel has the following relationship.

• • Orifice diameter (approximately 7.9φ) of adjustment part 170 for natural gas>orifice diameter (approximately 7.7φ) of adjustment part 170 for LP gas

Accordingly, for example, when the adjustment part 170 that has a large orifice diameter for natural gas is used in the case where LP gas is the fuel, the gas having a great calorific value is supplied to the combustion chamber 137 more than necessary. As a result, incomplete combustion due to a so-called gas-rich condition occurs in the combustion chamber 137, leading to abnormal generation of carbon monoxide. Accordingly, the water heater 100 according to the present embodiment has a two-stage test operation mode. In a first test operation mode, the fan 154 operates at a rotation speed lower than a rotation speed during normal ignition, and performs a determination related to LP gas. Thereupon, the water heater 100 switches to a second test operation mode. The fan 154 operates at the rotation speed during normal ignition and performs a determination related to natural gas.

Referring to FIG. 3, a relationship between volume percent concentration of CO₂ and ignition time is described. FIG. 3 illustrates a relationship between the volume percent concentration (vol %) of CO₂ during ignition and time required for a gas mixture to ignite. Region 300 represents a range in which ignition is possible. As evident from FIG. 3, the lower the volume percent concentration of CO₂ during ignition, the longer the ignition time tends to be.

Referring to FIG. 4, a relationship between the rotation speed of the fan 154 and the ignition time is described. FIG. 4 illustrates a relationship between the rotation speed of the fan 154 during ignition and the time required for a gas mixture to ignite. Region 400 represents a range in which ignition is possible. As evident from FIG. 4, the lower the rotation speed of the fan 154 during ignition, the longer the time required for ignition. For example, in the case where the rotation speed is r (rpm), the ignition time is t (1) seconds. Since the fuel is gas, t (1) seconds is several seconds.

In the case where gas is used as fuel, if the gas type is the same, the larger the orifice diameter of a gas supply path, the larger the amount of gas supplied, thus resulting in a higher gas concentration in a gas mixture. The water heater 100 according to the present embodiment adopts the totally primary air combustion method in which ignition is performed by sending a spark to the gas mixture. In this method, as the gas concentration increases, the number of gas molecules that undergo oxidation reaction per unit time increases. Thus, an ignition timing becomes earlier (that is, the time required for ignition becomes shorter). The same applies to the rotation speed of the fan 154. That is, when the fan 154 operates at a low rotation speed, the gas mixture sent to the combustion chamber 137 is decreased, and the number of gas molecules that react per unit time decreases. As a result, the ignition timing becomes later (that is, the time required for ignition becomes longer). In the water heater 100 according to the present embodiment, whether a combination of the gas used as fuel and the adjustment part 170 is correct or erroneous is determined using such a relationship.

Accordingly, referring to FIG. 5, difference in range in which ignition is possible depending on the adjustment part is described. FIG. 5 illustrates a relationship between the rotation speed of the fan 154 and the time required for a gas mixture to ignite for the same gas. Region 500 represents a difference in range in which ignition is possible. Line 510 defines a range in which ignition is possible in the case where the adjustment part is for LP gas. Line 520 defines a range in which ignition is possible in the case where the adjustment part is for natural gas. Accordingly, region 500 represents the difference between these ranges in which ignition is possible.

That is, in the case of the same gas, since the orifice diameter of the adjustment part 170 for LP gas and the orifice diameter of the adjustment part 170 for natural gas are different, the rotation speed (ignitable rotation speed) at which ignition begins also differs. More specifically, considering a difference in calorific value of each gas, the orifice diameter of the adjustment part 170 for LP gas is smaller than the orifice diameter of the adjustment part 170 for natural gas. Accordingly, within a range of the ignitable rotation speed, in the water heater 100, it can be determined whether a combination of a gas type and the adjustment part 170 is correct or erroneous using a test operation mode in which ignition is performed.

In another aspect, in the water heater 100, the time for determining the presence or absence of ignition can be changed according to the test operation mode. The shorter the time, the greater the difference in ignitable rotation speed depending on the adjustment part 170. Thus, in the water heater 100, whether the combination is correct can be determined with high accuracy.

In the case where natural gas is used as fuel, a user (for example, the installer of the water heater 100) may cause the fan 154 to rotate at the rotation speed during normal ignition and perform an ignition operation of the water heater 100, thereby identifying whether the adjustment part 170 corresponding to the gas type is being used. That is, considering that the calorific value of natural gas is less than that of LP gas, the orifice diameter of the adjustment part 170 for natural gas is larger than the orifice diameter of the adjustment part 170 for LP gas. Accordingly, in the case where natural gas is the fuel, if ignition occurs when the fan 154 is operating at the rotation speed during normal ignition, it means that the adjustment part 170 with a larger orifice diameter, namely, the adjustment part 170 for natural gas, is being used, indicating that the combination of the gas and adjustment part 170 is correct. On the other hand, in the case where natural gas is the fuel, if ignition does not occur when the fan 154 is operating at the rotation speed during normal ignition, it means that the necessary amount of gas is not being supplied, indicating that the adjustment part 170 with a smaller orifice diameter, namely, the adjustment part 170 for LP gas, is being used in error. In the case where natural gas is used as fuel, it is possible to identify whether a predetermined adjustment part 170 is being correctly used in this manner.

Determination Processing

Referring to FIG. 6, determination processing by the water heater 100 is described. FIG. 6 illustrates an overview of processing for determining whether the adjustment part 170 corresponding to the gas type is attached to the venturi 152 in the water heater 100. The processing shown in FIG. 6 is executed in the case where the operation mode of the water heater 100 is the test operation mode. In the present embodiment, the test operation mode may include multiple modes. The multiple modes are described below as the first test operation mode and the second test operation mode.

In step S610, when detecting a test operation start instruction, the control circuit 110 starts the first test operation mode. The test operation start instruction is detected by depression of a physical switch (not shown) provided in the water heater 100, or by input of a control code indicating a test operation instruction. The control circuit 110 causes the fan 154 to rotate at a low rotation speed (for example, r(1) rpm in FIG. 5) preset as a rotation speed lower than a normal rotation speed, supplies a gas mixture to the combustion chamber 137, and starts an ignition operation.

After the ignition operation is started, gas may be ignited or may not be ignited within a predetermined time. For example, in one aspect, if the combination of the type of gas used as fuel and the adjustment part 170 is normal, since the fan 154 rotates at a speed equal to or lower than a rotation speed required for ignition of the gas, the gas is not ignited (step S620). In another aspect, in the case where natural gas is used as fuel, when the adjustment part 170 for LP gas is used in the venturi 152, since the adjustment part 170 for LP gas has a smaller orifice diameter than the adjustment part 170 for natural gas, the fuel necessary for combustion fails to be supplied, and the gas is not ignited (step S630).

On the other hand, when the adjustment part 170 for natural gas is incorporated into the water heater 100 in the case where LP gas is used as fuel, since the adjustment part 170 for natural gas has a larger orifice diameter than the adjustment part 170 for LP gas, the fuel necessary for ignition is supplied, and the gas is thus ignited (step S670). In this case, since an incorrect adjustment part 170 (that is, the adjustment part 170 for natural gas) is incorporated into the venturi 152 instead of the adjustment part 170 required for the gas (LP gas) used, the control circuit 110 determines the combination of the gas and the adjustment part 170 to be abnormal (step S680).

If the gas is not ignited (step S620 or step S630), the control circuit 110 switches the operation mode of the water heater 100 to the second test operation mode (step S640). In the second test operation mode, the control circuit 110 causes the fan 154 to rotate at a rotation speed (r(2) rpm) preset as a speed at which the fan 154 should be rotated during normal operation of the water heater 100, and supplies the gas mixture to the combustion chamber 137. In this case, r(1)<r(2).

If the combination of the type of gas used and the adjustment part 170 for the gas is correct, the gas is ignited (step S650). Accordingly, the control circuit 110 determines the combination of the gas and the adjustment part 170 to be correct (normality determination, step S670).

On the other hand, if the gas is not ignited (step S660), since an incorrect adjustment part 170 (that is, the adjustment part 170 for LP gas) is incorporated into the venturi 152 instead of the adjustment part 170 required for the natural gas used, the control circuit 110 determines the combination of the gas and the adjustment part 170 to be erroneous (abnormality determination, step S680).

Control Structure

Referring to FIG. 7, a control structure of the water heater 100 is described. FIG. 7 is a flowchart illustrating a portion of processing executed by the control circuit 110 of the water heater 100.

In step S710, the control circuit 110 switches the operation mode of the water heater 100 to the first test operation mode, and executes a first ignition operation under a predetermined first operating condition. More specifically, the control circuit 110 turns on an igniter (not shown), enables ignition at the ignition plug 120, opens a gas valve, and starts the supply of gas. At this time, the control circuit 110 sets the rotation speed of the fan 154 to r(1) (rpm) and determines the presence or absence of ignition within a threshold time (t(1) (seconds)) predetermined as an ignition determination time.

In step S720, the control circuit 110 determines whether combustion is being performed. More specifically, the control circuit 110 determines whether the frame rod 126 is on. If it is determined that the frame rod 126 is on (YES in step S720), the control circuit 110 switches the control to step S730. Otherwise (NO in step S720), the control circuit 110 switches the control to step S740.

In step S730, the control circuit 110 determines the combination of the gas used as fuel and the adjustment part 170 to be abnormal (erroneous) (step S670 in FIG. 6), and ends the first test operation mode. Furthermore, the control circuit 110 executes error notification to notify that the combination is abnormal (step S680 in FIG. 6). Subsequently, the control circuit 110 ends the operation of the water heater 100.

In step S740, the control circuit 110 scavenges the combustion chamber 137 and expels air from the combustion chamber 137.

In step S750, the control circuit 110 switches the operation mode of the water heater 100 to the second test operation mode, and executes a second ignition operation under a predetermined second operating condition. More specifically, the control circuit 110 turns on the igniter, enables ignition at the ignition plug 120 and opens a gas valve. At this time, the control circuit 110 sets the rotation speed of the fan 154 to r(2) (rpm) and determines the presence or absence of ignition within a threshold time (t(2) (seconds)) predetermined as the ignition determination time. Here, r(1)<r(2) and t(1)≥t(2).

In step S760, the control circuit 110 determines whether combustion is being performed. More specifically, the control circuit 110 determines whether the frame rod 126 is on. If it is determined that the frame rod 126 is on (YES in step S760), the control circuit 110 switches the control to step S770. Otherwise (NO in step S760), the control circuit 110 switches the control to step S790.

In step S770, the control circuit 110 scavenges the combustion chamber 137 and expels air from the combustion chamber 137.

In step S780, the control circuit 110 determines the combination of the gas used and the adjustment part 170 to be normal, outputs a determination result indicating that the combination is correct, and ends the second test operation mode.

In step S790, the control circuit 110 determines the combination of the gas used and the adjustment part 170 to be abnormal (step S660 in FIG. 6), outputs a determination result indicating that the combination is erroneous, and ends the second test operation mode. Furthermore, the control circuit 110 executes error notification to notify that the combination is erroneous (step S680 in FIG. 6). Subsequently, the control circuit 110 ends the operation of the water heater 100.

That is, in the first test operation mode, the control circuit 110 performs the ignition operation in a state in which the fan 154 is rotated at a speed (r(1)) lower than a predetermined rotation speed. If a gas mixture is ignited, the control circuit 110 detects that the combination of the gas and the adjustment part 170 is erroneous (the adjustment part 170 for natural gas is adopted for LP gas), and outputs a determination result indicating the same. On the other hand, if the gas mixture is not ignited by this ignition operation, the control circuit 110 transitions to the second test operation mode.

In the second test operation mode, the control circuit 110 performs the ignition operation in a state in which the fan 154 is rotated at a normal rotation speed. If no ignition occurs, the control circuit 110 detects that the combination of the gas and the adjustment part 170 is erroneous (the adjustment part 170 for LP gas is adopted for natural gas), determines the combination to be abnormal, and outputs a determination result. On the other hand, if the gas mixture is ignited by this ignition operation, the control circuit 110 determines the combination of the gas and the adjustment part 170 to be correct, outputs a determination result indicating the same, and ends the second test operation mode.

If it is determined that the combination is erroneous, in order to perform error notification to prompt confirmation of the adjustment part 170, the control circuit 110 performs message display, voice output, or indicator illumination or the like. In this case, the operation mode of the water heater 100 remains the test operation mode. On the other hand, if it is determined that the combination is correct, the control circuit 110 performs reporting indicating the same, and ends the test operation mode of the water heater 100.

As described above, in the water heater 100 according to the present embodiment, since whether a combination of gas and the adjustment part 170 is correct is determined based solely on a rotation speed during ignition, this determination can be realized without increasing complexity of the configuration of the water heater 100. In the water heater 100, it is determined whether a combination of a gas type and the adjustment part 170 is correct within a few seconds of determining the presence or absence of ignition. Thus, it is possible to make a determination within a short time. Since the fan 154 operates at a low rotation speed, it is less susceptible to the effects of so-called explosive ignition in which ignition occurs in a state in which gas has accumulated due to ignition delay. Accordingly, the determination can be realized without causing anxiety to an installation contractor or an end user of the water heater 100.

The embodiments disclosed herein should be considered as illustrative in all aspects and not restrictive. The scope of the disclosure is indicated not by the description above but by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A water heater, capable of using each of a plurality of types of gas as fuel, a first type of gas among the plurality of types of gas having a greater calorific value than a second type of gas, wherein the water heater comprises: a venturi, comprising an air intake port and a gas intake port, comprising a supply path of air and gas to a combustion chamber, and where the gas is drawn in response to negative pressure generated by passing air;an adjustment part, replaceably incorporated into a gas supply path, having an inner diameter according to a gas type;a fan, mixing air and gas and supplying the mixed air and gas to the combustion chamber;a burner, for combusting gas;an ignition part, igniting the burner;a sensor, detecting that combustion is being performed in the combustion chamber; anda control device, operating the water heater in a plurality of test operation modes,wherein the control device: in a first test operation mode among the plurality of test operation modes, causes the fan to rotate at a rotation speed preset to be lower than a rotation speed during normal ignition;causes the ignition part to ignite the burner; and,in response to combustion being detected before a predetermined first time elapses from the ignition of the burner, considering that the first type of gas is being supplied to the combustion chamber and an adjustment part for the second type of gas is incorporated into the water heater, determines a combination of the gas used as fuel and the adjustment part to be erroneous.

2. The water heater according to claim 1, wherein the control device: in response to no combustion being detected in the first test operation mode, ends the first test operation mode and transitions to a second test operation mode different from the first test operation mode;causes the fan to rotate at a rotation speed pre-defined as the rotation speed during normal ignition;causes the ignition part to ignite the burner;in response to no combustion being detected before a predetermined second time elapses from the ignition of the burner, considering that the second type of gas is being supplied to the combustion chamber and an adjustment part for the first type of gas is incorporated into the water heater, determines a combination of the gas used as fuel and the adjustment part to be erroneous; and,in response to combustion being detected before the second time elapses, determines the combination to be correct.

3. The water heater according to claim 1, wherein the first type of gas is liquefied petroleum gas; andthe second type of gas is natural gas.

4. The water heater according to claim 2, wherein the first type of gas is liquefied petroleum gas; andthe second type of gas is natural gas.

5. The water heater according to claim 1, further comprising: a reporting part, reporting a result of any of the determinations.

6. The water heater according to claim 2, further comprising: a reporting part, reporting a result of any of the determinations.

7. The water heater according to claim 5, wherein the reporting part comprises: a display device or a speaker, provided in the water heater; ora remote controller capable of wireless communication with the water heater, or a transmitter transmitting a signal indicating a result of the reporting to an information communication terminal capable of wireless communication with the water heater.

8. The water heater according to claim 6, wherein the reporting part comprises: a display device or a speaker, provided in the water heater; ora remote controller capable of wireless communication with the water heater, or a transmitter transmitting a signal indicating a result of the reporting to an information communication terminal capable of wireless communication with the water heater.