AU2016266056B2 - Water Heater - Google Patents

Abstract

P-16022-AU ABSTRACT A controller (13) starts a timer of 30 seconds in S5 after detecting a flame of a burner (4) in S3, and in S6 and S8, determines whether or not a water temperature at an outlet detected by an outlet temperature thermistor (21) is less than 35°C and a discharging hot water temperature detected by a hot water discharging thermistor (22) is less than 35°C during counting of the timer. In the case where 30 seconds have passed while detected temperatures of both thermistors (21, 22) stay less than 350C, the controller (13) controls a bypass servo (20) to increase a bypass rate in S9. This decreases a quantity of water to the heat exchanger (5) to raise temperature of a water pipe. Then, a bimetal switch (25) reaches an operating temperature to operate the boiling prevention device (24), and burning of the burner (4) is forcibly stopped. 2/2 FIG.2 (Open hot water tap S1 Ignition water quantity? NO YES Prepurge S2 Open each valve Ignitor on S3 Is flame detected? NO 0 YES Stop operation S4 Start timer S5 Is water temperature at outlet S6 less than 35°C and discharging hot NO water temperature less than 35°C? Normal S7 YES operation S8 NO Have 30 seconds passed since flame confirmation? YES Bypass raeu S9

Description

2/2

FIG.2 (Open hot water tap

S1 Ignition water quantity? NO

YES

Prepurge S2 Open each valve Ignitor on

S3 Is flame detected? 0 NO

YES Stop operation S4

Start timer S5

Is water temperature at outlet S6 less than 35°C and discharging hot NO water temperature less than 35°C? Normal S7

YES operation

S8 NO Have 30 seconds passed since flame confirmation?

YES

Bypass raeu S9

AUSTRALIA

PATENTS ACT 1990

COMPLETE SPECIFICATION FORASTANDARD PATENT

Name of Applicant: Paloma Co., Ltd

Actual Inventor: Yusuke Kakizaki

Address for Service is:

SHELSTON IP PTY LTD

60 Margaret Street Telephone No: (02) 9777 1111

SYDNEY NSW 2000 Facsimile No. (02) 9241 4666

CCN: 3710000352

Attorney Code: SW

Invention Title: Water Heater

The following statement is a full description of this invention, including the best method of performing

it known to us:

File: 94481AUP00

P-16022-AU

WATER HEATER

Field of the Invention

[0001] The present invention relates to a water heater that includes a heat exchanger to

which a water inlet pipe and a hot water discharging pipe are coupled, and a burner for

heating water passing through the heat exchanger, and includes a bypass pipe for

bypassing the heat exchanger between the water inlet pipe and the hot water discharging

pipe.

Background of the Invention

[0002] As disclosed in Japanese Unexamined Patent Application Publication No.

2014-25664, there has been known a water heater that includes a heat exchanger where a

burner heats water passing through the inside, a water supply pipe coupled to an upstream

side of the heat exchanger, a hot water discharging pipe coupled to a downstream side of

the heat exchanger, and a bypass pipe for bypassing the heat exchanger coupled to

between the water supply pipe and the hot water discharging pipe.

[0003] The water heater is configured to include an outlet temperature thermistor for

detecting a water temperature at an outlet from the heat exchanger in the proximity of a

coupling portion to the heat exchanger on the hot water discharging pipe. The water

temperature at the outlet is monitored by a controller. When the water temperature at the

outlet rises to equal to ormore than a predetermined temperature, the controller decreases

a degree of opening of a bypass valve for adjusting a quantity of water to a bypass pipe, so

P-16022-AU

that the quantity of water to the heat exchanger is relatively increased. In the above

configuration, the heat exchanger is prevented from overheating.

[0004] On the other hand, there has been a large-sized water heater that has a high

temperature water discharging function for discharging hot water with a high temperature

(such as 85C). In this water heater, when a user chooses the high temperature water

discharging function, a controller closes a bypass valve to close a bypass pipe, and

controls so as to heat all of water of a small amount by a heat exchanger.

Summary of the Invention

[0005] Now, in the above-described water heater, if a breakdown occurs in the outlet

temperature thermistor, hot water with a temperature higher than a detected temperature

flows into the hot water discharging pipe and a heat load is applied to a sealing member

such as an0-ring disposed on a pipe coupling portion. As a result, deterioration is

possibly accelerated. In the water heater with the high temperature water discharging

function, because of the breakdown of the outlet temperature thermistor, the hot water with

a high temperature more than the temperature intended by the user may be discharged.

[0006] On the other hand, some water heater include a boiling prevention device

constituted of a heat sensitive switch and an electric circuit on the downstream side of the

water passing portion of the heat exchanger, in consideration of a case where such as

heating without water occurs in the pipe of the heat exchanger. The heat sensitive switch

is such as a bimetal switch configured to operate at a predetermined temperature. The

electric circuit, for example, cuts off a part of the circuit to automatically stop burning of the

burner when the heat sensitive switch is operated.

P-16022-AU

[0007] Therefore, there is a possibility to use the boiling prevention device to operate for

stopping the discharge of the hot water with the high temperature in the case of the

breakdown of the outlet temperature thermistor.

[0008] However, the heat sensitive switch is susceptible to such as heat from the heat

exchanger and the burner because the heat sensitive switch is secured to the pipe as the

water passing portion of the heat exchanger via a metallic mounting member. Then, a

difference occurs between an actual temperature of passing water and a temperature on a

mounting portion of the heat sensitive switch. Accordingly, to prevent the water heater

from unexpectedly stopping the operation by a malfunction, an operation temperature of

the heat sensitive switch is required to be set at a higher temperature with a sufficient

margin with respect to the boiling temperature.

[0009] In the above case, when the breakdown of theoutlet temperature thermistor is

dealt with using the boiling prevention device, it takes along time from the discharge of the

hot water with the abnormally high temperature to the operation of the heat sensitive switch

for stopping the burning of the burner. As a result, it fails to decrease the heat load applied

on the sealing member, which causes the hot water with the high temperature to be

discharged for a relatively long time. However, if the operation temperature of the heat

sensitive switch is set lower, when the high temperature water discharging function is

selected, the heat sensitive switch operates to stop the burning even though the hot water

is discharged at a normal temperature in the function. Then, usability is decreased.

[0010] Therefore, it is an object of the present invention to provide a water heater that is

configured to deal with a breakdown of an outlet temperature thermistor by a boiling

prevention device including a heat sensitive switch such as a bimetal switch, and

P-16022-AU

configured, in such case, to stop burning of a burner early only in the case where a heat

exchanger discharges hot water with an abnormally high temperature so that a heat load

on such as a sealingmember is decreased and usability is maintained.

[0011] According to a first aspect of the invention, in order to achieve the

above-described object, a water heater includes a heat exchanger, a water inlet pipe, a hot

water discharging pipe, a bypass pipe, a bypass amount adjusting unit, an outlet

temperature thermistor, a controller, and a combustion stop unit. The heat exchanger

includes a water passing portion and is heated by a burner. The water inlet pipe is

coupled to an upstream side end portion of the water passing portion. The hot water

discharging pipe is coupled to a downstream side end portion of the water passing portion.

The bypass pipe is coupled to between the water inlet pipe and the hot water discharging

pipe so as to bypass the heat exchanger. The bypass amount adjusting unit is configured

to adjust a quantity of water to the bypass pipe. The outlet temperature thermistor is

disposed on an upstream side of a coupling portion of the bypass pipe to the hot water

discharging pipe. The outlet temperature thermistor is configured to detect a water

temperature at an outlet from the water passing portion. The controller is configured to

monitor a detected temperature of the outlet temperature thermistor to detect an

abnormality of the outlet temperature thermistor. The controller is configured to control the

bypass amount adjusting unit. The combustion stop unit includes a heat sensitive switch

configured to operate at a predetermined temperature. The heat sensitive switch is

disposed on the water passing portion. The combustion stop unit is configured to stop

burning of the burner when the heat sensitive switch is operated. When the abnormalityof

the outlet temperature thermistor is detected, the controller controls the bypass amount

adjusting unit to increase the quantity of water to the bypass pipe and decrease the quantity

P-16022-AU

of water to the heat exchanger so that a temperature of the water passing portion is raised

until the heat sensitive switch operates.

[0012] According to a second aspect of the invention, the first aspect further includes a

hot water discharging thermistor configured to detect a discharging hot water temperature

after mixed with water from the bypass pipe. The hot water discharging thermistor is

disposed on a downstream side of a coupling portion of the bypass pipe to the hot water

discharging pipe. The controller monitors a detected temperature of the hot water

discharging thermistor. When both the detected temperature of the outlet temperature

thermistor and the detected temperature of the hot water discharging thermistor do not

reach equal to or more than a predetermined determination temperature before alapse of a

predetermined time period for an ignition confirmation of the burner, the controller

determines that the abnormality has occurred on the outlet temperature thermistor and the

hot water discharging thermistor.

Effect of the Invention

[0013] With the water heater according to the first aspect of the invention, when the

abnormality of the outlet temperature thermistor is detected, the controller controls the

bypass amount adjusting unit to increase the the quantity of water to the bypass pipe and

decrease the the quantity of water to the heat exchanger so that the temperature of the

water passing portion is raised until the heat sensitive switch operates. In the above

configuration, burning of the burner is stopped early only in the case where the heat

exchanger discharges the hot water with the abnormally high temperature even if the

breakdown of the outlet temperature thermistor is dealt with the combustion stop unit with

the heat sensitive switch. Therefore, a discharging period of the hot water with the

P-16022-AU

abnormally high temperature is reduced to decrease the heat load applied on the sealing

member, and an unexpected stop of the burning of the burner is prevented in the case

where the high temperature water discharging function is included. Accordingly, usability

is maintained. Furthermore, since the existing thermistors and the combustion stop unit

are utilized, cost increase is suppressed.

[0014] With the water heater according to the second aspect of the invention, in addition

to the effect of the first aspect, the hot water discharging thermistor is allowed to be used to

perform the strict abnormality determination. Therefore, the abnormality determination is

performed at an early timing to reduce the possibility of decreasing the usability.

Brief description of the Drawings

[0015] Fig. I is a schematic diagram of a water heater.

[0016] Fig. 2 is a flowchart of an abnormality determination control of a thermistor.

Description of preferred embodiments

[0017] The following describes an embodiment of the present invention based on the

drawings.

[0018] Fig. I is a schematic diagram illustrating an exemplary water heater. A water

heater 1 includes a combustion chamber 2 with an air supply fan 3 in the apparatus main

body. The combustion chamber 2 internally includes a plurality of burners 4, 4 - - (here,

three units) and a heat exchanger 5. The burners 4, 4 - - burns a mixed gas of a fuel gas

and a primary air form the air supply fan 3. The heat exchanger 5 is heated by burning of

P-16022-AU

the burners 4, 4 and has a water pipe as a water passing portion where the upstream

side end portion is coupled to a water supply pipe (water inlet pipe) 6 and the downstream

side end portion is coupled to a hot water discharging pipe 7. The heat exchanger 5 is

constituted of a primary heat exchanger 5A and a secondary heat exchanger 5B. The

primary heat exchanger 5A is coupled to the hot water discharging pipe 7 and recovers the

sensible heat of the exhaust air of the burners 4, 4 - . The secondary heat exchanger 5B

is coupled to the water supply pipe 6 and recovers the latent heat of the exhaust air. A

drain generated in the secondary heat exchanger 5B is neutralized by a neutralizer 8 to be

discharged outside the apparatus.

[0019] Each burner 4 is supplied with the fuel gas through a gas pipe 9 that includes a

main solenoid valve 10 and a gas proportional valve 11. The gas pipe 9 is branched to

branch pipes 9a, 9a - - toward each burner 4. The branch pipes 9a, 9a - -respectively

include switching solenoid valves 12, 12 - . Each valve is configured to be controlled by a

controller 13. An ignition electrode 14 is coupled to an ignitor (not illustrated). A flame

rod 15 is disposed for detecting a flame.

[0020] Furthermore, between the water supply pipe 6 and the hot water discharging

pipe 7, a bypass pipe 16 for bypassing the heat exchanger 5 is coupled. The water supply

pipe 6 includes a water sensor 17 that detects a quantity of water flowing through the water

supply pipe 6, a water servo 18 that controls the quantity of water of the water supply pipe

6, and a water inlet thermistor 19 that detects a temperature of the inflow water, on the

upstream side of the coupling position to the bypass pipe 16. The bypass pipe 16 includes

a bypass servo 20 as a bypass amount adjusting unit for controlling the quantity of water to

P-16022-AU

the bypass pipe 16. Each of the water sensor 17, the water servo 18, the water inlet

thermistor 19, and the bypass servo 20 is electrically coupled to the controller 13.

[0021] On the other hand, the hot water discharging pipe 7 includes an outlet

temperature thermistor 21 and a hot water discharging thermistor 22. The outlet

temperature thermistor 21 detects the temperature of the outlet from the heat exchanger 5

near the coupling portion to the heat exchanger 5. The hot water discharging thermistor

22 detects the temperature after mixed with the water on the downstream side of the

coupling position to the bypass pipe 16. An outside air temperature thermistor 23 detects

the external temperature. Each of the outlet temperature thermistor 21, the hot water

discharging thermistor 22, and the outside air temperature thermistor 23 is electrically

coupled to the controller 13.

[0022] Then, a boiling prevention device 24 is a combustion stop unit secured to the

water pipe of the heat exchanger 5 on the outside of the can body of the heat exchanger 5

via a mounting member. The boiling prevention device 24 is constituted of a bimetal

switch 25 as a heat sensitive switch configured to operate at a predetermined temperature

and a circuit board 26 that includes an electric circuit to automatically stop the burning of the

burner 4 by such as cutting off of a part of the circuit when the bimetal switch 25 operates.

Therefore, in a case where such as heating without water occurs in the pipe of the heat

exchanger 5 and the temperature of the water pipe is raised high (such as 90°C), the

bimetal switch 25 operates to cause the electric circuit on the circuit board 26 to forcibly

stop the burning of the burner4. A remote controller 27 is coupled to the controller 13 to

make the setting of such as a temperature of the discharging hot water.

P-16022-AU

[0023] The following describes an abnormality determination control of the thermistor by

the controller 13 in the water heater 1 configured as described above based on a flowchart

in Fig. 2.

[0024] First, a hot water tap (not illustrated) disposed on a down stream end of the hot

water discharging pipe 7 is opened to cause the water to flow through the apparatus.

Then, in S1, a signal obtained from the water sensor 17 is used to confirm whether or not

the quantity of water flowing through inside the apparatus exceeds an ignition water

quantity. Here, when the quantity of water is confirmed to exceed the ignition water

quantity, in S2, the controller 13 rotates the air supply fan 3 to perform a prepurge, and

opens the main solenoid valve 10, the switching solenoid valve 12, and the gas

proportional valve 11 to supply the gas to the burner 4, while the controller 13 causes the

ignitor to operate the ignition control of the burner 4.

[0025] Next, in S3, the flame rod 15 detects the flame of the burner 4. Here, when the

flame is not detected, the controller 13 closes each valve to stop the operation in S4. On

the other hand, in S3, when the flame is detected, the controller 13 starts a timer of 30

seconds in S5.

[0026] Next, in S6, it is determined whether or not a water temperature at the outlet

detected by the outlet temperature thermistor 21 is less than 350 C as a determination

temperature, and a temperature of discharging hot water detected by the hot water

discharging thermistor 22 is less than 350C as the determination temperature. Here, if it is

NO, that is, at least one of the detected temperatures by the outlet temperature thermistor

21 and the hot water discharging thermistor 22 is equal to or more than 35°C, a normal

operation is performed in S7. This is a control of the temperature of the discharging hot

P-16022-AU

water where the controller 13 controls the degree of opening of the gas proportional valve

11 corresponding to the difference between the temperature of the discharging hot water

detected by the hot water discharging thermistor 22 and a set temperature set by the

remote controller 27 to continuously vary the gas quantity, so as to cause the temperature

of the discharging hot water to match the set temperature. The controller 13 varies the

rotation speed of the air supply fan 3 corresponding to the change of the gas quantity by the

control of the gas proportional valve 11 to control the ratio of the gas quantity and the air

quantity.

[0027] On the other hand, in the determination in S6, when the detected temperatures

of both thermistors 21 and 22 are less than 35°C, it is confirmed whether or not 30 seconds

have passed since the start of the timer after the detection of the flame, in S8. Here, if it is

before 30 seconds have passed, S6 is executed again to confirm the detected

temperatures of both thermistors 21 and 22. When any of or both detected temperatures

are equal to or more than 350C, the normal operation is performed in S7.

[0028] Then, if it is YES in S8, that is, if 30 seconds have passed while the detected

temperatures of both thermistors 21 and 22 stay less than 35°C, the controller 13

determines that a failure has occurred on both thermistors 21 and 22 and controls the

bypass servo 20 for increasing a bypass rate (such as 45%) of water, in S9. In the above

manner, the quantity of water to the heat exchanger 5 is decreased and the temperature of

the water pipe is raised. Then, the bimetal switch 25 reaches the operation temperature to

cause the bimetal switch 25 to be operated, and the boiling prevention device 24 operates

to forcibly stop the burning of the burner 4. While the illustration is omitted, a release

condition of the abnormality determination control here is not only the confirmation about

P-16022-AU

that the water temperature at the outlet and the temperature of the discharging hot water

are equal to or more than the determination temperature, but also the stop of use by the

user, for example, a power-off by the operation of the remote controller 27 and a closing of

the hot water tap, is included.

[0029] Thus, according to the above-described water heater 1, the controller 13 is

configured such that, when the abnormality is detected on the outlet temperature thermistor

21, the controller 13 controls the bypass servo 20 to increase the quantity of water to the

bypass pipe 16 and decrease the quantity of water to the heat exchanger 5 so as to raise

the temperature of the water pipe until the bimetal switch 25 operates. In the above

configuration, the burning of the burner 4 is stopped early only in the case where the heat

exchanger 5 discharges the hot water with the abnormally high temperature even if the

breakdown of the outlet temperature thermistor 21 is dealt with the boiling prevention

device 24 that has the bimetal switch 25. Therefore, the discharging period of the hot

water with the abnormally high temperature is reduced to decrease the heat load applied

on the sealing member, and an unexpected stop of the burning of the burner 4 is prevented

in the case where the high temperature water discharging function is included.

Accordingly, usability is maintained. Furthermore, since the existing thermistors 21 and

22 and the boiling prevention device 24 are utilized, cost increase is suppressed.

[0030] Especially, here, in the case where both the detected temperature of the outlet

temperature thermistor 21 and the detected temperature of the hot water discharging

thermistor 22 do not reach equal to or more than the predetermined determination

temperature (here, 35°C) before a lapse of the predetermined time period for the ignition

confirmation of the burner 4, the controller 13 determines that the abnormality has occurred

P-16022-AU

on the outlet temperature thermistor 21 and the hot water discharging thermistor 22.

Then, the controller 13 can also control the hot water discharging thermistor 22 to perform

the strict abnormality determination. As a result, the abnormality determination is

performed at an early timing to reduce the possibility of decreasing the usability.

[0031] The determination temperature of the thermistor abnormality is not limited to

350C, and may be changed as necessary. However, if the determination temperature is

too low, the abnormality cannot be detected, and if the determination temperature is too

high, an erroneous detection possibly occurs when the hot water is discharged at a low

temperature. Then, 350C is preferable.

[0032] The abnormality determination of the thermistors is not limited to the

above-described determination in S6. The determination may be performed under the

other condition, for example, a condition where it is determined whether or not the detected

temperature of the hot water discharging thermistor exceeds the detected temperature of

the outlet temperature thermistor by equal to or more than a predetermined temperature

(such as 10°C), and when the detected temperature of the hot water discharging thermistor

exceeds the detected temperature of the outlet temperature thermistor by equal to or more

than the predetermined temperature, it is determined to be the thermistor abnormality.

[0033] On the other hand, the timer for the abnormality determination also may be

increased and decreased to the time period other than 30 seconds. If the time period of

the timer is shortened, an early deal is possible.

[0034] The bypass rate when the thermistor abnormality is detected is also not limited to

45%, and may be configured to be higher than 45%.

P-16022-AU

[0035] Furthermore, the abnormality determination of the thermistors is performed

within the predetermined time period after the ignition confirmation of the burner in the

above-described embodiment. However, it is not limited to immediately after the ignition.

The abnormality determination may be continuously performed during the burning of the

burner by monitoring the detected temperature of the thermistors at regular time intervals.

[0036] Then, the abnormality determination is performed by monitoring the detected

temperatures of both thermistors of the outlet temperature thermistor and the hot water

discharging thermistor in the above-described embodiment. However, the abnormality

determination may be performed by monitoring only the detected temperature of the outlet

temperature thermistor.

[0037] Besides, in the above-described embodiment, the water heater includes the

secondary heat exchanger for recovering the latent heat. However, the present invention

is applicable to even the water heater that includes only the primary heat exchanger (main

heat exchanger) for recovering the sensible heat without the secondary heat exchanger.

[0038] The present invention can be applied to even the water heater with a bath where

the hot water discharging pipe is branched to be coupled to a bathtub, and a circulation

circuit of hot water is disposed between a bath heat exchanger and the bathtub.

[0039] In the claims which follow and in the preceding description of the invention,

except where the context requires otherwise due to express language or necessary

implication, the word "comprise" or variations such as"comprises" or "comprising" is used

in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude

the presence or addition of further features in various embodiments of the invention.

P-16022-AU

[0040] It is to be understood that, if any prior art publication is referred to herein, such

reference does not constitute an admission that the publication forms a part of the common

general knowledge in the art, in Australia or any other country.

Claims (2)

P-16022-AU CLAIMS:

1. A water heater comprising:

a heat exchanger that includes a water passing portion and is heated by a burner;

a water inlet pipe coupled to an upstream side end portion of the water passing

portion;

a hot water discharging pipe coupled to a downstream side end portion of the

water passing portion;

a bypass pipe coupled to between the water inlet pipe and the hot water

discharging pipe so as to bypass the heat exchanger;

a bypass amount adjusting unit configured to adjust a quantity of water to the

bypass pipe;

an outlet temperature thermistor disposed on an upstream side of a coupling

portion of the bypass pipe to the hot water discharging pipe, the outlet temperature

thermistor being configured to detect a water temperature at an outlet from the water

passing portion;

a controller configured to monitor a detected temperature of the outlet temperature

thermistor to detect an abnormality of the outlet temperature thermistor, the controller being

configured to control the bypass amount adjusting unit; and

a combustion stop unit that includes a heat sensitive switch configured to operate

at a predetermined temperature, the heat sensitive switch being disposed on the water

passing portion, and the combustion stop unit being configured to stop burning of the burner

upon the operation of the heat sensitive switch, wherein

when the abnormality of the outlet temperature thermistor is detected, the

controller controls the bypass amount adjusting unit to increase the quantity of water to the

P-16022-AU

bypass pipe and decrease a quantity of water to the heat exchanger so as to raise the

temperature of the water passing portion until the heat sensitive switch operates.

2. The water heater according to claim 1, further comprises

a hot water discharging thermistor configured to detect a discharging hot water

temperature after mixed with water from the bypass pipe, the hot water discharging

thermistor being disposed on a downstream side of the coupling portion of the bypass pipe

to the hot water discharging pipe, wherein

the controller monitors a detected temperature of the hot water discharging

thermistor, and

when both the detected temperature of the outlet temperature thermistor and the

detected temperature of the hot water discharging thermistor do not reach equal to or more

than a predetermined determination temperature before a lapse of a predetermined time

period for an ignition confirmation of the burner, the controller determines that the

abnormality has occurred on the outlet temperature thermistor and the hot water

discharging thermistor.