Patent Application
20070257122
With reference to
In a gas supply passage 8 for the burner 3, a main valve 9, a proportional valve 10, and a plurality of switch valves 11 for switching the number of unit burners 3a in combustion are provided. The main valve 9 is opened and an ignitor outside the figure is operated to ignite the burner 3. After the ignition, the proportional valve 10 and the switch valves 11 control a combustion amount of the burner 3.
Combustion exhaust gas of the burner 3 passes through the heat exchanger 4, and is then discharged to the outdoors from an upper end of the housing 2 through an exhaust gas cylinder 12. An air supply cylinder 13 surrounding the exhaust gas cylinder 12 is provided. A suction duct 15 connected to a suction side of an air supply fan 14 provided in the water heater 1 is connected to the air supply cylinder 13. The air supply fan 14 is operated to supply outside air through the air supply cylinder 13, the suction duct 15, and the air supply fan 14 into the housing 2 as combustion air.
The water supply channel 5 and the hot water delivering channel 6 are connected via a bypass channel 16 parallel to the heat exchanger 4. In the water supply channel 5, a flow rate sensor 17 and a flow rate control valve 18 are provided upstream of a branch portion of the bypass channel 16. Further, a supplied water temperature sensor 19 as supplied water temperature detection means for detecting a temperature of water supplied to the heat exchanger 4 is provided downstream of the branch portion of the bypass channel 16. In the hot water delivering channel 6, a first hot water delivering temperature sensor 20 as delivered hot water temperature detection means for detecting a temperature of hot water fed from the heat exchanger 4 is provided upstream of a converging portion of the bypass channel 16, and a second hot water delivering temperature sensor 21 is provided downstream of the converging portion of the bypass channel 16. A bypass flow rate control valve 22 is also provided in the bypass channel 16.
Detection signals from the flow rate sensor 17, the supplied water temperature sensor 19, the first hot water delivering temperature sensor 20, and the second hot water delivering temperature sensor 21 are input to a controller 23 provided in the water heater 1. With reference to
In the embodiment, a downstream end of the hot water delivering channel 6 is connected to a portion of the water supply channel 5 upstream of the flow rate sensor 17 and the flow rate control valve 18. A circulating pump 25 that returns hot water fed from the heat exchanger 4 to the hot water delivering channel 6 to the heat exchanger 4 through the water supply channel 5 is provided in the hot water delivering channel 6. The circulating pump 25 is always driven. Thus, water is always supplied to the heat exchanger 4 even when the hot water delivering tap 7 is closed to stop delivery of hot water. The burner 3 is subjected to combustion when the detection temperature from the second hot water delivering temperature sensor 21 reaches less than a predetermined heat insulating hot water temperature set according to the set hot water temperature, and the temperature of the circulated hot water is maintained at the heat insulating hot water temperature. Thus, hot water at an appropriate temperature is delivered immediately after opening of the hot water delivering tap 7, thereby preventing cold water from flowing out immediately after the opening of the hot water delivering tap 7 to cause discomfort to a user.
In areas with high water hardness, CaCO3 or MgCO3 contained in water is deposited in the heat absorbing pipe 4b of the heat exchanger 4, and a deposit easily adheres to an inner surface of the heat absorbing pipe 4b. Adhesion of the deposit reduces heat exchange efficiency of the heat exchanger 4. This makes it difficult for combustion heat of the burner 3 to be absorbed by water, thereby increasing a temperature of the heat exchanger 4 itself. Repeating combustion in this state causes heat damage to the heat exchanger 4 and thus causes leakage. In the embodiment, the diagnosis control portion 232 of the controller 23 performs diagnosis control so that an abnormality of the heat exchanger 4 can be identified at early stages when it occurs, such as the adhesion of the deposit to the inner surface of the heat absorbing pipe 4b. The diagnosis control portion 232 comprises a condition determination processing portion 233 and a diagnosis processing portion 234 configured by Steps S2 and S3 described later. The diagnosis processing portion 234 comprises a stop processing portion 235 configured by Step S4 described later, a display processing portion 236 configured by Step S5 described later, and an abnormality determination processing portion 237 configured by Steps S6 to S14 described later.
Details of the diagnosis control are as shown in
In Step S2, it is determined whether the hot water delivering tap 7 is closed based on the detection temperature Tin from the supplied water temperature sensor 19. When the hot water delivering tap 7 is opened, running water in an amount corresponding to an amount of hot water delivered from the hot water delivering tap 7 flows in from an upstream portion of the water supply channel 5 (a portion of the water supply channel 5 upstream of a connection of a downstream end of the hot water delivering channel 6). Thus, the detection temperature Tin from the supplied water temperature sensor 19 becomes much lower than the heat insulating hot water temperature, and Tin becomes lower than YTin. On the other hand, when the hot water delivering tap 7 is closed, the hot water is circulated in a closed loop extending from the heat exchanger 4 through the hot water delivering channel 6 and the water supply channel 5 and returning to the heat exchanger 4, and no running water flows in from the upstream portion of the water supply channel 5. Thus, the detection temperature Tin from the supplied water temperature sensor 19 is maintained at a temperature substantially equal to the heat insulating hot water temperature, and Tin becomes equal to or higher than YTin.
The determination processings in Steps S2 and S3 are repeated until both the determination results of Steps S2 and S3 become YES. When both the determination results of the Steps S2 and S3 become YES, that is, when Tin is equal to or higher than YTin and the burner 3 is subjected to combustion, the process proceeds to Step S4 and thereafter, and a diagnosis processing is performed.
In the diagnosis processing, first in Step S4, the flow rate control valve 18 is closed. Further, in Step S5, a signal is sent to the remote controller 24, and a “check display” indicating that the diagnosis is being performed is lit in a display portion of the remote controller 24. When the flow rate control valve 18 is closed, the supply of water to the heat exchanger 4 is stopped even if the circulating pump 25 is operated. Then, the detection flow rate from the flow rate sensor 17 reaches a minimum operative flow rate or less, and the combustion of the burner 3 is stopped.
Next, in Step S6, it is confirmed whether the flow rate control valve 18 is actually closed based on a signal from a sensor provided in the flow rate control valve 18. When the closing of the flow rate control valve 18 is confirmed, the process proceeds to Step S7, an amount of increase ΔTout of a detection temperature Tout from the first hot water delivering temperature sensor 20 from the time of confirmation of the closing of the flow rate control valve 18, and it is determined whether the amount of increase ΔTout reaches a predetermined threshold value YΔTout or more. When ΔTout is smaller than YΔTout, it is determined in Step S8 whether a predetermined time (for example, 30 seconds) has passed from the time of confirmation of the closing of the flow rate control valve 18, and the process returns to Step S7 until the predetermined time passes. When the predetermined time passes with ΔTout being smaller than YΔTout, the absence of an abnormality is determined, a signal is sent to the remote controller 24 in Step S15 to extinguish the “check display”. Then, in Step S16, the flow rate control valve 18 is opened (in a normal control state) again, and one diagnosis processing is finished.
If a deposit adheres to the inner surface of the heat absorbing pipe 4b to reduce heat exchange efficiency of the heat exchanger 4 and thus increase the temperature of the heat exchanger 4 itself, the amount of increase ΔTout of the detection temperature Tout from the first hot water delivering temperature sensor is increased by a delayed water temperature increase after a stop of the supply of water. Thus, if the threshold value YΔTout is set to a value slightly larger than the amount of increase ΔTout when the heat exchanger 4 is normal, it can be determined that the state where ΔTout is equal to or larger than YΔTout is an abnormal state where the deposit adheres to the inner surface of the heat absorbing pipe 4b.
A relatively large amount of delayed water temperature increase is obtained only by combustion of the burner 3 for a certain time or longer to uniformly heat the heat exchanger 4 even if the deposit adheres to the inner surface of the heat absorbing pipe 4b, and sometimes ΔTout becomes smaller than YΔTout. Thus, it is preferably determined YES in Step S3 to start the diagnosis processing only when the burner 3 is subjected to combustion for a predetermined time (for example, one minute) or longer.
The amount of increase ΔTout also varies according to the combustion amount of the burner 3 immediately before the stop of the supply of water. If the threshold value YΔTout is fixed, with a large combustion amount of the burner 3 immediately before the stop of the supply of water, ΔTout may become equal to or larger than YΔTout and the presence of an abnormality may be falsely determined though the heat exchanger 4 is normal. If the threshold value YΔTout is set to a relatively high value in view of this, with a small combustion amount of the burner 3, ΔTout may become smaller than YΔTout and the absence of an abnormality may be falsely determined though an abnormality of the heat exchanger 4 occurs. Thus, a data table indicating a relationship between the combustion amount and the threshold value YΔTout as shown in
However, even when ΔTout becomes equal to or larger than YΔTout only once, the possibility of false determination remains. In the embodiment, when it is determined in Step S7 that ΔTout is equal to or larger than YΔTout, one is added to a count value C in Step S9, and then it is determined in Step S10 whether the count value C reaches three. Until the count value C reaches three, the flow rate control valve 18 is opened again in Step S11, the burner 3 is subjected to combustion for a predetermined time (for example, 15 seconds) in Step S12, the flow rate control valve 18 is closed again in Step S13, and the process returns to Step S6, which are repeated. When the count value reaches three, that is, when it is determined three times continuously that ΔTout is equal to or larger than YΔTout, the presence of an abnormality of the heat exchanger 4 is determined, a signal is sent to the remote controller 24 in Step S14, and an abnormality indication that indicates the occurrence of the abnormality is lit in the display portion or the remote controller 24. Then, after the processing in Step S14, the above described processings in S15 and S16 are performed, and one diagnosis processing is finished. The abnormality indication may be not extinguished after the diagnosis processing, and may encourage a user to take an appropriate measure such as cleaning of the heat exchanger 4.
If the diagnosis processing is started while the hot water delivering tap 7 is opened to deliver hot water, the closing of the flow rate control valve 18 in Step S4 stops the delivery of hot water from the hot water delivering tap 7, which imposes an inconvenience on the user. In the embodiment, however, it is determined in Step S2 that Tin is smaller than YTin during the delivery of hot water, thus the process does not proceed to Step S4, and the delivery of hot water is not stopped in midstream. Also, no water is delivered during the diagnosis processing even if the hot water delivering tap 7 is opened, which may be construed as a failure by the user. In the embodiment, however, the “check indication” is lit during the diagnosis processing, thereby preventing the user from misconstruing the situation as a failure.
When the hot water delivering tap 7 is opened to deliver hot water, running water flows in from the upstream portion of the water supply channel 5 (the portion of the water supply channel 5 upstream of the connection of the downstream end of the hot water delivering channel 6), while when the hot water delivering tap is closed, the inflow of the running water from the upstream portion of the water supply channel 5 is stopped. Thus, it can be considered that the flow rate sensor 17 provided in a downstream portion of the water supply channel 5 (a portion of the water supply channel downstream of the connection of the downstream end of the hot water delivering channel 6) is placed in the upstream portion of the water supply channel 5, and whether the hot water delivering tap 7 is closed is determined based on the signal from the flow rate sensor 17. The flow rate sensor 17, however, needs to be provided in the downstream portion of the water supply channel 5 for fail safe in the event of failure of the circulating pump 25. Specifically, when the supply of water to the heat exchanger 4 is stopped by the failure of the circulating pump 25 at the stop of the delivery of hot water, the stop by the failure needs to be detected to prohibit the combustion of the burner 3. Providing the flow rate sensor 17 in the upstream portion of the water supply channel 5 prevents detection of the stop of the supply of water by the failure of the circulating pump 25. Thus, the flow rate sensor 17 has to be provided in the downstream portion of the water supply channel 5. Thus, for directly detecting the supply of running water from the upstream portion of the water supply channel 5, a water flow switch needs to be further provided in the upstream portion of the water supply channel 5, which increases costs. In the embodiment, the existing supplied water temperature sensor 19 can be used to determine whether the hot water delivering tap 7 is closed, which is cost-effective.
In the embodiment, the flow rate control valve 18 is closed in Step S4 to stop the supply of water to the heat exchanger 4, but it can be considered that the circulating pump 25 is stopped to stop the supply of water. However, the circulation type hot water supply device that always drives the circulation pump 25 comprises no control switch for controlling the circulating pump 25 with the controller 23 in the water heater 1. Thus, in order to stop the circulation pump 25 at the start of the diagnosis, the control switch needs to be added, which increases costs. In the embodiment, no control switch needs to be added, which is cost-effective.
The embodiment of the present invention has been described with reference to the drawings, but the present invention is not limited to this. For example, in the embodiment, the supplied water temperature sensor 19 is provided as supplied water temperature detection means for detecting the temperature of the water supplied to the heat exchanger 4, but the supplied water temperature detection means may be configured by the controller 23 in a software manner. Specifically, the supplied water temperature can be calculated by a predetermined arithmetic expression from the combustion amount of the burner 3, the water supply amount detected by the flow rate sensor 17, and the delivered hot water temperature detected by the delivered hot water temperature sensor 21. The calculation is performed by the controller 23 to calculate the supplied water temperature, which allows the supplied water temperature sensor 19 to be omitted.
The water heater 1 in the embodiment is of a bypass mixing type having the bypass channel 16, but a water heater may be used in which the entire amount of water supplied to the water supply channel 5 is supplied to the heat exchanger 4 without providing the bypass channel 16. In this case, the combustion amount of the burner 3 is controlled so that the detection temperature from the delivered hot water temperature sensor 20 reaches the set hot water temperature, which eliminates the need for the second hot water delivering temperature sensor 21.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-085886 | Mar 2006 | JP | national |
