JP3869771B2 - Water heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention is provided with a bypass pipe that branches from the water supply pipe and bypasses the heat exchanger and joins the hot water supply pipe in order to alleviate the post-boiling after the hot water supply is stopped and suppress the hot water temperature overshoot at the start of reheating. It relates to a water heater.
[0002]
[Prior art]
Conventionally, in this type, as disclosed in, for example, Japanese Patent Laid-Open No. 2000-320894, a bypass opening / closing valve is provided in a bypass pipe that bypasses the heat exchanger, and the hot water temperature is predetermined after the hot water supply is stopped. By rising above the temperature, this bypass on-off valve was opened to prevent burns with hot water at the start of hot water supply.
[0003]
[Problems to be solved by the invention]
By the way, with this conventional type, the bypass on-off valve is opened when the hot water temperature in the hot water pipe is higher than a predetermined temperature regardless of whether the hot water supply is started or stopped, so if the burner is a preheat vaporization type, the burner is vaporized in advance. There is a standby state that preheats to a possible temperature. At this time, the heat exchanger is also heated by this preheating, and the hot water temperature rises above the specified temperature, so that the bypass on-off valve opens even when hot water is stopped. The on-off valve generated heat in the open state of time, and the durability of the peripheral parts and the on-off valve itself were problematic.
[0004]
[Means for Solving the Problems]
This invention pays attention to this point and solves the above-mentioned drawbacks. In particular, the present invention comprises a water supply pipe, a heat exchanger provided downstream of the water supply pipe, and a vaporization heater for heating the heat exchanger. A premixed burner, a hot water supply pipe provided downstream of the heat exchanger, a bypass pipe branched from the water supply pipe and bypassing the heat exchanger to join the hot water pipe, And a standby circuit for holding the premixed burner in a standby state at a vaporizable temperature for a certain period of time. The bypass on-off valve is opened when the flow rate sensor provided in the hot water supply pipe detects a predetermined flow rate during standby, and the hot water thermistor is at a predetermined temperature not lower than a predetermined temperature determined by the hot water supply set temperature. Closing by continuing the time It is intended.
[0005]
As a result, the bypass open / close valve operates only during hot water supply with hot water flow, and even when the residual oil in the heat exchanger is heated to high temperature due to preheating during standby, the bypass open / close valve is opened at the start of hot water supply. Since the valve is opened and water is mixed in, the temperature drops, the hot water is supplied without fear of burns, and the bypass on / off valve is closed because all the remaining hot water in the heat exchanger flows out. Undershoot can be surely prevented, and has no influence on the durability of the surrounding parts and the on-off valve itself, and can be used for a long time.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Next, a water heater according to the present invention will be described based on one embodiment shown in the drawings.
A fin-and-tube heat exchanger 1 includes a water supply pipe 2 connected to a water pipe on the upstream side of the heat exchanger 1, and a hot water pipe having a hot water tap 3 at the downstream side. 4 is provided.
[0007]
Reference numeral 5 denotes a bypass pipe branched from the water supply pipe 2 and connected to the hot water supply pipe 4 by bypassing the heat exchanger 1, and a bypass opening / closing valve 6 comprising a normally closed electromagnetic valve is provided in the middle of the bypass pipe 5.
[0008]
Reference numeral 7 denotes a water supply thermistor provided upstream of the branch point of the bypass pipe 5 of the water supply pipe 2, which detects the water supply temperature as needed and is provided with a flow sensor 8 provided on the heat exchanger 1 side. A flow rate Q of water flowing into the exchanger 1 is detected, and 9 is a hot water thermistor provided on the downstream side of the junction of the bypass pipe 5 of the hot water supply pipe 4. This is to detect the hot water temperature after water mixing or the hot water temperature at which no water is mixed when the bypass opening / closing valve 6 is closed.
[0009]
A premixing burner 10 heats water through the heat exchanger 1, and the amount of heating is the temperature setting means 11 for setting a desired hot water supply temperature T, the water supply thermistor 7, the flow rate sensor 8, and the hot water supply heater. With the signal of the mister 9 as an input, it is controlled by a controller 12 constituted by a microcomputer so that the hot water supply set temperature T and the hot water temperature t detected by the hot water supply thermistor 9 coincide.
[0010]
A standby circuit 13 holds the premixed burner 10 in a standby state at a vaporizable temperature for a predetermined time scheduled for hot water supply, and a vaporization heater provided in a vaporizer (not shown) of the premixed burner 10. -Energization of the heater 14 is controlled by the temperature detected by the temperature sensor 15 and is kept at a vaporizable temperature for a preset time so that hot water supply can be started immediately.
[0011]
Further, the controller 12 opens the bypass on-off valve 6 and burns the premixed burner 10 when the hot-water tap 3 is opened and the flow rate sensor 8 detects 2.0 L / min or more during standby. The water is mixed at the same time as the hot water supply is started, and when the hot water supply set temperature T is 55 degrees C or higher, 13 degrees C is added, and when the hot water set temperature T is less than 55 degrees C, 10 degrees C is added. The hot water thermistor 9 detects the temperature below the predetermined time 0 when the integrated flow rate from the start of hot water supply is 0.9L or more, and continuously detects the temperature for less than 0.9L for 1 to 3 seconds. The bypass on-off valve 6 is closed.
[0012]
Next, the operation of this embodiment will be described with reference to the flowchart of FIG.
When the standby mode in which the premix burner 10 is preheated is started and the hot-water tap 3 is opened and the water from the water pipe is circulated through the water inlet pipe 2, step 1 (hereinafter abbreviated as S1). When it is detected that the flow rate detected by the flow rate sensor 7 is at least the minimum operating flow rate of 2.0 L / min, the premix burner 10 is turned on and the bypass opening / closing valve 6 is opened in S2.
[0013]
As a result, even if the remaining hot water in the heat exchanger 1 is heated due to preheating in the standby mode, the temperature of the heat exchanger 1 is warmed up, and the risk of being burned due to water contamination from the bypass pipe 5 is ensured. Therefore, it can be used with confidence at all times.
[0014]
Next, in S3, it is determined whether or not the hot water detection temperature by the hot water thermistor 9 is equal to or lower than a predetermined temperature of hot water set temperature determined by the hot water set temperature + alpha temperature, and in YES, the process proceeds to S4 and the integrated flow rate from the start of hot water supply is 0. If YES, the process proceeds to S5, where it is determined whether detection below the predetermined temperature has continued for a predetermined time or more. If YES, the process proceeds to S6 where the bypass on-off valve 6 is closed. If NO is 9L or more, the process immediately proceeds to S6.
[0015]
Therefore, since all the residual oil whose temperature has risen in the heat exchanger 1 is discharged as hot water supply, the bypass on / off valve 6 is closed, so that overshoot and undershoot due to hot water supply during standby can be reliably prevented, Good hot water is always provided.
[0016]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent the risk of burns due to the start of hot water supply during standby, and always be used with peace of mind. There is no fear of adversely affecting the durability, it can be used for a long period of time, and overshooting and undershooting due to hot water supply during standby are reliably prevented, and good hot water supply is always performed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.
FIG. 2 is a flowchart of one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Water supply pipe 4 Hot water supply pipe 5 Bypass pipe 6 Bypass on-off valve 8 Flow rate sensor 9 Hot water thermistor 10 Premixing burner 11 Temperature setting means 12 Controller 13 Standby circuit 14 Vaporization heater

Claims (1)

    A water supply pipe, a heat exchanger provided downstream of the water supply pipe, a premixed burner provided with a vaporization heater for heating the heat exchanger, and a hot water supply pipe provided downstream of the heat exchanger A bypass pipe branched from the water supply pipe and bypassing the heat exchanger to join the hot water supply pipe, a bypass on-off valve provided in the middle of the bypass pipe, and a temperature setting means for setting a desired hot water supply temperature And a standby circuit for holding the premixed burner in a standby state at a vaporizable temperature for a certain period of time, wherein the bypass on-off valve is in standby and a flow rate sensor provided in the hot water supply pipe is predetermined. A hot water heater, which is opened by detecting a flow rate, and is closed when a hot water thermistor continues a predetermined temperature not lower than a predetermined temperature determined by the hot water set temperature for a predetermined time.

Images