JPH03213953A - Freezing preventive mechanism of hot water feeder - Google Patents

Abstract

PURPOSE:To make a simple configuration of a freezing preventive mechanism by a method wherein a heating source for preventing a freezing action and a temperature sensor are arranged in a circulating passage and the heating source is turned on or off within a temperature range near a freezing temperature and a hot water feeding pump is turned on or off within a temperature range higher than the former temperature range. CONSTITUTION:During operation of a pump 7, as a sensor 11b detects that a hot water temperature is decreased down to a temperature T4 near a freezing temperature due to a reduction in surrounding air temperature, an electrical heater 13 at a heating part 14 acting also as a heater is operated to heat the circulating water. As a sensor 11a detects that the temperature becomes a temperature T2 slightly higher than T4, the heater 13 is turned off and operation of the pump 7 only is continued. Accordingly, temperatures at each of the positions in the circulation passage are made uniform under the continuous operation of the pump 7, resulting in that no local low temperature part is formed and then a freezing is prevented. The continuous operation of the pump 7 is turned off when the hot water temperature is higher than T2. Accordingly, it is not necessary to arrange a separate exclusive heater and a simple configuration can be assured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a freeze prevention mechanism for a water heater.

(Prior art) In a so-called single-pipe water heater, in which the piping from the heat exchange part of the water heater to the hot water supply part is a single pipe, even if the hot water tap in the hot water supply part is opened and hot water supply starts, it will not work for a while. There is a drawback that cold water comes out.In order to solve this problem, a circulation path is constructed between the heat exchanger and the hot water supply section, and when the hot water supply is stopped, the hot water in the circulation path is kept warm. A hot water supply apparatus has been proposed that performs the following: For example, as shown in FIG. A hot water return path 6b from the hot water supply section 5 to the upstream side of the heat exchanger 1 via the pump 7 is provided to constitute a circulation path, and a water supply path from the water supply section 8 to the upstream side of the heat exchanger 1. It has a configuration with 8.
A heating section 14 equipped with an electric heater 13 is provided in the hot water return path 6b. In this configuration, when hot water supply is stopped, the pump 7 is operated and the electric heater 13 is operated appropriately to perform a heat retention operation to keep the hot water in the circulation path at a predetermined temperature, and when hot water supply from the hot water supply unit 5 is started. Hot water at a predetermined temperature in the pipes is immediately used. In the above-described water heater, an electric heater 17 dedicated to anti-freezing is provided at a suitable location inside the water heater 2 in order to prevent the components from freezing when the heat-retaining operation is not performed in the winter.
A temperature switch 18 such as a bimetal switch is provided at an appropriate location in the heat exchanger 1, etc., and this temperature switch 18 is turned ON when the temperature is near the freezing temperature, for example, below 3±2.5°C.
It is set to turn off at temperatures above 5°C. However, when the temperature of the temperature switch 18 drops to the above-mentioned low temperature at night or early morning in winter and turns on, the control means 1
9 operates the electric heater 17 and the pump 7 to circulate the water heated by the electric heater 17 through the circulation path, and when the temperature of the temperature switch 18 reaches the high temperature or higher, it is turned off.
Freeze prevention operation is being carried out until .

(Problem to be Solved by the Invention) In the above-described anti-freezing mechanism, since the temperature switch 18 is not necessarily located at the lowest temperature, it is necessary to There is a risk that components in areas such as the mouth that are directly exposed to the outside air and cannot be adequately coated with heat insulating material may freeze. Since the antifreeze operation continues until the temperature rises, there is a problem that the operation rate of the electric heater 17 is high and heat loss is large.

The present invention aims to solve the above problems.

(Means for Solving the Problems) Means for solving the above-mentioned problems will be explained with reference to FIG. 1 corresponding to the embodiment. From the downstream side of the heat exchanger 1 to the hot water supply section 5
A hot water supply route 6a leading to the hot water supply section 5 and a hot water return route 6b leading from the hot water supply section 5 to the upstream side of the heat exchanger 1 via the pump 7 are provided to constitute a circulation route.
In a water heater equipped with a water supply path 9 that reaches the upstream side of
A heating source H for preventing freezing and a temperature sensor S for detecting the temperature of the water are provided in the circulation path, and the heating source H for preventing freezing is turned on and off in a temperature range near the freezing temperature of water, and the pump 7 is configured to turn on and off in a temperature range higher than the freezing temperature.

In the above configuration, the anti-freezing heating source H may be configured to double as the heat exchanger l heating burner 3,
It may also be an electric heater 13 provided in the heating section 14 of the hot water return path 6b. Also, the pump 7 may be configured to maintain operation for a predetermined period of time after starting to prevent freezing. Furthermore, it is preferable that the temperature sensor S is configured to also serve as temperature sensors lla and llb, which are components of feedback control or feedforward control of the burner 3 for heating the heat exchanger 1.

(effect) The operation of the above configuration will be explained with reference to FIG.

When the temperature of the hot water detected by the temperature sensor S drops to T (for example, 12 degrees Celsius) when the heat-retaining operation is not performed, such as at night or early in the morning in winter, only the pump 7 starts and the water circulates in the circulation path. . This circulation of water averages out the temperature at each location in the circulation path, preventing the formation of localized low-temperature areas. In such an operation, for example, if hot water at a relatively high temperature is held in an area with sufficient heat retention, the hot water temperature detected by the temperature sensor S will temporarily rise after the pump 7 starts operating. However, the temperature may be higher than the temperature at which the pump 7 is turned off. If the operation of the pump 7 is stopped at this point, the temperatures at various locations in the circulation path cannot be sufficiently averaged.

Therefore, by maintaining the operation of the pump 7 for a predetermined period of time after starting regardless of the temperature change of the temperature sensor S, it is possible to prevent the pump 7 from stopping due to local high temperature parts. If the water temperature reaches the temperature T (for example, 13° C.) or more after a predetermined period of time has elapsed, the operation of the pump 7 is stopped, and thereafter the temperature range is T1 to T.

Turn it on and off. Further, if the temperature is below T3, the operation continues.

As described above, when the temperature of the outside air continues to drop while the pump 7 is operating, and the water temperature drops to a temperature T near the freezing temperature (for example, 3°C), the antifreeze heating source H is activated. The circulating water is heated to prevent it from freezing. A temperature T where the water temperature is slightly higher than the above temperature T4, (
For example, when the temperature reaches 6[deg.] C.), the operation of the anti-freeze heat source H stops, and only the pump 7 continues to operate, and thereafter the anti-freeze heat source H is turned on and off in the above temperature range T, ~T.

Although the anti-freeze heating source H is thus turned on and off in the temperature range near the freezing temperature, the temperature at each position in the circulation path is averaged due to the continued circulation operation by the pump 7, and localized low-temperature areas are formed. There is no risk of freezing.

(Example) Next, an example of the present invention will be described with reference to the drawings. For convenience, the same reference numerals will be given to the same components as in the conventional example described above.

In FIG. 1, the symbol l is the heat exchanger of the water heater 2,
3 is a burner for heating it, and 4 is a fan for supplying combustion air. Thus, a hot water supply path 6a is formed from the downstream side of the heat exchanger 1 to the hot water supply section 5, and a hot water return path 6b is provided from the hot water supply section 5 to the upstream side of the heat exchanger l via the pump 7. A water supply route 9 is provided from the water supply section 8 to the upstream side of the heat exchanger 1. In the hot water return route 6b and the water supply route 9, a flow rate sensor 10 and a temperature sensor lla are provided on the route from their meeting point to the upstream side of the heat exchanger 1. A temperature sensor llb is also provided on the downstream side. On the other hand, in the circulation path, a heating section 1 is provided with a check valve 12a on the upstream side of the pump 7 and an electric heater 13 on the downstream side.
4. The water supply path 9 is provided with a check valve 12b and a water flow detection means 15 such as a flow rate sensor or a water flow switch from the upstream side.

In the above configuration, by operating the pump 7 when the hot water supply is stopped, the hot water in the circulation path can be circulated, and during this circulation, the electric heater 1 can be
By turning on 3, a heat-retaining operation can be performed and the temperature of the circulating hot water can be maintained at a predetermined temperature. Such control of the hot water temperature can be performed by using one of the temperature sensors lla and llb provided on the downstream and upstream sides of the heat exchanger 1, respectively, as a control element.

In the above state, when the hot water tap 16 of the hot water supply section 5 is opened, water flows from the water supply section 8 at the same time as hot water is discharged from the hot water tap 16 and flows through the water supply path 9 toward the heat exchanger 1. When the flowing water detection means 15 detects the inflow of water, the ignition sequence of the burner 3 is activated, and the burner 3 is ignited at step 1, which performs operations such as pre-purge by starting the fan 4, and the burner 3 starts combustion at the maximum combustion amount. At the same time, the operation of the pump 7 is stopped. In such hot water supply, the required combustion amount is derived from the set temperature, the actual flow rate, and the water temperature measured by temperature sensor lla, and the burner 3 is feedforward controlled. Predetermined hot water temperature control can be performed by feedback controlling the burner 3 based on the hot water temperature and the set temperature.

Next, when the above-mentioned hot water supply and heat retention operations are not performed, when the temperature of the outside air decreases and the temperature of the water heater 2 decreases together with this, this temperature decrease is caused by the temperature sensor lla, l.
It can be detected by either lb. Therefore, either of these temperature sensors lla and llb can be used as the temperature sensor S to perform antifreeze operation.

In addition, in the same way as the heat retention operation, the water in the circulation path can be heated by the electric heater 13 provided in the heating section 14, so that the electric heater 13 can be used as the antifreeze heating #H.
Anti-freeze operation can be performed as follows. That is, the control means (not shown) operates the pump 7 when the water temperature is below T (for example, 12°C) and stops when the water temperature is above T (for example, 13°C), and the electric heater 13 is activated when the water temperature is T (for example, 13°C) or higher. The antifreeze operation can be performed as described above by controlling the temperature to start at T (3° C.) and stop at T (for example, 6° C.) or higher.

In the above embodiment, the anti-freezing heating source H in the heat retention operation and the anti-freezing operation is the electric heater 13 provided in the heating section I4, but in addition, a burner for heating the heat exchanger 1 is used. It is also possible to have a configuration in which 3 is also used.

(Effects of the Invention) As described above, the present invention provides a hot water supply route from the downstream side of a heat exchanger of a water heater to a hot water supply section via a flow control valve, and a hot water supply path from the hot water supply section to a pump upstream of the heat exchanger. In the operation of the pump and heating source when preventing freezing of a hot water supply device that has a hot water return path leading to the side to form a circulation path and a water supply path leading from the water supply section to the upstream side of the heat exchanger, The heating source is configured to be turned on and off in a temperature range near the freezing temperature of water, and the pump is configured to be turned on and off in a temperature range higher than the freezing temperature, so that the temperature in the circulation path is By the time the operating temperature range of the heating source is reached, the temperature at each location has already averaged out. Therefore, even if the operating temperature range of the heating source is near the freezing temperature of water, the hot water supply opening, return opening, etc. that are directly exposed to outside air are This has the effect of effectively preventing freezing even in areas where insulation materials cannot be applied sufficiently. Since the operating temperature range of the heating source is close to the freezing temperature of water, the operation rate of the heat source for freezing prevention is low, so heat loss is also small, and unlike conventional electric heaters 8 Since a temperature switch such as a bimetallic switch or a bimetal switch is not required, the configuration is simple and the cost is low.

[Brief explanation of drawings]

FIG. 1 is a system explanatory diagram corresponding to an embodiment of a water heater to which the present invention is applied, FIG. 2 is a time chart showing the operation of the present invention, and FIG. 3 is a system explanatory diagram of a conventional water heater. Code l: heat exchanger, 2... water heater, 3... burner, 4
・・Fan, 5・・Hot water supply section, 6a・・Hot water supply route, 6b・
...Hot water return route, 7...Pump, 8...Water supply section, 9...
Water supply route, 10 - Flow rate sensor, lla, Ilb... Temperature sensor, +2a, 12b... Check valve, 13... Electric heater, 14... Heating section, 15... Flowing water detection means, 1
6...Hot water tap, 17...Electric heater for freezing prevention,
18. Temperature switch, 19. Control means, G. Anti-freezing heating source, S. Temperature sensor. Diagram

Claims (5)

[Claims] (1) A circulation path is constructed by providing a hot water supply path from the downstream side of the heat exchanger of the water heater to the hot water supply section, and a hot water return path from the hot water supply section to the upstream side of the heat exchanger via the pump. With,
In a water heater provided with a water supply path from a water supply section to an upstream side of the heat exchanger, a heating source for preventing freezing and a temperature sensor for detecting the temperature of hot water are provided in the circulation path, and the heating source for preventing freezing is provided with a temperature sensor for detecting the temperature of hot water. A freezing prevention mechanism for a water heater, characterized in that the pump is turned on and off in a temperature range near the freezing temperature of water, and the pump is turned on and off in a temperature range higher than the freezing temperature. (2) A freeze prevention mechanism for a water heater, wherein the freeze prevention heat source according to claim 1 is configured to double as a burner for heating a heat exchanger. (3) A freezing prevention mechanism for a water heater, wherein the freezing prevention heat source according to claim 1 is an electric heater provided in a heating section of a hot water return route. (4) The pump according to claim 1 is a freeze prevention mechanism for a water heater, characterized in that the pump maintains operation for a predetermined period of time after the freeze prevention starts. (5) A freeze prevention mechanism for a water heater, wherein the temperature sensor according to claim 1 is configured to double as a temperature sensor forming a component of feedback control or feedforward control of a burner for heating a heat exchanger.