EP3270075B1

EP3270075B1 - Gas-fired water heater with external pump for regulating temperature of outlet water

Info

Publication number: EP3270075B1
Application number: EP17180438.8A
Authority: EP
Inventors: Xinfeng Gai; Yan MIAO
Original assignee: Vaillant Group (china) Heating Cooling And Environmental Technology Co Ltd; Vaillant Wuxi Heating Equipment Co Ltd; Vaillant GmbH
Current assignee: Vaillant Group (china) Heating Cooling And Environmental Technology Co Ltd; Vaillant Wuxi Heating Equipment Co Ltd; Vaillant GmbH
Priority date: 2016-07-13
Filing date: 2017-07-10
Publication date: 2020-10-07
Anticipated expiration: 2037-07-10
Also published as: CN106288336B; ES2840898T3; CN106288336A; EP3270075A1

Description

FIELD OF THE INVENTION

The present invention relates to the field of domestic gas appliances, and more particularly to a preheating module suitable for use in a gas-fired water heating appliance.

BACKGROUND OF THE INVENTION

Gas-fired water heating appliances usually include gas water heaters and gas boilers. A gas water heater, for example, is usually equipped with a burner, a heat exchanger, and a piping system. The burner often includes a number of burner plates arranged side by side, each of which has a gas-air mixing channel in which the gas and air are mixed and passed to the fire holes located at the top of the plate to burn in a combustion chamber and generate heats. The generated heats can be transferred to cold water passing through the heat exchanger, and then the heated water can be output through the pipeline system for use of drinking, bathing and other hot water supply needs. In addition to supply sanitary hot water, a gas boiler can be used to provide a space heating function via radiators connected thereto within dwellings.
When turning on a hot faucet to start a gas water heating appliance, such as a gas water heater, a user often has to wait a long time for hot water output from the hot faucet. This is because, on one hand, there is a large amount of cold water staying in water pipelines within or outside of the appliance, and this amount of cold water has to be drained out first and then hot water comes out; on the other hand, at the beginning of starting the gas water heater, for consideration of security, a blower will be first activated to exhaust residual gas within the combustion chamber and flue pipes, and the combustion burner will be ignited after the residual gas being all replaced by fresh air, during the period, hot faucet continuously outputs cold water. Obviously, the big volume of drained cold water causes the waste of water resources. In addition, this will lead to a poor user experience, for example, when the user desires to take a shower in winter, the user has to wait a long time to get hot water.
One of the applicants of present application has ever filed a patent application that has been published with the number CN 105299875 A and discloses a gas-fired water heating appliance having a preheat function. The appliance is provided with a water pump and a water tank for preheating cold water in the piping system before a user can use it so that hot water can be supplied immediately when the user turns on the hot water faucet, thereby improving the user's experience. However, these additional parts for preheating will undoubtedly increase the manufacturing cost of the entire appliance and increase the price accordingly, as compared with conventional gas water heating appliance. In addition, not all users need such preheating function. For instance, in the southern region of China, since the ambient temperature of tap water would not decrease below a lower level, the preheating function is not necessary for residents in this region, so they will not pay extra for unnecessary functions. In view of this, it is necessary to put forward a more flexible solution to realize the preheating function, so as to better satisfy all needs of different users.
US published patent application US 2008/0265046 A1 discloses a hot water return recirculation system alternatively connected to and isolated from a tankless hot water heater. The hot water return recirculation system includes a recirculation pipeline connecting between the water heater and a hot water distribution pipeline for pumping previously heated warm water from the hot water distribution pipeline back through the recirculation pipeline to the water heater for reheating the warm water and send the reheated water back to the hot water distribution pipeline for use.
In hot summer, when a user has a demand of hot water, like taking a hot shower, since the cold water has an ambient temperature which is relatively high and close to a temperature of output hot water preset by the user, the cold water can be easily overheated and lead to the actual output temperature higher than the preset one. Obviously, the output hot water with higher temperature may result in an accident such as a burn.

SUMMARY OF THE INVENTION

It is an object of present invention to provide a preheating module which can be attached to a gas water heating appliance to preheat cold water accumulated in pipes disposed both inside and outside of the appliance; in addition, the preheating module is able to avoid overheating of cold water in hot summer.
It is another object of present invention to provide a gas water heating system employing the above preheating module.
According to one aspect of the present invention there is provided a preheating module adapted to be attached to a gas water heating appliance for preheating cold water within circulation pipelines disposed inside and outside of the gas water heating appliance prior to the use of the appliance supplying hot water. The preheating module includes an incoming pipe section adapted for being connected to an inlet pipe of the gas water heating appliance, a return pipe section communicating with the incoming pipe section, a first temperature sensor provided in the return pipe section for detecting temperature of water therein, and a water pump provided in the incoming pipe section. The preheating module further includes a cold water incoming pipe section communicating with the incoming pipe section, a flow sensor provided in the cold water incoming pipe section for detecting a water flow therein, and a second temperature sensor for detecting temperature of water in the cold water incoming pipe section. A controller is electrically connected with the water pump, the first temperature sensor, the flow sensor and the second temperature sensor. The controller is configured to detect the temperature of water in the return pipe section via the first temperature sensor after a preheating mode being activated, and start an operation of the water pump if the detected temperature of water is lower than a first temperature threshold. The controller is configured to detect the temperature of water in the cold water incoming pipe section via the second temperature sensor after sensing the water flow in the cold water incoming pipe section via the flow sensor and start the operation of the water pump to increase the water flow if the detected temperature of water exceeds a third temperature threshold.
Preferably, the preheating module further includes a check valve provided in the return pipe section so that water can only flow from the return pipe section to the incoming pipe section.
Preferably, the return pipe section is arranged in parallel with the cold water incoming pipe section.
Preferably, during the preheating mode, the controller is further configured to continuously detect the temperature of water in the return pipe section and stop the operation of the water pump when the temperature of water exceeds a second temperature threshold that is larger than the first temperature threshold.
According to another aspect of the present invention there is provided a gas water heating system including a gas water heating appliance and the afore-mentioned preheating module. The gas water heating appliance includes a burner, a heat exchanger, an inlet pipe, and an outlet pipe. The incoming pipe section of the preheating module is connected to the inlet pipe.
Preferably, the preheating mode is activated according to a time preset by a timer, or is activated according to a command received by a communication device.
In one embodiment, the controller is provided in the preheating module.
In an alternative embodiment, the controller is provided in the gas water heating appliance and electrically connected with the water pump, the first temperature sensor, the flow sensor, and the second temperature sensor via an electrical connector assembly.
Preferably, the gas water heating appliance includes a first housing for receiving the burner, the heat exchanger, and the inlet and the outlet pipes; the preheat module includes a second housing for receiving the incoming pipe section, the return pipe section, the water pump, the first temperature sensor, the cold water incoming pipe section, the flow sensor, and the second temperature sensor.
Compared with the state of art, the present invention has the advantages that: the preheating module can be attached to a gas water heating appliance to ensure that hot water is always ready for demands of use, so as to enhance users' experience. Moreover, since the preheating module can be provided independent of the gas water heating appliance, manufacturers can sell the gas water heating appliance and the preheating module separately, or sell an assembly consisting of the gas water heating appliance and the preheating module, so as to meet different users' demands. Furthermore, when there is a demand of hot water and the cold water introduced into the gas water heating appliance has a relatively high ambient temperature, the preheating module is able to increase water flow of the cold water by operation of the water pump, thereby avoiding the output hot water with a higher temperature, which results in a poor user experience.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic plan view showing a gas water heating system in accordance with a first embodiment of present invention, wherein the system is connected with external pipelines and water facilities;
Fig. 2 is a schematic plan view showing a gas water heating system in accordance with a second embodiment of present invention, wherein the system is connected with external pipelines and water facilities;
Fig. 3 is a schematic plan view showing a gas water heating system in accordance with a third embodiment of present invention, wherein the system is connected with external pipelines and water facilities;
Fig. 4 is a schematic plan view of a specific example of the gas water heating system in the first embodiment as shown in Fig. 1;
Fig. 5 is a schematic perspective view of the gas water heating system of Fig. 4, wherein the housing of a preheat module of the system is removed to show its internal configuration;
Fig. 6 is a schematic perspective view of the gas water heating system of Fig. 5 from another perspective;
Fig. 7 is an exploded view of part of the components of the preheating module in the gas water heating system shown in Fig. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawing figures to describe the preferred embodiments of the present invention in detail. However, the embodiments can not be used to restrict the present invention. Changes such as structure, method and function obviously made to those of ordinary skill in the art are also protected by the present invention.
Gas water heating appliances could be fired with combustible gas, such as natural gas, city gas, liquefied petroleum gas, methane, etc., thereby supplying hot water and/or heating living space for domestic sanitary usage and heating purpose, such as gas water heaters and/or gas boilers. A gas water heater will be exemplified hereinafter.
In a first embodiment as shown in Fig. 1, the reference number 1 indicates a gas water heater. The gas water heater 1 includes a first housing 10, and a burner 11, a heat exchanger 13, a flue hood 14, an exhaust pipe 15 are all received in the first housing 10. When the gas water heater 1 performs a normal heating operation, the burner 11 ignites the mixture of gas and air, and the mixture is combusted in a combustion chamber 12 defined between the burner 11 and the heat exchanger 13. The high-temperature flue gas generated by the combustion is driven by a fan (not shown) through the heat exchanger 13 and transfers the heat to a water flow passing through a water pipe 162 coiled outside of the heat exchanger; the flue gas passing through the heat exchanger 13 is then collected by the flue hood 14 and discharged via the exhaust pipe 15. An inlet pipe 161 and an outlet pipe 163 are located upstream and downstream of the heat exchanger 13 respectively, and are both communicated with the water pipe 162 coiled outside the heat exchanger. The inlet pipe 161 and the outlet pipe 163 extend beyond the bottom of the first housing 10. Since the construction and working principle of the gas water heater are well known to those skilled in the art, a detailed description is omitted for purpose of brevity and simplicity.
Refer to Figs. 4 through 7, a preheating module 2 can be independently mounted to the bottom of the gas water heater 1, in other words, the preheating module 2 can be an accessory for the gas water heater 1. The preheating module includes a second housing 20, an incoming pipe section 171 and an outgoing pipe section 173 both received in the second housing and respectively connected to the inlet and the outlet pipes 161, 163 of the gas water heater, a return pipe section 172 and a cold water incoming pipe section 174 both connected to the incoming pipe section 171. The cold water incoming pipe section 174 communicates with external cold water pipelines 41, and the outgoing pipe section 173 communicates with external hot water pipelines 43, and the return pipe section 172 communicates with external return pipelines 42. When a user has the demand for hot water, cold water flowing from the cold water pipelines 41 enters the gas water heater through the cold water incoming pipe section 174 and the incoming pipe section 171 for being heated, then the heated water flows out of the gas water heater through the outgoing pipe section 173 and the hot water pipelines 43 to reach a water supply device 4, like a mixing valve, and mixes with cold water from the cold water pipelines 41 to output water at an appropriate temperature. Before the use of the gas water heater supplying hot water, cold water existing in the circulation pipelines disposed inside and outside of the gas water heater can be heated in a preheating mode, and in this mode, the water in the return pipelines 42 and the return pipe section 172 flows into the gas water heater through the incoming pipe section 171 for being heated, then the heated water passes through the outgoing pipe section 173 and the hot water pipelines 43 and enters the return pipelines 42 again. The circulation is recycled until the temperature of water within the circulation pipelines reaches a predetermined temperature value.
A water pump 21 can be associated with one of the incoming pipe section 171 and the return pipe section 172 for driving the flow of water therein. In this embodiment, the water pump 21 is provided in the incoming pipe section 171. A first temperature sensor 22 is provided in the return pipe section 172 for detecting temperature of water therein. The first temperature sensor 22 may be a NTC (Negative Temperature Coefficient) thermistor. A check valve 25 is also provided in the return pipe section 172 so that the water can only flow from the return pipe section 172 to the incoming pipe section 171. In this embodiment, the preheating module 2 further includes a controller 30. The controller 30 may be a logic control circuit in which a number of electronic components are connected in a certain wiring manner, or may incorporate a Micro Controller Unit (MCU) storing program instructions, or may be an integrated chip with a proprietary use, such as ASIC (Application Specific Integrated Circuit), or FPGA (Field Programmable Gate Array), etc.. The controller 30 can be electrically connected to the water pump 21 and the first temperature sensor 22 through electrical wires.
The controller 30 may be triggered to enter a preheating mode. In the preheating mode, the controller 30 detects temperature of water in the return pipe section 172 through the first temperature sensor 22. If the detected water temperature is lower than a first temperature threshold T1, it indicates that the temperature of the water in the pipeline is too low and not suitable for direct use, thus, the controller 30 starts an operation of the water pump 21. When a water flow entering the gas water heater 1 is detected, the gas water heater is enabled to work, thereby heating the cold water in the circulation pipelines disposed inside or outside of the gas water heater 1. During the period, the controller 30 continuously detects the temperature of water in the return pipe section 172 by the first temperature sensor 22 and stops the operation of the water pump 21 when the water temperature exceeds a second temperature threshold T2, and then the gas water heater 1 stops working accordingly. The first temperature threshold T1 may be set at an acceptable comfort temperature, such as 35°C, which depends on the user's somatosensory. And the second temperature threshold T2 is typically set higher than the first temperature threshold T1, such as 40°C. This is to take into account the temperature of water in the return pipe section 172 may be somewhat reduced for some time before the demands of supplying hot water.
The preheating mode can be activated by a timer (not shown). The timer may be integrated with the controller 30 or may be independent of the controller 30. For instance, a user usually bathe at 9:00 pm, in this case, the timer can be set the time to activate the preheating mode at 8:50 pm, so that the user can enjoy instant hot water when he turns on the tap at 9:00 pm. The preheating module 2 may also be provided with a communication device (not shown) which is electrically connected with the controller 30 and has a communication module for realizing a wired or wireless communication with external communication devices, so that the preheating mode can be activated according to a command received by the communication device. For example, the user wants to take a bath immediately after arriving at home when he is on the way home, in this case, he can activate the preheating mode by a remote control through his mobile phone 50, so that he can enjoy instant hot water after back home.
As shown in Fig. 1, in this embodiment, the preheating module 2 further includes a flow sensor 23 and a second temperature sensor 24 mounted in the cold water incoming pipe section 174. The second temperature sensor 24 may be a NTC thermistor. The controller 30 is electrically connected to the flow sensor 23 and the second temperature sensor 24. In summer, when a user has a need of hot water, since the cold water has an ambient temperature which is relatively high, the temperature of water heated in the gas water heater increases quickly and may lead to a temperature higher than that preset by the user. In order to avoid this situation, when the gas water heater starts working, the controller 30 can detect a water flow through the flow sensor 23, and then detect the temperature of water passing through the cold water incoming pipe section 174 by the second temperature sensor 24. If the detected water temperature exceeds a third temperature threshold T3, it indicates that the temperature of the cold water introduced into the gas water heater at this time is relatively high, and then the controller 30 starts the operation of the water pump 21 to increase the flow rate of the cold water so as to avoid raising the water temperature quickly, and thus avoid a higher temperature of output hot water. Of course, the third temperature threshold T3 may be preset according to the user's somatosensory, for example, 30 °C. In addition, in this embodiment, the return pipe section 172 and the cold water incoming pipe section 174 are arranged in parallel, so as to prevent the preheating module from interfering with each other when realizing the preheating function and the function of raising the water flow of intaking cold water.
Fig. 2 shows a second embodiment of the gas water heating system, which differs from the first embodiment as shown in Fig. 1 in that: the controller 30 is disposed in the first housing 10 of the gas water heater, and the controller can also be used to control the operation of the gas water heater. The controller 30 may be electrically connected to components within the preheat module 2 via an electrical connector assembly. As shown in Fig. 2, the electrical connector assembly may include a receptacle 35 including a number of sockets disposed at the bottom of the first housing 10 and a number of plugs 31, 32, 33, 34 respectively connected to the water pump 21, the first temperature sensor 22, the flow sensor 23, and the second temperature sensor 24 via electrical wires. When the preheating module is mechanically connected to the gas water heater, the number of plugs 31, 32, 33, 34 are plugged into the corresponding sockets of the receptacle 35 to establish electrical connections between the controller 30 and the water pump 21, the first temperature sensor 22, the flow sensor 23, and the second temperature sensor 24.
Fig. 3 shows a third embodiment of the gas water heating system, which differs from the first embodiment as shown in Fig. 1 in that: the gas water heating appliance in this embodiment is a gas boiler 6. The gas boiler has a first housing 60, and a burner 61, a heat exchanger 62, a secondary heat exchanger 63, and a three-way valve 64 are all received in the first housing 60. When there is a demand for hot water, cold water enters an inlet pipe 661, then passes through a pipe 662 and is heated by the heat exchange 62. The heated water then flows out of the gas boiler via the three-way valve 64 and an outlet pipe 663. When there is a demand for space heating, under control of the three-way valve 64, the heated water flows through the secondary heat exchanger 63 instead of flowing out of the gas boiler via the outlet pipe 663, thus, water for space heating obtains heat on passing through the secondary heat exchanger and is circulated in a boiler circuit 664. Space heaters 65, such as radiators or under floor heating loop, which are connected in the boiler circuit 664 and positioned in a dwelling for space heating purpose. Since the construction and working principle of the gas boiler are well known to those skilled in the art, a detailed description is omitted for purpose of brevity and simplicity.
The preheating module can be attached to a gas water heating appliance to ensure that hot water is always ready for demands of use, so as to enhance users' experience. Moreover, since the preheating module can be provided independent of the gas water heating appliance, manufacturers can sell the gas water heating appliance and the preheating module separately, or sell an assembly consisting of the gas water heating appliance and the preheating module, so as to meet different users' demands. Furthermore, when there is a demand of hot water and the cold water introduced into the gas water heating appliance has a relatively high ambient temperature, the preheating module is able to increase water flow of the cold water by operation of the water pump, thereby avoiding the output hot water with a higher temperature, which results in a poor user experience.
It is to be understood, however, that even though numerous, characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosed is illustrative only, and changes may be made in detail, especially in matters of number, shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broadest general meaning of the terms in which the appended claims are expressed.

Claims

A preheating module (2) adapted to be attached to a gas water heating appliance (1) for preheating cold water within circulation pipelines disposed inside and outside of the gas water heating appliance prior to the use of said appliance supplying hot water; wherein said preheating module comprises:
an incoming pipe section (171) adapted for being connected to an inlet pipe (161, 661) of the gas water heating appliance, and a return pipe section (172) communicating with said incoming pipe section;

a water pump (21) provided in the incoming pipe section;

a first temperature sensor (22) provided in the return pipe section for detecting temperature of water therein;

a cold water incoming pipe section (174) communicating with the incoming pipe section (171);

a flow sensor (23) provided in the cold water incoming pipe section for detecting a water flow therein;

a second temperature sensor (24) for detecting temperature of water in said cold water incoming pipe section; and

a controller (30) electrically connected with the water pump, the first temperature sensor and the flow sensor and the second temperature sensor; wherein

said controller is configured to detect the temperature of water in the return pipe section via the first temperature sensor after a preheating mode being activated, and start an operation of the water pump if the detected temperature of water is lower than a first temperature threshold (T1); and said controller is configured to detect the temperature of water in the cold water incoming pipe section via the second temperature sensor after sensing the water flow in the cold water incoming pipe section via the flow sensor and start the operation of the water pump to increase the water flow if the detected temperature of water exceeds a third temperature threshold (T3).
A preheating module according to claim 1, characterized in that the preheating module further comprises a check valve (25) provided in the return pipe section so that water can only flow from the return pipe section to the incoming pipe section.
A preheating module according to claim 1, characterized in that the return pipe section (172) is arranged in parallel with the cold water incoming pipe section (174).
A preheating module according to claim 1, characterized in that, during said preheating mode, and the controller is further configured to continuously detect the temperature of water in the return pipe section and stop the operation of the water pump when said temperature of water exceeds a second temperature threshold (T2) that is larger than the first temperature threshold (T1).
A gas water heating system (100), characterized in that, said system comprises:
a gas water heating appliance (1) comprising a burner (11, 61), a heat exchanger (13, 62), an inlet pipe (161, 661), and an outlet pipe (163, 663); and

a preheating module (2) according to any of the preceding claims; wherein the incoming pipe section (171) of the preheating module is connected to said inlet pipe.
A gas water heating system according to claim 5, characterized in that said system is arranged such that the preheating mode is activated according to a time preset by a timer, or is activated according to a command received by a communication device.
A gas water heating system according to claim 5, characterized in that said controller is provided in the preheating module.
A gas water heating system according to claim 5, characterized in that the controller is provided in the gas water heating appliance and electrically connected with the water pump and the first temperature sensor and with the flow sensor and the second temperature sensor via an electrical connector assembly (31, 32, 33, 34, 35).
A gas water heating system according to claim 5, characterized in that the gas water heating appliance comprises a first housing (10) for receiving the burner, the heat exchanger, and the inlet and the outlet pipes; the preheat module comprises a second housing (20) for receiving the incoming pipe section, the return pipe section, the water pump, the first temperature sensor, the cold water incoming pipe section, the flow sensor, and the second temperature sensor.