Shell: The shell of the hot electric water heater is divided into base and cover, that is, the shell of the hot electric water heater is mostly made of insulating material, and there are also a few metal shells (such as aluminum alloy and stainless steel). Because the instant electric water heater is used in live working state, the use environment is humid, the metal material is conductive and the safety performance is low. It is not recommended to choose the instant electric water heater with metal shell.
Instant electric heating system is the heart of instant electric water heater. The reliability and safety of the heating device are very important. Hydropower must be truly separated. According to the water quality and electricity consumption environment in China, water leakage, electric leakage, scaling and dry burning should be prevented to ensure safe use.
Circuit control system: the brain of hot electric water heater, which is divided into gear control, intelligent constant temperature control, accurate temperature control and intelligent protection.
Starting device: accurately detect the size of water flow, inlet and outlet water temperature, transmit water flow signals, ensure that the water heater is not dry, and accurately control the temperature. Instant electric heater is the key to the safety and efficiency of instant electric water heater. Water leakage is the key to be solved in the core heating technology of instant electric water heater, and the anti-electricity wall, safety detection of wire control system, leakage protection function and external leakage protection switch also play a certain role. Modern people's safety requirements for household appliances are to achieve 100% safety, so how to solve the problem of water leakage in the instant heating system has become the top priority of the household appliance industry.
In order to let users better choose a safe and reliable instant electric water heater, let's analyze the advantages and disadvantages of various heating systems:
First generation glass transistor heater
Advantages: there is a circuitous water flow channel formed by glass tube, which specifies the direction of water flow, so that the water temperature rises gradually at a uniform speed, and the outlet temperature is uniform, without the phenomenon of hot and cold. The waterway is long, the water moves in the pipeline for a long time, the heat exchange time is long, and the heat exchange efficiency is high.
Defect: The glass crystal tube is easy to break and leak when it works under high temperature and high pressure for a long time, while the glass tube heater relies on the coating on the surface of the glass tube to generate heat, but once it leaks, it will inevitably leak. The temperature is concentrated on the surface of the glass tube, which makes the inner wall easy to produce scale and affects the heat transfer. Therefore, after a period of time, the thermal efficiency decreases and the possibility of tube explosion increases. In addition, water leakage at the end is also the biggest defect of the glass tube heater. The connection between multiple glass tubes depends on the end caps and sealing aprons at both ends. The end cover is bolted to seal the apron. This structure is fixed, too much force will directly crush the pipe, but too little force will lead to water leakage.
Second generation cup heater
One is a stainless steel cup heater and the other is a copper cup heater. The structure, principle and performance of these two heaters are exactly the same except for the different materials on the cup body. The cup is a container for holding water, which will neither generate heat nor serve as a conductive medium for heat conduction (it is said that the copper cup heater has higher thermal efficiency than the steel cup heater, which is purely misleading to consumers). If we have to say the difference between the two, it is that the materials are different, and copper is easier to oxidize than steel in water.
Advantages: looking at the stainless steel electric heating tube alone, it has strong corrosion resistance, high heat transfer efficiency, water and electricity isolation and good insulation performance of the insulation layer.
Disadvantages: In the cup structure, the electric heating tube is immersed in water for a long time. During the heating process, the heating pipe directly transfers the high temperature to the water near the pipe wall, and then transfers it to the surrounding water through the thermal movement of water molecules. The heat transfer and heat conduction of water are slow, resulting in low thermal efficiency; Long-term high temperature and high pressure, thermal expansion and cold contraction, and heat concentration on the surface of the tube are easy to produce serious scale on the surface of the tube, which will lead to the decrease of heat exchange speed and thermal efficiency, the increase of tube surface temperature, the cracking and bursting of the tube wall, which will damp the insulation layer and lead to the danger of electric leakage. Therefore, in this structure, when the heating pipe is directly soaked in water for heating, once the pipe wall is damaged and damp, it cannot be kept warm, so it is not really water and electricity isolation. In addition, the metal cup is easy to be oxidized and corroded, especially in the welding part of the cup body, which leads to the failure of the water heater to work normally. The terminals of the cup heater are concentrated above the cup body. If improperly installed, the terminal will loosen in the process of alternating cold and hot for a long time, causing short circuit and burning the heater or circuit board. From the thermal principle, we know that the temperature at the top is the highest, and the heat of the terminal itself will overheat and burn it out. Another disadvantage of the cup heater is that there is no water flow channel, cold water flows in from the bottom of the cup cavity and out from the top, and the water flows irregularly in the cup body, so the temperature of the outlet water rises and falls, which is what we often call uneven cold and hot.
The Third Generation Plane Superposition Heater
This heater is a new structure heater introduced in recent years. It is a heater with water flow channels, which is composed of two or more layers of plane aluminum alloy plates. The heating wire wound by mica sheet is sandwiched between two aluminum plates to form a structure of surface heating and plate heat transfer, and the two ends are sealed with end covers to connect the surfaces of each water flow channel.
Advantages: plane heating, up-and-down heat exchange, heat dissipation, heat load reduction and high efficiency; Like the glass tube, it has a designated waterway, which gradually heats up evenly, without the phenomenon of hot and cold, and it is beautiful as a whole.
Disadvantages: the corrosion resistance of aluminum body is extremely poor, and the aluminum plate-type water flow channel is easy to corrode and leak. However, the heater is separated between the aluminum plate and the heating plate by two mica sheets, which can't be sealed, so the mica sheets are easy to get wet and cause leakage, and the end cover seals the water channel, which has the same defects as the glass tube.
The Fourth Generation Semiconductor Ceramic Heater
Semiconductor is a kind of ceramic heater, which has two heating methods:
First, the ceramic heating plate is directly inserted into the water for heating, which is a metal cup-shaped shell, similar to the internal cup-shaped heater, and has the disadvantages of the cup-shaped heater;
2. Metals (aluminum, copper, etc. ) The material is designed as an independent water flow channel, and then it is bent into a multi-section S-shape, and the gap is reinforced with ceramic sheets. The whole heating is a combination of nonmetallic and metallic materials. The safety performance can be imagined. The biggest defects of ceramic sheets are slow heating, slow heat transfer, slow heat dissipation and high thermal hysteresis temperature. Therefore, the hot water speed of this water heater is slower than other water heaters, and the temperature difference is unstable when the water flow fluctuates, resulting in the phenomenon of hot and cold.
The fifth generation electromagnetic heater
Electromagnetic heating technology is to make the metal molecules of metal utensils containing water move at high speed through electromagnetic field oscillation, resulting in high temperature. There is a certain air gap between the electromagnetic coil and metal appliances and materials such as heat insulation.
Advantages: The biggest advantage lies in the complete separation of water and electricity, safety and high thermal efficiency.
Disadvantages: As we all know, the failure rate of induction cooker is high, and thermal radiation is harmful to the control system. Under high power, IGBT is easy to burn out. The power of water heater is more than four times that of induction cooker, so it is difficult to control the small power. Intermittent heating, high inlet temperature, low power, unstable water temperature, can not be used. Large volume; High cost.
A New Generation of 3D MAX Integrated Extreme Speed Heating System
3D MAX integrated rapid heating system is an integrated heating system developed by technicians of Zhongshan Hangong Electric Appliance Co., Ltd. through years of efforts, combining the advantages of various instant heating technologies, improving and perfecting the heating technology of instant electric water heaters. It has been recognized by the industry and obtained a number of national patent technologies.
Advantages:
1, heat conduction principle: the heat source generated by the electric heating device is quickly transferred to the integrally cast metal filler through the pipe wall (the metal material has extremely fast heat conduction performance), so that the temperature of the whole metal body is uniformly dispersed, the temperature per unit area of the heating element is reduced, the heat load of the heating element is reduced, and at the same time, the heat exchange with all the water in the three-dimensional surrounding waterway is carried out at the same time, thus improving its thermal efficiency. With the acceleration of heat source dispersion and the improvement of thermal efficiency, the aging of heater also slows down.
2. The gap between the heating tube and the water flow channel is filled with metal casting, so the surfaces of the heating element and the water flow channel are completely isolated from the air, eliminating the possibility of surface oxidation. The waterway is surrounded by stainless steel pipes, and there are no joints, solder joints and welds, which completely eliminates the risk of water leakage and corrosion that may be caused by welding. (water-stainless steel water flow channel wall-integral pouring filling layer-heating pipe wall-insulation layer-heating element) Its structure completely prevents water from contacting the electric heating element, and even if the water pipe or electric heating pipe is broken, it will not make the electric heating element damp or contact with water, thus realizing real water-electricity separation.
3. The size of the heater is 240mm× 100mm×30mm, and the water flow channel of the heater is formed by winding a stainless steel tube with a total length of nearly 6000mm around 1 1 turn, and the length of each turn is 520 mm.. It has a long water pipe and a large heat exchange area (the inner diameter of the pipe is 6.5mm× π× 6000mm = 65438.
4. The metal material is cast as a whole, the weight of the heater is 2. 1kg, and the pressure resistance is 2000 V/
5. The water inlet and outlet interfaces are connected by high-pressure stamping interfaces without solder joints, which completely eliminates the problem of water leakage in and out of traditional heaters due to solder joint corrosion. Moreover, the movable joint is used to connect the inlet and outlet nonmetallic water nozzles (safety insulation), and the heater does not need to be disassembled when installing, disassembling and repairing the water inlet switch and the water outlet nozzle, so the operation is simple. The center distance between the water inlet and the water outlet of the heater can be adjusted by using movable joints, which can be applied to any style (horizontal) shell on the market.
6. The terminals are connected by high-voltage stamping, which avoids the contact loss caused by welding, or the phenomenon that the terminal current is too large to burn the circuit due to virtual welding or poor welding.
Disadvantages: complex process, increased production difficulty and relatively high cost.
Special statement: There are products imitating this heating system in the market, but in order to reduce the cost, its imitators not only use inferior materials, but also shorten the materials such as waterways and double-ended heating pipes. Although the appearance is similar to our heating system, the performance and quality are greatly reduced.
"3D MAX Integrated Extreme Speed Heating System" is called "cast aluminum heater" only because its structure is made of aluminum alloy. The integrated filled heat-conducting medium can be any metal material with high heat-conducting efficiency, not limited to aluminum alloy material, so as to avoid misleading consumers by imitating the technology called "cast zinc and cast copper heater" in the future.
Judging from the advantages and disadvantages of the above generations of traditional heaters, to improve the thermal efficiency and quality of heaters, the following should be done:
Increase heat exchange area, speed up heat exchange and improve efficiency; The heating time is prolonged, the pipeline channel is heated, the pipeline is long, the heating time is long, and the heat transfer is more sufficient; It has good heat transfer medium, fast heat transfer and fast heat transfer speed; The water channel and pipeline of the heater should not be connected by welding, and should not be sealed with liquid in a large area to prevent leakage of corrosive liquid; The heating element must not be affected with damp, and the water and electricity must be completely isolated to ensure safety; Reduce the heat load of heating elements, reduce the generation of scale and prolong the service life. The quality of the circuit control system determines the use, safety and performance of the water heater. The circuit control system is divided into multi-step control system and constant temperature control system.
Gear control type
Generally, the instant electric water heater has about seven gears, and the heating power is controlled by closing the relay. The quality of relay is related to the quality, life and safety of circuit control system. In the field of instant electric water heaters, the relay quality of Matsukawa, Hongfa and Le Song ranks in the top three. However, due to the high power and high assembly technology of the instant electric water heater, plug terminals are not allowed to be used for connection, and only Matsukawa needs to be connected by bolts. Hongfa or other relays are also used for self-drilling and assembly on terminals. Although the connection is firm, the surface of the terminal has been damaged during self-drilling, and there may be burrs, which may lead to poor contact between the relay terminal and the connecting wire terminal, which may easily lead to heating and wire burning, resulting in danger, or the damaged terminal surface will be oxidized after long-term use, which will also have the same consequences.
The control scheme of double break and double open must be adopted in the wire control system. When the water heater is started and shut down, the two poles of the power supply (live wire and zero wire) should be disconnected or connected at the same time. Many people mistakenly think that the zero line is zero potential and there is no voltage, so there is no fear when disconnecting. Theoretically, we know that three-phase electricity is 380V, that is to say, the interphase voltage (that is, the voltage between one live wire and another live wire) is 380V, while the voltage between single-phase live wire and neutral wire is 220V, which is the so-called unidirectional electricity. When the three-phase loads are completely equal, the voltage on the neutral line is 0V and the current is three-phase. But what is really exciting is not voltage but current, and alternating current is positive and negative. The current changes from fire to zero or from zero to fire, and the cross flow is called alternating current; The unidirectional direct current flowing from the positive electrode to the negative electrode is called direct current. Whether it is AC or DC, it means that the current flows from one pole to the other to form a loop, and the load on the loop can do work, so no matter which side of the current is equal, the greater the current, the greater the harm to the human body. Therefore, it is safe to cut off the bidirectional power supply during shutdown or protection. The control scheme of double break and double open is realized by closing the relay.
Constant temperature control type
In the constant temperature control system, SCR is mainly used to adjust the voltage input to the heating system, thus changing the power. Some manufacturers think that relays are used to control live wires and thyristors are used to control neutral wires, which is a wrong understanding. Thyristors are used to adjust the input voltage, not to switch. Many people think that neutral line power failure is not dangerous, and the above analysis is also wrong. Even if there is no voltage, there is current on the neutral line, so it is necessary to disconnect the neutral line. Moreover, many household connections are not standardized and are not connected with the national standard red cable and blue cable, so the electricity consumption environment is complicated and dangerous, and the control scheme of double relays and double switches must be used to ensure safety.
In the constant temperature system, the intelligent variable frequency constant temperature control system of Sony Ericsson instant electric water heater has made a great breakthrough. Constant temperature effect and speed are well-known in the industry. The constant temperature speed is fast, the response is sensitive, the constant temperature effect is good, and its products are more stable and energy-saving. Many constant-temperature water heaters on the market can keep constant temperature for more than 20 seconds to more than 40 seconds, and it is not uncommon to exceed 1 minute. Sony Ericsson intelligent variable frequency constant temperature water heater can achieve constant temperature effect in seven or eight seconds. For water heaters with long constant temperature adjustment time, if the water flow or voltage changes suddenly during the shower, it will take a long time to reach stability due to slow response, untimely power adjustment and great temperature difference, which may easily lead to burns or colds. When the water flow or voltage of the instant electric water heater in Han Palace changes, the power changes accordingly to keep the temperature unchanged. When the water flow or voltage changes too much, there is a deviation of 1 to 2 degrees, and it will return to the set water temperature in about 3 seconds, which is fast and safe. This requires a high level of control system, and the control scheme and program of microcomputer control chip should be very accurate, which is also a test for the R&D ability of water heater manufacturers. Therefore, when you choose a water heater, please choose the products of manufacturers with professional R&D strength.
Some manufacturers can't reach the constant temperature height in the control system, so thermostatic valve device is installed at the water inlet. Thermostatic valve is a steady-flow device of water flow, which is called a steady-flow valve. Its cost is about 100 yuan. It is to keep the water flow constant when the water pressure changes, so as to ensure the constant outlet temperature of the water heater. This method seems feasible, but if the voltage changes, the constant temperature cannot be achieved, and after long-term use, the sensitivity of the automatic water stabilizer valve decreases, and the surface of the metal body is oxidized by water or stuck by impurities in the water, which will make it unable to work normally. Instant electric water heater is a kind of instant hot water device, that is, the water works normally and safely when flowing, and stops working when the water is turned off. Therefore, there must be a water flow control device on the water road. Water flow switch used in instant electric water heater mainly includes: reed switch magnetic core induction switch, Hall water flow switch and infrared induction water flow switch.
1, magnetic reed switch magnetic core induction switch
Previously, the "floating magnetic" switch widely used by instant electric water heater manufacturers has a certain weight because there is a magnetic core inside the water inlet and a reed switch is installed outside the water inlet. When there is no water flow, the magnetic core is at the bottom of the water inlet, far away from reed switch, and the power supply of the water heater has no signal induction, so the water heater cannot work. When the water valve is opened, the inner magnetic core floats to the upper part of the water inlet. At this time, the reed switch senses the magnetic field signal and controls it. This switch can't detect the flow of water, and is generally used for multi-stage water heaters.
Because the nozzle is made of magnetic core, the magnetism will gradually demagnetize in water for a long time, and the performance is unstable. When the metal substance magnetically adsorbed in the water for a long time reaches a certain amount, the magnetic core will get stuck in the water nozzle and cannot move. If it is stuck at the bottom, the water heater will not work, but there is no danger. If the water is stuck at the top of the water tap after use, the signal will not be turned on, and the water heater will continue to work without water, which is what we usually call dry burning. When dry burning is serious, it may cause safety hazards such as burns to the human body. This kind of switch is rarely used by manufacturers.
2. Hall flow switch
Adopt German Hall induction technology. A rotating wheel is arranged in the water inlet, and a magnetic ring is arranged on the rotating wheel. Hall sensing device is installed on the surface of the water nozzle. When the runner rotates under the push of water flow, the magnetic ring on the runner moves and the magnetic field moves with it. The higher the movement frequency, the stronger the signal, so as to measure the water flow. When the water flow stops, the signal is interrupted, and the control system can control the startup, shutdown and power increase and decrease through the detected water flow, which can play an important role in the constant temperature system. Gear shifting machine can also be used generally, and it is the most widely used water flow starting device in instant electric water heaters.
However, if the waterway is not clean, there are metal substances or large sundries, which will also block the runner and cause it to fail to work normally; Long-term wear and tear of the rotating shaft of the runner will lead to deviation of the runner and unstable signal. The sensitivity of the runner requires a high degree of matching between the Hall element and the magnetic ring. In order not to make the rotor eccentric, the structure is compact, the gap is small, and the place with poor water quality is easy to get stuck; When the surface of the magnetic ring is scratched or soaked in water for a long time, it will slowly demagnetize, which is also related to the water temperature. The higher the water temperature, the faster the demagnetization. If there is no magnetism, there will be no danger. If there is no signal, there is no heating. But this water flow switch at least ensures that the water heater will not work or be dangerous because of dry burning.
3. Inductive switch of infrared water flow sensor
Infrared water flow sensor is a sensing device technology that uses infrared light to sense and test water flow. It is similar to the structure of Hall flow switch, but it does not use a magnetic ring on the flow channel. It mainly cuts off the infrared light by rotation and generates pulse signals. The pulse signal is different with different water flow size and rotation speed, so as to realize the function of controlling starting, closing and increasing or decreasing power. The rotor shaft will not be worn due to the magnetic core sticking, and the rotor will be offset for a long time, and the signal will not be unstable. As long as the infrared light can be continuously cut off, it can work normally. 1, over-temperature protection
According to the national standard, that is, the outlet temperature of electric water heater should not be higher than 55℃, which is dangerous to human body. In general, the maximum set temperature of constant temperature water heater is about 52℃. If the water flow or voltage changes, the water temperature of a good constant temperature water heater will not change more than 55℃. The gear shifter will automatically downshift when it is over-temperature protected at 55℃, so that it will not be over-temperature next time.
2, dry burning protection
When the surface temperature of the heater exceeds 95℃ under normal use, machine performance problems or over-temperature protection failure, the dry-burning protector is started and all power supplies are cut off. Please ensure safety when using.
3. Leakage protection
1) The reliability of the heating system itself, whether there are hidden dangers of water leakage, and real water and electricity isolation are the standards for measuring the safety performance of electric water heaters;
2) Leak detection of control system. When the leakage is greater than 20mA, the system should cut off the power supply within 0. 1 s to ensure the safety of bathing;
3) Good grounding;
4) The air gap and creepage distance between the rechargeable body and the shell, heating system, wire control system and water inlet and outlet should be greater than 5 mm.
5) Conductive materials such as metal or electroplating cannot be used in the water inlet and outlet, otherwise once the heating system leaks electricity, it will come out through the water inlet and outlet;
6) When the performance of most water heaters can't ensure the safety of electricity consumption, they completely rely on the electricity-proof wall, which mistakenly leads users to think that it is safe to have the electricity-proof wall, but ignores the factors such as water electrification and shell electrification;
7) The external leakage protection switch is the last leakage protection device installed in the user's home, which is also a mandatory requirement of the country.
Ten Intelligent Safety Protection of Instant Electric Water Heater
1, national standard electricity-proof wall; 2. Mutual inductance leakage protection device; 3, anti-dry burning protection device; 4. Overvoltage protection device; 5. Automatic power-off protection device; 6, fault self-check protection device; 7. Over-temperature protection device; 8. Two-way disconnection protection device; 9. Patented heating technology for hydropower separation heater; 10, imported ABS insulation fuselage and internal and external insulation coating protection.