An electric water heater is a device that heats water by converting electrical energy into thermal energy, and its working principle is mainly based on the principle of resistive heating. The following is a detailed introduction:

Basic Structure and Composition: An electric water heater generally consists of components such as a storage tank, electric heating elements, a temperature controller, a magnesium rod, and a safety valve. The storage tank is used to store water; the electric heating elements are the key components for converting electrical energy into thermal energy; the temperature controller is used to control the water temperature; the magnesium rod mainly plays a role in protecting the inner tank and reducing corrosion; and the safety valve ensures the safety of the water heater during use.
Resistive Heating Process: When the electric water heater is connected to the power supply, the electric current passes through the electric heating elements. Since the electric heating elements (usually made of metallic alloy materials with high resistance, such as nickel-chromium alloy) have a certain resistance to the electric current, according to Joule's law (, where ?is the heat, ?is the current, ?is the resistance, and ?is the time), the electric current does work on the resistance, and the electrical energy is converted into thermal energy, causing the temperature of the electric heating elements to rise.
Heat Transfer and Water Temperature Rise: After the temperature of the electric heating elements rises, the heat is transferred to the water in contact with them through heat conduction. As the water absorbs heat, its temperature gradually increases. Since the density of hot water is lower than that of cold water, hot water will rise and cold water will sink, forming natural convection inside the storage tank, thus gradually making the water temperature inside the tank more uniform.
The Function of the Temperature Controller: The temperature controller monitors the water temperature inside the storage tank in real time. When the water temperature reaches the preset upper temperature limit, the temperature controller will automatically cut off the power supply and stop the operation of the electric heating elements to prevent the water temperature from being too high. When the water temperature inside the storage tank drops to a certain temperature (the preset lower temperature limit) due to the use of hot water or natural heat dissipation, etc., the temperature controller will automatically connect the power supply again, making the electric heating elements work again to heat the water to the preset temperature.
Working Principle of Dual Heating Elements (for Some Electric Water Heaters): Some electric water heaters are equipped with upper and lower electric heating elements. In the initial stage of use, the upper electric heating element works first, giving priority to heating the water in the upper part of the storage tank to meet the user's need for quickly obtaining hot water. When the water temperature in the upper part reaches the preset temperature, the upper temperature controller will cut off the power supply of the upper electric heating element and connect the power supply of the lower electric heating element to continue heating the water in the lower part of the storage tank, so that the water temperature throughout the storage tank can reach the preset temperature, improving the heating efficiency and the utilization rate of hot water.
Protection Principle of the Magnesium Rod: During the heating process, calcium, magnesium and other ions in the water will deposit on the surface of the inner tank to form scale, and the dissolved oxygen in the water will also corrode the inner tank. The chemical properties of the magnesium rod are more active than those of the metal of the inner tank, and it will preferentially react with the dissolved oxygen and other corrosive substances in the water, thus protecting the inner tank from corrosion and extending the service life of the electric water heater.

Through the above series of working processes, the electric water heater realizes the conversion of electrical energy into thermal energy, providing users with stable hot water at an appropriate temperature.

Anatomy of Electric Heating Elements:
The electric heating elements are the main components of an electric water heater and play a crucial role in heating the water. Understanding their design and functions is key to diagnosing and resolving potential issues. These elements are usually rod-shaped and located inside the storage tank, consisting of several core components:
Metal Sheath: The outer layer of the element is a metal sheath, typically made of copper, stainless steel, or nickel alloy. This sheath encloses the heating element, providing a robust barrier against the corrosive environment inside the water tank.
Resistance Wire: Inside the sheath is the resistance wire, usually made of nickel-chromium alloy. The wire is the core of the element, where electrical energy is converted into heat energy through resistance. When an electric current passes through this wire, its natural resistance generates heat, which is then transferred to the water.
Insulation: There is an electrical insulation layer around the resistance wire, usually made of magnesium oxide. This insulation is highly effective in conducting heat but prevents electrical contact with the sheath, ensuring safety and efficiency.
Termination Points: Both ends of the heating element have termination points where electrical connections are made. These points protrude from the top of the water heater tank and are where the power supply is connected.
Thermostat and Safety Switch: Each element is regulated by a thermostat, which controls the temperature by switching the power supply to the element on and off. The safety switch (high limit switch) is integrated to prevent overheating and will cut off the power supply if the water temperature exceeds the safe limit.
Understanding these components is essential for diagnosing problems with the heating elements. Issues are usually caused by the failure of one or more of these components, such as a burned-out resistance wire or corrosion of the sheath, resulting in low heating efficiency or complete failure.

Common Issues with Electric Heating Elements:
The heating elements of electric water heaters often face several common malfunctions due to their working environment:
1.Burnout: Excessive current from unstable voltage or long-term use can cause the resistance wire in the heating element to burn out, making the water heater unable to heat and possibly tripping the circuit.
2.Insulation Damage: Erosion by water, high-temperature aging, or external damage can damage the insulation layer, leading to electric leakage and short circuits.
3.Sheath Corrosion: The metal sheath may corrode due to chemicals in water. Severe corrosion can cause perforation, bringing safety risks and affecting heating.
4.Terminal Issues: Loose or oxidized terminal connections increase resistance, causing problems like slow or intermittent heating.
5.Thermostat-related Problems: A faulty thermostat can make the heating element overheat or fail to start properly.
6.Efficiency Drop: Scale accumulation on the heating element reduces its heat transfer efficiency, slowing down water heating and wasting energy.