The principle of operation of an electric water heater

To comprehend the functioning of a water heater, it is essential to grasp its design and identify its key components. In reality, the concept is relatively straightforward. A classic electric storage water heater consists of the following elements:

  • External case (most often steel)
  • Thermal insulation. A layer, typically made of polyurethane foam, is placed between the inner and outer tanks to ensure long-term temperature preservation.
  • Internal tank. One or two depending on design
  • The heating element. Responsible for heating the water in the tank and can be either dry or wet.
  • Thermostat. Mechanical or electronic. A device for controlling and adjusting the water temperature and timely automatic shutdown of heating
  • Magnesium anode. There may be several, which protects the inner coating of the tank from corrosion. It is a consumable component that needs periodic replacement.
  • Connection pipes for intake of cold water and distribution of hot water
  • The thermometer is installed for visual monitoring of the water temperature. There are analog and digital options
Water heaters with magnesium anode

Water heater with one tank operates based on the following principle. After installation and connecting it to the water supply and electricity, the internal tank is filled with water, and the heating process begins using the heating element. This process typically takes several hours and stops once the temperature set on the thermostat is reached. As hot water is used and depleted, it is replaced with cold water, leading to a decrease in temperature. The thermostat then activates the heating element again to heat the water back to the desired temperature.

There are models with one tank and two heating elements, which allows you to increase the heating efficiency due to high power. Most often, 1.5 + 1 kW heating elements are installed, which can be activated simultaneously or alternately, depending on the need.

But in the case of two internal tanks, the principle of operation changes, several heating options appear. Water from the first tank overflows into the second tank, from where it is distributed to the water outlets (kitchen faucet, bathroom faucet). This setup often incorporates two independent heating elements to ensure efficient heating. Additionally, some models include a combined heating unit in the output tank, allowing for up to three heating modes.

In mode 1, the heating element in the output tank is switched on first to quickly provide hot water in small quantities for immediate use, such as taking a shower or washing dishes. Once the desired temperature is reached, the first heating element is turned off, and the second heating element, located in the input tank, is activated. In mode 2, both heating elements are turned on simultaneously, suitable for households with a high demand for hot water, especially when multiple outlets are being used simultaneously or in quick succession. There is also a mode 3, facilitated by the combined heating element in the output tank, which allows for urgent heating and continuous hot water supply during usage. However, this mode requires high energy consumption and requires enhanced electrical wiring.

Due to the separation of containers, the volume of water that needs to be heated is reduced, and the total volume remains unchanged, so water heaters with two tanks reach the set temperature faster.

Double-tank water heaters

Advantages and disadvantages of one or more tanks

Differences in design, principle of operation, heating modes make it possible to highlight the features of water heaters with 1 or 2 tanks and optimize them for certain operating conditions.

Advantages of single tank:

  • Affordable price (on average $200 for 80 L)
  • A wide range
  • There are models with large volume(more than 500 liters)

Disadvantages of single tank

  • After switching on, it heats all the water in the tank, so it is difficult to get the right amount quickly
  • Usually equipped with one heating element, so if there is a breakdown, there will be no hot water at all

Advantages of two tanks:

Disadvantages of two tanks:

  • High price (average $330 for 80 L)
  • Limited volume (usually no more than 100 L)
  • Simultaneous operation of heating elements creates an increased load on the wiring

Which water heater is better — with one tank or several?

There is no universal answer to this question and there cannot be. What is good for one is bad for another. It all depends on the purpose and operating conditions.

Water heaters with a single tank have a larger variety of options available on the market, making them more popular among consumers. Additionally, their price is generally more affordable compared to other types of water heaters. These single-tank models come in various shapes, such as cylindrical, rectangular, and even narrow designs, allowing for flexible installation options to fit different room dimensions.

When would one tank be better? A single tank water heater is preferable when fast heating is not a priority. It can effectively meet the hot water needs of a household, regardless of the number of occupants. It is particularly suitable for individuals who prefer taking full baths. However, constant maintenance of the temperature may result in higher energy consumption, negating potential savings. For households with 1-2 people, a 30-50 liter tank is generally sufficient for showers and regular use. Larger families (3-4 individuals) would benefit from a tank with a volume of 100+ liters. Some individuals may opt for an 80-100 liter tank, using water sparingly over several days to achieve savings.

Rectangular water heaters

Larger volumes of 500+ liters in a single tank water heater can cater to the needs of small gyms or kindergartens. If budget constraints exist and installation space is not limited, a single tank water heater is a cost-effective solution. For small applications like holiday homes, opting for a smaller tank volume makes sense to avoid unnecessary expenses. These water heaters are typically low-power (around 1 kW), ensuring they do not overload the wiring. Their fast heating capability enables electricity savings, which can be significant in areas where electricity costs are high, such as country cooperatives.

The dual tank design is effective where space is limited because all models are flat. In fact, inside are cylindrical containers, but smaller. Due to the high heating rate, such models are best suited for a large family (3 — 4 people) who do not want to install a huge cylindrical water heater of 150+ liters. The principle of operation of the water heater with two tanks also saves energy. With reduced consumption, it is possible to use only the heating element of the output tank, quickly getting hot water in small volumes.

If you want to automate the operation of the water heater, then programmers and automatic Smart modes will help. They are present in models with one and several tanks, offering the ability to customize the water heater's operation based on the user's schedule. This is the best option for those who often work on a fixed schedule (4/4, 5/2, 7/7) and consume hot water only on certain days / hours.

Water heaters with automatic mode

Whatever electric water heater you choose, do not forget about the rules of operation, periodic maintenance. Then your investment will pay off with a vengeance. You can find out how to properly install, use and maintain the water heater in this article.