Double-circuit electric boiler - features, pros and cons

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Published: 02.06.2019

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A double-circuit electric boiler is a popular type of heating equipment and has a lot of advantages. It is customary to install it in rooms remote from the centralized gas and water supply in order to heat the building and supply hot water. Before purchasing a unit, you must carefully study the principle of its operation and performance characteristics.

• 1 Types of double-circuit boilers
• 2 Design and principle of operation of the electric boiler 2.1 Connection diagram

What are double-circuit electric boilers

Double-circuit electric boilers are almost always wall-mounted models, which, with the same technical characteristics and previous or slightly large dimensions, combine the functionality of two devices at once - the heating boiler itself and a flow-through (less often storage) water heater. The heating medium from the heating circuit is never mixed with sanitary water in the hot water supply (DHW) circuit.

Two-circuit electrical models are best used in small residential buildings with an area of ​​up to 150-200 m2. And it's not only about high operating costs, but about the length of the pipeline from the boiler to the points of consumption, which should not exceed 8-10 m, otherwise it will be possible to get hot water in more than 20 seconds after opening the tap.

Wiring diagram for a double-circuit electric boiler.

If you do not take into account the high cost of electricity, double-circuit hot water electric boilers are ideal boilers, because, unlike other types, they are easy to install, do not require a chimney and ventilation, are not demanding on the parameters of the room, are reliable and functional. Only models with a capacity of more than 10 kW require approval from the Energy Supervision Authorities.

It is also worth considering that models with a power of over 6 kW must be connected to a three-phase (380 V) power grid, a single-phase (220 V) network will not be enough to provide higher power.

How to calculate how much electricity an electric heating boiler consumes

Device and principle of operation

The device of a double-circuit electric boiler using the example of SAVITR Premium.
Electric double-circuit boilers differ from single-circuit boilers only by the presence of a heat exchanger in which sanitary hot water is heated, as well as by means of capacity distribution between the circuits. All models have exactly the same basic device: the heating unit of the heating circuit, which contains the heating elements and the DHW heat exchanger, in which the water is heated.

Almost always, the housing already from the factory contains all the necessary elements and assemblies of the heating system: an expansion tank, a circulation pump, an automatic air vent, a safety valve, a pressure gauge, a set of sensors, etc. This means that in order to install and connect the boiler to the system, it is enough to bring the heating supply and return lines, hot water supply and a source of sanitary water (for example, water supply) to it.

To clearly understand the principle of operation of double-circuit boilers, consider how each circuit works separately:

• heating - the primary circuit, the coolant continuously circulates in it, warming up in the heating unit and giving off heat through radiators installed throughout the house;
• water heating - it is activated only when the hot water consumption point is opened, directs the heating agent of the heating circuit to the DHW heat exchanger, by means of the contact heats it, and therefore the sanitary water inside.

In double-circuit electric boilers, the distribution of power between the circuits is carried out using a three-way valve, therefore not all power is given to heating hot water, which allows maintaining the temperature in the main heating circuit.

For models with a flow-through heating principle, a delivery delay of about 5-15 seconds is characteristic, however, there are models with a built-in boiler with a volume of 50-300 liters, in which the water is constantly heated. This allows not only to minimize the delay in the supply, but also to provide a certain supply of already prepared hot water, leveling the low performance of DHW.

How to save with an electric boiler

Since the main disadvantage of electric boilers is the price of electricity, and in other characteristics, this is perhaps the most attractive option for heating and hot water supply, the issue of saving electricity for these types of boilers is especially acute. Despite the widespread belief that heating with electricity is prohibitively expensive, with an economical approach, you can reach quite affordable costs with quite significant advantages.

There are a number of ways to reduce electricity costs when using these boilers:

1. Boiler selection. Electricity consumption depends on the type of heating element. They are of three types: heating elements (the most common), cathode and film. Heating elements convert electricity into heat using a spiral, cathode heating elements heat the coolant through the ionization process, film uses infrared rays for their task. The most economical are cathode ones, and heating elements are considered the most energy-consuming.
2. Temperature control and planning systems, programmers. A saving method that allows you to control the boiler power, set the desired temperature, including according to a given schedule, select the heating mode depending on the temperature outside the window, etc.
3. House insulation. This way will help with any heating, but the savings will be especially significant when using an electric boiler.

Do not forget about the savings from the very choice of an electric boiler. There are a number of factors that can be attributed to different types of savings when using electric heating:

• A simple solution for heating and hot water supply issues. When choosing an electric boiler for two circuits, saving time, effort, material costs associated with various communications associated with connecting another type of heating and hot water supply is obvious.
• Price. For a double-circuit electric boiler for heating a house, the price is almost always more attractive than for other types of heating equipment.
• Service cost. Such boilers have a very simple design, rarely fail and require minimal maintenance. It is enough to buy such a heating boiler, and installation and use in most cases will not cause trouble.
• Saving space. A striking example is an electric double-circuit wall-mounted boiler, which takes up almost no space, and meanwhile solves the serious problems of heating and uninterrupted supply of hot water.
• Caring for the health and tranquility of residents. A high level of safety, cleanliness at work, the absence of environmentally harmful waste, as well as silent work - all this protects the nerves and health of the homeowners, and it costs a lot.

Electric boilers have many advantages, with a competent approach, they are not as expensive as it might seem, and in any case they have the right to be a worthy alternative for equalizing the temperature when using other types of heating systems and as a backup option.

Reviews of household double-circuit electric boilers: advantages and disadvantages

Installation of electric boilers

For installation, only one thing is required: connection to a constant power supply, as well as water supply, if double-circuit heating is provided. Electric boilers usually serve for a long time and reliably. However, network surges have the potential to harm such equipment. For those who decide to buy an electric boiler for heating, before installation, it will be useful to make sure that there is an uninterrupted and uniform flow of electricity, to strengthen the wiring and ensure grounding.

If the issue with voltage interruptions is not resolved, when buying, you should pay attention to the readiness of the device to withstand such fluctuations, perhaps choose a more expensive imported model.

For example, many who purchased a Russian-made ZOTA electric boiler faced the failure of some elements precisely because of network outages. Domestic electric boiler ZOTA is equipped with an overheating sensor, but if operational requirements are violated, if the voltage in the network rises above 240 V, the boiler may overheat above the established norm.

How to choose the right model

Electric boiler type

Combining the functions of heating and hot water preparation is possible only in heating element models of electric boilers, where tubular electric heaters are used as heating elements. We would not focus on this point if it were not for the frequent mistakes of online stores or a play on words by manufacturers who designate electric boilers with nozzles for connecting an indirect heating boiler as double-circuit.

Heating elements are the most common among all electric boilers in general, but they also have a special unpleasant drawback - a tendency to form scale on the heating elements, which over the years leads to a decrease in efficiency by 10, 20 and even 30%, the boiler needs more electricity and time to heat up the same amount of coolant through the scale layer.

A layer of scale on the heating element due to the use of a hard coolant.

Electric boilers can be electrode: simpler and more reliable, not involving the formation of scale, but demanding on pipes, radiators, coolant and high-quality grounding.And also induction: reliable, used mainly in industrial areas, characterized by faster heating, with the possibility of using antifreeze as a coolant. But it is worth remembering that today neither electrode nor induction boilers exist in a double-circuit design: only heating elements.

Minimum required power

In a simplified form, the minimum required power of an electric double-circuit boiler for heating and water supply at home is calculated based on the rule of 1 kW for every 10 m2, we also recommend laying 25-30% of the stock. This method is more than enough for an average house (no or weak insulation, 2 bricks laying, ceiling height 2.7 m, climate zone of Moscow region).

For example, for the above-described average house with an area of ​​150 m2, the minimum required power of a double-circuit electric boiler is 150/10 * 1.3 (30% of the stock) = 19.5, that is, 20 kW.

In other cases, with high ceilings or a large glazing area, southern or northern climatic zone, individual correction factors are taken into account, which change the result by 5-30% up or down. You can accurately calculate the minimum required power using the calculator below.

Calculator for accurate calculations

The power of the electric boiler must provide the total heat output of all radiators, the power of which is calculated for each room separately (based on heat loss). Therefore, to obtain accurate data, use a calculator to calculate the minimum required power for each heated room separately and add up all the values ​​obtained to get the result for the whole house.

Automation functionality

The most energy-saving models are characterized by the presence of a programmer. It allows you to set a boiler operation pattern for a day or a week, for example, setting the temperature to 15 ° C for working hours when no one is at home or 19 ° C during sleep, which will significantly reduce energy consumption, up to 30-40%. If there is no built-in programmer, the same functionality can be provided with a room thermostat.

How to choose an external thermostat for an electric boiler and save up to 30% on heating costs every month

It is also worth paying attention to the number of heating elements and the smoothness of temperature control, models with at least 6 heating elements and temperature control by degrees will be more comfortable and economical.

Many boilers are equipped only with overheating protection, but it is good if, among such a small selection, you can find a model with frost protection and pump blocking. Otherwise, the choice is small and it makes no sense to highlight more criteria.

Calculation of boiler power

Like any boiler, a double-circuit one must be chosen taking into account the required power. According to the mind, you need to select it based on the heat loss of your home, which is far from always possible to calculate yourself. The crudest approach is to put 1 kW of power into 10 squares of your house.

But it is different if you are going to use the second circuit on a permanent basis. Based on the power of the boiler, the amount of hot water we release per minute depends. Here everything is easier. You need a minimum of 24 kW of power to be sure that you have enough hot water production. Typically, a boiler of this capacity is capable of emitting 12-14 liters of water per minute. This volume is just enough to take a shower or completely wash the dishes.

The best known manufacturers and models: characteristics and prices

SAVITR Premium 15 Plus

One of the most common models of domestic production among double-circuit electric boilers. Differs in the presence of a programmer, as well as a complete room thermostat and a remote sensor for outdoor temperature.It is worth noting the layout and build quality that are good for Russian production, the heating unit is wrapped with a layer of thermal insulation, which is clearly a plus. In practice, the boiler fulfills its tasks without any problems; there are practically no serious service complaints for almost 10 years of operation.

The only drawbacks are loud clicks of the switching relay, not the most compact dimensions, controversial design and a rather high price. Available in 9, 12, 15, 18, 21, 22 and 25 kW versions.

Cost: RUB 47,200-53,000

Kiturami KIB-12

Korean, slightly cheaper option with much more compact dimensions. The internal layout is pretty good, the heating unit is thermally insulated, there is even a water filter, which is clearly a plus in the case of heating elements. Due to the absence of mechanical switches, the operation of the boiler is practically silent. However, the build quality is controversial, many nodes and connections are plastic, which in the future inspires less confidence than in the case of the previous SAVITR Premium with threaded connections.

The disadvantage is also the extremely low performance of hot water supply, for the model under consideration with a capacity of 12 kW - 4.2 l / min, which is enough for the full operation of just one point of hot water consumption (with a weak opening of the tap, a maximum of two points).

Cost: RUB 43,600-52,000

ACV E-Tech S 160

The Belgian technological model is probably one of the best double-circuit electric boilers for a private house. It differs in floor-standing design and the presence of a built-in storage tank (from 99 liters in the younger version and up to 263 liters in the older one), while the dimensions are small, typical of most floor-standing boilers. The DHW performance (excluding the tank volume) is also high, more than 10 l / min for the 14 kW model. Boilers of the ACV brand are known in the market as extremely durable and trouble-free.

The only significant drawbacks are the huge price and small, minimum required functionality. Nevertheless, this can be solved by installing a climate controller in the boiler panel (optional) or by connecting a good programmable room thermostat, the possibility of connecting an external control in the boiler is provided.

Cost: 239,000-249,000 rubles.

Features of the device and work

The heart of almost any electric boiler is a heating element. It consists of internal heating elements, to which automatic units are switched. With their help, the heating agent is heated, which transports heat to the heating circuit. Electricity is supplied from single-phase and three-phase electrical networks. The efficiency of electric boilers is such that they almost completely convert electrical energy into heat: the efficiency of the devices is close to 99%.

How to save on heating

It doesn't matter how the dwelling is heated - by a boiler, stove or other equipment - sources that provide heat require prevention.

What affects the consumption of electricity by the boiler:

1. Contaminated devices are ineffective - the heat is released "into the pipe", because due to dirt there is a difficulty with the normal transfer of fluid in the system.
2. The pump will not function efficiently if there is not enough refrigerant in it.
3. Electrical converters should be flushed out as a lot of dust accumulates inside.

Experts recommend, in order to save money, set your mode in all rooms. So, at night, during sleep, you can lower the temperature of the system by 2-3 degrees. However, if a child lives in the house, the temperature in his room should be stable.

Air congestions form in batteries and underfloor heating, impairing the operation of the system and increasing the consumption of gas or electricity. Leaving your home for a while, you need to leave the system in working order, but set it to 15-18 degrees.

Prices for the boiler ZOTA 24 Lux

ZOTA 24 Lux

It is necessary to take care of window and door seals. Elastic bands lose their elasticity and cracks appear on them. Due to deformed seals, cold air enters the house and warm air comes out.

When using radiators or convectors, certain rules must be followed.

Not worth it:

• obscure the equipment with furniture or curtains that prevent the flow of infrared radiation from the device;
• to mount decorative screens on radiators that interfere with the normal heating of the building and the movement of air.

The disadvantage of using batteries is that they give off heat to the wall on which they are fixed. To avoid this, a heat-reflecting shield should be glued to the wall behind the radiator. Study brick corner fireplace on our website.

Criterias of choice

In the process of choosing a floor-standing or wall-mounted boiler, it is required to focus on the power of the device, because the quality of heating the room will depend on this.

When buying a device, you should also pay attention to the quiet operation of the equipment. A good boiler makes almost no sound, except for the circulation pump.

There are not so few criteria for choosing a device, but the most important are:

• power;
• layout solution;
• place for installation;
• automation.

If there is no room for a large size of equipment or you want to install a unit with a presentable look in the kitchen, then it is better to take a wall-mounted type of low power.

How to calculate power

To heat one square meter, 100 W of heat is required.

The formula looks like this:

P = S * K * 100,

where S is the area, k is the coefficient that determines the heat loss, based on the air temperature outside.

Many factors affect heat loss, so measurements are not always accurate.

They are true for a dwelling that has:

• rooms with a height of 2.5 m;
• medium thermal insulation;
• cold attic.

Factors that generally affect heat output:

1. The height of the premises.
2. Number of walls.
3. Area and type of window openings.
4. Thermal insulation level.
5. Insulated attic.

To calculate the capacity of equipment by volume, the following formula is used:

P = V * K * Δ T / 860,

where V is the volume of the house, K is a coefficient indicating heat loss depending on thermal insulation; Δ T is the difference between the desired temperature in the home and the temperature outside.