Induction boiler is the best source of electric heat for heating systems

Recommendation points

• Induction boiler history
• Device and principle of operation
• Induction boiler characteristics
• How to install an induction boiler
• How to choose an induction boiler

In this article: History of the creation of induction boilers; the principle of operation and the device of the boiler; pros and cons of induction boilers; how to install a boiler in a closed heating system; selection of an induction boiler.

Organic fuels, such as wood, coal, oil products and natural gas, make up the main group of energy carriers on earth used to heat our homes and apartments. However, any of its varieties has two serious drawbacks, and the second one is especially critical at the household level – once there will be no organic fuel at all due to full production, it is extremely difficult to get it in some regions of the CIS for whatever reasons. And in such a desperate situation, homeowners turn to heating electric boilers, and their choice lies between boilers with heating elements and boilers with thermal electric heaters – i.e. there is no choice as such. But there are also electric induction boilers, and their operational characteristics are quite high …

Induction boiler history

From about 1822 to 1831, the brilliant English scientist and researcher Michael Faraday conducted a series of experiments with the aim of converting magnetism into electricity. And only at the end of August 1831, another Faraday experiment gave the result that the scientist hoped for – having received an electric current in a primary wire winding wound on a round iron core, he discovered electromagnetic induction.

Michael Faraday’s discovery was originally used in transformers, generators and motors, but it became really in demand only 70 years later – from the beginning of the 20th century, the pace of industrial development demanded new methods of melting metals in a workshop. And the first induction smelter was opened in Sheffield, England, in 1927.

In the 80s of the XX century, induction boilers were created, which were used for heating in industrial enterprises, including in the USSR: the first type consumed current with a frequency of 50 Hz, the second – with a frequency of 1 kHz and above. The dimensions and weight of industrial induction boilers are quite impressive, the coolant in them circulates through a secondary winding of pipes placed on top of a metal core with a primary winding. Serial models of induction boilers intended for domestic heating systems and differing from industrial analogs in much smaller size and weight, appeared in Russia in the 90s of the last century.

It should be noted that the physicist-inventor Nikolo Tesla has no direct relation to the induction boiler – except perhaps by the discovery of alternating electric current.

Device and principle of operation

The body of an induction boiler is multilayer – a core with a double wall, then a layer of electrical and thermal insulation, then an outer (outer) body. Unlike industrial induction boilers with a cylindrical winding, in domestic boilers, a toroidal copper wire winding is used, made between two ferromagnetic steel pipes welded to each other with a wall of more than 10 mm, the inner diameter is less than the outer diameter. As a result, lower weight, higher efficiency and small dimensions of the boiler are achieved in comparison with industrial analogues. The inner tube with a toroidal winding acts as a core (magnetic circuit), the inner tube is a heating element for the coolant.

The coolant, water or antifreeze, enters the boiler through an inlet pipe welded through both metal pipes. Due to the large internal area of ​​the inner tube-heat exchanger, the heat carrier receives about 98% of the thermal energy generated by the induction boiler, and in a shorter time than heating with heating elements, due to the lower inertia. The induction current generated by the high-frequency magnetic field from the outer winding to the inner pipe causes heating of the coolant, while the vibrations of the walls at high frequencies prevent scale from accumulating on the metal walls. The outer electrical and heat-insulating layer provides complete protection against possible electric current leaks and heat losses.

An alternating current under voltage, the frequency of which is about 20 kHz, is supplied to the boiler from a semiconductor inverter converter. In addition to the inverter, the inverter boiler package includes an electronic thermostat (a temperature sensor is built into the boiler body) and circuit breakers.

Heating of the coolant in an induction boiler occurs due to the heating of the steel core by eddy currents caused by the electromagnetic field generated by the high voltage current. When the boiler power is connected, the following occurs – a high-voltage current flows to the primary toroidal winding of the boiler, the resulting electromagnetic field presses the eddy currents into the outer surface of the steel core, their density increases and the core pipe heats up first from the outside, and then completely. The heat generated by the boiler is absorbed by the heat carrier circulating through it and delivered to the heating devices. It takes about 7 minutes to heat the core of an induction boiler to an operating temperature of 75 ° C.

Induction boiler characteristics

This type of heating boilers has a number of advantages over traditional heating elements, but it also has disadvantages, including those specific only for such boilers. Let’s take a closer look at the pros and cons of induction boilers, starting with the positive characteristics:

• complete absence of any heating elements, as well as moving and highly loaded elements that are subject to wear during operation and require periodic replacement;
• the ability to operate from a low voltage and constant current power grid, which is usually unacceptable for other types of electric boilers;
• the boiler structure does not contain detachable connections, i.e. the probability of leakage is completely excluded;
• significantly faster heating to operating temperature, compared to any other types of electric heating boilers;
• protection against scale formation *;
• high fire (class II) and electrical safety, since the heating element (core) is not electrically connected to the inductor (primary winding) directly, and the temperature difference between the core and the coolant does not exceed 30 ° С;
• the boiler design does not require the installation of a chimney;
• there is no need to install the induction boiler in a separate room;
• Like any electric heater, the efficiency of such a boiler is close to 100%. By the way, this value does not change over the years of its operation, unlike boilers with heating elements and electrode;
• the average service life is 25 years and more (depending on the thickness of the metal pipes forming the boiler core), and no maintenance work is required with this equipment;
• allows you to use almost any coolant in the heating system (water, antifreeze, oil, etc.), and without any preliminary preparation;
• replacement of the spent coolant in the heating system is carried out once every 10 years;
• absolute noiseless operation;
• low inertia, which saves energy due to efficient control of the boiler operation using electronic automation **. It should be noted that the inertia of induction boilers is lower than that of heating elements, but higher than that of electrode boilers;
• boiler installation does not require the involvement of highly qualified specialists;
• it is allowed to use for any closed heating systems, including for “warm floor” and for baseboard heating – the minimum threshold for the heating medium heating temperature is 35 ° С.

* – scale deposits on the inner surfaces of the core pipe are not formed due to the small temperature difference between the heater and the coolant, not exceeding 30 ° C, as well as due to high-frequency vibrations caused by eddy currents that repel salt ions from the inner walls of the pipe.

** – electronic control of the induction boiler provides less energy consumption by maintaining the temperature at a strictly specified level, i.e. when it rises, the power supply to the boiler is immediately turned off and resumed only when the temperature drops below the user-specified temperature.

It should be noted that the maximum allowable pressure in a heating system with heating of the coolant from an induction boiler should not exceed 0.3 MPa.

Cons of induction boilers:

• significant size and weight. For example, a 2.5 kW single-phase boiler, with a height of 450 mm and a diameter of 121 mm, weighs 23 kg;
• high cost – from 30,000 rubles. and higher. In part, the price of induction boilers is due to the presence of an inverter starter in the control system, which is not cheap in itself;
• installation only in closed heating systems;
• during operation, depending on the power of the boiler, interference is generated in the long-wave, medium-wave and VHF radio ranges at a distance of several meters from its location, which cannot be completely screened. However, this has no effect on the human body, only domestic animals (dogs, cats) are able to feel them..

How to install an induction boiler

Installation of such boilers is allowed only in a closed heating system equipped with a forced circulation pump and an expansomat expansion tank. The induction boiler is positioned strictly vertically, the return pipe of the heating circuit is connected to the inlet pipe (depending on the model, located at the bottom or side, in the lower part of the body), and the supply pipeline is connected to the outlet pipe (located in the upper side of the body or from above). The induction boiler is fixed to the wall using fasteners that can support its own weight and the weight of the heating medium that fills the boiler during operation. The distance from the boiler body to any nearby object, walls, ceiling and floor must be at least 300 mm on its sides, at least 800 mm – from below and from above.

During installation work, the induction boiler must be grounded. Strapping with metal pipes is not required, you can connect the metal-plastic pipes of the circuit directly to the boiler nozzles. A safety group is built into the section of the pipeline located not far from the boiler outlet pipe – a pressure gauge, an automatic air vent and an explosive valve. The shut-off valves can be installed in the heating circuit after the safety group placement points, the expansomat tank – in the return section. After the point where the expansomat is placed and before the return pipeline is inserted into the induction boiler, a settling filter, a coarse mesh filter, a circulation pump and a flow sensor are sequentially built into the circuit (allows you to control the flow of the coolant along the return circuit, its flow into the boiler). The control system of an induction boiler is installed according to the rules of the PUE and is connected to the boiler according to the diagrams given in its technical passport.

How to choose an induction boiler

On the Russian market, there are mainly single- and three-phase induction boilers of two domestic manufacturers – LLC “Alternative Energy” (brand “VIN”) and CJSC “NPK” INERA “(brand” SAV “), with a capacity of 2.5 to 7 kW ( single-phase) and from 7 to 60 kW (three-phase).

In addition to the mandatory elements, which are equipped with a heating system with an induction boiler, and to facilitate its control, it is allowed to complete with an electronic programmer unit for boiler operating modes for one week or a programmer that allows you to control the operation of the heating system remotely via a GSM channel.

Considering that the power of induction boilers does not decrease over the years of operation, the selection of the required model is made at a ratio of 60 W per m² area to be heated. For example, for premises with a total area of ​​20 m² you need a boiler with a capacity of 3 kW. To accurately calculate the required boiler power in relation to a specific building, it is necessary to involve specialists who will assess the degree of insulation of the premises in it..

The warranty period for induction boilers is 3 years for the boiler itself and a year for the electrical equipment of the cabinet with which it is completed. The defining moment in the duration of the trouble-free operation of such boilers is the thickness of the steel inner pipe-core – the thicker its wall, the longer it will be able to withstand corrosive processes. The optimum wall thickness of the core pipe is 10 mm.

The convenience of using electric induction boilers also lies in the ability to maintain the optimum temperature in buildings that are visited by the owners from time to time. In this case, a particularly powerful model will not be needed, since even a 6 kW boiler is able to maintain the temperature in a house with an area of, for example, 120 m² at the level of 12-15 ° С. And since a country cottage usually has a fireplace, then by melting it, you can easily and quickly raise the temperature maintained by the induction boiler to a comfortable level, which would be impossible in an unheated building.