The use of inverter heaters in heating

Among the many types of heating devices there are units called inverter. Consider what it is, and what kind of heating device can be given such a definition.

What is an inverter

An inverter is a device that converts direct current into alternating current or increases the value of voltage, frequency of alternating current. The need for such a transformation arises when creating devices and mechanisms with a sensitive system of settings that respond to the slightest change in the parameters of the environment. Inverters are used in many areas: electric welding (in fact, a welding machine is a kind of inverter), control of electric motors and electric drives, production of air conditioners and heaters, etc.

As an integral part of the device, the inverters look different and may not have an individual case.

The use of inverters in heating

In the production of heating appliances, inverters are used as a device that allows precise pre-setting or adjustment during the operation of the unit.

High-tech electrical heating devices that do not have heating elements, lamps, filaments and heating coils in their design necessarily include inverters as devices to increase the functionality and efficiency of the heating unit. Such means of heating include vortex induction heaters (VHE) and inverter air conditioners. Both of these devices originated from their less advanced predecessors: VIN — from induction boilers of the SAV type, inverter split systems — from conventional air conditioning systems.
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VIN heating boilers

A wine boiler is a unit for equipping housing with a heating system and, depending on the model, hot water supply. The device runs on electricity and uses the phenomenon of electromagnetic induction, known for more than 100 years, discovered by Faraday, to heat water.

Simplified, a water-heating boiler is a vertically mounted cylindrical metal body equipped with two fittings for water inlet and outlet. Inside the case there is a primary winding (coil) — turns of an insulated conductor, the ends of which are energized. A secondary winding (core) is placed in the coil without contact with it, which is a section of the pipe of the heating system itself with a coolant.

When voltage is applied to the ends of the primary winding, an electromagnetic field is induced around the coil, which causes the formation of Foucault eddy currents in the upper layers of the core, heating its surface with subsequent transfer of this heat to the coolant.

The VIN-boiler differs from SAV-devices in that a current is supplied to the ends of the primary winding, the frequency of which is several times increased by the inductor included in the design of the unit. The high frequency of the electric current causes the emergence of an electromagnetic field around the primary winding of a larger strength value, which, accordingly, causes the appearance of vortex flows of greater power in the secondary winding.

The primary and secondary windings of the VIN-unit are made of various ferroalloys with different values ​​of their own magnetic field. These magnetic fields, interacting with the induced electric field, contribute to the heating of the core.
Thus, the combination of these factors increases the intensity of heating of the upper layers of the secondary winding, but reduces its depth, accelerating the process of heat transfer to the coolant and reducing the time for the heating system to reach a given power.

A more advanced design of VIN-boilers causes a higher price compared to other induction devices.

Inverter air conditioner-heater

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The simplified household name of such devices «air conditioner» is misleading regarding the functionality of these units. Indeed, one of the functions of this device is to lower the air temperature in the room to a predetermined value in the summer. However, the unit can also perform the opposite function — to heat the room in the cold season.

Device and principle of operation

To understand the principle of operation of an inverter heater, consider the operation of an air conditioner without an inverter in the design, but still a modern design that does not use air from the street. The inverter heater has the same algorithm of action, only improved.

The principle of operation of both of these devices is based on the release of heat by the gas during compression and cooling by the liquid of the surfaces in contact with it during evaporation. The gas that performs this role in air conditioners is called the refrigerant.

Refrigerant properties

As a refrigerant in split systems, a fluorine-containing compound is used — freon, which can be more than 40 types. We list the 3 most common types of freon:

• R-22 is not an effective refrigerant at temperatures below -5 and above 40 degrees (boiling point -41 degrees), due to the increased harmful effect on the ozone layer, it is prohibited for use in Russia;
• R-410A — a substance (boiling point -51 degrees) of less negative impact on the ozone layer, effective for use in the temperature range from -15 to +45 degrees, used in most air conditioning systems;
• R-32 is a safe new refrigerant (boiling point -52 deg.), with an efficiency of use 5% more than R-410A.

Important! When buying an air conditioner of any type, especially a used one, it is necessary to exclude the possibility of buying a device on R-22 refrigerant, due to the prohibition of using it, which has become a shortage, which, if the device needs to be charged, cannot be replaced by another type of freon.

Functions of the constituent units of the air conditioner

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A modern air conditioner, called a split system, consists of two blocks. Such a division into two components made it possible to remove a noisier and, moreover, bulky block from the room, leaving a compact and, as a rule, aesthetically executed unit inside. Freon is moved by a pump located in the outdoor unit.

The principle of interaction of split system blocks

The indoor unit of the split system contains a heat exchanger (condenser). In the mode of operation of the air conditioner for heating, freon is compressed in the heat exchanger, during which its temperature rises. The temperature of the compressed refrigerant reaches 80 degrees, and the heat is transferred to the room through the circulation of room air through the heat exchanger. After the release of heat, the compressed freon passes into a liquid state (condenses) and moves to the outdoor unit — to the evaporator, the pressure in which is ten times lower. A sharp decrease in pressure leads to the boiling of the refrigerant while simultaneously absorbing heat from the environment. The boiling point of liquefied freon (depending on the type) with a large pressure drop is several tens of degrees below zero, that is, the outside air at a temperature of even -15 degrees is still warmer. Therefore, the absorption of heat by boiled freon occurs even from frosty air, and the lower the tabular boiling point of the refrigerant, the colder it is able to take heat from the colder air.

At the end of boiling, the refrigerant that has absorbed heat from the air returns to the indoor unit and is compressed again, condensing, heating up and heating the heat exchanger.

Design details of the process

Compression of the refrigerant with the release of heat and evaporation with its absorption occur not in some chambers, but in two coils located in the outdoor and indoor units. After being compressed by the pump in the coil of the indoor unit, freon enters the outdoor unit through a tube of very small diameter (capillary), but the narrowness of the outlet of the capillary tube prevents the filling of the outer coil (evaporator) and causes the freon to evaporate with the absorption of heat from the environment.

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Briefly, the heating process can be described as a chain of four successive processes: compression of the refrigerant — heat release — boiling (evaporation) of the refrigerant — heat absorption.

If the process is started in the opposite direction, then the roles of the condenser and evaporator will be reversed, and the air will be cooled in the room.

Split system operation algorithm without inverter

A conventional air conditioner can only be in two states — on or off. Before turning on, the required air temperature in the room is set on it, then it is started, and the compressor starts to drive the refrigerant through the system. The split system temperature sensor controls the air temperature in the room and compares it with the set value. As soon as these values ​​are equal, the compressor will be automatically turned off, and the split system will remain inactive until the difference between the actual and maintained temperatures in the room reaches 2-3 degrees. After that, the compressor will start up again at full capacity on a signal from the thermostat.

The imperfection of the algorithm is obvious — turning on the system at full capacity without reference to the upcoming volume of work, which creates a short-term, but excessive load on the power grid. In addition, it is at the moment of start-up that the wear of equipment components and power consumption are maximum, since starting the rotation of the rotor of a conventional, non-inverter compressor requires large starting currents.

Inverter split system

The actions of an inverter-type air conditioner-heater are identical to the behavior of a conventional split system until the moment when, after the device is first turned on, the temperature in the room has reached the set temperature, and this value must be maintained — to heat the air or cool it, depending on the operating mode of the unit.

From this moment on, its operation algorithm differs from the unit without an inverter. The compressor of the inverter split system does not turn off, but continues to work, but not at full capacity, but within 5% of the potential. Consequently, the inverter heater operates constantly, without using the on-off cycle, smoothly adjusting the intensity of work (compressor speed) for the optimal mode of maintaining the specified temperature conditions. When using inverter split systems, temperature fluctuations in the room are within one degree, in contrast to the spasmodic provision of temperature in steps of 2-4 degrees with conventional air conditioners.

Characteristics and classification

The main characteristic of inverter air conditioners-heaters is power, moreover, of two types — consumed and useful. Given the ability of these units to regulate the speed of the compressor, these characteristics are indicated in the form of ranges. For example, a useful power of 0.5 — 5.1 kW indicates its minimum and maximum value.

Important! It should be taken into account that the upper value of the range of the indicated power exceeds its nominal value, since modern inverter heaters-air conditioners can, if necessary (quick heating or cooling of the room), operate in excess of the nominal value for a short period.

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In addition to power, inverter units are divided depending on the refrigerant used, an important characteristic of which is the boiling point — a criterion for the possibility of using the device in heating mode (the lower the boiling t, the lower the outside temperature, the system can be operated as a heater).

By execution, inverter air conditioners are divided into:

• wall;
• subceiling;
• floor.

Classification by design features and functionality:

• cassette;
• channel.

Important characteristics of inverter air conditioners also include noise level, dimensions, power supply parameters, etc. As a rule, all these data are indicated by the manufacturer in the technical data sheet of the product and the instruction manual.

For clarity, we present a comparative table of technical characteristics of four models of McQuay M5MSY-BR inverter split systems, since a detailed description of all the parameters of such high-tech devices in everyday life is rarely required.

Areas of use

Inverter air conditioners-heaters are used where the level of comfort is important. If the room is used infrequently and not for a long time during the day, then in such rooms you can limit yourself to installing a conventional split system, modern models of which also have high technical characteristics.

If it is a children’s room, a bedroom or an office, the comfort of a long stay in which must be ensured by definition, then the best choice would be an inverter device, the higher price of which is justified by greater functionality and integrated economy.

Advantages

This type of air conditioning and heating systems is promising and is constantly being improved. The newer the model, the higher its technical characteristics, so we list and comment on the advantages inherent in all inverter air conditioners-heaters and declared by marketers:

• Profitability — inverter units are 30% more economical than classic ones, but given the high cost of these devices, the payback period for the price difference is about three years, and with short-term use this time increases.
• Low noise level — confirmed, but this parameter is not achieved using an inverter, but depends on the models of compressors, drives and fans.
• Durability — is present only with a high-quality compressor, proper installation of a split system and careful maintenance of it (if these requirements are not met, both classic devices and inverter ones, containing additionally several electronic boards, fail equally quickly);
• The accuracy and smoothness of maintaining the temperature is confirmed only in the absence of such external factors as opening windows, doors or turning on household appliances, the operation of which is accompanied by heating (computer, oven, etc.).

Disadvantages of inverter heaters

• High relative to conventional units, the price, which increases with the growth of the perfection of models.
• The high cost of components if repairs are needed.
• Sensitivity to the parameters of the consumed electricity.

Conclusion

And yet, with proper installation and operation, inverter air conditioners will provide a higher level of comfort in the room than classic units can do. The categorical enthusiastic statements of marketers also contain a share of reliable information.