Household electric boilers are convenient in operation, efficient and inexpensive compared to gas or solid fuel units. To install such a heater, you do not need to build a chimney, draw up a permit, allocate space for storing firewood. The only serious minus - the price of electricity - is leveled by the night tariff. To organize electric heating, it remains to find out the last question - how to choose an electric boiler for heating a private house or apartment.
The most economical electric boiler is a myth
Electricity is much easier to convert to heat than other energy sources - natural gas, solid fuel, diesel fuel. Here are 3 simple examples of side heat generation when using electricity:
- the windings of any running electric motor always heat up;
- a light bulb (even an LED) generates heat with the light;
- even the wires through which current flows are heated.
Note that the listed equipment is designed to perform its functions, and not to heat the house. The engine rotates something, the lamp shines, the wiring supplies them with energy. The formation of excess heat is a side effect that occurs due to the resistance of these elements.
To convert all electrical energy into heat energy, it is enough to create a section of high resistance in the circuit, which itself will not be destroyed by heating. Such an element is called an electric heater. The second (more complex) way to get heat is to create Foucault induction eddy currents that heat a metal object in the area of the coil-inductor.
An important point. Regardless of the conversion method, 98–99% of electricity will turn into heat. That is, any electric heating device works with an efficiency of 98–99%, no less. This means that the most economical electric boiler does not exist, all units are equally efficient. Whatever sellers of household appliances claim.
Heat generator selection by power
To pick up the power of an electric boiler, first of all, calculate the heat loss of your home. You probably know the approximate calculation method: for heating 100 square meters of the building area, a heating unit with a capacity of 10 kW is taken, 20 kW for 200 m² and so on. If you want to get a more sane result, use our calculation methods.
Now we define the tasks that the electric boiler should solve (select the desired item on the list):
- round-the-clock heating of the apartment, cottage, country house;
- the same with heated water for household needs;
- night work at a cheap rate;
- standby heating - maintaining air temperature + 5 ... 10 ° C.
Note. Night heating at home with an electric boiler can be combined with heating the heat accumulator. At 7.00, the unit shuts off, then the water system receives the heat accumulated in the buffer tank. 2 conditions: the allocated limit of energy consumption should be 15 ... 20 kW + powerful electric boiler.
Full-fledged heating with electricity is expensive and is applied as needed. A more profitable option is night heating from 23.00 p.m. to 7.00 a.m., when the cost of energy is half that. Standby mode is used at facilities under construction or dachas, where the owners spend 2-3 days weekly.
We select the power of an electric heating boiler, depending on the tasks:
- For round-the-clock operation, the unit is selected with a margin of 10 ... 20%. That is, the figure for heat loss is multiplied by a factor of 1.1–1.2. For example, a house with an area of 60 squares loses 4 kW, the electric boiler performance will be 4 x 1.2 = 4.8 kW.
- Under hot water supply (DHW), the unit's capacity should be increased by 50%. That is, multiply the 4 kW figure from the example by a factor of 1.5 (we get 6 kW).
- An electric heating apparatus for night heating can be taken without a power reserve if in the morning it is replaced by a gas or solid fuel boiler. Lowering the temperature to 18–19 ° C during sleep will not cause much discomfort, but it will save money.
- We take the power of an electric boiler maintaining the positive temperature in the building with a decreasing coefficient of 0.6–0.7 (minus 30–40%) of the amount of heat loss.
Tip. To organize a hot water supply, you do not need to look for a dual-circuit boiler. Usually 2 options are realized: a separate electric water heater or a powerful heat generator is installed plus an indirect heating boiler.
The performance of the heater for the night "charging" of the heat accumulator depends on the volume of the tank and is considered individually. The selection of an electric boiler under standard conditions is described in the video:
3 types of electric heating units
The next step is to select the type of boiler. There are 3 varieties of electric water heaters that differ in the principle of operation:
- heat generators with tubular heating elements (heating elements);
- electrode;
- induction.
It is pointless to divide electrical installations into types according to other characteristics. For example, the supply voltage - 220 or 380 volts - depends on the power of the unit, and not on the method of heating the water. Typically, heaters up to 6 kW are connected to a single-phase 220 V network, 7 kilowatts and more - to a three-phase network (380 volts).
The configuration and control automation is also different, this issue is proposed to be considered at the end of the publication. First, we will analyze the advantages and disadvantages of 3 types of electric boilers.
Pros and cons of TENovy coppers
TEN - this is the portion of the electrical circuit with high resistance. It is a copper tube (straight or curved), a heating spiral made of heat-resistant chromium-nickel alloy is embedded inside. A ceramic backfill acts as an insulator between the outer copper wall and the spiral.
Briefly list the constituent elements of any electric boiler (not only TENOVO):
- a heating block, in this case, a sealed container with heating elements inside;
- control automation - thermostat, temperature sensors, actuator;
- case with handles / control buttons.
Reference. The actuating element supplies or interrupts the power supply to the heaters at the command of the thermostat. There are 2 types - mechanical and electronic. In the first case, the circuit breaks the starter or contactor, emitting loud clicks. In the second case, the power supply is controlled by a triac unit, which operates silently.
The operation algorithm of the electric boiler differs little from other heating appliances. The coolant has warmed up to the set temperature - the heater has turned off, the water has started to cool - it has turned on. If there are 2 ... 4 heaters in the tank, then the control unit turns them on alternately, the so-called step heating is implemented.
We list the advantages of electric heating elements:
- the thermal performance of the unit does not depend on external factors, it changes only at the command of the control unit;
- the heating coil is reliably isolated from contact with the coolant, the heat generator works equally well with ordinary water or non-freezing liquid;
- failure of 1 heater from the group does not mean stopping the heating; power will simply decrease;
- replacing a blown heater is simple and inexpensive;
- Reliability of heating elements tested by many years of practice.
Electric boilers with tubular heaters are free from serious flaws. We note 3 minor minuses:
- Since the nichrome spiral is surrounded by ceramic backfill, heat transfer to the copper casing takes a little longer than other electric boilers.
- When using hard water, the copper tube is coated on the outside with a layer of deposits.Heat transfer is hindered, surface temperature rises, spiral life is reduced.
- If the heat selection stops, the heater coil burns out. That is, the heater does not tolerate "dry running", accidental switching on without water is guaranteed to lead to breakage.
At a price, an electric boiler with heating elements occupies a middle position between induction and electrode "brothers". Pricing is greatly influenced by bundling. For example, a Polish wall-mounted mini-boiler house Kospel EKCO.LN2-6 (6 kW) with a pump and an expansion tank costs about 600 oz. e., and a simple unit without bells and whistles Heatman Light 6/220 - only 100 at. e.
The advantages of electrode heaters
In general, the device of the electrode boiler repeats the design of the apparatus with heating elements. Only the power unit differs - a cylindrical chamber with an electrode (or several) inside. The heating section is separated from the control cabinet mounted side by side on the wall. The increased resistance in the circuit is created by the water itself, or rather, its layer between the internal electrode and the metal casing.
Explanation. The electric boiler works on the principle of a boiler made of 2 iron plates. The water flowing between them serves as a conductor, ions - charged particles of magnesium and calcium salts carry an electric charge. The generated heat heats the water. Hence the second name of the boiler is ionic.
Advantages of electrode boilers:
- the heating unit consists literally of 2 pieces of iron, there is nothing to break in it even in the absence of water or overheating;
- voltage drops to the power unit are fearless, only sensitive automation (if any) can suffer;
- high salt content - water hardness - only increases the heating rate, scale slightly reduces the power of the apparatus;
- heating units of certain models can be used in gravity heating systems;
- compactness.
For comparison, we present the cost of a 6-kilowatt heater of the famous Galan brand, with a set of automation the boiler will cost 155 y. e. According to the manufacturer, the energy consumption of a 6 kW heat generator will be approximately 950 kW per month. If there is a need to increase power, it is enough to buy a second power unit and install in cascade with the first.
Electric ion boilers have earned a lot of negative feedback from homeowners on the forums. The reason is the significant disadvantages of water heaters:
- During the heating process, a chemical reaction of electrolysis takes place, the salts of magnesium and calcium decompose, due to which the power of the boiler decreases markedly.
- Again, unit performance is variable. Depends on salt concentration, water temperature and mains voltage.
- With conventional antifreeze for heating, the electrode boiler is not "friendly", you will have to buy a special liquid. For obvious reasons, desalinated or distilled water cannot be used.
- During the electrolysis reaction, a mixture of various gases is released, sometimes combustible. Cases of airing of closed heating systems are noted.
- The power unit runs at full power in start / stop mode. To organize step regulation, you need expensive automation.
Personal review of the author of the article. I heat the house with a 100 m² electrode boiler, the timer turns on heating only at night. Heat carrier - tap water, without additives. Due to the decomposition of salts, it is necessary to change it once a month and a half, otherwise the power of the electric boiler drops by about 50%. I am afraid to add salt according to the instructions, since the system is mounted from steel pipes, gravity is provided.
Features of induction apparatus
This electric boiler is also divided into 2 parts - a heating unit and a control cabinet with standard automation. The heating section is a sealed cylindrical body, inside is a multi-turn induction coil-inductor and a hollow metal core. Simplified - the pipe inside which the coolant moves.How does an electric induction boiler work:
- After turning on the device, the contactor closes the power circuit at the command of the automation. A voltage of 220 or 380 volts is supplied to the coil.
- The inductor creates eddy currents of high density around the core, which causes the metal pipe to heat up. Heat is transferred to the water flowing inside.
- The heating element operates on / off at full power until the sensor detects the temperature set by the user. Then the automation turns off the heat and so on.
Note. The electric boiler inductor always turns on at maximum power, there is no step adjustment.
Vortex electric heaters are a relatively new type of heating boilers. The devices did not have time to earn a certain reputation, since private houses have been heated for no more than 10 years. It is too early to judge reliability, therefore, we indicate the obvious features of induction heat generators:
- if there is no water or circulation stops, the power unit fails;
- non-separable brewed casing assumes complete replacement of the heating section in case of breakage (for example, inter-turn circuit inside the coil);
- the unit is quite heavy, a heating unit of 5 kW weighs about 24 kg, 20 kW - 76 kg;
- there is no step heating - voltage surges appear in the house electrical network when the boiler is turned on.
Complete set of heating units
We have already listed the elements of any electric boiler in the basic, cheapest configuration. This is a heating unit, a temperature controller, automation with an actuator, controls and a temperature sensor.
An important nuance. In budget versions of boilers, the magnetic starter acts as the executive element. He clicks loudly at the moment the heating is turned on, the sound is clearly heard in the rooms adjacent to the boiler room.
In an expanded configuration, manufacturers supply electric boilers with the following equipment:
- low-noise modular contactor instead of a magnetic starter;
- circulation pump;
- membrane expansion tank for a closed heating system;
- overheating sensors and coolant pressure;
- safety group - automatic air vent, safety valve;
- circulation sensor - for induction heat generators;
- weather automation;
- LCD display, programmer, GSM remote control module from a smartphone.
Naturally, a "fat" grade electric boiler will cost much more than a "poor" one. On the other hand, the expansion tank, pump and safety group will still have to be bought. It is much more convenient to mount the unit when these elements are hidden inside the case.
Which electric boiler to choose - recommendations
In 90%, we recommend choosing an electric boiler with heating elements. These are reliable devices that are equally suitable for different heating systems - radiators, underfloor heating, floor or skirting convectors. Select the level of staffing based on the conditions of installation, operation and allocated budget.
Some more tips:
- In the apartment, definitely take a wall-mounted electric mini-boiler room equipped with heating elements, your own pump and tank.
- If the electric boiler is to be paired with a solid fuel or gas unit, it is better to choose a model without an integrated pump and expansion tank. The specified equipment is connected separately - the tank works for the entire system, the pump is controlled by a room thermostat, as shown in the diagram.
- Install a remote thermostat. Then the boiler will focus on the air temperature, and not the coolant.
- Take the electrode heat generator in 3 cases: a limited budget, too little space in the boiler room or connection to a gravity heating wiring without a pump.
- Least of all problems are electrode assemblies in open systems - the resulting gases safely leave through an atmospheric expansion tank.
- Induction boiler choose at will and availability of funds. But keep in mind: operating experience has shown that the specified device is no better than the heater. There were no special technical problems with induction heaters, only financial ones.
Comment. The electrode-type boiler for a gravity-fed system must have nozzles of the corresponding diameter (minimum Ø32 mm), the feed is directed upward.
For a water heated floor, only an electric TEN boiler is suitable. It is difficult for induction and electrode units without step heating to maintain a low water temperature in floor circuits - 35 ... 45 ° C.
Finally, about energy consumption
The homeowner's natural desire is to know how much electricity the electric boiler will use during the heating of a private house. Unfortunately, real consumption is impossible to predict. The indicator is too individual and depends on a number of factors - the degree of insulation maintained inside the temperature, weather.
Monthly consumption can be calculated approximately: take 50% of the calculated heat loss at home, multiply by 24 hours and 30 days. Example: losses are 6 kW, half - 3 kW, per day 3 x 24 = 72 kW, per month - 72 x 30 = 2160 kW. Why we take ½ power: during the season the weather is not always cold, the warmer it is on the street, the more often the electric boiler turns off.
An example from personal experience. The house of 100 m² is heated at night with an electrode boiler of 9 kW for 8 hours, the region is southern. For 6 months of the heating season, the electric boiler consumed 9104 kW. The average monthly energy consumption is 1517 kW, the average daily consumption is 1517/30 = 50.6 kW.