Increasingly in heating systems an alternative double-circuit boilers use boilers of indirect heating or the so-called "tank in the tank". When a large amount of water needs to be supplied, »Tank in tank« at several draw-off points become indispensable assistants. Stainless steel boiler suitable for country houses, office and industrial buildings.
"Tank in a tank" are becoming more and more popular in the heating market. Working with heat generated by any other energy sources is the main advantage, since water is not heated directly from electrical energy, solid fuel or gas. Boilers with indirect heating do not overload the power grid, do not need a chimney.
Working principle "Tank in a tank"
The indirectly heated stainless steel boiler is manufactured according to the tank-in-tank principle. It works on the basis of two tanks. The first container is internal, filled with heated sanitary water, the second container - the outer one contains a coolant - it is he who heats the sanitary water. Thus, "Tank in tank" eliminates a large number of disadvantages inherent in conventional water heaters with a coil.
The main advantages of the indirect heating boiler:
1. More draw points are provided hot water due to the increased heat transfer area. Also, a short heating time of the newly received cold water.
2. Water heaters made according to the tank-in-tank scheme have a smaller volume than was required when using a conventional water heater to ensure a given performance.
3.Sanitary requirements are met by the numerous advantages of stainless steel.
4.The use of reliable thermal insulation and self-cleaning effect of descaling results in saving energy consumption
5. Possibility of regulation of heating of sanitary water, due to the built-in thermostat.
6. Long service life
In rooms without a center of a lysed hot water supply system, tank-in-tank boilers are an indispensable assistant.
Boilers can be divided into indirect and direct heating boiler.
The advantages of indirect boilers (for example, boiler, WESTER or) use the heat converted heating boilers, and are intended for economical hot water supply of apartments, office and industrial facilities, cottages.
Gas water heaters use a direct heating circuit. The advantage of this type of boiler is stability and sometimes independence from electricity and other factors.
The advantages of indirect boilers (for example, the acv smart boiler) are the speed of heating and the possibility of using it for several points of water consumption. During a water shutdown, the indirect agent ensures its continuous supply. The volume of the tank can reach 1000 liters. Enormous energy savings!
You can buy indirect heating boilers in the section.
A life modern man who is accustomed to comfortable conditions, it is hard to imagine without hot water. Unfortunately, the work of the central water supply leaves much to be desired. Hot water is supplied intermittently, and some houses are not connected to central heating at all. In such cases, a good solution is to connect an indirect heating boiler.
What is an indirect heating boiler?
Separately, we note indirect heating boilers from the European brand STOUT. These boilers are universal, sold with capacities from 75 to 200 liters - suitable for an apartment or house of almost any size. Each stage of the STOUT boiler production process meets the European ISO standards, at all stages the product is checked for tightness.
The brand closely monitors the product, audits every 50th boiler. Absolutely everything is checked, from the quality of packaging to testing of operating modes. Thanks to this, the STOUT indirect heating boiler is reliable, easy to operate and will serve for many years.
For details, go to stout.ru.
How does an indirect heating boiler work?
The inside of the boiler is usually steel or plastic, and the water heating tank itself is made of heat-insulating material. Inside the tank there is a heat exchanger made of brass or steel, through which the coolant from the heating boiler passes. It is usually made in the form of a coil to ensure the fastest and most efficient heating of the tank. To protect against corrosion, a magnesium anode is used to protect the tank from pressure increase, a thermostat and a safety valve are installed inside the boiler. The outer body of the tank is usually made in the manufacturer's design style. Today, other models of indirectly heated boilers can be found on the market - tank-in-tank water heaters or boilers with several heat exchangers. But they are extremely rare to find on sale.
An indirect heating boiler is connected to the water supply system through an inlet for cold and an outlet for hot water.
Cold water fills the heating tank, and at the outlet hot water goes to the consumer. Each indirect heating boiler is connected to a pipeline through which the coolant enters the boiler for the next heating. On such a pipeline, a pumping and mixing system is required, which is responsible for the circulation of water.
Pros and cons of the scheme of work
The main advantages of the indirect heating boiler:
- the operation of such a water heater does not overload the electrical wiring during the heating season, since the boiler depends on central heating and does not consume electricity;
- when properly designed, the boiler has a very high performance and an optimal cost ratio;
- inner surface of the heater and coolant does not interact with running water , which ensures a safe and long service life of the unit;
- hot water is recirculated immediately after opening the faucet;
- the indirect heating boiler can always be switched to alternative source heat or use several.
Unfortunately, each scheme of work, in addition to positive, has negative aspects:
- to re-equip the system, you will need additional expenses;
- the cost of a boiler with indirect heating is much higher than gas or electric heaters;
- initial heating of water (volume more than 100 liters) lasts 1 to 2 hours, this can adversely affect the quality of the heating system of the room;
- for a boiler with a volume of 100 liters or more need a separate room due to the impressive size of the device.
What to look for when choosing an indirect heating boiler?
The most main characteristic boiler is its volume. You need to roughly estimate how much water is needed for a comfortable existence for your family. Based on averages, a person spends 5–15 liters per day on personal hygiene, 15–25 liters per day on washing dishes, 50–100 liters per day on showering, and 150–200 liters per day on bathing.
It is believed that for one resident it is necessary 80-100 liters of hot water Of course, this calculation is conditional, it all depends on the preferences and habits of the residents. For example, someone likes to take a shower twice a day, another manages to take a bath once a week. The larger the volume of the boiler, the higher its cost.
The next thing you need to pay attention to when buying is interior material water heater.
Preference should be given to boilers with a brass coil. It will heat water more efficiently than steel, and besides, it is much easier to clean the brass coil.
The water heating tank must be protected against corrosion. In cheaper models, the tanks are covered with a layer of enamel or glass-ceramic. Expensive instruments are protected from corrosion by stainless steel.
In addition, do not forget about the thermal insulation of the unit, high-quality boilers are insulated with mineral wool or polyurethane foam. Models with foam insulation are best avoided.
The boiler can be connected to the hydraulic and electrical system. The connection scheme on two pumps or hydraulic is considered the most effective.
One pump is used for residential heating, the second is for indirect heating the boiler itself. Wiring diagram connection involves a mode switching system - a relay.
In a two-pump boiler connection scheme, the coolant flows move in different directions due to the operation of the circulation pumps. The hot water line (boiler and heating boiler) is connected in parallel to the pumps, the operating mode of the pumps is controlled by the heater's temperature sensor. A non-return valve is installed in the circuit after each pump so that the pumps work autonomously, independently of each other. In the presented scheme, the heating circuit is turned off, but this practically does not affect the rate of water heating in the batteries.
Typical connection errors
The first mistake that is most often encountered is the wrong place to install an indirect heating boiler. Need to install it as close as possible to the boiler or to the outlet of the central water supply.
The next error is an incorrect connection of the cold water supply. Serial connection of the inlet and outlet of the coolant ensures efficient operation of the water heater. For optimum heating and heating results the coolant must enter the boiler from above and exit from below.
Wrong connection circulation pump entails many negative consequences:
- motor axis should be placed horizontally this will help to avoid early bearing wear;
- the pump must be protected from debris, you need to constantly monitor the condition of the mesh filters.
The modern market of heating systems offers a wide selection of boilers and other water heaters, so everyone can find a model with the best price-quality ratio. For advice, you can always contact the service center, where you will definitely be assisted in the design, installation and maintenance of heating appliances.
Article plan
If you live in a private house, then installing an indirect heating boiler together with a boiler will kill two birds with one stone - heat the house and provide constant access to hot water. We have selected for you best models water heaters that can be found on sale today - choose!
Briefly about the main characteristics
In conventional storage water heaters, the liquid temperature rises due to the operation of heating elements, while in boilers, heating is carried out due to the circulation of a heated coolant in the system. It looks something like this: water is heated in a single- or double-circuit boiler and fed through pipes to a coil or other heat exchanger installed in the tank; at the same time, cold water enters the tank from the main, which is subsequently heated due to heat exchange through the walls of the coil. Instead of a coil, a tank-in-tank design can be provided. In this case, the coolant is supplied to the external tank, and the heated liquid is supplied to the internal one. The presence of temperature and liquid volume sensors inside the tank, as well as automatic relays, ensure the smooth operation of the equipment. Some models are also equipped with additional electric heaters - even with force majeure with a boiler, you can use hot water. Everything seems to be simple, but before buying it is necessary to understand the main technical characteristics of such equipment.
| Selection criterion | Varieties | Note |
|---|---|---|
| Volume of the tank | from 50 to 400 liters and more | In the most popular models for domestic use, tanks with a volume of 80 to 200 liters are used. The volume is selected based on the consumption of hot water and the number of draw points. |
| Power | from 2 to 60 kW and above | Together with the volume of the tank, the power determines the rate of heating of the liquid. The more powerful the equipment and the smaller the capacity, the faster the heating goes. |
| Max water pressure | 6-10 bar (0.6-1 MPa) | The pressure that the boiler can withstand in operating mode. It is advisable to install pressure reducers to prevent damage from water hammer. |
| Mounting method | Wall | Equipment with a small tank volume (up to 100 liters) is often attached to the wall. The larger the volume, the more difficult it is to do this, so capacious water heaters are made in the floor version. |
| Floor | ||
| Combined | ||
| Heat exchanger design | Coil | The heat carrier from the boiler is supplied through a metal coil installed in a tank with heated water. The most common type. |
| coil in coil | The heat exchange area is increased due to the use of two coils with different spiral diameters. | |
| Tank in a tank | There are two steel tanks - one inside the other. The coolant from the boiler is supplied to the larger tank, heated water is supplied to the smaller one. | |
| Heat exchanger material | Stainless steel, brass | The vast majority are made of stainless steel. However, this material may vary in quality. Therefore, you should not save and buy products of an unknown brand. |
| Material and thickness of the thermal insulation layer | Foam rubber, mineral wool, expanded polystyrene, polyurethane foam - from 20 to 60 mm thick | The effectiveness of thermal insulation is determined by the value of thermal conductivity (the less, the better) and the thickness of the insulation layer (the more, the better). To date, a good solution is the use of 50-60 mm polyurethane foam insulation. |
| Maximum productivity in flow mode when heated to ΔT °C, l/min | where ΔT °C = 25, 45, 55 etc. | Determines the efficiency of the heater in flow mode. Depends on its power. |
| Heating time per ΔT °C, min. | where ΔT °C = 25, 45, 55, 60 etc. | Determines the heating rate of the entire volume of water in the tank. Depends on size and power. |
| Options | heating element | Many models can be upgraded with tubular electric heaters that fire when the boiler is turned off. |
| recycling | The tank may be provided with a circuit for water circulation using a pump. This is necessary so that water is supplied to the consumer at a constant temperature. | |
| Solar collectors | The use of solar energy to heat the coolant with the subsequent transfer of heat to water heating. Collectors are installed on the roof. In the CIS, this option is relevant only in the warm season. | |
| Heat pump | Ability to connect a heat pump to minimize the cost of heating cold water. A very rare option. |
We omitted such a parameter as the thread diameter for connecting to pipes, because. this issue, if necessary, is solved by installing adapters.
Calculation of the volume of water
Only you can determine exactly the required volume, because. calculations are tied to the conditions of water consumption. Our task is to provide information that will somehow help in the choice or suggest thoughts when making the calculation. For example, we open SNiP 2.04.01-85 and see that the norms set 7.9-10.9 liters of hot water (HW) per hour per person. Following some simple calculations, we get the following table.
These calculations can only be taken into account if the water heated by the boiler is consistently used and one draw-off point is operating at the same time (only one tap is open). In practice, the given values \u200b\u200bmust be multiplied by 3-5. Why is this happening? Because the norms do not take into account the desire to bask in the shower (+20 l. HW) and take a bath (+80 l. HW), wash a mountain of dishes (+20 l. HW), etc. etc. Take into account the peak loads on the boiler - choose the volume that is most suitable for your needs.
- 50-60 liters is enough for 1 person;
- for 2-3 people you need to choose from models of 80-120 liters;
- for a family of 3-5 people, the capacity of a boiler of 120-200 liters is enough
To make it easier for you to choose the right model of equipment, we have identified four product groups depending on the volume of the storage tank: up to 100, 200, 300 and 400 liters. All technical specifications are taken from open sources, and prices are provided for comparison purposes only.
Important! Please note that some water heaters are only suitable for certain models of boilers. In the description, we will focus on this, but we recommend that you clarify all the nuances before buying.
Up to 100 liters
1. Baxi Combi 80 (80 liters) - from 52,500 rubles.
A notorious Italian player specializing in heating and water heating equipment, Baxi has been holding the quality mark for decades. The Baxi Combi 80 small volume boiler model is designed to work in conjunction with the LUNA-3 Comfort series boilers of the same manufacturer. Placement is floor, the water heater can be installed directly under the boiler, saving space. One of the advantages of this system is its compact dimensions. Corrosion protection is provided by the use of stainless steel and a magnesium anode. Polyurethane foam is used as thermal insulation. TENA connection is not provided.
2. Gorenje GBK80ORRNB6 (72.6 liters) - from 24,000 rubles.
When looking for a small model that can provide hot water for one or two people, pay attention to Slovenian equipment. This is a classic compact boiler with two tubular heat exchangers, the performance of which is enough for two points of water intake at once. The device is equipped with an electronic control unit and allows you to change the DHW temperature in the range of 15-75 °C. It has outlets for connecting to the boiler on the right side, two dry heating elements are installed as an additional heater. The model is equipped with several types of protection: against corrosion (magnesium anode), against freezing ( effective thermal insulation), from overheating and heating without water. The manufacturer also provides a legionellosis control function ( lung disease, the pathogens of which actively multiply in hot water). One of the best combined solutions in terms of price / quality ratio.
* operating parameters in flow mode are not specified by the manufacturer. The power of the heat exchanger itself is not indicated - only for the heating element.
3. Protherm FS B100S (95 liters) - from 36200 rubles.
The Czech boiler is structurally tied to the boilers of the same manufacturer - the Bear. Compact, with a concise but informative control panel, it easily fits into the kitchen interior as built-in appliances. Enamelled stainless steel, magnesium anode and antibacterial coating - all aimed at protection against corrosion and microorganisms. The tubular heat exchanger provides a high rate of heating of the entire volume of liquid: water is heated by 50 degrees in 13 minutes. To keep warm, the product is protected by a polyurethane foam coat.
4. ACV COMFORT 100 (100 liters) - from 48,000 rubles.
The Belgian manufacturer with almost a century of history offers interesting solution based on a tank-in-tank heat exchanger - model . The boiler consists of two stainless steel containers of different volumes, one of which is inserted into the other. Particular attention should be paid to the internal container: its surface is corrugated, therefore, due to thermal expansion, a change in size takes place, followed by the removal of the formed plaque of hardness salts (scale). The equipment is installed on the floor by default, but with the help of additional fixings it is possible to mount it on the wall. The heat-insulating layer is made of polyurethane foam 30 mm thick. The set of standard functions is small, but an optional control panel can be installed. It is also worth considering the lack of the possibility of recycling and connecting the heating element.
Up to 200 liters
5. Baxi Premier plus 150 (150 liters) - from 50,600 rubles.
It is possible to ensure the full operation of two hot water points with the help of. In a series of these heaters, a tubular coil-in-coil heat exchanger is used. Due to its low weight, the device can be hung on a wall or placed on the floor. The parts of the structure that come into contact with water are made of DUPLEX stainless steel, the minimization of heat losses is achieved by the use of polyurethane foam. The model is equipped with a thermostat and can be used in conjunction with any type of boilers. Optionally, it is possible to connect a tubular electric heater. The manufacturer has provided for the connection of the recirculation circuit. According to reviews, this is one of best solutions value for money for a family of four.
6. BOSCH WSTB 160 (160 liters) - from 28,000 rubles.
If a gas boiler is installed in your house, then you should think about buying a water heater. Although there is no possibility of connecting a heating element here, there is a recirculation system. The model is adapted to the harsh conditions of use in the CIS, i.e. suitable for hard water. To protect steel from corrosion, the material is coated with a special composition of glass-ceramic. There is a recirculation line so you can always count on getting water at a constant temperature. To minimize heat losses, a fur coat of 50 mm polyurethane foam is provided, the lining is made of PVC, soft. Frontal connection, it is possible to connect a temperature sensor. The entire volume is heated to ΔT=45°C in 37 minutes.
7. Protherm FE 200 BM (184 liters) - from 41650 rubles.
Many manufacturers offer storage heaters that are only suitable for their boiler models. If you installed a Proterm boiler, then to meet the needs of a large family in hot water supply, you should think about installing it. This is an indirect floor standing boiler made of stainless steel, enameled for corrosion protection. The installed titanium anode serves the same purpose. To prevent bacteria from multiplying on the walls of the container, they are covered with a layer of antibacterial substance. Productivity is high - with a delta of 25 degrees, you can get more than 30 liters of water per minute. Without the possibility of connecting the recirculation line and heating element.
8. Gorenje GV 200 (188.9 liters) - from 25,800 rubles.
Floor water heater of indirect type Combustion GV 200 - simplicity of the device, reliability of a design and laconic design. The product is an enameled steel tank with a tubular heat exchanger inside. Installed on the floor under the boiler. An overpressure relief valve is used as protection against overheating. The device is protected from corrosion by enamel and magnesium anode. It takes up to 24 minutes to heat the entire volume of water in the tank from 15 to 75 degrees. A 40 mm thick thermal insulation layer is responsible for maintaining the temperature of the hot water supply.
* the possibility of working in flow mode is not announced by the manufacturer
Up to 300 liters
9. ACV COMFORT 240 (240 l.) - from 65,000 rubles.
Another representative of indirect water heaters that use a tank-in-tank heat exchanger. The model is able to provide hot water to three points of water intake. The product is protected from corrosion due to the use of stainless steel and a special approach to the formation of the walls of the inner tank. Here it is corrugated, which has a positive effect on its work even with very hard water. At the same time, the equipment is characterized by the same features as for products of the same series: a minimum of functions, a thermal insulation layer of 30 mm, the inability to connect a tubular electric heater and a recirculation circuit.
10. Protherm FS B300S (295 liters) - from 63,000 rubles.
This accumulator is intended for use with Proterm Grizzly or Bizon boilers. - a capacious tank with a tubular heat exchanger. There are two flanges in the tank: for installing a heating element and servicing the boiler. Enamelled surfaces that come into contact with water, as well as the presence of a titanium anode, protect equipment from corrosion. Not to mention the presence of an antibacterial coating. A layer of polyurethane insulation is responsible for reducing heat loss. The device is characterized by high performance in flow mode, it is possible to connect a recirculation line. The possibilities of this heater will be appreciated by the owners of large private houses with more than three bathrooms.
11. Baxi Premier plus 300 (300 liters) - from 70,000 rubles.
Often the main criterion for choosing a boiler is not only its volume, but also the heating rate. In this case, it is relevant to consider models with a coil-in-coil heat exchanger. - exactly what is needed! Firstly, it is compatible with any boilers. Secondly, high-quality stainless steel, perfectly protected from corrosion, is used for its production. Thirdly, with enough compact size and low weight, the equipment has a universal placement and is equipped with an accurate thermostat. The model allows you to supplement the system with a recirculation circuit. Connecting a heating element for 2.7 kW is optional.
Up to 400 liters
12. Drazice OKC 400 NTRR / 1 MPa (380 liters) - from 68,000 rubles.
The Czech boiler is equipped with two tubular heat exchangers, one of which is designed to be connected to a solar collector, and the second to the boiler. This allows you to save a lot on heating water on sunny days, especially in summer. If necessary, for example, a malfunction of the boiler equipment, you can install two auxiliary electrical heating element. The enameled tank, as well as the presence of a magnesium anode, provide long-term protection of the tank from corrosion. 50 mm rigid polyurethane foam is used as a heat-insulating layer. There is a recirculation pipe.
Information on the rate of water heating in flow mode is not provided by the manufacturer. This is due to the presence of two independent heat exchangers with different temperature regime work.
13. Bosch SK 400-3 ZB (388 l.) - from 59,500 rubles.
There are not many indirect water heaters of the capacity we are interested in in the Bosch assortment, but among them there is a special model - Bosch SK 400-3 ZB. This is an enameled tank with a stainless steel coil. Corrosion protection is represented by a magnesium anode, which has already become a natural phenomenon in such equipment. The device is quite simple: a built-in thermometer and a flange for easy maintenance. At the same time, it is possible to connect a hot water recirculation line, as well as to synchronize with the boiler if the latter has an NTC sensor connector (thermal sensor). Those. you can fine-tune the operation of water heating equipment. Separately, it must be said about thermal insulation. Here it is not polyurethane foam, but made of rigid foam, which, with equal thickness, gives a lower heat-shielding effect.
14. BAXI UBVT 400 SC (395 l.) - from 58100 rubles.
If the prevailing part of the boilers is designed to work in tandem with the boiler, then the model is an exception to the rule. It is adapted for connection to a solar collector, so its purchase will be appropriate in two cases: in places with year-round sunny weather or for seasonal use. Additionally, for heating, it is possible to install electric heaters. The container itself is made of steel coated with titanium enamel - it turned out to be a corrosion-resistant and durable coating. The latter is also facilitated by the presence of a magnesium anode. The kit includes a thermometer for temperature control, there are sockets for connecting sensors. The design provides a flange for monitoring the condition of the coil, as well as a built-in pipe for recirculation.
15. Hajdu STA 400 C (400 liters) - from 64,100 rubles.
The model from the notorious Hungarian manufacturer is interesting in that with one heat exchanger, fine-tuning of the equipment is possible. So, in the cold season, such an indirect heating boiler can be configured to work in tandem with the boiler, while in the summer it can be connected to a solar collector. In the latter case, if necessary, the heating element is additionally connected. The tank and heat exchanger are protected from corrosion by a layer of hot enamel and a magnesium anode. To minimize heat loss, the container is covered on the outside with a layer of polyurethane foam protected by a plastic casing. A branch pipe is provided for connecting a DHW recirculation system.
In the next video, this boiler is presented in section.
Editor's Choice
For ease of comparison, we will enter the main characteristics in the table and decide on the most successful models. To make it clearer, we choose a boiler for 1-2 people, 2-4 people, 4-6 people. (marked in the table below in bold from top to bottom, respectively). Because not all manufacturers adhere to common standards when drawing up technical documentation, for example, not everyone indicates the value of performance in the flow mode, then we introduce the characteristic N. It shows the ratio of a unit of power per 1 liter. water. Those. we simply took and divided the capacities indicated by the manufacturer by the useful volume of drives. The larger this value, the faster the heating takes place.
| Model name | Useful volume, l | power, kWt | N, kW/l | Accommodation | heat exchanger | heating element | rec-tion | price, rub. |
|---|---|---|---|---|---|---|---|---|
| 80 | 31 | 0,3875 | outdoor | coil | — | — | 52500 | |
| 72,6 | 2 | 0,027548 | wall | coil | + | — | 24000 | |
| 95 | 26,1 | 0,274737 | outdoor | coil | — | — | 36200 | |
| 100 | 23 | 0,23 | floor/wall | tank in a tank | — | — | 48000 | |
| 150 | 30 | 0,2 | floor/wall | serpentine in serpentine | + | + | 50600 | |
| 160 | 20,8 | 0,13 | wall | coil | — | + | 28000 | |
| 184 | 43,2 | 0,234783 | outdoor | coil | — | — | 41650 | |
| 188,9 | 17,6 | 0,093171 | outdoor | coil | — | — | 25800 | |
| 240 | 53 | 0,220833 | floor/wall | tank in a tank | — | — | 65000 | |
| Gorenje KGV 300-2/BG | 280 | 69,6 | 0,248571 | outdoor | coil | + | + | 83700 |
| 295 | 46 | 0,155932 | outdoor | coil | + | + | 63000 | |
| 300 | 30 | 0,1 | floor/wall | serpentine in serpentine | + | + | 70000 | |
| 380 | 57 | 0,15 | outdoor | coil | + | + | 68000 | |
| 388 | 60 | 0,154639 | outdoor | coil | — | + | 59500 |
To organize the supply of hot water, powered by a heating system, a double-circuit boiler is installed. Its disadvantage is low productivity. Hot water is only enough for washing hands or dishes. For comfortable bathing, it is better to install an indirect heating boiler, the advantage of which is a storage tank.
The basic principle of operation of an indirect heating boiler is to circulate the coolant through a heat exchanger connected to the heating system. The hot liquid is pumped by the pump. The internal circuit of the boiler is enclosed in a storage tank, where cold water coming from the water supply system is heated from the energy of the coolant.
The circulation of the heating system has a vicious circle. Having given up energy, the coolant returns to the boiler through the pipes. The cycle is repeated while the pump and boiler are running. The rate of water heating inside the storage tank depends on the thickness of the coil pipe.
Design features
To better understand the work, it is necessary to study the device of the indirect heating device and understand how it differs from its counterparts.
The water heater is intended for systems of heating of the closed and open type. The main difference is the energy source. If gas water heater works from bottled or main gas, and electrical appliance from the heating element, then the internal circuit of the indirect heating boiler consists of a coil. The coolant is the source of energy. The coil is equipped with an inlet and outlet for connection to the heating system.
There are bivalent water heaters with two heat exchangers, where a heat carrier is supplied to one coil from the heating system, and heat is supplied to the other circuit from a solar system or a heat pump. If desired, the coils can be combined with fittings. It will turn out an indirect heating water heater with one circuit.
The heat exchanger is enclosed inside the storage tank, where the indirect heating of the water takes place. To connect to the water supply, the tank is similarly equipped with an inlet and outlet pipe. The shape of the storage tank is usually a cylinder, but there are rectangular models. So that the water inside the tank does not quickly cool down, it was enclosed in a decorative case, and the space between them was filled with thermal insulation.
A magnesium or titanium anode protects against scale formation. The heating element is installed inside the storage tank. The anode protects the metal parts of the boiler from galvanic corrosion and also reduces water hardness.
A thermostat is a regulator with which to reduce or increase the flow of coolant into the heat exchanger. The mechanism allows you to adjust the temperature of water heating.
When choosing a boiler for home use, it is better to give preference to a model where a heating element is additionally provided. The device combines indirect and electric water heater. The heater allows you to heat water in the summer when the heating system is not working. To regulate the heating of water from electricity, an additional thermostat and automation are installed.
Varieties
Most often, an indirect heating boiler with a coil is found on sale. However, there are models assembled according to the "tank in the tank" system. The principle of operation remained unchanged, only instead of a coil, an additional capacity acts as a heat exchanger. The advantage of the tank-in-tank system is the larger heating area. To connect the heating system pipe to the tank, an inlet and outlet pipe is similarly provided.
By type of installation, indirect water heaters are:
- Wall models are limited to a storage tank of up to 200 liters. The water heater is hung on steel brackets. The main requirement is a solid wall. Hollow drywall partition won't hold a water tank.
- The floor water heater is designed for a large capacity. Household models are usually produced with a storage capacity of 250-300 liters. The floor boiler for industrial use can hold more than 1000 liters of water. Due to the large dimensions, a separate room is allocated for the water heater.
According to the type of tank location, an indirect boiler is:
- Horizontal models are roomy. It is more convenient to maintain the water level, but the water heater takes up a lot of space.
- Vertical models are smaller. The advantage of a water heater is its compactness and saving usable room space.
According to the material of manufacture of the storage tank, boilers are of three types:
- All cheap models are equipped with an enameled steel tank. In a couple of years protective layer breaks down and leaks.
- Glass-ceramic tanks are one step higher in quality. The service life is increased, but they are also more expensive.
- Stainless steel tank is expensive. However, the service life is unlimited. The water heater will last for many years, if you do not come across a low-quality fake.
A variety of indirect water heaters allows the consumer to choose the optimal model in terms of shape, cost, and capacity.
Positive and negative characteristics
Considering the pros and cons of indirect water heaters, we must dwell on the main advantage - energy savings. You will have to pay separately for the gas and electric boiler. The indirect water heater receives energy free of charge from a working heating system.
Other benefits stand out:
- Long service life. The heating of the heat exchanger does not form solid accumulations. Scale appears during the operation of the heating element, but it is not turned on all year round, but only in summer.
- A water heater with two heat exchangers or a tank-in-tank system is characterized by high performance.
- The model with an additionally installed heating element combines two important parameters: efficiency in winter, efficiency in summer.
- Having welding experience, an indirect water heater can be made independently.
The downside is the complexity and high cost of installation. The first heating of the container takes a long time, but then the water temperature is constantly maintained. In the absence of heating elements in the summer it is impossible to get hot water.
How to choose an indirect heating boiler
Making the right choice of a suitable indirect heating boiler model is a difficult task for a beginner. However, there is nothing overwhelming here, you just need to take into account a few important nuances:
- When choosing a water heater with indirect heating for an apartment or a private house, the first step is to determine the optimal volume of the storage tank. In order for all family members to have enough hot water, they calculate taking into account the approximate consumption of 100 liters per day by one person.
- An indirect water heating boiler is economically beneficial for a family of four or more people. With this number of people, the approximate consumption of hot water is 1.5 l / min.
- Paying attention to the volume of the tank, take into account the heating time. Large capacity will take longer to heat up. It may be worth giving preference to a model with two heat exchangers or a tank-in-tank system.
- The composition of the thermal insulation determines how long the water will remain hot after the boiler is turned off. Cheap water heaters come with foam. Porous material poorly retains heat and quickly decomposes. The optimal thermal insulation is mineral wool or polyethylene foam.
- To make the right choice, you need to compare the power of the indirect water heater and the heating boiler. If the latter is characterized by weak parameters, the boiler will become an unbearable load.
- When buying any model, be sure to pay attention to the presence of a thermostat, valve and other protection elements.
When with everyone important nuances the issue is resolved, you can pay attention to the form, design, manufacturer and other details.
Calculation of the volume of the storage tank
To make an approximate calculation of the volume of the storage tank, you can use simple withdrawal water meter readings. When the same number of people constantly arrive at the house, the daily consumption will have the same data.
A more accurate calculation of the volume is based on counting water points, taking into account their purpose and the number of living family members. In order not to go into complex formulas, the hot water consumption is taken from the table.
Connection diagrams for the heating system
When choosing a connection scheme for an indirect boiler for heating water, the location of the device in the house, as well as the features of the wiring of the heating system, are taken into account.
A simple and commonly used scheme is based on connecting an indirect device through a three-way valve. As a result, two heating circuits are formed: heating and hot water. After the boiler, a circulation pump crashes in front of the valve.
If the need for hot water is small, a system diagram with two pumps is suitable. The indirect water heater and the boiler form two parallel heating circuits. Each line has its own pump. The scheme is suitable for country houses where hot water is rarely used.
The connection diagram is more complicated if the house has a “warm floor” system installed along with radiators. To distribute pressure along all lines, and together with an indirect boiler there will be three of them, a hydraulic distributor is installed. The unit normalizes the circulation of water through the "warm floor", water heater and radiators. Without a distributor, pumping equipment will fail.
In indirect water heaters with recirculation, three nozzles come out of the body. Traditionally, two outputs are used to connect to the heating system. A looped circuit is led from the third branch pipe.
If the indirect water heating device does not have a third branch pipe, and recirculation must be done, then the return line circuit is connected to the cold water pipe and the recirculation pump is additionally inserted.
Recirculation allows you to get hot water at the outlet of the tap even before the liquid in the storage tank of the boiler is completely heated.
Popular Models
It is always necessary to choose the right model for technical specifications. As an aid, you can see the rating of indirect heating boilers, compiled taking into account consumer feedback.
Viessmann Vitocell-V 100 CVA-200
The model is equipped with a steel tank with an enamel coating with a capacity of 200 liters. Rapid heating of water is carried out by means of a heat exchanger with a total area of 1 m 2 . The temperature is controlled by a thermostat. Maximum valid parameters: water heating - up to +95 ° C, inlet pressure - 10 atm.
Drazice OKC 200 NTR
The water heater is presented in two models: with one and two heat exchangers. The container is similarly designed for 200 liters of water. However, heating is carried out faster due to the increased heat exchanger area - 1.45 m 2. The disadvantage is the lack of a heating element, which does not make it possible to obtain hot water in the summer.
Roda Kessel ILW 200B
The powerful appliance with a 200 l steel storage tank is equipped with copper heat exchanger. Additionally, the model is equipped with a heating element, which allows you to get hot water in the summer when the heating is turned off. The temperature is controlled by a thermostat. The maximum limit is +65 o C.
Indirectly, the use of the capabilities of the heating system is becoming more and more popular today among the inhabitants of country houses and cottages in the private sector. Indirect DHW heating is the most energy efficient, economical and smart way to heat water from all available methods.
An indirect heating boiler, as opposed to a direct one that heats water using gas or electricity, provides housing with hot water at a minimum cost calculation. A heater of this type is a reservoir in the form of a rectangle, cube or barrel made of a metal sheet with heat-saving insulating material and resembles a huge thermos.
An indirect heating boiler is usually installed next to the boiler in the boiler room, there are branded kits where the installation is thought out directly to the boiler equipment.
What is an indirect heating boiler
What is it for?, first of all, a typical layman asks. Owners of country houses rightly believe that it is much easier to buy a double-circuit boiler. One circuit will be used for heating the household through the heating system. The second circuit will prepare hot water for hot water supply, thus two issues are immediately closed with one purchase.
Yes, such reasoning is valid, but up to a certain point. Firstly, the double-circuit boiler instantly switches to hot water preparation mode as soon as you open the tap. The boiler completely stops taking care of your heating system at this time, leaving it to its own devices. Simply, the boiler directs all its power to DHW heating, blocking the heating of the heating heat exchanger.
Secondly, as a rule, a double-circuit boiler does not have the full functionality of a gas column, its power is hardly enough for one draw-off point. It turns out that if the family returned from a ski trip, and the household decided to take a shower, then the heating system will be turned off for at least a couple of hours.
In addition, the rest of the family will have to patiently wait for all the participants and not turn on the tap in the kitchen if they do not want to hear flattering words addressed to them. Thus, only at first glance, an indirect heating boiler looks like a waste of money. In fact, this is a necessity to ensure a comfortable stay. An acceptable compromise would be the verdict to buy an indirect heating boiler with a capacity of 200 liters.
Schematic diagram of an indirect heating boiler
Installed inside heat exchanger - the heart of the design, is most often made ofbrass or carbon steel, the coolant circulates through it from the heating boiler. The heat exchanger has the form of a spiral, which allows you to quickly and efficiently heat the liquid in the tank.
Through the hot water outlet and the cold water inlet, the device is connected to the main water supply system. It turns out that the indirect heating boiler is more than simple, and it is not even clear why the simplest invention has not been used by mankind for so long.
After spending only three and a half minutes watching a video review, you will understand the principle of operation of an indirect heating boiler, especially since the video series is easier to understand:
Indirect heating has the following advantages in use:
- The main advantage is that an indirect heating boiler does not require financial costs for operation. It does not at all burden the electrical wiring with an additional load during the peak heating period, because the described system does not consume electricity;
- Due to the closed circuit, water constantly circulates through the boiler and is in a hot state, after opening the tap, the consumer immediately receives a hot stream without draining the cold sediment;
- The recirculation process not only keeps the water hot, but also protects the DHW system from contamination by pathogenic microorganisms - Legionella. Supported heat hinders their development.
- Running water is excluded from interaction with the inner surface of the heat exchanger tubes, scale and salt are not deposited in it, which ensures the possibility of long-term operation of the boiler system;
- Large hot water reserves and increased power modern designs allow the liquid to heat up much faster than traditional storage tanks. The volume of stocks calmly makes it possible to connect an indirect heating boiler to two or more points that consume hot water.
- The coolant coil and the auxiliary heating element are protected from corrosion by a special anode. In fact, the anode takes on the entire load of corrosion, extending the service life of the heating elements.
This device also has some disadvantages, which are:
- depending on the connected heat sources;
- in the summer, in the absence of heating, it is necessary to connect to electricity, for this it is equipped with electric heaters.
Essentially, an indirect water heating system uses the thermal energy generated by a solid fuel or gas boiler. The combination of a heat generating device and an indirect heating boiler forces the boiler to do double work. The advantage is especially felt in winter time- it turns out that the water is heated for free, due to the fact that the heating system works one way or another.
During the winter, water heating costs can account for up to one-third of all electricity bills. Connecting an indirect boiler system to a gas or pellet boiler effectively contributes to save our finances.
Advantages and disadvantages of an indirect heating boiler
The positive factors of using such a boiler include:
- Indirect water heating does not create an additional load on the electrical wiring, especially during the heating season, since it is connected to centralized heating and has practically nothing to do with electricity;
- with proper connection and configuration, the boiler is able to show a high coefficient of performance with an acceptable cost comparison;
- the heater located inside, as well as the coolant, does not come into contact with the inlet water, thereby ensuring the duration of operation and the safety of the unit;
- it is always possible to connect an indirect heating boiler to other heat sources, as well as to use several devices at the same time, creating a cascade.
The tank and the emergency heating element are protected from corrosion by an anode made of magnesium alloy. In order to avoid the maximum allowable pressure, a thermostat and a safety valve are installed in the boiler. The tank body can be in any design, for a variety of interiors.
Along with the undeniable advantages of this system, there are also disadvantages:
- if necessary, refurbishment existing system you need to be prepared for the costs;
- the price of an indirect heating boiler is very high, the initial costs for the acquisition and installation will require significant financial resources. So, the price will always be higher than the cost or;
- after installation and the first start-up, heating the first 100 or more liters of water will last up to two hours, which may adversely affect the heating of the house during this period;
- buying a boiler is half the battle, a capacity of 100 - 200 liters has large dimensions that will have to be taken into account, your boiler room should provide free space.
How to choose an indirect heating boiler
The main difference between a boiler and a tank is the capacity of the tank. For right choice and avoiding excessive costs, when buying a boiler, you need to know how much water will be required to meet the demand of the family unit. The average indicators are presented by such calculations: personal hygiene, per day - up to 15 liters; washing kitchen utensils - up to 25 liters per day; shower - up to 100 liters per day; bathroom - up to 200 liters.
It is generally accepted that one person consumes about a hundred liters of hot water, but this, of course, is a convention, the actual consumption depends on the person himself and his habits. Someone visits the shower twice a day, the other spends one day a week taking a bath. Surely we can say that a larger volume of the heater will have a greater cost.
The second important factor affecting the cost of the boiler is the materials from which it is made, in particular its internal parts. It is recommended to choose a unit with a brass coil, which gives more efficient heating compared to steel. Brass is also convenient because it is much easier to clean scale from it than from steel.
The level of protection against corrosion should also be taken into account. In low-cost models, the surface of the tanks is covered with an enamel layer or glass-ceramic. In higher quality appliances, stainless steel is used in the manufacture of the tank instead of the inner coating.
A good boiler should be provided with a heat-insulating layer. As this material, either basalt wool or gas-filled plastics - polyurethane foam are used. If the thermal insulation of the boiler is represented by foam rubber, it is better to ignore this model.
Proper connection of an indirect heating boiler
The first step is to choose the right location for the device. It is necessary to take into account, at the place of installation of the boiler, quick and easy access to important connecting links of the system - this will allow carrying out routine repair work equipment and carry out maintenance.
Models of hinged execution of an indirect heating boiler will require a strong brick load-bearing wall at the attachment point. Drywall or lightweight walls interior partitions cannot provide the required rigidity and cannot be fully used in installation work
The distance from the tank mounts to the ceiling should be 15-20 cm. Anchor-type spacer bolts act as fasteners, and their length and diameter are selected based on the material of the wall and the volume of the boiler.
The approximate load for pulling out a container up to 100 liters is from 25 to 25 kilograms, when mounted on concrete wall a bolt will suffice 10 mm thick in diameter and 100 mm long. For the same parameters, but taking into account the brick-cinder block wall, a bolt is needed with a diameter of 12 mm and a length of 120 mm.
After mounting the heater to the wall, it should be connected, for this:
- two separate cranes are installed on it for overlapping;
- a fum tape is wound and a relief valve is connected to the cold water inlet line;
- connection to the water supply system with a flexible hose;
- after all the connecting operations, you can supply cold water to the water heater and at the same time turn off the hot water tap - this will allow you to bleed any air.
Connecting an indirect heating boiler
It can be carried out using both a hydraulic system and an electric one. The most effective is the scheme in which the connection takes place on 2 pumps, i.e., the hydraulic scheme, where one of the pumps acts as a heater for the room, and the second is used for indirect heating of the boiler itself. The electrical connection is made via a relay switching system.
When an indirect heating boiler is connected through two pumps, the heat-carrying flows move in different directions due to the operation of the recirculation (reverse) pumps.
The hot water supply line coming from the coolant and the water heater is simultaneously connected to the circulation pumps, and the regulation of the operating mode of the pumps is provided by the heater temperature sensor.
Behind the pumps in sequence, direct-acting fittings in the form check valve, for autonomy and independent operation of pumps from each other.
Connection to pipes made of various materials
The tie-in of the boiler may differ slightly, depending on what material the water pipe consists of.
Polypropylene pipe
Pipes not sewn into the wall will not create connection problems. The work will consist in cutting the water supply pipe in the required place and soldering it into the holes of the tees, from which the pipes will go to the boiler. Cranes are connected by ordinary couplings. If the pipes are walled up, then the algorithm of actions will change slightly:
- pipes should be opened;
- tie-in occurs;
- branch pipes are removed;
- pipes are sewn into the wall.
Metal-plastic pipes
Since there is no technology to mount such pipes in a hidden way, the tie-in will not be a problem. Pipes are cut, tees are attached to them and water supply pipes are connected to the heater.
Steel pipes
Connecting to steel pipes is a tricky business. In this case, it is rational to use the mixer pipes, through which the tank will be connected. Tees are put on the branch pipes, by connecting them, the water heater and the mixer are connected to one pipe.
Common mistakes when connecting an indirect heating boiler
A common mistake is not a suitable location for the boiler. It should be installed as close as possible to a heating boiler or central heating outlet - this will help save on the laying of additional pipes and other accompanying infrastructure.
The bathroom is almost perfect for this, the only catch is its small size:
Another "popular" mistake is the incorrect connection of the cold water inlet. Connection in a sequential order of input-output of a substance of thermal energy (heat carrier) must ensure the correct and efficient operation of the boiler.
The best and most effective option for heating and heat supply will be the inlet of the coolant into the water heater from above, and the outlet, respectively, from below.
Incorrect connection of the circulation pump can lead to a lot of adverse consequences, namely:
- a motor axis other than a horizontal arrangement can lead to rapid wear of the bearings;
- An important factor is keeping the pump clean and free of debris. Screen filters should be checked regularly.
Cost of equipment
Potential buyers, faced with the choice of an indirect heating boiler, solve the problem of finding an acceptable price for equipment with optimal functions. The cost of equipment presented in stores varies greatly depending on the model. Here are just some of the factors that affect pricing:
- Manufacturing company. European counterparts, due to the influence of the high cost of EURO, will cost more than the same Korean ones. Nevertheless, the quality level of the leading brands of the Eurozone: ACV, Viessmann, Buderus, Vaillant, Protherm, Drazice, Gorenje, always remains on top, which makes the products in demand on the domestic market.
- materials present in the products and the quality indicator of the performance of the tank.
- Accessories high quality and not so good. Expensive models are equipped with brass or stainless alloy tanks. Hull cladding made of such material also leads to an increase in price.
- constructive solution. The tank-in-tank module results in an increase in cost compared to the traditional design of an indirect heating boiler.
- Overall parameters of the device. Of course, a more capacious tank is offered at an increased cost.
- functionality. Equipping the inlet for the recirculation system requires additional costs for the production process. As you might guess, the seller will include everything in the final price.
At the beginning of 2018, the price for the design of an indirect heating boiler foreign production, with a volume of 100 liters or more, is formed in the region of 50-90 thousand rubles. The cost of a similar boiler with a volume of 300 liters increases to 100 thousand rubles, and for a device with a capacity of 1000 liters, you will have to pay 350-450 thousand rubles.
Conclusion
Based on the numerous positive reviews from owners of indirect heating boilers, you can see that the system is quite popular and in demand. When buying a particular model, almost all the information can be found on the Internet, where you can also consult online stores specializing in such equipment.
For private houses, such structures will be an indispensable tool in saving money, and you can forget about the lack of hot water.
