How to choose an expansion tank for an indirect heating boiler. Indirect heating boiler - what is it? Boiler for indirect water heating

06.04.2020

To arrange supplies hot water operating from the heating system, put a double-circuit boiler. Its disadvantage is low productivity. Hot water is only enough for washing hands or dishes. For comfortable bathing, it is better to install a boiler indirect heating, the advantage of which is the 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 the gas water heater is powered by 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 the solar system or 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.

Choosing for home use boiler, 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. A hollow plasterboard partition will not withstand a water tank.
The floor water heater is designed for a large capacity. Household models are usually produced with storage capacity 250–300 l. 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. After a couple of years, the protective layer is broken and a leak appears.
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

Do right choice 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 such a large number of people DHW consumption 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 a simple reading of the water meter. 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 the 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 heating system wiring, 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 across all lines, and together with an indirect boiler they will get three, 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 the outlet of the faucet hot water before the liquid in the storage tank of the boiler is completely heated.

Popular Models

Choose suitable model always need to 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. Fast heating of water is carried out due to the heat exchanger with total area 1 m 2. The temperature is controlled by a thermostat. Maximum allowable 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

Powerful device with steel storage tank 200 l equipped with a 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.

Indirect heating boilers are different from all other sources warm water the fact that this design does not have its own heating element. Water heating in such a system is carried out due to the influence of external heating devices. It can be a boiler, central heating or solar panels.

The principle of operation of an indirect heating boiler

A distinctive feature of the principle of operation of an indirect heating boiler is that this device only works together with external sources of heating. From this source, a coolant is supplied through a coil located inside the boiler. Thanks to the operation of the pump, the coolant circulates and thereby heats the existing water. The whole system is closed thermal insulation materials(styrofoam or polyurethane) to reduce heat loss.

Cold water enters the boiler tank through the water supply pipes. Special pipes are used to connect to the heat carrier supply source. After going through the entire cycle through the coil, the heat source returns to the heating system through the outlet pipe. When choosing a boiler, you should be guided by the power of the heating source, if this value is insufficient, the water will not have time to heat up to the desired temperature.

Water connection

For an uninterrupted supply of warm water, the rules for connecting an indirect heating boiler should be strictly observed. The main nuance of the connection is that cold water must be supplied from below, i.e. the inlet pipe is connected at the bottom of the boiler. However, there are boilers where the entrance to the supply cold water located at the top - this means that the water goes through the entire system to the lowest point.

As for the hot water outlet, it is located, as a rule, at the top. The branch pipe takes the upper layers of water, which are always the hottest in the tank. Thanks to such a system, hot water will be supplied until not a single gram of warm water remains in the tank, only after that cold water will go.

The piping of the indirect heating boiler can be carried out with my own hands, but for this you need to know some connection features. The coil, through which the coolant moves from the source, is a spiral pipe that runs along the entire length of the boiler. Under the influence of the buoyancy force of the pump, the coolant passes through the circuit and is cooled in cold water to a certain temperature. After several cycles, the temperature of the coil equalizes with the temperature of the water inside the boiler, at which point the relay is activated, opening the electrical circuit in the electric pump.

As soon as the water temperature drops to a certain level, the circuit closes again and the supply of hot coolant to the coil resumes. For greater heating efficiency and reduced energy costs, the coil must be connected from above to the coolant source. Otherwise, the coolant would not be cooled to the maximum value, passing warm layers of water at the end of its path, due to which the efficiency would decrease. Below is typical scheme connection of an indirect heating boiler to a heat source and its connection to consumers of warm water.

Benefits of an indirect heating boiler

Among a large number advantages of indirect heating boilers, many note the absence of energy costs. However, this statement is not entirely true, energy costs are present due to the cooling of the coolant, but they are several times less than when using boilers powered by electricity or other energy sources. In addition, indirect heating boilers have more power than many analogues, which means that water can heat up much faster. This advantage allows you to connect the boiler to several hot water consumers, for example, a faucet in the bathroom and in the kitchen at the same time.

The main advantages of an indirect heating boiler:

Reducing energy costs;
Large production capacity;
Heating speed;
Ease of connection;

The disadvantages of boilers of this type include the fact that they depend on the connected heat sources. For example, if the heating system acts as this, then in summer time she won't work.

In this case, you have to use electricity, for this, almost all models of boilers are equipped with electric heating elements.

Boilers of indirect heating are slightly more expensive than electric analogues of the same volume. Another disadvantage is the energy consumption for space heating for water heating. In private homes, this problem is solved by increasing the fuel supply. In any case, as a result, energy losses will be lower than when using alternative ways getting hot water.

Analyzing the numerous reviews of the owners of indirect heating boilers, we can conclude that this system is widely in demand. Despite the fact that many are faced with the problem of warm water supply in summer period year, this problem is still solved.

Even if the design of the boiler does not provide heating from electricity, do not despair. In order not to waste a large number of fuel for the operation of the heating system, it can be switched to an economical mode. To do this, it is only necessary to block all heating circuits, with the exception of what is supplied to the boiler.

Video: connecting an indirect heating boiler

Updated: 16.09.2018 15:03:29

Judge: David Lieberman

*Overview of the best in the opinion of the editors of the site. About selection criteria. This material is subjective, is not an advertisement and does not serve as a guide to the purchase. Before buying, you need to consult with a specialist.

Among the wide variety of water heaters, buyers show particular interest in indirect heating boilers. Outwardly, these models do not differ from conventional storage devices. Most often, manufacturers stop at a rectangular or cylindrical shape corps. At indirect boilers has its pros and cons. Experts recommend paying attention to several technical parameters.

How to choose an indirect heating boiler

Power heater is selected taking into account the volume of the tank and the desired rate of water heating. When studying the documents for the boiler, it is necessary to take into account the useful power of the device.
capacity water heating tank depends on the number of users. To take a shower in the country for a couple of avid gardeners and gardeners, a 100-liter drive is enough. If the family is large, there are small children, then more capacious boilers (200-300 liters) should be preferred. But at the same time, the power of the heat exchanger should be greater so that the heating of the water does not drag on for a long time.
Heating rate also depends on the area of the heat exchanger. To find the optimal combination, you can start from the following ratio. The heating rate of water with a volume of 120 liters with a coil area of 1 sq. m will be about 30 minutes.
Reliability and durability boiler is largely determined by the quality of the tank. A stainless steel tank will last the longest, but the price of such models is high. Manufacturers cover tanks made of ordinary steel with enamel or glass-ceramic. Additionally, magnesium anodes help resist corrosion, they also protect the internal cavity from scale formation.
Maintain temperature water in a given interval helps thermal insulation. Budget boilers have a foam layer, more modern products are equipped with polyurethane foam insulation.
Functionality. Various options help to minimize human intervention in the operation of the boiler. This is overheating protection. safety valve, thermostats and thermometers.
Number of water intake points. With the help of a boiler, you can conduct hot water in several rooms. To do this, you need to choose a water heater with several points of water intake.

What is better indirect heating boiler or gas boiler

Boiler type

Advantages

disadvantages

high power

Fast water heating

Easy setup and adjustment

Multiple water points

Inconvenience of ignition

Gas costs

High price

Indirect

Effective thermal insulation

Can be connected to different power sources

High performance

No additional costs

Performance depends on the temperature of the coolant

Large dimensions and weight

Attachment to the source of energy

Rating of the best indirect heating boilers

Nomination	place	Name of product	price
The best indirect heating boilers with a volume of 100 l	1		62 100 ₽
	2		26 900 ₽
	3		18 361 ₽
The best indirect heating boilers with a volume of 150 l	1		39 451 ₽
	2		42 040 ₽
	3		21 700 ₽
The best indirect heating boilers with a volume of 200 l	1		49 250 ₽
	2		56 580 ₽
	3		24 600 ₽
The best indirect heating boilers with a volume of 300 l	1		114 000 ₽
	2		60 362 ₽
	3		36 400 ₽

The best indirect heating boilers with a volume of 100 l

Indirect boilers with a small tank (100 l) are in demand among single residents or families consisting of 2 people. Devices of this type are installed in apartments or cottages. The experts selected several models.

The most modern indirect heating boiler in design is the Belgian development ACV Smart 100. The water heater is a heat exchanger that uses two stainless steel tanks. The tank-in-tank system is different in that the coolant heats the contents of a small tank over the entire area. This approach allows you to heat twice as much water in the same time as traditional way using a coil. The maximum temperature is limited to 90ºС.

Experts gave the first place in the rating of the model for high-quality thermal insulation. The manufacturer used polyurethane foam 50 mm thick, which is famous for its low thermal conductivity. Experts also speak flatteringly about the wavy surface of the tank, due to which self-cleaning of scale occurs.

Advantages

modern design;
effective thermal insulation;
self-cleaning from scale;
fast heating of water;

disadvantages

high price.

The indirect heating boiler Electrolux CWH 100.1 Elitec allows you to heat water up to 100ºС. In this component, it outperforms its competitors. The capacity of this small water heater is 390 l/h. Both the heat exchanger and steel tank covered with a double layer of glass enamel. To extend the life of the boiler, a large magnesium anode is installed inside. The manufacturer also took care of the thermal insulation, the water remains hot for a long time due to the use of a 75 mm thick insulation. Additionally, you can install a heating element, which is important in the summer.

Although the device is somewhat inferior to the winner in terms of innovation and efficiency, it is affordable, and guarantee period service is 10 years.

Advantages

high performance;
reliable protective coating;
effective thermal insulation;
several points of water intake;

disadvantages

small heat exchanger area;
heavy weight (55 kg).

At the most affordable price, the Gorenje GV 100 boiler is sold on the domestic market. The quality of the heater is quite high. The role of a heat source is played by a tubular carrier, which allows you to connect the boiler to different heating mains (even to central heating). Water can be heated up to 85ºС, the manufacturer has provided several points of water intake. The model has all the main options, it is a thermometer, indication of switching on and heating, overheating protection, safety and check valve. The heat exchanger is made of stainless steel, and the steel container is covered with enamel. Magnesium anode provides additional anti-corrosion protection to the tank. Users do not complain about the quality of workmanship, but the search for spare parts and mounting elements becomes a serious problem.

Advantages

versatility of connection;
low price;
rich functional content;

disadvantages

lack of spare parts and components.

What is better indirect heating boiler or double-circuit boiler

HEATER TYPE

ADVANTAGES

LIMITATIONS

INDIRECT HEATING BOILER

HIGH VOLUME

HIGH-QUALITY HEAT INSULATION

MINIMUM SCALING

HIGH PRICE

LARGE OVERALL DIMENSIONS

DOUBLE-CIRCUIT BOILER

AFFORDABLE PRICE

HIGH RELIABILITY

EASY OPERATION

LOW PERFORMANCE

PRODUCES A LOT OF SCALE

The best indirect heating boilers with a volume of 150 l

Boilers with a storage tank of 150 liters can provide hot water to residents of apartments or houses in the amount of 2-3 people. They are affordable and compact in size. Here are some successful water heaters.

Boiler indirect heating Vaillant uniSTOR VIH R 150/6 B has a stylish appearance. It can be installed in any premises, the manufacturer has provided vertical mounting with top strap. The device allows you to heat water up to 85ºС, and the inlet pressure can reach 10 atm. A powerful heat exchanger (25.5 kW) quickly heats up the contents of the tank, and effective thermal insulation keeps the water hot for a long time. The tank is made of ordinary steel, which is covered with a layer of enamel. The magnetic anode becomes in an additional way protect the tank from corrosion.

Advantages

stylish design;
magnetic anode;
fast heating;
high water temperature;

disadvantages

heavy weight (79 kg).

One of the most popular indirect heating boilers is the Italian Baxi model Premier Plus 150. The excellent quality of the product is recognized by experts in different countries. The storage tank is made of stainless steel, which is highly resistant to corrosion. The efficient polyurethane foam insulation helps keep heat loss to a minimum. A tubular coil will cope with fast and uniform heating of water.

The high strength and reliability of the boiler is perfectly combined with lightness (31 kg), so the user can choose between wall or floor mounting.

Advantages

high efficiency;
effective thermal insulation;
lightness and compactness;
quality assembly;

disadvantages

high price;
incomprehensible installation instructions.

The Hajdu AQ IND150SC floor heater attracts the attention of potential buyers with an affordable price. The model is capable of serving several points with hot water. The manufacturer provided for the possibility of installing an electric heater with a power of 2 or 3 kW. The inner surface of the tank is covered with glass enamel, which permanently protects the steel from corrosion. The heat exchanger is made of ordinary steel with protective enamel. Thermal insulation made of polyurethane foam in combination with a polymer paint layer on the outer surface allows the water to remain hot for a long time.

Advantages

affordable price;
reliable thermal insulation;
good equipment;

disadvantages

coil leaks are noted;
service difficulties.

The best indirect heating boilers with a volume of 200 l

Full-fledged families of 3-4 people need a lot of hot water, especially in the summer. Boilers of indirect heating with a volume of 200 liters are capable of ensuring uninterrupted supply. Experts have chosen the following models.

Users call the Viessmann Vitocell-V 100 CVA-200 boiler a reliable heating device. Its work is stable, the unit is easy to operate, the service life is more than ten years. Powerful heat exchanger (36 kW) with an area of 1 sq. m quickly heats water up to 95ºС. The steel tank is protected by an enamel coating, and a magnesium anode is additionally installed, which is powered by a third-party energy source. The manufacturer effectively isolated the tank from the outside world with the help of eco-friendly insulation.

The boiler deservedly becomes the winner of the rating for the optimal combination of price and quality. Users are satisfied with the reliability and uniform heating of water.

Advantages

fast heating of water;
long service life;
high heating temperature;
reliable protection against corrosion;

disadvantages

not detected.

To speed up the process of heating water with a volume of 200 liters to a temperature of 90ºС, the Ariston BC2S CD2 200 boiler was equipped with two heat exchangers. Thanks to this constructive solution, it was possible to bring the heat exchanger area to 1.8 square meters. m. The heater can be connected to gas boilers and solar collectors. Manufacturer applied comprehensive protection, the inner surface of the steel tank is covered with a layer of fine enamel. The magnesium anode helps fight corrosion. The layer of polyurethane foam allows to reduce heat loss. The thermostat prevents overheating of water, the device has a safety drain valve. In the absence of water in the tank, protection against turning on the heating is provided.

Experts put the boiler in the second position in the rating for its large weight (111 kg).

Advantages

two heat exchangers;
high performance;
the presence of protective options;
durable anti-corrosion coating;

disadvantages

great weight.

Indirect heating boiler Hajdu AQ IND200SC was liked by specialists at an affordable price and stylish design. The model is able to heat water up to 65ºС at a maximum water pressure of 6 atm. Experts note good power (32 kW) and a large heat exchanger area (1.06 sq. M). To protect the inner surface of the tank, a glass-ceramic coating is applied, and the coil is made of an enameled pipe. The magnesium anode helps fight corrosion. The manufacturer has provided the possibility of installing an electric heater with a power of 2 or 3 kW.

Another boiler with a progressive "tank in tank" system becomes the winner in our ranking. This is the ACV Smart Multi-Energy 300 model, which is floor version water heater. The device is designed to provide hot water to cottages, offices and production shops. A well-designed design allows you to connect the boiler to the heating systems of residential and industrial facilities. Thermal power is 32 kW, however, the storage device is economical. This is due to excellent thermal insulation, for 8 hours the water temperature drops by only 3ºС.

Experts highly appreciated the use of stainless steel for the manufacture of tanks and components, which makes the boiler exceptionally reliable and durable. In addition, it is also the lightest (99 kg).

Advantages

high power;
reliability and durability;
several points of water intake;
quality manufacturing;

disadvantages

high price.

The high power of the Buderus Logalux SU300 indirect heating boiler is provided by a smooth-tube heat exchanger. It is able to quickly heat water up to 95ºС. The manufacturer chose to make the storage tank out of ordinary steel, thermal glaze was used in combination with a magnesium anode to protect against corrosion. Thermal insulation made of thick polyurethane foam (50 mm), which does not contain dangerous fluorine and chlorine hydrocarbons, helps to keep the high temperature of the water.

The model is located on the second position not only because of the steel tank, the large weight (145 kg) also made a negative contribution. It is not surprising that the installation of the tank is provided only on the floor, and they help to quickly level the boiler. adjustable feet. Users like the model for the optimal combination of price and quality.

Advantages

quality assembly;
effective thermal insulation;
powerful heat exchanger;

disadvantages

great weight.

The Hajdu STA300C indirect heating boiler has several advantages that helped it climb to the third step in the rating. Firstly, the model is sold in the domestic market at an affordable price. Secondly, you can connect the heater to different energy sources, starting with a gas boiler and ending with solar collector. The manufacturer uses the classic scheme to protect the steel tank from corrosion (glass-ceramic + magnesium anode). Heating efficiency is achieved by a powerful heat exchanger (45 kW) with a recirculation pipe. Possibility of installation of additional TEN is provided.

The boiler is not perfect in build quality, which has prevented it from climbing higher in the rankings. Users note a number of minor flaws that have to be eliminated on their own.

Advantages

connects to different energy sources;
affordable price;
installation of an additional heating element is allowed;

disadvantages

build quality sucks.

Attention! This rating is subjective, is not an advertisement and does not serve as a purchase guide. Before buying, you need to consult with a specialist.

Hot tap water has long ceased to be a luxury. Today it is one of the mandatory requirements of a normal life. One of the possibilities for organizing hot water supply in a private house is the installation and connection of an indirect heating boiler.

What is an indirect heating boiler and what are they

A water heater or an indirect exchange boiler is a tank with water in which a heat exchanger is located (a coil or, according to the type of water jacket, a cylinder in a cylinder). The heat exchanger is connected to a heating boiler or to any other system in which hot water or other coolant circulates.

Heating is simple: hot water from the boiler passes through the heat exchanger, it heats the walls of the heat exchanger, and they, in turn, transfer heat to the water in the tank. Since the heating does not occur directly, then such a water heater is called "indirect heating". The heated water is used for household needs as needed.

One of the important details in this design is the magnesium anode. It reduces the intensity of corrosion processes - the tank lasts longer.

Kinds

There are two types of indirect heating boilers: with built-in control and without. Indirect heating boilers with built-in control are connected to a heating system powered by boilers without control. They have a built-in temperature sensor, their own control that turns on / off the supply of hot water to the coil. When connecting this type of equipment, all that is needed is to connect the heating supply and return to the corresponding inputs, connect the cold water supply and connect the hot water distribution comb to the upper outlet. That's all, you can fill the tank and start heating it.

Conventional indirect heating boilers work mainly with automated boilers. During installation, it is necessary to install a temperature sensor in a certain place (there is a hole in the body) and connect it to a certain boiler inlet. Next, they make the piping of the indirect heating boiler in accordance with one of the schemes. You can also connect them to non-volatile boilers, but this requires special schemes (see below).

What you need to remember is that the water in the indirect heating boiler can be heated just below the temperature of the coolant circulating in the coil. So if your boiler works in low-temperature mode and gives out, say + 40 ° C, then Maximum temperature water in the tank will be just like that. You can't heat it up anymore. To get around this limitation, there are combined water heaters. They have a coil and a built-in heating element. The main heating in this case is due to the coil (indirect heating), and the heating element only brings the temperature to the set one. Also, such systems are good in tandem with solid fuel boilers- the water will be warm even when the fuel has burned out.

What else can be said about the design features? Several heat exchangers are installed in large-volume indirect systems - this reduces the time for heating water. To reduce the time of heating water and for slower cooling of the tank, it is better to choose models with thermal insulation.

Which boilers can be connected to

Boilers of indirect heating can work with any source of hot water. Any hot water boiler is suitable - solid fuel - on wood, coal, briquettes, pellets. Can connect gas boiler any type, electric or oil-fired.

It’s just that, as already mentioned above, there are models with their own control, and then their installation and strapping is more simple task. If the model is simple, it is necessary to think over a system for controlling the temperature and switching the boiler from heating radiators to heating hot water.

Tank shapes and installation methods

The indirect heating boiler can be installed on the floor, it can be hung on the wall. Wall-mounted options have a capacity of no more than 200 liters, and floor options can hold up to 1500 liters. In both cases, there are horizontal and vertical models. When installing the wall-mounted version, the mount is standard - brackets that are mounted on dowels of the appropriate type.

If we talk about the shape, then most often these devices are made in the form of a cylinder. In almost all models, all working outputs (pipes for connection) are brought out at the back. It's easier to connect, and appearance it is better. On the front of the panel there are places for installing a temperature sensor or a thermal relay, in some models it is possible to install a heating element - for additional heating of water in case of a lack of heating power.

By type of installation, they are wall-mounted and floor-mounted, capacity - from 50 liters to 1500 liters

When installing the system, it is worth remembering that the system will work effectively only if the boiler capacity is sufficient.

Schemes and connection features

There are two principles for connecting an indirect heating boiler: with and without hot water heating priority. In priority heating, all the heating medium is pumped through the boiler heat exchanger if required. Heating takes a little time. As soon as the temperature reaches the set point (controlled by a sensor, thermostatic valve or thermostat), the entire flow is again directed to the radiators.

In schemes without water heating priority, only some part of the heat carrier flow is directed to the indirect water heater. This leads to the fact that the water is heated for a long time.

When connecting an indirect heating boiler, it is better to choose a scheme with priority - it provides hot water in the required amount. At the same time, heating does not suffer much - it usually takes 20-40 minutes to heat the entire volume of water, and 3-8 minutes to maintain the temperature at a flow rate. During such a time, no house can cool down enough to feel it. But this is provided that the power of the boiler is comparable to the power of the boiler. Ideally, the boiler is more productive, with a margin of 25-30%.

General rules

To ensure the normal operation of all appliances connected to the hot water comb, a expansion tank for hot water (not for heating). Its volume is 10% of the volume of the tank. It is necessary to neutralize thermal expansion.

Also, shut-off valves (ball valves) are installed in each branch of the connection. They are needed so that each device can be used - a three-way valve, a circulation pump, etc. - if necessary, disconnect and service.

On supply pipelines, they are usually also installed check valves. They are necessary to exclude the possibility of backflow. In this case, the connection of an indirect heating boiler will be safe and easy to maintain.

Installation next to the boiler in a forced circulation system (with 3-way valve)

If a circulation pump is already installed in the system, and it is installed on the supply, and a forced heating boiler can be placed next to the boiler, it is better to organize a separate circuit that comes from the heating boiler. This connection of an indirect heating boiler is implemented with most wall-mounted gas or other boilers that have a circulation pump on the supply pipe. With this connection scheme, it turns out that the water heater and the heating system are connected in parallel.

With this piping method, a three-way valve is installed after the circulation pump, controlled by a temperature sensor (installed on the boiler). One of the outlets of the three-way valve is connected to the boiler pipe to connect the heating. A tee cuts into the return pipeline before entering the boiler, a branch pipe is connected to it to drain water from the heat exchanger. Actually, the tie-in to the heating system is completed.

The way this circuit works is:

When information is received from the sensor that the water temperature is below the set one, the three-way valve switches the coolant to the boiler. The heating system is turned off.
The entire flow of the coolant goes through the heat exchanger, the water in the tank is heated.
The water heats up enough, the three-way valve redirects the coolant to the heating system.

As you can see, the scheme is simple, its operation is also clear.

Scheme with two circulation pumps

Pier installing a water heater in the system circulation pump, but not next to it, but at some distance, it is better to install a circulation pump in the circuit on the water heater. The connection of an indirect heating boiler for this case is shown in the diagram below.

The circulation pump can be installed either on the supply pipe or on the return. In this scheme, there is no three-way valve; the circuit is connected through conventional tees. Switching the flow of the coolant is carried out by turning on / off the pumps, and it is controlled by a temperature sensor, which has two pairs of contacts.

If the water in the tank is colder than the one set on the sensor, the power circuit of the circulation pump in the boiler circuit is turned on. When a predetermined degree of heating is reached, the contacts of the pump are closed, which drives the coolant into the heating system.

Scheme for a non-volatile boiler

In a scheme with a non-volatile boiler, in order to ensure the priority of the boiler, it is desirable that it be higher than the radiators. That is, in this case, it is desirable to install wall models. AT ideal- the bottom of the indirect water heater is above the boiler and radiators. But such an arrangement is not always possible.

The schemes will also work with the floor location of the boiler, but the water will heat up more slowly and in the lower part it will not be hot enough. Its temperature will be comparable to the degree of heating of the return pipeline, that is, the supply of hot water will be less.

With non-volatile heating, the movement of the coolant occurs due to the force of gravity. In principle, it is possible to connect an indirect heating boiler according to the traditional scheme - with a circulation pump in the circuit for heating it. Just in this case, when the electricity is off, there will be no hot water. If this turn doesn't suit you, there are several schemes that will work with gravity systems.

When implementing this scheme, the circuit that goes to the water heater is made with a pipe with a diameter of 1 step larger than the heating one. This is what gives priority.

In this scheme, after a branch to the heating system, a thermostatic head with an attached sensor is installed. It runs on batteries and does not require external power. The desired water heating temperature is set on the thermostatic head regulator (not higher than the temperature at the boiler supply). While the water in the tank is cold, the thermostat opens the supply to the boiler, the coolant flow goes mainly to the boiler. When heated to the required degree, the coolant is redirected to the heating branch.

With coolant recirculation

If present in the system, constant circulation of water through it is necessary. Otherwise, it won't work. All consumers can be connected to the recirculation loop. In this case, hot water will constantly chase in a circle with a pump. In this case, by opening the water at any time you will immediately receive hot water - you will not have to wait until cold water drains from the pipes. This is a positive thing.

The negative is that by connecting the recirculation, we increase the cost of heating water in the boiler. Why? Because running along the ring, the water cools down, therefore the boiler will be more often connected to water heating and spend more fuel on it.

The second drawback is that recirculation stimulates the mixing of water layers. During normal operation, the hottest water is at the top, from where it is fed into the DHW circuit. With stirring, the total supply water temperature drops (at the same settings). However, for a heated towel rail, this is perhaps the only way out.

How to implement the connection of an indirect heating boiler with recirculation? There are several ways. The first is to find special indirects with built-in recirculation. Very convenient - the heated towel rail (or the entire loop) is simply connected to the corresponding pipes. But the price of such options for water heaters is almost twice as much as the price of a conventional tank of the same volume.

The second option is to use models that do not have an input for connecting a recirculation circuit, but connect it using tees.

Increasingly in heating systems alternative double-circuit boilers use boilers of indirect heating or the so-called "tank in the tank". When it is necessary to supply a large amount of water, at several points of draw-off "Tank in tank" become indispensable helpers. The stainless steel boiler is 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 hot water taps are provided due to the increased heat transfer area. Also, a short heating time for newly supplied 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.

AT gas water heaters direct heating circuit is used. 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.