Indoor heating boiler strapping schemes

Before purchasing and installing the boiler, you should understand some structural features and the principle of operation of the most popular models. There are many types of similar installations that can work simultaneously from the heating system and alternative energy sources.

It is advisable to consider as an example traditional attitudes with a classic coil that work (receive thermal energy) from hot water. First you should deal with the term “indirect heating” in more detail. Classic installations use an electricity connection or natural gas to receive heat. Boilers do not have such advantages. They are connected to the hot water and use the heat of water or other coolant.

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Standard installations have the shape of a round barrel (although today there are already more convenient and compact square models). If you look closely at the product line from well.known manufacturers, you can notice a certain tendency. They all have the same design. This applies to both boilers and gas boilers. You can significantly save space when they are placed by installing one unit on another.

The only element of heating is the coil of brass or steel. It is located inside the case (tank) having a protective layer of enamel. To reduce heat loss, the case is well isolated, and sometimes covered with a protective casing.

If you need to quickly heat water, then you should choose devices with several heat exchangers. For slow cooling of water, you need models with good insulation.

Magnesium anode is one of the most important elements in modern boilers. The part serves to prevent corrosion on all internal surfaces, and the rod itself is inside the structure in its upper part. Thanks to this, the unit serves several times longer. The design must have a thermostat and valves, since they are fuses from a strong increase in pressure as a result of failure of the entire system.

Boiler System Explained: Hydronic Heating

A common myth states that boilers are not effective equipment for heating water, since the temperature of the coolant in the coil does not exceed 70 ° C. This is not true. It all depends on the area of ​​contact of the coolant in the coil with water. It is quite large in the BKN, so the water heats up effectively even at a seemingly low temperature not exceeding 70 ° C.

fill, indirect, heating, boiler

The device works very simple. The boiler capacity is completely filled with cold water for heating. Inside is a coil, into which hot water from the boiler is launched at this moment. Cold water after a certain time heats up and becomes suitable for taking a shower, washing dishes and other household needs.

Varieties and selection of devices

In addition to the elementary design tanks, there are also boilers of a more complex device that allows you to realize some wonderful functions when integrating into the heating system.

One of the most popular functions is the use of a boiler as a heat accumulator. This is especially important for electric heating with an unstable supply of electricity or when working on daily tariffs. Devices with the heat accumulator mode have a significant container (more than 300 liters) and reliable thermal insulation.

Boilers with a recirculation system that provide instant supply of hot water into the mixer are considered more expensive. They have three pipe for connecting to the DHW system: one for supplying cold water and two for a hot duct. Circulation is performed by a small pump. Boilers of this type are less economical, but with their help you can organize a small heating circuit, for example, to install a heated towel rail.

Some boilers have a “tank in a tank” design, the name itself speaks for itself. In the external container is the heating system coolant, in the internal. heated tap water. The advantage of such a design in very rapid heating of water, but due to the complexity of the device, such boilers are much more expensive than usual.

A boiler of indirect heating “tank in the tank”: 1. input of cold water; 2. hot water output; 3. input of central heating; 4. an internal stainless steel tank; 5. central heating exit


The main feature of the connection scheme for any indirect heating boiler (the brand and model here can not be taken into account) is that it is deprived of its own heating unit. Water takes thermal charge from external heating systems.

They can receive thermal energy at the expense of:

  • burning of mineral or organic fuel;
  • electrical resistance effect;
  • contact with the central heating system;
  • Accumulations of sunlight.


With any form of external sources of thermal energy, the work of the boiler goes the same way, with rare exceptions. And even the private innovations of individual firms protected by patent law do not change the essence of a long.established scheme. The portion of heat received from any source goes along the coil built into the drive. Circulation is maintained due to the pump. In close contact with the tubes or tank, where the colder water is originally located, it is heated.

Since even one joule heat, in vain radiated outward, affects the system of the system extremely negatively, it is necessarily equipped with thermal protection. Polyurethane or polystyrene is usually chosen as an impermeable heat for the outflow of heat. The receipt of new doses of cold water naturally comes from the general water supply system. Each new portion passes through specially designed nozzles. As soon as the movement cycle in the coil is completed, the coolant enters the heating system of the house. for this a very special pipe is provided.

Further differences begin further: although most boilers are designed to calculate cold water along the lower move, there are those in which it enters through the top. In a similar design, the liquid must first completely go through the system to the lower point. Variations with the withdrawal of a heated coolant is noticeably less, in almost 100% of cases it is removed from above. It is difficult to find the reason why it should be done otherwise. After all, the upper location allows you to serve hot water for the long time as long as possible in the container at least its small portion.

So that the coil occupies the largest space within the body, it is usually done in the form of a spiral. When the coolant passes several cycles through this pipe, the temperature becomes equal to the heating of the liquid in the boiler itself. At the command of a special relay, a special circuit stops, nourishing the pump. With the subsequent cooling of the coolant to the set value, the relay gives another command. to close the chain. and heating is resumed. The advantages of such a device are quite well known. All these points should be taken into account before the start of work.

Advantages, disadvantages, types of equipment

What is such a boiler is good? The most important thing is that water in it can be heated without unnecessary costs. That is, you will not have to pay for electricity or gas, unlike the same direct heating boilers, which have special heating elements such as burners in their design. The KN boiler uses a ready.made resource of the heating system in the house.

Indirect heating water heater

This aspect also allows us to talk about a reduced load on the mains in the house. At the same time, the productivity of the boiler is quite high, it is safe and able to serve for many years without complaints, because its inner part is even protected from contact with running water. Water from such a boiler comes to the consumer as soon as it turns out.

Cons, of course, the equipment has. This is, first of all, a high cost. it costs more than a direct heating boiler. It should also be understood that the water in it heats up longer, but it lasts a hot. And such a boiler takes up a lot of places, it is better to put it in a separate room at all. And another main drawback. in the summer, to heat the water, you will have to run the heating boiler.

When equipping the DHW system in a private house, the owner often has to decide what is better. an indirect heating boiler or a double.circuit boiler

On a note! There are several types of indirect heating boilers. Let’s see how they differ from each other.

Table. Types of boilers Prince.


Using an indirect heating boiler and electric boiler

On a note! It is important to understand that the smaller the boiler, the faster the water will heat up in it. Although modern structures sometimes allow you to heat a large volume of water in a very short time.

How the boiler power is selected?

Choosing a boiler pr

The choice of such an aggregate as an indirect heating boiler must be approached with all responsibility and, above all, ask yourself the question: “Will it be convenient to use such a device?””. The pluses and minuses of the unit are described above. In this section, we note several aspects that you need to know in order to understand whether it is necessary to buy it. They will also help to choose the right variant of the boiler KN.

    How much will buy such equipment justified? The fact is that it makes sense to buy such a device if the water consumption in the house or room is large enough and is at least 1.5 l/min. For comparison, this is precisely such water consumption is observed in large families with a composition of 4 or more people.

It is also better to take boilers that have some protection elements. safety valves, thermostats, etc. D. Do not be lazy and refuse to fill out a warranty coupon in the store when buying. The boiler is expensive, and it will be insulting, having acquired it, to make sure of the inadequate quality of the goods. And change such equipment without a guarantee is difficult.

The principle of connection

An indirect heating boiler can be connected:

With a priority of hot water. In this case, the entire volume of the coolant passes through the heat exchanger. This can significantly reduce the preparation time of water hot water. When the set temperature is reached, the flow is redirected to the heating system.

Without hot water priority. Only part of the flow of the coolant is consumed to heating water, which increases the time to achieve the desired temperature.

Connecting BKN with a priority is a more profitable scheme that provides hydroelectric power plants in full without a significant reduction in temperature in the heating system. Water heating requires 20-40 minutes, and to maintain temperature at a given level-3-8 minutes. For such a short time, the house cannot cool without heating so much that it can be felt.

It is important that the power of the boiler and boiler is at a comparable level. In an ideal case, the boiler should have a performance supply of 25-30%.

Schemes and features of connecting an indirect heating boiler

When choosing a BKN connection scheme, first of all, pay attention to the class class and features of the heating system at the facility. The installation site is determined depending on the place of the pump insert and the existing wiring. There are several options for connecting an indirect heating boiler, which will be discussed below.

Three.way valve strainer diagram

This option is most often used to connect BKN. The scheme provides for a parallel connection of the heating system and boiler, which is installed near the boiler. The circulation pump is cut on the supply, and behind it is a three.way valve.

The three.way valve is controlled by the thermallane and performs the function of the switch. As soon as the temperature decreases, the automation is triggered, which redirects the coolant to the boiler.

A three.way valve binding circuit is a system with a priority of hot water. It allows you to quickly heat the water in the boiler when the heating radiators are turned off from the flow of the coolant for a while. When the water temperature reaches in the BKN, a three.way valve is triggered, and the coolant begins to arrive on heating devices. Such a strapping is an optimal solution if there is a constant need for a hot water.

Binding circuit with two circulation pumps

With a periodic need for DHW, a boiler is rarely used. In this case, the most optimal is the scheme in which two circulation pumps are present: one is mounted on the supply in front of the boiler, the second on the heating circuit.

The operation of the circulation pump occurs in conjunction with the thermallane. It is included in the work when the temperature is reduced below the given value. Forced circulation of the coolant intensifies the process of heating water in the boiler.

This scheme does not provide for the installation of a three.way valve. For binding, ordinary connecting tees are used.

Binding diagram with a hydraulic arrow

The use of such an indirect heating boiler is advisable if the water heater volume is more than 200 liters or the heating system provides additional contours, for example, a warm floor.

The hydraulic distributor is turned on to simplify the heating system scheme. In this case, there is no need to install circulation pumps on each branch.

The hydraulic shotient does not allow heat strokes, since the pressure in the contours is aligned.

Binding diagram with coolant recirculation

If the system has a contour that requires a constant supply of hot water, then recirculation helps to solve this problem. An example is a heating system with a heated towel rail. The main advantage of this scheme is always at the disposal of hot water.

However, recirculation leads to an increase in energy consumption, since constant heating of water in a cooling circuit is required. In addition, the water is mixed in the boiler, which leads to the temperature difference in the upper and lower part. Thus, at the output, water with a low temperature is obtained.

Manufacturers offer indirect heating boilers, the design of which already provides for recirculation and has noblebags for a heated towel rail. When comparing the cost of connecting a conventional tank using tees and models with recirculation, the latter are more expensive.

Binding diagram with an energy.dependent boiler

When using this scheme, the boiler is installed on a certain elevation in relation to the heat generator and heating devices. In this case, it is better to give preference to the Nasten BCN, which can be installed at the desired height.

Participation in this scheme of floor boilers of indirect heating leads to a decrease in speed, heating efficiency and a decrease in the reserve of water for the hot water.

The advantage of the energy.dependent heating system is the possibility of functioning in the absence of power supply.

Useful tips from professionals

There are a number of important nuances, without knowledge and compliance with which the connection of the boiler to the water supply will be wrong. You should know that the hot water supply system does not need to be equipped with any additional elements, with the exception of the cutting tap. It is installed on the boiler pipe.

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The cold water pipe is installed after preliminary installation of the tee. The tap for the removal of excess cold water from the water heater crashes into the side of the branching of the branch. Also, the return valve and the cutting crane are connected to the tee. The latter connects to the water supply.

When connecting a tank to the water supply, it is forbidden to do the following:

  • open a protective window with the heater on;
  • Test an empty boiler. Previously, the tank needs to be filled with water, otherwise the heater may burn;
  • drain the water without turning off the heater;
  • equip the water heaters with details from other boilers. The exception is the same models, as well as tanks with compatible spare parts.

Briefly about important: safety valve

Safety valve for a water heater

A separate section deserves such an element of the system under consideration as a safety valve. It excludes the possibility of reverse fluid departure into the water supply, and also helps to normalize pressure in the system by discharge of excess water during its heating process.

An important nuance: it is forbidden to install a check valve instead of safety. Because of this, the temperature relay may break, as a result of which the boiler will explode.

The installation of the safety valve is performed at the place of the cold water entrance to the heater. Connection technology prohibits placing elements between the entrance to the tank and are safety valve.

Important! Follow the valve condition during the operation of the tank. If the brass device remains dry for a long time, this may indicate its breakdown. The failed element should be replaced in the shortest possible time.

Now you can connect the heater to the water supply in compliance with all the requirements and nuances of technology. This is a great opportunity to save on plumbing services and keep the whole process under personal control.

The nuances of the strain device

It is easier to make wiring and strapping if the KN boiler is installed along with the boiler, pumps with other equipment participating in the assembly of the DIS system. Cut an additional device into an existing network is much more difficult.

In any case, for the normal operation of the devices you will have to fulfill a number of rules:

  • choose the right installation site. as close to the boiler as possible;
  • provide an even surface to install a boiler;
  • To protect against thermal expansion, install a membrane accumulator (at the output of heated water), the volume of which is not less than 1/10 from the volume of BKN;
  • equip each contour with a ball crane. for convenient and safe maintenance of devices (for example, a three.way valve, pump or boiler itself);
  • To protect against the anti.flow on the pipes of water supply, install the check valves;
  • improve the quality of water by inserting filters;
  • Properly place the pump (or several pumps). the engine axis should be in a horizontal position.

For safety reasons, you can not try to fix heavy devices on drywall or thin wooden partitions. Suitable walls of concrete and brick are. Brackets or other types of holders are fixed with brackets, anchors, dowels.

Regardless of the type of device. floor or wall. if possible it is mounted above the level at which the boiler is installed, or at the same level. For the floor, you can make a pedestal or strong stand up to 1 m high

When installing, the pipes are directed towards the boiler (even if masked in the rear or behind a false.walled). It is impossible to use unreliable equipment, for example, corrugated hoses that do not withstand the pressure and pressure of the water.

For the normal operation of the accumulative water heater, the following functional devices must be included in the strapping:

The complex technical system should be equipped with pumps supplied to the taps of hot sanitary water and stimulating the movement of the coolant along the heating branch, as well as the circuit of water in the boiler, the cold water coming from the general or autonomous water supply should be cleaned through the mud in the boiler or the boiler a system of filters that destroy lime salts. Filtering will prevent the formation of mineral sediment after a mud or water filtration system should be a pressure gearbox. However, it is needed only if the pressure in the branch exceeds the 6th bar before the input of cold water into the boiler, a check valve is required, which will prevent the reverse movement of the flow in order for the heating water to have a reserve for expansion during the period when it is not used, they include the strapping Expande tank and a safety valve for dumping pressure so that hot water that threatens burns does not enter the taps, a three.way mixing valve must be installed in the circuit. It will mix the portion of cold to hot water, as a result, the water redistribution will be water in the water.necessary user so that the heating heat carrier heating the heating heating is received in the “shirt” when it is necessary, a two.way thermostat is installed in it. Its server connects to the water heater temperature sensor

How to choose the right boiler

Important characteristics of an indirect heating boiler are:

  • volume;
  • coil material;
  • tank material;
  • insulation material;
  • the presence of additional heating and alternative heating sources.

Boiler volume

It is necessary to choose the volume of the boiler based on the power of your heating system, since it is on it that the load of heating water has to. If you buy an unit, the volume of which is too large, then there is a possibility that your heating system may not cope with it. This is fraught with the fact that the water temperature in heating devices will be small for heating the room. In order not to lose, you need to find out the volume of the boiler coolant, it should be no more than 30-40% of the volume of water in the heating system, otherwise its performance will noticeably suffer.

What volume of the boiler is needed for your family, it is very easy to determine. On average, a person accounts for 60-80 liters to take a shower. Heating 200 liters occurs about 6 hours. Based on these numbers, you need to take the volume of the boiler, which is enough to cover the needs of the family, taking into account the time until the next heating.


One of the most important parts of the boiler is the coil, so you need to ask in advance about what it is made. Cheap models have a steel coil, which is simply welded to the tank. In more expensive models, it is removable and made of brass, which is much better in many respects. over, the removable option can be dismantled and cleaned from scale.

What is made of the tank is also very important, since the frequent problem of any water heater is a leak. Inexpensive models have a layer of enamel inside, but it quickly forms cracks from the temperature difference. And this, in turn, is fraught with ambulance corrosion of metal

It is best to buy those options in which the tank is made of stainless steel. This can be more expensive, but it will also serve longer, subject to timely replacement of the magnesium anode

And this, in turn, is fraught with ambulance corrosion of metal. It is best to buy those options in which the tank is made of stainless steel. This can be more expensive, but it will also serve longer, subject to timely replacement of the magnesium anode.

How to Remove Air from a Hot Water Boiler

The quality of the insulation is also an important factor in the effectiveness of such a system. Sometimes use ordinary foam rubber, but it loses in many points. It is best if polyurethane and similar materials are used as thermal insulation.

Other parameters

In addition to the fact that the boiler can have two sources of indirect heating of water, it can also be equipped with a heating element as a heat source outside the heating season. Such designs are much more expensive than usual, but they are extremely practical.

The type of boiler can be of two types: wall or floor. It must correspond to the type of heating system. So, if the system is wall, then the boiler should be of this type. Only models can be driven, the volume of which is less than 200 liters.

Basic principles for connecting a solid fuel unit

Considering how to properly connect a solid fuel boiler, it is necessary to pay attention to the basic elements of the strapping that ensure the safety of the functioning of the heat generator. We are talking about a security group and a mixing unit

The security group, which includes a pressure gauge, as well as a safety valve and air vent, mounted on one manifold, is installed directly on the output pipe of the boiler room. The pressure gauge helps to monitor the pressure in the system, the air vent is used to remove air plugs, and the safety valve drops the excess of the steam.water mixture when the pressure exceeds the specified parameters.

The mixing node based on a three.way valve with a thermogol is installed together with the bypass (jumper) connecting the feed and return pipe, due to which a small circulation circuit is formed.

A system that protects the boiler from condensate and temperature shock works, according to the following scheme:

  • While the fuel flares up, the valve overlaps the flow of cooled coolant from the large circuit of the heating system. As a result, the circulation pump drives a small circle in a small circle.
  • A sensor connected to a thermogram of the three.way valve is installed on the return pipe. When the coolant in the reverse pipeline heats up to 50-55 degrees, the thermal head is triggered and pressed on the valve rod.
  • The valve smoothly opens and the cooled coolant begins to go a little into the boiler shirt, mixing with heaps heated from bypass.
  • When all radiators warm up and the return temperature rises to the values ​​safe for the boiler, the three.way valve covers the bypass, completely opening the passage of the coolant flow through the opposite pipeline.

The basic connection diagram of the solid fuel boiler to the heating system is as simple and reliable, the installation of the strapping can be performed independently.

It is important to know how to connect a solid fuel boiler using polymer pipes to avoid common problems:

  • Polymer pipes are unsafe to use to strapping the boiler. they may not withstand an emergency increase in temperature and pressure. Therefore, it is recommended to carry out the strapping with steel or copper, and the polymer pipes are already connected to the collector distributing the coolant through the heating contours. In extreme cases, the metal pipe is mounted only between the boiler supply pipe and the security group.
  • The use of thick.walled polypropylene pipe for the return pipeline on the site between the three.way valve and the boiler pipe leads to the fact that the overhead temperature sensor reacts to the heating of the coolant with a noticeable delay. It is better to install a metal pipe.

Connection of a solid fuel unit with hydraulic heat

fill, indirect, heating, boiler

The pump for the heating system with a forced supply of coolant is installed on the return pipe between the three.way valve and the boiler. This arrangement allows it to ensure the circulation of water or antifreeze in a small circle. It is impossible to put the circulation pump on the supply pipe, since the device is not designed to work with a steam.water mixture that is formed when the coolant is overheated. The stop of the pump will accelerate or provoke an explosion of a heating boiler, since a cooled coolant will stop entering it.

How to reduce the hazard of a strapping

The base diagram of the connection of a solid fuel boiler provides for the use of a three.way mixing valve equipped with a thermogram and a overhead sensor. This equipment is quite expensive, and it can be replaced with a cheaper option. a three.way valve with an mounted thermostatic element. Such a device has a fixed setting. the valve is triggered when the temperature of the medium reaches 55 or 60 degrees (depending on the model).

Installation of a valve supporting a fixed temperature reduces the financial costs of installing a solid fuel unit from condensate and thermal drops. The ability to flexibly control the temperature of the coolant is lost, deviations from a given value can reach 1-2 degrees, but this is not critical.

Joint connection of two boilers

To increase the comfort of heating of a private house, many owners set two or more heat sources working on different energy carriers. At the moment, the most relevant combinations of boilers on:

Accordingly, the gas and solid fuel boiler must be connected so that the second automatically replaces the first after burning the next portion of firewood. The same requirements are put forward to the strapping of an electric boiler with a wood. This is quite simple when a buffer container participates in the strapping circuit, since it simultaneously plays the role of a hydraulic shotgun, which is shown in the figure.

As you can see, due to the presence of an intermediate tank-accumulator, 2 different boilers can serve several distribution contours of heating at once-batteries and warm floors, and in addition to load an indirect heating boiler. But not everyone put the heat accumulator with TT KOTLOL, because this is expensive. In this case, there is a simple scheme, and it can be mounted with your own hands:

Note. The scheme is fair for both the electric and for a gas heat generator working with solid fuel.

Here the main source of heat is a wood heating. After the laying of firewood, the air temperature in the house begins to fall that the sensor of the room thermostat is registered and immediately turns on the heating with an electric boiler. Without a new loading of firewood, the temperature in the supply pipe decreases and the overhead mechanical thermostat turns off the pump of a solid fuel unit. If after some time it is to light it, then everything will happen in the reverse order. In detail about this method of joint connection is described in

Binding method by primary and secondary rings

There is another way of joint strapping of a solid fuel boiler with an electric to ensure a large number of consumers. This is the method of primary and secondary circulation rings, which provides for the hydraulic separation of flows, but without the use of a hydraulic rifle. Also, a minimum of electronics is required for reliable operation of the system, and the controller is not needed at all, despite the apparent complexity of the circuit:

The trick is that all consumers and boilers are connected to one primary circulation ring of both the supply pipeline and the reverse. Due to the small distance between the connections (up to 300 mm), the pressure drop is minimal compared to the pressure of the pump of the main circuit. Due to this, the movement of water in the primary ring does not depend on the operation of the pumps of the rings of the secondary. Only the temperature of the coolant changes.

Theoretically, the main contour can be included as many heat sources and secondary rings. The main thing is to correctly choose the diameters of the pipes and the performance of pumping units. The actual performance of the main ring pump should exceed the consumption in the most “voracious” secondary circuit.

To achieve this, it is necessary to perform a hydraulic calculation and only then it will be possible to correctly select the pumps, so you can not do without the help of specialists. In addition, it is necessary to link the operation of a solid fuel and electric boilers by installing disconnecting thermostats, as described in the next

Features of the design of an indirect boiler

An indirect type boiler is a tank made of stainless steel. The internal walls of the container are covered with special material, which not only protects the surface of the water heater from corrosion processes, but also reduces the concentration of harmful bacteria and microorganisms.

The diagram of an indirect type boiler device with a single.circuit coil

Otherwise, the boiler of the simplest design consists of the following components:

  • heat exchanger. a spiral pipe or a smaller tank. Depending on the volumes of the tank can be located in its upper and lower part;
  • input pipe. a fitting in the lower part of the device for supplying a pipe with cold running water;
  • The output pipe is a fitting for connecting a hot water output pipe;
  • magnesium anode. additional protection of the walls of the tank from corrosion processes;
  • internal thermometer. a device for measuring the temperature of the heating of water;
  • Thermostat is a device that prevents the overheating of the equipment;
  • control unit. rotary handle with divisions for setting heating temperature;
  • Thermal insulation is a layer of insulation material that helps maintain the set temperature of heated water;
  • exhaust hole. a valve for draining stagnant water;
  • Revision. a hole of large diameter, designed for maintenance, repair and modernization of the boiler.

The design of new tanks can differ slightly and have a number of improvements from manufacturers, but in general, any indirect type boiler consists of the listed elements.

The principle of operation of the boiler

The indirect type boiler is part of the heating system and is connected directly to the gas, electric or solid fuel boiler, which heats the coolant due to the energy released during fuel burning.

The coolant circulates through the DHW system and passes through the heat exchanger located in an indirect heating boiler. Due to the return of thermal energy from hot coolant, cold water is heated, which is filled with the tank of the device. From it, heated water through the outlet hole through the pipe is transported to the bathroom, to the kitchen and other rooms with plumbing equipment.

An indirect type boiler can work with any type of heating boilers

When turning off the heating boiler or its transition to an economical mode of operation, the coolant quickly cools down. Thanks to the design, which provides insulation of the walls of the tank with uretany foam, the water in the tank cools very slowly. This allows you to use the entire volume of warm water for another several hours.

Connection of the boiler to the gas boiler

For the correct functioning of a boiler with a gas boiler, there is a temperature sensor in its composition. So that they work together connect a three.way valve. The valve regulates the flow between the main contour and the contour of the hot water.

To a single.optical gas boiler

For such a connection, a strapping with two pumps is used. It is she who is able to replace the scheme with a three.way sensor. The main thing is to divide the flows of the coolant. In this case, it will be more correct to say about the synchronous work of two contours.

To a double.circuit gas boiler

The main connection in this diagram will be two magnetic valves. The essence is this. the boiler is used as a buffer. Cold water comes from the water supply network. DOV entrance valve is blocked. If you open it, then at first water will come from the buffer, which is a boiler. The buffer contains heated water, the consumption of which is regulated by the capacity of the boiler and the set temperature.