If it is possible to connect main gas to the house, then for cooking hot water and an automated gas boiler will be used to heat the house. Today this is a self-evident solution due to its low cost. natural gas and ease of use of the boiler.
The choice is not difficult, but...
There are usually no problems with choosing a gas boiler. It is known that a wall-mounted boiler with a closed burner, in which a short chimney exits through the wall, is most preferable for low heating powers - up to 30 kW.
With the boiler power, everything is also clear - it is selected according to known criteria or according to the recommendations of specialists.
But the difficulty is mainly caused by the question of whether to choose a single-circuit or double-circuit boiler. And also whether an indirect heating boiler is needed or not - after all, this is a significant additional expense. And if you buy a boiler, then how to connect it to the boiler.
Features of each boiler
In a single-circuit boiler, the liquid can be heated in only one heat exchanger to heat the house. There is no heat exchanger for water supply, and the boiler has two hydraulic connections - supply and return for heating.
In a double-circuit boiler, heating fluid and water for hot water supply (DHW) can be heated.
In order to obtain hot water for domestic needs with a single-circuit boiler, you need to connect an indirect heating boiler to it. This is a large container in a heat insulator, inside of which there is a coil for the passage of coolant from the heating system.
The DHW boiler is connected to the heating circuit according to a special scheme. Which, as a rule, provides the so-called “Boiler Priority”. If the water in the DHW system has cooled below the set value, the boiler switches completely to heating the boiler. When the water has warmed up, usually to 50 - 55 degrees, the heating is turned on again.
Additional equipment for connecting the boiler
Additional equipment is installed with the boiler:
- An expansion tank in a domestic hot water system is a device that compensates for the increase in water volume when heated. Capacity – 1/10 of the boiler volume.
- A circulation pump that will provide hot water supply and pressure in the DHW system.
- Safety valve, as well as additional pipelines, taps and other system elements.
You also need to remember that installing all this yourself is not so easy if you haven’t “turned the nuts” before. You'll have to invite a specialist.
It is unlikely that it will be possible to place a boiler with a boiler and other elements of the system in the kitchen. And it’s not rational because of the clutter and noise of the equipment. Therefore, it is advisable to allocate a separate room for it - a boiler room.
Features and disadvantages of a double-circuit boiler
A double-circuit boiler is a mini-boiler room in “one cabinet”, it already has safety devices and circulation pumps, and in
some models and expansion tanks. And all this fits in a small device hanging on the wall.
The performance of direct water heating in the circuit is not high - it is calculated only for one open tap. This means that only one person can take a shower and it is advisable that he is not disturbed at this time by opening a hot tap in the kitchen, and the bathroom should not be too large, since it takes a long time to fill it with high-temperature water. 
Each time the tap is opened, the second circuit of the boiler will be switched on if the water heating mode is set. Frequent switching on of the boiler often simply worries the owners - will it break down prematurely?
Placement of dual circuit
The main purpose of double-circuit boilers is small houses and apartments where the equipment is located near the kitchen, but not far from the bathroom. Short distances are a necessity for this type of boiler; the shorter the path of hot water to the consumer, the better, so that you don’t have to wait too long for hot water to flow.
Experts believe that the maximum distance from the heating circuit to the tap is 7 meters. Anything more and it all just becomes wasteful. The usual distances are from 1.5 to 3 meters. But the priority placement is the kitchen, where the hot tap opens frequently.
When do you need a boiler?
For a large house, where there are significant distances between hot water consumers, and also where there is a high consumption of hot water, or where people want to consume a lot of hot water, you need to choose an indirect heating boiler - it can instantly produce an “avalanche” of heated liquid without significant temperature changes.
You can also make a system of constant circulation of hot water between the tap and the boiler, and if you open the tap even 20 meters from the boiler, you will immediately get hot water.
This is much more economical than waiting a couple of minutes, flushing tons of cold water. In such conditions with a double-circuit boiler, the lack of power in the second circuit will already cause significant inconvenience.
Boiler volume
Typically, boilers with a volume of 80 to 300 liters are installed. The volume of the boiler, in principle, is not very limited by the power of the boiler and is selected according to preference. The greater the number of baths, the larger the boiler needed. Let's just say that for a large bathtub with hydromassage, even 300 liters is not enough - you need 500.
In most cases, the choice is limited to sizes of 100 - 200 liters.
The same volume will very quickly heat up a conventional gas boiler with a capacity of 12 - 20 kW.
Question of price
A double-circuit boiler is only slightly more expensive than a single-circuit boiler. But the kit - a single-circuit boiler, plus a boiler, plus the entire system for the boiler - is quite significant in price - several hundred dollars more expensive than a double-circuit boiler.
Another factor pushing you to make the same choice is the lack of information. People often don’t know why else they need an expensive boiler element and all the difficulties associated with it, and they don’t want to understand it. And this often leads to the following result.
How not to connect a hot water boiler
This situation often happens. Feeling the lack of comfort in using hot water from a double-circuit boiler, residents decide to rectify the situation and buy a boiler. But how to connect it?
The answer would seem obvious - without additional automation, cheaply, directly to the second free circuit of the boiler.
But this cannot be done. The second circuit is limited in temperature to 60 degrees, so that there are no burns from the hot water supply. Therefore, it will never heat the water in the boiler to 60 degrees, even to 50. When heated, the temperature at the return of this circuit will rise to 50 degrees, and the boiler will operate in an abnormal mode, with a minimum flame, constantly turning off and on, etc. Therefore, it remains to connect the boiler, as it should be according to the classical scheme, to a high-temperature heating circuit. 
Boilers with built-in hot water boiler
These are floor-standing devices that resemble a refrigerator in appearance, but can be low-power, i.e. These are adapted samples of wall-mounted boilers. With a boiler capacity of up to 100 liters, they can also be wall-mounted.
The peculiarity is that boilers combined with a boiler can be installed as a separate unit not only in the boiler room, but also in another utility room, is a handy thing when you don’t have enough space, and you don’t need to assemble the system together.
It is not recommended to install any boilers in places where people are constantly present, as they make noise. Installation in the kitchen is rather a necessary measure.
As a result, we figured out when it is worth buying a double-circuit boiler, and when you need a single-circuit one. But in principle, there is an opinion that there is no need to save on the hot water supply system. It should be as comfortable as possible. Therefore, a boiler with a single-circuit boiler is still a priority.
Where the supply of main gas is provided and possible, the owners often decide on the principle gas equipment, which will be located in the house. After all, a gas boiler is capable of not only heating the coolant circulating through the internal circuit and providing heating for the radiators, but also preparing hot water in the boiler for household needs. For such a purpose, it is quite possible to consider purchasing a single-circuit gas boiler with an indirect heating boiler.
What is a single-circuit boiler with an indirect heating boiler
Despite the fact that only one circuit is mounted in such a circuit, such equipment is capable of producing hot water. This occurs due to the fact that a spiral tube is installed in the water heater, which is a thermal container, and the coolant circulates through it. And it, in turn, warms up in a gas boiler. Thus, heat is transferred to the water, and it warms up, which allows you to significantly save electrical energy.
Operating principle
Gas single-circuit boilers with indirect boiler work according to two main connection schemes. The principle of operation of the first is as follows:
- The three-way valve dominates here. A pump is installed directly into the outlet of the gas boiler, which provides circulation and creates pressure. The next step is to install a three-way valve, which is connected to the boiler thermostat. When heated tap water or other coolant, its flow is directed to the heating system, with priority for the hot fluid entering the boiler coil. This happens with the help of an additional, second pump. And it turns out that in this case hot water supply and heating system connected in parallel, and they can form two circuits, precisely in this closed chain. And after the boiler, an additional pump is installed, which helps regulate the operation of the thermostat. The principle of starting and stopping the process is also regulated by a thermostat, namely, when the heating is strong, the fuel supply is forced to shut off, when the coolant cools down, the fuel is passed through again, and the burner is automatically ignited.
- If there is no double circuit and priority is not given to heating hot water, the boiler is mounted in common system, installed in convenient location, and water heating occurs on a par with all radiators.
Specifications
When choosing a model of the system in question, the technical characteristics must correspond to the level of expected comfort and the amount of heat and hot water used. Since they will vary greatly depending on the area of the room and the activity of using the system. Because some owners visit private houses only for a short period of time, while others live in them permanently.
The number of people living and the presence of pets also greatly influences. Because, in any case, the more people live, the more hot water is used. Therefore, when choosing a model, it is necessary to take into account all the characteristics of the heated object in order to choose the best option.
Installation features
Installation features include the following:
- the entire piping of the water heater itself must be connected not only to the heating system, but also to both water supply lines, that is, to both cold and hot water;
- It should be noted that the cold water input is connected to the system from below, and the hot water is discharged from the top of the tank, while the recirculation point is located approximately in the middle of the boiler tank;
- the heated coolant must move along the circuit from top to bottom;
- It is worth noting that the coolant liquid moves to the upper nozzle, and then returns back into the bosom of the heating line from the lower nozzle of the container. It is this feature that helps increase efficiency, since heat is initially transferred to the warmest layers of the coolant;
- it is important to know in what ways you can connect the boiler so that it works correctly, making the most of its resources;
- It is for a single-circuit gas boiler with an indirect heating boiler that a sensor is provided that regulates the temperature, and it is installed directly in the tank;
- When connecting a boiler to a single-circuit boiler, it is necessary to use a circuit with two circulation pumps. It is important to note that this type can replace the previously discussed three-way sensor circuit;
- it is important to know that the connection features also include the separation of flows through which the coolant moves;
- due to the way the heating system assembly algorithm is configured, either the water heating system or the circuit where the coolant circulates can take precedence in receiving heat;
- The thermostat also regulates the alternating activation of both pumps installed in the tank.
Requirements for the location of such a boiler
Single-circuit gas boilers are divided into floor-mounted and wall-mounted, and, depending on the model purchased, there will be special requirements for the room:
- For you need:
- the presence of at least one window in the room where the boiler itself will be located;
- you need to install a chimney;
- The boiler is best located close to the boiler.
- For you need:
- equipment of a separate room;
- insulation of walls with non-combustible materials;
- chimney organization;
- supply and exhaust ventilation equipment;
- mounting a boiler either near the boiler, or good insulation of the pipe that will supply hot coolant to the boiler installed in the house;
- organization of a concrete area for installation of the boiler structure itself.
Hot water is used every day in everyday life, and the central water supply does not fully satisfy this need.
In some places there is no possibility to connect to the public highway at all. In this regard, there has been widespread gas boilers.
A gas boiler is heating equipment for heating the coolant, which works by burning gas. Some types of boilers can provide both heating and hot water supply (DHW) at the same time - these are double-circuit boilers. Others are used only for heating - single-circuit.
A double-circuit gas boiler heats cold water using a flow-through circuit, which ensures a continuous flow. Heating occurs due to direct heat from the flame.
Water consumption depends on the boiler power. On the one hand, this is very effective way provision hot water, but on the other hand there is a drawback.
Tap water is used for heating; it has a high hardness level (salt content). Therefore, when heated, scale formation occurs on the walls of the heat exchanger.
If you do not control the process of scale formation, this can lead to a malfunction of the gas boiler.
Just a note.To reduce the hardness of heated water, special devices are used - softeners.
DHW using a single-circuit boiler
Despite the obvious advantage of double-circuit boilers, both types are popular. In fact, they are also capable of participating in heating hot water for the household, but this requires an additional water heater.
This heater is an indirect heating boiler.
Indirect heating boiler
A boiler is a reservoir inside which a heating element is located, most often. That is, the energy source is located inside the boiler itself. In our case, an indirect heating boiler is used.
“Indirect” means that there is no source of thermal energy inside the boiler. Heating occurs due to the heat from the gas boiler. Inside the boiler, as a heating element, there is a coil.
The same coolant that is used for heating enters this coil and heats the cold water that fills the boiler. In other words, the heating fluid heats cold water for domestic use.
The design of an indirect heating boiler includes two non-communicating water circuits:
- Heating water circulation circuit – heating circuit. The flow pattern of the coolant begins in the gas boiler, then it enters the boiler coil and gives off its thermal energy cold water in the boiler and returns back to the boiler for heating. This cycle repeats continuously.
- Flow circuit domestic water– heated circuit. For heating, water from the water supply is used, it enters the boiler tank, coming into contact with the heat exchanger, the water heats up and at the exit from the boiler has a temperature of 45-65 ° C.
Types of indirect heating boilers
Due to the great demand for water heating equipment, they have many different modifications.
A wall-mounted or hanging boiler has compact dimensions. Due to wall mounting, it takes up virtually no space. These types of boilers have found their application in apartments and small private houses.
A floor-standing or stationary boiler has a wide choice of sizes and capacities, and can also be made in a vertical or horizontal arrangement. This type of boiler can provide a constant large supply of hot water.
To heat water in an indirect type boiler, you can use any heat source: a boiler liquid fuel or solid fuel, electric boiler, wall-mounted or floor-standing gas boiler.
There are types of indirect heating boilers that are equipped with additional electrical heating elements. If for some reason the gas boiler cannot function normally, you can always heat the water using an electric heater.
The tank is made of stainless steel with additional protective coatings. The heat exchanger is made of copper, as it has good thermal conductivity properties. To preserve heat, the boiler is packaged in thermal insulation material.
Main characteristics of an indirect heating boiler
Indirect heating boilers have the following characteristics:
- tank volume;
- water heating speed;
- power consumption;
- heat losses;
- the presence of an additional heat source (TEH).
For the normal functioning of the boiler, heating and indirect heating boiler, it is necessary to correctly select the power of the gas unit.
The power of a gas boiler must be at least twice as large as the energy consumed by the boiler. Otherwise, the water in the boiler will not heat up quickly enough, and the heating system will not work efficiently.
Attention!The connection diagram for a gas boiler must provide for disconnecting individual coolant consumption circuits. So that it is possible to turn off the heating, but the boiler continues to function and vice versa.
For example, the power of a boiler for a house of 100 m2, with a rough calculation, can be 20 kW. (2 kW per 10 m2 area). In this case, the maximum boiler consumption should not exceed 10 kW. But it is best to have a reserve of boiler power.
Thus, with the correct selection of equipment, you can achieve normal and continuous operation heating and hot water supply.
A floor-standing gas boiler with a boiler is distinguished by the ability to quickly supply hot water in the required volume. The storage tank can hold from 40 to 500 liters.
Double-circuit gas boilers with a built-in boiler for hot water supply are essentially single-circuit units with an indirect heating tank, combined into one compact system. Such heating devices are equipped with a heat exchanger, which heats the water during breaks between heating support. Thanks to this design, the gas boiler will always have a supply of warm water. Examples of units are the Protherm Bear 30 KLZ models with a 90 l boiler, Baxi GALAXY 280 i with a 100 l capacity, Beretta Boiler 28 BAI with a 60 l boiler.
Pay attention! A unit with a built-in boiler can provide up to 3 water intake points, depending on the volume of the container. The built-in boiler holds from 40 to 100 liters of liquid.Advantages and disadvantages of units
The advantages of floor-standing gas boilers with a built-in boiler include:
- possibility of constant supply of hot water supply;
- compact dimensions;
- ease of use;
- the presence of many additional functions.
The disadvantages of dual-circuit units are:
- high price;
- dependence on electricity;
- complex installation.
Operation of a gas boiler with an indirect heating boiler
An indirect heating boiler is a separate container that can be equipped with both a single-circuit and a double-circuit gas boiler. Single-circuit units are equipped with an indirect heating boiler to ensure the production of hot water, since these devices are designed only for heating.
To dual-circuit gas heating boilers connect additional capacity if the volume of the built-in boiler or the performance of the flow-through heat exchanger is not enough.
Advantages and disadvantages of boilers with indirect heating boilers
Advantages of gas floor standing boilers, equipped with an indirect heating boiler, have the following:
- possibility of installing a non-volatile system;
- there is no need to purchase a full-fledged boiler.
The disadvantages of such heating devices include the following:
- take up a lot of space;
- There may be difficulties when connecting the container to the boiler.
Selecting boilers with a boiler
A properly selected boiler will cover peak hot water needs. Floor-standing units differ in the type of combustion chamber:
- Atmospheric - with an open combustion chamber. Installed in a specially prepared boiler room with a classic chimney.
- Turbocharged - with a closed combustion chamber. Setting up a special room is not necessary. To remove smoke, it is enough to install a coaxial chimney.
When choosing a boiler with a boiler also take into account:
- required power;
- DHW capacity reserve;
- amount of hot water consumed;
- adaptation to domestic operating conditions;
- Availability of service centers nearby.
The required power of a gas boiler is calculated on the basis that 1 kW of energy is needed to heat an area of 10 m². To heat the water you need to add about 30% additionally. The capacity ranges from 40-100 liters for household equipment and up to 500 liters in industrial devices.
Pay attention! In order not to encounter difficulties when connecting an indirect heating boiler to your boiler, it is better to purchase a container from the same manufacturer as the gas unit.Piping a gas floor-standing boiler with a built-in boiler
The piping scheme for a gas boiler with a built-in boiler includes five pipes: one gas and four water. Gas connections should only be made by a specialist; water pipes can be connected yourself. The gas main is connected using ball valve. The rest are connected as follows:
- heat exchanger pipe with heating supply pipe;
- another main circuit pipe with a return pipe;
- water supply with boiler pipe;
- warm water supply tap with a second tank connection.
This connection scheme has two undeniable advantages compared to piping a conventional double-circuit boiler with an instantaneous water heater:
- the heat exchanger does not become clogged with sediment that remains when the liquid is heated;
- When using hot water, the heating does not turn off.
Which boiler to choose with a floor-standing boiler depends on the specific situation. If you already have a gas boiler with certain indicators of domestic hot water production, then it is advisable to supplement it with an indirect heating capacity for the missing volume. If you choose a new unit, then you should clearly calculate the expected need for hot water and select the appropriate boiler.
People who do not have enough space in their apartment or house to equip a boiler room often try to save space and purchase a double-circuit boiler. This is a smart choice, however, in order to provide the family with hot liquid for the bath and everyday life, care should be taken to have additional equipment. Choosing a suitable tank is not difficult; you can take a tank or other container. However, to make the task easier, you can simply buy a special gas boiler with a boiler.
Possibility of connecting a boiler
A boiler for a gas boiler is a storage tank, inside of which a heat exchanger is located. This model is essentially a dual-circuit model, as it has connections for both the heating system and the hot water supply.
Double-circuit models have a built-in instantaneous water heater, which single-circuit models cannot boast of. The advantage of a gas boiler with a built-in storage tank is that there is no need to create an indirect heating boiler. In addition, the water is heated much faster than in single-circuit options and does not reduce the efficiency of the heating fluid.
A separate boiler can also be connected to double-circuit boilers to provide more hot water. Such equipment belongs to the layer-by-layer heating technique. You can also buy a double-circuit gas boiler with a built-in indirect heating boiler. Such devices are combined with the boiler, although separate devices can be purchased. Depending on what is best for you: ease of transportation and installation or compact placement, you can choose a separate or adjacent model.
If a single-circuit boiler is already installed, you can purchase a special layer-by-layer heating boiler for it, which is equipped with a flow-through liquid heater. If you need to save space in your apartment, you can opt for a single-circuit boiler with a built-in indirect heating boiler.
Heater power
Depending on the power of the gas burner, the liquid flow rate in the instantaneous water heater varies. Also, the rate of water heating depends on design features heat exchanger. A feature of heating the liquid is its short contact with the heat exchanger, so in order to warm the coolant to the desired temperature, a lot of heat is needed. To increase the performance of the heating element, you need to increase the burner power and increase the gas flow.
In order for the water temperature in the shower to be 40 degrees, you will have to set the burner to produce a power of 20 kW, but if the burner is not designed for such power, then it is impossible to take a warm shower. For a bath, you also need to have a powerful burner, since the water must heat up quickly in large volumes for a normal set.
Most boilers have a power of about 20–30 kW, and 10 kW is enough to heat a house. Thus, the entire difference can be used to provide domestic hot water. For hot water boilers, modulating burners have been developed that cover a range from 30 to 100 percent of maximum power.
However, even the weakest boilers have excess power, which leads to frequent turning on and off of the burner. This process leads to rapid wear of equipment and increases fuel consumption. These problems make purchasing a more powerful boiler model to provide more hot liquid an unprofitable and unjustified solution.
That is why double-circuit models have a boiler that holds hot water, which allows it to be released in large volumes while taking a shower or bath. Thus, layer-by-layer heating of water is optimal: it ensures normal operation of the equipment and does not lead to burner wear.
In dual-circuit models with stratified heating, water is heated using a plate radiator or tubular water heater. The presence of an additional heat exchanger is beneficial in condensing models, as it provides additional heat from combustion products. The liquid enters the boiler with layer-by-layer heating already heated, which allows you to quickly prepare hot liquid in the required volume.
Floor-standing double-circuit gas heating boilers with a boiler have a number of advantages.
- The flow of hot water into the upper layers of the boiler allows you to take a shower 5 minutes after turning on the heat exchanger. In contrast, boilers with an indirect heating boiler provide longer heating of the liquid, since time is spent convecting warm water from below the heat source.
- The absence of a heat exchanger inside the storage tank allows you to collect more warm water for domestic needs. The performance of such boilers is 1.5 times higher than in models with indirect heating.
Operation of a gas boiler with a boiler - video
Frequently Asked Questions
Most often, people do not understand why there is also a boiler in the boiler. The fact is that the built-in model allows for comfortable use of warm water. This allows you to quickly ensure the availability of hot liquid when opening several water intake points, something that a conventional double-circuit boiler could never cope with.
Moreover, there are cases when a small pressure of warm water is needed, which a boiler with an instantaneous water heater is not capable of, since it has a limited lower pressure limit.
Floor-standing models with a built-in storage tank are similar to a refrigerator. They hold up to 100 liters of liquid, which is enough to provide warm water for an entire family.
The connection diagram for a double-circuit gas boiler with a boiler is practically no different from the standard connection. An important difference is the need to connect not only to the heating system, but also to the water supply. It is necessary to cut into the system before the water exit points, but after the toilet. This will ensure the release of hot liquid from all water intake taps. It is best to consult with specialists to connect everything correctly.