Connecting two boilers to the heating system. A heating system of two boilers is the best alternative for continuous heating of the building. Closed system with heat accumulator

Let's start with the fact that modern house, located with middle lane, there should be 2 boilers. It’s not even necessary to have 2 boilers, but two independent sources of thermal energy – that’s for sure.

We have already written about what kind of boilers or energy sources these could be in the article “”. It describes in more detail which boiler and which backup is needed and can be selected.

Today we’ll look at how to connect 2 or more heat generators into a single heating system and how to connect them. Why am I writing about 2 or more units? thermal equipment? Because there can be more than 1 main boiler, for example two gas boilers. And there may also be more than 1 backup boiler, for example, on different types fuel.

Connecting two or more main heat generators

Let us first consider a scheme in which we have two or more heat generators, which are the main ones and, when heating the house, run on the same fuel.

These are usually connected in a cascade in order to heat rooms from 500 sq.m. total area. Quite rarely, solid fuel boilers are combined together for main heating.

We are talking specifically about the main heat generators and heating of residential premises. For cascade and modular boiler houses for heating large industrial premises may include “batteries” of coal or fuel oil boilers in quantities of up to one dozen.

So, as mentioned above, they are connected in a cascade, when a second identical boiler or slightly less powerful one complements the first heat generator.

Usually, during the off-season and mild frosts, the first boiler in the cascade operates. In cold weather or when it is necessary to quickly reheat the premises, a second boiler in the cascade is connected to it to help.

In a cascade, the main boilers are connected in series to be heated by the first heat generator. At the same time, of course, in this combination it is possible to isolate each boiler and a bypass, which allows water to bypass the isolated boiler.

In case of problems, any of the heat generators can be turned off and repaired, while the second boiler will regularly heat water in the heating system.

There is no special alternative to this system. As practice shows, it is better and more reliable to have 2 boilers with a capacity of 40 kW each than one boiler with a capacity of 80 kW. This allows you to repair each individual boiler without stopping the heating system.

It also allows each of the boilers to operate at its full power if necessary. While 1 high-power boiler would operate only at half power and at an increased clock rate.

Parallel connection of boilers - pros and cons

We reviewed the main boilers above. Now let's look at connecting backup boilers, which should be in the system of any modern home.

If backup boilers are connected in parallel, then this option has its pros and cons.

The advantages of parallel connection of backup boilers are as follows:

Each boiler can be connected and disconnected from each other independently.
Each heat generator can be replaced with any other equipment. You can experiment with boiler settings.

Disadvantages of parallel connection of backup boilers:

We'll have to work more with boiler piping, more soldering polypropylene pipes, more welding of steel pipes.
As a result, more materials, pipes and fittings will be wasted, and shut-off valves.
Boilers will not be able to work together in a single system without using additional equipment- hydraulic guns.
Even after using the hydraulic arrow, there remains the need for complex configuration and coordination of such a boiler system according to the temperature of the water supply to the system, and.

The indicated pros and cons of parallel connection can be applied both to the connection of the main and backup heat generators, and to the connection of two or more backup heat generators using any type of fuel.

Serial connection of boilers - pros and cons

If two or more boilers are connected in series, they will operate in the same way as the main boilers connected in cascade. The first boiler will heat the water, the second boiler will reheat it.

In this case, you should first install the boiler on the cheapest type of fuel for you. This can be a wood, coal or waste oil boiler. And behind it, in a cascade, there can be any backup boiler - be it diesel or pellet.

The main advantages of parallel connection of boilers:

In the case of operation first, the heat exchangers of the second boiler will play the role of a kind of hydraulic separator, softening the impact on the entire heating system.
The second reserve boiler can be turned on to reheat the water in the heating system in the coldest weather.

Disadvantages when using the parallel method of connecting backup heat generators in the boiler room:

Longer path of water through the system with more turns and narrowing in connections and fittings.

Naturally, you cannot directly let the supply from one boiler into the inlet of another. In this case, you will not be able to disconnect either the first or the second boiler, if necessary.

Although from the point of view of coordinated heating of boiler water, this method will be the most effective. This can be achieved by installing bypass loops for each boiler.

Parallel and series connection of boilers - reviews

And here are a couple of reviews from users about parallel and series connection of heat generators in a heating system:

Anton Krivozvantsev, Khabarovsk Territory: I have one, it is the main one and heats the entire heating system. I'm happy with Rusnit, it's a normal boiler, in 4 years of operation 1 heating element burned out, I changed it myself, that's all for 30 minutes with a smoke break.

The KChM-5 boiler is connected to it, into which I built. The locomotive turned out to be a great one, it heats perfectly and, most importantly, the automation of the process is almost the same as that of an automatic pellet boiler.

These 2 boilers work in pairs, one after the other. The water that Rusnit did not heat is heated by the KChM-5 and the Pelletron-15 pellet burner. The system turned out as it should.

There is another review, this time about the parallel connection of 2 boilers in the boiler room:

Evgeny Skomorokhov, Moscow: My main boiler is, it runs mainly on wood. My backup boiler is the most common DON, which is connected to the system in parallel with the first one. It rarely lights up, and anyway, I inherited it along with the house I bought.

But 1 or 2 times a year, in January, you have to flood the old DON, when the water in the system almost boils, but the house is still a little cold. This is all due to poor insulation; I haven’t fully finished insulating the walls yet, and it would be nice to insulate the attic floors better.

When the insulation is completed, I think I won’t heat the old DON boiler at all, but I’ll leave it as a backup.

If you have comments on this material, please write them in the comment form below.

Connection diagram for two boilers with automatic control

Important! The valves must work towards each other, then the coolant from the two boilers will move only in one direction, towards the heating system.

For an automatic system for simultaneous operation of two boilers, an additional part will be needed - a thermostat that will turn off the circulation pump if the system has a wood-burning boiler or any other boiler with non-automated loading. It is necessary to turn off the pump at the boiler. Because when the fuel burns out in it, there is no point in wasting coolant through this boiler, interfering with the operation of the second boiler. Which will pick up the work when the first one stops. With the maximum diameter and the highest brand of thermostat to turn off the pump, you will spend no more than 4,000 rubles and get an automatic system.

Video of the implementation of two boilers in one boiler room

The feasibility of using automatic and manual switching between two boilers

Let's consider the following five options with various units in conjunction with an electric boiler, which is in reserve and must turn on at the right time:

Gas + Electric
Firewood + Electric
Liquefied gas + Electro
Solar + Electro
Pellet (granular) + Electro

Pellet and electric boiler

Combination of connecting two boilers - pellet and electric boilers– best suited for automatic activation and manual operation is also allowed.

A pellet boiler may stop because it has run out of fuel pellets. It got dirty and wasn't cleaned. The electric one must be ready to turn on to replace the stopped boiler. This is only possible with automatic connection. Manual connection in this option is only suitable when you permanently live in a house where such a heating system is installed.

Diesel boilers fuel and electricity

If you live in a house with such a system for connecting two heating boilers, a manual connection is quite suitable for you. The electric boiler will operate as an emergency boiler in case the boilers fail for some reason. They didn’t just stop, they broke down and require repairs. Automatic switching is also possible as a function of time. An electric boiler can operate in tandem with liquefied gas and a solar boiler at a night rate. Due to night rate costs less per 1 kW/hour than 1 liter of diesel fuel.

Combination of electric boiler and wood boiler

This combination of connecting two boilers is more suitable for automatic connection and less for manual. A wood boiler is used as the main one. It heats the room during the day, and turns on the electricity to add heat at night. Or if you are not living in the house for a long time, an electric boiler maintains the temperature so as not to freeze the house. Manual operation is also possible to save electricity. The electric boiler will turn on manually when you leave and turn off when you return and start heating the house using a wood-fired boiler.

Combination of gas and electric boilers

In this combination of connecting two boilers, the electric boiler can act as both a backup and a main one. In this situation, a manual connection scheme is more suitable compared to an automatic one. The gas boiler is a proven and reliable unit that for a long time can work without breakdowns. At the same time, connecting an electric boiler to the system for backup in automatic mode is impractical. If the gas boiler fails, you can always manually turn on the second unit.

By including two or more boilers in a heating scheme, one can pursue the goal of not only increasing heating power, but also reducing energy consumption. As already mentioned, the heating system is initially designed to operate during the coldest five-day period of the year; the rest of the time the boiler works at half capacity. Let's assume that the energy intensity of your heating system is 55 kW and you select a boiler of this power. The entire power of the boiler will be used only a few days a year; the rest of the time, less power is needed for heating. Modern boilers are usually equipped with two-stage blower burners, which means that both stages of the burner will work only a few days a year, the rest of the time only one stage will work, but its power may be too much for the off-season. Therefore, instead of one boiler with a power of 55 kW, you can install two boilers, for example, 25 and 30 kW each, or three boilers: two 20 kW each and one 15 kW. Then, on any day of the year, less powerful boilers can operate in the system, and at peak load, all boilers can be turned on. If each of the boilers has two-stage burner, then setting up the operation of boilers can be much more flexible: the system can simultaneously operate boilers in different burner operating modes. And this directly affects the efficiency of the system.

In addition, installing several boilers instead of one solves several more problems. Large-capacity boilers are heavy units that must first be brought and brought into the room. Using several small boilers greatly simplifies this task: a small boiler fits easily into doorways and is much lighter than a large one. If suddenly during operation of the system one of the boilers fails (boilers are extremely reliable, but suddenly this happens), then you can turn it off from the system and calmly begin repairs, while the heating system will remain in operating mode. The remaining working boiler may not warm up completely, but it will not allow it to freeze; in any case, there is no need to “drain” the system.

Several boilers can be connected to a heating system using a parallel circuit or a primary-secondary ring circuit.

When working in a parallel circuit (Fig. 63) with the automation of one of the boilers turned off, the return water is driven through the idle boiler, which means it overcomes the hydraulic resistance in the boiler circuit and consumes electricity by the circulation pump. In addition, the return flow (cooled coolant) passing through the idle boiler is mixed with the supply (heated coolant) from the operating boiler. This boiler has to increase water heating in order to compensate for the addition of return water from the idle boiler. To prevent mixing cold water from an idle boiler with hot water boiler operating, you need to manually close the pipelines with valves or supply them with automation and servo drives.

Rice. 63. Heating scheme of two half-rings with increasing power by installing a second boiler

Connecting boilers according to the scheme of primary-secondary rings (Fig. 64) does not provide for such types of automation. When one of the boilers is turned off, the coolant passing through the primary ring simply does not notice the “loss of a fighter.” The hydraulic resistance in the connection section of the boiler A-B is extremely small, so there is no need for the coolant to flow into the boiler circuit and it calmly follows the primary ring as if valves in a switched-off boiler were closed, which in fact are not there. In general, in this scheme everything happens exactly the same as in the scheme for connecting secondary heating rings, with the only difference being that in this case it is not heat consumers who “sit” on the secondary rings, but generators. Practice shows that including more than four boilers in a heating system is not economically feasible.

rice. 64. Schematic diagram of connecting boilers to the heating system on primary-secondary rings

The Gidromontazh company has developed several standard schemes using HydroLogo hydrocollectors for heating systems with two or more boilers (Fig. 65–67).

rice. 65. Heating scheme with two primary rings with a common area. Suitable for boiler houses of any power with backup boilers, or for boiler houses of high power (over 80 kW) and a small number of consumers.

rice. 66. Double boiler heating circuit with two primary semirings. Convenient for large number consumers with high requirements for supply temperature. The total power of consumers of the “left” and “right” wings should not differ much. The power of the boiler pumps should be approximately the same.

rice. 67. Universal combined heating scheme with any number of boilers and any number of consumers (in the distribution group, conventional collectors or HydroLogo hydrocollectors are used, in secondary rings horizontal or vertical hydrocollectors (HydroLogo) are used)

Figure 67 shows a universal diagram for any number of boilers (but no more than four) and an almost unlimited number of consumers. In it, each of the boilers is connected to a distribution group consisting of two conventional collectors or “HydroLogo” collectors, installed in parallel and connected to a hot water supply boiler. On collectors, each ring from boiler to boiler has a common section. Small hydraulic collectors of the “element-Micro” type with miniature mixing units and circulation pumps. The entire heating circuit from boilers to “Element-Micro” hydrocollectors is the usual classical heating circuit, forming several (according to the number of hydrocollectors) primary rings. Secondary rings with heat consumers are connected to the primary rings. Each of the rings located at a higher stage uses the lower ring as its own boiler and expansion tank, that is, it takes heat from it and discharges waste water. This installation scheme is becoming a common way to install “advanced” boiler rooms and in small houses, and at large facilities with a large number heating circuits, allowing fine-tuning of each circuit.

To make it clearer what the universality of this scheme is, let's look at it in more detail. What is a regular collector? By and large, this is a group of tees assembled in one line. For example, in a heating circuit there is one boiler, and the circuit itself is aimed at priority cooking hot water. This means that hot water, leaving the boiler, goes straight to the boiler, giving up some of the heat to prepare hot water, and it returns to the boiler. Let's add another boiler to the circuit, which means that you need to install one tee each on the supply and return lines and connect the second boiler to them. What if there are four of these boilers? And everything is simple, you need to install three additional tees for the supply and return of the first boiler and connect three additional boilers to these tees, or not install tees in the circuit, but replace them with manifolds with four outlets. So it turned out that we connect all four boilers with the supply to one manifold, and the return to another. We connect the collectors themselves to the hot water boiler. The result was a heating ring with a common area on the collectors and boiler connection pipes. Now we can safely turn off or turn on some of the boilers, and the system will continue to function, only the coolant flow will change.

However, in our heating system it is necessary to provide not only heating domestic water, but also radiator heating systems and “warm floors”. Therefore, for each new heating circuit, you need to install a tee for the supply and return, and you need as many tees as we have planned for the heating circuits. Why do we need so many tees? Isn’t it better to replace them with collectors? But we already have two collectors in the system, so we’ll just expand them or immediately install collectors with enough taps so that they are enough to connect boilers and heating circuits. We find collectors with the right amount bends or we assemble them from ready-made parts or use ready-made hydraulic collectors. To further expand the system, if necessary, we can install collectors with a large number of outlets and temporarily plug them with ball valves or plugs. The result is a classic collector heating system, in which the supply ends with its own collector, the return with its own, and from each collector pipes go to separate heating systems. We close the collectors themselves with a boiler, which, depending on the speed at which the circulation pump is turned on, can have a hard or soft priority or not have one, since it turns out to be connected to the circuit in parallel with other heating circuits.

Now it's time to think about the heating system with primary-secondary rings. We close each pair of pipes leaving the supply and return collectors with an “element-Mini” type hydrocollector (or other hydrocollectors) and obtain primary heating rings. Through pumping and mixing units, we will connect heating rings to these hydrocollectors according to the primary-secondary scheme, those that we consider necessary (radiator, heated floors, convector) and in the quantity we need. Please note that in the event of failures in heat requests even for all secondary heating circuits, the system continues to operate because there is not one primary ring in it, but several - according to the number of hydrocollectors. In each primary ring, the coolant from the boiler(s) passes through the supply manifold, from it enters the hydraulic manifold and returns to the return manifold and to the boiler.

As it turns out, making a heating system with at least one boiler, at least with several and with any number of consumers is not so difficult, the main thing is to choose required power boiler(s) and choose the correct section of hydraulic collectors, but we have already talked about this in sufficient detail.

Two boilers in one house are the key to the reliability of your heating system. It is very good if the second boiler acts as an alternative, for example to gas. A gas boiler provides comfort (it does not require frequent maintenance), and a solid fuel boiler is installed to reduce heating costs and as a backup in case of an emergency. If certain conditions are met, they can be combined in one system. You can look at link an interesting video that shows two main ways to implement such a solution, or below is a brief summary and description of two ways to connect boilers into one system:

The first way The implementation of such a solution is the use of a hydraulic separator or hydraulic arrow in the boiler piping scheme. This simple device serves to equalize temperatures and pressure in the heating system and allows you to combine two or more boilers into one system and use them both separately and in cascade together.

One of the solutions for coordinating the work of two heating units and heating system circuits

Hydraulic arrow ( hydraulic separator) for connecting 2 boilers

Second option Coordination of the operation of two boilers can be used in low-power systems and, for example, with a double-circuit gas heating boiler. Everything is simple here: two boilers are connected in parallel to each other, the circuits are separated from one another by check valves, and the two boilers can operate in one combination either separately or simultaneously.

The classic heating scheme with one heat generator is well known to every home owner. However, by combining a gas and electric boiler in one system, a much greater practical effect can be achieved. They say that such a connection is much more economical than usual. Sounds tempting, doesn't it?

Logical reasoning raises doubts: how will electricity help save the budget, since its cost is much higher than gas? And why do this at all from the point of view of the feasibility of increasing the power of the units? Isn't it easier to just buy one productive boiler?

In fact, the project of such a combination is quite justified. We will tell you in detail how to assemble heating with electric and gas appliances. You will learn about the structure of this system and its feasibility. We’ll help you create a plan and not miss out. important nuances arrangement of a combined heating line.

The role of the leader in the gas + electric combination is usually performed by a gas unit. This is logical, if only because of the lower cost of the fuel used in the supply. But the word “save” was mentioned above, and it is not clear what the cost reduction is.

The fact is that in many regions the electricity tariff is based on the day/night system. In some cases, it turns out, at least a little, but more economical than paying for gas. The difference is doubtful, but it can serve as an additional reason to add arguments for the double connective.

Installing an electric boiler in conjunction with a gas boiler can play a backup or additional role in general organization heat supply. When choosing equipment power, you should focus specifically on the purpose of its use.

Of course, this is not such a compelling reason to immediately design a heating system with 2 boilers. The main advantages of the circuit are power amplification and uninterrupted operation. When choosing and installing a heat generator, you must clearly understand that any device and fuel supply are not eternal.

The power supply is turned off, the gas line may be blocked due to a leak, the voltage in the network will drop, or a simple breakdown of the unit itself will occur. In this case, you risk being left without heat and hot water during the cold season.

To ensure smooth operation heating equipment or increase the power of the system as a whole, you can allow 2 boilers operating on different fuels to operate at once

This is called connecting an additional (to enhance power) or backup power source, depending on the purposes and situations that arise.

Possibility of implementing joint connection

Designing a conventional gas-consuming heating system is not so easy. That is, create working diagram easy, but getting it approved is problematic. The situation is less dire in terms of costs, time and problems with obtaining papers approving the procedure.

And here is the combination of 2 different fuel units. It would seem that you won’t run into problems and will go through the authorities literally for years, for permits. But that's not true.

Restrictions on sharing There are no gas or electric boilers in the regulatory documents. However, it is still necessary to coordinate such a project with the gas service and obtain permission if your use of electricity exceeds the established limit in the total capacity of the equipment

In fact, building regulations are quite favorable to such schemes. To be more precise, there are no prohibitions.

Energy and fuel consumption meters are different. Resource consumption is not exceeded, an explosive situation is not provoked - install boilers in compliance with standard standards and installation instructions for each. There shouldn't be any problems.

We remind you that the installation of gas boilers should be carried out in accordance with SP 402.1325800.2018 (and this document is mandatory and not advisory).

How to connect 2 boilers in the system?

You can’t just randomly connect 2 devices, the system will either not work or will work incorrectly. It is necessary to use carefully designed and competently designed ones from an engineering point of view.

There are two main connection schemes, these are:

Sequential, when all elements are connected to each other without additional nodes. In this case, one device will heat the coolant, and the second will reheat it;
Parallel, in which the devices included in the circuit have 2 connection points and the boilers operate independently of each other.

The sequential system is more suitable for low-power boiler installations and is rarely used.

Serial connection is considered impractical if only because it is impossible to remove one boiler without affecting the second. In fact, the problem is solved by installing bypasses and shut-off valves, but still parallel connection is preferable

Meanwhile, parallel connection in a single system of gas and electric boilers has many advantages. Therefore, it is used most often, despite the fact that this arrangement requires more materials and is considered more expensive.

In such a device, you can turn off one of the devices at any time and even remove it for replacement or repair, while the second one will continue to operate as normal.

Features of parallel connection

Let's take a closer look at what a standard parallel connection diagram for gas and electric boilers looks like:

Each unit has coolant supply circuits. They join the common line.
It is imperative that there are safety groups and shut-off valves.
The return lines, also equipped with shut-off valves, are connected to the other line.
On the return line (or on the supply line), in front of the unit for combining the piping contours, it is installed.
The lines of both heating units are connected to.
It is installed on one of the distribution manifolds. A make-up circuit is also connected to its pipe, equipped with a check valve and shut-off valves.
From distribution collectors there are main branches to warm floor, radiators, boiler, each installed circulation pumps and valves for draining coolant from the system.

Is not circuit diagram, but only its main features. She in general outline gives an idea of how best to connect an additional electric boiler to the main gas boiler. The assembly option can be complicated and improved, for example, with an automation system and a servo drive.

With a parallel connection, you can also install a hydraulic arrow and an automation unit, but before doing this, carefully consider this decision; installing them is not always advisable

Manual/automatic control options

Control of the boiler backup system or shutdown of failed ones can be carried out manually or automatically. It is not advisable to leave the system running with one boiler turned off, since the water will continue to circulate.

Imagine what will happen when the cooled return flows in the opposite direction and begins to mix with the supply, cooling the coolant and causing the pump to work in vain.

If for some reason you do not want to equip the boilers with complex devices, you will start the unit yourself. That is, everything is standard: you need to turn on the device - turn all the necessary valves and turn it on. When disconnecting, perform the steps in reverse order.

If you want the backup equipment to start automatically, the system is equipped with automation, indoor and outdoor air temperature sensors, coolant temperature sensors, and servos.

However, despite the convenience, the system can cause certain problems, for example, hydraulic resistance check valves, causing strain on the pumps, contamination and wear of the devices themselves.

To automatically turn on the heating boiler, the system is equipped with a thermostat, which sends commands to the control unit, depending on the indicators temperature regime in the house. The switch-on time for night standby use is set on a timer. switched off using a magnetic starter.

Automation for electric boilers can be built-in, homemade, or purchased separately. However, you should not install it yourself using advice from the Internet, without having the proper skills. Invite a specialist for installation and correct system settings

When choosing a control that will be equipped with an electric boiler installed in parallel with a gas boiler, you should opt for automation if:

The backup boiler is turned on at night, when it is inconvenient to start it manually.
In case of long trips from home during the heating season.
If the gas boiler is unreliable.

In other cases, it is quite possible to use the simplest manual scheme.

Hydraulic arrow in a parallel connection system

A hydraulic arrow is a device that provides hydraulic isolation of flows supplied to individual circuits of the heating system. It plays the role of a buffer tank, receiving the flow of coolant heated by the boilers and distributing it to consumers in a branched system.

Often the volume of coolant required for them differs, the speed of movement of the heated water and its pressure differ. And in the situation under consideration, the movement of heated water from each of the boilers also stimulates its own circulation pump.

When the powerful pump is turned on, the coolant is unevenly distributed throughout the circuits. So, the task is to equalize this pressure. Due to the fact that there is virtually no hydraulic resistance inside it, it will freely receive and distribute coolant flows from both boilers.

Let’s figure out whether it is really necessary in a parallel system for connecting 2 boilers, especially since if you buy and install a hydraulic separator with the help of a specialist, and not with your own hands, the total amount will be unpleasantly surprising.

The device is a piece of pipe with pipes, hollow or with filter meshes to remove bubbles and filter out incoming contaminants. It can be placed in any position, but more often vertically, with an air vent on top and a shut-off valve on the bottom for cleaning. A hydraulic arrow is installed between the boiler and heating circuits

In the classic connection scheme, a hydraulic separator is usually not required, since the conflict of 2-3 pumps can be equalized without this device. Accordingly, if you have 2 boilers that are used exclusively as a backup and there are no more than 3-4 pumps in the system, there is no particular need for it.

But if there are more circuits or heating boilers operate simultaneously at full power, it is best to install this device. Again, it is unknown whether you will use the second boiler permanently or only in backup mode, so it is better to be safe.

Conclusions and useful video on the topic

Synchronization of operation and shutdown of boilers in a parallel installation:

Installing 2 heating boilers, gas and electric, is a wise solution to increase the power of heating equipment, as well as for backup heating of the building. Parallel installation of units is not as difficult as it might seem at first.

The main thing is to correctly select the arrangement scheme and correctly calculate the total or reserve power of the equipment. If you are not confident in your abilities and cannot cope on your own, it is best to contact plumbers. They will help you quickly and efficiently install a system for reliable and comfortable heating of your home.