Boiler room with two boilers. Scheme of connecting two boilers to one heating system. Parallel and serial connection of boilers

Modernization of the heating system in a private house may require the installation of two boilers at once, connecting them to a common network. What sequence should be followed in this case? How to connect two boilers to one system, which must be taken into account if there is a need to share a gas boiler with a solid fuel, electric boiler or heating equipment operating on liquid fuel.

How to connect two boilers together?

For what purposes may it be necessary to connect two boilers to one system? There are several compelling reasons to justify this.

1. Lack of power. Incorrect calculation of equipment or an additionally attached living area can lead to the fact that the boiler power may simply not be enough to maintain the normal temperature of the coolant.
2. Increased functionality. It may be necessary to connect two boilers to one system in order, for example, to increase the battery life of the equipment. For example, if the main source of heat is a solid fuel boiler, then for its operation it is necessary to constantly add firewood, which is not always convenient, and even more so practical.
   Installing after it an electric boiler or gas heater, this situation can be solved in the following way. As soon as the firewood or coal burns out and the coolant begins to cool down, additional heating equipment is switched on in the process and continues to heat the room until the owner brings a new batch of firewood in the morning.

As you can see, it is practical to connect two heating boilers using different types of fuel, in addition, it may be due to an urgent need associated with a lack of equipment performance.

How to connect two gas boilers in parallel

• Sequentially - in this case, one unit will be installed after another. In this case, the load will be distributed unevenly, since the main boiler will constantly operate at full capacity, which can lead to its rapid failure.
• Parallel. In this case, the heated area will be conditionally divided into two parts. Heating will be carried out immediately by two installed boilers. Parallel connection of two gas boilers is usually used in cottage houses and buildings with a large heated area.

For parallel connection, it is mandatory to install a controller and also develop a cascade control scheme. Only a competent specialist in each case can answer the question of how to connect two gas boilers.

How to connect two boilers - gas and solid fuel?

Models of gas and solid fuel equipment can be installed sequentially in one network. In this case, TT boilers will play the role of the main source of heat supply.

The principle of their work will be that gas equipment will be turned on for heating only if the operation of the main unit for some reason becomes impossible. Also, usually the task of heating water is assigned to a gas boiler, of course, if such a function is provided. When designing such a system, these features must be taken into account.

It will also be necessary to coordinate the selected scheme in the gas sector and get everything there necessary permissions, including specifications and connection project.

How to combine gas and liquid fuel boilers

• To carry out the installation of a general control system for the operation of water-heating equipment. Joint use of liquid fuel and gas boiler involves the installation of general automation. It, in turn, is connected to control sensors, which give a signal to turn on in the event of a shutdown of the main heat source.
• Install control valves. Shut-off valves operating in automatic mode can also be used.

Advantages of installing several boilers in one network

1. Ability to simultaneously control the operation of all equipment.
2. Savings due to the choice of the main type of fuel.
3. Possibility of longer operation of the equipment.

Practice shows that it is possible to simultaneously install two or more boilers in one network. With every additional element overall performance and efficiency drops significantly. Therefore, the expediency of simultaneous installation of four or more units of water heating equipment is completely absent.

By including two or more boilers in the heating circuit, one can pursue the goal of not only increasing the heating power, but also reducing energy consumption. As already mentioned, the heating system is initially designed to work in the coldest five-day period of the year, the rest of the time the boiler works at half strength. Suppose that the energy intensity of your heating system is 55 kW and you select a boiler of such power. The entire capacity 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 draft 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 capacity may be too much for the off-season. Therefore, instead of one 55 kW boiler, 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, everything turns on. If each of the boilers has two-stage burner, then the configuration of the boilers can be much more flexible: boilers can simultaneously operate in the system on different modes burner operation. And this directly affects the efficiency of the system.

In addition, installing several boilers instead of one solves several more problems. High-capacity boilers are heavy units that first need to be brought and brought into the room. The use of several small boilers greatly simplifies this task: a small boiler easily fits through doorways and is much lighter than a large one. If suddenly, during the operation of the system, one of the boilers fails (boilers are extremely reliable, but suddenly this happens), then it can be turned off from the system and quietly repaired, while the heating system will remain in operation. The remaining working boiler may not fully warm, but it will not freeze, in any case, it will not be necessary to “drain” the system.

The inclusion of several boilers in the heating system can be carried out according to a parallel scheme and according to the scheme of primary-secondary rings.

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 that it overcomes the hydraulic resistance in the boiler circuit and consumes electricity by the circulation pump. In addition, the return flow (cooled coolant) that has passed through the idle boiler is mixed with the supply (heated coolant) from the working boiler. This boiler has to increase the heating of the water in order to compensate for the mixing of the return from the idle boiler. To prevent mixing cold water from a non-working boiler hot water operating boiler, it is necessary to manually close the pipelines with valves or supply them with automation and servo drives.

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

Connection of 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 at the connection site 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 were closed in the disconnected boiler, which actually do not exist. In general, everything happens in this scheme in exactly the same way as in the scheme for connecting secondary heating rings with the only difference that in this case, not heat consumers, but generators “sit” on the secondary rings. Practice shows that the inclusion of more than four boilers in the heating system is not economically feasible.

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

Figure 67 shows a universal scheme for any number of boilers (but not 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 ordinary collectors or "HydroLogo" collectors, installed in parallel and closed to a hot water supply boiler. On the collectors, each ring from the boiler to the boiler has a common area. Small hydraulic collectors of the "element-Micro" type with miniature mixing units and circulation pumps are connected to the distribution group. The entire heating scheme from boilers to “element-Micro” hydrocollectors is a common classical heating scheme that forms several (according to the number of hydrocollectors) primary rings. Secondary rings with heat consumers are connected to the primary rings. Each of the higher rung rings uses the lower ring as its own cauldron and expansion tank, that is, it takes heat from it and discharges waste water. This installation scheme is becoming a common way to build "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 by and large, this is a group of tees assembled in one line. For example, in the 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 part of the heat to prepare hot water, it returns to the boiler. Let's add one more 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 do 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 a supply to one collector, and a return to another. We connect the collectors to the hot water boiler. It turned out a heating ring with a common area on the collectors and pipes for connecting the boiler. Now we can safely turn off or turn on part of the boilers, and the system will continue to function, only the coolant flow rate will change in it.

However, in our heating system, it is necessary to provide not only heating utility water, but also radiator systems heating and underfloor heating. Therefore, for each new heating circuit for supply and return, you need to install a tee and these tees need as many as we have planned 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 will simply build them up or immediately install collectors with such a number of taps that they are enough to connect the boilers and the heating circuits. Find collectors with the right amount bends or we assemble them from ready-made parts or use ready-made hydraulic collectors. For further expansion of the system, if necessary, we can install manifolds with a large number of outlets and temporarily plug them with ball valves or plugs. The result was a classic collector heating system, in which the supply ends with its own collector, the return - with its own, and from each collector pipes went to separate heating systems. We close the collectors themselves with a boiler, which, depending on the turn-on speed of the circulation pump, may have a hard or soft priority or not have one, since it turns out to be included in 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 coming out of the supply and return manifolds with an element-Mini hydrocollector (or other hydrocollectors) and get the heating primary rings. Through the pumping and mixing units, we will connect to these hydrocollectors, already according to the primary-secondary scheme, heating rings, those that we consider necessary (radiator, underfloor heating, convector) and in the quantity we need. Note that in case of failures in heat requests even for all secondary heating circuits, the system continues to work because it has not one primary ring, but several - according to the number of hydrocollectors. In each primary ring, the coolant from the boiler (boilers) passes through the supply manifold, from it enters the hydrocollector and returns to the return manifold and to the boiler.

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

The creation of a heating circuit in which two boilers in a heating system work either alone or together is associated with the desire to provide redundancy or reduce heating costs. The joint operation of boilers in an integrated system has a number of connection features that should be considered.

Possible options - two boilers in one heating system:

• gas and electricity;
• solid fuel and electricity;
• solid fuel and gas.

Combining a gas boiler with an electric boiler in one circuit, as a result of which a heating system with two boilers is created, can be implemented quite simply. Both serial and parallel connection is possible. In this case, a parallel connection is preferable, because. you can leave one boiler running and the other completely shut down, switched off or replaced. Such a system can be completely closed, and ethylene glycol can be used as a coolant for heating systems or.

Joint operation of a gas and solid fuel boiler

This is the most difficult option for technical implementation. In a solid fuel boiler, it is extremely difficult to control the heating of the coolant. Typically, these boilers operate in open systems, and overpressure in the circuit in case of overheating is compensated in the expansion vessel. Therefore, it is impossible to directly connect a solid fuel boiler to a closed circuit.

For the joint operation of a gas and solid fuel boiler, a multi-circuit heating system has been developed, which consists of two independent circuits.

The gas boiler circuit operates on radiators and on a common heat exchanger with a solid fuel boiler and with an open expansion tank. For a room in which both boilers are installed, it is necessary to fulfill the requirements for both gas and solid fuel boilers

Joint operation of solid fuel and electric boilers

For such a heating system, the principle of operation depends on the type. If it is intended for open heating systems, then it can easily be connected to an existing open circuit. If the electric boiler is intended only for closed systems, then the best option will be - teamwork to a common heat exchanger.

Dual fuel heating boilers

To increase the reliability of heating and to eliminate interruptions in the operation of the heating system, dual-fuel heating boilers operating on different types of fuel are used. Manufactured combined boilers only in the floor version due to the rather large weight of the unit. The universal unit can have one or two combustion chambers and one heat exchanger (boiler).

The most popular scheme is the use of gas and firewood to heat the coolant. It should be taken into account that solid fuel boilers can only work in open heating systems. To realize the benefits closed system an additional circuit for the heating system is sometimes installed in the universal boiler tank.

There are several types of dual-fuel combined boilers:

1. gas + liquid fuel;
2. gas + solid fuel;
3. solid fuel + electricity.

Solid fuel boiler and electricity

One of the most popular combined boilers is a solid fuel boiler with installed electric heater. This unit allows you to stabilize the temperature in the room. Thanks to the use of heating elements, such a combined boiler has acquired a lot of positive qualities. Consider how the heating system works in such a combination.

When igniting fuel in the boiler and when connecting the boiler to electrical network heating elements that heat the water immediately begin to work. As soon as solid fuel flares up, the coolant quickly heats up and reaches the temperature of the thermostat, which turns off the electric heaters.

The combi boiler runs on solid fuel only. After the fuel burns out, the water begins to cool in the heating circuit. As soon as its temperature reaches the thermostat threshold, it will turn on the heating elements again to heat the water. Such a cyclical process will maintain a uniform temperature in the rooms.

To optimize the heating circuits, heat accumulators in heating systems were invented, which are a large volume tank from 1.5 to 2.0 m3. During the operation of the boiler, a large volume of water is heated from the pipes of the circuit passing through the accumulator tank, and after the boiler stops working, the heated water slowly releases heat energy to the heating system.

Heat accumulators allow you to maintain comfortable temperature quite a long time.

To in winter time to avoid critical situations, reduce heating costs and ensure its reliability, many owners prefer either installing a system with two boilers using different fuels, or installing. These heating options have certain advantages and disadvantages, but they fully provide their main task - stable and comfortable heating.

Let's start with what modern house located with middle lane, should be 2 boilers. Not even necessarily 2 boilers, but two independent sources of thermal energy - that's for sure.

We already wrote about what boilers or energy sources these could be in the article "". It describes in more than detail which boiler, which understudy is needed and can be selected.

Today we will consider how to connect 2 or more heat generators to 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, such as two gas boilers. And also there can be more than 1 backup boiler, for example, on different types of fuel.

Connection of 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, heating the house, operate on the same fuel.

These are, usually, which are connected in a cascade in order to heat rooms from 500 sq.m. total area. Rarely enough they are connected together for basic heating or solid fuel boilers.

We are talking about the main heat generators, and about the heating of residential premises. For cascade and modular boiler houses for heating large industrial premises may include "batteries" of coal-fired or oil-fired boilers in an amount of up to one dozen.

So, as mentioned above, they are connected to a cascade when a second identical boiler or a slightly lower power complements the first heat generator.

Usually, in the off-season and slight frosts, the first boiler in the cascade operates. In frosts or if it is necessary to quickly warm up the premises, a second boiler in the cascade is connected to it to help.

In the cascade, the main boilers are connected in series so that they are heated by the first heat generator. At the same time, of course, in this bundle it is possible to isolate each boiler and bypass, which allows you to let water bypass the isolated boiler.

In the event of a malfunction, any of the heat generators can be turned off and repaired, while the second boiler will properly heat the 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.

And also allows each of the boilers to work at its full capacity if necessary. While 1 high-power boiler would only work at half power and increased clocking.

Parallel connection of boilers - pros and cons

We have considered the main boilers above. Now consider the connection of 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 reserve boilers are as follows:

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

Cons of parallel connection of backup boilers:

• We'll have to work more with the piping of boilers, more soldering polypropylene pipes, more welding steel pipes.
• As a result, more materials, pipes and fittings, and valves will be used.
• The boilers will not be able to work together, in unified system, without use additional equipment- hydraulic arrows.
• Even after using the hydraulic arrow, there remains the need for complex adjustment and coordination of such a system of boilers 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 reserve heat generator, and to the connection of two or more reserve heat generators on any type of fuel.

Serial connection of boilers - pros and cons

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

In this case, the first thing to do is to put the boiler on the cheapest type of fuel for you. It can be a wood, coal or waste oil boiler. And behind it, any backup boiler can stand in a cascade - even a diesel one, even a pellet one.

The main advantages of parallel connection of boilers:

• In the case of working 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 backup boiler can be turned on to heat water in the heating system in the coldest days.

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

• Longer water path through the system with more twists and turns in connections and fittings.

Naturally, it is impossible to directly let the flow from one boiler into the input 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 just be the most effective. It can be implemented by installing bypass loops for each boiler.

Parallel and serial connection of boilers - reviews

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

Anton Krivozvantsev, Khabarovsk Territory: I have it, it is the main one and heats the entire heating system. I am satisfied with Rusnit, a normal boiler, 1 heating element burned out in 4 years of operation, I changed it myself, everything was there for 30 minutes with a smoke break.

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

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

There is one more review, now about the parallel connection of 2 boilers in the boiler room:

Evgeny Skomorokhov, Moscow: My main boiler is , which works mainly on wood. My backup boiler is the most common DON, which is included in the system with the first one in parallel. It rarely fires up, and indeed, I inherited it along with the house I bought.

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

When the insulation is completed to the end, I think I will not melt the old DON boiler at all, but I will leave it as a backup.

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

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Serial connection of boilers more economically feasible- in this case, an expansion tank and a safety group built into the gas boiler are used. At the same time, there are fewer difficulties with connection and a smaller number of components, materials and valves are needed, which, on average, cheapens total material cost for 40$ ~ 80$.

This option is justified when connecting an electrode boiler (hereinafter EC) paired with a solid fuel boiler (hereinafter TTK) or a gas boiler (hereinafter GK) - boilers with a small displacement ( up to 50 liters) in order to save the material part of the components. The boiler can be connected sequentially both before and after the gas boiler - it all depends on the physical possibility of the tie-in. It is recommended to embed the boiler in such a way that circulation pump was on the "return" of both one and the second boiler. That is, if a circulation pump is used, which is built into the GC, then it is more logical to organize an EC tie-in in front of the GC (i.e., at the GC supply).

However, still key point when connecting a boiler to an existing one - is what must be implemented general connection GK and EK systems to the safety group and expansion tank.

Parallel connection

Parallel connection most often used for connection to GK or TTK (solid fuel boiler) with large capacity, i.e.
more than 50 liters. This is done in order to cut off (not spend additional energy on heating) the unused volume of coolant in the main or TTC.

Usually, such systems are more expensive. due to the need to install additional equipment on the electric boiler circuit, i.e. additional safety group, expansion tank and shut-off valves.

Parallel system can operate in manual and automatic mode(as opposed to serial, where the principle of connection makes it possible at the lowest cost to implement only automatic or semi-automatic automatic operation EC paired with TTK or GK)

In order for the parallel system to function in manual mode, shut-off valves (ball valves) must be installed in the necessary places or a By-Pass system is embedded, which generally leads to an increase in the cost of such a connection by $40-80.

If you organize automatic operation with parallel connection of the TTC (GK) and EC, you need to insert a three-way zone valve, a servo drive and an additional thermostat, from which a command will be sent to subsequently switch the heating circuit of the TTK (GK) to the heating circuit of the EC. The use of such a system as a whole will increase the cost of materials for connection by approximately $80 - $120. I repeat, such a connection scheme is highly desirable and economically justified in the future in the case when the volume of the HA or TTK, together with the total volume of the heating system, significantly exceeds the recommended proportion - the ratio of the total volume of the system coolant per 1 kW of boiler power.

This ratio varies on average (20~40) L / 1 kW

SUMMARY

Each connection scheme, whether parallel or serial, has the right to exist.

Question- so how to effectively and competently organize the linking of boilers to work in pairs in parallel or in series!?

Answer- in each individual case, it will be advisable to have its own connection method. And the main factors that will influence the choice of the type of boiler connection are:

1. The ratio of thermal, energy parameters: (20~40) L /1 kW(the ratio of the total volume of the system coolant per 1 kW of boiler power);
2. physical capability implementation of one or another project;
3. Financial opportunities implement option 1 or 2.