The two-boiler scheme is very widely used in recent times, and there is a lot of interest. When two thermal units appear in one boiler room, the question immediately arises of how to coordinate their work with each other. Let's try to answer the question of connecting two boilers to one heating system.
This information will be of interest to those who are going to build their own boiler house, who want to avoid mistakes and for those who are not going to build with their own hands, but want to convey their needs to those people who will assemble the boiler house. It is no secret that each installer has his own ideas about how the boiler room should look and often they do not coincide with the needs of the customer, but the customer's desire is more important in this situation.
Let us analyze examples of why in one case the boiler house works in automatic mode(boilers are coordinated with each other without the participation of the consumer), and in another it is required that it be turned on.
Nothing is required here, except for shut-off valves. Switching between boilers is carried out by manual opening / closing of two taps located on the coolant. And not four, in order to completely cut off the idle boiler from the system. In both boilers, most often there are built-in ones and it is more profitable to use them both at the same time, because the volume of the heating system very often exceeds the capabilities of one expansion tank taken separately. In order to avoid the useless installation of an additional (external) expansion tank, it is not necessary to cut off the boilers from the system completely. It is necessary to shut them off according to the movement of the coolant and leave them simultaneously included in the expansion system.
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 automatic system simultaneous operation of two boilers will be required additional detail is a thermostat that will turn off circulation pump if the system has a wood burning boiler or any other boiler with manual loading. It is necessary to turn off the pump at the boiler. Because when the fuel burns out in it, it makes no sense to drive the coolant through this boiler for nothing, interfering with the operation of the second boiler. Which will pick up the work when the first one stops. At maximum diameter and the highest brand of thermostat to turn off the pump, you will spend no more than 4000 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
Consider the following five options with different units in conjunction with an electric boiler, which is in reserve and must turn on at the right time:
- Gas + Electric
- Firewood + Electric
- LPG + 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 activation is also acceptable.
The pellet boiler may stop due to the fact that it has run out of fuel pellets. It got dirty and wasn't cleaned. The electric must be ready to turn on instead of the stopped boiler. This is only possible with automatic connection. Manual connection in this option only suitable if you permanently live in a house where such a heating system is installed.
Boilers for diesel 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 work as an emergency in case the boilers fail for some reason. Not just stopped, but broken and in need of repair. It is also possible to switch on automatically as a function of the time. The electric boiler can work in pairs with liquefied gas and a solar boiler at a nightly rate. Due to the fact that the night rate is cheaper for 1 kW / hour than 1 liter of diesel fuel.
Combination of electric boiler and wood burning
This combination of connecting two boilers is more suitable for automatic connection and less for manual connection. The wood burning boiler is used as the main one. It heats the room during the day, and the electric turns on to heat it up at night. Or in the case of a long stay in the house - an electric boiler maintains the temperature so as not to freeze the house. Manual 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 with a wood-fired boiler.
Combination of gas and electric boilers
In this combination of connecting two boilers, the electric boiler can act both as a backup and as a main one. In this situation, a manual connection scheme is more suitable than an automatic one. Gas boiler tested and reliable unit, which the for a long time can work without damage. In parallel, it is not advisable to connect an electric boiler to the system for safety net in automatic mode. Upon failure gas boiler– You can always turn on the second unit manually.
A feature of solid fuel boilers is the need to load firewood to maintain heat in heating appliances, this requires constant attention from the residents. The solution to the problem in such a situation can be called connecting a heat accumulator, installing an additional boiler in the heating system, or using two boilers at the same time: solid fuel and gas.
In this case, heat is supplied to the batteries if the firewood in the firebox has already run out, but there is gas in the cylinder. As alternative you can install a wood-gas unit, which does not require special costs and efforts to installation work. But practical application has shown that connecting two boilers to one system is much more efficient and profitable. When connecting a gas and solid fuel boiler at the same time, the system is in the mode permanent job even if one of the devices fails. The breakdown of the boiler, which runs on gas and wood, leads to a shutdown of the entire system and it becomes cold in the rooms.
What is the difficulty of connecting two boilers
The main difficulty in using two boilers in one heating system is the need to equip different types strapping. Two gas boilers in one house can only be installed with a closed heating system. That is, connecting a gas boiler to the heating system will not cause problems. And for solid fuel units you need open system. The fact is that the second version of the boiler is capable of heating water to a very high temperature, which leads to an increase in pressure in the system. Even with weak combustion of coals, the coolant continues to heat up.
In such a situation, pressure relief in the heating network is required, for which they cut into the circuit expansion tank open type. If the volume of this element of the system is insufficient, a separate pipe can be brought into the sewer to drain excess coolant. However, the installation of such a tank can cause air to enter the coolant, which can damage the internal elements of the gas boiler, pipes and heating devices.
To avoid all these difficulties of connecting two boilers to one heating system at the same time, you can use two options:
- Use a heat accumulator - a device that allows you to combine a closed and open heating system.
- Organize a closed heating circuit for a solid fuel and pellet boiler using a special security group. In this case, the units can work autonomously and in parallel.
Arrangement of a heating system with a heat accumulator
The use of such an element in a scheme with two boilers in one heating system has several features, depending on the installed units:
- The heat accumulator, gas boiler and heating devices form a single closed system.
- Solid fuel boilers running on wood, pellets or coal heat water, thermal energy transferred to the heat storage. It, in turn, heats the coolant circulating in a closed heating circuit.
For self-creation heating schemes with two boilers, you must purchase the following:
- Boiler.
- Heat accumulator.
- Expansion tank of the appropriate volume.
- hose for additional outlet coolant.
- Shut-off valves in the amount of 13 pieces.
- pump for forced circulation coolant in the amount of 2 pieces.
- Three-way valve.
- Water filter.
- Steel or polypropylene pipes.
Such a scheme is characterized by operation in several modes:
- Transfer of thermal energy from a solid fuel boiler by means of a heat accumulator.
- Water heating solid fuel boiler without using this device.
- Receiving heat from a gas boiler connected to a gas cylinder.
- Connecting two boilers at the same time.
Assembly of an open type system with a heat accumulator
The organization of this type of heating system is carried out according to the following scheme:
- Shut-off valves are installed on two fittings of a solid fuel boiler.
- Connect the expansion tank. At the same time, its location should be located on the very high level relative to other elements of the heating circuit.
- Taps are also installed on the pipes of the heat accumulator.
- Connect the boiler and the heat accumulator through two pipes.
- Two tubes are cut into the circuit between the heat accumulator and the boiler, stepping back a short distance from the taps. Shut-off valves are also installed on these tubes. Additional tubes will allow heating the coolant from a solid fuel boiler without using a heat accumulator.
- Next, a jumper is cut in to connect the supply and return pipes in the gap between the heat accumulator and the boiler. Welding or fittings can be used to fasten the jumper to the supply; the jumper is fixed on the return pipe by means of a three-way valve. In the formed small circle, the coolant circulates until its temperature reaches 60 degrees. With stronger heating, the water begins to move in a large circle, capturing the heat accumulator.
- Connect a water filter and a circulation pump. Both devices must be installed on the return pipe of the heating circuit, the best place the gap between the boiler and the three-way valve is considered. Here they have a tap with a pump and a filter. It should be remembered that cranes are necessarily mounted before and after these elements. The advantage of a U-shaped outlet is the ability to install a bypass, it will carry out the movement of the coolant in the absence of electricity. Naturally, a gas boiler room in a private house should have enough space to accommodate all the necessary equipment.
Closed system with heat accumulator
closed system heating does not require the installation of an expansion tank, therefore assembly process is greatly simplified. Most often, gas boilers are equipped with an expansion tank and safety valve.
For correct assembly such a heating circuit, you must follow certain instructions:
- A tap and a pipe going to the heating appliances are connected to the supply fitting of the gas boiler.
- A pump for forced circulation of the coolant is installed on this pipe. It should be placed in front of the radiators.
- Each radiator is connected in series.
- A pipe leading to the heating boiler is diverted from them. At the end of the pipe at a short distance from the unit, powered by a gas cylinder, a shut-off valve is installed.
- Pipes leading to the heat accumulator are connected to the supply and return pipes. One of the tubes is connected in front of the pump, the second tube is connected behind the heating devices. Each tube is equipped with a tap, and tubes should also be connected here, which were previously embedded in front of and after the heat accumulator.
Installation of a closed system with two boilers - gas and solid fuel
When arranging such a heating system, a solid fuel and gas boiler in one circuit are connected in parallel with obligatory installation security groups. The open expansion tank is replaced by a closed membrane tank, which is located in a special room.
The security group contains the following elements:
- Valve to remove accumulated air.
- Safety valve, with which you can reduce the pressure in the system.
- Pressure gauge.
The question of how to connect two boilers, gas and solid, is solved in the following order:
- On the pipes coming from the heat exchangers of the gas and solid fuel boilers in the same system, shut-off valves are installed.
- A safety group is located on the supply pipe coming from the solid fuel unit. However, it can be placed near the valve.
- The supply pipes of both boilers are connected. Previously, a jumper cuts into the line coming from the solid fuel boiler, along which the movement of the coolant in a small circle will be organized. The distance from the boiler to the tie-in point can be up to 2 meters. A reed valve is installed next to the jumper. When the wood-fired boiler is turned off, such a scheme does not allow the coolant to enter the boiler, despite the strong pressure that the gas boiler creates.
- Perform the connection of the supply line with heating appliances, which are located in different rooms and at different distances from each other.
- Between boilers and heaters, a return line is installed. In a certain place, it is divided into two pipes: one is directed to a gas boiler, the other to a solid fuel unit. In front of a device powered by a gas cylinder, install spring valve. A jumper and a three-way valve are connected to another pipe.
- A membrane expansion tank and a pump for forced circulation of the coolant are mounted on the site before the separation of the return line.
The scheme for connecting two boilers to one system may well be used when installing a universal combined heating boiler.
Two boilers for a hydraulic gun can be connected through a polypropylene tee. Simple, logical and relatively reliable. It all depends on your skill, patience and ingenuity. About whether this is justified from a security point of view, where to place something, read and see in our article.
Is it possible or not?
How to connect two boilers to the hydraulic gun, both specialists and ordinary buyers understand. Our managers hear this question quite often. Recently, the activity of customers has intensified, so there was a topic for the article.
First, let's find out whether it is possible to display the hydraulic arrow on two boilers at once. Experts interviewed say yes. Examples from practice are given to support this.
Boiler house on the basis of 2 gas boilers with a hydraulic arrow
There are several reasons to buy and install another boiler
Lack of main power
When equipping the system, the master or you, if you designed the boiler room with your own hands, made a mistake
You decide to expand your living space and build another floor
In addition, an additional boiler is brought to the hydraulic arrow in order to save money. The maximum power of the boiler is taken, with the expectation of the coldest season.
In full force heating equipment works five days a year, this is how long frosts last on average in central Russia
In spring, summer and autumn, the system needs much less power. That is why one 55 kW boiler is often replaced with two 25 or 30 kilowatt ones. It is not only economical, but also practical. You can turn on one boiler. When all the power is needed, start both.
The reserve boiler is an excellent insurer
For example, solid fuels are often supplemented with electric ones. As soon as the coolant cools down, the electric boiler is quickly wedged into the system. Helps, especially at night. You do not have to get up, go down to the boiler room and load a new “portion” of fuel into the furnace.
Installation steps
Our client from Sochi connected the hydraulic switch in the balancing manifold with two boilers at once. The main one is gas, the backup one is electric.
The outlet to the boiler in the BM-100-4D design complies with the DN 32 standard, that is, 1 1/4 inches. The thread is standard, suitable for the main types of pipes.
Polypropylene tees are placed on the return and supply. The three-part design was not chosen by chance. In the installation of pipes, tees are placed to enter additional communication. In the case of a hydraulic gun, the retraction principle also applies.
Advantages
Safely. Both boilers work correctly with optimal output
functional. The coolant enters in full and at the desired temperature (it will not lose a single degree).
practical. Two boilers in the heating system significantly reduce maintenance costs. The amount on the electricity bill is a pleasant surprise.
By the way, the strapping uses three-way valves Esby, also with polypropylene tees. Unusual design solution makes the boiler room even more efficient. Mixing of hot and cold streams occurs strictly in accordance with the norms of the throughput of consumers.
There is also a boiler in the harness indirect heating 200 liters, circulating Grundfos pumps 25/6, automatic floor heating. All of the above is connected in the balancing manifold Gidruss BM-100-4D
Three contours are directed downwards, one to the side. center distance between nozzles 125 millimeters allows you to install pumping modular groups of both domestic and foreign brands
balancing manifold made of structural low-alloy steel. This is the second brand after stainless steel, inferior to the "girlfriend" only in rust resistance. Signs of oxidation will appear after three to four years. To delay this unpleasant moment, all BM series collectors are painted polymer paint. The composition has a light consistency, applied with a sprayer. Only 4 layers. The finish dries completely within a day. The product is then checked and prepared for shipment.
Learn more about the benefits of carbon steel manifolds at
Conclusions briefly
A hydraulic gun with two boilers is a reality.
Polypropylene tees can be used as wiring.
Several heating devices evenly distribute the load throughout the system, which significantly reduces the cost of diagnostics and maintenance.
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 costs by material 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 the circulation pump is 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 inserting a boiler into an existing one, it is that a common connection of the GK and EK systems to the safety group and expansion tank must be implemented.
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 installation additional equipment to the electric boiler circuit, i.e. additional group safety, expansion tank and shutoff valves.
Parallel system can operate in manual and automatic mode(unlike serial, where the principle of connection makes it possible to least cost implement only automatic or semi automatic operation EC paired with TTK or GK)
In order for the parallel system to function in manual mode, they must be installed in the required places. shut-off valves(ball valves) or the 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:
- 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);
- physical capability implementation of one or another project;
- Financial opportunities implement option 1 or 2.
Ecology of knowledge. Homestead: The most rational heating system is one in which the coolant becomes hot due to the operation of two or three boilers.
A home heating system based on two boilers is a fairly common solution that saves a lot of money. Usually one of the boilers - the main one - is a gas boiler, easy to operate, but running on expensive fuel. The second is a solid fuel boiler, less convenient, requires constant monitoring and periodic fuel supply, but more economical ( solid fuel- coal, wood - much cheaper than gas).
When using two boilers, it is rational to combine them into one system and, if necessary, turn on or off the additional boiler. But the work of these heating appliances has a number of differences that need to be considered when planning their connection scheme.
Adjustment of excess pressure in the heating system
The operation of a solid fuel boiler is associated with such a phenomenon as a significant increase in pressure in the system due to an increase in temperature, which is difficult to control. To protect the system in such cases, an open expansion tank is used, connected to the atmosphere, which allows the coolant (water) to expand without increasing the pressure in the pipes. At a temperature exceeding the norm, the excess of heated water simply flows through the hole in the tank into the sewer.
An open expansion tank is the main difference between a solid fuel boiler and a gas boiler. The latter is equipped with automation that controls the temperature and pressure in the system, preventing the coolant from overheating. The advantage of such a closed self-regulating system is that a minimum of oxygen from outside enters it, reducing the risk of corrosion. metal parts. But even such a system has a certain overpressure, which is regulated by a safety valve and expansion tank, only they are mounted in the boiler body itself, and not separately, like in solid fuel boilers.
How to make heating with two boilers
So, there are two boilers that differ side by side design features. How can you combine them in one system? The most effective is the option of dividing the system into two independent circuits using a heat exchanger. One of the circuits is open, equipped with a solid fuel boiler; the second - a gas boiler and radiators. Both circuits are loaded on one heat exchanger.
When planning such a system, it is necessary to take into account the position of all the main and connecting elements, so that during operation, maintenance or repair they can be easily found, inspected, and replaced if necessary. Therefore, before starting the installation, it is better to draw a diagram, put equipment on it, outline the laying of pipes, and mark the places for installing additional elements.
Requirements for premises with a solid fuel boiler
To the premises in which the boilers are installed, normative documents a number of requirements are put forward depending on the type of boilers. Solid fuel boilers with a power of 30 kW or more can only be installed in rooms specially equipped for them. The boiler room should be centrally located relative to the rooms that are heated, on the same level with them or in the basement, which will allow the generated heat to be used with maximum efficiency, and a minimum of energy will be spent on maintaining circulation. Fuel cannot be stored directly in the boiler room, it is usually stored in an adjacent room. An exception is when boilers of small power up to 30 kW are used, then the fuel supply can also be kept in the boiler room itself in boxes at a distance of at least 1 m from the boiler. Since solid fuel, unlike gas, has to be harvested independently, it is advisable to do this once for the entire heating season, and for this it is necessary to have enough space for its storage, which must be taken into account when choosing a room.
The boiler must not be installed on the floor, but on a foundation or foundation made of non-combustible materials. The surface of the base or foundation must be strictly horizontal and extend beyond the boiler by 0.1 m on the sides and rear and by 0.3 m in front. For boilers with a power of up to 30 kW, the floor can be made of combustible materials, such as wood, but then a steel sheet 0.7 mm thick must be attached around them, which extends beyond the boilers by 0.6 m on all sides. Under the boilers, the floor, foundation or base must be non-combustible.
The walls, partitions and ceilings of the boiler room must have a fire resistance limit of at least 0.75 hours. When the boiler room is located above the living quarters, its floor, the places where pipes pass through holes in the floor, door sills, as well as walls at a height of 10 cm must be protected waterproofing material. A prerequisite for choosing a room for a boiler room is the presence of sufficient natural lighting (at least 0.03 m2 per 1 m3). The height of the boiler room should not be less than 2.5 m. The area of the boiler room should provide access to all elements of the system for the purpose of their inspection or repair. Minimum distances between the boiler and walls (partitions) should be 1 m from the front side and 0.6 m from all the others. The minimum volume of the boiler room depends on the power of the boiler used: for a boiler with a power of up to 30 kW - 7.5 m3, a power of 30 to 60 kW - 13.5 m3, a power of 60 to 200 kW - 15 m3.
Ventilation of the boiler room
For normal operation of the boiler, the boiler room must have a ventilation system, not only exhaust, but also supply. An opening with an area of 200 mm2 or more is used as an intake duct, and a ventilation duct with a cross section of 14x14 cm is used as an exhaust duct, the entrance of which is located under the ceiling (for boilers with a power of up to 30 kW). The area of the inlet of the hood should be the same as the section of the ventilation duct. The hole itself is usually closed with a grate. Both the supply and exhaust ducts should not have any dampers - they should always be open and preferably clean. When using more powerful boilers (from 30 kW and above) ventilation holes must have a cross section of at least 20x20 cm and not less than half the cross section of the chimney.
The opening of the supply channel is best made behind the boiler, its height above the floor level should not be less than 1 m. An air duct of the same cross section can also be used as a supply channel. When using an air duct, a damper is allowed to regulate the air flow, but it should not block the channel by more than 80%.
All ventilation ducts are made of non-combustible materials. You can not install a forced system exhaust ventilation if the chimney is with natural draft.
Sewerage
To drain excess water when it overheats, the boiler room must be equipped with a sewerage system connected to the sewerage of the house by a floor drain. If for some reason this cannot be done, a well with a hand pump is equipped in the boiler room. When overheated, water will accumulate in it, and pumped out with the help of a pump. To supply water to the boiler, the system is equipped with an intake valve, in front of which it is usually mounted also check valve. The boiler is connected to the cold water system with a flexible hose.
Requirements for rooms with gas boilers
Now consider the requirements that are put forward for rooms with gas boilers. gas boilers, whose power does not exceed 30 kW, can be installed on any of the floors in almost all rooms, except for those in which people are constantly (bedrooms, living rooms, children's rooms, as well as garages and landings if the boilers are equipped open cam combustion). Using liquefied gases there are more restrictions, for example, they cannot be installed in basement or basements. Boilers with a power exceeding 30 kW are installed in separate rooms with a ceiling height of at least 2.5 m. The volume of the room for gas boilers with a power of up to 30 kW must be at least 7.5 m and gas stove for 4 burners, the minimum volume of such a kitchen is 15 m3.
Ventilation of a room with a gas boiler
To ensure air supply to the room with a gas boiler, an inlet with a cross section of at least 200 cm2 is used, located at a height of no more than 30 cm from the floor. Air can come from outside or from adjacent rooms.
In boiler rooms where liquefied gas boilers are installed, the exhaust opening must be at the bottom at floor level, and the exhaust duct must slope outwards. This is due to the fact that liquefied gas heavier than air, and if it leaks, it will sink down. air inlet should also be at floor level and have a cross section of 200 cm2.
Structural materials and heating systems
The floor under the gas boiler must be made of non-combustible materials or covered with steel sheet or other non-combustible material, going beyond the boiler by 0.5 m. The same applies to walls if the boiler is attached to them.
Gas pipelines are made of steel seamless pipes or straight-seam electric-welded pipes. It is also possible to use copper pipes, the wall thickness of which is not less than 1 mm, indoors.
In a heating system for heat carriers, copper or plastic pipes are usually used. Using plastic pipes in places where the temperature is high enough, for example, near the boiler, their sections should be replaced with pipes made of copper or steel. Copper pipes are sensitive to mechanical damage, therefore, when using them, it is necessary to install filters that do not allow small particles to enter the system. Inside the copper pipes, their walls are covered protective layer copper oxide, and solid particles can damage it.
When installing copper pipes, their edges must be carefully sanded so that there are no sharp edges, and wrapped inward. Rough edges can cause system flow turbulence, noise, bacteria build-up and damage to the pipe lining. Copper pipes must be correctly selected in diameter - too thin pipes with high water pressure can quickly fail due to a protective layer damaged by strong pressure. In addition, thin pipes increase the load on the pump and impair the operation of the boiler burner. And one more nuance concerning copper pipes. When using pipes with a diameter of less than 28 mm, it is undesirable to connect them by soldering, since heat affects their structure, significantly reducing the strength and resistance to oxygen.
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