How to properly connect two heating boilers

Wiring diagrams solid fuel boiler heat accumulator and reserve boiler

The question of combining heating system (the ability to heat the building with different fuels) is of interest to all owners of private buildings. As a rule, the problem is solved in two ways. by purchasing a universal boiler, the fuel for which is wood (coal) electricity, or 2 units (solid fuel and electric), which are included in a common circuit. According to experts, the latter option, although it will cost a little more, is the best.

This heating system generates heat by burning solid fuel (wood, coal, to, pellets ). It has its own features that directly affect its efficiency and safety:

• Inertia. The solid fuel boiler cannot be stopped immediately. After stopping the oxygen supply, the system continues to work until the oxygen inside the furnace runs out, or until the fuel burns out. This can lead to overheating of the coolant, the formation of large amounts of steam. As a consequence. the destruction of the boiler body or parts of the heating system.
• Condensate. Appears when the boiler is connected directly, the coolant passes through the boiler tank at a low temperature. Causes corrosion of the steel walls of the fuel tank. As it mixes with the ash, it turns into a sticky mass that is difficult to clean off.

Boiler gas and solid fuel in one: the connection of two boilers in one heating system, the scheme with two boilers, how to connect an additional boiler

In order to avoid these problems, the boiler must be piped properly, and a safety group must be included. Let’s take a closer look at what you need the strapping of a solid fuel heating boiler, the main schemes of installation.

What are double circuit gas boilers and how do they differ from single circuit boilers?

The principle of operation of the device is as follows: there are two circuits, and they work independently of each other.

One ensures the smooth flow and proper operation of the coolant in the heating system, the second. in the hot water system.

Heat exchangers (main and additional) allow to perform two tasks: to heat the coolant running through the heating system and water for DHW. A single-circuit boiler cannot boast of such features. It is equipped with a single heat exchanger, so it is used only for supplying the house with heat.

Connection of two or more main heat generators

Let’s first consider the scheme, in which we have two or more heat generators, which are the main and heat the house, using the same fuel.

These are usually main gas boilers, which are connected to the cascade in order to heat premises with the area over 500 sq.m., which are usually heated by the second boiler.м. of the total area. It is rather rare to connect together for the main heating diesel or solid fuel boilers.

This concerns the main heat generators, and the heating of the living quarters. For cascade and modular boilers for heating large industrial premises can include “batteries” of coal or fuel oil boilers up to one dozen.

So, as mentioned above, the main boilers are connected in Cascade, when the second boiler of identical or slightly lower capacity complements the first heat generator.

Usually the first boiler in the cascade works during low frosts and low seasons. In case of frost or in the event of the need for rapid heating of the rooms, the second boiler in the cascade is connected to assist.

In the cascade, the main boilers are connected in series, so that the second boiler heats the water heated by the first heater. In this connection, of course, it is possible to isolate each boiler and bypass the isolated boiler.

In the case of a malfunction, either of the heat generators can be shut down and repaired, while the second boiler will properly heat water in the heating system.

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

And also allows each of the boilers to work at its full capacity if necessary. Whereas 1 boiler of high capacity would only work at half capacity with low efficiency and increased clocking.

Parallel connection of boilers. pros and cons

The basic boilers we have considered above. Now let’s consider the connection of backup boilers, which must be in the system of any modern house.

If the reserve boilers are connected in parallel, this option has its advantages and disadvantages.

The pros of connecting backup boilers in parallel are as follows:

• Each boiler can be independently connected and disconnected from the heating system.
• It is possible to replace each heat generator with any other equipment. It is possible to experiment with the settings of the boilers.

Disadvantages of parallel connection of reserve boilers:

• You will have to work more with boiler piping, more soldering of polypropylene pipes, more welding of steel pipes.
• As a result, you will need more materials, pipes and fittings, and valves.
• The boilers will not be able to work together in a single system, without additional equipment. the hydro.
• Even after the use of hydrostrek, the need for complex adjustment and harmonization of such a system of boilers on the temperature of water supply into the system, and water supply from the return flow to the boilers remains.

The above advantages and disadvantages of parallel connection can be applied to the connection of the main and backup heat generator, as well as to the connection of two or more backup heat generators on any type of fuel.

Peculiarities of primary and secondary rings scheme

Such a scheme provides the organization of the primary ring, through which the coolant must constantly circulate. Heating boilers and heating circuits are connected to this ring. Each circuit and each boiler is a secondary ring.

Another feature of this scheme is the presence of a circulation pump in each ring. The operation of the individual pump creates a certain pressure in the ring in which it is installed. The assembly also has a certain effect on the pressure in the primary ring. So, when it is turned on, water comes out of the water supply pipe, entering the primary circuit and changing the water resistance in it. As a result, there is a kind of barrier to the coolant flow.

Since first the return pipe is connected to the circle, and after it. the supply pipe, the coolant, having received a considerable resistance at the supply pipe, begins to flow into the return pipe. If the pump is turned off, the water resistance in the primary ring becomes very small and the coolant can not swim into the boiler heat exchanger. The piping continues to work as if the unit had not been shut down at all.

For this reason it is not necessary to use one complicated automation for shutting down the boiler. The only thing to do is to install a check valve between the pump and the water return pipe. The same situation is with the heating circuits. Only the supply and return lines are connected to the primary circuit in the opposite order: first the first and then the second.

It is reasonable to include no more than 4 boilers in such a scheme. The use of additional devices is not practical.

What is needed to connect the solid fuel and electric boiler

Consider not only schemes of connecting two boilers in one heating system, but also what is needed for these purposes:

Two circulation pumps. And one of them needs a slightly higher capacity. This pump must be installed on the solid fuel boiler if it is installed in the heating system as the main.

Two check valves. Each of them is installed in the supply upstream of the boilers. Check valves allow you to separate the flow of coolant and properly organize the heating system.

Cocks and disconnecting connections. Assembling the heating system should be organized in such a way that it is possible to replace the circulation pump or a “sticky” non-return valve in emergency mode. Therefore it is important to install not only cocks, but also split connections with union nuts (American-style) in front of the most important elements of the heating system.

Boiler Safety Group. We recommend installing multiple boiler safety groups, on each individually. First, since the operation of each boiler in the heating system will be autonomous, it is very important. Secondly, given the fact that the electric boiler is always installed above the solid fuel, it is very important to organize an air vent in the supply.

Expansion tank. It can be one, the main thing is its volume, which is chosen according to the liters of the heating system. Connecting the expansion tank is recommended to perform on the return line of the system.

So, above were listed the main elements when connecting two boilers in a heating system. Thus, its operation will be organized correctly, and the power consumption will be lower than when connecting two boilers in series.

Closed type system with a heat accumulator

Closed heating system does not require the installation of an expansion tank, so the installation process is greatly simplified. Most gas boilers are equipped with an expansion tank and a safety valve.

For the proper assembly of such a heating circuit, it is necessary to follow certain instructions:

• To the supply connector of the gas boiler is connected to the tap and the pipe that goes to the heating appliances.
• 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.
• From them the pipe that goes to the heating boiler is diverted. At the end of the pipe at a short distance from the unit, powered from a gas cylinder, the installation of a cut-off valve.
• Pipes leading to the heat accumulator are connected to the supply and return pipes. One of the pipes is connected before the pump, the second pipe is connected behind the radiators. Each pipe is equipped with a faucet, also here should be connected pipes that have been previously cut in front of the heat accumulator and after it.

Installation of a closed system with two boilers. gas and solid fuel

In the arrangement of such a heating system, solid fuel and gas boiler in one circuit are connected in parallel with the mandatory installation of a safety group. Open expansion tank is replaced by a closed membrane reservoir, which is located in a special room.

As part of the safety group the following elements are marked:

• Valve for removing accumulated air.
• A safety valve that can be used to 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 running from the heat exchangers of gas and solid fuel boilers in one system, cut-off valves are installed.
• On the supply pipe, coming from the solid fuel boiler, there is a safety group. This may be located near the valve.
• Connect the supply pipes of both boilers. In the line coming from the solid fuel boiler, a damper is inserted in advance, which will organize the movement of the coolant in a small circle. The distance from the boiler to the point of connection can be up to 2 meters. A paddle valve is installed next to the bridge. When you turn off the boiler running on wood, such a scheme does not allow the heat medium to flow into the boiler, despite the strong pressure that creates a gas boiler.
• Perform the connection of the supply line to the heating devices, which are located in different rooms and at different distances from each other.
• Installation of a return line between boilers and radiators. In a certain place, it is divided into two pipes: one is sent to the gas boiler, the other. to the solid fuel unit. A spring valve is installed in front of the device that operates on a gas cylinder. To the other pipe is connected a jumper and a three-way valve.
• Membrane expansion vessel and pump for forced circulation of coolant mounted in the area before the return line separation.

Scheme of connection of two boilers in one system may well be used when installing a universal combined heating boiler.

How to connect the gas boiler and solid fuel boiler in one. features of the installation

Parallel connection of boilers

In case of parallel operation (in case of shutdown of one of the boilers automatics), water from return flows through the disconnected boiler, overcoming the hydraulic resistance of its circuit, which means additional electricity consumption for the circulation pump. In addition, the return flow (chilled water), after passing through a non-working boiler, is mixed with the supply from the boiler that remains in operation, which in turn has to increase its capacity to compensate the offset from the return flow. To avoid this happening, the master plumber has to block pipelines manually (with valves), or install automation, equipped with servo drives.

This process is performed in this sequence:

• Do your own hands to install ball valves on boiler fittings. To ensure sealing on the threads of fittings wrap hemp, foum tape or thread. It is worth adding that before fixing shut-off valves or filters, you should always wind one of these elements on the threads of metal pipes. If you plan to use polypropylene or metal-plastic pipes, you will have to conduct soldering and use special fittings. Features of these processes can be found in various videos.
• Connect to one tap a pipe for the supply of coolant to the heating system installed in the house.
• If necessary a safety group is mounted.
• On the return pipe of the heating system put the expansion tank (of course, if there is a need for it).
• Install the ball valve and water treatment filter. The last one shall be installed on the horizontal part of the pipeline. It can also be installed on a vertical pipe, but in this case a special variant of the filter must be used. It is installed in such a position so that the direction of the arrow shown on it coincides with the direction of the coolant flow.
• After the filter the second ball valve is installed. These cocks are needed to facilitate the cleaning of the filter. They shut off with their own hands and clean the filter.
• Connect the return pipe from the heating system to the boiler.
• Connect the “hot” DHW pipe to the tap located on the desired branch.
• In the return line for the trimmer from the DHW is cut into a water pipe. Of course, at the beginning of this pipe put a ball valve. It will stop the flow of cold water after it fills the entire heating system installed in a private home and DHW.
• On the return pipe from the DHW before entering the boiler put a ball valve, water treatment filter, magnetic filter and ball valve.

The circulation pump was not mentioned here. Wall mounted two-circuit boilers always have it. For floor boilers, designed for natural circulation of the coolant, it is not necessary. If previously installed an apparatus for natural circulation. And then wanted to make the coolant flow forced, will have to put two circulating pumps: one on the return line for the heating system trimmer, the other on the return line for the DHW trimmer.

Rules of installation on the wall or floor

The gas unit must be placed inside a separate room. Which meets such requirements:

• There is a window that can be opened at any time.
• Existence of a functioning ventilation system.
• The presence of gas and water pipes.
• The presence of an outlet for the circulation pump and electronics. Of course, it must be the end of a separate branch that comes from the electrical panel. This cable must be connected to a separate circuit breaker. In addition to this, earthing is compulsory.

There are also requirements for the proper placement of the boiler in the house. They are like this:

• The distance between the main element of the heating system and other gas appliances must exceed 20 cm.
• There must not be a window in the vicinity.
• The distance between the boiler and the socket must be at least 0.5 m (at least that is what the manufacturers recommend). In general, the further the socket from the boiler, the better. It is worth adding that some models have a power cable without a plug. This means that the wire must be connected with your own hands immediately to the circuit breaker placed in the switchboard.
• The space between the side walls of the boiler and adjacent walls or objects must be more than 15 cm.
• The wall on or near which the boiler is installed must be solid and covered with non-flammable substances. If the wall is such that it can catch fire, it must be covered with at least 3 mm of non-flammable material. This is often noted in various videos.

Mini boilers

Boiler models are now available with an expansion tank, pump, valve and pressure gauge. It can be a heating element, electric, diesel, gas units with forced draught. These units can be called a mini-boiler room. Thus, safety valves in the scheme of electric heating of a private house with a pump are mounted immediately on the heat exchanger along with the heating element. This design allows you to quickly dump the excess coolant, if it boils when the pump stops.

Scheme to connect the boiler to the heating system in this case is not complicated. You only need to install two ball valves, which can cut off the boiler in case of need. Repair of the unit or any preventive maintenance will not be difficult.

Equipment with an open gravity system

With an open gravity system, the entire load falls on the open expansion tank.

• Takes away the excess of the coolant;
• Compensates the increase in pressure;
• Evacuates air and hot steam when the coolant boils.

The volume of the tank should not be less than 10 percent of the volume of the heating medium. is possible. It is installed at the upper point of the circuit, where the dispersal manifold ends. From the tank backflow goes to the heat exchanger, with a slope that ensures the withdrawal of air s and the progression of the coolant under gravity.

Through the open expansion tank is usually filled with cold water to compensate for evaporation.

Boiler type selection

The type of heating boiler depends on how it should be connected to the heating system of a private property.

The easiest solution in this case can be called an electric unit, shown in the photo, because it only needs to be attached to the wall, connect to the network, set the parameters of the coolant heating and the house will be warm.

Плюсами электрокотла следует назвать:

• the need to constantly maintain voltage in the network, for which you must buy a voltage regulator and a generator, otherwise interruptions in power supply will lead to equipment failure;
• the high cost of electric boilers.

Gas heating units have a lower cost, but the connection of the heating boiler, working on natural gas, is more time-consuming and expensive work. Also, many problems arise during further operation.

• the variety of models;
• affordable price;
• It is possible to choose one or two-circuit scheme of arrangement of the heating system;
• low cost of maintenance.
• Complex installation of equipment and smoke extraction system;
• The problem with environmental friendliness associated with the type of fuel used;
• The need to constantly monitor their functioning.

Connection options for heating boilers

Heating heaters can be wall-mounted and floor-mounted. In the first case, the units are attached to the walls, they occupy less space, they do not require a separate room on the type of mini boiler room. In the second case, the equipment is placed on the floor, and they require a specially dedicated furnace room. The scheme itself, how to connect a heating boiler to the structure of the heat supply will not be particularly different.

What type of design has a heating unit, affects its capacity: a wall-mounted device can heat a smaller area, and a floor-mounted one. a much larger house.

Development of the project of installation

Once the technical specifications are obtained, you can move on to drafting the installation.

The project is developed taking into account all the requirements specified in the specifications. This also includes a scheme of laying gas communications: for a private home. along the site to the entrance to the house with an indication of this point in the drawing, and for an apartment. from the entrance to the gas supply pipe to the point of connection to the heating boiler autonomous system.

Do not start any installation work until the relevant project is drawn up, coordinated and approved

Project development should be carried out only by specialists with a license for this type of work. As a rule, the organization dealing with gas supply in a particular region (settlement) has a design department, where all such surveys, calculations and their graphic design are performed.

Boiler service menu

For all manipulations with the switching of modes there are only 4 buttons. Plus, Minus, OK/Menu, ESC.

It is important to understand that not all items in the boiler menu will be available to you, some of them will be available only if you connect additional devices to the boiler, such as external sensors or a solar collector. And most of the menu items are available only by service code, I will tell you about this below, but now “let’s practice on the pussycats

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And most of the menu items are available only by service code, I’ll tell you about this below, but now “let’s practice on the cats

Our kitty cats will be open to free access values. But first, read how to work with the menu.