Combined boilers for gas and wood

Standards for installing a gas-wood heating boiler

For the installation of a gas boiler with the possibility of burning wood, higher requirements are imposed than for conventional solid fuel equipment. The operating and connection standards are described in SNiP, SP and PPB. In particular, it states:

• Boiler room - for the installation of the boiler, a room with a total area of ​​at least 12 m2 and a ceiling height of 2.2 m is chosen.
• Walls and floors are tiled with non-combustible material: plaster and ceramic tiles.
• Supply and exhaust ventilation is required. For better air flow, the door frame is installed without a lower threshold.
• The boiler is connected to the electrical network through machines located outside the boiler room. Modern multi-fuel small-sized boilers for gas, firewood and electricity are protected against power surges. Despite this, manufacturers recommend connecting through an uninterruptible power supply with a built-in stabilizer.
• Natural light is required. The dimensions of the window openings are calculated depending on the boiler performance.
• Universal heating boilers for gas and wood, with a capacity of up to 40 kW, can be installed in any room used for household needs. A heat generator over 40 kW is installed in a separate room intended exclusively for the needs of the boiler room.
• In the place where the chimney passes the floor slabs and the roofing cake, fire-prevention cuts are provided. The pipe is insulated with a non-combustible mineral seal.
• A spark arrester and a deflector are installed on the chimney head to increase the traction force.

When connected to the main gas, the first start-up of the boiler is performed in the presence of an inspector. In the absence of violations, the inspector of the Gas Service will make a note in the equipment passport about putting it into operation.

Pros and cons of using wood and gas boilers

Heating boilers for the home, running on wood, gas and electricity, as practice has shown, are convenient to operate and easily replace two single-fuel units. The advantages of universal multi-fuel models are:

• Combustion process automation.
• Long operating time from one bookmark of firewood.
• Lower cost compared to two boilers operating separately on gas and wood.
• Fast switch over to reserve fuel source.
• The ability to work in an unheated building to prevent the coolant from freezing.
• Small size.
• Meeting the needs of hot water supply - floor-standing double-circuit heating combined gas-firewood boilers, operate as a flow-through water heater. Single-circuit analogs are connected to an indirect heating boiler.

Household hot water gas-wood heating boilers have several disadvantages:

• High price.
• Large weight, due to the fact that several combustion chambers are built into the structure.

This is where the disadvantages of universal boilers end. It is clear that domestic equipment has flaws, but in general, even Russian units work flawlessly. Multi-fuel boilers are easy to operate and in many respects surpass units operating on only one type of fuel.

Calculation of the power and temperature of a warm water floor

Design features

The range of heating boilers is presented in different models. Some run on gas, others on electricity, and still others on liquid fuel. Each variety has its own operational advantages and disadvantages. The disadvantages of using certain installations haunt designers and technicians. Therefore, they decided to combine some models, and combined heating devices were born. They can work, for example, on solid fuel and gas at the same time.

This combination made it possible to minimize emergency risks and organize the operation of the same solid fuel boiler in an autonomous mode.How do such installations work, and where is their use more than justified? As a rule, universal boilers are always equipped with an additional number of nozzles. They can be used to connect underfloor heating, heating radiators, greenhouse control systems, pool water heating or sauna heating.

The gas burner in such a boiler is located below the combustion chamber, where firewood, briquettes, sawdust or coal are laid. Therefore, if necessary and when switching, it allows you to completely burn the residual solid fuel. If the work is switched to solid fuel, the gas burner is automatically closed. For ease of use, a steel heat exchanger, which is responsible for heating the room, runs through the entire body. All walls are thermally insulated with special mineral wool, so the efficiency of the unit is almost 92%. And this is a very high indicator.

The heat exchanger for hot water supply is made of copper and is located in the upper part of the unit. Copper is not afraid of corrosion, therefore the service life of the coil is equal to the service life of the entire device as a whole. Universal boilers have lever and air dampers, which ensure the supply of the required portion of air.

How the installation works

The principle of operation of a gas-firewood boiler is trivially simple. The design uses two self-contained cameras. The furnace is located above the gas one. This feature allows the use of two types of fuel at the same time. Gas burners are capable of operating at low pressure. Therefore, it is often possible to see models that are connected not to central gas pipelines, but to cylinders with liquefied gas.

Note! In the event of a power outage, the gas-firewood boiler will not be able to operate on gas. And all because the products of its combustion in this case will not be independently removed through the chimney to the outside, and condensate instantly accumulates on its walls, clogging the chimney

If there is no light in the house, the boiler is heated exclusively with wood.

Installation advantages

There are quite a few advantages of gas-firewood boilers, so we will designate only the most basic ones:

• The main factor is the ability to save money and use cheap firewood instead of expensive blue fuel. If you run out of wood, you can switch to gas in automatic mode.
• The combined design allows the use of autonomous heating. Gas ensures the operation of the unit at night without additional fuel loading. It's also nice to come home after work to a well-heated house, knowing that the gas will maintain the desired temperature when there is no one to throw firewood into the stove.
• Universal combined boilers can have one or two circuits, which makes it possible to use the installation not only for heating, but also for supplying hot water for technical needs. Today, universal gas-firewood boilers are equipped with storage boilers, and there are models that can heat water to the desired temperature in a flowing manner. The choice is great, and it pleases.

But before deciding to buy such installations, experts recommend studying the features of their operation and disadvantages.

Varieties

Solid fuel boilers for heating a private house in most cases are represented by classic convection units. In them, firewood is burned directly, with the formation of a powerful flame, the heat from which is immediately taken by the heat exchanger. Disadvantages of this scheme:

• Lack of possibility of smooth temperature control;
• Not the highest efficiency;
• Virtually no automation.

With the help of traditional wood-burning boilers, it is difficult to maintain a certain temperature - the intensity of combustion, if regulated, is within extremely small limits.

Pyrolysis wood-fired boilers are an alternative to convection appliances. They are built according to the gas generator scheme. Firewood burns here in an oxygen-poor atmosphere. In fact, they do not burn, but simply smolder. Due to the high temperature, they begin to release pyrolysis products that are flammable. Combustible gases are burned in a separate chamber (called the afterburner), where secondary air is supplied. And in order to be able to adjust the intensity of combustion, the equipment is equipped with blowing fans.

Boilers built according to the pyrolysis type are more complex than their convection comrades. Here we see two chambers - in one, firewood is smoldering, emitting pyrolysis gases, and in the second, these gases burn out at a very high temperature, reaching + 800-1000 degrees. The released heat is absorbed by the same fire-tube heat exchanger and partially by a protective water jacket (if any).

Pyrolysis wood-fired boilers are endowed with automation systems that control blowing fans. As soon as the temperature in the heating system with batteries reaches the set limit, the fan stops, the flame in the afterburner goes out. This happens until the temperature in the heating drops - then the blowing fan starts up, a humming flame reappears in the afterburner.

Pyrolysis gas-fired wood-fired boilers need dry wood. Using raw logs, pyrolysis will be difficult or impossible. The efficiency of this equipment reaches 90%, as the calorific value of solid fuel increases.

Heating combined boilers wood-gas

The most economical types of energy sources are currently wood and gas. That is why it is recommended to use combined wood-gas heating boilers to organize heat supply for private houses.

Combined wood heating boiler-gas

Structurally, boilers of this type have two combustion chambers for each type of fuel. This leads to the large dimensions of the heating equipment. Depending on the functional features, combined wood-gas heating boilers can have one or two heat exchangers. In the first case, they are common to each combustion chamber. In double-circuit combined heating boilers, the DHW function is performed using one of the types of fuel.

For all combined gas heating boilers, before installation, it is necessary to correctly issue permits.

At the same time, the Management Company in the Technical Conditions will focus on the technical properties of the gas component of the equipment.

It is important that in the design of combined boilers for heating a house, the characteristics of the solid fuel part do not affect the gas

There are two types of combined wood-gas heating boilers:

• With separate combustion chambers. These are mainly factory models with two circuits. One of them heats water for heating, and the second provides hot water supply;
• With a common combustion chamber. This is more true for self-made installations, when you need to minimize the cost of arranging heating a country house with a combined boiler. The standard boiler is fitted with a factory gas burner. In the case of using firewood, it is dismantled.

The latest models have the most controversial reviews about combined heating boilers. Basically, these are self-made structures in which the heat exchanger is not designed for high thermal effects during the operation of a gas burner. This is what causes the frequent failure of the boiler.

Criterias of choice

The Kupper boiler is characterized by the optimal price / quality ratio.

When choosing a boiler, it is worth considering the following indicators:

• Heated area. Approximate efficiency calculations are performed according to the formula 1 kW = 10 sq. M. For example, in the central part of Russia, to heat a house with an area of ​​150 square meters, a device with a power of 15 kW is required. For colder regions, a more powerful unit is needed. To heat a similar house in Siberia, it is worth taking a device with a capacity of 30 percent more. When connecting a second DHW circuit, add another 15–20 percent to the total value.

• Material. Cast iron equipment can last 35 years, it has the best thermal and technical performance. But such units are unstable to mechanical damage and weigh a lot. Steel devices are cheaper, they are not afraid of shocks, but their service life is on average 10-15 years shorter.
• Firewood loading type. More often, devices are made in which a side supply of fuel is provided. But there are also top-loading models. A similar design is used in gas-fired boilers. The main advantage of the solution is the possibility of pre-drying the wood, which increases the heating efficiency.
• The ratio of the volume of the combustion chamber and the output of the boiler - how many times during the day it is necessary to load fuel. For devices made of steel, this value is on average 1.5-2.5 l / kW versus 1.1-1.4 l / kW for cast iron.
• Burn protection. An important characteristic, especially with open access to the boiler room. This is achieved by insulating the handles of the combustion chamber and other highly heating elements that protect the cases and grates.
• Additional functionality - automatic sensors, built-in storage boiler, remote control system. All this makes the operation of the heater more convenient. But for some options, it is necessary to connect to an electrical power source, which deprives the unit of autonomy.

Disadvantages and Benefits

Universal heating boilers are quite large when compared with analogues that use only one type of fuel. But on the other hand, such installations are much smaller than those that use 4 types of fuel.

The main advantages of wood-gas heating boilers:

1. They allow you to provide a kind of autonomy. When the gas runs out, you can always switch to firewood;
2. Such installations are always equipped with all the necessary nozzles and connections so that the owner can easily connect a conventional home heating system or a "warm floor" structure;
3. Combined wood-gas boilers can be double-circuit or single-circuit. Thanks to this, you can easily access a boiler for heating water or heat water in a flowing way.
4. The disadvantages of combined boilers include:
5. Boilers of this kind need a separate room, which can be a rather costly solution in terms of space;
6. The more powerful and heavier the combined boilers, the fewer additional features they have available. For example, high-performance equipment may well not be equipped with an anti-freeze system or a secondary circuit for additional heating of water. On the one hand, this is a trifle, but on the other hand, it is a very useful function, which is sometimes difficult to do without;
7. The design of increased complexity significantly overestimates the cost and makes it difficult to carry out service;
8. Their heavy weight creates many difficulties during transportation or installation. In addition, such boilers are produced mainly in floor-standing design.

After you have decided on the need for hot water and the heating system, you are faced with the selection of a combined boiler in terms of power that can satisfy the necessary conditions and requests.For calculations when choosing a power, it is necessary to take into account the fact that about 1 kW of boiler power is spent for every 10 square meters of room.

If you need hot water, then the power will have to be increased by about thirty percent. The advantage is that the additional power will be used exclusively for preparing water. The temperature in the house will not drop.

Construction of a universal firewood-gas boiler

How to choose a combi boiler?

Available types of energy are the main criterion for choosing combi boilers. The most demanded models are fuel equipment, which must run on coal or wood. The popularity of pellet boilers is growing; this environmentally friendly fuel is becoming more and more affordable. They show good efficiency, which is not lower than that of a wood-burning boiler.

In addition to choosing the fuel on which the heating equipment will operate, it is necessary to pay attention to important technical characteristics when choosing a boiler. The main parameter of this technique is power

The number of heating circuits is also an important characteristic of the equipment. If you are purchasing a boiler for a home with permanent residence, then a two-circuit model will be the best choice. It will provide not only heat, but also hot water at minimal cost.

Do not forget about such a simple but important characteristic of heating equipment as the dimensions of the boiler. Most of the models have impressive dimensions, which, with a limit on the usable area, can be a serious problem

This is especially true for boilers with several furnaces.

It is also worth paying attention to the complete set of equipment with automation. It is designed to provide the most simple operation and a high degree of safety, to protect against freezing

Electric fire boiler device

The device of multi-fuel heat generators uses a combination of elements capable of converting energy received from various sources into heat. Electric wood-burning units in their design practically do not differ from conventional boilers operating on wood and coal.

Structurally, they consist of:

• a body, inside which a water jacket or heat exchanger of heat or water tube type is located;
• a combustion chamber with an air supply and chimney system;
• ash chamber for accumulation and removal of solid combustion products;
• TENA (tubular electric heater) or a block of heating elements;
• control equipment.

Depending on the chosen method of controlling the air supply to maintain combustion, heat generators operating on solid fuels can be equipped with either a mechanical draft regulator or an electric blower fan.

Principle of operation

The operation of the combined firewood-electricity heat generator is based on the principle of automatic or manual transition from solid fuel to electricity. At the moment when the firewood laid in the combustion chamber burns out, electric heaters come into operation, maintaining the temperature of the coolant within the specified limits. The switching on and off of the heating element or the block of heating elements is carried out by a switching device when it receives a signal from a temperature sensor installed in the heating circuit.

Benefits of using

The presence of an electrical component in a solid fuel boiler can significantly increase the reliability of the entire heating system and the ease of use.

The relatively small complication of the combined unit design during operation allows:

• maintain a comfortable temperature when heating the house both during the day and at night;
• avoid defrosting the heating circuit of a country house, cottage or summer cottage in case of a long trip;
• use electricity during the absence of firewood or coal as a backup source of heat.

Features of gas-fired boilers for home

First of all, it is worth noting that in most cases the gas main is taken as the main fuel, and they switch to wood heating in case of shutdown for periods of maintenance or accidents. Of course, for a completely universal approach, it is worth installing a combined firewood-gas-electricity device, but not everyone can be satisfied with the cost of electricity.

In general, combined boilers can be fired with different solid fuels, with almost no changes in its design. So, firewood, coal, briquettes, pellets - everything is at the same level in terms of prevalence, the choice depends on the price of various species in a particular region. That is why gas-wood boilers are popular, solid fuel can be easily replaced with an analogue.

Rice. 2 External view of a gas-fired boiler

Secondly, it is important to consider that solid fuel heating boilers are made of steel and cast iron, which makes them resistant to constant high temperatures during the heating season. This is especially important if coal is used as fuel, which gives a noticeably higher temperature in the furnace.

But it also adds to the hassle. The heavy weight of the equipment in some cases requires reinforcement of the floor covering in the room in the house allocated for its installation. Cast iron boilers for heating gas-firewood are required without fail. Gas-water modifications made of light grades of metal can be mounted on a regular floor, in place of the previously occupied wood or coal stove. Firewood-gas-electricity appliances are usually lightweight.

There are two more types of combined models: single-circuit (they work only to heat the heating system) and double-circuit (the second circuit heats water for the water supply system in the house). So, the gas-wood device can be used as a boiler even in the warm season. The same applies to the wood-gas-electricity appliance.

It is also worth noting this feature. In addition to the removal of smoke through the chimney, when burning with solid fuels, there are solid combustion products that settle in the pallet and require periodic disposal.

The most interesting for heating boilers are universal gas-wood-pellets, which have the ability to work independently without human intervention for a long time. Such a heater, instead of wood or gas, is capable of working with special pellets. Such a combined option eliminates the need to stock up on firewood, because pellets are usually always available for sale. Alternatively, a combined boiler is still convenient.

Finnish combined heating boilers

Finnish boilers occupy a fairly large market share. There are several reasons for this. First, their climate is close to ours, so we should expect that their capacity will be sufficient in our conditions. Secondly, most of the campaigns have been operating for a long time, and, therefore, have gained experience and have a certain potential. Well, and thirdly, their quality is at the same level.

Jäspi Group is one of the Finnish companies operating in this sector of heating equipment. Their boilers have a good reputation and are all equipped with heating elements. In the basic configuration of the boilers there is one heating element for - 6 kW. 2 or 3 pieces can be supplied under the order.

Finnish combined heating boilers Jäspi

In the Jäspi VPK line, you can use wood, pellets, diesel fuel, gas. Jäspi Tupla has a high efficiency, copper coil, diesel / gas and solid fuels. In this line, the furnaces are autonomous, only the combustion products go into one pipe, therefore the smoke channels are combined in front of the chimney fitting. Working on gas or diesel fuel is characterized by high efficiency.With the correct setting of the burner, the fuel is burned almost completely, so that cleaning of this combustion chamber is required only once a year. When using firewood, their size depends on the modification: in Tupla 1 S - 35cm, in Tupla 2 S - 50cm.

Some technical characteristics of Jäspi Tupla and Triplex

Jäspi Triplex boilers are a model with a reduced emission of harmful substances into the atmosphere, equipped with new ceramic grates. It is also possible to use 35 and 50cm firewood. For modification with a firewood length of 50cm, top burning can be realized.

The Jäspi Biotriplex range uses the latest developments: switching from pellets to firewood and vice versa does not require changing equipment. The two fireboxes are independent from each other.

Varieties of combined boilers

Divide universal heating equipment depending on the type of fuel used.

Rice. 1 Internal structure of combi boilers

So, the following combined options are distinguished:

• Gas + Solid fuel. It allows you to quickly replace the main gas when it was turned off as a result, for example, of an accident on the line. A wood-fired boiler is one of the most popular solutions in view of the good availability of wood.
• Gas + Liquid fuel. Such options are convenient in case of periodic interruptions in the gas supply, but they require the organization of storage of diesel fuel supplies.
• Gas + Electricity + Liquid fuel. Combined option for savings in the absence of a guarantee of timely supplies of gas and diesel fuel.
• Gas + Solid and liquid fuels. One of the most versatile models for heating cottages. An excellent substitute for wood-burning stoves.
• Gas + Solid and liquid fuels + Electricity. This model makes the owner of a private house completely independent of tariffs and other factors that do not affect the change in energy carrier. For example, a firewood-gas-electricity appliance.

There are universal boilers without connecting to a gas main, for example, for coal and firewood, with the ability to connect heating elements for power supply from electricity. Combined gas and firewood heating boilers are often installed in conditions of interruptions in gas supply. Firewood for heating, including special pellets (pellets), cause less inconvenience during storage than other types of fuel. Yes, and there is no smell, as, for example, from diesel fuel (and a gas boiler sometimes gives a slight smell).

Another option - a combined gas-firewood-electricity boiler - allows you to become completely autonomous with any changes in tariffs and in other situations. For a firewood-gas-electricity appliance, you don't have to worry about stocks of the same firewood, power outages, etc.