Owners of private houses who decide to install a solid fuel heating boiler are primarily concerned with 3 parameters - the unit's thermal power, its price and the duration of burning from 1 load. These parameters are interrelated, the greater the power and duration, the higher the cost of the heat generator. The only way to reduce costs is to make a long burning boiler with your own hands or to entrust the work to the craftsmen. Introducing 2 designs of TT boilers, detailed drawings and manufacturing procedures for heaters.
How does the duration of burning solid fuel increase
The dream of many homeowners is to put a solid fuel boiler, which does not have to run around with firewood every 4-6 hours. Using this, manufacturers and sellers of heating equipment apply the prefix "duration of combustion" to all heat generators in a row, including pellet ones, working independently up to 7 days.
It is customary to justify the duration of the combustion process using a smoldering regime with limited air supply. But burning wood and coal in this way is inefficient, and here's why:
- Wood and coal boilers achieve their efficiency of 70-75% during maximum combustion. When smoldering, the efficiency of the aggregate decreases to 40–50% (as with an ordinary potbelly stove).
- Smoldering firewood produces little thermal energy. Who needs a “long-playing” heat generator that does not fully heat the house?
- Freshly cut wood of certain species (for example, poplar, willow) and low-calorie fuel cannot be burned normally in smoldering mode.
In fact, solid fuel boilers of long burning are those that have an enlarged fuel chamber, only its size affects the duration of the process, ceteris paribus. The principle is simple: the more firewood is in the furnace, the longer they burn and give off heat.
Domestic boilers that can work from one bookmark for 8-12 hours on wood and up to 24 hours on coal are of the following types:
- classic, with forced air supply;
- acting on the principle of upper combustion (such as the Baltic "Stropuva").
It is quite realistic to make these designs of TT-boilers at home with the necessary tools and practice in welding. Even on the Internet, you can find drawings of mine boilers for solid fuel and sawdust, but such heaters are rather bulky and difficult to manufacture, and therefore deserve a separate topic.
Classic Continuous Burning Boiler
Reliability and efficiency of boilers has already been tested by time at various facilities. The technical characteristics of the presented model of the unit are as follows:
- power - 22-24 kW;
- the burning time (on average) on wood is 10-12 hours, at least 8 hours;
- the same, on coal - up to 1 day;
- Efficiency - 75-77%;
- maximum working pressure in the heating system - 3 Bar, nominal - 1.5 Bar;
- the amount of water in the boiler tank - 50 l;
- product weight - 150 kg;
- loading aperture size (width x height) 360 x 250 mm;
- the total volume of the furnace is 112 l, useful (for loading fuel) - 83 l;
- the depth of the furnace is 46 cm, the optimal log length is 40 cm.
For reference. The master makes boilers of long burning of different power, the line includes units for 16, 24, 36 and 130 kW. The price of the finished product for 24 kW when ordering from the master is about 450 u. e. All questions and clarifications related to the design of a solid fuel boiler and its manufacture can be discussed personally with Vitaly, whose contacts are listed on the page "Our Experts".
The device and overall dimensions of a long-burning wood-burning boiler for DIY manufacture are shown in the drawing:
The heat generator successfully operates both on wood and on coal fuel. The useful capacity of the firebox is calculated to the bottom edge of the loading opening, since it is undesirable to fill the chamber to the top. The boiler operates in the following order:
- After laying and igniting solid fuel, the doors hermetically close.
- At the electronic control unit, the desired coolant temperature is set, it is recommended not lower than 50 ° C. Then the unit is turned on by pressing the appropriate button, the fan starts.
- When heated to the set temperature, the fan turns off, air in the firebox stops. TT-boiler is in standby mode, firewood smolders very weakly and practically does not produce heat.
- After the temperature drops in the boiler tank, the controller gives a command to start the fan and the combustion process in the furnace resumes.
The controller modifies fan performance as it sees fit to maximize combustion efficiency. There is no burning by decay in this home-made boiler, it is either in a standby state, or it burns wood and coal in an intensive mode.
The internal structure of the unit is shown in the drawings of the boiler in the context of:
The heating system implements the classic method of burning solid fuels with direct heat transfer to the walls of the water jacket and to the roof, which is the bottom of the boiler tank. A fire-tube heat exchanger is immersed in this tank, taking the heat of flue gases. Heated air in the channel is supplied to the furnace from below, through the grate. Duration of burning is provided due to:
- Large volume firebox.
- Complete blocking of air access to the furnace in standby mode. After turning off the fan, the gravity damper closes, closing the duct and thus preventing the draft of the chimney from inflating the coals.
The device of the rear part and the fire tube heat exchanger is shown in the following drawing:
Tools and materials for manufacturing
Low-carbon steel grades St 3, 10, 20 are usually used for blanks for assembling a long-burning solid fuel boiler. The best option is St 20, the heat generators made from it last up to 15 years. Steel containing more carbon (St 35, 45) has the tendency to heat up on high temperature, and therefore is unsuitable for welding a heat generator.
If you have sufficient welding experience and the ability to buy metal at a higher price, then the combustion chamber can be made of heat-resistant steel alloyed with chromium and molybdenum (for example, 12XM, 12X1MF). How to independently determine the grade of steel with sufficient approximation is described in this article.
The list of blanks from which you will assemble a solid fuel boiler with your own hands is given in the form of a table:
Tip. Billets are best cut with guillotine shears somewhere in the workshop. So you save a lot of time on manual cutting and deburring.
Additionally, such materials will be required:
- equal-angle corner 50 x 4 mm for the manufacture of grates;
- pipe DN50 - to the heat exchanger and pipes for connecting the heating system;
- pipe DN150 - to the chimney pipe;
- profile pipe 60 x 40 mm for the air channel;
- steel strip 20 x 3 mm;
- basalt insulation with a density of 100 kg / m³ and a thickness of 2 cm;
- smooth sheet metal 0.3-0.5 mm with polymer coloring;
- ready-made handles on the door;
- cord, asbestos cardboard.
Of the tools, it is worth noting the welding machine, the grinder and the drill; for welding, the electrodes ANO-21 or MR-3C are used. The rest is a standard set of measuring devices and tools available in every home.
The automation kit used in the TT boiler, consisting of a control unit, a fan and a temperature sensor, is made in Poland (do not mix up with Chinese, it looks the same). The marking of the control unit is KG Elektronik SP-05, the fan is DP-02.
Assembly of the heating unit
First step The manufacture of a long-burning boiler consists in assembling a firebox case from metal with a thickness of 4 mm by welding on tacks. It all starts with the bottom of the unit, to which the side walls, the roof cover and the door openings are caught, as shown in the photo:
The bottom sheet is produced in each direction in accordance with the drawing, at the same time it serves as the lower frame of the ash pan door. Inside the chamber for welding, shelves from corners are fixed, where the grate will be supported. The assembled firebox is carefully boiled at all joints and checked for leaks.
Second phase - installation of a water jacket made of metal 3 mm. Its thickness at the side walls is 2 cm, therefore, pieces of steel strip should be welded to the firebox housing, releasing them by 20 mm. Steel sheets of cladding are clung to them.
Attention! The water shirt starts at the grate level and does not wash the ash chamber.
The so-called clips are staggered in the middle. This is a steel circle, passed through holes in the wall of the boiler tank and welded butt to the furnace. The second end of the clip is scalded around the hole, as shown in the photo:
A few words about how to make additional clips around the edges of the water jacket of a homemade solid fuel boiler. It is necessary to take a strip of 20 mm and insert it from the end between the walls to a depth of 50-100 mm, and then weld on both sides.
Third stage - installation of flame tubes in the upper part of the boiler tank. To do this, in the rear and front wall according to the drawing, holes are cut where pipes are inserted. Their ends are hermetically boiled, like all joints of a water jacket.
Fourth stage - manufacture of doors and grate. A strip in 2 rows is welded to the doors from the inside, and an asbestos cord is inserted between them, this will be the seal of the narthex. Grid-irons are made from corners No. 5, welded with an outer corner down. So they serve as diffusers of air supplied by the fan to the ash pan.
In the fifth stage Fittings for connecting the supply and return pipes cut into the walls of the boiler tank, a chimney pipe and an air channel from a 60 x 40 mm pipe with a fan mounting flange are installed. The duct enters the ash chamber in the middle of the back wall, immediately under the water jacket.
Stage six - welding of door hinges and embedded parts 2 cm wide for fastening the decorative lining of the boiler for long burning.
Seventh Stage, last. The boiler tank is lined on the sides and on top with basalt insulation, the latter is fixed with a cord. After that, it remains to screw the sheets of painted metal with screws to the embedded parts and install the doors.
At the end, a fan is attached to the counter flange of the duct, and the control unit is mounted on the boiler from above. The temperature sensor must be inserted under the basalt insulation from the back of the unit. In addition, a number of useful additions can be made to the design of a home-made long-burning boiler, according to your desire:
- to integrate in the boiler tank a water circuit for heating water on the hot water supply;
- Provide an immersion sleeve for installing the thermometer - in case of a power outage when the controller display goes out;
- the same for mounting a security group;
- install an electric heater, heating the coolant after burning wood.
A few words about how to circulate hot water in a solid fuel boiler in order to heat it for household needs. It is necessary to take 10 m of a copper tube with a diameter of 8-12 mm and bend a coil in the form of a spiral from it. The latter is wound inside the boiler tank around the flame tubes, and the ends are brought out from the back of the unit. We get a double-circuit boiler of long burning.
Note. The practice of operating these heat generators showed that the installation of an electric heater is necessary for those homeowners who want to heat the house at a night rate.In other cases, the burning time is enough not to run into the boiler room in the middle of the night in order to toss firewood.
The legs of the unit can be attached at any stage by choosing suitable sections of metal. For details and secrets of assembling a TT boiler, see the author’s video of the master - creator of the heating unit:
Top burning boiler
In the post-Soviet space, these heat generators are known in two varieties:
- Baltic units of the company "Stropuva" (Stropuva) and their derivatives from other manufacturers.
- Wood stoves like "Bubafonya".
It is not known which of the heaters appeared earlier, but the Bubafonya stove gained wide popularity as a heater for summer houses, garages and other buildings with low requirements for the aesthetics of the product. What can not be said about boilers of the upper combustion, although many for some reason consider them the only possible version of solid fuel heat generators of continuous burning. In fact, their only trump card is the same - a large firebox.
The principle of operation of such boilers is to burn fuel, crushed by the load, from top to bottom. Moreover, air is supplied to the combustion zone also from above, through a telescopic pipe connected to the load. The working diagram of the unit is shown in the figure:
During the operation of Stropuva boilers, many shortcomings were manifested, as evidenced by the reviews of the owners on the forums:
- You can not throw logs into the furnace until the previous tab burns. Physically, this is possible, but then the principle of upper combustion will be violated, the flame will cover all layers of fuel.
- When working on fresh sawdust and other small debris, the remaining fuel “hangs” on the walls.
- The efficiency of the TT boiler is not too high, since it does not have a heat exchanger. Due to the air heating chamber and the large firebox, there is no space left for the heat exchanger.
Preparation of materials
The round body creates some inconvenience in the manufacture, but you won’t make it square either - the fuel will “hang” in the corners. There is a problem with the assembly of a telescopic pipe with a load, so this part is better to take from the Bubafoni furnace. A drawing of a long-burning boiler, comparable in size to the classic version, looks like this:
Before making a boiler, we select materials according to the drawing:
- pipe DN 400 with a wall of 5 mm - on the firebox;
- the same, DN 50 - for air supply and water pipes;
- the same, DN 100 - for the chimney;
- a blank of a sheet 10 mm thick round with a diameter of 38 cm;
- strip 40 x 4 mm - for air distributors;
- reinforcement with a diameter of 16-20 mm of a periodic profile - on grates;
- basalt cotton wool with a thickness of 3 cm and a density of 100 kg / m³;
- sheet metal with a polymer coating.
The choice of material for the water jacket depends on the method of its installation, because the home craftsman is unlikely to have rollers in stock that can give the metal a thickness of 3 mm cylinder shape. The options are as follows (shown below in the diagram):
- Scheme number 1. Take a thin-walled pipe of larger diameter, although it is not easy to find one, but the ordinary one will heavily weight the boiler.
- Scheme number 2. Bend two sheets of metal in 2 places at an angle of 60 °, and then weld two halves together. You will need a press listogib.
- Scheme No. 2 in another design. Cook a shirt of 6 sheets - segments on clips.
- Scheme number 3. Weld a rectangular box, which will increase the volume of the boiler tank.
You will also need 3 mm sheet metal on the door frame, the bottom with a lid and an air damper.
Heat generator manufacturing
Work begins with cutting blanks and openings in the pipe wall according to the dimensions in the drawing. Doors are made of cut parts, canopies and purchased handles are fitted to them. From the reinforcement, the grate is shown, shown in the photo:
In general, the assembly algorithm of the upper combustion boiler looks like this:
- Cut a hole in the round workpiece for the load, insert the pipe into it and scald.
- Weld 6 curved strips to the bottom of the load, which will serve as air distributors.
- Attach the bottom to the firebox, install inside the grate.
- After cutting a hole in the center of the cover for the air pipe, fit it to the firebox. Before this, you need to put the pipe with the load in place.
- Weld the flue pipe.
- Mount the water jacket according to the selected scheme, hermetically scald all the joints.
- Tie in coolant nozzles.
- Carry out insulation and casing of the boiler, install doors.
- Place a shutter on top of the air pipe.
It is difficult to install automatic equipment and pressurization on a boiler with a long upper combustion, because the fan cannot be attached to a moving pipe. It is necessary to make a flexible sleeve, and to provide an immersion sleeve for the temperature sensor. It is impossible to put it under the insulation, because the combustion zone in this type of heaters is constantly shifting down.
Conclusion
Both do-it-yourself solid fuel boiler designs of long burning have the right to life. But to make a reliable heating unit is not easy - metal joints need to be boiled in a high-quality and tight manner. One cannot do without the experience and qualifications of a welder. Hence the conclusion: if you see that you can’t overcome the self-assembly or if you don’t have time for this, contact the masters. So you will save up to 50% of the money compared to buying a factory TT boiler.