- What steel the heater was made from
- How the wood-burning “Titan” works
- Furnace manufacturing and lining
- Ash pan and draft adjustment
- Chimney water jacket
- Possible refinement methods
- Installation and use rules
Even the basic skills of working with arc welding are enough to make heating equipment for your home yourself. We propose to consider aspects of the self-made development of a wood-burning water heater: the materials used, the assembly technique and the scaling of the installation to fit your needs.
What steel the heater was made from
Self-production of a water heating column will save at least 50% of the funds that could be spent on purchasing a factory-assembled heater. However, the design of such a device is rather complicated, in addition, a significant amount of rolled metal will be required for its manufacture..
A wood or coal furnace acts as a heating source. The lowest consumption of materials with optimal strength indicators can be achieved when manufacturing a firebox in the form of a cylinder with a diameter of 50 cm and a height corresponding to the volume of the heating tank. For the manufacture of the furnace block, low- and medium-carbon alloyed steels with a scaling temperature of at least 400 ° C are used. The operating temperatures in the furnace are not particularly high, however, the use of conventional structural steel is fraught with rapid carbon burnout.
The heat resistance of steel increases with the content of nickel and chromium in it, at the same time, the difficulty of welding increases. Steels with a high content of alloying additives belong to the class of stainless steel, their welding is carried out mainly in a shielding gas environment. The golden mean in this regard is austenitic steels of the AISI 304 (08X18H10) type, which are welded with 308L / MVR electrodes in soft current modes at a high speed, as well as the more common grade 20 steel, which is well welded with a wide range of low-carbon electrodes, for example, E50A UONI 13 / 55. In both cases, the sheet thickness is selected in the range from 4 to 8 mm.
For a water tank, heat resistance is not so important, but tightness is important, therefore, alloys with good weldability should be chosen. Here, the use of medium-carbon steels without alloying is encouraged, but mandatory anti-corrosion protection of internal surfaces. The wall thickness of the tank is about 2–2.5 mm; it will be too difficult for thicker metal to shape it at home. The use of stainless steel in the construction of the tank is excluded only for the reason that it becomes necessary to weld the lid and the bottom with the chimney pipe, which is usually made of ordinary “black” steel.
How the wood-burning “Titan” works
There is nothing tricky about the Titan. This is an ordinary wood-burning stove, the lid and chimney of which have a water jacket. To facilitate maintenance and assembly of a homemade structure, it is recommended to make a modular product.
Wood-burning water heater device: 1 – firebox; 2 – ash pan door; 3 – furnace door; 4 – cold water supply pipe; 5 – water tank; 6 – hot water intake pipe; 7 – chimney
The combustion block is a cylinder without a cover, divided into a combustion chamber and an ash pan by a massive grate. To reduce useless heat loss and extend the life of the metal, the firebox is lined with fireclay bricks from the inside. In addition to the ashpit doors and the firebox with a special form of the vestibule, there is nothing remarkable about the structure of the combustion block..
Hot gases, rising through the chimney, give off heat to the water inside the tank, while heating occurs mainly in the lower zone, which forces the liquid to circulate and mix. In order for heat transfer to be as efficient as possible, the chimney is equipped with radiator fins. It is also important to maintain the tightness of the tank without slowing down the heat transfer from the combustion chamber. For this reason, the tank is welded as a one-piece container, which is “put” on top of the firebox glass with the formation of a double narthex around the perimeter.
Furnace manufacturing and lining
The biggest challenge in making a homemade Titan is rolling a sheet of steel into a cylinder. With a significant metal thickness, this is not so easy to do, parts should be welded without stress, because when exposed to high temperatures, the strength characteristics of the weld are greatly reduced.
Initially, you should select the assumed internal diameter of the furnace in the range of 50–70 cm and cut two discs to this size. According to the diameter, the circumference is calculated, along which a strip is cut out of the sheet, from which the walls of the combustion block will be formed. The height of the firebox, as already mentioned, is selected according to the volume of the tank: about 5 kW of heat is consumed to heat every 50 liters of water, which corresponds to about 1 kg of dry firewood. Thus, for a 200 liter heater, the firebox should freely accommodate 4 kg of firewood, excluding the ash pan volume. The higher and narrower the heating column, the more efficient the heat transfer occurs, but the Titan’s stability decreases.
The cut steel sheet is laid horizontally with two discs vertically positioned on its short edge. One is placed parallel to the long edge with a slight indentation – this disk forms the bottom of the combustion block. The second disk is installed parallel to the first one with a distance of 20–25 cm from it – this is how a partition is formed between the firebox and the ash pan. You can immediately cut an opening in the partition, the size of which is 40-50 mm smaller than the available grate.
The two discs act as a rigid mandrel to roll the cylinder. First, they are welded to the strip on both sides with tacks 10–15 mm long with careful control of the perpendicularity of the installation. Further, the metal is recovered along the disks with a sledgehammer, with a metal thickness of more than 5 mm, heating with a propane torch may be required. When the two parts to be welded are tightly pressed, the perpendicularity of the position of the disks is checked, after which the weld seam continues for another 10-15 mm and so on until it is completely circumvented. When the seam is completed for the entire length, it is covered with another one: the electrode is led without separation with heating and surfacing of a wide zone, the weld pool is displaced along a zigzag. After welding the discs to the wall, a longitudinal seam is welded from the outside.
When the furnace body is assembled, it is lined with fireclay bricks from the inside without a binder in the seams; the thickness of the lining is about 50–70 mm. In order to accurately fit the stones to the size of the furnace, they are first placed vertically on a flat surface in a cylindrical well, the inner diameter of which is approximately equal to the diameter of the furnace block. In this case, the bricks are located close to the inner side and with the most uniform indentation from each other along the outer, diverging rays. The distance between adjacent stones at the most extreme points must be divided in half and the bevels of the resulting size must be removed with a diamond wheel, achieving a wedge-shaped shape. After that, the bricks are installed at the walls of the firebox from the inside, if necessary, they are adjusted to each other using angle grinders. The stability of the lining can be ensured by using a steel strip rolled into a ring and installed from the inside with a grip. After covering the walls, the grate is inserted inside.
Ash pan and draft adjustment
To complete the combustion block, it remains to cut out two doors – for loading fuel and cleaning the ash pan. First, you need to cut out two rectangular parts from a steel sheet 3-4 mm thick, the dimensions of which are 20-25 mm larger than the expected dimensions of the doors. For the ash pan, the lada should be small (under the size of the scoop) and be located close to the bottom. For the firebox, the width of the door is chosen approximately equal to the radius or slightly less, the height is about 25-30 cm.
When the door openings are marked on the outer surface of the firebox, four holes need to be drilled in the corners. The parts cut from the sheet are placed in place of future doors and straightened with a mallet, achieving the most snug fit. When the bend is formed, holes are drilled in the linings in a checkerboard pattern with a diameter of 8–10 mm, then the walls of the combustion block are cut out. The cut sections are placed from the inside of the overlays with even indents along the edges and welded together through the perforations.
The door canopies are made as easy as shelling pears: when they are in place, they are welded to the edge of the bent plates with an M10 nut, and 2 more nuts are added to the firebox body. It is enough to insert a pin, for example, from a turned pin, and the doors are securely fastened. For locking, an ordinary latch or a hook can be used, the handle of which is made in the form of a wire spiral, which can be gripped with bare hands even with a heated firebox.
It remains only to adjust the draft, without which the effective operation of the heater cannot be achieved. A hole is drilled in the center of the ash pan door for a thread of 8–10 mm. Around it, a dozen through holes of 10–12 mm are drilled with a “camomile”. Further, the central part of the formed lattice is slightly recessed inward with a couple of light blows, a thread is cut in the central hole. An ordinary bolt is screwed into it, threaded into a wide washer, the fields of which overlap the holes in the door by 15–20 mm. The washer is welded to the bolt rod, and a short bar is welded onto the head, which acts as a flywheel. When the bolt is fully clamped, the minimum clearance from the curvature of the door will be enough to maintain combustion, but by unscrewing the damper a little more, you can make the flame more intense..
Chimney water jacket
The second part of the homemade wood-fired “Titan” is a complex shape heat exchanger. Its manufacture begins with cutting a disc out of the same metal that was used to make the firebox. Lay the sheet on the combustion block and circle it from below along the entire perimeter. As a result, the disc must exactly match the size of the upper ring of the firebox glass. Initially, it will not be superfluous to check the geometry of the combustion block circumference and straighten it with a sledgehammer if necessary.
At the end of the disc, you need to chamfer on both sides with a width of 4–5 mm. Next, a strip 3–4 mm thick and 50 mm wide with a projection about 15 mm in one direction is welded to the edge. The weld seam must be airtight, so first a deep penetration is made, then the corner is cleaned up with a flap disc and a cosmetic seam is applied with heating a wide zone. Strip penetration is performed on both sides of the disc.
The side of the disc, on which the strip has a wider projection, is intended for joining the tank with the firebox. To ensure a tight rebate, a ring of smooth reinforcement is welded to the disc from the inside. In this case, the gap between the ring and the strip should be 1–1.5 mm more than the thickness of the furnace wall.
In the center of the disc, you need to cut a hole and insert a chimney pipe with a diameter of about 120 mm into it, placing it in the side of the short protrusion of the framing ring. The pipe length should be 20-30 cm longer than the planned tank height. Outside, plates of 40×300 mm with a thickness of 3-4 mm are welded onto the pipe in a chaotic manner. A more effective layer of heat is possible if you make slots in the pipe and insert ribs with a protrusion about 10–15 mm inward, but the tightness of the welded seams should be ensured. The pipe is welded to the disc strictly perpendicularly and tightly, penetration is performed on both sides.
Next, from a thin steel sheet, you need to roll up the outer wall of the tank and insert it into the framing ring. Having unclenched inside, the sheet will adhere tightly to the short edge of the disc, after which you can overlap with short tacks along the entire length. A connecting and then a cosmetic weld is applied to the longitudinal overlap of the resulting cylinder. The cylinder is installed on the bottom of the tank and boiled outside. The tank lid is made with a conventional disc cut from a thin steel sheet.
In the lower part of the tank, you need to weld a hole of about 20 mm and insert a threaded tube into it at the outer end. The pipe should be directed exactly to the center of the tank and not reach the chimney about 15–20 mm, which ensures effective dispersion and mixing of the incoming water. In the upper part of the tank, a short branch pipe for hot water intake is cut in the same way with an indent of about 10 cm from the lid.
Possible refinement methods
Despite the simplicity of the principle of operation, such a water heater is very convenient to use, but requires a number of improvements. First of all, at the outlet of the chimney from the tank, you need to drill a through hole and insert a pin with a damper disc into it. At the same time, the disk does not have a rigid attachment to the hairpin, because the damper must be periodically disassembled to clean the chimney.
For maintenance and repair of the heater, it will need to be disconnected from the piping; therefore, it is recommended to install brass American connections on the threaded branch pipes of the tank. The lower branch pipe is connected directly to the water supply system through a stopcock. Also, in this place, you can make a drain outlet with a tap and a fitting for connecting a flexible hose. On the upper branch pipe, it is necessary to provide a free outlet with a ball valve for air suction when draining water from the tank. A standard safety group is installed behind the outlet – an overpressure relief valve for water heaters. Further behind the group, the shut-off valve is packed.
If the water heater is located outside, it will not be superfluous to provide thermal insulation for the tank. It is easy enough to make it with ordinary basalt wool. A wide piece of steel reinforcing mesh is required, rolled into a ring with the formation of a gap from the tank walls of the order of 50–70 mm. Insulation is attached to the mesh with a thin wire, then the resulting casing is wrapped around the water heater and pulled together with wire clamps.
Installation and use rules
The wood-fired water heater must be installed on a solid, non-flammable base. The non-combustible substrate should protrude 15 cm to each side of the column profile and at least 50 cm from the side of the fire door. The column should be installed no closer than 15 cm to walls with a non-combustible coating and no closer than 50 cm to a combustible finish.
Ignition of titanium is only possible in a fully filled state. In this case, an air pocket is formed in the part of the tank located above the hot water intake pipe, which acts as a damper in case of liquid boiling. The procedure for preparing the tank for work is as follows:
- The furnace is fired up.
- The ash-pan door is kept open until the flame covers the entire volume of fuel.
- After ignition of the fuel, the ash pan closes. The damper regulates the air supply so that the outlet chimney is only perceptibly warm.
- If a characteristic noise of boiling water appears in the tank, the blower flap is closed completely.
- After complete combustion of the fuel, the chimney flap is closed.