The cheapest, most reliable and accessible heating method in our country is heating with solid fuel boilers (hereinafter SF boilers). This article covers the main types of such devices and maintenance features that can significantly extend the boiler's uninterrupted operation period.
Main types of solid fuel heating boilers
Conventional solid fuel boilers, in terms of internal design, resemble a stove: fuel is loaded and ignited, its combustion heats a steel or cast iron heat exchanger, which transfers heat to the system through pipes, thereby heating the indoor air. This type of boiler can be either one of the most budget-friendly or one of the most expensive, due to the large number of convenience features. They can be equipped with mechanical or electronic controls.
If the control is mechanical, such a boiler can be completely energy-independent; electronic control units require a mains connection, but their use makes operation much more convenient and precise. The price of such an SF boiler is difficult to state – it all depends on the technical specifications, efficiency indicators, and materials.
Pellet boilers get their name from the main fuel they use – pellet granules. This type of solid fuel heating boiler is one of the most expensive (due to the use of various automation systems). Such models are mostly installed at industrial facilities (they come with a fuel hopper and a fuel supply system that allow for less frequent pellet loading). The system can also handle ash removal, chamber cleaning, scheduled startup, or remote control via mobile devices. Each manufacturer offers a wide range of automation systems for pellet boilers.
Pyrolysis boilers are one of the most cost-effective options among SF boilers (average price compared to other types, but efficiency is 1.5–2 times higher). The device is designed so that when the wood ignites, the air supply to the combustion chamber is cut off, causing the wood to smolder and release gas, which mixes with fine ash particles to form a gaseous mixture. Using forced draft fans, the mixture is directed into the combustion chamber, where it is reignited. The chamber reaches a temperature of 1100–1250 degrees Celsius, which contributes to rapid system heating and extended operation on a single load of firewood. On one cubic meter of wood, a pyrolysis boiler will operate 1.5–2 times longer than a conventional SF boiler of the same power.
Universal boilers are advantageous because they run on all types of solid fuel. They are in high demand at sawmills, woodworking enterprises, and other companies whose activities generate a lot of wood or other combustible agricultural waste. In most cases, these boilers are very undemanding and operate on almost anything that burns, but many waste types may simply not provide the necessary temperature inside the combustion chamber, and the use of low-quality fuel can lead to problems with the heat exchanger, such as soot formation.
Maintenance of solid fuel boilers and off-season preservation
For the boiler to last a long time, it requires periodic maintenance and, of course, proper use. Each manufacturer has its own maintenance recommendations; below we list general rules that, if followed, extend service life, ensure uninterrupted operation, and eliminate the need to contact a service company.
Preservation is a term referring to preparing a solid fuel boiler for the off-season period when it will remain idle for a long time.
Periodically (once every 1-2 months), completely shut down the device, allow it to cool, and thoroughly clean the internal walls of soot and carbon deposits. The same actions should be performed before preserving the device for the warm period. If you leave the soot and carbon deposits from spring and only address them in autumn before startup, there is a risk of not being able to scrape them off at all, which is detrimental to further use. During preservation, after cleaning, it is recommended to lubricate the internal walls with machine oil; this prevents corrosion from spreading on the steel. It is also useful to lubricate the sealing cord with graphite grease. The figures show what should be avoided; the pipes in the top figure lose about 30-40% of energy due to the thickness of soot and rust.
Often, owners of such heating systems complain that over time the boilers no longer reach the required temperature in the system; this may be due to several factors:
• using low-quality firewood (they simply do not provide the necessary temperature when burned);
• soot and carbon deposits on the heat exchanger and other elements, not removed in time;
• clogged nozzle opening;
• loss of tightness;
• wear of the sealing cord.
In pyrolysis boilers, at the end of the season, attention should be paid to the fireclay nozzle. It is a consumable item and is replaced on average once per heating season. With active use throughout the heating season, the nozzle walls burn out, and the flame opening becomes smaller, causing the heat exchanger to take longer to heat up.
Also, in pyrolysis models, it is recommended to periodically check whether there are any foreign objects on the nozzle (bad firewood may contain nails, or a foreign object may accidentally get in during loading). These objects all accumulate near the nozzle opening, and if they are nails, at first they will simply interfere with the flame passage, but over time they will melt, forming a plate on the nozzle. As a result, there is a large loss of energy, cold pipes and low efficiency, which can ultimately lead to breakdown.
Pellet boilers may have various systems for cleaning and ash removal, but you should not rely on them completely; at least once every 2 months, check whether there is soot or residual ash or fuel on the fuel burner. If there are automation systems, before preservation, lubricate all moving mechanisms.
Following these rules will help increase the service life of a solid fuel boiler and avoid problems during the first startups of the season.
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