From theory to practice! Heating the boiler with coal correctly

When it comes to heating our homes, efficiency and effectiveness are paramount. Whether you"re aiming to combat the chill of winter or simply keep your space cozy year-round, choosing the right heating method is crucial. One traditional but still widely used method is coal heating, particularly via a boiler system. While coal heating might seem like a relic of the past, it remains a viable option for many households, offering steady warmth and cost-effectiveness when done correctly.

But heating your boiler with coal requires more than just throwing some lumps into the fire. To guarantee efficiency and safety, a mix of skills, equipment, and knowledge is needed. This article explores the usefulness of using coal to heat your boiler and provides a comprehensive guide to help you move from theory to effective practice.

It is imperative to grasp the foundational principles of coal combustion prior to delving into the details. Burning coal releases energy since it is a fossil fuel made of remnants of ancient plants. This energy is used to heat the water in the boiler, creating steam that can be used to heat your entire house. Although the procedure might appear simple, following best practices and paying close attention to details are necessary to get the best results.

Make sure you have the appropriate coal and equipment before you even consider turning on your boiler. Utilizing the incorrect kind of coal can result in inefficiency, excessive smoke, and even safety risks because not all coal is made equal. Your boiler must also be in good operating order, with all of its parts operating as intended. Maintaining optimal performance and preventing malfunctions requires routine inspections and maintenance.

How and what kind of coal is better to fire a solid fuel boiler

Several grades of hard coal, brown coal, and charcoal are typically available for domestic use. However, you should carefully read the solid fuel boiler’s instruction manual before filling it with fresh fuel because it contains the manufacturer’s recommended fuel grades.

The documentation outlines the best coal brands to use in heating boilers, both residential and commercial. It is a fact that boilers undergo testing and certification upon completion of the manufacturing process to ensure compatibility with various fuel types. The equipment’s ability to function normally may be compromised if the heat capacity of a particular group of coal is higher than the heat capacity of the brands that the manufacturer recommends.

Making the right fuel selection is one of the requirements for heating a boiler with coal effectively. Manufacturers advise paying attention to factors like dust, ash content, calorific values, and the quantity of harmful impurities, in addition to defining the type and brand. The fuel passport contains this information, but it’s still important to understand the specific characteristics of each brand.

Hard coal

This type of coal is the most common. In most grades, the calorific value is about 5500-6000 kcal/kg on average. This indicator is associated with a high content of hydrocarbon, this substance makes up about 75% of the mass. During combustion, hard coal forms from 2 to 5% of ash, but it should be said that this applies to a sorted product that has been cleaned from rock. Grades of hard coal are divided by fraction size, mass and calorific value. There is also a gradation according to how fast the fuel burns. Almost all brands of hard coal are suitable for firing universal solid fuel boilers of the classical type. But for devices of long combustion such fuel is not suitable, it has a fairly high temperature index, which adversely affects the equipment.

Brown coal

The majority of uses for this fuel are in mining regions. Traditionally, brown coal has been primarily used for domestic use and has not found widespread application. Brown coal has a lower calorific value than hard coal; it is between 3000 and 3200 kcal/kg, which is nearly twice as low as the lowest grade of hard coal. This product is unique in that it produces more ash when it burns. In residential heating installations, brown coal and its briquettes with a mass fraction of moisture of roughly 50% are utilized.


Anthracite is one of the best types of coal for boiler combustion, so it should be the primary consideration when selecting a fuel with the highest calorific value. A calorific value of 9000 kcal/kg can be released at combustion, making it one of the highest indicators. Nevertheless, anthracite generates a significant amount of ash—up to 7%—and unburned coal—up to 5-7%—after burning.


The purpose of this kind of coal raw material is to be used in industrial facilities. Because of its unique structure and significant ash residue, many manufacturers do not advise using it in homes.

Coal processing products

It is challenging to categorize any kind of solid fuel derived from natural hydrocarbons conditionally these kinds of products, but it is equally challenging to overlook them. Coal briquettes and coke, two byproducts of hard coal processing, fall under this category.

The first kind of fuel is briquette fuel, which is produced at coal preparation facilities by pressing waste from coal recovery. In a nutshell, it’s the fine fraction of the sorted coal that remains after the main mass has been sifted out. This type of fuel is primarily utilized in industrial settings due to its high sulfur emissions during combustion and residue that frequently contains more ash than 10% of the original mass.

Since dust combustion technology is not included in solid fuel domestic boilers, pure coal dust is essentially never used in individual heating systems. The use of dust is justified in industrial production, power engineering with thermal generation, and even metallurgy; in the form of a water-dust mixture, it can cost-effectively replace pricey natural gas. However, this method is too expensive for small boilers designed to produce 7–15 kW of power.

The primary fuel used in blast furnaces to produce iron is coking coal, which is also successfully used at home. Indeed, it is important to keep in mind that the energy value ranges from 5.6 to 7.0 thousand kcal per kilogram. The average composition of the material is 8% ash, 3.2% to 4.2% volatiles, and 1% to 2% sulfur in coke. At least 87% of the material is made up of pure carbon.

Gas coal

Combustible coal is a common term used to describe this kind of coal. Coal belonging to this group is saturated with light flammable gases and has a maximum diameter of 4 cm, making up a very small fraction. This product is great for stoking because it ignites the majority of the main fuel’s coals quickly, starting the combustion process and raising the temperature of combustion to 400–600 degrees. However, because of its low calorific value and four to five times longer combustion time than anthracite or coke, it is unlikely to be used in a full-fledged furnace.


Charcoal was one of the most widely used charcoal products until recently. Although hard coal has replaced this type of coal in modern times, private homes still use it. It forms between 7000 and 8000 kcal/kg when burning, which is not too bad when using regular firewood. Two to two.8% of carbon is left over after 84% of the carbon has burned. Charcoal works particularly well in long-burning and pyrolysis-style solid fuel boilers.

How to fire a boiler from theory to practice

When firing coal, the best outcome is determined by how well every technological step of the firing process is executed, from loading firewood to refueling the furnace with primary fuel. How to melt the boiler will determine how successful you are. The truth is that when the temperature in the combustion hearth rises to 400–600 degrees, hard coal—such as anthracite or coke—enters the combustion process. This is just not possible to accomplish with paper, and a match or piece of paper won’t ignite solid fuel itself.

In the world of heating and insulation for homes, knowing how to properly heat your boiler with coal is key. Transitioning from theory to practice can be a game-changer. It"s not just about throwing coal into the boiler and hoping for the best; it"s about understanding the nuances of coal combustion, airflow, and temperature control. From selecting the right type of coal to mastering the art of adjusting dampers and vents, getting it right can mean greater efficiency, cost savings, and a warmer home. This article will guide you through the practical steps, tips, and best practices for effectively heating your boiler with coal, ensuring both comfort and sustainability for your household.

The process of ignition of solid fuel heating boiler

The method of lighting a solid fuel boiler and lighting a wood boiler use the same technology. Only a few subtleties are present. The first detail is that the lower portion of the furnace needs to have a special coal fuel grate installed. This grate’s function is to facilitate the coals’ mixing during combustion. It is constructed as a large cast iron casting with 1.5–2 cm separating the grates. This grate is vertically positioned in the furnace’s lower section, and a blower door with a slide valve controlling the oxygen supply closes it off.

The lower section is packed with paper, and then wood chips are added on top. Tinder and small logs are used in the next layer to start an active flame. Four or five large logs are stacked on top. The top layer is positioned to allow coal to be poured on top of it without causing fuel to leak into the blowhole.

Coniferous wood chips are used as kindling; they ignite fast, maintaining the fire’s heat and enabling the subsequent ignition of hardwood logs. Hardwoods such as oak, birch, and hornbeam are utilized as firewood because they generate the heat required to ignite coal.

Small fraction coal, or coal with a diameter of 3–4 cm, is used for the initial laying; gas coal or fuel oil are good choices in this situation.

It is crucial to keep in mind that kindling is made from dry wood. Using liquid fuel and combustible mixtures is never impossible. Pouring gasoline, biofuel, or diesel into the furnace increases the likelihood that it will seep into the cushion and possibly onto the ground. A fire in such a situation is unavoidable. Adding more crumpled paper to the bottom is preferable to adding at least a drop of gasoline.

It doesn’t matter if you use a lighter or a match to start the fire; what matters is that it spreads swiftly to cover the top logs and wood chips.

Main heating period

According to conventional wisdom, starting a coal boiler correctly involves multiple steps: initial ignition, basic combustion phase two, reaching stable combustion phase three, and lastly, fading out.

The main period of firing usually falls at the moment when the wood forms productive coals for backfilling the stone fuel. The moment when the first portion of fuel is poured in depends on how to properly fire the solid fuel boiler. In terms of time from the moment of the beginning of paper burning to the time when the logs of the main wood will be embraced by the flame usually takes about 4-5 minutes, but this is with a normal draught and an open damper blower. To check what is happening in the firebox, you can open the firebox door – when carefully opened, the firebox will light up with an even bright flame, it means that the moment has come for pouring the first portion of coal.

First, small fractions of coal (2-4 cm in diameter) are added to the firebox. At this point, one or two scoops or 0.5 to 1 kg of fuel will be required. Coal is poured through the fire door, ensuring that the layer covers the whole fire area uniformly. The door is shut immediately after pouring, and the blower door’s latch is slightly loosened to allow more oxygen to enter the furnace area.

It is worthwhile to check the furnace after ten to twelve minutes. This is sufficient time for the fuel to begin burning and the temperature to reach 400 degrees Celsius, producing a sufficient amount of heat. It is important to monitor the boiler’s thermometer readings during this time. If the temperature has suddenly increased and the coolant in the pipes and radiators has become more heated, it is time to add more fuel to the boiler.

According to the rules, how to properly fire the boiler with coal it is necessary to introduce from 3 to 5 kg of anthracite or medium-fraction coal. Coals should be of medium size 4-7 cm in diameter. As with fuel, the filling is done through the firebox door with a spatula or scoop. If possible, the coal is scattered over the whole area of the firebox, so that the layer is about 10-15 cm (however, much depends on the size of the firebox). After the furnace door is closed, the thermo regulator is set and the boiler is switched to the long burning mode, when it regulates the opening and closing of the oxygen supply valve by itself.

Stable combustion stage

Stable combustion lasts for roughly five to nine hours. Even fuel feeding into the furnace is the key to firing the boiler correctly during this time. Typically, if only ¼ of the fuel is used during the initial filling, the remaining fuel is split into three equal portions and burned steadily. To keep the furnace from slagging, the burning mass is stirred after anthracite is added through the blower grate.

End of burning

The third fuel feeding stage signals the end of combustion. The furnace is filled with the remaining coal. In addition, it is worthwhile to sprinkle ash from the ash pan on top to enhance the effect. As a result, the combustion process will take longer and incorporate more unburned coal particles.

Theory Practice
Choose the right coal type Opt for high-quality coal with low sulfur content
Ensure proper ventilation Provide adequate air intake for combustion
Control combustion rate Adjust airflow to maintain steady heat output
Clean the boiler regularly Remove ash buildup to prevent inefficiency

It takes a combination of theoretical knowledge and practical experience to become an expert at heating your boiler with coal. Understanding the basics of combustion, airflow, and coal types lays a solid foundation, as we’ve discussed throughout this article. The real magic, though, occurs when you put that knowledge into practice.

First and foremost, taking your time when choosing the proper coal for your boiler is essential. Different types of coal burn differently and release different amounts of heat. Selecting the right grade of coal will maximize productivity and reduce waste. Recall that high-quality coal produces high-quality heat.

After you’ve sorted the coal, it’s critical to become an expert at stoking the fire. Maintaining consistency is essential. Efficient heating requires a steady, even burn, regardless of whether you use an automatic stoker or the hand-fired method. Refrain from packing the firebox too full since this may smother the flames and cause incomplete combustion.

Don’t undervalue the significance of airflow, either. In order to maximize heat transfer to your boiler, proper ventilation guarantees that your coal burns evenly and cleanly. To ensure maximum airflow throughout your heating system and to prevent blockages, clean and inspect your chimney, flues, and vents on a regular basis.

Finally, keep in mind that improvement comes from practice. Don’t let early difficulties or failures depress you. It takes time and patience to become proficient at heating with coal, just like any other skill. Accept that you will be learning, pay attention to how your boiler behaves, and don’t be afraid to make changes as you go.

In conclusion, it is worthwhile to go from theory to practice when it comes to heating your boiler with coal. You can maximize efficiency and comfort in your home by maximizing the potential of your heating system by fusing theoretical knowledge with real-world experience.

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Sergey Ivanov

I like to help people create comfort and comfort in their homes. I share my experience and knowledge in articles so that you can make the right choice of a heating and insulation system for your home.

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