Efficiency and selection criteria for long burning coal-fired boilers

Winter is approaching, and keeping our houses warm and comfortable takes precedence. For many, particularly those who live in places with limited access to electricity or natural gas, coal-fired boilers provide an effective and dependable solution. For many years, these boilers have been a mainstay in home heating, offering consistent warmth even during the coldest months.

But not all coal-fired boilers are made equal, and choosing the best one for your house can have a big impact on its efficiency and level of comfort. The capacity of long-burning coal-fired boilers to maintain heat output over extended periods of time has made them more popular and less dependent on frequent maintenance and refueling.

For homeowners wishing to make an investment in dependable heating solutions, it is imperative that they comprehend the critical components that contribute to the efficiency of long-burning coal combustion boilers. Numerous factors, ranging from fuel quality to design features, are critical in determining how well these heating systems operate.

This post will examine the many facets of long-burning coal-fired boilers, focusing on the characteristics that make them effective options for insulation and heating in homes. Learning about the efficiency and selection criteria of these boilers can help you make well-informed decisions that are tailored to your unique needs, whether you’re thinking about replacing your current heating system or looking into other options for your new house.

In the realm of heating and insulating your home, selecting the right long-burning coal-fired boiler is crucial for efficiency and cost-effectiveness. These boilers are designed to burn coal slowly, releasing heat over an extended period, which can significantly reduce fuel consumption and maintenance costs. When choosing a long-burning coal-fired boiler, factors like size, efficiency ratings, fuel type compatibility, and environmental impact should be considered. Investing in a high-quality, properly sized boiler that matches your heating needs can lead to long-term savings and optimal performance while minimizing environmental impact. By understanding the selection criteria and aiming for efficiency, homeowners can ensure warmth and comfort in their homes without breaking the bank or harming the environment.

What are long-burning coal boilers for private homes

A long-burning coal boiler is a contemporary heating appliance that uses specific solid fuels, mostly anthracite, coal briquettes, hard and brown coal, to produce heat energy and subsequently heat the coolant.

Citation. The term "long burning" actually refers to any boiler that is able to continue producing intense heat for an extended amount of time. For example, a boiler that burns on a single fuel charge for a day receives this status; if it burns for two days or longer, it maintains this status going forward.

Application and efficiency

Solid fuel boilers are used everywhere because they don’t require planning for construction projects. They can be used to create new heating systems or update pre-existing ones in homes, businesses, and other settings.

Coal-fired boilers do not require network connectivity, making them perfect for residential buildings in non-gasified regions. Under these circumstances, they reach their maximum potential and can be used to their greatest advantage. к. They can be modified to prepare and heat water if needed.

Although coal-fired long-burning boilers have an efficiency of 80–87% (compared to the industry average of 70–75%), they are not particularly inexpensive as a heating option.

Efficiency comparison of long-burning coal boilers (tabular data):

Basic resource Heat of combustion, mJ (kW)/kg (m 3 ) Price of fuel, rubles./t (m 3 , kW) EFFICIENCY Cost of kW of heat, rubles
hard coal 22,1 (6,2)-27,6 (7,7) 6000-7000 80-87 % 1,04-1,20
anthracite coal 28,3 (7,8)-31,1 (8,7) 8000-8500 80-87 % 1,12-1,28
natural gas 33,5 (9,3)-36,5(10) 5400-5700 90-95 % 0,60-0,64
chopped wood 11,2 (3,1)-14,3 (4,0) 1500-1800 60-65 % 0,69-0,80
electricity 3,6 (1) 2.5-4.3 (tariff) 98-99 % 2,55-4,34

Gas boilers are the most financially advantageous option, as the table illustrates. Gas is nearly entirely transformed into heat energy during combustion, so you are not responsible for the waste that is unavoidably produced when any solid fuel is burned.

Although firewood is less expensive than coal, heating with it still results in short-term losses because, at the same furnace volume, a full load of firewood burns for 8–48 hours (even with the increase in burning time), whereas coal can burn for 1–7 days.

We can therefore summarize the following: a long-burning coal boiler is a very good option for heating a small private house (100-150 m 2) in the absence of access to the main gas pipeline, especially since it will actually be much more economical than using electricity.

Device and principle of operation

Long-burning coal boilers function similarly to other solid fuel units in general, but they have the following features:

  • charging chamber – occupies almost all the internal space of the cylindrical body, which explains the increased capacity of the boiler;
  • furnace inlet – is necessarily located in the upper third of the stoking chamber, and the door itself can be located both vertically and horizontally;
  • air chamber – is also a recuperator, because of which the air in it is heated and enters the combustion zone already hot;
  • movable distributor – is a flat metal "pancake" necessary for metering air on the combustion surface of the fuel;
  • telescopic duct – looks like a dynamically extending tube, which unites the air chamber and the distributor;
  • ash pan – is placed as standard in the lower part of the boiler drum, but it does not play the role of an under-blow as in conventional boilers, so it must be hermetically closed;
  • chimney channel – has a "broken" (knee) shape, so the smoke passing through it accumulates heat better and is discharged into the chimney already cooled down;
  • heat exchanger – "water jacket" is built into the boiler body, it (unlike the coil) around the entire perimeter surrounds the combustion chamber and chimney channel.

Citation. Long-burning pyrolysis boilers are designed with a secondary chamber that can "afterburn" glowing exhaust (flue) gases. It is positioned either throughout the entire casing or in the upper portion of the primary combustion chamber. These coal-fired boilers can achieve efficiency gains of 90–95%.

Although it might initially appear that increasing the stoking chamber allows for a prolonged period of continuous operation, this is not entirely accurate.

These boilers work on the principle of "upper combustion," which is accomplished by forcing air through a duct from above with the aid of forced flow injection, rather than from below through a grate as in conventional boilers (direct combustion), which run on a natural draught.

In these circumstances, the combustion process becomes completely controlled; it only occurs in the air supply zone and essentially has no effect on the fuel’s bulk. The process of combustion is actually reduced to layer-by-layer smoldering (without flame), which transfers heat more uniformly from the upper to the lower layers.

Boilers that can burn a single fuel deposit for up to seven days

Reviews of household long-burning coal-fired boilers: advantages and disadvantages

It is best to avoid making mistakes in this situation because installing the heating system requires a lot of labor and is expensive. For this reason, it’s critical to weigh the advantages and disadvantages of long-burning boiler technology in advance, paying close attention to both manufacturer claims and actual owners’ evaluations.

Benefits and drawbacks of long-burning coal boilers

Advantages Disadvantages
saving resources – coal consumption per month is 20-30% lower than in conventional boilers impossibility of refueling – you have to wait for the fuel to burn out completely
autonomy – most models do not need access to electricity Continuity of the process – even after stopping work, smoldering will continue
easy maintenance – cleaning is less frequent and takes less time allocation of the boiler room – the unit should be installed in a separate room
temperature stability – constant control excludes overheating of the system large dimensions – both the boiler and the hopper (optional) takes up a lot of space
environmental protection – no smoke, coal dust, etc. accumulate in the room. д. low working pressure – maximum 1.6-1.8 bar (traditional 3-4 bar)
reliability – the simple structure of the boiler guarantees protection from frequent breakdowns high price – the boiler itself is 1.5-2 times more expensive than a conventional one + additional. equipment

The installation of the long-burning boiler pays for itself after five to six years, as the high cost is gradually offset by the coal savings.

Which one to choose: details about the characteristics that are worth paying attention to

The first consideration when selecting a long-burning coal boiler should be the heated room’s features (heat loss, area, installation capabilities, region), t. к. If something goes wrong, all of the piping will need to be replaced in addition to the equipment, which will take more time and money.

It will be wise to research the various types of devices available and comprehend the factors that determine their cost in advance.

Material of the primary heat exchanger (housing)

First and foremost, the material used to make the primary heat exchanger affects the system’s dependability as well as the boiler’s longevity and maintainability:

  • steel – well withstands temperature fluctuations, but is prone to corrosion;
  • cast iron – is durable (service life not less than 25 years), cools down longer, continuing to heat the heat carrier, but poorly tolerates temperature and pressure fluctuations.

Damaged steel bodies with a thickness of 4 mm can be readily repaired by welding, but delicate cast iron needs to be replaced even if it cracks slightly.

Numerous producers merge the advantages of both metals, such as creating boilers with a cast iron combustion chamber housed in a steel casing.

Single-circuit or double-circuit

Long-burning coal boilers can distribute the heat produced to accomplish one or more tasks, depending on the number of circuits:

  • single-circuit – designed exclusively for space heating, it is connected directly to the radiators (radiators) and heats water only for them;
  • two-circuit – has an auxiliary heat exchanger, which is responsible for providing hot water supply and heating water for the warm floor system.

Citation. It is necessary to continuously adjust the flow heater’s output, which serves as a heat exchanger, to the water flow rate.

The benefit of using a coal boiler with a water circuit is seriously questioned because the intensity of combustion of solid fuel cannot be adjusted in real time. Furthermore, two heat exchangers cannot operate simultaneously, and frequent switching causes equipment wear and tear as well as unintentional breakdowns.

Connecting an indirect heating boiler to a single-circuit boiler, which functions as a traditional storage water heater, makes more sense.

Minimum required capacity and heated area

Make sure you choose the coal-fired long-burning boiler’s capacity correctly. This will benefit the contractor company handling the installation.

Nevertheless, you can use the following formula to approximate the amount on your own:

Q is equal to S × 100.

  • Q – the required power needed to heat the room (kW);
  • S – heated area (m²);
  • 100 – power rate per unit area (W/m²).

For instance, Q = 120×100= 12000 W ≈ 12 kW for a 120 m² house.

The output is listed by the manufacturer under the most calorific type of coal that is used as the primary fuel. It is advised to add a reserve of 10–20% to the obtained value, Q ≈ 14 kW, in order to prevent operating the equipment at its maximum capacity when using alternative fuels.

Methods for determining the boiler’s required power: Individual calculations, formulas, and correction factors


The efficiency factor lets you calculate how effectively energy resources are used in relation to the amount of useful heat the unit emits; the higher this indicator, the better. However, you must first consider whether the decision is rational.

The efficiency of long-burning boilers ranges from 80 to 87%. Although a difference of 1% to 2% won’t make a big difference in fuel consumption, "ideal" models are way too expensive, so if money is tight, you can afford a more affordable model by rounding down.

What kind and how of coal is best for firing a solid fuel boiler in a home?

Other important selection criteria

Other factors, the convenience of which depends on continued operation, should be considered when selecting a long-burning boiler:

  • the degree of automation – semi-automatic boilers are loaded manually, after which ignition and support of combustion goes automatically, and in automatic devices there is a hopper, which also automates and fuel supply;
  • energy dependence – automatic coal-fired long-burning boilers require constant connection to the power grid, and boilers with thermomechanical regulation can operate smoothly even without access to electricity;
  • volume of the stoking chamber – the size of the furnace must correspond to the capacity, the optimum is considered to be 3.3-5.1 liters / kW (for example, for a 25 kW boiler with a chamber of 110 liters it will be equal to 110/25 = 4.4 liters / kW, which is considered normal);
  • other types of fuel – almost all coal boilers can be heated with wood and pressed briquettes, but some models are even more universal, i.e. they can be fired with wood and briquettes. е. If desired, they can be equipped with a pellet burner or even a gas burner;
  • control and functionality – the equipment is equipped with a thermostat, weather-dependent automation, self-cleaning system and GSM-module, as well as safety elements (emergency switch, explosion valve, etc.).).

The final point warrants particular attention because inadequate emergency equipment is the primary cause of breakdowns.

The best known manufacturers and models: characteristics and prices

Stropuva S15U

The 15 kW Stropuva (Stropuva) S15U universal boiler is a shaft-type boiler that can operate with wood, pellets, and briquettes of any kind in addition to coal. Because of its bimetallic draught regulator, it doesn’t require a connection to the electrical grid. ideal for homes between 100 and 120 square meters in size.

81,500–99,770 rubles is the cost.

Russia-Lithuania, LLC "STROPUVA" (STROPUVA) is the manufacturing country.

Heiztechnik Q Alfa 15

The Heiztechnik Q Alfa 15 has a 15 kW output and is intended to heat a room that is between 110 and 130 m³. It burns briquettes, coal, shtyb, and different types of wood. Cast iron grates and a body composed of thick boiler steel (5 mm) set this Polish boiler apart and ensure a long service life of up to 20 years.

62 240–68 720 rubles in price.

Nation of productionHEIZTECHNIK Ltd., Poland.

Buderus Logano S181-15E

One of the best long-burning coal-fired boilers for heating a private home with an area of 120–140 m 2 is the Buderus Logano (Buderus Logano) S181-15E 15 kW boiler. In order for the device to function for three to five days straight, the basic configuration consists of sensors for the temperature of the gas and water as well as a large hopper (240 liters).

Cost range: 250,640–218,000 rubles.

Germany-based LLC "BOSCH" (BOSCH THERMOTECHNIKA) is the manufacturer.


With a 60 kW capacity, the highly efficient domestic NEDELKA KO-60 model can heat a 200–250 m 2 home for two to four days with a single coal load. The boiler’s microprocessor unit is not susceptible to power outages, and when it is disconnected, it fades out gradually over the course of six to twelve hours.

$150,900–130,500 rubles in price.

Manufacturer: LLC "TRIAI," Russia (G. Kemerovo).


The 11 kW TIS (TIS) PRO 11 is a small unit that is ideal for heating an 80-100 m 2 private home, cottage, or summer house. You have the option of either automatic (using a mechanical thermoregulator) or manual (using a bolt on the door) air supply regulation.

Price range: 64-67 200 rubles.

Manufacturing nation: Belarus; producer: BelComin LLC TIS Group (TIS Group).


With a large 320-liter stoking chamber, the energy-independent LIEPSNELE (LIEPSNELE) L20U (20 kW) boiler is perfect for a 150–180 m 2 home. It can sustain the combustion of a single charge for up to 6-7 days. It can be heated using coal, wood, sawdust, shavings, pellets, and even peat, making it essentially "omnivorous."

85,400–90,560 rubles in price.

Lithuania is the manufacturing nation for VAKARO RASA Ltd.

How to stoke so that the coal burns as long as possible

The quality of the coal itself and the availability of the regulating automatics are the two main factors influencing the coal-fired long-ignition boiler furnace’s accuracy.

What coal is better to use

Coal of any fraction can be used in manual boilers. The use of raw fuel can cause the accumulation of excess moisture in the chimney and the formation of condensate, a black, drafty liquid with a tar smell. However, it should be noted that the temperature of gases in the chimney during prolonged combustion is much lower than during direct combustion. Consequently, coal (or any other solid fuel) should have a relative humidity of no more than 15-20%.

Aid. Equipment with an automatic fuel delivery feature is more fraction-sensitive, as it was initially intended for standard 5–25 mm. Furthermore, low-sintered (type 31 or 32) and low-ash (up to 15%) coal should be used to stoke it in order to prevent the accumulation of needless "garbage" and decreased efficiency.

Correct firebox

The following plan is used to operate a long-burning boiler furnace:

  1. Laying the fuel – the distributor is raised to its original position so that it is just above the loading door, and all the coal is immediately poured in.
  2. Burning – dry wood chips and paper are placed on top of the coal, after which they are set on fire and burned with the top door open and the air duct closed.
  3. Burning – when the temperature in the heat exchanger reaches 50-60 °C, the door is tightly closed, then the regulator of the telescopic air duct is opened.
  4. Temperature regulation – the boiler automatically enters the optimal mode, but if necessary, the temperature is corrected by the air duct flap.

After the full combustion cycle is finished, the sintered coal fragments must be taken out of the loading chamber, the ash pan must be cleaned, and fresh fuel must be added.

Prices: summary table

Long-burning coal boiler price rating (table):

Model of long burning coal boiler Cost, rub.
Stropuva S15U 85 400-90 560
Heiztechnik Q Alfa 15 62 240-68 720
Buderus Logano S181-15E 218 000-250 640
NEDELKA KO-60 115 900-130 500
TIS PRO 11 64 100-67 200
LIEPSNELE L20U 81 500-99 770
VIADRUS Hercules (Viadrus Hercules) U22D 126 600 -128 530
Galmet CARBO 21 103 890-116 750
Criteria Efficiency
Heat Output High heat output for longer periods
Fuel Efficiency Ability to burn coal efficiently, minimizing waste
Combustion Control Efficient control mechanisms for adjusting combustion rate
Insulation Well-insulated to retain heat and maximize efficiency

Selecting a coal-fired boiler with a long burn time is a choice that needs to be carefully thought through. Compared to conventional models, these boilers have the benefit of longer burn times, which means they can produce consistent heat for longer periods of time. However, when choosing the best boiler for your house, efficiency is crucial.

The energy efficiency rating of the boiler is an important consideration. High efficiency models will produce more heat with less coal consumption, so look for those. This lowers emissions, which lessens the impact on the environment while also cutting fuel costs.

When selecting a boiler, take your home’s layout and size into account. An appropriately sized boiler guarantees best efficiency and minimum energy use. Larger spaces may be difficult for smaller boilers to heat evenly, resulting in inefficiency. However, large boilers can waste fuel and frequently cycle on and off, which shortens their lifespan and efficiency.

When contrasting various boiler models, consider extra features that can improve convenience and efficiency. Operation can be streamlined and performance can be enhanced with features like ash removal mechanisms, automatic ignition systems, and programmable thermostats.

Investing in appropriate insulation and upkeep can help your coal-fired boiler operate at peak efficiency. Homes with adequate insulation are better at retaining heat, which eases the boiler’s workload and uses less energy. Frequent upkeep, such as cleaning and servicing, guarantees peak performance and increases the boiler’s lifespan.

In conclusion, choosing a long-burning coal-fired boiler that is efficient requires taking into account a number of variables, including size, extra features, insulation, and upkeep. You can have dependable heat while lowering fuel expenses and your home’s environmental effect by selecting the best boiler for your needs and putting in place the necessary insulation and maintenance procedures.

What type of heating you would like to have in your home?
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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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