How to choose the best solid fuel boiler?


Despite the fact that gas heat­ing is more cost-effec­tive today, in some cas­es a sol­id fuel boil­er or an elec­tric heater is used to heat indus­tri­al build­ings, pri­vate res­i­den­tial build­ings.

The type of heater, a clear under­stand­ing of the tech­no­log­i­cal needs for heat­ing equip­ment, will help you decide which one is suit­able for a giv­en sit­u­a­tion. The option with elec­tric­i­ty is expen­sive, imprac­ti­cal in terms of eco­nom­ic para­me­ters when heat­ing large areas is required. Let’s focus on sol­id fuel boil­ers. Fire­wood, coal, wood­work­ing waste, every­thing that has con­stant access to it, can go into the fur­nace of sol­id fuel boil­ers. The bet­ter to heat a sol­id fuel boil­er, you decide. The pos­si­bil­i­ties of sup­ply­ing fuel to the heat­ing sys­tem are pure­ly indi­vid­ual. We will deal with the sit­u­a­tion when it comes to sol­id fuel boil­ers, what type, what mod­el of equip­ment to give pref­er­ence to.

Which boiler is better — evaluation criteria

Which boil­er is bet­ter or worse, it will become clear already dur­ing the oper­a­tion of the heat­ing equip­ment. The only way to avoid fur­ther dis­ap­point­ment, to elim­i­nate addi­tion­al costs, is to cor­rect­ly assess the exist­ing options for inde­pen­dent heat­ing on sol­id fuels. What are the eval­u­a­tion cri­te­ria: bet­ter or worse for sol­id fuel units?

For heat­ing tech­nol­o­gy, the fol­low­ing cri­te­ria are impor­tant:

  • pow­er of the pro­posed mod­els of sol­id fuel boil­ers;
  • avail­abil­i­ty of fuel, its cost;
  • tech­no­log­i­cal para­me­ters of heat­ing boil­ers;
  • safe­ty of heat­ing equip­ment;
  • equip­ment with auto­mat­ic con­trol sys­tems;
  • the pos­si­bil­i­ty of switch­ing to gas heat­ing.

Require­ments for the desired pow­er, types of fuel deter­mine the tech­no­log­i­cal para­me­ters of the units. These include dimen­sions, num­ber of com­bus­tion cham­bers, prin­ci­ple of oper­a­tion, method of load­ing fuel.

Per­for­mance, per­for­mance, safe­ty are also key aspects, rely­ing on which you can say for sure — this heat­ing boil­er is bet­ter than oth­er mod­els.

How to calculate the optimal power parameters

As in the sit­u­a­tion with gas boil­ers, the method for cal­cu­lat­ing the pow­er of sol­id fuel boil­ers is car­ried out accord­ing to the same prin­ci­ple — 1 kW is required for heat­ing 10 m2 area of ​​the inte­ri­or. The height of the ceil­ings is also tak­en based on the aver­age val­ue — 3 m.

For exam­ple: for heat­ing a res­i­den­tial build­ing or a small indus­tri­al build­ing with an area of ​​150 m2 a sol­id fuel boil­er with a capac­i­ty of 15 kW is required. Why? 150 / 10 = 15.

Some­times the pow­er of the boil­er is cal­cu­lat­ed tak­ing into account the inter­nal vol­ume of the room. Here it is already nec­es­sary to take into account such a fac­tor as the ther­mal insu­la­tion of the room. To cal­cu­late a well-insu­lat­ed and insu­lat­ed room, a fac­tor of 40 is tak­en. A build­ing that is not suf­fi­cient­ly insu­lat­ed cor­re­sponds to a fac­tor of 60. For a build­ing with an area of ​​150 m2 with a ceil­ing height of 2.5 m. we make cal­cu­la­tions

For exam­ple:

150 x 2.5 x 40 u003d 15000W (15 kW) — equip­ment pow­er that is opti­mal for heat­ing a build­ing with good ther­mal insu­la­tion.

150 x 2.5 x 60 u003d 22500W (22.5 kW) — the opti­mal pow­er of the unit for heat­ing a room with poor ther­mal insu­la­tion.

Impor­tant! Up to 50% of the design capac­i­ty must be added to the cal­cu­lat­ed capac­i­ty of the equip­ment used for hot water sup­ply. Indi­rect­ly heat­ing water in a boil­er or heat­ing a heat exchang­er will require sig­nif­i­cant addi­tion­al pow­er and more wood or coal.

For res­i­den­tial premis­es, the issue of pro­vid­ing hot water sup­ply is espe­cial­ly rel­e­vant. In this sit­u­a­tion, an impor­tant ques­tion should be resolved, which type is prefer­able for you and how much it will be required for the nor­mal oper­a­tion of the indi­vid­ual heat­ing sys­tem.

What fuel to use

Today, a vari­ety of types of fuel are used for the oper­a­tion of sol­id fuel boil­ers:

  • brown coal;
  • coke;
  • coal;
  • peat;
  • fire­wood, wood­work­ing prod­ucts.

It is mis­lead­ing to assume that the pow­er of the heater, regard­less of whether it is fired with wood, coal or pel­lets, will be the same. Each fuel has its own caloric para­me­ters, there­fore, in each case, the pow­er of the appa­ra­tus and the vol­ume of load­ing of the com­bus­tion cham­ber may dif­fer.

For ref­er­ence: less high-calo­rie fuel can lead to a drop in the pow­er of a sol­id fuel unit by 20–30% of the design data. An unpre­pared fuel resource (high humid­i­ty) leads to even more notice­able pow­er loss­es of heat­ing equip­ment.

In the tech­ni­cal doc­u­men­ta­tion for the heat­ing device, man­u­fac­tur­ers usu­al­ly indi­cate the rec­om­mend­ed type of fuel and alter­na­tives. The main type of com­bustible mate­r­i­al will increase the dura­tion of the boil­er equip­ment with­out fail­ures. The best com­bustible mate­r­i­al may have lit­tle effect if used in this type of equip­ment as an addi­tion­al fuel.

For an opti­mal assess­ment of the qual­i­ty of heat­ing equip­ment, it is nec­es­sary not only to take into account the require­ments for the pow­er of the heater and the tech­no­log­i­cal para­me­ters of the fuel resource, but also to care­ful­ly study the vari­eties of exist­ing sol­id fuel heaters.

What types of solid fuel boilers are on the market today

The deci­sion on which sol­id fuel boil­er is bet­ter depends on a num­ber of fac­tors that are deci­sive in each indi­vid­ual case. Depend­ing on the select­ed fuel, the pow­er of the equip­ment and the type of heat­ing unit on sol­id com­bustible mate­r­i­al depend.

Today, sol­id fuel boil­ers for heat­ing of the fol­low­ing types are pre­sent­ed on the domes­tic mar­ket:

  • tra­di­tion­al (steel or cast iron) heat­ing devices;
  • pyrol­y­sis (gas gen­er­at­ing) boil­ers;
  • heat­ing sol­id fuel devices of long burn­ing;
  • pel­let heat­ing units.

All devices have their own spe­cif­ic advan­tages and dis­ad­van­tages, there­fore, to eval­u­ate the most appro­pri­ate type of equip­ment, it is nec­es­sary to take into account a num­ber of nuances.

With tra­di­tion­al mod­els of sol­id fuel vehi­cles, there are no par­tic­u­lar dif­fi­cul­ties. Devices of this type resem­ble an oven. And the method of sup­ply­ing fuel, and the design of the fur­nace itself, and the device of the chim­ney, all these ele­ments are sim­i­lar to the device of a con­ven­tion­al fur­nace. For such a heat­ing appa­ra­tus, coal or wood is usu­al­ly used. Devices are tra­di­tion­al­ly pro­duced in two ver­sions — steel and cast iron.

If you want to have a sim­ple and reli­able heat­ing device at home, tra­di­tion­al mod­els are just for you. Here you will not find either com­plex automa­tion or elec­tron­ic devices, which usu­al­ly affect the cost of heat­ing equip­ment and often cause heat­ing equip­ment to fail. Heat­ing appli­ances of the tra­di­tion­al type are equipped with a mechan­i­cal heat­ing tem­per­a­ture con­troller. The whole sys­tem is designed for long and trou­ble-free oper­a­tion.

Which boil­er is bet­ter if you have a lim­it­ed amount of fuel, but it is desir­able to have pow­er­ful equip­ment with high effi­cien­cy. The answer is sim­ple, get a pyrol­y­sis type appa­ra­tus. Using a sim­i­lar heater, with the same vol­ume of com­bustible mate­r­i­al as for tra­di­tion­al units, you can get a sig­nif­i­cant increase in ther­mal ener­gy.

In pyrol­y­sis boil­ers, the whole process is divid­ed into three phas­es: fuel dry­ing, syn­the­sis of com­bustible mate­ri­als into a gaseous state, com­bus­tion of a gaseous sub­stance. Fuel is 85% syn­the­sized, giv­ing an air-gas com­bustible mix­ture. The result of com­bus­tion is a huge amount of ther­mal ener­gy. The oper­a­tion of the fan pro­vides a con­stant sup­ply of fresh air, there­by reg­u­lat­ing the direc­tion of the flame. More­over, pyrol­y­sis-type devices are equipped with a sec­ondary, heat­ed air sup­ply sys­tem, which increas­es the inten­si­ty of com­bus­tion.

A good heater that will be fired with wood or coal is a long-burn­ing boil­er. The main dif­fer­ence between this heat­ing equip­ment and oth­er designs is that these mod­els are not whim­si­cal in main­te­nance. The high effi­cien­cy of this equip­ment is achieved due to a fun­da­men­tal­ly dif­fer­ent way of burn­ing com­bustible mate­r­i­al. The com­bus­tion cham­ber is devoid of an open flame, the ther­mal effect is achieved due to the smol­der­ing of the fuel lay­er.

The fig­ure shows a dia­gram of the arrange­ment of equip­ment using wood bri­quettes for long-term burn­ing.

In con­clu­sion, a few words can be said about such a type of heat­ing device as a pel­let boil­er. Wood pel­lets are used as fuel. For the cat­e­go­ry of con­sumers who live in areas rich in for­est resources and have wood­work­ing prod­ucts con­stant­ly at hand, pel­let heat­ing units are an ide­al option for heat­ing equip­ment.

Mod­els of this type are equipped with a mech­a­nism for auto­mat­i­cal­ly sup­ply­ing com­bustible mate­r­i­al to the com­bus­tion cham­ber, mak­ing them com­pet­i­tive prod­ucts.

Usable volume of the loading chamber and boiler power

What you need to pay atten­tion to when eval­u­at­ing a sol­id fuel boil­er for heat­ing a house is what is the ratio of the use­ful vol­ume of the load­ing cham­ber and pow­er for the units. For dif­fer­ent heat­ing devices, this ratio varies. The best sol­id fuel boil­ers have the opti­mal ratio in this case. The high­er the num­ber, the bet­ter for you.

On a note: usable vol­ume is the amount of fuel that can be put into the com­bus­tion cham­ber at one time for the oper­a­tion of the heat­ing unit. The max­i­mum val­ues ​​of use­ful vol­ume are mod­els of fuel appa­ra­tus­es with top load­ing. Such devices, with front load­ing, also have high use­ful vol­ume val­ues. How­ev­er, load­ing the com­bus­tion cham­ber with com­bustible mate­r­i­al of such a device will require more time and effort.

For tra­di­tion­al mod­els of sol­id fuel equip­ment, the table gives an idea of ​​the ratio of usable vol­ume to pow­er

Steel boil­ers 26l / 13kW = 2 l/kW
Steel boil­ers 61l / 32kW = 1.9
Cast iron boil­ers 21l / 12 kW = 1.75
Cast iron boil­ers 73l / 35 kW = 2

With pyrol­y­sis units, the sit­u­a­tion looks dif­fer­ent: one refu­el­ing is enough to get heat in 6–10 hours of burn­ing. The effi­cien­cy of the heat­ing device is 90%. The main and dis­tinc­tive fea­ture of this type of mech­a­nism is two com­bus­tion cham­bers. The load­ing cham­ber has a large size and vol­ume, when com­pared with the fur­nace of tra­di­tion­al types of devices.

The first cham­ber is used for pri­ma­ry com­bus­tion. It is here that due to the lack of oxy­gen, pyrol­y­sis occurs — a process that gen­er­ates com­bustible mate­r­i­al into a gaseous state. In the sec­ond cham­ber, the after­burn­ing of the syn­the­sized gaseous fuel is already tak­ing place. This tech­nique is designed to be used for kin­dling hard­wood. The table shows the data of pyrol­y­sis appa­ra­tus­es.

86l / 25 kW = 3.44
138l / 36 kW = 3.8
110l / 25 kW = 4.4
294l / 60 kW = 4.9

The next type is pel­let sol­id fuel heaters. Here, fuel is loaded mechan­i­cal­ly. The burn­ing time direct­ly depends on the vol­ume of the load­ing cham­ber. Some mod­els are equipped with pneu­mat­ic fuel sup­ply devices. The ratio for boil­ers of this type is shown in the table below.

725l / 24kW = 30l/kW
725l / 45 kW = 16 l/kW

A sep­a­rate place in this list is occu­pied by long-burn­ing heat­ing devices. The burn­ing time in the com­bus­tion cham­ber from one load in such units is sig­nif­i­cant, reach­ing 12 hours, 24 or 48 hours. The pecu­liar­i­ty of the equip­ment is that com­bus­tion in the com­bus­tion cham­ber does not occur from the bot­tom up, but, on the con­trary, from top to bot­tom. As a result, fire­wood, coke or coal smol­der. The para­me­ters of the ratio of usable vol­ume to pow­er for devices of this type are giv­en in the table

200l / 10 kW = 20
350l / 20 kW = 17.5
500l / 40 kW = 12.5


To deter­mine the best mod­el of a long-burn­ing sol­id fuel boil­er means to rad­i­cal­ly solve the issue of orga­niz­ing autonomous heat­ing of indus­tri­al build­ings and res­i­den­tial build­ings. Although each sit­u­a­tion requires an indi­vid­ual approach to assess­ing the capa­bil­i­ties of the heat­ing unit. The very best heat­ing devices can per­form hor­ri­bly when sup­plied with fuel that does not match the tech­no­log­i­cal data of the equip­ment. Con­verse­ly, sim­ple mod­els can be effec­tive and reli­able.

How well the unit will work, time will tell. Only a com­pe­tent design and ther­mal cal­cu­la­tions can guar­an­tee the sat­is­fac­to­ry oper­a­tion of any heat­ing equip­ment.


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