Draft regulator for solid fuel boilers: device and installation


For any boil­er equip­ment, the most impor­tant com­po­nent of suc­cess­ful oper­a­tion is the pres­ence of trac­tion. From the point of view of phys­i­cal process­es, this is a com­plex, het­ero­ge­neous phe­nom­e­non, which is due to the phys­i­cal state of sub­stances. Warm, heat­ed to a cer­tain tem­per­a­ture, gaseous sub­stances tend to rise up, while cold­er sub­stances, on the con­trary, are heav­ier and fall down. This prin­ci­ple under­lies the process of oper­a­tion of heat­ing tech­nol­o­gy.

Sol­id fuel boil­ers, where car­bon diox­ide super­heat­ed as a result of fuel com­bus­tion and volatile sol­id par­ti­cles rise up, fresh, cool air comes in their place. The force of thrust depends on how strong the gas exchange of hot mass­es and cold air is. The draft reg­u­la­tor for sol­id fuel boil­ers is pre­cise­ly designed to solve the prob­lem of the inten­si­ty of the mutu­al exchange of air mass­es, affect­ing the per­for­mance of the heat­ing unit. Let us con­sid­er in detail what a mechan­i­cal draft reg­u­la­tor is. We will find out what is his direct par­tic­i­pa­tion in the oper­a­tion of heat­ing equip­ment, how impor­tant is the instal­la­tion of this device for boil­ers.

Draft regulator — its importance for solid fuel boiler equipment

The oper­a­tion of a heat­ing device with an open and closed com­bus­tion cham­ber is 90% depen­dent on the state of draft in the heat­ing sys­tem. The more sta­ble the thrust para­me­ters, the bet­ter the heat­ing unit works. Under the action of draft in the com­bus­tion cham­ber, sol­id fuel burns bet­ter, com­bus­tion prod­ucts eas­i­ly escape through the chim­ney. With nor­mal thrust, the fuel burns more inten­sive­ly, heat exchange process­es improve, and the effi­cien­cy of boil­er equip­ment increas­es accord­ing­ly.


Despite the fact that today most of the mod­els of sol­id fuel heaters are equipped with automa­tion, mechan­i­cal con­trol and adjust­ment devices are still the most effi­cient and effec­tive. Ener­gy depen­dence is the most impor­tant draw­back of sol­id fuel boil­er automa­tion. There is no elec­tric­i­ty in the house, the bat­tery that feeds the UPS is dead, the boil­er becomes uncon­trol­lable. A device with a mechan­i­cal dri­ve, installed on the boil­er and adjust­ed in accor­dance with the set tem­per­a­ture para­me­ters of the boil­er, is able to ful­ly con­trol the inten­si­ty of com­bus­tion.

The main advan­tages that a mechan­i­cal draft ther­mo­stat has are as fol­lows:

  • the sim­plest design and reli­able oper­a­tion, unlike auto­mat­ic devices equipped with elec­tron­ics;
  • non-volatile (auto­mat­ic trac­tion con­trol requires unin­ter­rupt­ed pow­er sup­ply);
  • con­ve­nient and clear instal­la­tion of the device;
  • low cost.

The sim­ple design and prin­ci­ple of oper­a­tion allow such a device to be made by hand, installed and con­fig­ured. The mech­a­nism has a sci­en­tif­ic and tech­ni­cal name — a ther­mo­stat for a boil­er. To get the max­i­mum pos­si­ble effect from the exist­ing heat­ing unit, it is enough to cor­rect­ly install the ther­mo­stat. Sub­se­quent cal­i­bra­tion of the device is car­ried out in accor­dance with the main func­tions of the exhaust ven­ti­la­tion and the spec­i­fied tem­per­a­ture para­me­ters.

Impor­tant! Installing a draft reg­u­la­tor allows you to adjust the oper­a­tion of the entire heat­ing sys­tem depend­ing on the tech­no­log­i­cal and design fea­tures of the boil­er equip­ment, to com­pen­sate for the insuf­fi­cient­ly effi­cient oper­a­tion of the chim­ney and the qual­i­ty of the fuel.

Draft thermostat device

The ther­mo­stat is a fair­ly sim­ple and reli­able mech­a­nism. Ten­ta­tive­ly, the dia­gram shows the device of the draft reg­u­la­tor, what ele­ments the design of the device con­sists of.


The main task in the mech­a­nism is per­formed by a tem­per­a­ture-sen­si­tive ele­ment, which, when inter­act­ing with a spring, plays the role of a boil­er tem­per­a­ture con­trol sen­sor. When the tem­per­a­ture of the boil­er ris­es and falls beyond the estab­lished norm, the spring and the tem­per­a­ture-sen­si­tive ele­ment actu­ate the work­ing part of the device. The immer­sion sleeve inter­acts with the stem, which is direct­ly con­nect­ed to the actu­a­tor.

Due to the mechan­i­cal dri­ve, the work­ing part is con­nect­ed with the damper of the draft hole. The cur­rent draft reg­u­la­tor, under cer­tain con­di­tions, clos­es or slight­ly opens the damper, adjust­ing the area of ​​​​the inlet. The sim­plest mechan­i­cal action acts as a tem­per­a­ture con­troller for the heat­ing unit. The damper is more closed, the boil­er switch­es to the mode of poor air sup­ply. The damper is ajar more, more air enters the fur­nace, the inten­si­ty of com­bus­tion increas­es accord­ing­ly, the heat­ing tem­per­a­ture of the coolant increas­es. Every­thing is sim­ple and clear.

Impor­tant! Prop­er instal­la­tion of the fix­ture ensures the nor­mal move­ment of all ele­ments of a sim­ple design. Oth­er­wise, the trac­tion con­trol will per­form work that does not cor­re­spond to the spec­i­fied para­me­ters.

Instal­la­tion of the reg­u­la­tor is described in detail in the tech­ni­cal doc­u­men­ta­tion for the boil­er equip­ment. The instruc­tion tells how to prop­er­ly install the device on an exist­ing boil­er and how to set it up.

Do-it-yourself installation and calibration of the draft regulator

A sim­ple design allows you to install the device with your own hands. If we con­sid­er the boil­er from all sides, in the pro­jec­tion, then the front or side sur­face of the unit is select­ed for the instal­la­tion of the reg­u­la­tor. For this pur­pose, the prod­uct has a spe­cial hole. The reg­u­la­tor is mount­ed using a thread­ed con­nec­tion. The dia­grams show how to install the reg­u­la­tor and how not to install the fix­ture.

Note: In this case, there can be no mid­dle solu­tion. As indi­cat­ed in the instruc­tions, in this way, the draft reg­u­la­tor is installed on a sol­id fuel boil­er.

Cor­rect instal­la­tion is deter­mined by align­ing the device ver­ti­cal­ly and hor­i­zon­tal­ly. After the reg­u­la­tor is installed, all rotat­ing ele­ments are tight­ened, exist­ing mat­ing points are to be sealed with a spe­cial heat-resis­tant com­pound. The lever is placed in a posi­tion so that the hole through which the chain will pass is above the damper, in a ver­ti­cal posi­tion.

If the first stage is quite clear and sim­ple, then sub­se­quent actions require spe­cial atten­tion, accu­ra­cy and sequence of actions. Reg­u­la­tor cal­i­bra­tion is the most impor­tant stage of its func­tion­al­i­ty.

Stage one


By installing the reg­u­la­tor on your heat­ing unit, you can start kin­dling. Bring­ing the tem­per­a­ture of the boil­er water to 60 0C, record the same tem­per­a­ture on the fly­wheel (ther­mo­stat) of the draft reg­u­la­tor. The lever at this time must be con­nect­ed by a chain to the damper.

Impor­tant! The chain must be in a taut state and not have mechan­i­cal inter­fer­ence from the side. The damper at the time of cal­i­bra­tion is in a slight­ly open state, at a dis­tance of 1–2 mm from the edge of the con­tour of the exhaust hole. Dur­ing the adjust­ment phase, the flap posi­tion is man­u­al­ly deter­mined by length­en­ing or short­en­ing the chain.

Hav­ing fixed the damper in a cer­tain posi­tion, with the reg­u­la­tor set at 60 degrees, we do the fol­low­ing.

Stage two

The ther­mo­stat is set to 80 0C. If you installed the draft reg­u­la­tor cor­rect­ly and per­formed all the pre­vi­ous steps accord­ing to the instruc­tions, when the boil­er heats up to the set tem­per­a­ture, the damper will auto­mat­i­cal­ly close. Air will stop flow­ing into the fur­nace, and the inten­si­ty of fuel com­bus­tion will decrease accord­ing­ly. The error in tem­per­a­ture mea­sure­ment accu­ra­cy can reach +/- 5 0C, which is not crit­i­cal for ordi­nary, sim­ple heat­ing devices of heat­ing sys­tems.

It is nec­es­sary to adjust the draft reg­u­la­tor as often as pos­si­ble. Mechan­i­cal dam­age to the chain, a tight­ly mov­ing shut­ter can cause a vio­la­tion of the func­tion­al­i­ty of the device.


In terms of its accu­ra­cy, the mechan­i­cal method is undoubt­ed­ly infe­ri­or to the accu­ra­cy of auto­mat­ic con­trol devices. How­ev­er, from the point of view of expe­di­en­cy, for a sol­id fuel boil­er of the clas­si­cal type, this equip­ment option is no less effec­tive. In addi­tion, set­ting up automa­tion requires the par­tic­i­pa­tion of a spe­cial­ist, a heat­ing engi­neer and spe­cial elec­tron­ic devices.

The installed tem­per­a­ture sen­sor responds to the oper­a­tion of the boil­er, auto­mat­i­cal­ly act­ing as a stok­er. All sub­se­quent tem­per­a­ture devi­a­tions in the heat­ing sys­tem are record­ed by the heat­ing cir­cuit tem­per­a­ture con­trol devices.


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