Electric heaters of vapor-drop type


Among the many types of house­hold heaters, vapor-drop type heat­ing devices are deserved­ly pop­u­lar — units of a sim­ple prin­ci­ple of oper­a­tion with an afford­able price range.

In order to take into account the pos­si­bil­i­ty of acquir­ing this device — com­pact, effi­cient, reli­able, when choos­ing a device for heat­ing hous­ing, we will con­sid­er vapor-drop heaters in more detail.

Mod­ern vapor-drop (steam-con­den­sate, PKN) house­hold heater with a finned cas­ing and a tem­per­a­ture con­troller

The device and principle of operation of vapor-drop type heaters

This type of heater belongs to the group of “elec­tric con­vec­tors”, that is, to heaters, the oper­a­tion of which ini­ti­ates con­vec­tive air flows in the heat­ed room — the air in con­tact with the unit body heats up and ris­es, being replaced by a cold­er one.

Move­ment of con­vec­tive cur­rents ini­ti­at­ed by a wall heater

The basis of the design of vapor-drop type heaters is a nee­dle-type heat­ing ele­ment. The tubu­lar heater is mount­ed in the low­er part of a sealed cast-iron, steel or alu­minum tank with water, ethanol or methanol, filled above the lev­el of the heat­ing ele­ment, the nee­dle-shaped design of which does not require a large amount of liq­uid for this.

Schemat­ic rep­re­sen­ta­tion of the oper­a­tion of a vapor-drop heater in sec­tion


The con­tain­er in the PKN case is installed at an angle — the devi­a­tion of the plane of its base from the hor­i­zon­tal is approx­i­mate­ly 20 degrees.

When the device is con­nect­ed to the net­work, the water is heat­ed by the heat­ing ele­ment to the boil­ing point for sev­er­al min­utes and begins to evap­o­rate, fill­ing the free vol­ume of the tank with steam.

Hot steam under pres­sure, in con­tact with the met­al walls in the upper part of the tank, con­dens­es on them with the release of ther­mal ener­gy. Due to the high ther­mal con­duc­tiv­i­ty of the met­al, heat is trans­ferred to the air lay­ers clos­est to the heater, ini­ti­at­ing con­vec­tion in the room, and the con­den­sate in the tank flows down the inclined walls to its low­er part and, heat­ed up again by the heat­ing ele­ment, evap­o­rates again.

Scheme of the cir­cu­la­tion of the coolant in the vapor-drop heater

Thus, two coolants are involved in the heat trans­fer process — water and steam, but the liq­uid tem­per­a­ture does not exceed 100 degrees, and the steam in the tank can heat up to 120, so the upper part of the PKN is always hot dur­ing oper­a­tion.

To increase the inten­si­ty of heat trans­fer in most PKN mod­els, the upper part of the reser­voir with liq­uid is made in the form of mul­ti-sec­tion blocks of nar­row sec­tions with addi­tion­al exter­nal fins, which sig­nif­i­cant­ly increas­es the heat trans­fer area.

Impor­tant! The vol­ume of the reser­voir of a vapor-drop heater, free from liq­uid, is filled with a tech­ni­cal vac­u­um, there­fore, the tran­si­tion of the coolant from a liq­uid state to a vapor dur­ing heat­ing occurs bypass­ing the boil­ing process, that is, silent­ly.

Technical characteristics and types of steam condensate heaters

The main cri­te­ri­on for choos­ing a PKN is the pow­er required to heat a room of a spe­cif­ic area and vol­ume. For house­hold mod­els of vapor-drip heaters, this para­me­ter is in the range from 0.5 to 2.0 kW. Accord­ing­ly, in regions with a tem­per­ate cli­mate, in the pres­ence of effec­tive exter­nal insu­la­tion of build­ing envelopes, a PKN with a pow­er of 1.5 kW will pro­vide heat­ing for a room up to 15 sq. m.

Vari­ants of the loca­tion of the wall-mount­ed PKN in res­i­den­tial premis­es

The design of var­i­ous mod­els of vapor-drop heaters requires an accu­rate cal­cu­la­tion of the ratio of the pow­er of the nee­dle heat­ing ele­ment, the sur­face area of ​​the unit body, tak­ing into account the fins and the amount of coolant used in the tank.

The max­i­mum PKN pow­er of 2 kW is cho­sen for safe­ty rea­sons. With ref­er­ence to this val­ue, the vol­ume of the tank, the amount of liq­uid poured into it and the heat trans­fer area are cal­cu­lat­ed. The ratio of these para­me­ters should ensure effec­tive vapor­iza­tion in the tank at a safe steam pres­sure (not more than 0.07 MPa), the sur­face tem­per­a­ture of the body is not more than 115 degrees, and the loca­tion of the nee­dle heat­ing ele­ment is always below the liq­uid lev­el — even when the heater is oper­at­ing in the max­i­mum nor­mal mode.

Impor­tant! A cor­rect­ly per­formed cal­cu­la­tion of the ratios of the pow­er of the heat­ing ele­ment, the amount of coolant, the vol­ume of the reser­voir and the heat trans­fer area of ​​the body allows not to equip the PKN with an over­pres­sure relief valve. At the same time, for safe­ty rea­sons, devices with a pow­er of more than 1.5 kW are pro­duced with increased strength char­ac­ter­is­tics and are intend­ed main­ly for indus­tri­al premis­es.

Vapor-drop type heaters are mul­ti-sec­tion bat­ter­ies with an elec­tron­ic con­trol unit, with a pow­er of 1.5, 0.9 and 0.5 kW.


Vapor-drop type heaters, as men­tioned above, are divid­ed into house­hold appli­ances and units for indus­tri­al use.

Devices for indus­tri­al use are more pow­er­ful, respec­tive­ly, and their dimen­sions are larg­er. With the release of such units, the aes­thet­ics of exe­cu­tion are rel­e­gat­ed to the back­ground, giv­ing way to work effi­cien­cy, the strength of the case and the secu­ri­ty of the con­trol sys­tem, as well as the sup­ply cable.

Steam con­den­sate heaters for indus­tri­al appli­ca­tions

How­ev­er, even indus­tri­al vapor-drop heaters of mod­ern mod­els have a class of exte­ri­or fin­ish above aver­age, which allows them to be used in every­day life with­out prej­u­dice to the inte­ri­or of the room.

Steam con­den­sate heaters of increased pow­er BHeat Air 3000 with a pow­er of 3 kW for indus­tri­al use — space heat­ing up to 30 sq. m.

Mod­ern PKN heaters, both for domes­tic and indus­tri­al pur­pos­es, are equipped with a secu­ri­ty sys­tem (auto­mat­ic shut­down when the bimetal­lic plate is over­turned or over­heat­ed) and tem­per­a­ture con­trol — a ther­mo­stat that oper­ates on the basis of data from a tem­per­a­ture sen­sor, stan­dard or addi­tion­al­ly installed by hand in the actu­al area of ​​​​the room — accord­ing to reach­ing the set tem­per­a­ture in this zone, the heater will turn off.

Steam con­den­sate heater with an elec­tron­ic con­trol unit equipped with a liq­uid crys­tal dis­play

PKN mod­els by loca­tion are divid­ed into floor, wall and uni­ver­sal. The prin­ci­ple of oper­a­tion of devices of all these designs is the same, the heat trans­fer by the units is car­ried out by both sides of the pan­el.

Floor-stand­ing units are equipped with sup­port legs that pro­vide it with a sta­ble posi­tion on a hor­i­zon­tal plane, or a plat­form with wheels that facil­i­tate move­ment.

Impor­tant! If the unit has a per­ma­nent loca­tion, but there is a fear of tip­ping over, then after dis­man­tling the wheels, the sup­ports can be fixed on the floor using self-tap­ping screws.

In the event of an unfore­seen over­turn­ing of the heater, the auto­mat­ic dis­con­nec­tion of the net­work will work, and the rel­a­tive­ly low tem­per­a­ture of the hous­ing will not be able to cause a fire.

Floor-stand­ing mod­el of a steam-and-drip domes­tic heater with holes in the sup­ports for fas­ten­ing to the floor with self-tap­ping screws


Wall-mount­ed mod­els have holes on one side of the pan­el for brack­ets that attach the unit to the wall. The design and size of the brack­ets ensure the loca­tion of the PKN at a dis­tance of 7–10 cm from the sup­port­ing base, which reduces the ther­mal effect of the heater on the wall and does not pre­vent air con­vec­tion from the back of the device. The sec­tion of the wall locat­ed behind the installed heater must be addi­tion­al­ly equipped with heat pro­tec­tion made of heat-resis­tant mate­r­i­al.

Steam con­den­sate wall heater

The design of the uni­ver­sal loca­tion PKN allows you to install sup­port legs on them or mount them on the wall. The effec­tive­ness of one or anoth­er method of appli­ca­tion depends on the spe­cif­ic oper­at­ing con­di­tions.

PKN uni­ver­sal place­ment mod­els — for use on the floor or on the wall

Application of PKN

The pro­duc­tion of steam con­den­sate heaters for both domes­tic and indus­tri­al needs is based on the pos­si­bil­i­ty of their use for a vari­ety of pur­pos­es:

  • heat­ing of urban and sub­ur­ban build­ings for res­i­den­tial, pub­lic and indus­tri­al pur­pos­es;
  • in the north­ern regions — heat­ing of rooms remote from the main heat­ing means installed in the house;
  • main­te­nance in the base­ment floors and base­ments of the tem­per­a­ture nec­es­sary for the nor­mal func­tion­ing of the water sup­ply and fan sys­tem in the win­ter;
  • an alter­na­tive method of heat­ing hous­ing dur­ing emer­gency repairs of the main heat­ing sys­tems;
  • heat­ing of hous­ing that is inap­pro­pri­ate for equip­ment with a heat­ing cir­cuit due to sig­nif­i­cant heat loss­es asso­ci­at­ed with a large length of pipe spans;
  • main­tain­ing the required tem­per­a­ture regime in the premis­es when per­form­ing work there that requires it tech­no­log­i­cal­ly.

In fact, the scope of steam con­den­sate heaters is much wider, so the high degree of demand for PKN can be said with con­fi­dence.

Options for the loca­tion of the PKN in res­i­den­tial premis­es

Advantages and disadvantages of vapor-drop design heaters


Assess­ing the fea­si­bil­i­ty of using a steam-con­den­sate type heater under cer­tain con­di­tions, you need to know the main pros and cons of these units.

Advan­tages of PKN:

  • envi­ron­men­tal friend­li­ness — the absence of any emis­sions into the heat­ed space,
  • safe­ty — a fair­ly low case tem­per­a­ture (they do not affect the humid­i­ty in the room and do not burn dust), equipped with an auto­mat­ic shut­down sys­tem in case of over­heat­ing, noise­less­ness;
  • a suf­fi­cient degree of automa­tion of con­trol of most mod­els;
  • dura­bil­i­ty — due to the lack of air in the tank, which is nec­es­sary for cor­ro­sion, but is lim­it­ed by the life of the heat­ing ele­ment;
  • frost resis­tance — the expan­sion of the coolant dur­ing freez­ing will not cause the destruc­tion of the tank due to the pres­ence of free vol­ume in it;
  • com­pact­ness, pos­si­bil­i­ty of wall instal­la­tion;
  • tech­no­log­i­cal effi­cien­cy — ease of instal­la­tion and dai­ly main­te­nance, no need for a chim­ney.

Dis­ad­van­tages of vapor-drop heaters:

  • rather high cost of units, even for domes­tic pur­pos­es;
  • inher­ent in all elec­tric heaters increased pow­er con­sump­tion;
  • the impos­si­bil­i­ty of repair­ing heaters in domes­tic con­di­tions in cas­es asso­ci­at­ed with depres­sur­iza­tion — an error in the amount of coolant is fraught with an explo­sion when heat­ed.

Self-manufacturing of PKN

The high cost of steam con­den­sate heaters, with the seem­ing sim­plic­i­ty of the prin­ci­ple of oper­a­tion, gives rise to the temp­ta­tion to man­u­fac­ture such a unit on their own, giv­en the mod­ern avail­abil­i­ty of mate­ri­als, com­po­nents and tools.

Indeed, today vapor drop heaters often made with your own hands — mate­ri­als and com­po­nents for their assem­bly can be eas­i­ly found on sale. But it is not real­is­tic to pro­duce such units at home only after read­ing the instruc­tions and rec­om­men­da­tions — there are a lot of designs of such devices, and the man­u­fac­tur­ing tech­nol­o­gy of each has indi­vid­ual char­ac­ter­is­tics. At the same time, it is nec­es­sary to have not only gen­er­al assem­bly and weld­ing skills, but also prac­ti­cal expe­ri­ence specif­i­cal­ly in the man­u­fac­ture of PCN.

In addi­tion, the assem­bly of a low-pow­er vapor-drop heater is imprac­ti­cal — there are many oth­er types of inex­pen­sive heat­ing devices, more­over, indus­tri­al-made ones that can cope with home heat­ing bet­ter and safer. And a home-made high-per­for­mance unit is not so aes­thet­ic as to be used to heat a home.

Home­made PKN from a steel pipe with a heat­ing ele­ment of 500 W

The heat­ing reg­is­ter shown above, oper­at­ing on a vapor-drop type, can serve as a visu­al aid to the ques­tion of how to make a PKN your­self

The unit is assem­bled from four frag­ments — “streams” made of a steel pipe with a diam­e­ter of 50 mm and plug-plates made of sheet steel. A heat­ing ele­ment is mount­ed in the low­er “stream”, equipped with a branch pipe. In the upper part of the reg­is­ter there is a plug with a valve through which a mix­ture of water and antifreeze was poured into the radi­a­tor and air was bled under pres­sure when the device was first turned on.

Schemat­ic rep­re­sen­ta­tion of the PKN device in sec­tion


A coolant is poured into the low­er “stream”, which evap­o­rates when heat­ed. Steam fills all the free space of the “streams”, gives off heat to the walls of the radi­a­tor and con­dens­es on them, then flow­ing back down to the heat­ing ele­ment.

The design of the PKN may be sim­pler, but this does not elim­i­nate the need for spe­cif­ic pro­fes­sion­al skills.

PKN of hand­i­craft pro­duc­tion of a sin­gle-strand struc­ture made of steel pipe

Impor­tant! The lack of vac­u­um in a home­made radi­a­tor caus­es the coolant to boil, accom­pa­nied by a cer­tain noise dur­ing oper­a­tion of the unit.


Steam heaters are effi­cient elec­tric heaters. Their effec­tive­ness explains the demand for these devices, which, in turn, affects the pric­ing pol­i­cy — the cost of PKN is high­er than the prices of many oth­er infrared heaters. How­ev­er, striv­ing for the effi­cien­cy of the heat­ing method, one should not for­get about a more impor­tant fac­tor — the safe­ty of the equip­ment, which can­not be ful­ly ensured in the hand­i­craft pro­duc­tion of units.

The main essence of the article

  1. Vapor-drop heat­ing devices are mod­ern reli­able units, the sim­plic­i­ty of the design of which is their advan­tage, and not a flaw.
  2. When choos­ing a method of heat­ing a home, one should not ignore PKN — effec­tive heaters, knowl­edge of the char­ac­ter­is­tics of which will sim­pli­fy their use. The use of vapor-drop heaters in every­day life and at work is proof of their effec­tive­ness.
  3. When plan­ning the use of PKN, it is nec­es­sary to know their tech­ni­cal char­ac­ter­is­tics, types of instru­ment exe­cu­tion and selec­tion cri­te­ria for these units.
  4. Self-man­u­fac­tur­ing of drip-steam elec­tric heaters is pos­si­ble, but is asso­ci­at­ed with the risk of acci­dents dur­ing the oper­a­tion of such equip­ment in case of a design error.


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