Pressure in the heating system: what the developer needs to know

Most own­ers of pri­vate hous­es inde­pen­dent­ly main­tain an autonomous heat­ing sys­tem. As a result, the most fre­quent ques­tion they have is: “What is the oper­at­ing pres­sure in the heat­ing sys­tem (CO), and what are the rea­sons for its devi­a­tion from the norm?”. The answers to these ques­tions will be the sub­ject of this pub­li­ca­tion.


We study the theory

Efficient operation of the heating system

The most impor­tant indi­ca­tors of any CO, which deter­mine its effec­tive­ness, are tem­per­a­ture and pres­sure.

Every­thing is clear with the first para­me­ter: it depends on the oper­a­tion of the heat gen­er­a­tor. Regard­ing the sec­ond indi­ca­tor: if the sys­tem is not filled with coolant, the pres­sure in it is equal to atmos­pher­ic. When fill­ing the con­tours, water (due to grav­i­ta­tion­al forces) begins to act on the struc­tur­al ele­ments. After start­ing the boil­er plant, water (antifreeze, brine) begins to heat up and expand, cir­cu­la­tion appears. After turn­ing on the cir­cu­la­tion pump, the effect on the inter­nal sur­faces of the CO ele­ments increas­es sharply, and the water pres­sure increas­es.

It should be under­stood that in cer­tain sec­tions of the heat­ing cir­cuit, this indi­ca­tor is not the same. For exam­ple, in the sup­ply pipeline (after the cir­cu­la­tion pump), the pres­sure is always high­er than in the return flow sec­tion.

Sum­ma­riz­ing the above: the pres­sure of the coolant in the heat­ing sys­tem depends entire­ly on the tem­per­a­ture of the coolant, the flow area of ​​the pipeline, fit­tings and equip­ment, as well as the pow­er of the pump.

Deciding on terminology

Home heating system

In mod­ern heat engi­neer­ing and reg­u­la­to­ry doc­u­ments, there are sev­er­al def­i­n­i­tions:

  • Sta­t­ic, appears in the sys­tem under the influ­ence of grav­i­ty on the coolant.
  • Dynam­ic, caused by the move­ment of water in CO.
  • The oper­at­ing pres­sure in a heat­ing sys­tem is the sum of sta­t­ic pres­sure and dynam­ic pres­sure.
  • Nom­i­nal, char­ac­ter­izes the indi­ca­tor at which the man­u­fac­tur­er guar­an­tees the CO ele­ments a cer­tain peri­od of oper­a­tion with­out changes in per­for­mance.
  • Max. This is a bor­der­line indi­ca­tor that the CO can with­stand with­out fail­ure of its ele­ments.
  • Crimp­ing or test­ing, usu­al­ly tak­en 1.5–2 times high­er than the work­er.

Impor­tant! The most “weak link” in any heat­ing sys­tem is the heat gen­er­a­tor heat exchang­er. The most durable mod­els can with­stand about 3 kg / cm2 or 0.3 MPa. In addi­tion, the dis­tri­b­u­tion of CO, made by a poly­mer pipe, also has lim­i­ta­tions.

Statics and dynamics

Statics and dynamics of CO

In an open, grav­i­ta­tion­al CO, the sta­t­ic effect of the coolant on struc­tur­al ele­ments is equal to the height dif­fer­ence between the low­er and upper­most points of the struc­ture. More­over, the high­est fig­ure will be at the bot­tom point.

Quite often, the instal­la­tion of a heat­ing sys­tem for a pri­vate house involves the pres­ence of a cir­cu­la­tion pump and a closed-type expan­sion tank. In such a design, there is both a sta­t­ic (due to height dif­fer­ence) and a dynam­ic effect that will be cre­at­ed by pump­ing equip­ment. As you move away from the cir­cu­la­tion pump, this indi­ca­tor slight­ly decreas­es due to the hydraulic resis­tance cre­at­ed by the pipeline, fit­tings, and oth­er ele­ments of the sys­tem.

“jumps” and “drops”

Jumps and drops in CO

Dur­ing the oper­a­tion of autonomous COs, almost every own­er is faced with the prob­lem of pres­sure surges. An increase in this val­ue may indi­cate:

  • Heat car­ri­er over­heat­ing.
  • Incor­rect cal­cu­la­tions of the pipeline sec­tion.
  • CO pol­lu­tion.
  • The pres­ence of air pock­ets.
  • Incor­rect oper­a­tion of the pres­sure reg­u­la­tor in the heat­ing sys­tem.

Tip: If you encounter this prob­lem, the first thing to do is to check the recharge. In prac­tice, it is this rea­son that experts note as the most com­mon.

The pres­sure drop to the own­er of an autonomous CO of a pri­vate house can say the fol­low­ing:

  • leaks. To iden­ti­fy this prob­lem, most often, it is enough to care­ful­ly exam­ine the pipeline and the equip­ment includ­ed in the CO.

Tip: Coolant leak­age from CO can also be “imper­cep­ti­ble”, through a dam­aged expan­sion tank mem­brane. To check, you need to press the air pump valve of the expan­sion tank. The pres­ence of water indi­cates a crack in the mem­brane.

  • Remov­ing the air lock through the air vent. As a rule, this prob­lem occurs soon after fill­ing with CO.

Tip: Experts rec­om­mend that the coolant should be sub­ject­ed to a deaer­a­tion pro­ce­dure before being pumped into the sys­tem.

  • Over­lap­ping of the CO sec­tion with a shut-off and con­trol device.

Control methods

CO pressure control methods

To mon­i­tor the pres­sure in CO, spe­cial­ized devices are used — pres­sure gauges, which show all changes in this val­ue in real time. Struc­tural­ly, these devices can car­ry a pure­ly infor­ma­tive func­tion, or be equipped with a con­tact group that switch­es the oper­a­tion of some CO ele­ments. For exam­ple, when the pres­sure ris­es above the nom­i­nal val­ue, the con­tacts of the pres­sure gauge open, which leads to the shut­down of the heat gen­er­a­tor.

Impor­tant! For oper­a­tional mon­i­tor­ing of the state of CO, pres­sure gauges are installed: on the pip­ing of the boil­er unit; at the inlet and out­let of pump­ing equip­ment; on the sides of the water pres­sure reg­u­la­tor in the heat­ing sys­tem. In addi­tion, experts rec­om­mend installing pres­sure gauges at branch­ing sites; on the sides of the mud col­lec­tors; at the low­er and upper points of CO.

As you know, when heat­ed, the coolant expands, as a result of which its vol­ume increas­es. An expan­sion tank, which can be of a closed or open type, is respon­si­ble for com­pen­sat­ing for the vol­ume of the expand­ing coolant and a sharp jump in pres­sure.

To main­tain the val­ues ​​​​of the work­ing and nom­i­nal pres­sure, the CO includes the so-called safe­ty group, which con­sists of a pres­sure gauge, an auto­mat­ic air vent and a blast valve.

Pressure gauge, automatic air vent, blast valve

What is considered normal?

In pri­vate hous­es, the work­ing pres­sure should be the sum of sta­t­ic and dynam­ic. As a rule, this val­ue varies in the region of 1.5 — 2 kg / cm2.

Most of our com­pa­tri­ots liv­ing in apart­ment build­ings with a cen­tral CO are inter­est­ed in the ques­tion, what is the pres­sure in the heat­ing pipes in the apart­ment? It is almost impos­si­ble to answer this ques­tion unequiv­o­cal­ly: it all depends on the num­ber of storeys of the house and the cho­sen wiring dia­gram.

Heating system pressure standards

As a rule, the pres­sure in the CO of a mul­ti-storey build­ing should not be less than 5 atmos­pheres, which are used to over­come the num­ber of storeys and local resis­tances. Most often, in five-sto­ry build­ings, this val­ue reach­es 4–5 bar; and in nine-sto­ry build­ings — 6–8 bar; in the sup­ply line it is usu­al­ly 10–12 kg/cm2 and depends on the length of the route.

Impor­tant! It is not rec­om­mend­ed to change the pres­sure in the heat sup­ply pipes in the apart­ment on your own. This can adverse­ly affect the effi­cien­cy of the heat­ing sys­tem and the life of the heaters.

As a con­clu­sion. No mat­ter how com­pe­tent­ly the heat­ing sys­tem of a pri­vate house is installed, soon­er or lat­er each own­er is faced with pres­sure drops and surges that sig­nal prob­lems and the need for mea­sures to detect and elim­i­nate them.


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