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
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
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
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”
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.
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.
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.
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.