Reasons for pressure drop in a gas boiler. Reasons for the drop in pressure in a gas boiler Should the pressure in the heating system drop?

To heat a large country house, owners often install gas double-circuit boilers. They have a number of advantages compared to other types of equipment. Devices that operate on blue fuel are economical and affordable, since gas pipelines are laid even in the most remote corners of the country. Even if the central gas system does not run near your home, you can buy a cylinder and effectively heat the room in winter.

Why double-circuit boilers? They perform two jobs at once - they maintain the desired temperature in the room and supply the house with hot water, so there is no need to install a boiler or a water heater to ensure hot water flows from the tap.

Today's market offers different models of heating equipment from well-known domestic and foreign manufacturers. The devices differ in power, size, and price. No matter how high-quality and productive a boiler is, it may malfunction during operation. The most common failure is a drop in pressure.

If the pressure in the heating system is lower than required, it does not function. In addition, this threatens heating equipment breakdowns. There is a clearly defined range when blood pressure is considered normal. To determine why the pressure in a gas boiler drops, you should familiarize yourself with what it can be and what affects it.

1. Static – the force of pressure of the coolant, which is at rest, on the heating system.
2. Dynamic - the pressure of the coolant that is transported through the pipeline and other elements of the system.
3. Maximum operating pressure – the pressure at which the heating device is still operating. If the value is even higher, a breakdown occurs.

Pressure in gas boilers is measured in atmospheres. For different devices, different values ​​of pressure force may be considered normal. The heating system is adversely affected by both low and high pressure. For example, if the device allows an indicator of two atmospheres, but it has increased to three, it is necessary to urgently take some measures. Otherwise, the pipeline may depressurize and the entire heating system will fail.

Note! The minimum permissible pressure can only be when the coolant is just being pumped into the system. When heated, the water expands, due to which the pressure gradually increases to normal operating pressure.

Pressure control

Gas boilers belong to high-tech equipment. It contains many parts and elements responsible for adjusting the device and maintaining it in working condition. If for some reason the control parts do not function correctly, the gas boiler will malfunction. For an ordinary private house, the pressure is set in the range from 1.5 to 2 atmospheres.

Mainly in systems with forced circulation, the pressure in the gas boiler drops. The reasons may be different, but they all boil down to the fact that there is a leak somewhere. If the house has a heating system that operates due to natural circulation, the pressure in the device may drop as a result of airing. It is rarely possible to fix a problem on your own. It is better to call a specialist to avoid problems.

Causes of pressure drop

If you notice problems in the operation of your heating equipment, you should immediately look for the cause. In some cases, it is impossible to cope on your own, since you cannot do without the use of professional equipment. Most often, the pressure in gas boilers drops for the following reasons:

• coolant leak from the heating system;
• lack of electricity for a long period;
• problems in the operation of the device’s expansion tank;
• The double-circuit boiler was chosen incorrectly and is not suitable for use in this case.

Low pressure causes heating equipment to stop functioning. When the coolant pressure decreases, water does not enter the device, but if the gas pressure drops, the equipment switches off spontaneously. To prevent such situations, you should provide the heating system with proper maintenance, periodically carry out diagnostics and, if necessary, repair work. It is better to prevent problems with the functioning of the heating system than to be in a cold house in winter.

Another reason for a decrease in pressure in a gas boiler is the formation of air pockets. Their appearance is caused by the following factors:

• the heating system was filled with coolant incorrectly;
• The coolant, which is often water, contains air. If you do not remove it from the water using a special device before pumping it into the system, the problem of air locks will definitely appear;
• air entering the system due to poor sealing of connections;
• clogging or improper operation of the air release valve.

Air locks in the heating system mean not only low pressure, but also other troubles. They cause noise in the system, which in turn leads to vibration. When the pipeline vibrates, connections become loose, which is the cause of leaks. Air also causes a disruption in the effective circulation of the coolant. Some batteries may not warm up at all, and gas consumption will increase two to three times.

How to solve a problem

It is strictly not recommended to undertake repairs of heating equipment yourself, especially if you are not familiar with the diagrams and operating principles of boilers. However, in some cases, urgent measures are required.

To resume operation of the heating system, a whole range of work must be done. The first thing you need to do is find out why the pressure in a double-circuit gas boiler drops. In a forced circulation system, the most common problem is coolant leakage. To detect the location of the leak, you should carefully inspect the connection points of the system elements.

Note! The cause of leaks is poor quality installation work. When installing a heating system, seek help from specialists to prevent possible problems.

The leak may not be noticed during the initial inspection. If puddles are already forming under the pipeline, the reaction must be immediate, since if problems are ignored, disastrous consequences can arise. Old pipes may leak due to corrosion damage.

If your home has a complex heating system piping, problems may arise when leaks are detected. If the pressure is unstable, and the owner cannot independently detect the cause, you need to seek qualified help. Specialists have at their disposal specialized equipment that allows them to easily detect the location of the leak and effectively correct the error.

Before starting repair work to eliminate leaks, you should first disconnect the radiators and boiler from the system. Once the damaged area is identified, repairs can begin.

1. If the pipe is damaged, it is removed and a new one is installed.
2. In case of leakage at the pipe connection, additional sealing is carried out. To do this, you can use a special tape or silicone sealant.
3. If the coupling is damaged, it should be replaced with a new one.

Note! It is especially difficult to detect a leak if it occurs as a result of damage to the heat exchanger. During operation, due to mechanical damage or wear, cracks appear on the heat exchanger. When the boiler is operating, moisture flows out and enters the combustion chamber and disappears without a trace, so it is quite difficult to detect a problem.

Preventing the formation of air jams

In order to avoid such an unpleasant situation as a decrease in pressure during the operation of the heating system, preventive measures should be taken. The first thing you need to pay attention to is the correct installation of the pipeline and connection of the heating equipment. Most problems are caused by mistakes made at this stage.

To prevent air pockets from getting into the heating system of a private home, you should put the equipment into use correctly and first check all elements, connections, and valves. Before starting up the equipment, you should check its functionality. Using a compressor, apply a pressure that is a quarter higher than normal operating pressure. If the pressure does not weaken within half an hour, then everything is fine and the system can be put into operation. When the pressure drops sharply, leaks are possible. They need to be detected and eliminated.

The heating system of a private house, which operates on double-circuit gas boilers, is very profitable, economical and simple. If the equipment is properly maintained, problems can be avoided.

The heating system of multi-storey buildings is quite complex, and can only work normally if all the necessary requirements are met, which necessarily include maintaining normal operating pressure. The value of this parameter directly determines the full circulation of the coolant, and as a result, the quality of the required heat transfer. And what is also very important, normal pressure is the key to longevity and reliability of the entire operation, reducing the likelihood of emergency situations.

So, working pressure in the heating system - how to check the norm, reasons for the decrease and increase? This question often arises among apartment owners in several cases. Most often, the reason is unsatisfactory heating of the home, that is, a decrease in the temperature of the coolant. It is important to have an understanding of this parameter and, if necessary, carry out repair work on the intra-apartment circuit or completely replace it. In this regard, it is worth considering aspects directly related to current norms and standards. It will also be useful to familiarize yourself with the reasons for possible deviations and ways to eliminate them.

The pressure in the central heating system is divided into pressure testing and working.

• Pressure testing is the pressure that is created in the system during hertest after performing any installation or repair work. As a rule, pressure testing is carried out before the start of the next heating season. This set of measures involves a time-limited increased load on the system elements. Such a process is necessary in order to check the performance of the heating, the reliability of connections in the circuits, the integrity and proper permeability of the pipes and radiators of the system, since pressure drops may occur during its operation.

• Working pressure is considered to be the pressure at which the system must operate continuously throughout the heating period.

The working pressure indicator includes static and dynamic components:

• Static pressure is the pressure created by the natural pressure of water rising through the pipe channels. The higher the risers (correspondingly, the more floors in the house), the more significant its parameter.
• Dynamic is the artificially created pressure that occurs when circulation pumps act on the flow of water.

In multi-storey buildings, the coolant in the heating system is most often first supplied to the upper floors, and pumps are indispensable for supplying it. Moreover, the higher the building, the greater the pressure should be, and the flow acquires a very considerable speed. For nine-story buildings, the pressure standard is set at 5÷7 technical atmospheres (bar), which corresponds to approximately 50÷70 meters of water column or, based on SI system standards, 0.5÷0.7 MPa. If the house has more floors, then the pressure required is higher than -7 ÷ 10 technical atmospheres (70 ÷ 100 m water column or 0.7 ÷ 1.0 MPa). The operating pressure in the heating circuit of the top and bottom floors should not differ by more than 10%, and the pressure test pressure by 20%.

Most often, in average urban multi-storey building, the working pressure on the coolant supply pipe is 6 atmospheres, and on the “return” pipe - 4÷4.5 atmospheres. However, it should be noted that many factors influence pressure indicators in the system. The cleanliness of the internal channels of main pipes and circuits is also important.

In an autonomous system of a private house or apartment, the pressure and temperature of the coolant must be monitored by the owner himself. For this purpose, special devices (pressure gauge and thermometers) are installed in the boiler area, which are designed to monitor these parameters. Most often today, in autonomous systems, the necessary pressure is created using a circulation pump, that is, forcibly. Although, systems with natural circulation (beyond checkdifference in density of hot and cooled water) are still quite widely used.

Why might pressure changes occur?

As mentioned earlier, in multi-story buildings, operating pressure can depend on the number of floors, as well as a number of other factors.

Pressure readings may deviate from established standards for the following reasons:

• Most widespread prerequisite for pressure reduction in old houses is the overgrowing of the internal surfaces of pipes and radiators with lime deposits and debris.
• The pressure can drop sharply if there is no electricity in the boiler room where the circulation pumps are installed. Failure of such pumps cannot be ruled out. And in general - outdated, long ago non-changing equipment in boiler rooms can lead to a decrease in the efficiency of the entire system.
• The cause is often a coolant leak, that is, depressurization of the system.
• The normal temperature in the room where the elevator unit is equipped, from which the coolant is “distributed” to the risers, is also important. At subzero temperatures, the unit may respond by increasing the pressure in the system.
• Sometimes the reason lies in the ill-considered actions of apartment owners. This could be the unauthorized replacement of pipes with an oversized or, conversely, narrowed diameter, the installation of taps on bypasses, the installation of additional sections of heating gates or the installation of heat exchange devices with increased thermal power, the installation of radiators in loggias or on the balcony.
• The “enemy” of the normal operation of the system is always air pockets in heating radiators if the owners do not ensure timely checking and bleeding of air.
• Poor quality coolant in a central heating system can also lead to pressure instability.
• Differences are always observed during preparatory work before the heating season, when the system is being pressure tested. Likewise, after carrying out repair or modernization work to replace radiators or pipeline sections, under test loads, when the pressure increases by 0.5÷1.5 times. These measures are carried out before the start of the heating season to identify vulnerable areas of the system in advance so that they do not appear later, during the cold season. Then this will become a real problem, since when carrying out repairs, one or even several houses have to be completely disconnected from heating.
• Water hammer is a short-term sharp increase in pressure that cannot be foreseen. Therefore, when purchasing new radiators, you need to study their characteristics, since they must have a safety margin. So, if, when pressure testing the system, the pressure rises to 10 atmospheres (bar), then you need ones designed for 13–15 atmospheres.

Pressure and temperature are monitored by common house-wide control and measuring instruments located in the heating station (at the elevator unit). If you want to independently control the condition of your section of the heating system, these devices can be installed in your apartment. They are usually placed at the coolant inlet to the radiator.

How to deal with pressure changes

Features of central heating systems

It should be correctly understood that in heating mains running from boiler houses or thermal power plants to consumers, the level of pressure and temperature of the coolant differs significantly from what is supplied to apartments. Naturally, it must be reduced to safe values ​​that meet the standards.

The intra-house coolant temperature and pressure in the heating system circuits are adjusted by adjusting the elevator unit, which is most often located in the basement of a multi-story building. In this design, hot water supplied to the heating circuit from the main is mixed with cooled return coolant.

The design of the elevator unit includes a so-called mixing chamber, equipped with a nozzle, the size of which regulates the flow of hot water into the house heating system. Since the coolant coming from the central pipeline has a very high temperature, before entering the heating circuit of the house, it is mixed with the cooled “return” water.

The illustration above shows the main working part of the elevator assembly with a mixing chamber and nozzle. In the diagram below, the location of this element is highlighted with a yellow ellipse.

1 - main line for the central supply of hot coolant.

2 - return pipe of the central main.

3 - valves that disconnect the intra-house system from the central heating main.

4 - flange connections.

5 - mud filters, to prevent clogging of the pipes of the intra-house system with insoluble impurities or debris, which are difficult to completely get rid of in central lines.

6 - pressure gauges for constant monitoring of pressure in different parts of the system. Please note that pressure gauges are installed both on the main pipes, that is, before and after the elevator unit. It is the latter that controls the pressure level in the intra-house system.

7 - thermometers, also showing the temperature in different parts of the general system: tc - in the central line, at the inlet, tc - in the supply pipe of the intra-house heating system, tc and tc - in the return of the system and the central line, respectively.

8 - the main working unit, that is, the elevator itself.

9 - jumper pipe, which ensures the supply of cooled coolant from the return to the mixing chamber of the elevator unit.

10 - valves that make it possible to disconnect the intra-house wiring of the heating system from the elevator unit. This is necessary, for example, to carry out certain preventive or repair work.

11 - supply pipe for intra-house wiring, into which coolant of the required temperature is supplied mi under the established pressure standards.

12 - return pipe for intra-house wiring.

It is clear that the diagram is given with significant simplification, simply to demonstrate the principle of operation of the elevator. In fact, this elevator unit looks much more complicated, and only heating network specialists can understand its design.

Only heating system specialists should monitor the stable operation of elevator equipment. They monitor pressure and temperature indicators, conduct technical inspections, carry out preventive measures and, if devices fail, replace them with serviceable ones. Thus, most problems with insufficient or excess pressure in the intra-house system can be solved by properly adjusting the elevator unit and monitoring its operation.

The combination of simplicity of the operating principle and reliability - the elevator unit of the heating system

Despite the introduction of innovative control systems, there is no hurry to abandon the use of elevator units that are simple in their operating principle. And this is unlikely to happen in the near future. To learn more about how it functions, what devices it consists of, how it is calculated and maintained - read about all this in a special publication on our portal.

However, some nuances may depend on the apartment owners.

• For example, standard pipeline risers have a nominal diameter of 25÷33 mm. The pipes of the heating circuit of the apartment should have the same diameter. If there is a need to replace a certain section of the pipeline, then the new pipe inserted in place of the damaged section should have the same diameter as the removed one - not narrower and not wider.
• It is necessary to regularly carefully inspect the heating circuit of the apartment, especially carefully checking the connections of pipes and radiators.
• It is periodically necessary to bleed air from radiators. This is especially true for apartments located on the top floor of the building. Modern batteries go on sale already equipped with special valves, so servicing the devices is not difficult. If not, you will have to install Mayevsky taps or automatic air vents on the batteries.

• To ensure that the heating circuit of the apartment does not suffer from water hammer, which, unfortunately, is not excluded during test runs of the central system before the heating season, a special device is cut into the pipe supplying coolant to the apartment at the beginning of the circuit. It prevents the negative impact of sudden pressure surges on radiators and pipe connections.

Pressure in the autonomous heating system of a private house

Most often, the heating system of a private house involves the presence of a boiler equipped with a heat exchanger. This element is probably the weakest link in terms of pressure. Most heat exchangers are designed for pressure loads exceeding 5, maximum 7 atmospheres.

Due to the fact that the maximum permissible pressure of the heating circuit is determined by the element most unstable to it, which is the heat exchanger, this value is the determining standard for autonomous heating. Therefore, when purchasing a heating unit, you need to pay special attention to what pressure it is designed for. But there is no “tragedy” in this - as a rule, for a one-story house or autonomous heating in an apartment, an indicator of 2–3 atmospheres (0.2–0.3 MPa or 20–30 meters of water column) is quite sufficient.

If an open expansion tank is provided in the autonomous heating system, then there is no need to worry about the fact that pressure dangerous to the integrity of pipes and radiators may arise. The only thing we must not forget about is that after installing such a structure, you must carefully ensure that there is a sufficient amount of coolant in the system, since it tends to evaporate.

If an open expansion tank is installed in the heating circuit, the pressure will never be higher than the static maximum. This ensures the safety of the heating system elements, but is not always effective in heating the house, precisely because the pressure is too low. The explanation is simple - the coolant, slowly moving through the channels of the circuit and overcoming hydraulic resistance, quite quickly loses its thermal potential, and approaching the “return” in the boiler room, it becomes almost cold. Therefore, the boiler has to work almost continuously, maintaining the set temperature. In this regard, fuel will be consumed uneconomically, and you will have to pay considerable sums for it.

Nowadays, there is a steady tendency to abandon such solutions in favor of systems with forced circulation and a membrane expansion tank. Moreover, specialized stores offer a very wide selection of circulation pumps with different ratings for performance and pressure generated.

If a closed heating system is installed with a pump installed in it and sealed membrane expansion tank, then in order to constantly monitor the current parameters, a pressure gauge is installed on the coolant supply pipe. Besides him, this the so-called "security group" includes elements such as automatic or manual air vent and a safety valve that will operate if the pressure in the system exceeds the permissible threshold.

Autonomous heating in an apartment in a multi-storey building

In recent years, more and more residents of apartments in multi-storey buildings have decided to acquire one, since, despite the high cost of equipment and problems with legalization, the return on all costs is quite high.

The main advantages of autonomous heating of an apartment is that payment for heat will have to be made only in the winter, and only based on the energy consumed. In addition, it becomes possible to turn on the heating in the off-season, when the central system is not yet functioning or is already turned off.

However, when installing autonomous heating in an apartment, you need to remember that monitoring its serviceability and safe operation, including adjusting pressure and temperature, falls on the homeowner. In this regard, its installation and initial start-up should not be done independently - this process must be carried out by specialists who have special permission to work with gas equipment.

The main elements and units of an autonomous heating system are most often installed in the kitchen, since all communications necessary for its arrangement, such as gas and water, are connected to it.

Now we need to consider the question of what could cause instability of pressure in the autonomous heating system of an apartment.

• Most often, the pressure in the system can be reduced due to coolant leakage, which can occur at pipe connections, at radiator inlets or air vent. Therefore, if the pressure gauge shows a decrease in pressure in the system, it is necessary to immediately inspect the entire circuit, paying special attention to the connecting nodes. Any leak found must be repaired immediately. To do this, in some cases it is necessary to drain all the coolant from the system, and after repairs, fill it again.

• Damage to the expansion tank membrane - this can occur due to initially incorrect calculationthis element of the heating system. The membrane may stretch, crack, or rupture completely. When choosing an expansion tank, you need to remember that its volume must correspond to the actual parameters of the heating system being created. It is clear that you want to install the most compact devices to save space, but fighting against the laws of physics is pointless.

The appendix to the article will provide a method for calculating the volume of an expansion tank for an autonomous heating system, with the attached calculator.

• Air locks in the system may occur in the first days after it is filled with new coolant. Therefore, at this time, heating usually shows slightly reduced parameters, since air must be completely released from the system. To avoid the formation of plugs, it is recommended to fill the system with low water pressure, that is, very slowly.

To quickly get rid of air locks in radiators, on each of them you need to install Mayevsky crane, which designed specifically for this purpose.

• If the pressure drops after replacing old batteries with , then at first very active chemical reactions can occur inside them, during which gaseous substances are released. When this period passes and the free gases are completely released through air vents, the heating system will return to normal operation.

• The pressure in the circuit may also decrease due to failure of the boiler heat exchanger (rupture or dense overgrowth with insoluble deposits - when using untreated water as a coolant. In this case, you cannot cope with the problem on your own, and you will have to call a specialist.
• The heating temperature of the coolant is set too high, when it is not too low outside. In this case, the water in the heating circuit may even boil.
• There is a blockage in one of the pipe sections or in the connecting nodes, which inhibits the normal circulation of the coolant. In this case, the pressure in the narrowed area drops, and in the area before the blockage it will be increased, as a result of which depressurization of the circuit may occur there.
• Narrowing of pipeline clearances is usually observed in old heating systems that have been in operation for decades, resulting in thick layers of scale and dirt forming on the pipe walls due to poor-quality coolant.

A decrease in pressure due to this problem in an autonomous system occurs if the central heating system, which had been operating for a long time, was replaced with an autonomous one, but the radiators and pipes of the circuit remained old. And in order to avoid such troubles when setting up an autonomous system, it is recommended to completely dismantle the old circuit and install a new pipeline and radiators in its place.

In addition, it is necessary to fill the closed circuit with a coolant, which can be water that has undergone the necessary preparation - mechanical filtration and softening, that is, the removal of hardness salts that cause build-ups on the walls of the pipes.

So, in order for any heating system to function well and show its efficiency, the pressure in it must be normal. If this parameter is underestimated, there is insufficient temperature in the premises of the apartment or house. As the pressure in the system increases, its most vulnerable elements may not be able to withstand it. Therefore, it is recommended to immediately bring all system parameters back to normal, and install a pressure gauge in the heating circuit in order to promptly respond to deviations from the norm, identify the causes and eliminate them. If the apartment is connected to a central heating system, the presence of control and measuring instruments will help motivate complaints to the management company about the low quality of services provided.

To understand in more detail the causes of pressure instability in autonomous heating systems, with methods for identifying them and methods for eliminating them, watch a very informative video on this topic:

Video: What are the main causes of pressure instability in the heating system, and how to deal with it

Appendix: How to choose the correct volume of a membrane expansion tank for an autonomous heating system

The operating principle of a membrane tank and the algorithm for calculating its volume

There are no words, an autonomous closed-type system, with a completely sealed circuit, is much more convenient and efficient in operation. The required level of pressure in it is maintained, among other things, by installing an expansion tank of a special design.

The expansion tank is a sealed container divided by an elastic membrane into two compartments. One, let's call it water, is connected to the heating system circuit. The second is air, in which a certain pressure is preliminarily created.

As you can see, the design of this device is very simple. There are no special “mysteries” about the principle of its operation.

A- the heating system is not working, there is no excess coolant pressure in the circuit. Due to the pre-created pressure in the air compartment of the tank, the membrane completely (or almost completely) displaces the liquid from the water section.

b- the heating system is in working order. In the circuit, the operation of the circulation pump creates the nominal operating pressure of the coolant. In addition, due to heating, water expands, which also leads to an increase in the total volume of coolant and an increase in pressure.

Excess volume enters the water compartment of the expansion tank. Due to in the circuit in the working When the pressure exceeds the preset pressure in the air chamber, the elastic membrane changes its configuration, and at the same time the volume of each compartment changes. As a result, excess pressure in the circuit is leveled by increasing the pressure in the air compartment. The result is a kind of air damper that very successfully compensates for all theoretically possible pressure drops in the system, as a result why this indicator is always maintained at approximately the same nominal level.

V – if for some reason the pressure in the system has increased above the set limit (the pressure gauge needle has entered the “red zone”), the membrane has reached its extreme position, and the water compartment has nowhere to expand, the safety valve of the “safety group” should operate. (some models of expansion tanks have their own safety valve). Excess coolant is discharged into the drain, and the pressure returns to normal. But, frankly speaking, this can already be classified as an emergency situation - with a properly adjusted system, such extreme pressure rises should not exist in principle.

What volume of the expansion membrane tank is needed so as not to clutter up the space with the large dimensions of this product, but in at the same time, the system was guaranteed to work as correctly as possible. This can be calculated with the following formula:

Vb = Vc × Kt / F

Let's look at the values ​​included in the formula:

Vb- the required volume of the expansion tank.

Vс - the total volume of coolant in the heating system.

This parameter can be defined in different ways:

— Use the water meter to measure how much water is used to “refuel” the heating system.

— Calculate and then sum up the volumes of all elements of the heating system - boiler heat exchanger, pipes, radiators, underfloor heating circuits. It turns out a little more complicated, but most accurate.

Calculate the volume of the heating system? - no problem!

This parameter is often necessary when designing a system or when purchasing special antifreeze coolants. A special tool will help you make calculations with sufficient accuracy. heating system volume calculator , which you will find on the pages of our portal.

— For small autonomous heating systems, without much fear of making a mistake, you can be guided by a simple rule - 15 liters of coolant for every kilowatt of boiler power. This dependence will be included in the calculation calculator below.

Kt- coefficient that takes into account the volumetric expansion of the coolant when heated. This parameter does not change linearly, and can differ significantly for water used as a coolant and for non-freezing liquids. These are tabular values, and they are easy to find on the Internet. But the calculation program of the proposed calculator has already included the necessary values ​​of this coefficient for an average temperature of +70 degrees, as the most optimal for autonomous heating systems.

F- expansion tank efficiency coefficient. It can be calculated using the following formula:

F = (Pmax – Pb) / (Pmax + 1)

Pmax - maximum pressure in the heating system. It is determined by a number of factors, including the passport characteristics of the boiler and the features of the installed heat exchange devices. For example, for bimetallic batteries, the highest possible pressure and temperature values ​​are desirable, but with aluminum or steel panel batteries you should be much more careful. It is under this parameter that the safety valve of the “safety group” of the entire heating system is adjusted.

Pb- pressure previously created in the air chamber of the expansion tank. It can be set at the stage of tank production - and then this parameter is indicated in its passport. But more often it is possible to carry out inflation yourself - the air compartment is equipped with a nipple device, similar to what is installed on car wheels. That is, pumping and monitoring the created pressure can be easily done with a car pump with a pressure gauge.

As a rule, in small autonomous heating systems they are limited to pumping the air chamber of the expansion tank to a pressure of 1÷1.5 atmospheres (bar).

So, all the values ​​are known - you can substitute them into the formula and perform calculations. But it’s even easier to use our online calculator, which already includes all the necessary dependencies.

For heating networks in private houses and apartments, it is advisable to use boilers with closed coolant circulation, i.e. double-circuit. This design allows you to increase the pressure of the working fluid in the circuit.

High pressure in the heating system ensures safety and a higher boiling point of the coolant, therefore, the economic effect of the installation increases, and a decrease in pressure leads to problems in the system. Therefore, let’s look at why the pressure in the heating system of a double-circuit boiler drops and how to raise it.

The parameters of the boiler unit are monitored by measuring instruments - pressure gauges, main and additional. If a pressure gauge should be included in instrumentation and control measures, then choose models with electronic sensors.

Factors that affect the pressure inside the circuit:

• The impact of the coolant on the walls of the heating network elements;
• Height of laying pipes, hanging radiators and boiler unit;
• Design of main pipeline sections.

The pressure value for autonomous heating is not standardized. Acceptable values ​​of network parameters are calculated based on the data of a specific object:

• Boiler type, pipe characteristics (diameter, presence of reinforcement, etc.), type and number of radiators;
• Equipment installation location, circuit length;
• Number of floors of the house;
• Parameters and condition of the external water pipeline.

It is important to know! The pressure in the system is determined by the lowest value (usually at the most distant point). In forward and return, the pressure difference should be up to 0.3...0.5 atm to ensure normal circulation of the working fluid.

Reasons for pressure drop in the circuit:

1. Presence of leaks in the pipeline;
2. Malfunction of the boiler, cracks on the surface of the heat exchanger;
3. Malfunction of the membrane valve responsible for the safety of boiler equipment;
4. Failure of the expansion tank membrane;
5. Depressurization of the hot water supply circuit.

Leaks

Gaps are determined visually by pumping water into the pipeline to a predetermined level, and the cycle is stopped. The most susceptible to leaks are the joints of pipes, shut-off valves, radiator connections and the boiler itself.

One of the reasons for the pressure drop is a leak at the junction of the pipe and the radiator

Causes of leaks:

• The presence of corrosion on metal pipes and connections;
• Poor quality pipeline installation;
• Weakening of joints;
• Damage to the pipe due to mechanical impact.

Attention! The network should be inspected several times a season. If there are no puddles on the floor, this does not guarantee that there will be no leaks. A quality inspection includes not only inspection, but also walking around the pipes with a paper towel.

Troubleshooting

If the connection is damaged, replace the fitting or the connection itself. If a leak is detected (by a special scanner) in a pipe behind a decorative partition, wall or under the floor, it is necessary to dismantle the surfaces and make repairs.

Expansion tank and its bleeding

In a closed-type system, the cause of a drop in pressure in the circuit may be the failure of the expansion tank.

Symptoms:

• Frequent recharge of the system. If there is a need to additionally introduce coolant into the system at least once a week, without visible leaks, then the problem lies in the incorrect operation of the expansion tank;
• Dispersion of pressure gauge readings for different operating modes of the system. A sharp drop in coolant pressure in the system when using hot water supply also indicates a malfunction in the RB.

Pressure inside the expansion tank

To check its functionality, it is necessary to pump the tank and check that the pressure in it corresponds to the pressure in the heating system.

Sequence of pumping actions:

1. Close the shut-off valves (direct and return water supply);
2. Open the fitting, drain the water until the pressure in the boiler becomes zero;
3. Take readings on the expansion tank in the “open” position. The presence of condensation on the RB should not be observed;
4. Pump air into the RB until liquid stops flowing from the fitting. Allow the water to drain completely from the tank;
5. Release the air;
6. Repeat the procedure, keeping the pressure in the RB at 1.1...1.3 bar;
7. Open the shut-off valve;
8. Connect the coolant to the network. Set the pressure level to 1…1.1 bar.

Air injection

If there is no special pump for RB, you can use a regular bicycle pump.

Attention! Most manufacturers indicate the pressure value in the air compartment in the equipment passport. This greatly simplifies the procedure for selecting an expansion tank for the boiler.

If there is no expansion tank

The expansion tank for a home heating network is the second most important element (after the boiler). Water, when temperature changes, changes in volume. The volume inside the circuit is always constant, so an expansion tank is additionally connected to the circuit, where excess coolant can be diverted, i.e. acts as a compensator. Consequently, the RB is a safety device that prevents emergency situations - increased pressure, depressurization of pipes, etc.

The use of boiler equipment without an expansion tank is highly not recommended.

For stable operation, the pressure of the RB must correspond to the system volume, because when replacing radiators with pipes, the volume of coolant must be increased. At the same time, a too large RB will not maintain the operating pressure in the circuit.

The standard is an expansion tank designed for 120 liters of coolant in the circuit (typical two-room apartment). If the tank is too small, then the water will be discharged when heating and expanding the volume through a safety valve. When the boiler is turned off, when the liquid temperature decreases, starting the boiler will be impossible, because its volume, and, consequently, the pressure will be insufficient. In such cases, additional network feeding is necessary.

Competent calculation of the heating system

In private homes, it is necessary to take a responsible approach to the choice of expansion tank. If the volume is insufficient and the system does not start, there is a high probability of pipes freezing.

The installed equipment should be checked twice - immediately after installation and upon the onset of the cold season (at higher heating intensity).

Make-up tap

A common cause of pressure drop is a malfunction of the make-up valve. Causes:

• Loose tap connections. When opened, water will constantly flow into the drain, causing a voltage drop;
• The additional make-up valve is open. This position of the shut-off valves causes constant fluctuations in coolant pressure.

Today it is becoming less and less popular in private homes. Recently, closed-type heating schemes have been developing quite rapidly; it involves the use of gas equipment. Even if the installation was carried out correctly, a pressure drop may occur. Even a new system sometimes faces this problem, and there are many reasons for this.

Heating system design

The main equipment when installing a heating system is a boiler. It transfers the thermal energy released during fuel combustion. As a result, the coolant heats up. Depending on which boiler is used, different fuels can be used, namely:

• natural gas;
• coal;
• firewood;
• peat.

Today you can also find heating schemes where electricity acts as a heat source. However, this approach is quite expensive, although it is considered the safest. When installing heating equipment, you need to place an expansion tank in front of the boiler. It is necessary to balance water pressure.

Expansion tank operation

Pressure stabilization equipment has a membrane that is designed to separate air and working space. The function of the expansion tank is to accept the excess volume of water generated during the expansion process when exposed to elevated temperatures.

After the first task is completed, the water must be returned to the system. When the coolant expands, the pressure in appliances and pipes increases, and excess water flows into the tank. This provokes stretching of the membrane, as a result of which the volume of air decreases, which leads to an increase in pressure. When the water temperature drops, the pressure decreases, and the water that was previously in the tank is pushed out of it.

Air heating

The room is heated thanks to radiators located in each room. Depending on what material is used, the equipment can be:

• cast iron;
• aluminum;
• bimetallic;
• steel.

When considering heating equipment and systems, it is better to prefer bimetallic radiators, as they have excellent heat dissipation. Water enters heating appliances through a branched system. To ensure fast and uniform movement of water, systems where the coolant moves by gravity operate on the same principle. In this case, the air vent valve from the heating system acts as one of the important elements; this should also include pressure gauges, as well as shut-off valves.

Why does blood pressure drop?

In a closed heating system, pressure drops due to:

• presence of air;
• water leaks;
• use of aluminum radiators.

If we are talking about a coolant leak, then it can occur in those places where the elements were connected, and there are also batteries and Water can also be lost in the area of ​​​​corroded elements. Sometimes a torn membrane causes a coolant leak.

To check for leaks, press the nipple located on top of the tank. If air and water are released, then we can safely talk about a coolant leak. Otherwise, only air is released. After checking the entire line, no leaks may be detected, but the problem is due to other reasons.

The reason for the pressure drop is the presence of air

Quite often, heating equipment and systems experience a drop in pressure. This may be indicated by the presence of air. If plugs appear, the technical requirements for the process of filling the system with water may have been violated. Sometimes the coolant undergoes poor preparation, as a result of which a certain amount of dissolved air remains in it.

The coolant may be air-filled, in which case suction occurs, and the connections remain not so tight. Sometimes it happens that the air release valve from the heating system does not work correctly; it may be poorly adjusted or clogged. Each of these problems can cause noise in the system. This phenomenon cannot be called normal, in addition, it is harmful to heating.

Consequences of a drop in system pressure

If air accumulates in heating appliances, this can cause noise in the pipelines, which weakens welds and threaded connections. If you have already figured out why it is falling, then you should also think about what consequences this can lead to.

For example, if it is impossible to ventilate the system, it cannot be adjusted; sometimes this causes the water circulation to stop in individual risers and batteries. The consequence may also be defrosting of the system. If the movement does not stop completely, the efficiency will decrease and fuel consumption will increase. If the pressure in the heating system of a private home drops, damage to the pump impeller will occur, because the load will increase.

What should the pressure be?

If you are also thinking about the question of what pressure should be in the heating system. If the circuit is open, then the pressure in the expansion tank will be equal to atmospheric pressure, while the pressure gauge will show a value of 0 bar. Immediately after the pumping equipment, there will be a pressure in the pipeline that will be equal to the pressure that the unit is capable of developing. If we are talking about a closed system, then everything is much more complicated.

To improve operating efficiency and prevent air from entering the water, the static component is artificially increased. There is a simplified method that helps determine the pressure in such a circuit. It is necessary to determine the elevation difference by finding the high and low points of the network. This value is multiplied by 0.1. Calculations will allow you to determine the static pressure; 0.5 should be added to this figure, this will allow you to calculate the required pressure in the system. In practice, 0.5 bar may not be enough. For this reason, it is generally accepted that in a closed system the pressure value is 1.5 bar, but during operation this value increases to 2 bar.

Once you know what pressure should be in the heating system, you should know that as it increases, the operation of the circuit improves. But this figure is limited by the characteristics of the equipment. Household heat generators can operate at only 3 bar, but you can also find very weak devices that are designed for only 1.6 bar. Therefore, when making adjustments, it is necessary to achieve a value 0.5 bar lower than the value specified in the boiler equipment passport. Otherwise, the pressure relief valve will operate.

Purpose and types of air release valve

If you are wondering why the pressure in the heating system drops, you should first use the air release valve. In industrial boiler houses, before entering the boiler, water goes through the stage of removing dissolved air. If initially it contained up to 300 g/m3, then later it becomes suitable and corresponds to 1 g/m3. But such technologies are quite expensive, so they are not used in private housing construction.

If you are also concerned about why the pressure in the heating system drops, then the coolant may be oversaturated with air. This prevents the circulation of fluid, causing some areas to overheat while others cool down. To solve the problem described, air vents are used, which can be automatic or manual. Each type is installed in different places where there may be a risk of air accumulation. The so-called valves can have radiator and traditional designs. As for the configuration, it can be angular or straight.

How to prevent air from entering the system

In order not to face the question of why the pressure in the heating system drops during operation, it is important to put the equipment into operation correctly. Before starting, an inspection of the system as a whole and each connection separately is carried out. The system must be pressure tested; for this, the compressor applies a pressure 25% higher than the operating pressure. If there is no significant decrease in pressure within 20 minutes, then the system is configured correctly and can be put into operation.

But if the pressure in the heating system constantly drops, then it is important to find the leak and fix it. A characteristic whistle may indicate such a problem. It is necessary to fill the system with cold water, this should be done gradually. Before starting, all taps are opened to allow air to bleed out. The plugs in the batteries should be unscrewed, this will remove air from the system. If the design allows, the valve should be opened to ventilate the circuit.

“Why does the pressure in the heating system drop and how can I get the pressure back?” – if you are interested in this question, then some trouble has happened to your heating system. But don't worry, this can be fixed. Now we will look at the reasons for the pressure drop effect and ways to eliminate such a failure.

5 most likely causes of pressure loss

The main reasons for the drop in pressure in the system are:

1. 1. Depressurization of wiring elements - pipes and radiators. In this case, the system loses coolant and pressure.
2. 2. A breakdown in the expansion tank, which can no longer act as a compensator and maintain the specified pressure.
3. 3. Air bubble (pocket) in the radiator or heat pipe. After the release of such a bubble, the pressure may drop by several tenths or even whole parts of atmospheric pressure.
4. 4. Defect in the integrity of the heat exchanger in the heating boiler. Your heating device loses coolant, and with it pressure.
5. 5. Depressurization of the valve that closes the coolant discharge line.

As you can see: the main reason for loss of pressure is the depressurization of one or more elements. Therefore, to increase the pressure, it is necessary, firstly, to eliminate the leak, and secondly, to add coolant to the system. And if in the case of a drain valve these works do not require much effort - the user closes the shut-off assembly with a “light movement of the hand”, then with other incidents you will have to tinker longer. And now we will teach you what to do when the pressure in the boiler drops.

How to determine the culprit of pressure loss?

So, the most important thing is to understand what exactly led to the loss of pressure. To do this, follow the algorithm. First, take a regular paper napkin and wipe all the fittings. At the same time, after each joint you need to carefully inspect the napkin to see if there is a wet spot on it. If there is, the reason has been found. If not, you need to move on.

Secondly, we spread dry newspapers under the radiators and wipe all the pipes with the same blotting cloth. If a wet spot is found, the leak has been localized. If not, move on to the next point. Thirdly, we measure the pressure in the expansion tank and pump it up. This can be done with a regular bicycle pump and a factory pressure gauge. The pressure no longer drops - congratulations, you have solved the problem with the air pocket. But if after pumping the pressure drops sharply or does not deviate from the original value, the membrane in your hydraulic tank is torn. If the pressure drops smoothly, we move on.

Fourthly, we turn off the boiler and close the valves on the pressure and return pipes, cutting off the heater from the system. We measure the pressure for an hour - if it does not drop, then the water heater itself, or rather its heat exchanger, is to blame. Moreover, in the boiler Navien or any other dual-circuit installation, the air vent or pressure relief valve may malfunction. Fifthly, we check the shut-off valve on the outlet for discharging the coolant into the sewer. If it is weakened, it needs to be blocked or replaced (it is better to insert another one downstream). After locating the leak or determining the cause, you can begin to eliminate it. How to do it? We'll talk about this below.

What to do to eliminate depressurization of pipes and radiators

This problem can be solved simply: we apply patches to the cracks in the pipes, and tighten the loose fittings, restoring the tightness of the joints. Therefore, if the reason why the pressure in a gas boiler drops is a leaky pipe or a poorly tightened joint, then you will spend much less time eliminating such a defect than finding the location of the leak.

A patch for a polymer pipe is cut out from a piece of reinforcement and glued to the leak site using a special composition adapted for polypropylene or polyethylene. A copper pipe can be soldered, a steel pipe can be welded. If you don’t have glue, a welding machine, or a soldering iron at hand, take two screw clamps and a rubber patch cut from an old bicycle or car inner tube. Press the patch onto the crack and secure the pipes to the body with clamps.

A chip or crack on the battery can be removed by welding or soldering. If you do not have the skills or welding equipment, use epoxy “liquid welding” compound, which is glued to the leak and pressed to the pipe with a clamp or screw clamp. It’s even easier to deal with a leaking joint. The collet clamps are tightened until there is a characteristic creaking sound, signaling the beginning of deformation of the pipe body. With threaded fittings, do the opposite - unscrew the lock nut, screw several turns of FUM or silicone-impregnated tow onto the pipe and tighten the clamping nut to its old place.

How to repair a hydraulic tank - instructions for everyone

Usually complaints about this unit begin with the words: “I raise the pressure, but nothing happens.” Moreover, the expansion tank itself can stand alone or be part of the boiler. As we said above: the lack of response to pumping the compensator is the first sign of a defect in its membrane. What to do in this case? Of course, change this membrane:

• We turn off the valve under the tank, cutting off this unit from the heating system.
• We dismantle the tank by twisting it from the valve. Moreover, under it you need to place an empty basin or bucket in advance, into which the rest of the water contained in the tank will be drained. Attention! The water can be hot, so dismantling should be done an hour after closing the lower valve.
• We open the compensator housing by unscrewing the nuts on the flange. In this case, it is better to tighten the nuts sequentially - 2-3 turns for each, in order to avoid distortions. When assembling the flange assembly, use the same diagram.
• We assemble the tank and put it in place, screwing it onto the valve. Pay attention to American fittings - they make it easier to install and dismantle any dismountable connection in the heating system. If there is a regular fitting under your tank, change it to an American one.
• We inflate the compensator using a bicycle pump connected to the nipple in the upper part of the body. The optimal pressure in this case is 1.5-3 atmospheres.
• Open the valve under the tank and add the required volume of water to the system.

Using this scheme, you can only repair a collapsible tank. If your compensator cannot be repaired, buy a new one of the same volume. Proceed in a similar way if the tank is built into a heating device. This advice is valid not only for brand boilers Navien, but also for equipment from other manufacturers.

How to bleed an air pocket from a radiator without losing pressure

First you need to determine the location of the air pocket. It is easily localized by the characteristic gurgling sound that accompanies the flow of coolant through the airy area. After this, it would be a good idea to record the initial pressure by reading the pressure gauge. We will focus on this indicator before raising the pressure in the boiler after eliminating the air bubble.

Turn off the boiler or circulation pump (if the latter is not included in the heating device). Pressure equipment generates a force in the heating network, providing circulation, and when etching an air pocket, this force will be unnecessary.

Next, place a bucket or basin under the Mayevsky faucet of the air-filled battery and turn its valve in the direction of the arrow in the desired direction. Air will first flow through the hole in the faucet (with a hiss, like from a deflated balloon), and then water will drip. But do not rush to close the tap - after a small portion of water, air will come out of the battery again. Turn off the valve only after making sure that only water comes out of the tap.

Then read the current pressure value on the pressure gauge (it will be less than the initial one) and open the valve for supplying water to the distribution system from the water supply, monitoring the readings of the pressure gauge. As soon as they approach the starting mark (we wrote it down earlier), close the water supply valve. Now turn on the boiler (pump) and listen to the noise in the radiators. If you hear gurgling or gurgling, do all the above-described manipulations from the very beginning until the gurgling sounds completely disappear as water moves through the pipes and radiators.

What to do if the source of the problem is the boiler?

If the source of the problem is the boiler, you will most likely have to call a technician from a service company or service center. Only specially trained people can repair gas equipment. After all, the consequences of errors in this case lead to disasters on a local scale. The slightest leak in gas equipment (with the ventilation system not working) leads to an increase in the concentration of the air-gas “cocktail” to an explosive level.

Moreover, even a small spark in the socket is enough to activate the explosion. Therefore, repairing a gas boiler yourself or even attempting to do so will lead to very sad consequences. As a result, if the drop in pressure in the system does not bother you very much, wait until the end of the heating period and call a boiler technician. If you do not want or cannot tolerate this disgrace, drain the water from the system and, again, call a technician. We do not recommend self-repair of the boiler with replacement of the heat exchanger, controller or expansion tank under any circumstances.