Pressure regulation in the heating network. Neutral points.

The pressure in the system must vary within acceptable limits; to ensure the reliability of the heating system, the pressure in the return line is of particular importance. At high blood pressure in the return network, the pressure in the heating system connected according to a dependent circuit increases. When the pressure in the network is low, circulation is disrupted.

To limit pressure fluctuations in the system, pressure is measured at one or several points in the network depending on the operating modes of the system. These points are called adjustable pressure points .

If the pressure is maintained constant at these points both during static and dynamic operating modes of the system, these points are called neutral . Constant pressure supported by automatic control device.

Neutral points can be installed:

1) at the suction pipe network pump. This place point installation is used in small systems, when static pressure= pressure at the suction pipe of the mains pump, the pressure of the mains pump remains constant during dynamic operation.

2) on the jumper of the network pump. It is used in branched networks, but with calm terrain. During operation of the network pump, water circulates in the jumper; the pressure drop in the jumper = pressure drop in the network.

The pressure at the neutral point is used as a pulse, with the help of which the amount of make-up is regulated; when the pressure in the system drops and the pressure at the neutral point decreases, the opening of the make-up regulator increases and the water supply by the make-up pump increases. As the pressure in the network increases, the pressure at the neutral point increases, the make-up regulator closes, the water supply decreases; if, after closing the make-up regulator, the pressure in the network continues to increase, the drain valve opens and the pressure in the system is restored. Adjustable valves 1 and 2 are also used to regulate the pressure in the network. A partial increase in pressure at the suction pipe of the network pump leads to an increase in pressure in the network. When valve 1 is completely closed, the circulation in the jumper stops and the pressure at the suction pipe becomes = the pressure at the neutral point. Piezometric graph moves as high as possible. When valve 2 is completely closed, the pressure at the discharge pipe of the network pump becomes = the pressure at the neutral point, the piezometric graph moves down as much as possible.

3) In case of difficult terrain or when connecting to heating networks of buildings high number of storeys it is necessary to establish several neutral points. (Fig.) The system in this case is divided into zones with independent mode, the main neutral point O 1 is fixed on the jumper of the network pump. Static pressure S 1 is maintained using the make-up regulator and the bottom zone make-up pump. Additional neutral point O 2 is fixed on return line, in the upper zone. Constant pressure in the upper zone is maintained by the RDDS (up to itself). If circulation in the network stops and pressure drops in the upper zone, the RDDS closes. Closes at the same time check valve on the supply line. The upper zone is hydraulically isolated from the lower. The upper zone is fed using the feed regulator and feed pump 2 according to the pressure pulse at point O 2 .

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Heat supply design of a large multi-storey building is a complex mechanism that can function effectively provided that many parameters of the elements included in it are observed. One of them is considered working pressure in the heating system. Not only the quality of heat transferred to the air, but also the reliable and safe operation of heating equipment depends on this value.

Pressure in the heating system multi-storey buildings must meet certain requirements and standards established and prescribed in SNiPs. If there are deviations from the required values, serious problems may arise, including the inability to operate the heating system.

Why is there pressure in the system?

Many consumers are interested in why there is pressure in the heating system and what depends on it. The fact is that it has a direct impact on the efficiency and quality of heating the premises of the house. Thanks to the working pressure it is possible to achieve best performance heat supply system due to the guaranteed flow of coolant into pipelines and radiators in each apartment of a multi-story building.

Types of working pressure in heating structures

The pressure in the heating design of a multi-story building is of several types:

1. The static pressure of a heating system is an indicator of the force with which the volume of liquid, depending on the height, acts on pipelines and radiators. In this case, when performing calculations, the pressure level on the surface of the liquid is zero.
2. Dynamic pressure occurs during the movement of coolant liquid through pipes. It affects the pipeline and radiators from the inside.
3. The permissible (maximum) operating pressure in the heating system is a parameter for the normal and trouble-free functioning of the heat supply structure.

Normal pressure indicators

In all domestic multi-storey buildings, built both several decades ago and in new buildings, the heating system operates according to closed schemes using forced movement of the coolant. Operating conditions are considered ideal when the heating system operates under a pressure of 8-9.5 atmospheres. But in old houses, a loss of pressure may be observed in the heat supply structure, and accordingly the pressure indicators may drop to 5 -5.5 atmospheres. Read also: "".

When choosing pipes and radiators to replace them in an apartment located in multi-storey building, initial indicators should be taken into account. Otherwise, the heating equipment will operate unstably and even complete destruction of the heating supply circuit, which costs a lot of money, is possible.

What pressure should be in the heating system of a multi-storey building is dictated by standards and other regulatory documents.

As a rule, it is impossible to achieve the required parameters according to GOST, since performance indicators are influenced by various factors:

1. Equipment power required for supplying coolant. The pressure parameters in the heating system of a high-rise building are determined at heating stations, where the coolant is heated for supply through pipes to the radiators.
2. Equipment condition. Both dynamic and static pressure in the heat supply structure are directly affected by the level of wear of boiler room elements such as heat generators and pumps. The distance from the house to the heating station is of no small importance.
3. Diameter of pipelines in the apartment. If, when carrying out repairs with their own hands, the apartment owners installed pipes larger diameter than in the inlet pipeline, a decrease in pressure parameters will occur.
4. Location separate apartment in a high-rise building. Of course, the required pressure value is determined in accordance with the norms and requirements, but in practice a lot depends on what floor the apartment is on and its distance from the common riser. Even when living rooms are located close to the riser, the pressure of the coolant in corner rooms is always lower, since there is often an extreme point of the pipelines.
5. Degree of wear of pipes and batteries. When the elements of the heating system located in the apartment have served for decades, some reduction in equipment parameters and performance cannot be avoided. When such problems occur, it is advisable to initially replace worn pipes and radiators and then emergency situations will be avoided.

Test pressure

Residents apartment buildings It is known how utility services, together with specialists from energy companies, check the coolant pressure in the heating system. Usually they are before heating season coolant is supplied to pipes and batteries under pressure, the value of which approaches critical levels.

They use pressure when testing the heating system in order to test the performance of all elements of the heat supply structure in extreme conditions and find out how efficiently heat will be transferred from the boiler room to a multi-story building.

When served test pressure heating systems often its elements come in emergency condition and require repairs, as worn-out pipes begin to leak and holes form in the radiators. Timely replacement of the outdated one will help to avoid such troubles. heating equipment in the apartment.

During testing, parameters are monitored using special devices, installed in the lowest (usually a basement) and the highest ( attic space) points of the high-rise building. All measurements taken are subsequently analyzed by specialists. If there are deviations, it is necessary to detect problems and correct them immediately.

Checking the tightness of the heating system

To ensure effective and reliable operation heating systems, not only check the coolant pressure, but also test the equipment for leaks. How this happens can be seen in the photo. As a result, you can monitor the presence of leaks and prevent equipment breakdown at the most crucial moment.

The tightness test is carried out in two stages:

• test using cold water. Pipelines and batteries in a multi-story building are filled with coolant without heating it, and pressure readings are measured. Moreover, its value during the first 30 minutes cannot be less than the standard 0.06 MPa. After 2 hours, losses cannot be more than 0.02 MPa. In the absence of gusts, the heating system of the high-rise building will continue to function without problems;
• test using hot coolant. The heating system is tested before heating season. Water is supplied under a certain pressure, its value should be the highest for the equipment.

To achieve the optimal pressure value in the heating system, it is best to entrust the calculation of its arrangement to specialist heating engineers. Employees of such companies can not only carry out the appropriate tests, but also wash all its elements.

Testing is carried out before starting up the heating equipment, otherwise the cost of an error can be too expensive, and, as is known, it is quite difficult to eliminate an accident at sub-zero temperatures.

The pressure parameters in the heat supply scheme of a multi-storey building determine how comfortable you can live in each room. Unlike their own home ownership with an autonomous heating system in a high-rise building, apartment owners do not have the opportunity to independently adjust the parameters heating structure, including temperature and coolant supply.

But the tenants multi-storey buildings if desired, they can install such measuring instruments like pressure gauges in the basement and in case of the slightest deviation in pressure from the norm, report it to the relevant utility services. If, after all the steps taken, consumers are still unhappy with the temperature in the apartment, perhaps they should consider organizing alternative heating.

As a rule, the pressure in the pipelines of domestic multi-story buildings does not exceed the maximum standards, but still, installing an individual pressure gauge will not be superfluous.

Connection diagrams for heating systems are dependent And independent. IN dependent circuits The coolant in the heating devices comes directly from the heating network. The same coolant circulates both in the heating network and in the heating system, therefore the pressure in heating systems is determined by the pressure in the heating network. In independent schemes, the coolant from the heating network enters the heater, in which it heats the water circulating in the heating system. Heating system and heating network separated by the heating surface of the heat exchanger and thus hydraulically isolated from each other.

Any scheme can be used, but the type of connection of heating systems must be chosen correctly to ensure their reliable operation.

Independent connection diagram for heating systems

Applicable in the following cases:

1. to connect tall buildings(more than 12 floors), when the pressure in the heating network is not enough to fill heating devices on upper floors;
2. for buildings that require increased reliability of heating systems (museums, archives, libraries, hospitals);
3. buildings with premises where access to outside service personnel is undesirable;
4. if the pressure in the return pipeline of the heating network is higher than the permissible pressure for heating systems (more 60 m.water column or 0, 6 MPa).

RS - expansion vessel, RD - pressure regulator, RT - temperature regulator: OK - check valve.

Network water from the supply line enters the heat exchanger and heats the water of the local heating system. Circulation in the heating system is carried out circulation pump, which ensures a constant flow of water through heating devices. The heating system may have an expansion vessel that holds a supply of water to make up for leaks from the system. It is usually installed at the highest point and connected to the return line to the suction of the circulation pump. At normal operation Heating system leaks are insignificant, which makes it possible to fill the expansion tank once a week. Make-up is made from the return line via a jumper, made for reliability with two taps and a drain between them, or using a make-up pump if the pressure in the return line is not enough to fill the expansion vessel. A flow meter on the make-up line allows you to take into account water withdrawal from the heating network and make payments correctly. The presence of a heater allows for the most rational control mode. This is especially effective at positive outdoor temperatures and at central quality regulation in the break zone of the temperature graph.

The presence in the circuit of heaters, pump, expansion tank increases the cost of equipment and installation, and increases the size heating point, and also requires additional costs for maintenance and repairs. The use of a heat exchanger increases specific consumption network water to the heating point and causes an increase in the temperature of the return network water by 3÷4ºС on average for the heating season.

Dependent connection diagrams for heating systems.

In this case, heating systems operate under pressure close to the pressure in the return pipe of the heating network. Circulation is ensured by the pressure difference in the supply and return pipelines. This difference ∆Р must be sufficient to overcome the resistance of the heating system and thermal unit.

If the pressure in the supply pipe exceeds the required level, it must be reduced by a pressure regulator or throttle washer.

Advantages dependent circuits compared to independent:

• simpler and cheaper subscriber input equipment;
• a larger temperature difference in the heating system can be obtained;
• reduced coolant flow,
• less pipeline diameters,
• operating costs are reduced.

Flaws dependent schemes:

• rigid hydraulic connection of the heating network and heating systems and, as a result, reduced reliability;
• increased complexity of operation.

There are the following methods of dependent connection:

Scheme of direct connection of heating systems

She is the simplest scheme and is used when the temperature and pressure of the coolant coincide with the parameters of the heating system. To join residential buildings at the subscriber input the temperature of the network water should not exceed 95ºС, For industrial buildings- no more 150ºС).

This circuit can be used to connect industrial buildings and residential sector to boiler houses with cast iron hot water boilers, operating at maximum temperatures 95 - 105ºС or after TsTP.

Buildings are connected directly, without mixing. It is enough to have valves on the supply and return pipelines of the heating system and the necessary instrumentation. The pressure in the heating network at the connection point must be less than permissible. Have the least strength cast iron radiators, for which the pressure should not exceed 60 m.water column Sometimes flow regulators are installed.

Scheme with elevator

It is used when it is necessary to reduce the temperature of the coolant for heating systems according to sanitary and hygienic indicators (for example, with 150ºС to 95ºС). For this purpose water jet pumps are used ( elevators). In addition, the elevator is a circulation stimulator.

Most residential and public buildings are connected under this scheme. The advantage of this scheme is that it low cost and, most importantly, high degree elevator reliability.

RDDS - pressure regulator upstream; SPT is a heat meter consisting of a flow meter, two resistance thermometers and an electronic computing unit.

Advantages elevator:

• simplicity and reliability of operation;
• no moving parts;
• does not require constant monitoring;
• performance can be easily adjusted by selecting the diameter of the replacement nozzle;
• long service life;
• constant mixing coefficient with fluctuations in pressure drop in the heating network (within certain limits);
• due to the high resistance of the elevator, it increases hydraulic stability heating network.

Flaws elevator:

• low efficiency equal to 0.25÷0.3, therefore, to create a pressure difference in the heating system, it is necessary to have an available pressure of 8÷10 times larger;
• constancy of the elevator mixing coefficient, which leads to overheating of the premises during the warm period of the heating season, because it is impossible to change the ratio between the amounts of network water and mixed water;
• dependence of pressures in the heating system on pressures in the heating network;
• at emergency shutdown heating network stops water circulation in heating installation, resulting in a risk of water freezing in the heating system.

Circuit with a pump on a jumper

Applicable:

1. in case of insufficient pressure drop at the subscriber input;
2. with sufficient pressure difference, but if the pressure in the return pipe exceeds the static pressure of the heating system by no more than 5 m water st.;
3. the required power of the heating unit is high (more than 0.8MW) and goes beyond the capacity of manufactured elevators.

In the event of an emergency shutdown of the heating network, the pump circulates water in the heating installation, which prevents its defrosting within a relatively short period of time. long period(8 - 12 hours). This pump installation scheme ensures the lowest energy consumption for pumping, because the pump is selected according to the flow rate of mixed water.

When installing mixing pumps in residential and public buildings It is recommended to use silent foundationless pumps of the TsVTs type with a capacity of 2,5 to 25 t/hour. More high reliability have imported pumps, which are currently beginning to be used at heating points.

Replacing elevators with pumps is a progressive solution, because... allows to reduce the consumption of network water by approximately 10% and reduce the diameter of pipelines.

The disadvantage is the noise of the pumps (foundation) and the need for their maintenance.

The scheme is widely used for central heating stations.

Diagram with a pump on the supply line.

This scheme is used when there is insufficient pressure in the supply line, i.e. when this pressure is lower than the static pressure of the heating system (in high-rise buildings).

The design pressure of the pump must correspond to the missing pressure, and the performance is selected equal to the total water flow in the heating installation. The filling of the heating system is ensured by the pressure regulator RD, and the pressure difference between the supply and return lines is throttled in the control valve on the jumper (DK - throttle control valve). With its help, the required mixing ratio is established. In case of unstable hydraulic conditions of the heating network, the check valve on the supply line is replaced with a downstream pressure regulator (RDPS), to which a pulse is applied when the booster pumps are stopped.

Scheme with a pump on the return line

This scheme is used when it is unacceptable high blood pressure in the return line. It is most often used at the end sections, when the return pressure is high and the differential is insufficient. The pumps operate in the “mix-pump” mode, which reduces the pressure in the return line and increases the difference between the supply and return pipelines. A pressure regulator on the return line is necessary in static mode, when the pumps operate as circulation pumps. In this case, the pressure regulators on the supply and return lines are forcibly closed, and the subscriber input is cut off from the heating network. To regulate the reduced pressure in the return line, a throttle control valve (DC) is installed on the jumper, with the help of which the mixing coefficient is regulated.

When using pump mixing at heating points, it is necessary to install a backup pump along with the working pump. In addition, increased reliability in power supply is required, since turning off the pump leads to the flow of overheated water from the heating network into the local heating system, which can lead to damage. In the event of an emergency in the heating network, in order to save water in the local heating system, a check valve is additionally installed on the supply line and a pressure regulator on the return pipeline.

Schemes with pump and elevator

The noted disadvantages are eliminated in schemes with an elevator and a centrifugal pump. In this case, failure centrifugal pump leads to a decrease in the mixing coefficient of the elevator, but will not reduce it to zero, as with pure pump mixing. These schemes are applicable if the pressure difference in front of the elevator cannot provide the required mixing coefficient, i.e. she's smaller 10÷15 m water Art., but more 5 m water Art. In existing heating networks, such zones are extensive. The schemes allow for stepwise temperature regulation in the zone high temperatures outside air. Installing a centrifugal pump with a normally operating elevator when the pump is turned on allows you to increase the mixing ratio and reduce the temperature of the water supplied to the heating system.

There are 3 possible pump activation schemes in relation to the elevator:

Scheme 1.

Scheme 1 is used if the pressure loss in a stopped pump is small and cannot significantly reduce the mixing ratio of the elevator. If this condition is not met, scheme 2 is used.

Scheme 2

For small pressure drops, it is necessary to close valve 1 in scheme 3.

Scheme 3

Another scheme that can provide two-stage control in an area of ​​high outside air temperatures is a two-elevator scheme.

Scheme 4

Shutting down one elevator leads to a decrease in the consumption of network water and an increase in the mixing coefficient. Each elevator can be designed for 50% of water flow, or one for 30-40%, and the other for 70-60%.

Elevators have been developed with adjustable nozzle. By introducing a needle, the cross-section of the nozzle and, accordingly, the mixing coefficient change. This allows during the warm period to reduce the consumption of network water and increase the mixing coefficient, maintaining constant flow in the heating system. No matter how perfect the elevator design is, the error and maneuverability when dependent connection this will not increase the price. IN recent years In connection with the increase in the construction of high-rise buildings, the use of independent schemes for connecting heating systems through water-to-water heaters is growing. Go to independent circuits allows for widespread use of automation and increased reliability of heat supply. It is advisable to use independent accession heating systems in networks with direct water supply, which eliminates the main drawback of these systems, namely, the low quality of water used for hot water supply.

5.5. Piezometric graph

When designing and operating branched heating networks, a piezometric graph is widely used, on which the terrain, the height of connected buildings, and the pressure in the network are plotted on a specific scale; it is easy to determine the pressure () and available pressure (pressure drop) at any point in the network and subscriber systems.

In Fig. 5.5 shows the piezometric graph of a two-pipe water heating system and circuit diagram systems. Level I - I, which has a horizontal mark of 0, is taken as the horizontal plane of pressure reference; , – network supply line pressure graph; , – graph of pressures of the return line of the network; – total pressure in the return collector of the heat supply source – pressure developed by the network ohm 1; N st – the total pressure developed by the make-up ohm, or, what is the same, the total static pressure of the heating network; N To – full head at point TO on the discharge pipe a 1; – loss of network water pressure in a heat treatment plant III;

Nn 1 – total pressure in the supply manifold of the heat supply source: . Available supply water pressure on the collectors . Pressure at any point in the heating network, for example at the point 3, denoted as follows: – total pressure at a point 3 network supply line; – full head at point 3 network return line.

If the geodetic height of the pipeline axis above the reference plane at this point in the network is equal to Z 3, then the piezometric pressure at the point 3 supply line, and the piezometric pressure in the return line. Available head at point 3 heating network is equal to the difference between the piezometric pressures of the supply and return lines of the heating network or, which is the same thing, the difference in total pressure .

Available pressure in the heating network at the subscriber connection point D:

Pressure loss in the return line in this section of the heating network

When calculating hydraulically steam networks the profile of the steam pipeline can be ignored due to the low steam density. The pressure drop across the steam pipeline section is taken to be equal to the pressure difference at the end points of the section. Correct definition pressure loss, or pressure drop in pipelines, is of paramount importance for choosing their diameters and organizing a reliable hydraulic mode of the network.

To prevent erroneous decisions, before carrying out hydraulic calculation water heating network, outline the possible level of static pressures, as well as the lines of the maximum permissible maximum and minimum hydrodynamic pressures in the system and, guided by them, select the nature of the piezometric graph from the condition that under any expected operating mode, the pressures at any point of the heating supply system do not go beyond the permissible limits. Based on the technical and economic calculation, it is only necessary to clarify the values ​​of pressure losses without going beyond the limits outlined according to the piezometric graph. This design procedure allows us to take into account technical and economic features of the designed object.

The main requirements for the pressure regime of water heating networks from the conditions of reliable operation of the heat supply system are reduced to the following:

1) it is not allowed to exceed permissible pressures in the equipment of the source, heating network and subscriber installations. Permissible excess (above atmospheric) in steel pipelines and fittings of heating networks depends on the range of pipes used and in most cases is 1.6–2.5 MPa;

2) ensuring excess (above atmospheric) pressure in all elements of the heat supply system to prevent cavitation (network, make-up, mixing) and protect the heat supply system from air leaks. Failure to comply with this requirement leads to corrosion of the equipment and disruption of water circulation. The minimum value of excess pressure is 0.05 MPa (5 m of water column);

3) ensuring that the network water does not boil during the hydrodynamic mode of the heating system, i.e. when circulating water in the system.

At all points of the heat supply system must be maintained in excess of saturated water vapor at maximum temperature network water in the system.

Working pressure in the heating system - the most important parameter, on which the functioning of the entire network depends. Deviations in one direction or another from the values ​​specified in the project not only reduce the efficiency of the heating circuit, but also significantly affect the operation of the equipment, and special cases may even disable it.

Of course, a certain pressure drop in the heating system is determined by the principle of its design, namely the difference in pressure in the supply and return pipelines. But if there are larger spikes, immediate action should be taken.

1. Static pressure. This component depends on the height of the column of water or other coolant in the pipe or container. Static pressure exists even if the working medium is at rest.
2. Dynamic pressure. Represents the force that acts on internal surfaces systems during the movement of water or other medium.

The concept of maximum operating pressure is distinguished. This is the maximum permissible value, exceeding which is fraught with destruction individual elements networks.

What pressure in the system should be considered optimal?

Table of maximum pressure in the heating system.

When designing heating, the coolant pressure in the system is calculated based on the number of floors of the building, total length pipelines and number of radiators. As a rule, for private houses and cottages optimal values The medium pressure in the heating circuit is in the range from 1.5 to 2 atm.

For apartment buildings up to five floors connected to the system central heating, the network pressure is maintained at 2-4 atm. For nine- and ten-story buildings, a pressure of 5-7 atm is considered normal, and in higher buildings - 7-10 atm. The maximum pressure is recorded in the heating mains through which the coolant is transported from boiler houses to consumers. Here it reaches 12 atm.

For consumers located at different heights and at different distances from the boiler room, the pressure in the network has to be adjusted. To reduce it, pressure regulators are used, to increase it - pumping stations. However, it should be taken into account that a faulty regulator can cause an increase in pressure in certain areas of the system. In some cases, when the temperature drops, these devices can completely shut off the shut-off valves on the supply pipeline coming from the boiler plant.

To avoid such situations, the regulator settings are adjusted so that complete shutoff of the valves is impossible.

Autonomous heating systems

Expansion tank in an autonomous heating system.

In the absence district heating In houses, autonomous heating systems are installed, in which the coolant is heated by an individual low-power boiler. If the system communicates with the atmosphere through an expansion tank and the coolant circulates in it due to natural convection, it is called open. If there is no communication with the atmosphere, and the working medium circulates thanks to the pump, the system is called closed. As already mentioned, for normal functioning In such systems, the water pressure in them should be approximately 1.5-2 atm. This low figure is due to the relatively short length of pipelines, as well as a small number of instruments and fittings, which results in relatively low hydraulic resistance. In addition, due to the low height of such houses, the static pressure in the lower sections of the circuit rarely exceeds 0.5 atm.

At the stage of launching the autonomous system, it is filled with cold coolant, maintaining a minimum pressure in closed heating systems of 1.5 atm. There is no need to sound the alarm if, some time after filling, the pressure in the circuit drops. Pressure loss in in this case are caused by the release of air from the water, which dissolved in it when filling the pipelines. The circuit should be de-aired and completely filled with coolant, bringing its pressure to 1.5 atm.

After heating the coolant in the heating system, its pressure will increase slightly, reaching the calculated operating values.

Precautions

Device for measuring pressure.

Since when designing autonomous systems In heating systems, in order to save money, a small safety margin is laid down; even a low pressure surge of up to 3 atm can cause depressurization of individual elements or their connections. In order to smooth out pressure drops due to unstable pump operation or changes in coolant temperature, in closed system heating system, install an expansion tank. Unlike a similar device in the system open type, it has no communication with the atmosphere. One or more of its walls are made of elastic material, due to which the tank acts as a damper during pressure surges or water hammer.

Availability expansion tank does not always guarantee maintaining pressure within optimal limits. In some cases it may exceed the maximum permissible values:

• if the expansion tank capacity is incorrectly selected;
• in case of malfunction of the circulation pump;
• when the coolant overheats, which is a consequence of malfunctions in the boiler automation;
• due to incomplete opening shut-off valves after repair or maintenance work;
• due to the appearance air lock(this phenomenon can provoke both an increase in pressure and a drop);
• when decreasing bandwidth dirt filter due to excessive clogging.

Therefore, in order to avoid emergency situations when installing heating systems closed type It is mandatory to install a safety valve that will release excess coolant if the permissible pressure is exceeded.

What to do if the pressure in the heating system drops

Pressure in the expansion tank.

When operating autonomous heating systems, the most common emergency situations are those in which the pressure gradually or sharply decreases. They can be caused by two reasons:

• depressurization of system elements or their connections;
• problems with the boiler.

In the first case, the location of the leak should be located and its tightness restored. You can do this in two ways:

1. Visual inspection. This method is used in cases where the heating circuit is laid open method(not to be confused with an open type system), that is, all its pipelines, fittings and instruments are visible. First of all, carefully inspect the floor under the pipes and radiators, trying to detect puddles of water or traces of them. In addition, the location of the leak can be identified by traces of corrosion: characteristic rusty streaks form on radiators or at the joints of system elements when the seal is broken.
2. Using special equipment. If a visual inspection of the radiators does not yield anything, and the pipes are laid in a hidden way and cannot be examined, you should seek the help of specialists. They have special equipment that will help detect leaks and fix them if the home owner is unable to do this themselves. Localizing the depressurization point is quite simple: water is drained from the heating circuit (for such cases, a drain valve is installed at the lowest point of the circuit during the installation stage), then air is pumped into it using a compressor. The location of the leak is determined by the characteristic sound that leaking air makes. Before starting the compressor, the boiler and radiators should be insulated using shut-off valves.

If problem area is one of the connections; it is additionally sealed with tow or FUM tape, and then tightened. The burst pipeline is cut out and a new one is welded in its place. Units that cannot be repaired are simply replaced.

If the tightness of pipelines and other elements is beyond doubt, and the pressure in a closed heating system still drops, you should look for the reasons for this phenomenon in the boiler. You should not carry out diagnostics yourself; this is a job for a specialist with the appropriate education. Most often the following defects are found in the boiler:

Installation of a heating system with a pressure gauge.

• the appearance of microcracks in the heat exchanger due to water hammer;
• factory defect;
• failure of the make-up valve.

A very common reason why the pressure in the system drops is the incorrect selection of the expansion tank capacity.

Although the previous section stated that this may cause increased pressure, there is no contradiction here. When the pressure in the heating system increases, it triggers safety valve. In this case, the coolant is discharged and its volume in the circuit decreases. As a result, the pressure will decrease over time.

Pressure control

For visual monitoring of pressure in the heating network, dial pressure gauges with a Bredan tube are most often used. Unlike digital instruments, such pressure gauges do not require connection electrical supply. IN automated systems use electrical contact sensors. At the outlet to the control and measuring device it is necessary to install three way valve. It allows you to isolate the pressure gauge from the network during maintenance or repair, and is also used to remove an air lock or reset the device to zero.

Instructions and rules governing the operation of heating systems, both autonomous and centralized, recommend installing pressure gauges at the following points:

1. Before the boiler installation (or boiler) and at the exit from it. At this point the pressure in the boiler is determined.
2. Before and after the circulation pump.
3. At the entrance of the heating main into a building or structure.
4. Before and after the pressure regulator.
5. At the filter inlet and outlet rough cleaning(mud collector) to control the level of its contamination.

All control and measuring instruments must undergo regular verification to confirm the accuracy of the measurements they perform.