Permissible differential pressure at the inlet of the heating system. Choosing a heating pressure regulator

In closed heating systems, the coolant is water or antifreeze liquid- inevitably exerts pressure on the walls of pipes and working equipment. Water pressure is used in the design as one of the key parameters of the heating system, and is also taken into account to check its serviceability.

The pressure in the heating pipes allows you to determine how well the entire system is functioning.

The pressure in the pipes is usually divided into several types:

• Static (manometric) - the physical effect on the walls of the pipeline, exerted by the coolant in a calm state. AT summer period when heating systems in houses are not in operation, it is possible to determine static pressure.
• Dynamic (working) - water pressure, taking into account heating and movement along a closed perimeter. Dynamic pressure is always higher than static pressure due to the expansion of the liquid under the influence of temperature.
• Permissible (maximum) - the maximum possible pressure in the system at which all equipment is working properly.

The prescribed norms and rules regulate what the temperature and humidity indicators in the heating circuit should be.

According to the requirements of SNiP, pressure and temperature hot water in closed system should be such that the air in the rooms is stably heated to 20-22°C at a relative humidity of 30-45%.

The more floors in the house, the higher the level of static pressure, in order for the water in the pipes to rise evenly to the upper floors, powerful pumps are used.

What should be the working pressure

Working pressure is the sum of static pressure and dynamic pressure. The safety of the entire heating line depends on its value.

It is important! normal pressure coolant - necessary condition for correct and effective work systems. It is necessary to maintain it at the set level so that the temperature in the heated rooms is within the range of permissible values.

With considering various factors, the working pressure in the systems should be:

• 2-4 atmospheres - for buildings up to 5 floors;
• 5-7 atmospheres - for houses of 9-10 floors;
• from 12 atmospheres - for buildings from 10 floors and above.

The pressure that should be in the heating system of an apartment building is regulated by SNiPs and established norms. The calculation takes into account the diameter of the pipes, the types of pipeline and heating appliances, distance to the boiler room, number of storeys.

Types of pressure

Speaking about the pressure in the heating system, they mean 3 types of it:

1. Static (manometric). When performing calculations, it is taken equal to 1 atm or 0.1 MPa per 10 m.
2. Dynamic, which occurs when the circulation pump is turned on.
3. Permissible working, which is the sum of the previous two.

In the first case, this is the pressure force of the coolant in radiators, valves, pipes. The higher the number of storeys of the house, the greater value acquires this value. Powerful pumps are used to overcome the rise of the water column.

The second case is the pressure that occurs during the movement of fluid in the system. And from their sum - the maximum working pressure, the operation of the system in a safe mode depends. In a multi-storey building, its value reaches 1 MPa.

GOST and SNiP requirements

In modern high-rise buildings installation of the heating system is carried out based on the requirements of GOST and SNiP. The regulatory documentation specifies the temperature range that central heating must provide. This is from 20 to 22 degrees C with humidity parameters from 45 to 30%.

To achieve these indicators, it is necessary to calculate all the nuances in the operation of the system even during the development of the project. The task of a heat engineer is to ensure the minimum difference in the pressure values ​​​​of the liquid circulating in the pipes between the lower and last floors home, thereby reducing heat loss.

The following factors influence the actual pressure value:

• The condition and capacity of the equipment supplying the coolant.
• The diameter of the pipes through which the coolant circulates in the apartment. It happens that, wanting to increase temperature indicators, the owners themselves change their diameter upwards, reducing general meaning pressure.
• The location of a particular apartment. Ideally, this should not matter, but in reality there is a dependence on the floor, and on the distance from the riser.
• The degree of wear of the pipeline and heating devices. In the presence of old batteries and pipes, one should not expect that the pressure readings will remain normal. It is better to prevent the occurrence of emergency situations by replacing your old heating equipment.

Check the working pressure in a high-rise building using tubular deformation pressure gauges. If, when designing a system, the designers laid down automatic adjustment pressure and its control, then additionally install sensors different types. In accordance with the requirements prescribed in the regulatory documents, control is carried out in the most critical areas:

• at the coolant supply from the source and at the outlet;
• before the pump, filters, pressure regulators, mud collectors and after these elements;
• at the outlet of the pipeline from the boiler room or CHP, as well as at its entry into the house.

Please note: 10% of the difference between the normative working pressure on the 1st and 9th floors is normal.

pressure in summer

During the period when the heating is inactive, both in the heating network and in the heating systems, a pressure is maintained that exceeds the static pressure. Otherwise, air will enter the system and the pipes will begin to corrode.

The minimum value of this parameter is determined by the height of the building plus a margin of 3 to 5 m.

How to raise the pressure

Pressure checks in heating lines multi-storey buildings are definitely needed. They allow you to analyze the functionality of the system. A drop in pressure level, even by a small amount, can cause serious failures.

In the presence of central heating, the system is most often tested cold water. The pressure drop for 0.5 hours by more than 0.06 MPa indicates the presence of a gust. If this is not observed, then the system is ready for operation.

Immediately before the start of the heating season, a test is performed with hot water supplied under maximum pressure.

Changes occurring in the heating system of a multi-storey building, most often do not depend on the owner of the apartment. Trying to influence the pressure is a pointless undertaking. The only thing that can be done is to eliminate air pockets that have appeared due to loose connections or improper adjustment of the air release valve.

A characteristic noise in the system indicates the presence of a problem. For heating appliances and pipes, this phenomenon is very dangerous:

• Loosening of threads and destruction of welded joints during vibration of the pipeline.
• Termination of the supply of coolant to individual risers or batteries due to difficulties in de-airing the system, the inability to adjust, which can lead to its defrosting.
• A decrease in the efficiency of the system if the coolant does not stop moving completely.

To prevent air from entering the system, it is necessary to test it in preparation for heating season inspect all connections, taps for water leakage. If you hear a characteristic hiss during a test run of the system, immediately look for a leak and fix it.

Can be applied to joints soap solution and where the tightness is broken, bubbles will appear.

Sometimes the pressure drops even after replacing old batteries with new aluminum ones. A thin film appears on the surface of this metal from contact with water. Hydrogen is a by-product of the reaction, and by compressing it, the pressure is reduced.

Interfering with the operation of the system in this case is not worth it. The problem is temporary and goes away on its own over time. This happens only in the first time after the installation of radiators.

You can increase the pressure on the upper floors of a high-rise building by installing a circulation pump.

Minimum pressure

From the condition when the superheated water in the heating system does not boil, the minimum pressure is taken.

You can define it like this:

A margin of approximately 5 m is added to the height of the house (geodesic) to avoid air pollution, plus another 3 m for the resistance of the heating system inside the house. If the supply pressure is insufficient, then the batteries on the upper floors will remain unheated.

If we take a 5-storey building, then the minimum supply pressure should be:

5x3+5+3=23 m = 2.3 ata = 0.23 MPa

Pressure drop

In order for the heating system to perform its functions normally, the pressure drop, which is the difference between its values ​​​​on the supply and return, must be a certain and constant value. In numerical terms, it should be in the range from 0.1 to 0.2 MPa.

The deviation of the parameter to a smaller side indicates a failure in the circulation of the coolant through the pipes. Fluctuation towards an increase in the indicator - about airing heating system.

In any case, you need to look for the cause of the change, otherwise individual elements may be out of order.

If the pressure has dropped, then check for leaks: turn off the pump and observe changes in static pressure. If it continues to decrease, then they look for the place of damage by sequentially removing different sections from the circuit.

In case when static head does not change, then the reason lies in the malfunction of the equipment.

The stability of the differential operating pressure initially depends on the designers, on their hydraulic calculations, and then correct installation highways. The heating of a high-rise building is functioning normally, during the installation of which the following points are taken into account:

• The supply pipeline, with rare exceptions, is at the top, the return at the bottom.
• Spills are made of pipes with a cross section of 50 to 80 mm, and risers and supply to batteries - from 20 to 25 mm.
• Regulators are embedded in the heating system in the bypass line of the pump or the jumper connecting the supply and return, ensuring that even with sudden pressure drops, air does not appear.
• Shutoff valves are present in the heat supply scheme.

There are no ideal operating conditions for a heating system. There are always losses that reduce pressure indicators, but still they should not go beyond the regulated building codes and the rules of the Russian Federation SNiP 41-01-2003.

What should be the pressure in a high-rise building?

From this article you will learn what pressure in the heating system of a multi-storey building is considered normal, about the causes of its drops and how to troubleshoot. We will also talk about methods for checking the circuit for strength and choosing the optimal radiators for the system.

Pressure in the central heating system

High pressure in central system heating of an apartment building is necessary in order to raise the coolant to upper floors. In skyscrapers, circulation occurs from top to bottom. The supply is carried out by boiler rooms with the help of superchargers. This is electric pumps dispersing hot water. The pressure gauge reading on the return flow depends on the height of the building. Knowing what pressure is expected in the heating system of a multi-storey building, appropriate equipment is selected. For a nine-story building, this figure will be approximately three atmospheres. The calculation is based on the fact that one atmosphere raises the flow by ten meters. The ceiling height is approximately 2.75 m. We also take into account a five-meter gap to the basement and technical floor. Based on this calculation, you can find out what pressure should be in the heating system of a multi-storey building of any height.

Temperature and pressure distribution in elevator node apartment building

The central city and housing and communal networks are separated by elevators. An elevator is a node through which a coolant is supplied to the heating system of a high-rise building. It mixes the supply and return flow, depending on what pressure is required to heat the apartment building. The design of the elevator has a mixing chamber with an adjustable opening. It's called a nozzle. Adjusting the nozzle allows you to change the temperature and pressure in the heating system of a multi-storey building. Hot water in the mixing chamber mixes with water from the return flow and involves it in a new cycle. By changing the size of the nozzle opening, you can reduce or increase the amount of hot water. This will lead to a change in temperature in the radiators of apartments and a change in pressure. The temperature in the heating system of the house at the entrance is 90 degrees.

Causes of pressure drops in the heating of an apartment building

Heating return pressure apartment buildings lower than submissions. The normal deviation is two bars. In normal operation, boiler rooms supply coolant to the system with a pressure of more than seven bar. About six bar reaches the heating system of a skyscraper. The flow is affected by hydraulic resistance, as well as branches in housing and communal networks. On the return line, the pressure gauge will show four bars. The pressure drop in the heating of an apartment building can be caused by:

• air lock;


• leakage;


• failure of system components.

In practice, gaps often occur. The water pressure in the heating system of an apartment building largely depends on the inner diameter of the pipes and the temperature of the coolant. Technical marking of the conditional passage - DU. For spills, pipes with a nominal bore of 60 - 88.5 mm are used, for risers - 26.8-33.5 mm.

Important! The pipes connecting the heating radiators and the riser must be of the same section. Also, the supply and return must be connected to each other before the battery.

The most important thing is that the apartment was warm. The hotter the water in the radiators, the higher the pressure in the system central heating apartment building. The return temperature is also higher. For stable operation of the heating system, the water from the reverse cycle pipe must be at a fixed temperature.

Elimination of drops

Elevator nozzle device

With a decrease in the return flow temperature and a change in pressure in the heating pipes in an apartment building, the diameter of the elevator nozzle is adjusted. It expands if necessary. This procedure must be agreed with the service provider (CHP or boiler house). Do-it-yourself activities are not allowed. In extreme situations, when defrosting of the system is at risk, the adjustment mechanism can be completely removed from the elevator. In this case, the coolant enters the communications of the house without hindrance. Such manipulations lead to a decrease in pressure in the central heating system and a significant increase in temperature, up to 20 degrees. Such an increase can be dangerous for the heating system of the house and city networks in general.

An increase in the temperature of the working medium from the return flow is associated with an increase in the diameter of the nozzle, which leads to a decrease in pressure in the heating of apartment buildings. In order to lower the temperature, it should be reduced. There is no need for welding work. Then a new hole is drilled with a smaller diameter drill. This will reduce the amount of hot water in the elevator mixing chamber. This manipulation is carried out after stopping the circulation of the coolant. If there is an urgent need, without stopping the system, reduce the return temperature, the valves are partially closed. But this can be fraught with consequences. Metal dampers stop valves create a barrier to the coolant. As a result, pressure and friction force increase. This increases the wear of the dampers. If it reaches a critical level, the damper can break away from the regulator and completely shut off the flow.

Features of autonomous heating

The normal rate for closed circuit 1.5 -2.0 bar, which is much different from the pressure in the central heating pipes. The reason for the downgrade could be:

• depressurization - when a leak or microcracks appear, through which water can escape. Visually, this may not be noticeable, since a small amount of water has time to evaporate;


• decrease in coolant temperature. The lower the temperature of the water, the less its expansion;


• the presence of autonomous pressure regulators that bleed air. They are installed to remove air pockets. Often leak;


• change in the radius of the conditional passage of pipes. plastic pipes when heated, they can change their geometry - they become wider.

Not only the circulation of the coolant, but also the serviceability of the equipment depends on the pressure indicator in the heating system. To prevent a decrease and increase in pressure in any part of the system, a expansion tank. It is a metal container with a rubber membrane inside. The membrane divides the tank into two chambers: with water and air. At the top there is a valve through which air escapes during an extreme increase in pressure. It can occur due to excessive heating of the liquid. After the water cools down and decreases in volume, the pressure in the system will not be enough, because the air has escaped. The calculation of the volume of the expansion tank is carried out based on the total volume of the coolant in the system.

Radiator selection

It is important to choose the optimal radiator for the heating system

• in private up to 3 bar;


• the operating pressure in the heating system of an apartment building is 10 bar.

In addition, it is necessary to take into account periodic checks of the reliability of the heating system, the so-called water hammer.

In a normally functioning heating system, a pressure difference is maintained between the direct pipeline, through which the coolant is supplied from the boiler room or heating main, and the return pipeline, through which it is supplied to the next circle, passing through the radiators. For various objects, it is 0.2–0.25 MPa or 2–2.5 atmospheres. It is due to this difference that there is a constant circulation of fluid in the circuit, and at the rate that is necessary to maintain comfortable temperature air in all rooms.

Optimal operating pressure parameters in the heating circuit or the head providing this difference are determined at the design stage. At the same time, for different objects, its value is different and depends on the height of the building, the type of system and the heating equipment used, and a difference of more than 0.02 MPa or 0.2 atmospheres is considered abnormal.

Normal working pressure for various objects

One-story house - 0.1–0.15 MPa or 1–1.5 atmospheres
low-rise building(no more than three floors) - 0.2–0.4 MPa or 2–4 atmospheres;
medium-rise apartment building (5–9 floors) - 0.5–0.7 MPa or 5–7 atmospheres
high-rise apartment buildings– up to 10 MPa or 10 atmospheres.

The pressure value is controlled using pressure gauges installed in the most critical areas:

At the input and output of the line with the coolant (with central heating);
before and after the heating boiler (with individual heating);
before and after the circulation pump (with forced circulation);
near filters, valves and pressure regulators.

The consequences of pressure going beyond the norm

Even a small deviation of pressure from the calculated indicator threatens at least temporary inconvenience. The temperature in some rooms may decrease, while others, on the contrary, increase. In the event that the hot water and heating systems are combined into one at the facility, a lack of pressure can also cause a lack of water on the upper floors.

With a significant change in the differential for various reasons, modern equipment can automatically turn off, and outdated equipment can fail. Old models of boilers that are not equipped with thermal control systems can even explode when pressure drops, which is fraught with significant damage.

What needs to be done to maintain the required pressure drop in the heating system:

1. Observe the established standards when designing and installing a heating system, primarily regarding the location of the direct and return risers relative to each other and the diameters of the pipelines.
2. Take into account the change in coolant pressure with a change in its temperature.
3. If it is not possible to achieve the required differential pressure using static pressure, use circulation pumps.
4. For automatic regulation working pressure in private houses use hydraulic accumulators, which allow you to compensate for a slight overshoot by taking part of the coolant.
5. In apartment buildings a similar function is performed by pressure regulators installed on the pump bypass or between the direct and return risers.
6. In some cases, in large facilities, to adjust the working pressure, a pipeline accessories, providing the possibility of changing the diameter of the pipeline due to its partial overlap.

The main reasons for the drop in operating pressure and how to eliminate them

The most common causes of pressure drop in the heating system are:

Coolant leakage;
reducing the volume of the coolant when removing the air contained in it;
decrease in coolant temperature due to malfunctions of boiler equipment;
malfunctions of pumping equipment (in a system with forced circulation).

Leaks are indicated by the drop in static pressure when the pump is turned off, and external signs leaks in pipes and radiators. If the static pressure does not change, then the reason is pumping equipment. If the coolant volume decreases due to the removal of plugs, it is necessary to restore it, and if the temperature drops, check the boiler.

The main reasons for the increase in operating pressure in the heating system:

airing the system;
severe clogging of filters;
erroneous setting or damage to the pressure regulator;
an increase in the volume of the coolant due to improper operation of the control automation.

First of all, you should check the condition of the filters and air plugs in the system, and if necessary, clean the former and remove the latter. The operation of automation can be checked by turning off the possibility of feeding the system. You can check the operation of the regulator by trying to adjust its settings.

Consider what the pressure of the heating system is, what it should be (its calculation), what it consists of, how it is regulated, and what its drops signal.
[content h2 h3]

To begin with, let's define - speaking about the pressure in the heating system, we take into account overpressure, not absolute. All characteristics of boilers and heating networks are described by this parameter, pressure gauges also show it. Excess pressure differs from absolute pressure by the value of atmospheric pressure. It is usually taken into account that it is 0.1 MPa or 1 Bar (atmosphere) less, although exact value may fluctuate, since the atmospheric pressure is not constant and depends on the height above sea level and meteorological processes.

The operating pressure in the heating system consists of two values:

1. Static - due to the height of the water column in the heating system. It can be taken into account that 10 meters create a pressure of 1 atmosphere;
2. Dynamic - which is created by pumps for the circulation of the coolant, as well as the convective flow of water from heating. However, it should be noted that it is not determined only by the characteristics network pumps, because on it big influence provides a heating regulator that redistributes the flow of coolant. Also, the regulator often includes booster pumps or elevators in its circuit.

The most frequently asked question is what pressure of the coolant should be in the heating system of the house, and how is it calculated? There are also two options here:

1. If we are talking about, then it is a small amount higher than the static pressure in the system;
2. If we are talking about a system with forced movement of the coolant, then it is necessarily higher than the static one, and is chosen as large as possible to ensure high efficiency systems.

The maximum is taken into account allowed values for elements of the heating system, for example cast iron radiators, as a rule, cannot work at a pressure of more than 0.6 MPa.

If we take high-rise buildings as an example, then we have to use a pressure regulator on the lower levels and pumps to increase the water pressure on the upper floors.

How to control the pressure in the system?

To control at various points in the heating system, pressure gauges are inserted, and (as mentioned above) they record excess pressure. As a rule, these are deformation devices with a Bredan tube. In the event that it is necessary to take into account that the pressure gauge must work not only for visual control, but also in the automation system, electrocontact or other types of sensors are used.

Lead-in points defined normative documents, but even if you have installed a small boiler for heating a private house, which is not controlled by GosTekhnadzor, it is still advisable to use these rules, since they highlight the most important points of the heating system for controlling pressure.

It is necessary to embed manometers through three-way valves, which provide their purge, reset to zero and replacement without stopping all heating.

The control points are:

1. Before and after the heating boiler;
2. Before and after the circulation pumps;
3. Output of heat networks from a heat generating plant (boiler house);
4. Entering heating into the building;
5. If a heating regulator is used, then the pressure gauges cut in before and after it;
6. In the presence of mud collectors or filters, it is advisable to insert pressure gauges before and after them. Thus, it is easy to control their clogging, taking into account the fact that a serviceable element almost does not create a drop.

A symptom of malfunctions or improper operation of the heating system is pressure surges. What do they stand for?

If the pressure drops

In this case, it is advisable to immediately check how the static pressure behaves (stop the pump) - if there is no drop, then the circulation pumps are faulty, which do not create water pressure. If it also decreases, then most likely there is a leak somewhere in the pipelines of the house, the heating main or the boiler house itself.

The easiest way to localize this place is by turning off various sections, monitoring the pressure in the system. If the situation returns to normal at the next cutoff, then there is a water leak on this section of the network. At the same time, take into account that even a small leak through a flange connection can significantly reduce the pressure of the coolant.

But there is a small nuance - the home heating regulator can independently cut off sections during automatic control so it needs to be disabled.

If the pressure rises

This situation is less common, but still possible. Its most likely cause is that there is no movement of water along the circuit. To diagnose, do the following:

1. And again we remember about the regulator - in 75% of cases the problem is in it. To reduce the temperature in the network, it can cut off the coolant supply from the boiler room. If it works for one or two houses, then it is possible that the devices of all consumers worked at the same time and stopped the flow.
   

   It is necessary to investigate the settings and adjust them so that the regulator does not give an order to completely close the valves, its inertia will increase, but such situations will be excluded;

2. Perhaps the system is under constant replenishment (malfunction of automation or someone's negligence). As the simplest calculation shows, the more coolant in a limited volume, the higher the pressure. In this case, it is enough to shut off the power line or set up automation;
3. If, however, everything is in order with the control devices or the heating system does not turn them on at all, we again take into account, first of all, the human factor - perhaps, somewhere along the course of the coolant, a tap or valve is closed;
4. The least likely situation is when an air lock interferes with the movement of the coolant - it is necessary to detect and remove it. The filter or sump may also be clogged in the direction of the coolant;

What does a large or small pressure difference between supply and return mean?

The normal difference between the pressure of the supply and return pipelines is 1-2 atmospheres. What does a change in this value in one direction or another mean?

1. If the difference between the supply and return pressure is significant, then the system is almost at a standstill, possibly due to an air lock. It is necessary to find the cause and restore the circulation of the coolant;
2. If in the heating system of your house it is much less, and tends to zero, then the movement of water through the pipes is disturbed. Most likely, water flows through nearby areas and does not reach remote areas, the adjustment is broken. But you need to take into account the fact that if the difference changes over time, and all the radiators warm up normally, the heating regulator may be to blame - the principle of its operation includes bypassing part of the water from the supply to the return, and perhaps the jump is due to the fact that just this cycle.

Why you need a differential pressure regulator

For the normal functioning of the heating system and the stable circulation of water through all its elements, a stable pressure drop is required. Sharp jumps in the pressure of the coolant lead to a violation hydraulic mode and malfunction of individual nodes.

In the heating system small house, as a rule, membrane water accumulators are mounted, which allow you to get rid of these undesirable phenomena. In more complex and large systems use a regulator that provides a stable pressure drop in the heating system and avoids airing even with sharp jumps in main pipelines. Also, the regulator is often mounted on bypass (bypass) lines of pumps, which makes it possible to make the characteristics of the unit constant.