home Design and calculations

Return pressure in the heating system

Most private house owners independently maintain an autonomous heating system. Because of this, the most common question they have is: "What is the working pressure in the heating system (CO), and what are the reasons for its deviation from the norm?". The answers to these questions will be the topic of this publication.

We study the theory

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

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

It should be understood that this indicator is not the same in some sections of the heating circuit. For example, on the supply line (after the circulation pump), the head is always higher than in the reverse current section.

Summarizing the above: the pressure of the heating medium in the heating system depends entirely on the temperature of the coolant, the pipeline cross-section, the fixtures and equipment, and also the pump capacity.

Defined with terminology

In modern heating engineering and regulatory documents there are several definitions:

Static, appears in the system under the influence of gravity on the coolant.
Dynamic, caused by the movement of water in the CO.
The operating pressure in the heat supply system is the sum of the static pressure and the dynamic head.
Nominal, characterizes the indicator at which the manufacturer guarantees CO elements a certain period of operation without changes in performance characteristics.
The maximum. This is a boundary indicator that can withstand CO without damaging its elements.
Testing or test, usually taken above the worker in 1,5-2 times.

Important! The "weakest link" in any heating system is the heat exchanger of the heat generator. The most durable models can withstand about 3 kg / cm 2 or 0.3 MPa. In addition, the distribution of CO, made by a polymer pipe, also has limitations.

Statics and dynamics

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

Quite often, the installation of a private house heating system requires the presence of a circulation pump and expansion tank closed type. In such a design, there is both a static (due to a difference in heights) and a dynamic effect that will be created by the pumping equipment. As the distance from the circulation pump, this figure is slightly reduced due to the hydraulic resistance created by the pipeline, fittings and other elements of the system.

"Horseracing" and "swings"

In the process of operating autonomous systems, virtually every owner faces the problem of pressure spikes. An increase in this value can speak of:

Overheating of the coolant.
Incorrect piping calculations.
Contamination of CO.
Presence of air congestion.
Incorrect operation of the pressure regulator in the heating system.

Tip: If you are faced with this problem, the first thing to do is check the makeup. In practice, it is this reason that experts say is the most common.

The drop in pressure on the owner of an autonomous private house can tell the following:

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

Tip: The leakage of the coolant from the CO can also be "imperceptible", through the damaged membrane of the expansion tank. For checking, you need to press the expansion tank expansion valve. The presence of water indicates a fissure in the membrane.

Removing the airlock through the air vent. As a rule, this problem occurs soon after the filling of the CR.

Covering the section of the CO with a shut-off device.

Control methods

To monitor the pressure in the CO, use specialized instruments - pressure gauges, which in real time show all the changes in this value. Structurally, these devices can carry a purely informative function, or be equipped with a contact group that commutes the operation of some CO elements. For example, when the pressure rises above the nominal pressure, the pressure gauge contacts open, which causes the heat generator to stop working.

Important! To monitor the state of CO quickly, manometers are installed: on the piping of the boiler; on the entrance and exit of pumping equipment; on the sides of the water pressure regulator in the heating system. In addition, experts recommend installing pressure gauges on the ramifications of sites; on the sides of the mudmen; at the bottom and top of the CO.

As is known, when heated, the coolant expands, as a result of which its volume increases. The expansion tank, which can be closed or open type, responds to the compensation of the volume of the expanding coolant and a sharp pressure jump.

To maintain the operating and nominal pressure values, the SO includes a so-called safety group, which consists of a manometer, an automatic air vent and a blasting valve.

What is the norm?

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

Most of our compatriots living in apartment buildings with a central SB are interested in the question, what is the pressure in the heating pipes in the apartment? It is almost impossible to answer this question unequivocally: everything depends on the number of floors in the house and the layout chosen.

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The operation of any heating system requires certain temperature and pressure gradient values, which are calculated during design. But sometimes during operation there is a pressure drop in the heating system - there is a deviation in the smaller or larger side. This problem must be addressed not only to maintain the efficiency of heating, but also for safety.

Working pressure in heating systems

The operating pressure is important, which ensures the normal functioning of the heating system, including the heat source, expansion tank, pump (more in detail: ""). It is calculated in atmospheres (1 atmosphere is 0.1 MPa). The indicator should be equal to the sum of two pressures:

static, created by a column of water (in the course of carrying out it is guided by the fact that there are 1 atmosphere per 10 meters);
dynamic, caused by the operation of the circulation pump and convective movement of the coolant during heating.

In different heating systems, the pressure head differs. For example, if the heat supply of the house is due to the natural circulation of the coolant (this option is possible with low-rise construction), then the pressure will only be slightly higher than the static pressure. And in systems with forced circulation It is much more that is necessary to obtain a higher efficiency.

It should be taken into account that the maximum operating pressure of the heating system is determined by the characteristics of its elements. For example, when using radiators made of cast iron, it should not exceed 0.6 MPa.

The working head index is:

for low-rise buildings with closed circuit - 0.2-0.4 MPa;
for one-story buildings with natural circulation coolant and open circuit - 0.1 MPa for every 10 meters of the water column;
for multi-storey buildings - up to 1 MPa.

Controlling pressure drops

In order for the heating system to work in normal mode, and the risk of an accident has been minimized, it is necessary to control the temperature and the head of the coolant from time to time. For this purpose, a special pressure sensor in the heating system is used, as in the photo.

Most often, pressure gauges with a Bourdon tube are used to measure the pressure. When determining the small pressure, their version can also be used - diaphragm instruments. After a water hammer, such models should be verified, since in subsequent measurements they can show inflated values.

In those systems in which automatic control and pressure adjustment are provided, are additionally applied different types sensors (for example, electrocontact).

Placement of pressure gauges (insert points) is determined by the regulations.

These devices should be installed in the most important areas of the system:

at its entrance and exit;
before and after filters, pump, pressure regulators, mud collectors;
at the exit of the main from the boiler or CHP and at the entrance to the building.

These recommendations must be observed even when creating a small heating circuit and using a low-power boiler, because not only does the safety of the system depend on it, but also its economy, which is achieved due to the optimal fuel and water consumption (read: ""). Pressure gauges are recommended to be connected via three-way valves - this will allow to purge, zero and replace devices without stopping the heating system.

Differential pressure value for the heating system

For a normal functioning of the heat supply, a certain pressure difference (the difference in the values of the flow and return of the coolant) is needed. Typically, the pressure loss in the heating system is 0.1-0.2 MPa.

When this indicator is less, this is a signal about the violation of water flow through pipelines, which is accompanied by inefficient heating (the coolant passes through the radiators without heating them to the required value). If the drop is exceeded by more than 0.2 MPa, the "stagnation" of the system arising as a result of zvozdushivaniya begins.

A sudden change in pressure does not have the best effect on the functioning of individual elements of the heating design, often causing them breakdowns.

Also important is the installation of pipelines and highways:

it is recommended to place the supply pipe from above, and the return pipe from below;
for spills should be involved pipes with a diameter of 50-80 millimeters, for risers - 20-25 millimeters;
the connection to the radiators can be made from the same pipes that are used for risers, or slightly less.

The cross-section of the radiator piping can be understated only if there is a jumper in front of them.

In addition, it is known that the heat carrier increases with a rise in temperature in the volume, respectively, the pressure in the heating system rises. For example, at 20 degrees it rises by 0.13 MPa, and at 70 degrees - by 0.19 MPa. Therefore, to adjust the head, you can simply change the water heating level.

To increase the pressure of the coolant, and this is important for providing heat to multi-storey houses, it is necessary to use circulating pumps.

To automatically adjust the working pressure and drop in small buildings, expansion tanks (usually of the membrane type) are used. They begin to function in the event that the pressure in the system rises to 0.2 MPa. These devices remove the excess hot water, which as a result helps maintain the pressure at the required level.

The expansion tank can be installed in any part of the circuit. Its volume is approximately equal to 10% of the total system capacity. However, experts advise installing it on a straight pipe return pipe in front of circulation pump, if it is present.

In the schemes it is envisaged to use a safety valve that removes excess coolant from the system - this is necessary to prevent a situation in which the tank capacity is not enough to stop the pressure build-up.

In complex and large heating structures, which are often found in multi-storey buildings, regulators are used to maintain the required pressure. They prevent the air-blasting even with sudden head-ons and noise on the control valves. They are installed on the bridge between the supply and return pipes, or on the bypass line of the pump.

There is also a way to control the pressure in multi-storey houses - this is the use of stop valves. For example, if the pressure drop in the heating system is observed, then to increase the value with the help of the gate valve, the cross-section of the return pipeline decreases. If the pressure deviates to a lower or higher side of the norm, it is necessary to find out the cause of the problem and eliminate it.

Pressure drop

If the pressure drops in the system, it is most likely that a leakage of the coolant occurs. The most vulnerable places are joints, seams and joints. To check, the pump is switched off and the static pressure changes are observed. If the head continues to decrease, you need to find the damaged area. For this purpose, experts recommend turning off different parts of the circuit, and after determining the location of the damage, replace or repair these elements.

In the event that the pressure remains stable, the pressure drop may be due to malfunction of the heating equipment or pump. A short-term pressure drop is sometimes due to the operating features of the regulator, which periodically releases a part of the water from the supply to the return. If the radiators are heated to the required temperature, and evenly, then the pressure drop occurred precisely because of the regulator.

Also, the causes of pressure reduction can be:

decrease in water temperature;
removal of air by air, which causes the volume in the coolant system to decrease.

Increase in pressure

If the maximum pressure in the heating system is exceeded, the reason for this is the slowing or stopping of the water flow in the heating circuit.

This can lead to:

contamination of mud collectors and filters;
the appearance of an airlock;
water supply of the coolant due to a malfunction of the automation or incorrectly adjusted valves located on the feed and return (read: "");
feature of the controller or its incorrect setting.

Unstable pressure is especially common in recently launched heating systems, which is associated with the removal of air. This is considered normal if, after adjusting the volume of water and pressure to operating values for several weeks, there are no deviations.

Otherwise, most likely, the instability of the pressure is due to incorrect hydraulic calculations, including - and insufficient volume of the expansion tank. That is why when installing a heating system, it is important to perform all the calculations correctly - in the future this will save you from various problems with its functioning.

When installing a heating system, several pressure gages are inserted into the pipeline. With the help of data measuring instruments control the working pressure in the heating system. In the case of fixing deviations from the normalized values, measures are taken to eliminate the causes that caused changes in the operation of the system. Critical is the drop in the pressure level by 0.02 MPa. Leaving aside the pressure drops in the heating system is by no means possible, as this negatively affects the efficiency of heating the room, the operation of the installed equipment and the period of its operation. In the period of preparation for the new heating season, during which excessive pressure is created in the system to identify "weak" areas and their early repair. The system thus tested allows you to be sure that all its elements are able to withstand the hydraulic shocks that occur in the heat network.

What is the norm of pressure?

The pressure in the autonomous heating system of a private house should be 1.5-2 atmospheres. In houses connected to a centralized heating network, this value depends on the number of storeys. In low-rise buildings, the pressure in the heating system is in the range of 2-4 atmospheres. In houses-nine-storey buildings this indicator is equal to 5-7 atmospheres. For heating systems of high-rise buildings, the optimal pressure value is 7-10 atmospheres. In the heating main, which goes underground from the CHPP to the points of heat consumption, the coolant is supplied under a pressure of 12 atm.

To reduce the pressure of hot water on the lower floors apartment buildings use pressure regulators. Increase the pressure on the upper floors allows pumping equipment.

The manual balancing valve (regulator), equipped with needle-type measuring nipples, allows controlling the differential pressure in the heating system

Influence of coolant temperature

After the installation of the heating equipment in the private house is completed, the coolant is pumped into the system. At the same time, a minimum possible pressure of 1.5 atmospheres is created in the network. This value will increase during the heating of the coolant, since in accordance with the laws of physics, its expansion takes place. By changing the temperature of the coolant, it is possible to adjust the pressure in the heat network.

Automate the monitoring of working pressure in the heating system by installing expansion tanks that do not allow excessive head pressure. These devices are activated when the pressure level reaches 2 atm. The surplus of the heated coolant is withdrawn by the expansion tanks, so that the pressure is kept at the desired level. It may happen that the capacity of the expansion tank is not enough to select excess water. At the same time, the pressure in the system approaches the critical bar, which is at a level of 3 atm. The situation saves safety valve, which allows to keep intact heating system by releasing it from the excess volume of the coolant.

With the coolant, a static pressure is created in the heating system, which is measured by 1 atmosphere for every 10 meters of the height of the water column. During installation, a dynamic pressure value is added to the static indicator, indicating the force with which the forced heat carrier presses against the walls of the pipeline. The maximum pressure setting in an autonomous heating system is made taking into account the features of the heating equipment used in the installation. For example, if you select cast-iron batteries it must be taken into account that they are designed for operation at a pressure not exceeding 0.6 MPa.

The points of the inset of the pressure gauges in the heating system: before and after the boiler, the circulation pump, the regulator, the filters, the mud collectors, as well as the output of the heat networks from the boiler room and at their entrance to the houses

Causes of growth and pressure drop in the system

One of the most common causes of pressure drop in the heating system is the occurrence of leakage of the coolant. "Weak" links most often become the junction of individual parts. Although the pipes can break through, if they are already heavily worn out or defective. The presence of a leak in the pipeline is indicated by the drop in the level of static pressure measured with the circulating pumps switched off.

If the static pressure is normal, then the fault must be found in the pumps themselves. To facilitate the search for leakage, it is necessary to disconnect alternately different sections, keeping in mind the level of pressure. Having determined the damaged area, it is cut off from the system, repaired, sealing all connections and replacing parts with visible defects.

Removing visible coolant leaks after their detection during the inspection of the heating system contour of a private house or apartment

If the pressure of the coolant drops, and the place of leakage can not be found, then specialists are called. Using professional equipment, experienced masters pump air into a system previously freed from water, as well as cut off from the boiler and. By the whistling air escaping through microcracks and loose connections, it is easy to detect places of leakage. If the pressure loss in the heating system is not confirmed, then proceed to check the serviceability of the boiler equipment.

Use of professional equipment when searching for hidden leaks. The scanner of detection of excessive moisture allows you to accurately determine the crack in the pipe

For reasons leading to a reduction in pressure in the system due to a malfunction of the boiler equipment, it is possible to refer:

accumulation of scale in the heat exchanger (typical for areas with hard tap water);
the appearance of microcracks in the heat exchanger, caused by physical wear and tear of equipment, preventive washing, factory marriage;
the destruction of the bithermal heat exchanger that occurred during the time;
damage to the expansion vessel chamber of the boiler.

In each case, the problem is solved in different ways. Water hardness is reduced with the help of special additives. Damaged heat exchanger is sealed or changed. The tank built in the boiler is suppressed, replacing it external device, having suitable parameters.

Due to what is a differential pressure created in heating and water supply systems? What is it for? How to adjust the difference? What are the reasons for the pressure drop in the heating system? In this article we will try to answer these questions.

Functions

First, we will find out why the difference is created. Its main function is to ensure the circulation of the coolant. Water will always move from a high pressure point to a point where the pressure is less. The more the difference - the more speed.

Useful: the limiting factor is the increasing hydraulic resistance with increasing flow velocity.

In addition, the difference is artificially created between the circulation cut-outs of hot water supply into one thread (feed or return).

Circulation in this case performs two functions:

Provides a stable high temperature towel warmers, which in all modern houses open one of the two connected hot water pipes.
Ensures fast flow of hot water to the mixer regardless of the time of day and water extraction in the riser. In old houses without circulation tap water in the mornings has to be drained for a long time before it is heated.

Finally, the difference is created by modern meters of water and heat consumption.

How and for what? To answer this question, we need to refer the reader to the Bernoulli law, according to which the static pressure of the flow is inversely proportional to the speed of its movement.

This enables us to design an instrument that records the flow of water without the use of unreliable impellers:

We pass the flow through the cross section.
We register the pressures in the narrow part of the counter and in the main pipe.

Knowing the pressure and diameters, with the help of electronics you can calculate in real time the flow rate and water flow; When using the same temperature sensors at the input and output from the heating circuit, it is not difficult to calculate the amount of heat remaining in the heating system. At the same time, the consumption of hot water is calculated from the flow difference between the supply and return pipelines.

Creating a Delta

How is pressure differential created?

Elevator

The main element of the heating system apartment building - elevator assembly. His heart is the elevator itself - an ordinary-looking cast-iron tube with three flanges and a nozzle inside. Before explaining the principle of elevator operation, it is worth mentioning one of the problems of central heating.

There is such a thing as a temperature graph - a table of the temperature dependence of the flow paths and the return from weather conditions. Here is a short excerpt from it.

Outside air temperature, С	Feed, C	Return, C
+5	65	42,55
0	66,39	40,99
-5	65,6	51,6
-10	76,62	48,57
-15	96,55	52,11
-20	106,31	55,52

Deviations from the schedule in the greater or lesser side are equally undesirable. In the first case, the apartments will be cold, in the second - the energy carrier's expenses for the thermal power station or the boiler-house will increase sharply.

At the same time, as it is easy to see, the spread between the feed and the return pipeline is quite large. When the circulation is sufficiently slow for such delta temperatures, the temperature of the heating devices will be distributed unevenly. Residents of apartments, whose batteries are connected to the risers, will suffer from heat, and the owners of radiators on the return - freeze.

The elevator provides a partial recirculation of the coolant from the return pipeline. By injecting a rapid jet of hot water through the nozzle, it in full accordance with the Bernoulli law creates a fast flow with low static pressure, which tightens an additional mass of water through the suction.

The temperature of the mixture is noticeably lower than that of the feed, and somewhat higher than return pipeline. The circulation speed is high, and the temperature difference between the batteries is minimal.

Support washer

This simple device is a disk made of steel not less than a millimeter thick with a hole drilled in it. It is placed on the flange of the elevator assembly between the circulation inserts. Washers are placed on both the supply and return pipes.

Important: for normal operation of the elevator assembly, the diameter of the holes of the retaining washers must be larger than the nozzle diameter.
Usually the difference is 1-2 millimeters.

Circulation pump

In autonomous heating systems, the head is created by one or more (by the number of independent circuits) circulating pumps. The most common devices - with a wet rotor - are a design with a common shaft for the impeller and rotor of the electric motor. The coolant serves as cooling and lubricating bearings.

Values

What is the pressure difference between different parts of the heating system?

Between the supply and return lines of the heating main, it is approximately 20 to 30 meters, or 2 to 3 kgf / cm2.

Help: excess pressure in one atmosphere raises the water column to a height of 10 meters.

The difference between the mixture after the elevator and the return pipeline is only 2 meters, or 0.2 kgf / cm2.
The drop on the retaining washer between the circulation cut-offs of the elevator unit rarely exceeds 1 meter.
The pressure created by the circulation pump with a wet rotor usually varies from 2 to 6 meters (0.2-0.6 kgf / cm2).

Adjustment

How to adjust the head in the elevator unit?

Support washer

To be precise, in the case of a retaining washer, it is not necessary to adjust the head, but to periodically replace the washer with a similar one due to the abrasive wear of the thin steel sheet in the process water. How to replace the washer with your own hands?

The instruction, in general, is quite simple:

All the valves or valves in the elevator are overlapped.
Opens one reset on the return and feed to drain the unit.
The bolts on the flange unscrew.
Instead of the old washer a new one is installed, equipped with a pair of gaskets - one on each side.

Tip: in the absence of a paronite, the washers are cut from the old car camera.
Do not forget to cut the eyelet, which will make the washer in the groove of the flange.

The bolts are pulled together in pairs, crosswise. After the gaskets are pressed, the nuts are screwed up to the stop no more than half a turn at a time. If you hurry, uneven compression sooner or later will cause the gasket to wring pressure from one side of the flange.

Heating system

The difference between the mixture and the return flow is regulated only by replacing, brewing or reaming the nozzle. However, sometimes it becomes necessary to remove the difference without stopping the heating (as a rule, with serious deviations from the temperature graph during the peak of cold weather).

This is done by adjusting the inlet valve on the return line; thus we remove the difference between the forward and reverse threads and, accordingly, between the mixture and the return flow.

We measure the pressure on the feed after the inlet valve.
We switch the DHW to the supply thread.
We screw the manometer into the resettable on the return.
Completely close the inlet return valve and then gradually open it until the drop decreases from the original by 0.2 kgf / cm2. Manipulation with closing and the subsequent opening of the gate valve is necessary in order for her cheeks to maximally descend on the rod. If you just cover the latch, the cheeks can persist later; the price of ridiculous time savings - at least unfrozen access heating.
The temperature of the return pipeline is monitored at intervals of 24 hours. If it is necessary to further reduce it, the difference is cleared by 0.2 atmospheres at a time.

Pressure in the autonomous circuit

The immediate meaning of the word "difference" is the level change, the fall. Within the framework of the article, we will also mention it. So, why does the pressure in the heating system drop if it is a closed loop?

To begin with, remember: the water is almost incompressible.

Excessive pressure in the circuit is created due to two factors:

Presence of a membrane expansion tank with its air cushion in the system.

Elasticity. Their elasticity tends to zero, but for a considerable area of the inner surface of the contour this factor also affects the internal pressure.

On the practical side, this means that the pressure drop recorded in the heating system in the heating system is usually caused by a very small change in the volume of the circuit or by a decrease in the amount of heat carrier.

And here is a possible list of both:

When heated, polypropylene expands more than water. When starting the heating system assembled from polypropylene, the pressure in it can drop slightly.
Many materials (including aluminum) are sufficiently plastic in order to change shape with prolonged exposure to moderate pressures. Aluminum radiators can simply swell with time.
Dissolved in water, gases gradually leave the circuit through the air vent, affecting the actual volume of water in it.
Significant heating of the coolant under low pressure can trigger the safety valve.

Finally, it is impossible to exclude also real faults: insignificant leaks on joints of sections and seams of welding, etching a nipple of an expansion tank and microcracks in a heat exchanger of a boiler.

In the photo there is an intersection leakage on a cast iron radiator. Often it can be seen only in the footsteps of rust.

Conclusion

We hope that we managed to answer the questions that the reader has accumulated. The video attached to the article, as usual, will offer him additional thematic materials. Good luck!

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

From this article you will find out what pressure in the heating system high-rise building is considered normal, the reasons for its differences and how to troubleshoot. Also, we will talk about methods for testing the contour for strength and.

Pressure in the central heating system

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

Distribution of temperatures and pressure in the elevator unit of an apartment building

The central city and housing and communal networks are separated by elevators. Elevator - a node through which the supply of coolant in the heating system of the high-rise. It mixes the flow and return flow, depending on what pressure is required to heat the apartment building. In the elevator construction there is a mixing chamber with an adjustable hole. It is 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 is mixed with water from the backflow and draws it into 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 the temperature in the radiators of the apartments and the change in pressure. The temperature in the house heating system at the entrance is 90 degrees.

The causes of pressure differences in the heating of an apartment building

The return pressure in the heating of apartment buildings is lower than the flow rate. The normal deviation is two bars. In the normal operating mode, the boiler plants supply the heat transfer medium to the system with a pressure of more than seven bar. The heating system of the high-rise reaches about six bars. The flow is affected by hydraulic resistance, as well as branches in housing and utility networks. At the return, the manometer will show four bars. Differential pressure in the heating of an apartment building can be caused by:

an air stopper;
leakage;
failure of system elements.

In practice, often there are differences. The pressure of water in the heating system of an apartment building largely depends on the internal diameter of the pipes and the temperature of the coolant. Technical marking of the conditional pass - DN. For spills pipes with conditional pass 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 cross section. Also, the feed 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 central heating system of the apartment building. Also the higher the return temperature. For stable operation of the heating system, the water from the return pipe must be a fixed temperature.

Elimination of differences

Arranging the nozzle of the elevator

When the return flow temperature and the pressure in the heating pipes change, apartment house, the diameter of the elevator nozzle is regulated. If necessary, it is reamed. This procedure should be agreed with the service provider (TEC or boiler house). You can not allow amateur performance. In extreme situations, when the system is being thawed under threat, the adjustment mechanism can be completely removed from the elevator. In this case, the coolant falls into the communications of the house unimpeded. 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.

The 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 reduction in the pressure in the heating of apartment buildings. In order to lower the temperature, it should be reduced. Here you can not do without welding. Then a new hole is drilled with a smaller diameter drill. This will reduce the amount of hot water in the mixing chamber of the elevator. This manipulation is carried out after the circulation of the coolant has stopped. If there is a need urgently, without stopping the system, reduce the return temperature, partially overlapping the valves. But this can be fraught with consequences. Metal shutters of the shut-off valves create a barrier in the coolant path. As a result, the pressure and frictional force increase. This increases the wear of the dampers. If it reaches a critical level, the flap can come off the regulator and completely block the flow.

Features of independent heating

The normal value for a closed loop is 1.5 -2.0 bar, which is much different from the pressure in central heating pipes. The reason for the decrease may be:

depressurization - when there is a leak or microcracks, through which water can escape. Visually, this can be imperceptible, since a small amount of water can evaporate;
reduction of the temperature of the coolant. The smaller the water temperature, the less its expansion;
the presence of autonomous pressure regulators, which bleed air. They are installed to remove air plugs. Often drip;
change in the radius of the conditional pass of the pipes. Plastic pipes when heated, they can change their geometry - they become wider.

From the pressure indicator in the heating system depends not only the circulation of the coolant, but also the serviceability of the equipment. To prevent a decrease and increase of pressure in any part of the system, an expansion tank is installed. This 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 exits at an extreme pressure increase. 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 left. 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 best radiator for the heating system

The temperature in the house also depends on the efficiency of the radiators. Manufacturers offer batteries of the following materials:

Each of the materials determines the working pressure of the radiator, its heat output and the heat transfer coefficient. Before you buy batteries, you should ask the Housing and Utilities Department about the pressure in central heating. In a private house and in a high-rise building, the pressure is different:

in private up to 3 bars;
the operating pressure in the heating system of the apartment building is 10 bar.

In addition, periodic checks of the reliability of the heating system, the so-called water hammers, should be taken into account.

And carried out in order to find out what pressure in the heating in the apartment, identify clogging, weaknesses and leaks. To remove dirt from the pipes, close the valve and drain the water. Then dial the complete system and repeat the procedure. It is allowed to use special means with high acidity. This requires equipment. To find a leak or weak point in the heating system of a multi-storey house, you must increase the pressure to 10 bar. If any connection fails this load, it must be reinforced or replaced. It is better to detect weak areas as a result of a hydrostatic attack in the summer. Since doing this kind of work in winter is much more difficult. This is due to the short period for which the system can be defrosted.