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The difference in pressure in the heating system of an apartment building. We define with terminology. Influence of coolant temperature

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 arrival 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 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 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 on the 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 the normal operation of the elevator assembly, the diameter of the holes of the retaining washers must be greater than the diameter of the nozzle.
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 are unscrewed.
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 strongly 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 leak on 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!

In a normally functioning heating system, a differential pressure is maintained between the direct pipeline, through which a coolant is supplied from the boiler or heating main, and the reverse one, through which it is fed to the next circle, passing through the radiators. For various objects it is 0.2-0.25 MPa or 2-2.5 atmosphere. It is thanks to this difference that there is a constant circulation of liquid in the circuit, and with the speed that is necessary to maintain a comfortable air temperature in all rooms.

Optimal parameters of working pressure in the heating circuit or pressure that provides 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 the difference of more than 0.02 MPa or 0.2 atmosphere is considered abnormal.

Normal operating pressure for various objects

One-storey house - 0,1-0,15 MPa or 1-1,5 atmosphere
   low-rise building (no more than three floors) - 0.2-0.4 MPa or 2-4 atmosphere;
   an apartment house of average height (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 monitored using pressure gauges installed in the most critical areas:

At the inlet and outlet of the mains with coolant (at centralized heating);
   Before and after the boiler individual heating);
   Before and after the circulation pump (when forced circulation);
   near the filters, valves and pressure regulators.

The consequences of pressure out of the norm

Even a slight deviation of pressure from the calculated index threatens at least temporary inconveniences. The temperature in some rooms may decrease, while others, on the contrary, may grow. In the event that the object of the hot water supply and heating system is combined into one, a lack of pressure can also cause a lack of water on the upper floors.

If there is a significant change in the drop for various reasons, modern equipment can automatically shut down, and the out-of-date equipment will fail. Old models of boilers that are not equipped with thermal control systems may even explode if the head falls, which is fraught with considerable damage.

What you need to do to maintain the necessary pressure drop in the heating system:

1. Observe the established standards for the design and installation of the heating system, primarily relating to the location of the forward and back risers relative to each other and the diameter of the pipelines.
   2. Take into account the change in the coolant pressure when its temperature changes.
   3. If it is not possible to provide the required differential with static pressure, use circulating pumps.
   4. To automatically adjust the working pressure in private houses, hydraulic accumulators are used, which make it possible to compensate for an insignificant out-of-tolerance by selecting a part of the coolant.
   5. In the apartment buildings a similar function is performed by pressure regulators installed on the pump bypass or between the forward and reverse risers.
   6. In some cases, pipelines are used to adjust the working pressure at large facilities, enabling the diameter of the pipeline to be altered by partially overlapping it.

The main causes of the drop in working pressure and how to eliminate them

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

Leaking of coolant;
   reduction of the volume of the coolant when the air contained in it is removed;
   decrease in the temperature of the coolant due to malfunctions of the boiler equipment;
   malfunctions of pumping equipment (in a system with forced circulation).

The presence of leaks is indicated by a drop in static pressure when the pump is switched off, as well as external signs of leaks on pipes and radiators. If the static pressure does not change, then the reason is in the pumping equipment. If the volume of the coolant is reduced due to the removal of the plugs, it is necessary to restore it, and when the temperature decreases, check the boiler.

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

   air system;
   heavy clogging of filters;
   mistaken adjustment or damage to the pressure regulator;
   increase in the volume of the heat carrier due to improper operation of the control automatics.

First of all, you should check the condition of the filters and air plugs in the system, and if necessary, clean the first ones and remove the second ones. The operation of the automation can be checked by turning off the system make-up capability. You can check the operation of the regulator by trying to adjust its settings.

Following a pressure failure in heating system the problem comes - the quality of the heating of the rooms in the house falls. You can, of course, adjust the heating operation once and for a long time, but this period will not be infinitely long. Once normal pressure in the heating system changes, and significantly. Therefore, the physical characteristics of the coolant, the elements of the heating circuit and heat appliances must be kept under control.

Depending on the current principle of the coolant flow in the heating circuit of the circuit, in the heating systems the main role is played by static or dynamic pressure.

Static pressure, also called gravitational, is developing because of the gravitational pull of our planet. The higher the water rises along the contour, the stronger its weight presses against the walls of the pipes. When the coolant is lifted to a height of 10 meters, the static pressure is 1 bar (0.981 atmosphere). The open heating system is designed for static pressure, its largest value is about 1.52 bar (1.5 atmosphere).

The correct piping will allow the boiler to be connected to the heating circuit in the way necessary for high-quality operation of the heating system

The dynamic pressure in the heating circuit develops artificially - the use of an electric pump. As a rule, closed heating systems are designed for dynamic pressure, the contour of which is formed by pipes of much smaller diameter than in open heating systems. Normal value of the dynamic pressure in the heating system closed type - 2.4 bar or 2.36 atmosphere.

Differential pressure in the heating system

Insufficient or higher pressure in the heat circuit is equally bad. In the first case, part of the radiators will not effectively heat the rooms, in the second - the integrity of the heating system will be violated, its individual elements will fail.

The increase in dynamic pressure in the heating pipeline occurs if:

the coolant is too hot;
the cross-section of the pipes is insufficient;
the boiler and the pipeline were overgrown with scum;
air congestion in the system;
too high a boost pump;
water is replenished.

Also, increased pressure in the closed loop causes incorrect balance of the cranes (the system is regulated) or the failure of individual valve regulators.

Pressure in the heating pipeline drops for the following reasons:

coolant leakage;
malfunction of the pump;
breakthrough of the expansionist membrane, cracks in the walls of a conventional expansion tank;
failure of the security unit;
leakage of water from the heating system into the feeding circuit.

Dynamic pressure will be increased if the cavities of pipes and radiators are clogged, if the filters are trapped. In such situations, the pump operates with increased load, and the efficiency of the heating circuit is reduced. The standard result of exceeding the pressure values are leaks in joints and even pipe rupture.

The pressure parameters will be lower than normal for normal operation if a pump with insufficient capacity is built in the pipeline. He will not be able to move the coolant at the required speed, so the device will be supplied with a somewhat cool working environment. The second vivid example of a pressure drop is the flow of the channel by a crane. A sign of these problems is the loss of pressure in a separate segment of the pipeline, located after the obstacle to the coolant.

Since all heat circuits have devices that protect against excessive pressure (at least, safety valve), the problem of low pressure happens much more often. Consider the causes of the fall and ways to increase the pressure, and therefore improve the circulation of water, in heating systems of open and closed type.

Pressure in an open heating system

Unlike the closed thermal circuit, a correctly constructed open heating system does not require balancing with years of operation - it is self-regulating. The operation of the boiler and the static pressure ensure a constant circulation of water in the system

The density of the heated water following the feeding riser is lower than the density of the cooled coolant. Hot water tends to occupy the highest point of the circuit, while the cooled water is at its very bottom.

The pressure necessary for the circulation of water is reached by the head in the feeder riser or by the boost pump (+)

The pressure developed by the water column in the supply riser promotes the circulation of the coolant and compensates for the resistance present in the pipeline of the circuit. It causes friction of water on the inner surface of the pipes, as well as local resistance (turns and branches of the pipeline, boiler, fittings). By the way, pipes of the raised diameter are used for assemblage of the open heating system with the purpose of decrease in a friction.

Understanding how to increase the pressure in an open heating system is impossible without considering the principle of achieving a circulating head in the heat circuit. His formula:

Pn = h (p o-p r), in which

Р ц - circulating pressure;
h - vertical distance between the center of the boiler and the lower radiator;
p r is the density of the heated coolant;
p o is the density of the cooled coolant.

Static pressure will be higher if the distance between the central axes of the boiler and the battery closest to it is as large as possible. Accordingly, the circulation rate of the coolant will be higher. To reach the maximum possible pressure in the heating circuit, it is necessary to lower the boiler as low as possible - to the basement.

The closer the radiator to the boiler is on the supply circuit, the better it gets warmer. Regulators allow to distribute heat between all radiators of the heating system

The second reason for the drop in pressure in an open heating system is associated with its self-regulation. When the heating temperature of the heating medium changes, the intensity of its flow changes. Increasing the heating of water for the heating circuit on cold winter days, the owners sharply reduce its density.

However, when passing through heating radiators, water gives off the heat to the room atmosphere, while its density increases. And according to the formula presented above, a high difference in densities of hot and chilled water contributes to the build-up of the circulation head.

The more the coolant warms up and the colder in the house, the higher the pressure in the system. However, after the atmosphere of the rooms has warmed up and the heat transfer of the radiators is reduced, the pressure in the open system will drop - the difference between the water temperature at the supply and the return will be reduced.

Balancing of a double-circuit open heat system

Gravitational heating systems are made with one or several circuits. In this case, the length of each looped pipeline horizontally should not exceed 30 m.

But to achieve optimum pressure and pressure in an open system with a natural movement of the coolant, it is better to make the pipelines even shorter - less than 25 m. Then it will be easier for water to deal with the hydraulic resistance. In a circuit with several rings, in addition to the length limitation, it is necessary to observe the condition for heating radiators - the number of sections in all rings should be approximately equal.

The lack of pressure in the open dual-circuit thermal system is due to design errors or pipeline contamination (+)

Balancing of horizontal rings entering into the vertical contour is required at the stage of designing the heating system. If the hydraulic resistance of any ring proves to be higher than that of the others, the static pressure in it will be insufficient and the head will practically stop.

In order to maintain the required pressure in the double-circuit heating system, it is required to reduce the cross-section of the pipes on the approach to the radiators. You can also install valves in front of the radiators that perform thermoregulation (manual or automatic).

Balance the two-circuit system open type can:

Manually. We start the heating system, then we measure the temperature of the atmosphere of each heated room. Where it is higher - we screw the valve, where below - we untwist. To adjust the heat balance, it is necessary to perform temperature measurements and adjust the valves several times;
Using thermostatic valves. Balancing occurs almost independently, you only need to set the desired temperature in each room on the handles of the valves. Each such device will control the flow of the coolant to the radiator itself, increasing or decreasing the flow of the coolant.

It is especially important that the total hydraulic resistance of the heating system (of all rings in the composition of the circuits) does not exceed the value of the circulation head. Otherwise, heating the coolant and trying to balance the system will not improve circulation.

Circulation pump for open heating system

It happens that the measures for balancing the heating circuit of the gravitational system do not give an effect. Not all causes of low pressure are solved by tuning - the choice of the wrong pipe diameter can not be corrected without a complete reconstruction of the contour.

Then, in order to increase the pressure and improve the movement of water without significant rework of heating, circulating or boosting pumps are installed in the system. The only thing that will require its installation is the transfer of the expansion tank or its replacement with a membrane expansion tank (closed tank).

With a serious drop in pressure, it is not a circulating pump, but a more powerful boost pump. However, for open systems heating pumps are not suitable; develop a significant dynamic pressure

The energy consumption of the circulation pumps does not exceed 100 W. Therefore, it is not necessary to fear that it will push the coolant out of the circuit. The volume of water in the heating system is more or less constant, subject to control over the filling of the open circuit. Therefore, no matter how much water the circulation pump does not push along the contour in front of it, the same amount will flow into it from the return pipe.

By bringing the pressure in the heat system to the required level, the pump will allow to extend it, reduce the diameter of the pipeline and reach the balance of the circuit at a high hydraulic resistance.

Pressure in a closed heating system

Installation of a modern boiler, especially a two-circuit, is called the sellers the ideal solution for home heating. With the qualitative installation of a new boiler closed system regularly serves for several years, but one day the pressure in it sharply or gradually decreases. How to find the cause of low dynamic pressure?

Closed heating system needs close attention. The fall or increase in pressure is equally dangerous for her. Staying without heating in winter is the worst nightmare of a homeowner

First of all, both the boost and the circulation pump in the heat circuit are checked. This device wears out faster than a boiler, expansion tank or pipeline, so its condition is determined first. It is important to make sure that the "silent" pump receives power and only then take steps to replace the device.

In general, it is more rational to build two pumps in advance in the heating circuit - one in the main pipe, the second in the bypass. Closed heating system can not operate at low dynamic pressure. Therefore, a spare pump, included in time, will protect the house and the pipeline from freezing.

If the pump is functional, the source of pressure loss is in the boiler or in the pipeline system. The boiler is checked last, first - the heating circuit.

How to find coolant leakage

It is possible to independently detect leaks in the heating system if the pipes are installed openly, there is access to the cranes and to all connecting elements. It is also necessary to remove the decorative cover of the heating radiators.

It is necessary to pass through the entire thermal circuit with a flashlight, carefully studying each connection, each element of the system (the piping of the boiler, too). We are looking for puddles of water, damp spots on the floor, traces of dried water, rusty stains on pipes, batteries and stop valves.

We take a small mirror, illuminate the flashlight and inspect the back of each section of the radiator. If the batteries are prefabricated, made of cast iron or aluminum, you should inspect the connections between the sections. Corrosion, rust staining is a sign of leakage, even if the floor is dry under the radiator.

There are situations when the pressure in the circuit falls slowly, day by day. And there are no distinguishable signs of leakage on the elements of the heating system or on the floor. Rather, there are leakages and there are many of them, but they can not be detected.

Leaking water evaporates on a pipe, radiator or on a floor surface, i.e. no appreciable puddles are formed. It is necessary to identify the places of possible flow of coolant, lay under them sheets of soft paper - you can use napkins or toilet paper. After a few hours, check the paper for moisture. If wet - means a leak here.

The serviceability of the boiler safety group is not only in the operation of a pressure gauge, safety valve and air vent. No element or plug-in connection should flow

In a house equipped with a partially hidden system of a heating pipeline, it is impossible to find leaks on its own. It remains only to call the heat engineers, who will perform a search for leaks in the heat circuit with the help of special equipment.

Thermotechnical leak detection in the heating system is performed in a certain sequence. First, the coolant flows out of the circuit. Then, the whole pipeline or its individual segments equipped with shut-off valves is connected via a screwed connection to the compressor. In the extreme version, you can connect the car pump to the pipeline.

After a few minutes from the beginning of the injection of air into the thermal circuit, a distinct sound of the outgoing air can be heard in the leakage areas. Each wall of the heating system, embedded in the wall or floor, must be opened from the cement screed with sound leakage. Further, the leakage is eliminated by replacing the segment of pipes, by tightening the connection with the rewinding of the pakli or the ribbon belt, by removing and installing a new stop valve.

Pressure drops in the boiler

We note at once that only the engineer-heat engineer of the service department is able to determine the exact breakdown of the boiler equipment. Those. independently to find out and, moreover, to eliminate the serious breakdown that caused the pressure drop in the boiler, the landlord will not be able to. Let us consider the possible reasons for the "creeping" pressure change on the boiler manometer, which occurs when the boiler is in an external condition.

A crack in the heat exchanger. Over the years, the walls of the heat exchanger in the boiler can get microcracks. The reasons for their formation are the deterioration of the aggregate, the weakening of the strength during flushing, the pressure testing (hydraulic shock), or factory mar- riage. The coolant flows through them and the boiler needs water make-up every 3-5 days. Visually, leaks can not be detected - the water flows weakly, when the burner is switched on, the moisture accumulated in the boiler evaporates. It is necessary to replace the heat exchanger, it is less likely to dissipate it.

The three-way valve is ideal for multi-ring heating systems. However, the capacity of such a crane is strongly related to how often it will be cleaned of contaminants

The pressure rises due to an open tap make-up. Against the background of low dynamic pressure in the boiler and more high pressure in the water pipe, through the make-up tap in the heating system comes "extra" water. The pressure in the heating circuit increases until the moment that it needs to be vented through the safety valve of the boiler unit.

If the pressure in the water pipe drops, the heating medium of the heating circuit will transfer it to the boiler, then the pressure in the heating system will decrease. A similar problem occurs with a faulty make-up tap. It is required to either close the valve or replace it.

Pressure growth due to a three-way valve. If the valve installed on the double-circuit boiler fails, the water from the "economic" heating sector will flow into the heating system. A three-way valve requires cleaning or replacement.

The display of the boiler manometer does not change. If, with changes in the operating conditions of the boiler, with an increase or decrease in temperature in the circuit, the pressure gauge shows the same pressure - it "freezes". Those. Through a branch pipe in it the dirt from heating system was filled. Requires replacement of a pressure gauge.

Low pressure due to expansion tank

With double-circuit boilers in closed heating systems, this situation often occurs: when starting in heating mode, the pressure on the boiler gauge increases dramatically. If the circuit is completely filled with water - the pressure rises to 3 bar and the discharge valve is activated, which drops some of the water.

The landlord turns off the burner and waits for the water to cool. At the same time, the pressure drops to a minimum. Next, the owner then tries to turn on the boiler. But the unit does not work, it signals "accident". Although sometimes it is possible to activate the operation of a double-circuit boiler, if the pressure does not decrease too much.

The position of the expansion tank near the boiler is explained by its importance for the heat system. The condition and serviceability of the expansion tank should be closely monitored

It remains only to try to raise the pressure by adding water to the system in the "cold" mode (with the burner switched off) and having obtained the gauge reading at the level of 1.2-1.5 bar. But the restart of the boiler occurs with the same result: the pressure increases; the reset valve is activated; the water is drained; pressure at a minimum; the boiler does not want to work. There can be several reasons for this malfunction. However, a frequent source of the problem is the expansion tank. And it does not matter where it is located - inside the boiler or outside it.

Expansomate is divided by a flexible membrane into two parts. In one heat carrier, in another gas (usually nitrogen) at a pressure of 1.5 bar. The water that expands during heating, contained in the thermal circuit, presses through the membrane to the gas compartment of the membrane tank. To compensate for the increased pressure in the system, the gas in the expansion vessel contracts.

After years of using the closed heating circuit, the nipple, through which the gas was pumped into the surge tank, begins to flow. It happens that the gas is dropped by the homeowners themselves, who do not understand the purpose of the nipple. In any variant of events, the gas in the expansion vessel becomes smaller and smaller. Soon, the expansion tank is no longer able to compensate for the pressure of the expanding coolant in the system, its values reach a maximum.

For the failure of the expansion tank, the closed heating system will react with a sudden take-off and a drop in the dynamic pressure

We'll figure out how to solve the problem with a lack of gas in the expansion. First turn off the boiler, if it is electric - from the mains too. If the expansion tank is integrated in the boiler, the access of water to both its circuits (or one) must be blocked. Drain the water completely from the boiler. If the expansion tank is located separately from the boiler, it is necessary to "his" fragment of the pipeline from the common network and drain the water from there.

After you take the car pump equipped with a manometer (you need a manometer), attach it to the nipple on the expansion tank and pump it up. From the blocked sector of the pipeline (or boiler, if the tank is in it) will go water - swing further. We follow the pump manometer. Water ceased to flow, and the pressure reached 1.2-1.5 bar - stop pumping air.

It remains to open the shut-off valves, feed the circuit with water to 1.2-1.5 bar, after turning on the boiler. The heating system will work. Having discovered that the pressure problem has reappeared after a while - replace the nipple of the expansomate, it flows heavily. Note that there may be another problem with the tank, more complicated is the rupture of the membrane. Then pumping with air will not help, you will have to change the expansometer.

Video about pressure adjustment methods

How to balance heating radiators in a home heating system. Recall that without the valves on each heating radiator to balance the system does not work.

A well-balanced heating system will perform its functions for several years. But one day the characteristics of the coolant will change or the responsible elements of the thermal circuit fail. Therefore, the monitoring of the coolant through the manometers should be kept constantly, in order to respond in a timely manner to pressure drops.

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. We will also discuss methods for testing the contour for strength and choosing the best radiators for the system.

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 construction of the elevator 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

Return pressure in heating apartment buildings lower than the filing. 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 in the apartment building are lowered, 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

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.

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 inclusion in work circulating pump The effect on the internal surfaces of 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 involves the presence of a circulating pump and an expansion tank of a 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 note as 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. For compensation of the volume of the expanding coolant and a sharp pressure jump responds expansion tank, which can be closed or open type.

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.