Dependent scheme of connection to thermal networks. Dependent and independent heating system

The growing popularity of autonomous engineering tools already at the stage of designing a house inclines the future owner towards an independent heating system. This is far from perfect solution, but many are willing to pay for its benefits. Moreover, the possibility of savings with such a choice is not completely swept aside. But there are also issues of safety, reliability and ergonomics of using equipment, therefore both dependent and independent heating systems should be considered in detail and with an emphasis on specific conditions of use. In this case, the most pronounced features and differences of each of these concepts will be noted.

Dependent heating system

The central link of such communications is the elevator unit, through which the tasks of regulating the coolant are performed. From the heating main to the distribution unit of a residential building, water is supplied through a pipeline, and mechanical control is carried out by a system of inlet valves and valves - typical plumbing fittings. On the next level are locking mechanisms, which regulate the supply hot water return and input circuits. Moreover, the heating system in the private country house can provide for two tie-ins - for the return line and the supply channel. Further, the home tie-ins are followed by a chamber in which the heat carriers are mixed. Hot streams can indirectly contact water in the return circuit, transferring some of the heat to it. Summarizing this part, we can conclude that the water is directed to DHW system directly from the central heating main.

Independent heating system

The principal feature of this system is the presence of an intermediate collection point. In residential private houses, it can be implemented as a control station (including for pressure reduction), but this scheme is made independent by the integration of a heat exchanger. It performs the functions of a rational and balanced redistribution of hot flows, also maintaining, if necessary, an optimal temperature regime. That is, at independent accession heating systems, the heating network as such does not act as a direct source of supply, but only directs flows to an intermediate technological point. Further from it, in accordance with the settings made, in a more point version, supply and drinking water, and hot water supply with heating and other household needs.

Comparison by the degree of dependence on electricity supply

Energy independence in this case refers to the absence of electricity. In other words, how communications will be able to continue their work if, for one reason or another, the light is turned off. Are there any differences in principle between dependent and independent heating systems in this aspect, because both infrastructures can provide for the operation of energy-intensive boilers? Indeed, in practice, most often both systems are equal in this regard, but the scheme of dependent connection to the central heating network itself can do without electrical equipment and supply the consumer all year round even without light - of course, if there are no other kinds of failures. In the case of an independent system, even with minimal equipment, the same presence of a collector unit with automation is more likely to make the system inoperative or cut in functionality for an emergency period in the power grid.

Comparison for reliability and durability

The practice of operating technically complex and multi-level systems shows that they are less maintainable and more often must be subjected to preventive examinations with service activities. It cannot be said that the independent connection of the heating system reduces the overall level of reliability and safety (in some cases even increases), but the tactics of carrying out repair and restoration measures should be at a different and more responsible level.

At a minimum, an increase in labor and time resources will be required when inspecting the heat exchanger and adjacent piping. Possible uncontrolled accidents at this node can lead to damage to the pipeline. Therefore, experts recommend installing several sensors with pressure, temperature and tightness control. The latest collector cabinets also provide for the use of self-diagnostic complexes for continuous monitoring of the system status. As for the closed heating infrastructure, such control and measuring fittings will also not be superfluous for it, but in this case its need is not so high.

Ergonomic comparison

In fact, all of the above disadvantages are not dependent systems are determined by the desire of users to obtain both an easy-to-use and economical means of heating. How is this achieved? It is due to the intermediate control and distribution unit connected to the heat exchanger. The main differences between independent and dependent heating systems in terms of control are that in the first case a wider range of options is provided for fine-tuning parameters DHW operation. In particular, automatic control means allow you to program the distribution of heat in given volumes and according to the intended contours for certain time intervals - from hours and days to weeks.

Advantages of dependent heating systems

In addition to the already mentioned reliability and reduced maintenance costs (at least on the part of the user), one can emphasize the rather high performance and stable maintenance of the hot water temperature at an average level of 95 ºС to 105 ºС. At the same time, both dependent and independent heating systems can equally regulate the thermal regime. Only in the first case, public utilities will be responsible for this regulation, integrating radiators into distribution systems for mixing water with different temperatures. Precisely for apartment buildings This is the optimal solution in terms of performance and financial feasibility.

Cons of dependent heating systems

From negative sides operation of such systems note the following:

• Intensive contamination of working circuits with scale, dirt, rust and all kinds of impurities that may well enter consumer equipment.
• Higher requirements for repair activities. The fact is that dependent and independent heating systems in such cases require the connection of specialists of different levels. It is one thing to make repairs on the main line once a year, and another thing is to perform a comprehensive inspection of the piping monthly. elevator node at home.
• Water hammer is possible. Incorrect connection of communications or excessive high pressure in the circuit can lead to pipe ruptures.
• Low basic quality of the coolant in terms of composition.
• Difficulties of control and management. At technological stations of municipal water heating, the process of updating the same stop valves proceeds rather slowly, hence disturbances in pressure balances may occur.

Advantages of independent systems

Already on the way to the main consumers home network water supply is provided with a whole range of preparatory measures that ensure the distribution, filtration and pressure adjustment of the coolant. All loads fall not on the final equipment, but on the heat exchanger with a hydraulic tank, which directly receive resources from the main source. Such resource preparation is practically impossible in private during the operation of systems dependent heating. The connection of an independent circuit also allows rational use of water for drinking needs of optimal purification. The streams are divided according to the intended purpose and each line can provide a separate level of training that meets the technological requirements.

Cons of an independent heating system

Of course, the introduction of additional regulatory and instrumentation equipment into the infrastructure will cost a lot. If we take into account the use of a boiler or radiator with the support of a circulation pump as the main heating unit, then we can talk about 500-700 thousand rubles. In this respect, dependent and independent heating systems diverge radically. By the way, a dependent connection can do without tangible costs. Another thing is that in a private house, owners usually introduce fairly efficient boilers and boilers into the network. In addition, high security requirements are also noted among the shortcomings. This does not mean that a stand-alone circuit with several layers of piping is in itself a great danger, but expanding the network with connection to a dozen intermediate devices imposes a great responsibility on the user when operating the system.

Dependent coolant connection lines are now perceived as obsolete, and independent lines are perceived as more functional, balanced and ergonomic solution. But what heating system is suitable if we are talking about an average private house with a typical amount of energy consumption? Initially, you can focus on certain configurations of independent systems, but do not forget about the following nuances:

• If there are technical difficulties in arranging heating equipment, then a dependent system will be more justified.
• If there are periodic power outages, then along with the heat exchanger, you will also have to purchase an autonomous generator.
• The longer it lasts heating period, the more profitable will be the transition to a dependent system.
• For dachas and, in principle, low-cost objects in terms of thermal energy, in the long term, it is advisable to make a choice in favor of an independent connection.

Can one system be converted into another?

Theoretically, this is quite possible - both in one direction and in the other. Basically, they just modernize dependent systems, but there may well be a need to reconstruct independent infrastructure. At the same time, the most rational option, when it will be possible to preserve the advantages of both systems to varying degrees, will be the implementation of an independent heating system with closed input circuits. This means that those functions that in the standard independent circuit were performed by a separate collector block with full set control units, in this case they will take over installed devices. On the different levels already in the home network, before approaching consumers, it is possible to insert filters, compressor units, distributors, circulation pumps and a hydraulic tank.

Conclusion

Yet decisive factor in choosing one or another heating system rightly remains safety. And if in one case employees of service organizations will be responsible for it, then in another, these tasks will be taken over to a large extent by the user himself. And in both situations, experts recommend periodically ordering a service. independent expertise heating system, which will allow you to professionally assess the current state of the pipeline and adjacent circuits with technological equipment. By the way, this is especially important for residents who use the communications of old houses. In such cases, a comprehensive diagnosis of the connection to the heating network, checking the tightness and compliance of the insulation with the established requirements should be carried out regularly.

Of course, living in your own home has a huge number of advantages compared to living in an apartment in an apartment building: clean air, the absence of constantly rattling or annoying neighbors, the possibility of creating all kinds of design and interior, both internal and external. Great importance during the construction of the house, it has a properly selected heating system, which can be based on both an independent and a dependent heat supply scheme. What is it and how they differ - in our article.

The fundamental difference between the two schemes

First of all, you need to figure out what an independent heating system is. Surely many of you will think that such a unit is a system that is able to function without providing it with power. However, this is not quite true. A dependent heating system operates from a centralized main, while an independent one, respectively, operates at the expense of individual resources.

In addition, the dependent heat supply scheme is fully subordinated to the source of its energy supply. It is a heating boiler, a pipeline circuit and a system of radiators, which are combined with a heat main. The heat carrier, which, as a rule, is hot water, continuously functions through the system, creating the necessary temperature conditions in the house. Such a heating installation does not allow adjusting the supply water, and homeowners are forced to wait until the end heating season to make the installation stop working. Such a heating system is practiced in the vast majority of apartments in the secondary housing stock, with the exception of those where individual heating is installed.

Mainly used in new buildings autonomous system heating, which allows residents to independently determine the temperature of the coolant, the time and end of the heating season.

Main characteristics of an independent heating system

An independent scheme for connecting the heating system operates autonomously and does not depend on centralized energy resources. Of course, the installation of such a heating unit will cost several times more than the installation of a dependent unit, but at the same time it has a number of advantages:

1. The use of technical water for domestic purposes.
2. Despite the fact that the purchase and installation of components, Supplies and functional equipment will cost you not so cheap, the savings will be felt on the consumption of fuel resources.
3. Adjustable and comfortable temperature conditions for living.
4. Dependent and independent heat supply system also differs in the type of coolant. In the first case, the highway circulates industrial water, in which there are all kinds of impurities (sand, salts, etc.), which eventually clog the circuit, preventing the full movement of the coolant. And this, in turn, leads to a decrease in the temperature regime inside the heated room. Whereas in the case of an independent heating unit, the homeowner can easily use purified water as a heating medium. This will not only prevent blockage of the heating main, but also extend the operational life of the functional equipment used to construct such a unit.
5. There is another difference between these two home heating options. So, absolutely all boiler houses, through which it is provided centralized heating, operate on electricity and as soon as power failures occur, the water in the circuit begins to cool. In turn, an independent heating system can fully function without electric power resources. Can buy a heating element operating on solid fuels. Such a unit is a metal container equipped with a thermostat and mechanical adjustment devices. This version of the heating block will allow you to avoid being tied to a centralized gas pipeline. But at the same time, there are also some difficulties in using equipment of this kind. So, from time to time there is a need to load fuel into the blower. Therefore, in order to simplify the task experienced professionals it is recommended to make bunkers and conveyors through which fuel materials are supplied. Can be used as energy wooden saw cuts, because without electricity, unfortunately, you will not be able to start the conveyor.

This, in fact, is the whole difference between a dependent and independent heat supply system. And if you live in a large private house, then you will surely appreciate the benefits the last way home heating.

VIDEO: Analysis of the heating scheme

Varieties of boilers

A properly selected and installed heating boiler is the key to an efficient heating system!

As a rule, the choice of a heating device is based on the specifics of the use of a particular type of fuel. There are also combined options, allowing the use of two or three types of fuel, depending on its availability and availability.

Operating on gas

The simplest and most popular option for the device heating system private house. First, compared to other energy resources, gas is the safest and most profitable. Secondly, such equipment is an automatic installation that does not require the constant presence of a person. You only need to set up the unit once and you can forget about it for a long time.

Without a centralized gas supply, such a unit will not work for a long time. It is extremely difficult and economically impractical to change cylinders filled with gas with enviable regularity to ensure full heating of the room.

Electric boilers

Such models are suitable for heating private houses where there is no possibility of connecting to a centralized gas pipeline. But again, power outages can lead to cooling of the coolant, which is not very comfortable in winter time of the year. And on accumulating devices, it is unlikely to work for a long time. And besides, this heating option will not be so cheap.

Working with electrodes

Instead of a heating element, electrodes are installed in such equipment, due to which water is ionized and, as a result, it is heated. This option is not as popular as the previous one, but at the same time it is much safer and more durable.

True, such a device will have to be readjusted regularly and constantly monitor the quality of the incoming water, on which the efficiency of the unit largely depends.

Solid fuel units

The highest quality example of an independent heating system. Such units are also divided into several types depending on the type of fuel. So, carbide boilers can work on:

• firewood;
• coal and coke;
• pellets made from wood waste.

In addition, there are still such models that can function both on wood and on coal. Combinations such as electricity + coal, firewood + electricity, etc. are also known.

Oil boilers

Such heating equipment runs on diesel fuel. It can also be safely called an independent heat source. But at the same time, unlike the previous version, the cost of this type of fuel is getting higher and higher every year, so today not many people decide to equip their homes with such heating installations.

As you can see, heating a private house can be done using all kinds of equipment and energy resources. The choice is always up to the homeowner!

VIDEO: An example of heating a private house

To understand how a dependent and independent heating system differs, it is necessary to give a clear definition of these concepts in order to avoid confusion in the future:

• Independence implies isolation from an external public heating main. It can be said that a two-circuit network is being implemented in order to avoid mixing the coolants of the first and second stages. Heat is transferred in a special device called a heat exchanger.

• Addiction is the inability to self adjustment coolant temperature, start and stop the system according to an individual schedule according to the climatic situation. Hard anchor to item district heating, which adjusts network settings as you see fit.

Each of the two heating options has both individual benefits, as well as their shortcomings, which follow from the design features and the principle of operation.

Independent heating system and its types

An independent heating system is divided, in turn, into two subspecies according to the implementation of the method of circulating an energy carrier in pipelines:

1. Gravitational, otherwise called non-volatile. The liquid moves through the pipes due to the different densities of cold and heated substances. Therefore, the heated carrier coming from the heat exchanger tends upward due to the lower specific gravity, cold, on the contrary, settles at the lowest points of the heating main. This feature imposes several strict requirements for the possibility of full functioning:

• A heat exchange device or a water boiler, if the heating is autonomous, must be placed at the lowest point of the building. If radiators are also installed on this floor, then a pit below the floor level will have to be equipped.
• All horizontally laid pipelines should be fixed at a slope of two to three degrees in the direction of movement of the coolant in the pipe. That is, the feed will have a positive angle relative to the common vector, and the return will have a negative angle.
• To minimize negative impact hydraulic resistance, the passage diameter of the pipes must be large. For two-storey cottage with five to seven heated rooms, a diameter of 35 millimeters will suffice. The more-better principle is fully at work here.

1. Circulating or volatile. The heat carriers of the centralized supply system and the hydraulics of heat distribution do not have physical contact together. The transfer of heat from one to the other occurs in the so-called heat exchanger, which is a tank in which tubes with liquid circulating through them are located. That is, an independent connection of the heating system realizes the possibility of flexible adjustment of the temperature regime of heated structures, simplification of modification and expansion of the network and saving on heating costs. There are also features:

• The cost of construction significantly exceeds the cost of the first method.
• Increased requirements are imposed on the quality of secondary circuit coolants.
• Almost always there is a need for a continuous power supply to ensure the circulation process.

Safety and efficiency of independent heating systems

To be able to save money on heating, several conditions must be met:

1. Develop and approve the project in the licensing authorities. Without the approved GUI and agreed with all project authorities, all modifications will be illegal. Therefore, the results cannot be used.
2. Perform installation or reconstruction of existing equipment according to the design solution.
3. Install a heat energy meter. This will allow you to pay for the received thermal energy exactly in the volume in which it was consumed.
4. Provide required level automation or manual control. CHP does not react very quickly to temperature changes weather conditions and can continue to fire their boilers to the fullest. And through the heat exchange tank, unclaimed energy will be transferred to the networks of consumers who open windows and vents from excessive heat.

Installation and connection of an independent heating system

Installation work in its complexity is not much more complicated than the gravity route. Of the additional measures, it is worth noting the need to organize an uninterruptible power supply. This will make it possible not to be left without heat during a power outage and is realized at the expense of automatic start an uninterruptible power supply or a liquid fuel electric generator.

In addition, the operating routes of a centralized type are also subject to modernization by separating heat carriers with a heat exchange tank, installing a forced circulation pump and an uninterruptible power supply. Replacement or dismantling of pipelines with radiators is not required.

Due to the fact that a certain set of documents is required, it is recommended to start with obtaining a design solution. This sequence avoids wasting time and wasting money on materials.

The heat supply system is one of the most important components of every residential building. Its main task is to provide thermal comfort for people in the premises. All central heating systems are connected according to a certain scheme - dependent or independent. These heat supply systems differ in the way they are connected and have fundamental differences. Independent heating system on this moment is gaining more and more popularity.

Independent heating system. Click on the photo to enlarge.

Dependent connection

It can be performed in two versions: directly or using a mixing unit.
If the connection is made according to the first option, then the superheated water from the heating networks is mixed in the boiler (in a certain volume) with the returning water from the heating system. In this way, the water acquires a sufficient temperature, up to approximately 100 0 . Its value depends on the power of the boiler. The temperature may be higher. Then it enters the heating source. Thermal points are supplied with pump mixers and water-jet elevators. To create an optimal indoor air temperature, low-temperature water is added to the pipeline, reducing the temperature regime. The second connection option implies that the hot and cold water are mixed, and the coolant liquid with a temperature of 70-80 0 C is sent to the heating radiators of residential buildings.

Dependent wiring diagram. Click on the photo to enlarge.

Direct connection can be used directly in low temperature heating networks, where a two-pipe system with radiator throttling thermostats is made. Here, the parameters of heat carriers are constant throughout the year. Heating network reflect changes in consumer demand in terms of thermal volume, through instruments showing the pressure drop at the inlets. With their help, electronic regulators change the supply of common pumps of the heating network.

regulate this system can only be quantitative. The circulation of the heat source of the dependent circuit is carried out through differences in the values ​​of water pressure in the areas of connection to the elements outdoor system heating. Dependent connection and its connection scheme with a water mixing unit is structurally simple and easy to maintain.

The cost of the scheme is greatly reduced by eliminating some structural elements. A dependent scheme is selected if the heat-consuming system, including the heating system (according to sanitary and hygienic recommendations) allows an increase in hydraulic pressure to the value of the water pressure outside when it enters the heat pipeline. For some time, the dependent scheme was popular in Russia, due to the ratio of its pros and cons.

Node independent heating system. Click on the photo to enlarge.

Advantages and disadvantages of a dependent heating system

Advantages:

• quick payback;
• easy and inexpensive maintenance.

Disadvantages:

• the inability to adjust the temperature regime in the premises;
• the possibility of using only certain equipment of the system, suitable for the requirements of the plant (systems of this kind must withstand high pressure and water hammer during start-up);
• regular measures are required to protect equipment from the hardness of salts dissolved in the coolant and oxygen exposure, in order to avoid corrosion;
• overexpenditure of consumed energy resources.

Connection according to an independent scheme

An independent heating system looks completely different. If the elements are connected according to an independent scheme, then the water in the boiler is heated to approximately 150 0, after which, through a special heat exchange equipment goes to the main coolant. The main coolant is used for circulation in closed loop heated residential building. In this case, water does not mix.

The heating point is equipped with a circulation pump to provide pressure and water heat exchangers. Application of a set of measures for energy saving of the system: the use of modern, electronic coolant temperature controllers, circulation pumps with adjustable speed, metering devices for consumed thermal energy. Application of a set of measures to ensure the reliability of operation: special design of the heating system of the entire settlement, looping them with the possibility of emergency switching of consumers to various sources thermal supply.

Schematic diagram of connection by independent system. Click on the photo to enlarge.

An independent connection scheme is used if an increase in hydraulic pressure is unacceptable in the engineering scheme (from the condition of system strength). That is, the water pressure in the outer pipeline must be greater than the pressure in the inner pipeline. In addition to implementing an unchanging thermal hydraulic mode under external influences, selected for each building separately, independent heating is characterized by increased reliability.

It is endowed with the ability to maintain circulation with the participation of the content in the water a certain amount heat, for a certain period of time, which is approximately enough to eliminate unforeseen emergencies in case of malfunctions of the external heat pipeline.

The hydraulic mode of connection with an independent circuit does not depend on external elements engineering system. AT open systems providing heat, the considered connection of the heating system improves the quality of the water coming through the hot water supply installations. At the same time, the connection scheme is configured so that water does not pass through heating appliances, which serve as cesspools for various kinds mud.

The principle of operation of an independent circuit. Click on the photo to enlarge.

Advantages and disadvantages of an independent heating system

Advantages:

• the possibility of flexible adjustment of the temperature regime in the premises (the heat carrier is isolated from the heat carrier boiler of the heating system) by maintaining the required pressure;
• the possibility of using different chemical composition of the coolant;
• obtaining the effect of energy saving, saving heat from 10 to 40%;
• possibility effective organization heat supply systems with a significant distance and territorial dispersion of consumers;
• the heating system shows a high level of reliability;
• improving the quality of hot water supply.

Disadvantages:

• huge maintenance costs are required;
• laborious and costly repairs.

Elements of an independent heating system. Click on the photo to enlarge.

AT closed systems, made in dependent or independent heating circuits, hot water heaters are connected to the heating network mainly in parallel, mixed and sequential options. When choosing the best option relation is taken into account maximum load, calculated for heating, to the load of hot water supply, which is used in some areas. This is done using temperature chart centralized regulation release of heat received in subscriber thermal energy-consuming devices.

The heating system, which uses dependent connection, has now lost its distribution. AT modern construction only an independent heating circuit is used. AT modern world they have all the important benefits modern systems heat supply, despite the large financial costs and investments. The transition to independent heating is happening everywhere. Sometimes used combined scheme local accession heating point using both dependent and independent heating systems.

WATER HEATING SYSTEMS

The scheme for connecting heating systems to heating networks depends on: the need to reduce the potential at the input; available pressure drop at the inlet; pressure in the return line of the heating network at the point of connection of the heating system.

1. Direct connection of the heating system to the heating network.

Without lowering the water temperature, heating systems of industrial buildings are directly connected to the heating network, in which, according to the norms, it is allowed fever coolant up to 150 ºС (rice. 2.1).

Rice. 2.1. Scheme of connecting the heating system to the heating network

2. Connection of heating systems through the elevator.

Maximum temperature water in the supply line of the heating network, as a rule, is equal to 150 ºС(SNiP), but in some systems it reaches 170 - 190 ºС. The maximum water temperature in the local heating system, according to sanitary and hygienic standards, should not exceed 95 - 105 ºС. To lower the water temperature in the supply line of the heating system, elevators are used ( rice. 2.2a).

Rice. 2.2. Scheme of connecting the heating system to the thermal

networks - a, structural diagram of the elevator - b: 1 - nozzle

elevator; 2 – mixing chamber; 3 - neck

The elevator performs two functions - it serves as a mixer and a circulation booster in the heating system. The elevator was developed by Professor Chaplin in the 20s and has been widely used in the country since then ( rice. 2.2b).

Advantages: simplicity of design and reliability in operation. Mixing ratio:

The required mixing ratio of the elevator is provided with pressure fluctuations at the inlet; its changes are very small.

disadvantages: low efficiency (10-15%) and the impossibility of connection in the end sections of the heating network at low pressure drops, insufficient for the operation of the elevator; in the event of an accident in the heating network, it is impossible to ensure autonomous circulation of water in local heating systems, which, if low temperatures outdoor air leads to a strong cooling of the premises; constant equality rigidly binds the hydraulic and temperature conditions in local heating systems and heating networks. At high temperatures outside air (fracture), which does not allow to reduce G ts of water in the heating system. At a constant mixing ratio with decreasing G ts decreases G under, hence decreasing G o, which leads to misalignment of heating systems.

Available pressure in front of the elevator:

, m v.st, (2.2)

where ΔР C - pressure loss in the heating system, m w.st.

If a ΔР C = 1 m w.st, U = 1, therefore ΔР E = 6 m w.st.

To remedy shortcomings in last years elevators with adjustable nozzle, i.e. elevators with variable adjustable nozzle section.

Rice. 2.3. Structural scheme Elevator with adjustable nozzle:

1 - nozzle; 2 – mixing chamber; 3 - neck;

4 - regulating needle; 5 - the source of the regulating needle;

6 - mechanism for moving the needle

Such elevators allow, within certain limits, to change the mixing ratio.

Significantly greater possibilities for regulating the heating system have a connection scheme with mixing pumps. The pump can be located on the supply, on the return and on the jumper between T1 and T2.

3. Jumper pump.

Rice. 2.4. Heating control schemes

The pump, installed on the jumper, takes water from the return line of the heating system and supplies it for mixing with hot water coming from the heating network ( rice. 2.4a).

At emergency shutdown heating network, the pump circulates water in local heating systems, which prevents it from freezing for a relatively long period (8-12 h): G n = G subm; ΔN n = ΔN AB

4. Pump for supply or return.

In the end sections of the heating network, where connection schemes with a mixing pump are usually used, the pressure difference is not only small, but also subject to daily and seasonal fluctuations. These fluctuations are sometimes so significant that they can lead to shortfalls in required amount network water and heat to consumers. It is in these cases that the installation of the pump on the supply or return makes it possible to obtain additional necessary circulation during the operation of the pump ( rice. 2.4.b).

The circuit with a return pump is of greater use, because. in the end sections of the heating network, where these schemes are most useful, often the pressure in the return line is increased. However, in these cases, one should take into account the possible stop of the circulation pump and at the same time prevent the pressure in the heating system from exceeding the working one. If the pressure in the heating system when the pump stops exceeds R slave. , it is more reliable to use an independent heating system.

When heating tall buildings or located at high elevations, sometimes a scheme with a supply pump is used ( rice. 2.4v), but, as a rule, in this case, one should also give preference to an independent scheme: G n = G about.

The presence of pumps in these schemes allows for a more perfect regulation of the heating system.

Only low-noise foundationless pumps are allowed for installation.

To simplify and clarify the regulation of heating systems, they should have a flat characteristic. In this case, regardless of the amount of water supplied from the network, the heating system will operate at a constant flow rate. circulating water, which will ensure its correct distribution over the risers and heating devices.

Rice. 2.4. Pump operation schedule: 1-characteristic of the pump;

2-characteristic of the network.

With all pump mixing schemes, turning off the pump leads to the flow of hot water from the heating network into the heating system, which can lead to its damage. True, the amount of incoming water will be small, because. the pressure loss in the system is several times higher than the pressure loss in the jumper at the pump. It is necessary to provide protective device, which would completely turn off the heating system when the pumps stop completely.

Must be installed with a working and standby pump.

All these shortcomings pumping systems led to the creation of a scheme that combines both an elevator and a pump ( rice. 2.4g).

5. Scheme with an elevator and a pump.

In this case, the failure of the pump will lead to a decrease in the mixing ratio, but will not reduce it to zero, as in schemes with pure pump mixing.

These schemes can be applied when the pressure difference in front of the elevator ΔN EL cannot provide the required mixing ratio, but not less than 5 m.v.st.

Using this scheme, it is possible to carry out stepwise regulation of the temperature of the supplied water in the fracture zone. The duration of the turning point is from 0-10 ºС can reach 1000 or more hours during the heating period. Overexpenditure of heat for heating during this period due to the supply of water to the network with a temperature of 70-75 ºС unwanted.

Installing a pump at the input with a normally operating elevator allows, when the pump is turned on, to increase the mixing ratio, and therefore reduce the temperature t 1 in the heating system.

6. Scheme with a pressure regulator.

When designing a heating system, there are cases when the pressure in the return line of the heating network is lower than required hydrostatic pressure for the heating system.

In this case, a pressure regulator RD is installed on the return line ( rice. 2.6), which should create the necessary backwater in the heating system with a margin of 5 m(from the condition of filling the heating system with water in static mode).

Estimated drop in front of the elevator ΔN EL must be determined taking into account the losses in the pressure regulator.

Rice. 2.6. Scheme of connecting the heating system to the heating network with RD

on the return line

The pressure regulator can prevent the discharge of water from the heating system through the return line when the heating network stops. To completely keep the water in the heating system, a check valve is installed at the supply.

7. Elevatorless systems.

In all considered schemes for connecting the heating system, there is a hydraulic and typical connection between the heating network and local heating systems. Therefore, all these systems are called "dependent".

The main disadvantage of dependent systems is precisely the hydraulic connection of the heating network with the heating device of subscriber units, which, as a rule, have reduced strength (mechanical), which limits the limits allowable pressures heating network: cast-iron radiators - R add = 60 m; steel radiators – R add = 100 m; convectors - R add = 160 m. Exceeding the specified pressures can lead to accidents.

This reduces the reliability and complicates the operation of heat supply systems, because. with long networks and in large numbers subscribers, pressure losses in the network fluctuate and vary widely. At the same time, the level of pressure in the network often exceeds the allowable for subscribers.

In cases where the difference between R auxiliary heater and R calculation in the heating network is small, even a slight increase in pressure in the return of the heating network can lead to a rupture of the heating devices in the heating system. Therefore, according to the conditions of reliable operation of heat supply systems, an independent connection scheme is preferable.

In the same cases, when the pressure in the heat network in static conditions exceeds R additional subscribers, the use of an independent connection scheme is mandatory.

8. Independent connection scheme.

Rice. 2.7. Independent scheme for connecting the heating system to

heating network: 1 - heating system feed line from

heating network return

With independent schemes, the heating system is connected to the heating network through a surface heater. The heating system in this case operates under the pressure of its own expansion vessel. If the heating system is designed to work with Δt = 105-70 ºС, then in order to avoid boiling water expansion tank must be raised above the heating system by 2.5-3 m.

With a heating system with inverted circulation, this can be omitted. To avoid scale formation in the water heater, it is recommended that the heating system be replenished from the return line of the heating network ( rice. 2.7), in which softened and deaerated water circulates.

During normal operation of the heating system, water leaks in it are insignificant, which makes it possible to fill the expansion tank no more than once a month. Filling the expansion tank is carried out by a jumper, performed for reliability with two taps.

The basis of this scheme: the presence of a heater in the scheme allows for a more rational control mode heating load. This is expedient if there is a zone of constant temperatures of network water at a positive outside air temperature in the central control schedule. This scheme allows the regulation of gaps by network water, because operation of the circulation pump allows not to interrupt the heating of the premises, continuing it at a gradually decreasing water temperature.

The disadvantages of the scheme include: a) the presence of additional expensive equipment: a heater, a circulation pump, an expansion tank, etc.; b) increase in the size of the heat point; c) additional costs for maintenance and repair of equipment; d) increased energy costs; e) an increase in the specific water consumption in the heating network and an increase in T2 by an average of 3-4 ºС.