What is a centralized heating system

The vast majority of apartment buildings in our country have centralized heating. Reform of housing and communal services, annually increasing tariffs make people think about the efficiency of heat use. To reduce operating costs, you need to know the design of the heat supply system.

How the centralized heating system works

District heating is a method of supplying heat from a single source to residential and industrial premises located over a large area.

The general scheme looks like this:

1. The coolant is heated at separately located objects to the required temperature.
2. Through pipes laid in the ground or in an open way, heat is supplied to the houses.
3. In heating units, energy consumption and heat distribution are organized along the entrances of the house.
4. Through the risers of the in-house wiring, hot coolant is supplied to each apartment and to the flights of stairs.
5. To heat apartments, heat exchangers are used, which are commonly called radiators or batteries.

The boiler room located in the house itself is a special case of central heating.

Each of the systems can be arranged in different ways and perform additional functions.

Heat sources

The coolant is heated in specially built for this purpose combined heat and power plants (CHP), state district power plants (GRES) or boiler houses serving several residential areas.

The names of TPP and GRES remain from Soviet times, although the owners are now private energy companies.

CHP, GRES and boiler houses differ:

• the main purpose and mode of operation;
• power;
• radius of the served area.

Based on the economic feasibility of CHP plants are being built in settlements with a population of 100 thousand people and developed industry. GRES are designed for small and medium-sized cities with low power consumption. Boiler houses heat residential and public buildings, industrial facilities within a radius of no more than 3 km.

Combined heat and power plants are designed in such a way that in the cold season their main purpose is to heat water for heating purposes. During the interfuel period, the station switches to the power generation mode.

State power plants are needed to generate electricity. Heat is released during the operation of the turbines and directed to heating purposes.

Boiler houses exclusively heat water for heating systems, they do not generate electricity.

Heat recovery scheme

The functional diagrams of the CHPP and GRES operation are very similar, the difference lies in the capacity and construction of equipment.

The receipt of electric and thermal energy at CHPPs and TPPs occurs due to the combustion of fuel. It requires coal, fuel oil or natural gas to work.

CHP device

The main units of the CHP are:

• fuel economy - a set of places for storing and preparing fuel;
• boiler room consisting of a boiler and auxiliary equipment;
• turbine and electrical equipment;
• condensate plant;
• heat exchangers that extract heat for district heating;
• technical water supply system.

Additional systems are smoke removal and smoke cleaning systems, ash and slag removal systems, pipelines.

Boiler houses are much simpler - they do not include turbines, condensate plants, and other auxiliary equipment.

Algorithm of work of heat sources

CHP and GRES are extremely complex structures, but the principle of operation for heating the coolant is not difficult to understand:

1. The prepared fuel is supplied to the boiler room. Coal must be ground, preferably to a dusty state. For combustion, air is pumped into the combustion chamber.
2. In the boiler room, the technical water in the boilers is brought to the state of steam, which is under high pressure.
3. Steam is supplied through pipelines to the turbine blades, which, while rotating, generate electrical energy.
4. After the turbine, the cooled steam enters the heat exchanger, where it gives off thermal energy to the water for the centralized heat supply system.
5. The cooled down vapor passes into the liquid phase, which the condensate unit cleans from vapors and impurities.
6. The purified water is supplied to the boiler room, where a new heating cycle begins.

In the summer use mode, when much less hot water is required, the CHP is switched to the mode of generating electricity. In this case, steam is cooled in cooling towers to the state of water, pumped to a height of up to 12 meters and sprayed by special installations. Excess steam is discharged into the atmosphere.

Water enters the pool, where it is cooled. Further, by condensing units, it is supplied to the boiler room. The process is repeated. To compensate for losses, water is added from external sources - rivers or lakes.

Coal-fired CHPPs and GRESs must be equipped with smoke cleaning systems.

Heat exchanger design

The task of heat exchangers is to take heat from the steam that has passed through the turbine.

Devices are classified by design:

• shell-and-tube;
• sectional (elemental);
• lamellar.

Each type has many designs.

The most common and effective is the shell-and-tube version of the device. Pressurized steam enters the tube bundle, which is located in a sealed casing. Chilled water is supplied inside the housing. The process of heat exchange takes place - tubes heated by steam heat the water inside the tank. The pumps create pressure for the movement of fluid in the piping of the central heating system.

Features of district boiler houses

Boiler houses, depending on the intermediate heat carrier, are divided into steam and water.

In the first case, the water is brought to the state of steam, in the second, water below 100 degrees participates in heat exchange. The option depends on the project, the distance to the objects, and other technical features of the construction.

Steam as a coolant for supplying apartments is used less often, it can only be found in old housing stock.

Indoor heating equipment

Distribution of heat in the premises of an apartment building is carried out according to one of the schemes:

• one-pipe with top filling;
• one-pipe with bottom filling;
• two-pipe with bottom filling;
• two-pipe with top filling.

In the first case, the coolant under pressure rises through the central riser to the upper floor. Further, by gravity, the water, having given up part of the heat to the batteries, returns to the heating unit and then is transported towards the CHP (boiler house).

Risers pass inside apartments and it is technically difficult, and sometimes impossible, to disconnect your home from the general system. The temperature of the radiators can be controlled by special thermostats, which require welding to be installed.In high-rise buildings, to supply the coolant to the last floor, additional pumps are installed in the heat supply units, which increases the costs and cost of the services provided.

Interference with the second scheme is also technically impossible - the pipes also run inside the apartments here.

Recently, in new houses and during the reconstruction of old buildings, two-pipe schemes have been performed with the location of common communications in the entrances or technological mines. In such cases, it becomes possible to disconnect a single apartment from the heat supply.

To unauthorizedly turn off the heating for any reason, Russian law strictly prohibits.

There is a restriction on the installation of radiators in apartment buildings. Pressure in a 5-storey building ranges from 2 to 4 atm, and in a 9-storey building up to 7 atm.

In the summer, after repair work on the communications, pressure testing is carried out - the pressure is raised to 10-12 atm in order to detect leaks. When filling the system with coolant, water hammer is possible.

Based on the possible loads, when replacing radiators, they refuse from all-aluminum products, choosing bimetallic radiators. Pay attention to the guaranteed pressure indicators that the battery can withstand.

Advantages and disadvantages of district heating

Any equipment, technical systems and communications have advantages and disadvantages. The pros and cons are considered in conjunction with the economic component and ease of use.

The positive qualities of centralized heating include:

• Operating costs under the central system are comparable to or lower than individual energy charges.
• Most of the CHPPs, GRES, district boiler houses operate on any type of fuel, which makes it possible to create emergency reserves for operation.
• There are only radiators from the heating equipment in the living quarters. Boiler plants are removed from residential areas, sanitary zones have been installed around them, which improves the environment.
• The owner does not purchase expensive equipment (boilers).
• Heating the apartment does not depend on the supply of energy and electricity to the house.
• Reduces the likelihood of accidents and disasters associated with gas leaks.
• There is no need to conclude contracts and pay for maintenance of gas equipment.
• Accidents are eliminated by the supplying organization in the shortest possible time at their own expense.

The disadvantages include:

• losses in networks that deliver heat to the house - the length of the pipeline can be 10 km;
• the supplying organization includes possible costs in the tariffs, so the payment is significantly higher than it could be;
• limited temperature control in the apartment, caused by the schemes for building intra-house networks;
• the impossibility of disconnecting a separate apartment from the common house network without a court decision;
• dependence on tariffs (set by regional commissions), which the homeowner is not able to influence.

The most important disadvantage in ease of use is considered to be the inability to heat the house during the inter-furnace period. In spring and autumn, there are often sharp temperature drops to which the CHPP cannot respond quickly. Changing operating modes entails large financial losses.

How homes are heated in other countries

Our country inherited central heating as a legacy of the socialist economy. In a planned economy and with large energy resources, centralized heating was built and for the most part paid for by the state.

Pipes with a coolant cooled down in houses on the way to the CHPP were a source of heat for greenhouses, industrial enterprises, and cattle breeding complexes.

Mass production of equipment for individual heating systematically began in the mid-90s, before that there was a shortage even for private households.

There are very few countries on the planet with similar climatic conditions and comparable population density. To save resources in most of the world, heating is decentralized.

In Germany, France, Canada, systems similar to ours were built until the 50s of the last century. The ensuing global energy crisis triggered the development of heating systems that serve one or more multi-storey buildings. For this, a separate boiler room is being built. There are no long communications for the transportation of hot water - losses are minimized.

It is easy to start up the units in case of a sudden cold snap, and on warm days, reduce energy consumption by reducing the temperature of the circulating water.

There is no centralized heating in France and Great Britain - there, each apartment has a separate boiler with a closed combustion chamber, the operation of which is controlled by the owner of the apartment.

The availability and availability of energy resources in the region plays an important role.

In Poland and China, many homes are heated with coal, in Iceland - with water from thermal springs. In Norway, cheap electricity is actively used.

Ways to reduce costs

There are few opportunities to reduce supplier operating costs and heating costs for apartment owners:

• high-quality thermal insulation of main pipelines, especially those located on the surface;
• installation of general household energy metering devices that compare the temperature of the coolant at the inlet and outlet - knowing the volume of the flowing liquid, the equipment automatically calculates the consumed calories;
• installation of individual metering devices in each apartment, which is applicable only for schemes 3 and 4 discussed above.

There are no other options to influence payment.

Is it worth giving up district heating

The legislation does not establish restrictions on changing the scheme, but there are no clear instructions on which it is possible to refuse heating in an apartment building.

The supplying organizations are directly interested in a larger number of customers, therefore, they agree on changes to the heating scheme only by a court decision.

The norm that gasification can only be carried out in houses with a height of up to 11 floors was canceled quite recently.

The court will need to collect documents, some of which are very difficult to obtain, and sometimes impossible:

• certificate of ownership - redevelopment of non-privatized apartments is excluded;
• the consent of the residents of the entire entrance - you can not get it only if the pipelines are not the property of the whole house;
• refurbishment project;
• gas service permit;
• approval of the project in the Ministry of Emergency Situations or another organization responsible for the fire safety of the facility;
• hydraulic engineering calculation of a specialized organization on the possibility of re-equipping the system and maintaining the characteristics after excluding a particular apartment from the general circuit.

You cannot completely refuse to pay. The receipt will contain the amount for the heat given off by risers and planks of pipelines, you will have to pay fees for heating the entrance.

Central heating, not always economical, but reliable and widely used, under certain conditions and additional costs can be replaced with an individual one.Before starting the arrangement of personal heating, it is worth weighing all the pros and cons, calculating the costs and possible savings, and then making the final decision on the refurbishment.