Open heating system: schematic diagrams and features of the arrangement

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Oksana Chubukina
Last update: March 2019

Due to its ease of installation, low cost and sufficient efficiency, an open heating system continues to be in demand. Having dealt with the principle of operation, equipment and installation rules, you can organize the heat supply of the house yourself.

We will tell you how to create a workable open-type heating circuit. We will show you how to build a system, strictly following the technological requirements and standards when choosing and connecting elements. Based on our recommendations, you will build a fail-safe effective circuit.

For independent craftsmen, we suggest that you familiarize yourself with proven assembly options. The information presented for consideration is supplemented by useful schemes, photo collections, video instructions.

Complete set and principle of system operation

AT water heating system Liquid acts as an intermediary in the transfer of thermal energy from a boiler plant to radiators. Coolant circulation can be carried out over long distances, providing heating of houses and premises of different sizes. This explains the widespread introduction of water heat supply.

The operation of an open heating system is possible without using a pump. Fluid circulation is based on the principles of thermodynamics. The movement of water through the pipes occurs due to the difference in the density of hot and cold liquids, as well as due to the slope of the laid pipes.

An indispensable element of the system is an open expansion tank, into which excess of preheated coolant enters. Thanks to the reservoir, the fluid automatically stabilizes. Capacity is installed over all components of the system.

The whole process of functioning of "open heat supply" is conditionally divided into two stages:

  1. Innings. The heated coolant moves from the boiler to the radiators.
  2. Return. Excess warm water enters the expansion tank, cools down and returns to the boiler.

In single-pipe systems, the supply and return functions are performed by one line; in two-pipe systems, the supply and return pipes are independent of each other.

Open heating system
The density of warm water is lower than the density of cold water; therefore, a hydrostatic head is formed in the system. Under pressure, hot water advances to the radiators

The simplest and most affordable for self-installation is considered single pipe system. The design of the system is elementary.

The basic equipment for a single pipe heat supply includes:

  • boiler;
  • radiators;
  • expansion tank;
  • pipes.

Some refuse to install radiators and place a pipe with a diameter of 8-10 cm around the perimeter of the house. However, experts note that the efficiency of the system and ease of use with this solution are reduced.

Heating system complete set
The open-type gravitational one-pipe system diagram is non-volatile. The cost of purchasing pipes, fittings and equipment is relatively low. It is possible to work with different types of boilers

More complicated in the device and more expensive in execution two-pipe heating option. However, the costs and complexity of the structure are fully offset by the elimination of standard flaws in single pipe systems.

A coolant with an equal temperature is supplied almost simultaneously to all devices, the cooled water is collected by the return line, and does not flow into the next battery.

Two-pipe open heating system
For servicing each appliance in the two-pipe heating circuit, a supply and return line are arranged, due to which the temperature of the system delivers a coolant of equal temperature to all points, and the cooled water is collected and directed to the boiler by a return line, independent of the supply line

Installation and Maintenance Requirements

When installing a heat supply system at home, it is important to consider a number of features of an open heating system:

  1. To ensure normal circulation, the boiler is installed at the lowest point of the line, and the expansion tank at the highest point.
  2. The best place to place the expansion tank is the attic. In the cold season, the tank and the supply riser within the unheated attic must be insulated.
  3. The laying of the highway is carried out with a minimum number of turns, connecting and fittings.
  4. In a gravitational heating system, water circulates slowly (0.1-0.3 m / s), therefore, heating should occur gradually. Boiling must not be allowed - this accelerates the wear of radiators and pipes.
  5. If the heating system is not used in winter, then the liquid must be drained - this measure will preserve the pipes, radiators and boiler.
  6. The coolant level in the expansion tank must be monitored and periodically replenished. Otherwise, air congestion may occur in the line, which reduces the efficiency of the radiators.
  7. Water is the best heat carrier. Antifreeze is toxic, it is not recommended for use in systems that have free contact with the atmosphere. Its use is advisable if it is not possible to drain the coolant in an unheated period.

Particular attention is paid to the calculation of the cross section and the slope of the pipeline. Design standards are regulated by SNiP under the number 2.04.01-85.

In circuits with gravitational motion of the coolant, the size of the pipe section is larger than in pumping schemes, but the total length of the pipeline is almost two times less. The slope of the horizontal sections of the system, equal to 2 - 3 mm per linear meter, is arranged only during the installation of heat supply with the natural movement of the coolant.

Diagram of an open gravity-type heating system
Failure to comply with the slope when installing systems with a natural movement of the coolant leads to airing of the pipes and insufficient heating of the radiators remote from the boiler. As a result, heat efficiency decreases

Types of open heat supply schemes

In an open heating system circuit, the movement of the coolant is carried out in two different ways. The first option is natural or gravitational circulation, the second is forced or artificial stimulation from the pump.

The choice of scheme depends on the number of storeys and the area of ​​construction, as well as on the expected thermal regime.

Natural circulation in heating

AT gravity system there is no mechanism to ensure the movement of the coolant. The process is carried out exclusively by expanding hot water. For the operation of the circuit, an overrun riser is provided, the height of which is at least 3.5 m.

Natural circulation
If you neglect the installation of a vertical transit riser, then it is highly likely that the coolant coming from the boiler will not develop a sufficient speed

The natural circulation type heat supply system is optimally suited for buildings up to 60 square meters. m. The maximum length of the circuit that can provide heat is considered to be a 30 m highway. An important factor is the height of the building and the number of storeys of the house that allows you to mount an accelerating riser.

The natural circulation pattern is not suitable for low temperature applications. Insufficient expansion of the coolant will not create the proper pressure in the system.

Features of gravity scheme:

  1. Connection to heated floors. A circulation pump is mounted on the water circuit leading to the floor. The rest of the system is operating normally.When a power outage occurs, the house will continue to heat.
  2. Work with a boiler. The heater is mounted at the top of the system, slightly below the expansion tank.

To ensure trouble-free operation, a pump can be installed on the boiler. Then the scheme of heat supply and production of hot water automatically goes into the category of forced options. Additionally, a non-return valve is installed to prevent recirculation of the coolant.

Forced system with pump

In order to increase the speed of the coolant and reduce the time to heat the room, a pump is built in. The movement of the water flow increases to 0.3-0.7 m / s. The heat transfer rate increases, and the branches of the trunk warm evenly.

Circulation pump in the system
Pumping circuits are constructed both open and closed. In open circuits, the expansion tank is installed at the highest point in the system. The presence of the pump allows you to increase the pipeline between the boiler and the batteries, both in height and in length

Organization Highlights forced system:

  1. The circuit with the integrated pump is volatile. So that the heating of the room does not stop when the power is turned off, the pumping equipment is placed on the bypass.
  2. The pump is installed before entering the boiler on the return pipe. The distance to the boiler is 1.5 m.
  3. When installing the pump, the direction of water movement is taken into account.

Two shut-off cranes and a bypass elbow with a circulation pump are mounted on the return. If there is current in the network, the taps are closed - the coolant moves through the pump. If there is no voltage, then the valves must be opened - the system will be converted to natural circulation.

Pump installation
A check valve must be installed on the supply pipe. The element is placed immediately after the boiler and prevents the recirculation of the coolant during pump operation.

Piping options in the system

From the layout heating appliances and connecting pipes depends on the efficiency, economy and aesthetics of the heat supply system. The choice of wiring is determined based on the design features and area of ​​the house.

The specifics of single pipe and double pipe schemes

Heated water enters the radiators and back into the boiler in various ways. In a single-circuit system, the coolant is supplied through one large-diameter trunk. The pipeline passes through all radiators.

Advantages of the single-tube system with self-circulation:

  • minimum consumption of materials;
  • ease of installation;
  • limited number of pipes inside the living room.

The main disadvantage of a single-pipe scheme that fulfills the supply and return duties is the uneven heating of the heating radiators. The intensity of heating and heat transfer of the batteries decreases as they are removed from the boiler.

Single pipe design
With a long wiring chain and a large number of radiators, the last battery can be completely ineffective. "Hot" heating appliances are recommended to be installed in the rooms of the north side, nurseries and bedrooms

The two-pipe heating circuit is confidently gaining ground. Radiators connect the return and supply piping. Local rings form between the batteries and the heat source.

The main advantages of the system:

  • all heaters are evenly heated;
  • the ability to adjust the heating of each radiator separately;
  • reliability of operation of the circuit.

The dual-circuit system requires large investments and labor. Installing two branches of communications on building structures will be more difficult.

Dual circuit
The two-pipe system is easily balanced, providing a coolant of the same temperature to all heating devices. Room rooms warm evenly

Upper and lower flow of coolant

Depending on the location of the main supplying the hot coolant, distinguish the upper and lower eyeliner.

Diagram of an open two-pipe heating system
In open top heating systems, there is no need to use air exhaust devices. Its excess is discharged through the surface of the expansion tank in communication with the atmosphere.

At the upper distribution, warm water rises along the main riser and is transferred to radiators through distribution pipelines. The installation of such a heating system is advisable in one- and two-story cottages and private houses.

Quite practical heat supply system with a lower wiring. The feed pipe is located below, next to the return. The movement of the coolant in the direction from bottom to top. Water, passing through radiators, is sent through a return pipe to a heating boiler. Batteries are equipped Mayevsky cranes to remove air from the line.

Open heating system with bottom wiring
In heating systems with lower wiring, there is a need to use devices for air exhaust, the simplest of which is a Mayevsky tap

Vertical and horizontal risers

The type of position of the main risers distinguish between vertical and horizontal piping wiring methods. In the first version, radiators of all floors are connected to vertically located risers.

Vertical wiring of the heating system
Vertical wiring is used when arranging houses on two, three or more floors with an attic, within which you can lay and insulate the pipeline

Features of "vertical" systems:

  • lack of air jams;
  • suitable for heating high-rise buildings;
  • floor connection to the riser;
  • the difficulty of installing apartment heat meters in multi-storey buildings.

Horizontal wiring involves connecting radiators of one floor to a single riser. The advantage of the scheme is that less pipes are used for the device, the installation cost is lower.

Horizontal cabling of an open heating system
Horizontal risers, as a rule, are used in one- and two-story rooms. The arrangement of the system is relevant in panel-frame houses and residential buildings without piers

Arrangement of gravity type of heating

It is better to entrust the development of the draft gravity system to heat engineering specialists. The document indicates the type of heating, the method of connecting radiators and coolant circulation, the recommended equipment parameters, the number of radiators and the length of the pipeline.

Calculation of the heat supply system

It is necessary to determine the hydraulic characteristics of the system, which in the future will help to choose the optimal diameter of the pipeline.

System calculation
In a natural heating system, it is recommended to install the boiler in a basement or basement. This allows you to increase the length of the transit riser.

To calculate the value of the circulation head (RC) you must have the following data:

  1. The distance from the center of the heating boiler to the center of the radiator (h) The greater the distance between these devices, the more stable the circulation.
  2. Cooled Pressure (Ro) and heated (Pr) water.

The circulation pressure depends only on the temperature difference of the coolant. Exact indicators can be found in the tabular data.

Circulation pressure
The greater the temperature difference of the coolant, the higher the pressure in the line. Therefore, it is important to take care of the "incoming" temperature of the liquid.

To width pipeline sections the type of material influences. The diameter of the steel pipe must be at least 50 mm. After branching, the cross section of the highway narrows by one size. The return, on the contrary, is compiled with the subsequent expansion.

Particular attention is paid to the volume of the expansion tank. The tank should not be less than 5% of the total coolant volume in the system. Failure to comply will result in draining water from the system or rupture of pipes.

Selection of basic components

For an open system, it is better to choose a boiler that runs on solid fuel or fuel oil. Installation of electric boilers and gas equipment is prohibited.Sometimes traffic jams form in the trunk - this can lead to an emergency.

The power of the heater is determined based on the calculation - 1 kW of heat energy per 10 square meters of the house. Depending on the quality of the insulation of the room, 10-30% is added to the obtained value.

Boiler in the heating system
The boiler is located in a separate room equipped with forced air circulation. The equipment is installed on fireproof material or concrete floor

The expansion tank for the gravity-type heating system must be made of steel. Polymer materials are extremely undesirable. For heating a small one-story house, a 8-15 liter tank is suitable.

To equip the pipeline using pipes from the following materials:

  1. Steel. They are characterized by high thermal conductivity and resistance to high pressure. The disadvantage is the complexity of installation and the need to use welding equipment.
  2. Polypropylene. The main advantages: resistance to temperature fluctuations, strength, tightness and ease of installation. Service life is 25 years.
  3. Metal-plastic. Material does not give in to corrosion, prevents contamination of a contour. Disadvantages of the highway: limited life (up to 15 years) and high cost.
  4. Copper. Pipes with maximum heat dissipation and resistance to high temperatures - up to + 500 ° C. The main disadvantage is the high cost of the material.

In the open heating circuit radiators are installedmade of high strength metals.

The most common are steel models. They have an optimal ratio of the main parameters: appearance, price and thermal power.

Steel radiator
Steel radiators due to thin walls, light weight and high degree of heat transfer are compared with convectors. The equipment quickly warms up the room, due to the accelerated air movement

Steps for installing an open system

The whole process of organizing a gravitational heating system can be divided into several stages:

  1. Boiler installation. The equipment is fixed on the floor surface or suspended on the wall. The choice of method depends on the size of the boiler.
  2. Piping according to the selected scheme and developed project. It is important to comply with the recommended slope angle of the pipe circuit.
  3. Installation of radiators heating and connecting them to the system.
  4. Installation of the expansion tank and its insulation.
  5. Connection of all elements, checking the tightness of joints and starting the system.

After the boiler, on the supply pipe, it is desirable to install a temperature sensor to monitor the efficiency of the heating system.

Solid fuel boiler
Installation of the heating system must be carried out in the warm season. Arrangement of the highway and commissioning will take about one week

Features of the forced circuit assembly

In order for the compulsory system to justify itself and function correctly, it is necessary to choose the right circulation pump and competently "embed" it in the heat supply line.

Circulation pump selection

The main parameters for the selection of pumping equipment: device power and pressure.These characteristics are determined based on the area of ​​the heated room.

Indicative indicators:

  • for houses of 250 sq.m, a pump with a capacity of 3.5 cubic meters / h and a pressure of 0.4 atm is suitable;
  • in rooms with a size of 250-350 sq.m, a device is installed at 4.5 cubic meters / h with a pressure of 0.6 atm .;
  • if the area of ​​the house is 350-800 sq.m, it is advisable to purchase a pump with a capacity of 11 cubic meters / h, the pressure of which is at least 0.8 atm.

With a more meticulous selection, experts take into account the length of the heating system, the type and number of radiators, the material of manufacture and the diameter of the pipes, as well as the type of boiler.

Installing the pump in the line

The pump is placed on the return so that not too hot coolant passes through the device. Installation of modern models from materials resistant to high temperatures is possible on the supply line.

When “tapping” the pump, the water circulation must not be disturbed. It is important that at any point in the line when the pump unit is in operation, the hydrostatic pressure remains excessive.

Pump installation diagrams
Four permissible circuits for heating systems with pump circulation and an open expansion tank. Hydrostatic pressure is maintained at the desired level.

Option 1. Raise the expansion tank. A simple way to convert a natural circulation system to a forced one. To implement the project, you need a high attic space.

Option 2 Moving the tank to the far riser. The time-consuming process of reconstruction of the old system, but for the installation of a new one, is not justified. Simpler and more successful ways are possible.

Option 3 Expansion tank pipe near the pump nozzle. To change the type of circulation, it is necessary to cut off the tank from the supply line, and then connect it to the return - behind the circulation pump.

Option 4 The pump is included in the supply line. The easiest way to reconstruct a system. The disadvantage of the method is the adverse operating conditions of the pump. Not every appliance can withstand high temperatures.

Conclusions and useful video on the topic

Video # 1. Recommendations for assembling a heating system with natural circulation:

Video # 2. Installation procedure of the circulation pump:

Important aspects of arranging an effective heating system are choosing a workable circuit, calculating the parameters of the mains, selecting components and following the installation technology. Self-installation is possible with plumbing skills, and it is better to entrust the development of a detailed project to professionals.

Want to ask a question about the organization scheme and the layout of the open water circuit? Please leave comments in the block below. Here you have the opportunity to ask a question or report an interesting fact on the topic.

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Visitors Comments
  1. Ilya Mechnikov

    An open heating system is quite widespread in villages and suburbs, because it is easy to operate and very cheap to install. But when you start using it, you understand that you need to know how it actually works, what are the driving forces of the heating process.If you are going to install such a system, do not be lazy and read about the principle of its action, features, pros and cons of heating of this type. But do not forget to consult a specialist.

    • Alexei

      Ilya, there is nothing good in such a heating system, it is a relic of the past, now rarely is anyone doing it. It is uneconomical even in fuel consumption. Judge for yourself how much water walks in all these thick pipe diameters, radiators (they only fit cast iron there).
      Its only advantage is that it is electrically independent, that is, there is no light, but you have heat, there is no pump in the system.
      But viduha, to put it mildly, depressing - pipes around the house, this terrible slope, a bulky expansion tank, constantly gurgling ... No, I wouldn’t like this for sure.

      • Alexei

        I have an open system on a two-story house. Bimetal radiators. The wiring pipe is copper 18 and 22, the slope is 5 mm per meter, it is not noticeable on the eye. Accelerating riser - 50 mm, structurally hidden. Expansion tank - 8 liters. Nothing gurgles 🙂

  2. Alexander

    Hello, there is such a problem, in the pipe heating system (without radiators) there is a reduced pressure. This becomes clear when you try to bleed air through a pump and Mayevsky taps, and vice versa, air is drawn into the system. Such a question - why can the pressure in an open heating system decrease?