House heating schemes - one-pipe and two-pipe heating system

How the natural circulation heating system works

The main task of the water heating system - this is to make the coolant circulate through the pipes. In order for the house to warm up, hot water from the boiler must flow into pipes and radiators. The natural circulation heating system works on the principle of gravity. The liquid moves through the pipes in a gravity way without using a pump. The density and weight of the liquid becomes less when heated, and after cooling it returns to its original state.

In such a device, there is virtually no pressure. According to calculations, it can be seen that with a pressure of a 10-meter water column, there is a pressure of 1 atmosphere. Turns out that in the heating device of a one-story house the pressure will be from 0.5 to 0.7 atm., and in a two-story house - no more than 1 atm.

Advantages and disadvantages of natural circulation heating

As with any device, water heating with natural circulation has its advantages, but also disadvantages. Why is the system good?

Simple installation and maintenance, easy system start-up. All installation can be done by yourself.
No need to buy expensive equipment.
The system works stably. The heat carrier gives the greatest heat output and maintains the required temperature in the room.
No dependence on electricity. The device will continue to work if the power is cut off.
If the house is well insulated, then with such a system you can save a lot.
No pump that makes a lot of noise.
If maintenance is carried out on time, the heating device can work for over 35 years.

Cons of the system:

Despite the fact that the heating system requires few materials, the costs will become much higher when the local resistance of the pipeline decreases. Because you will have to install larger pipes.
The house warms up much more slowly.
If pipes pass through unheated rooms, then these areas should be insulated. Otherwise, there is a risk that the liquid will freeze.
Such a heating system is only suitable for private houses with an area of no more than 100 sq. m., since it operates within a radius of up to 30 meters. This is due to the fact that the system has a small circular head.
The main condition is an attic in the house. It is there that the expansion tank is installed.

Scheme of a two-pipe heating system of a one-story house

If you choose a one-pipe system, it is worth considering the possibility of disconnecting each battery (for repairs, adjusting the temperature in the room)

This is relatively rarely used due to its low efficiency. It is one highway along the walls, passing under all radiators. From each of them, branch pipes are mounted into it, through which the coolant is supplied and removed. Since the hotter coolant enters the first radiators, giving them part of the heat, the water is already cooled down to the latter. As a result, the house will be heated unevenly, and the rooms farther from the boiler will heat up much longer. Best of all, such a scheme is suitable for a one-story house with a small area, as it will reduce installation costs. There is another version of the one-pipe scheme: when the radiator cuts into the pipe. The disadvantage of this method is the inability to shut off one of the radiators so as not to stop the entire system.

Choosing a two-pipe system, you can connect radiators in any way: diagonal, side, bottom connection

Types of natural circulation systems

Before creating a circuit for heating a private house, first calculate the amount of heat required for the premises. The calculation includes data on the boiler, placement and diameter of pipes, as well as the level of thermal insulation of the outer walls. Even the smallest errors in calculations can affect the quality of home heating. Therefore, it is better if all the calculations are carried out by specialists. Heating systems are of several types:

Open and closed type (differ by expansion tanks).
One-pipe and two-pipe type (heating radiators are connected in different ways).

Open system

The open device includes a reservoir (open tank), which is equipped with a pipe (emergency overflow). The pipe is connected to the sewer system or taken out into the street. The tank is installed under the ceiling, sometimes in the attic. An open-type tank can be made of any size with your own hands, which is its main advantage. Has an affordable price... Disadvantages of the device:

You constantly need to add water to an open-type tank, as it evaporates quickly. In order not to constantly add water manually, a water pipe can be brought to the tank.
Often, corrosion forms on the metal elements of the circuit. Due to the fact that oxygen is constantly flowing into the open tank.
Air enters the pipeline. By fixing the radiators at a slight slope, and installing automatic air vents, you can get rid of the problem.

Closed system

Natural circulation system a closed-type coolant is well suited for both one-story and two-story houses. A membrane tank is installed in the heating circuit. Thanks to the tank, the metal parts of the device are less susceptible to corrosion. A closed device works as follows:

The closed flexible diaphragm tank is a diaphragm expansion tank. The membrane creates two sections in the tank. The first section is for the coolant, the other contains air or nitrogen. During the expansion of the coolant, excess water from the heating circuit goes into the tank.
The membrane begins to stretch due to hot water, and the gas in the second part contracts.
When the water cools down, the gas increases again and pushes the coolant back into the system. Thus, there is a continuous filling of the water circuit with the coolant.

If you choose between an open system and a closed one, it is cheaper to purchase or create an open tank with your own hands. Diaphragm tank costs several times more, so it is rarely used.

One pipe system

For single-storey houses with a small area, one-pipe heating is suitable. In a two-story house, this type of heating will be ineffective. The advantages of the system are cheap installation, simple design, pipes are not installed under the ceiling, which means that the overall interior of the room will not deteriorate. One-pipe type of heating works according to the following principle:

The liquid rises along the vertical section of the pipe.
Then the coolant moves into a horizontal pipe. This pipe connects the heating radiators.
The cooled liquid returns back to the boiler from the outer radiator.

This system has its drawbacks. The further the supply riser, the lower the temperature of the radiators. Bypasses will help increase productivity. To establish uniform heating of the house, jumpers are placed in the places where radiators are connected. Even after making accurate calculations, a one-pipe type of system will be ineffective if a one-story house has more than three rooms. The problem can be solved by upgrading the system with a circular pump.

Scheme of two-pipe water heating for a private house with natural circulation

The two-pipe heating type is suitable for heating a two-story house. If we compare a one-pipe and two-pipe system, then in the second - the liquid is supplied to all radiators hot.The two-pipe circuit has a special design consisting of two pipes. One for supply, the other for return. A supply pipe is connected to each heating device. Connection is made through a separate input tap. And the return pipe is connected separately. The advantages of a heating system with upper and lower wiring are that its installation is very simple, and the operating characteristics are effective. With a system like this:

It is possible not to add additional sections to the radiator in order to improve heating.
Unlike a single-pipe circuit, pipes of a smaller diameter are used to lay the pipeline in this system.
Easy system adjustment.
The heat is evenly distributed.

Currently, it is possible to create with your own hands a two-pipe type of heating with natural circulation... For its manufacture, steel or polymer pipes are used..

Scheme for calculating a heating system with natural circulation

The most difficult thing in designing a heating system is the correct calculation. How well a device will perform depends on the length and angle of the pipes, as well as the number of turns on it. You need to know this because there is no pressure in the circuit. What you need to consider when drawing up a diagram and calculation:

What is the diameter of the pipes and the material from which they are made.
Angle of inclination of pipes.
Types of coolants.
Coolant supply methods.

Benefits of forced circulation ↑

The difference between the scheme with forced circulation is the installation into the pump system

The efficiency of the system with forced circulation of the coolant is achieved due to the ability to control and set the required heating level in each room and for each radiator. From the point of view of the owner, this nuance sometimes acts as a decisive factor when choosing the type of system. Referring to other advantages of a forced circulation heating system for a one-story house, it is worth noting:

It is allowed to use pipes of any diameter, whereas in a system with natural circulation, they must be of a large diameter and located at a slope.
The line can be placed in any plane (horizontally, vertically), pipes can be laid into the floor, placed at a minimum-low level, and a warm floor system can be installed. Due to the injection of the coolant, water in any case will go to the radiators.
Due to the use of small diameter pipes, the system does not require feeding with a large amount of water.
For a system with forced circulation, there is no need to install pipes with a slope and place the tank at the highest point
Possibility of installing an automated heating source (boiler), which will independently heat the coolant according to the set parameters.
Possibility to connect remote temperature control devices (room regulator).

Analyzing the shortcomings of the forced circulation scheme, it is worth noting the main ones. First of all, in the absence of electricity, there will be no heating in the house. It is not recommended to use such a system if the area has power outages. Experts note another drawback - the creation of noise during the operation of the circulation pump. But it can be solved. For example, by installing a boiler and a pump in a non-residential building, boiler room, basement.

Choosing modern options for boilers, you should know that almost all of them are equipped with a built-in pump. It works, of course, not silently, but not so loudly as to be considered a problem. For example, an extractor hood in the kitchen makes much more noise.

What is the best pipe material?

The method of installing the circuit, protection against corrosion and hydraulic resistance, all these indicators will depend on the material from which the pipeline is made. For the heating system, you can use polypropylene, steel, metal-plastic and copper pipes.

Polypropylene material. Polypropylene pipes withstand high temperatures well, have a long service life (over 25 years), and are smooth inside. Installation requires special tools and is expensive.
Steel. Despite the fact that such pipes are quite durable and have an affordable price, they are prone to corrosion and overgrowth. In addition, the installation requires welding or multiple fittings.
Metal-plastic. Lightweight pipes have a perfectly smooth inner surface. As a result, they are free of corrosion and deposits. But after installation, you will have to constantly pull the threaded fittings, which is a big drawback. Their service life is about 15 years, and for pipes this is very short. They have a high cost.
Copper pipes. Copper pipes have a beautiful appearance and a service life of over 100 years. Soldering is used for installation, very expensive in cost.

To determine what pipe diameter suitable for warming up your home, you need to know that:

The diameter of the pipe is selected according to the material from which the pipes are made and from the heat engineering calculations made.
Calculate the amount of heat required for the room and add 20% to the result.
Using the values indicated in the SNiP tables, the cross-section of the pipeline is calculated. For the calculation, take the readings of the heat capacity and the size of the pipe (internal section).

If, after each branching, install the supply pipe 1 size smaller than the previous one, then the circulation of the heat exchanger will become several times more intense. The return pipe is mounted with an extension. This calculates the minimum diameter of two pipes. Adhering to the obtained values, for each pipe section, its own size is established.

Coolant supply methods

The heating medium can circulate from the boiler to the heating device in two ways. Through the bottom or top filling.

Bottom filling. This filling method is only used for one-pipe systems. The pipeline is laid at floor level, while vertical pipes can be omitted. Bottom filling is ineffective without a circular pump.
Top filling. They are used for both one-pipe and two-pipe systems. Due to the fact that the distribution pipe is installed under the ceiling, the hot coolant is actively supplied to each radiator. Further, cooling down, the water goes into a return pipe mounted along the floor.

Circuit wiring diagrams

Heating scheme of a private house with a gas boiler

According to the method of connecting heating radiators, it is customary to distinguish two schemes for installing circuits of heating systems: one-pipe and two-pipe.

For a do-it-yourself one-pipe mounting assembly, a sequential arrangement of heating devices on the supply circuit is characteristic. Having passed from the top point through all the radiators (red line), the water returns along the return line (blue line) to the boiler.

One-pipe diagram of a gravity heating system

In a two-pipe system, two separate circulation circuits are installed. A hot coolant flows through one, supplying heat to the radiators, along the other circuit - the cooled water is sent from the radiators to the boiler.

The figure below shows a two-pipe heating system for a two-story house. The distribution of the coolant (red line) through the radiators starts from the maximum height H, which provides the required circulating head. The cooled coolant (blue line) is collected in the return line and sent to the boiler inlet.

Two-pipe diagram of a gravity heating system