Heating system with natural circulation

05-02-2018

Useful

Despite the fact that advanced technologies for space heating are now common, the heating system with natural circulation is in high demand. This is primarily due to the fact that it is easy to install, and if you also take into account the instability of providing the private sector with electricity, then the popularity of such an autonomous heating system becomes clear.

How it works

Immediately it should be said that thanks to a special device, the system works without forced circulation of the coolant. The movement of water in the pipes occurs due to the fact that when cooled, the density of water increases, and it flows down to the boiler through pipes installed on an incline, pushing out heated water from it.

Although a natural circulation heating system can work without a pump, it is still better to install it. When the pump is turned on, the coolant flows faster through the pipes, therefore, the room warms up faster.

When leaving the boiler, the water enters the accelerating collector, reaches through it to the top point, and through pipes installed at an incline from the boiler, while cooling, continues its way in a circle.

Disadvantages and advantages

First, let's talk about the shortcomings. Such an approach will help determine whether such a heating system will suit you.

If there is no pump in the system, then you need to wait for a rather long time until the hot water reaches the batteries and passes over them.
Uneven heating of radiators. This is due to the same nuance - hot water from above, and cold from below.
Installation выполняется более дорогими трубами большого диаметра.
It is necessary to install an open expansion tank, as a result of which the water evaporates and periodically needs to be added to the system. Installing a closed-type expansion tank can degrade system performance.
The design of the room suffers.
Do not violate the slope of pipes, even if you need to bypass the door.
The system should be as small as possible turns.
When planning a heating system without a pump, it is necessary to correctly determine the level of the batteries, the expansion tank and the boiler, which should be installed at the lowest point.

Benefits

Electrodependence Even if a pump is installed, when there is a power outage (or when the pump fails), the heating system continues to operate.
Installation и дальнейшее обслуживание не требует особых навыков.
Silent work.

Types of systems

As already mentioned, in the gravity heating system there should not be differences in height, otherwise it simply will not work. For this reason several contours can be made.

Single circuit

Everything is clear here - one pipe goes from the boiler, and the other goes to it, and batteries are connected between them. The presented scheme will help to figure it out.

A single-circuit system can be one-tube, only in this case it is necessary to take into account the factor that each successive battery in a gravity system will be more sensitively cooler than the previous one.

Double circuit

Dual-circuit systems may differ in the direction of movement of the coolant:

With oncoming traffic.
With passing traffic.

The choice of the method of pipe installation, taking into account the direction of the coolant movement, mainly depends on where the doors are located in the room or there are other nuances due to which the installation of the return in this place is impossible.

Regardless of the system chosen, the pitch angle of the pipes does not change.

How to calculate the power of the battery and boiler heating

It is not necessary to speak about exact results, since each house is individual and can differ in many parameters, which are impossible to take into account in the general scheme, and there is no need for that. Under ideal conditions, it is considered that for heating 1 m² enough 60 watts of radiator power. It is quite clear that if the house is not insulated, simple wooden windows are installed in it, then it will be necessary to install more powerful batteries.

In order not to engage in rework later, it is important even at the planning stage to find out what the capacity of the battery (or batteries) to be installed in a particular room should be. To do this, you can use one of two methods.

By volume

More accurate data can be obtained, given the volume of the room. We take measurements and, having received data on the height, width and length of the room, multiply them together, and multiply the result by 40 watts. Given the peculiarities of the structure, we introduce a correction factor. For:

a single-storey private house with a non-insulated attic - 1.5;
rooms with insulated walls - 1.1;
rooms with non-insulated walls - 1.3;

It is important to consider the number of doors and windows.

If there is an entrance door in the room, then another 150–200 W must be added to the resulting figure.
If the windows are small and energy-intensive, then for each you will need another 70 watts.
For large or non-insulated windows, you need to add 100 watts each.

By area

Calculating the number of batteries by area of the room, the average figure is 1 kW per 10 m². By the same principle, the power of the heating boiler purchased for the house is calculated.

Consider an example of how to make calculations.

There is a house with internal dimensions of 9? 8 m. We multiply the width by the length and get the area - 72 m².
72 m²divided into 10 (1 kW per 10 m²), and we get 7.2 - this is the boiler power in kW.
Now we find out the power of the battery for placing 2? 4 m.
The area turned out 8 m².
Using the same calculations as for the boiler, we get the figure 0.8 - the battery power in kW.

Now we will make amendments on climatic zones. Consider the coefficients:

In the southern regions - 0.8–0.9.
For the Far North - 1.5–2.
In the zone of the Middle Band - 1.2–1.4.

In our example, a 7.2 kW boiler was required. Taking into account the coefficient, we will calculate the final data for the Middle Band:

7,2?1,4=10,08.
Considering that the boiler must have a power reserve, we acquire a heating device with a capacity of 12–15 kW.
In the same way, we approach the calculations of the battery capacity for the room used in the example: 0.8? 1.4 = 1.12 kW. Round up and get 1.2 kW.

The power of the battery is indicated in the passport of the product. If you are not sure of the correctness of your calculations, then purchase a more powerful radiator by installing a thermostat on it.

Installation

As already mentioned, the boiler must be installed at the lowest point.
No pipe should be below the level of the entrance of the return pipe to our heater. Neglect of this requirement will lead to a significant deterioration of the heating system.
On the walls is marking the location of pipes and radiators.
Radiators are mounted - their position is checked by the building level.
A booster collector is mounted from the boiler supply pipe. It should be a pipe of large diameter.

An open expansion tank is installed at the top. If it is in the attic, then the vessel and the pipeline must be thoroughly insulated.
Pipes are mounted with a slope of 1 cm per linear meter of pipe. If it is not possible to adhere to this norm, then it is possible to reduce the drop to 0.5 cm, but not less. It should be borne in mind that with decreasing pipe slope, the efficiency of the entire heating system decreases.
In the right place is a tie-in pipe leading to the radiator. In the metal pipeline, the outlet can be welded or connected via a tee. When working with plastic pipes you need to use the fittings, soldering them, not forgetting the taps and thermostats (if their installation is provided).
At the lowest point of the system (usually near the boiler), you need to install a tap with a tap - through it water will be poured into the system.

When planning the production of a gravity system in a two-story house, you need to consider that the flow of coolant is carried out on the second floor, and then it is lowered onto the radiators installed on the first floor.

It remains to fill the system with water, and, checking it for leaks, heat the room, without worrying about the fact that they can turn off the electricity.

Video

Watch the video on how to calculate heating with natural circulation:

This video shows an example of heating with natural circulation: