Heating systems, depending on access to energy conductors, can conditionally be divided into two varieties:
- Open (popularly called gravity). The most primitive in design and operation. But the number of its shortcomings completely negates its advantages: it is expensive to buy material, large-sized, difficult to assemble, low efficiency, thick-walled pipes with a large diameter are used, and because of these materials it is very difficult to hide the entire system behind decorative panels. This open heating system is most often found in Soviet houses.
- Closed. All structural details are connected tightly to each other and with the help of a low-power pump, the coolant is accelerated.
The working process of an open system is based on the laws of thermodynamics, according to which the heated liquid flows upward, creating a certain vacuum at the inlet to the boiler and increased pressure at the outlet of it. Thus, the pipes of this design undergo self-circulation, where water moves from high pressure to lower. During circulation and temperature changes, the water expands, as a result of which, in order to avoid breakage, the system is equipped with an additional tank called an “expansion tank of an open heating system”. It is not airtight; heated water in the form of steam enters the atmosphere through it.
An open heating system, justifies itself only with the use of water and no other energy conductors, since it is a cheap resource. Another disadvantage is the constant evaporation of the liquid, which must be periodically renewed so that the entire structure is not aired.
Open heating systems have a huge drawback, which is slow circulation, which is why heating must be carried out very slowly to avoid damage. Not to mention the slowness, immediately there is a problem with the discharge of water in the winter season with idle pipes, so that the frozen water does not damage them.
To achieve a sufficient level of water circulation speed, the boiler of the specified system should be placed as low as possible, and the expansion tank, on the contrary, should be in the highest place. The tank, in turn, needs to be insulated. An open heating system does not need a pump. When installing this design, you need to abuse bends and fittings as little as possible.
An open heating system requires pipes of various diameters. This feature is a characteristic feature of this design. The diameter of the larger pipe, which is installed at the outlet of the boiler, with a heating area of 50 to 100 m² is approximately 40 mm. Accordingly, the increase in area makes proportionally increase the diameter and financial costs.
Among other things, it is necessary to take into account the slope of horizontally laid pipes, which is approximately 0.005-0.01% in the direction from the highest point to the heating radiators and then to the boiler.