- The history of baseboard heating
- How the baseboard heating system works
- The principle of operation of baseboard heating
- Baseboard heating characteristics – pros and cons
In this article: the origins of baseboard heating; installation of a baseboard heating system; water and electric baseboard radiators; the principle of operation of plinth heating; why only copper and aluminum are used in the construction of baseboard radiators; plinth heating pros and cons.
With the onset of cold weather and until mid-spring, we are forced to additionally heat our bodies, despite the regularly working heating devices. How is it, after all, the radiators of the heating system and electric heaters warm up to the full, but the feet are still cold? It’s all about air convection – the warmest air, which receives heat from radiators and heaters, rises to the ceiling, and the cold one is always near the floor. To solve the problem of heating and freezing feet by the forces of the “warm plinth” system, and in fact, the rooms are heated not by its radiators, but by the radiation heat emanating from the walls heated by them.
The history of baseboard heating
Without any doubt, the founder of this method of heating can be considered a Russian heating engineer, professor Vyacheslav Avgustovich Yakhimovich. At the beginning of the last century, he developed and patented a steam-concrete heating system – pipes through which hot steam circulated and, in some cases, water was conducted through the walls and along them, covered with gypsum, concrete or wood panels on top. Steam-concrete heating of Yakhimovich had a number of advantages over the water heating of natural circulation that was gaining popularity at that time – heat was transferred from the coolant to the gypsum or concrete finishing layer, and these materials held it well and gave it to the premises in the form of radiation heat for a long time, which made it possible to cope with frequent malfunctions of heating systems. The disadvantages of steam-concrete heating, namely the need for overhaul of the walls in case of any leakage of heating pipes, the complex installation of the pipe system, requiring many days of work with stucco moldings and the high heat loss of the buildings themselves, prevented its spread in Russia. Meanwhile, in Europe, panel or radiant heating, based on the developments of Jachymovich, enjoyed high popularity in the 20th century..
However, in the USSR, there were still similar heating systems – heating steel or cast-iron pipes were laid along the walls along the line of the baseboard, the top was covered with concrete, from which the baseboard was formed. Such baseboard heating was used in the middle of the last century in children’s and medical institutions of the Soviet Union..
In Europe, skirting heating systems have developed more – hollow panels in the form of a classic skirting board have been developed, covering heating pipes equipped with vertical ribbing along the entire length. The ribs made it possible to increase the heat transfer of baseboard radiators by more than 60% compared to flat and round heating panels without ribs.
How the baseboard heating system works
Skirting heating is subdivided into hot water and electric heating. The main components of a water-cooled system are a radiator block for a warm plinth, a distribution manifold and oxygen-tight plastic pipes, placed inside a corrugated tube made of XLPE.
The radiator block consists of a heat exchanger and an aluminum box. The heat exchanger is made of two copper tubes, the outer diameter of which is 13 mm, the wall thickness is 2 mm, with vertical aluminum or brass lamellas fixed to them. The aluminum box consists of three strips, profiled by hot extrusion – the bottom bracket, the top and the front cover. Box width – 28 mm, height – 140 mm. Installation of the heat exchanger inside the box is carried out using holders of a special design.
The distribution manifold consists of two steel pipes parallel to each other, equipped with outlets, inlets, air vents, shut-off and drain thermo valves – the upper pipe is designed to be connected to the heat carrier supply source and its further wiring through plastic pipes to the heating radiators, through the lower one, the cooled heat carrier is returned to the heating boiler or, in the case of central heating, to the return pipe.
When building a baseboard heating, a plastic tube, with the help of which the coolant is delivered to and removed from heating radiators, is placed in a corrugated pipe. Since part of the heating circuit will have to be laid in the floor and passed through the walls, the outer corrugated tube will allow replacing the inner one without opening the floor – by simply removing the latter from the corrugated channel and inserting a new PEX tube into it. However, the complete absence of air inside the baseboard heating system and the immunity of plastic pipes to salts contained in the water will allow it to function trouble-free for a long time.
The highest temperature of water or antifreeze used in the baseboard heating system as a heat carrier should not exceed 85 ° C, the operating pressure should not exceed 3 atmospheres, otherwise the tubes made of cross-linked plastic will lose strength. Since the water temperature in the central heating system can be more than 85 ° C, and the operating pressure can exceed 9 atmospheres (when testing the heating system with a water hammer), additional measures are required. Instead of plastic pipes, you can use metal-plastic or copper pipes, connected to each other by soldering, as an option, use a heat exchanger, built in as a receiver of thermal energy from the central heating network, transferring it to the coolant to the baseboard heating system through copper plates. The last measure is especially effective, since it allows you to maintain high performance characteristics of baseboard heating and completely protect it from the temperature and hydraulic effects of central heating.
When installing a baseboard heating system, it may be necessary to equip it with additional equipment, such as: thermomechanical or thermoelectric thermostats for each group of heating radiators, a servo drive on the distribution manifold, a circulation pump, a pressure gauge and a thermometer at the coolant inlet to the manifold.
Electric baseboard heating is based on radiator blocks with built-in air heating elements, that is, its installation is much easier than systems with a liquid heat carrier. The appearance of electric baseboard radiators is completely identical to liquid ones, the difference is in the absence of pipes supplying the coolant, the heating element is built into the lower copper tube of the radiator, and the power cable is laid in the upper one in heat-resistant silicone insulation. The power of the heating elements is 200 W for each running meter, the power source for them is an ordinary household electrical network. Despite the high level of moisture protection, electric baseboard radiators are not intended for installation in rooms with high air humidity.
The principle of operation of baseboard heating
Plinth heating radiators are not able to warm the atmosphere of the room by convection of air, since they are located close to the planes of the walls and the air convective flow emanating from them is influenced by the Coanda effect.
The strange behavior of a jet of hot air from a lighted candle – its aspiration to any nearby surface – was noticed by the English physicist Thomas Jung, who mentioned this in a report he gave at the Royal Society of London in 1800.
A detailed study of the effect of “sticking” of an air stream to nearby surfaces was carried out by the Romanian scientist Henry Coanda, who accidentally discovered it at the beginning of the 20th century, one of the first researchers of aerodynamics. During experiments with a jet turbine, created according to his project, Coanda discovered the same physical effect as Jung 100 years ago – the flow of fluid from a working turbine rushed to the wall located on the side of it, and seemed to stick to its surface. After conducting additional experiments, the scientist found out that the air flow behaves in the same way. In 1934, Henry Coanda named the effect he discovered in his honor, explaining it as follows – a zone of reduced pressure forms near surfaces, caused by their impermeability and free access of air from only one side. At the same time, the covering air flow spreads over a large area, developing only along the enclosing surface.
Radiators of the warm plinth system are installed along the external (one side facing the outside of the building) walls. The box formed by aluminum strips has two horizontal slots along its entire length – one is located at the floor, in the front panel, the second is in the upper part, closer to the wall. Cold air enters the inside of the box, heats up and rises, as with any heating equipment, the heating principle of which is based on air convection, but in this case the air flow obeys the Coanda effect and spreads only along the wall surface. As a result, the heat from the air is not transferred to the air atmosphere of the room, but to the structural material of the wall, which, like IR heaters, emits uniform heat in the form of infrared rays as it heats up.
Since the room is heated not due to convection, there is no need for high heating of the coolant – in the design of radiators, it is only required to use materials with a high coefficient of thermal conductivity. This explains the use of copper and aluminum, the thermal conductivity of which is 390 and 236 W / mK, respectively. For example, for iron, this coefficient is only 92 W / m K, and for metal-reinforced plastic, it is 0.43 W / m K, that is, copper and aluminum are the most suitable materials for baseboard radiators..
The maximum temperature of the aluminum box of the warm plinth during the operation of this heating system will be no more than 40 ° C, and the surface of the wall, next to which the radiator is installed, will not be warmed up above 37 ° C – it will not be possible to burn yourself on them with all the desire.
Baseboard heating characteristics – pros and cons
Positive properties of a heating system based on baseboard radiators:
- lack of convection air movement, accompanied by dust weighing;
- infrared heat positively perceived by the human body;
- even distribution of heat throughout the room, only opaque objects in the room are exposed to infrared heating;
- Warm air does not accumulate near the ceiling, which is usually the case with convection heating. The same temperature is established throughout the air volume of the room;
- the surfaces enclosing the room have a temperature acceptable for a person, that is, they do not steal heat from human bodies;
- the problem of moisture deposition on the surfaces of walls and ceiling is completely solved – they will always be dry, which means that neither mold nor lagging of finishing materials threatens them anymore;
- the installation of the baseboard heating system is carried out quickly, regardless of the age of the building. Skirting radiators, although they are somewhat larger than a wooden skirting board, are not striking as clearly as cast-iron or bimetallic radiators, usually installed under a window opening;
- the absence of the need for a high temperature of the coolant can significantly reduce the consumption of fuel spent on heating it – the savings will be about 30–40% compared to the needs of classic heating systems. In addition, fuel savings are achieved by reducing the air temperature in the premises – if the walls are heated to +22 ° C, then the comfortable air temperature will be +16 ° C, compared to +20 ° C of air and walls with a temperature of +18 ° C that draw heat from household members;
- high maintainability of system elements, which makes it possible to do without dismantling the finishing coatings in case of need for repair;
- equipping with thermostats allows you to set the optimal temperature in each room equipped with baseboard radiators, separately.
It should be noted that the baseboard heating system can also be used to cool the premises, if it is filled with a cold liquid carrier – the Coanda effect will work in this case, only with less efficiency. When using a system for cooling, it is important to maintain the temperature of the liquid in the system at a level higher than the dew point in these conditions (depending on the humidity of the air and its temperature), otherwise condensation will form on the surfaces of the circuit, which must be removed somewhere.
The disadvantages of the system include:
- high cost – about 3000 rubles. per meter of the heating system with its installation. However, this price is due to expensive materials that are extremely necessary in baseboard heating;
- the installation of the system is carried out only by professionals who have the appropriate certificates from manufacturers of baseboard heating systems. An amateur approach to installation will not allow achieving the required thermophysical characteristics, will significantly reduce the service life;
- the maximum length of one heating circuit should not exceed 15 running meters – one of the reasons why the system must be equipped with a distribution manifold. With a greater length of the circuit, the heating efficiency decreases markedly;
- installation of various decorative overlays on the radiator box is not allowed, since they reduce heat transfer;
- tighter fit of baseboard radiators to the wall surface, which allows full use of the Coanda effect, eventually leads to warping of the film wall decoration;
- it is required to keep the room heated by baseboard radiators as free as possible, without blocking the surfaces of the baseboards and walls with cabinet furniture, since this prevents convection and infrared radiation, distorting the air flow and absorbing IR heat emitted by the walls.
In the last century, baseboard heating, like radiant heating in general, was not very popular due to the high heat loss of building materials – it was easier to heat the air by convection, which made it possible to quickly compensate for heat loss, despite the obvious disadvantages of such heating. By the way, it is for this reason that heating radiators were installed under the window openings – through the cracks in the frames and the glazing area, the cold penetrated especially quickly.
Today, there are building and finishing materials for facades that can significantly reduce heat loss through the enclosing structures, and modern window frames equipped with thermal-retaining glass units do not allow air to pass at all. All this makes it possible to move away from classic convection heating systems to more efficient radiant heating, while significantly improving the quality of living in our houses and apartments. In the coming years, pipes and heating radiators, usual for systems with forced and natural (gravitational) circulation of the coolant, will disappear from our homes – they will be replaced by more advanced heating equipment.