When several rings of radiator or floor heating are connected to the distributor collectors on a floor, one must strive to equalize the lengths of these rings and quantity of radiator sections sitting on each heating ring. That is, the supply of warmth carrier in each heating ring connected to one collector group should be the same. But is it always possible? For example, suppose there is a contour of warm floors in the kitchen, in the living room, and in the bathroom, connected to one collector group. It is obvious that the floor areas in these rooms are different and the length of pipeline in the floors are also different. Of course, the supply of warmth carriers in the pipelines of different lengths will be different at well. In the short heating rings, the hydraulic resistance of the pipes will be less and the warmth carrier in them will circulate faster than in the longer heating rings. Hence if there is an equal temperature of warmth carrier in the supply collector for a floor, then some rooms on that floor will be overheated and some will be cold. The same applies to the radiator heating rings with different quantity of sections and different lengths of pipelines which are connected to one floor collector group: it will be cold in some rooms and hot in others. We already know that the supply of warmth carrier in radiator heating can be regulated by installing thermoregulators on each radiator — valves, in fact, which perform quantity regulation of supply. We can do roughly the same thing for the warmed floors.
Balancing the heating contours of warmth floors which are connected to one collector group can be achieved in two ways. First, make all the rings the same length and distribute them to the floors. For example, one contour will be in the bathroom, two contours in the kitchen, and three contours in the living room. Second, make the number of contours the same as the number of rooms, but attach them to the collectors, not directly but through special devices called supply metres or balancing valves. In this case, the name «supply metre» is used not to mean a measuring device, but to indicate a special valve which performs the function of quantity regulation of warmth carrier supply. The supply metres of some manufacturers are connected only to the return collector.
An interesting collector group (see Figure 37) is illustrated by the «Caleffi» company: their supply collectors are equipped with supply metres and return collectors with thermoregulators; thus the supply collector directs a strictly definite quantity of warmth carrier into each heating contour and the return collector opens and closes the heating contours according to the temperature in the floor. Furthermore, the supply collector has an automatic air purger and both collectors are joined with a bypass with an integrated relief valve. The air is removed through the automatic air purger from the whole warm floor system and if, as a result of outside warming, the thermoregulator turns off the contours, then the relief valve starts to act and resets the dramatically increased pressure.
It is necessary to note that there are on the market a lot of supply metres, as measuring devices and regulating valves. If for example you use a supply metre which performs only measurements, then it should be installed together with a usual valve (tap). By opening or closing the tap, the desired setting of warmth carrier supply is adjusted on the scale of the supply metre.
How is balancing of heat contours achieved? The starting point for the total supply of warmth carrier through the collector (litres per minute) is 100%. Then the supply for each heating contour is calculated as a percentage. For example, it can be 20%, 30%, and 50%, and proportionally then converted into litres per minute. By twisting or untwisting the head of the supply metre (or the tap by the measure supply metre), the necessary values are put onto the devices. It should be noted that in this way it is possible to achieve this calculated balancing of the contours. The actual balancing is performed by the actual readings of the supply of warmth carrier through the collector group; for this, a measure supply metre must be installed in front of the supply collector and, based on its reading, you must divide the total supply by the contours connected to the collector.