"You need a water gun, the system won't work without it. Or, let's put you a low loss header. " Such suggestions can be heard from some installers as well as from heating equipment sellers. Although in fact you don't need it.
In order to reasonably refuse the "golden" advice of plumbers, it is necessary to understand the simple principle of operation of this device. To do this, I made small diagrams, according to which it is easy to understand what's what.
If you have or have a simple heating circuit, as in the illustration above, then you absolutely do not need hydraulic separator (hydraulic arrow). Ponder this word, " share hydraulics", having one pump and radiators to share is nothing unnecessary.
But let's say you have a radiator network and a warm floor, then in these schemes two flows intersect, respectively, two pumps are working:
This scheme also does not require additional interventions in the form of a hydraulic arrow. It is not very difficult to calculate the power of two pumps so that they do not interfere with each other. Therefore, no extra costs are required. As much as installers and sellers would like.
Difficulties can arise in a heating system where there are three or more consumers. Suppose an indirect heating boiler appeared in the circuit. In order to warm up the "barrel of water", an additional pump will be needed, which will take the coolant from the systems for heating, thereby affecting the hydrodynamics of the system, which, with the correct calculation of pumping capacities, will not critical. The main thing is correct calculation.
But what if there is a need to play it safe, or it is planned to connect to the system, of your choice: a Winter Garden, a swimming pool, a bathhouse, heated street paths and blind areas, and even a doghouse. In these cases, it is necessary to separate the streams, so that later you do not find out why one branch works and the other does not, or the heating system does not "fury" at all.
What is the use of a hydraulic arrow in the heating system?
How will the system work with large numbers of consumers without a hydraulic arrow? Overflows from one circuit to another will begin, a more powerful pump will push the coolant into its branch, taking the liquid into its pipeline from other circuits, or other branches will simply stop due to the critical pressure difference between the suction and outgoing pipeline.
Therefore, by installing a low loss header, the pressure on the supply and return is equalized, regardless of the number of consumers. Therefore, there will be no fluid flows between the circuits:
Hydrostrelka performs the function of a kind of bottomless barrel from which pumps, on any of the branches, can take as much coolant as they need, without taking it away from neighboring circuits. Additionally, this device performs the work of a sludge trap and degasser.
If your system has three or more circulation pumps that can critically affect the operation of each other, then installing a flow divider is desirable, and in most cases necessary. Or you should use the principle of primary and secondary circuits, which we will talk about a little later.