It turns out that many people are not quite sure what a Low Loss Header is and what its role is in central heating installations. We often receive emails or calls like: "The plumber said I need to install a low loss header in my system, can you tell me what this low loss header is for?"...
A Low Loss Header for central heating, sometimes known as a hydraulic separator is a simple device used in modern heating systems, often in installations with gas boilers (condensing) or, for example, with heat pumps.
✅ Why with these devices? Because condensing boilers and heat pumps - especially require balanced pressures in the heating system to operate most efficiently and economically - in other words, the best. In these systems, the low loss header divides the heating system into 2 smaller sub-systems, thereby balancing the pressure in the central heating system and ensuring the most efficient operation of these devices. It is particularly useful to divide the system in large buildings, where it becomes quite extensive, causing uneven flow rates.
✅ In this way, the hydraulic coupling definitely influences long-term savings, but let's be honest - it should be installed in systems where there are technical indications; it is not a way to reduce heating costs in every installation.
Balance of systems in terms of flows and pressures is not the only function of the low loss header. As we mentioned, it divides the installation into two parts, creating something like a separate heating circuit for the heat source (such as a boiler). The second part constitutes the heated system.
✅ Therefore, the low loss header ensures that water does not cool down so quickly in the short circuit - there is no so-called cold return, allowing boilers to operate better. As a result, it also balances temperatures. This means that it is sometimes desirable in installations with solid fuel boilers or pellet boilers. By preventing the cold return, hydraulic couplings also prolong the lifespan of boilers and are often recommended by manufacturers of heating equipment for this purpose.
❌ Cold return - so the lack of temperature balance, destructive for heating boilers and heat pumps - is what we'd like to avoid. Low loss header should help us with this. Another types of solution of a Cold Return problems are Plate Heat Exchangers or Mixing Valves (3-way / 4-way valves).
In the latter application, the low loss header actually functions as a heat exchanger, but it is not. ✅The difference lies in the fact that in the case of the header, the fluids of both sub-systems actually come into contact with each other and can mix. In the heat exchanger, there are not two sub-systems, but two fully separate systems (usually closed/open), as the heating system water does not mix with the water from the heated system in the exchanger.
Therefore, the exchanger can connect two independent heat sources - which require separate systems (e.g., a gas boiler in a closed sealed system with a fireplace with a water jacket in an open system). The exchanger thus has certain advantages over the low loss header, although both devices have their proponents and advantages.
Most often, it takes the form of a steel tube, cylindrical or sometimes cuboid. It is installed in the boiler room, on the wall, to have a stable hanging position. There are couplings for horizontal mounting, although vertical ones are becoming increasingly popular, which also have better air venting capabilities - and separate accumulated impurities from the installation, which can be removed (vertical couplings usually have a drain valve at the bottom).
✅On the market there are also more sophisticated Low Loss Headers sets available featuring an integrated distributor/manifold for heating circuits. In such cases, they can certainly be much more elaborate, with their function potentially being much more significant.
Actually, nothing, it is only about making the Low Loss Header a place where water entering the hydraulic separator partially mixes with water from the so-called return. In this way, the pressure should balance. In many manufacturers, there is a metal mesh inside the header to better balance the flows. However, it is needed only if the header outlets for both sub-systems are directly opposite each other, and the water could flow through them freely.
✅ Low Loss Headers without a mesh - rely on a different solution - they have connections on both sides not opposite each other, so that supply and return water can mix independently of the situation. Therefore, the metal mesh inside the coupling is not always necessary, although its presence certainly does not hurt.
In comparison to other hydraulic equipment, especially for central heating - low loss header prices seem to be moderated. Of course there are different type of low loss headers and different solution, so the price will differ. However ✅ the simpliest systems which can be sufficient for single-family houses start from 90-100 €.
More sophisticated low loss headers systems quite often contain hydraulic circles distributors - and can be mounted even in case of bigger buildings. Their prices start from cca 250 €.
It depends on the type of hydraulic separator or set. Classic low loss headers have inputs for the heating circuit and the heated circuit, but there are also couplings to which several circuits can be connected, even several.
An important element of the low loss header nowadays is also its insulation. The low loss header is a long cylinder with a fairly large external surface. If we do not want it to function in the boiler room as an additional radiator (which we certainly do not need in the boiler room), the cylinder should be insulated.
✅ Below is a technical drawing (without dimensions) of a classic hydraulic low loss header designed for vertical installation by NORDIC TEC. The drawing also shows an air vent valve at the top and a drain valve at the bottom for better orientation. As can be seen, the connections for the boiler circuit and the heating circuit are not opposite each other so that the water can mix and balance.
✅ Below is the same central heating low loss header with the possibility of connecting 2 heated circuits and the heating circuit.
We recommend Nordic Tec hydraulic couplings. We ensure good quality, thanks to the construction of solid steel, couplings from this brand are a purchase for many years.
PUH LEDNET / Nordic Tec Team
Low loss header explained - structure, principles of operation, application
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