What is hydronic balancing?

In this article I will explain what hydronic balancing is and which steps are necessary to balance a heating system. For the term hydronic balancing the term hydraulic balancing is often used. Hydraulic balancing is relatively simple.

Hydraulics is the science of the flow behavior of liquids. Since the medium water is usually the energy carrier in a heating system, it is possible to improve the flow behavior of the heating water in the heating system with a hydraulic balance. This optimization process is called hydronic balancing (or hydraulic balancing).

Important: Hydronic balancing is mandatory in heating systems with circulating pumps.

What happens in a heating system without hydronic balancing?

The flowing water in the heating system always selects the lowest resistance. For this reason, the following phenomenon occurs in non-hydraulically balanced heating systems: Rooms that are close to the heat source are overheated and rooms that are far away from the heat source are too cold (see figure 1).

In order to counteract this phenomenon, so-called “first aid activities” are usually carried out. This often involves increasing the flow temperature in the heating system, the delivery head of the heating pump and the pump power.

These actions ensure that it gets warm in distant rooms, but bring with them new problems: by raising the flow temperature, a temperature increase takes place in the entire building. Rooms that are close to the heating source are hydraulically advantaged and can be so overheated that the high room temperatures usually can only be adjusted or reduced by excessive aeration.

These “first aid measures” thus lead to increased energy consumption. Furthermore, due to the increase in the delivery head and the pump power due to the higher volumetric flow rate, there are flow and crackling noises in the heating system and an unnecessary amount of pump current is consumed.

What happens in a heating system with hydronic balancing?

In a hydraulically balanced system, the flow behavior of the heating water is optimized and each radiator receives only as much heating water as it needs. This leads to the fact that there are no hydraulically over-advantaged or disadvantaged radiators (see Figure 2).

This is achieved by presetting radiator valves on the radiators, balancing valves or differential pressure controllers on the individual strings as well as by optimally adjusted and dimensioned electronically controlled circulating pumps.

The volumetric flow rate is limited by presetting the radiator valves on the radiators. The flow rate is also limited by balancing valves. Differential pressure controllers ensure a constant differential pressure in the respective strings. The setting of the ideal delivery head and the ideal flow rate for the electronically controlled circulating pump ensure an even and quiet flow of the heating water in the heating system.

These steps allow the radiators to heat up evenly, the control behavior of the radiator thermostats is optimized and energy consumption can be reduced by 10 to 15 percent.

If you would like to do a hydronic balancing yourself or need a procedure to do a hydronic balancing, you will find the overview of my series below:

Seven steps to hydronic balancing

Do it Yourself (DIY): In the following series I will show you in an example how you can do a hydronic balancing yourself with a simplified calculation method. In the series, I will proceed step by step so that you successfully reach your goal.

I hope I could bring you a little closer to hydronic balancing. If you have questions, suggestions or criticism to this contribution, use the comment function.

Greetings! Martin

Further links and sources:
Wikipedia – hydronic balancing
Erklärung – hydraulischer Abgleich von 2-Rohranlagen
VDMA 24199  – “Regelungstechnische Anforderungen an die Hydraulik
bei Planung und Ausführung von Heizungs-, Kälte,
Trinkwarmwasser- und Raumlufttechnischen Anlagen”
ZVSHK – Fachinformation zum hydraulischen Abgleich