The importance of balancing UFH systems

Nigel Sanger from JG Speedfit looks at the importance of balancing UFH systems, revealing best‑practice techniques and highlighting the importance of this often-overlooked process.
Balancing is a fundamental aspect of any underfloor heating (UFH) installation and something that is critical to ensure peak system performance. Unfortunately, this process is often overlooked or rushed by installers, leaving an inefficient system. To understand how UFH balancing should be carried out, it is important to firstly understand why it is so important.
When radiators are installed in a property they will come in various sizes – the largest radiators will have a larger output and therefore need more hot water flowing through them. However, the natural path for water to take is to flow to the smallest radiator as it presents the least resistance, reducing the flow available to the larger radiators. This sometimes stops some radiators from working at all. This means that the system needs to be balanced in order to ensure that the correct volumes of water are being sent to both the large and small radiators, creating maximum operating efficiency.
The same occurs in UFH systems because these use both long and small circuits of pipe. Large volumes of water will naturally flow to the shortest circuits of pipe at the expense of larger circuits, creating a less efficient system.
Go with the flow
To ensure maximum efficiency, UFH systems need to be balanced. Installers need to create artificial resistance within short pipe circuits and less resistance in the longer circuits to ensure that every circuit has the correct volume of water flowing through it. The working principles and installation techniques required to do this are similar to those involved with installing a radiator system.
Radiators typically have two valves – a TRV and a balancing valve. The TRV will open and close the radiator depending on the need for heat. The balancing valve is used to control the volume of water flowing through the radiator. Typically, the valve is turned down until the designed temperature difference between the incoming flow and outgoing return pipe is reached.
Installers will often have to close the valve on the smaller radiators to the point where they are almost shut, restricting the flow to smaller radiators and increasing flow to larger radiators.
A similar methodology is applied to balancing UFH.
Balancing a UFH system requires the manual adjustment of the flow meters on the UFH manifold. These dictate the level of water flow supplied from the manifold to each individual heating circuit in a property. The action involved in this task is simple – installers just need to open or close the flow meters until required flow is indicated. The challenge for many is understanding the level of flow required for each circuit.
Gauging the right level
When Speedfit designs UFH systems, for example, we know the exact length of pipe in each circuit and can accurately advise installers on the level of adjustment required for the flow meters. This is included in the design sheet – all that needs to be done is to match the required level of flow to each circuit.
However, as a very general rule, UFH systems require half a litre of water for every 20m of pipe, up to 2.5 litres of water for a pipe which is 100m in length. By following this procedure, installers can ensure that systems are as balanced as possible, and that certain zones in a property are not being heated at the expense of others.
A two-minute job
A common reason for overlooking UFH balancing, aside from a lack of knowledge, is time restraints. In reality, though, it takes just two minutes to successfully balance a standard UFH system. The efficiency gains that can be realised from UFH balancing can often mean the difference between a satisfied customer and an unsatisfied one. Therefore, taking a little time to perform this task can significantly reduce the number of call-backs installers receive from customers experiencing inefficient systems, and inconsistent heating patterns.