Hydronic balancing and effective control

The easy way to optimal heating.

Lower heating costs and increased living comfort with automatic hydraulic adjustment.

Here you will find all relevant information about hydraulic adjustment and effective control for heating systems with animations, articles, infographics, videos and guides to help you in your daily work.

Increase efficiency through effective control and hydraulic balancing of heating systems

Over 80% of existing heating systems have a huge potential for optimisation. Hydraulic balancing ensures the optimal distribution of water flows in a heating system, so that the right amount of heating water is available at the right time in the right place in the building.


Tests by Salford University have shown that controls are the key to improve efficiency.  They found that a condensing boiler without temperature controls will run in condensing mode for only 5% of the time, whereas one with temperature controls ran in condensing mode for up to 80% of the time.

Click on the animated parts of the graphic. Do any of the practical questions sound familiar to you?


Find out more about the different types of balancing and the benefits by clicking the tiles below.

Why are some of my radiators too hot and others not hot enough?  Some radiators make a ‘hissing’ or ‘gurgling’ noise as well.

Answer: Actually, the noises are always caused by excessive flow velocities at the radiator valve due to excessive differential pressures. The cause: Incorrectly set or not set external circulation pumps, condensing boilers with integrated pumps, and, especially in larger systems, excessively high differential pressures in the case of partial loads due to the lack of zoning and manual balancing valves.

Can upgrading controls help reduce my customers’ bills?

Answer: Absolutely, research has shown that upgrading a standard room thermostat to one with load or weather compensation, can reduce gas usage by 10-12%.  In addition to this, it has been proven that a boiler can use 18% less gas when TRVs are fitted to all radiators outside of the room with the room thermostat.

Why is the return temperature too high?

Answer: Quite simply: It’s due to a lack of effective controls, and because no hydraulic balancing was carried out. In condensing systems in particular, the return temperature must be as low as possible so that the highest possible degree of condensation (use of latent heat) is achieved over the entire heating period from the exhaust gas heat exchanger. If the volume flow at the individual radiators is limited, the radiator has more time to release the heat from the water (constantly), which not only leads to a lower mixed water temperature in the return but also increased comfort for the end user.

What benefit does a differential pressure controller offer?

Answer: For you the installer, a self-balancing TRV like the RAS-B2 will allow you to balance the heating system in a fraction of the time, it’s incredibly easy to calculate the required flow for each radiator and corresponding position for the setting ring.  For your customer, they’ll enjoy precise comfort with no hot or cold spots around the home as well as the added benefit of lower heating bills thanks to the fact that the boiler will run in condensing mode for longer.

I know the boiler is working efficiently because I can see the flue ‘pluming’ on cold days?

Answer: Unfortunately, the evidence of pluming means the boiler is losing energy through the flue.  The pluming you see on colder days is caused by water vapour that is released from the flue gasses when they are warmer than the outside air.  The lower the return temperature to the boiler, the more energy the boiler can reuse from the flue gasses.

What role does user behaviour play?

Answer: An increasingly important one! Ultimately, the goal of heating optimisation should be that the user feels comfortable and at the same time saves energy and money. That’s why it’s so important to explain to your customer how to use the controls you’ve fitted to ensure comfort and energy savings go hand in hand.

Will a lower flow temperature help increase the boiler efficiency?

Answer: Absolutely, in fact, it’s relatively simple to do so by installing a load compensating room thermostat.  A modern room thermostat featuring load compensation not only provides a compliant solution to the latest requirements of Building Regulations Part L, but like TRVs they also qualify for 0% VAT when installed as a standalone upgrade to an existing heating system.  A load compensating thermostat varies the flow temperature from the boiler in relation to the difference between the measured room temperature and the room thermostat set point. This is achieved by directly modulating the output of the boiler, thus reducing the amount of energy used.

When does it make sense to replace the heating circulation pump?

Answer: It certainly makes sense to replace an old “electric power guzzler” with a new high-efficiency pump. It’s important: An effectively balanced system will allow the pump to run at a lower speed and help save even more energy.

How big are the pressure losses in the pipelines?

Answer: A good question, as a general rule, a standard domestic heating system has a pressure loss (differential pressure) of around 0.1 bar (10 kPa) across the system.

How do I determine the presetting on the thermostatic valve?

Answer: Simple, the Danfoss Installer App has a handy radiator pre-setting tool for just this purpose.  You can calculate the correct pre-setting for each valve by entering either the size and type of radiator, the calculated heat requirement of the room or the output of the radiator.  The App does the hard work for you.

Hydronic balancing and effective control 6 Items