What does balancing mean? Well for older gas and oil boilers and also for electric, heat pumps and biomass boilers, it just means making sure every radiator gets hot. Water will always take the path of least resistance, so unless it is coaxed round all of the radiators it will just circle around the one closest to the boiler.
In order to balance the system, heating engineers have to restrict the access to radiators nearer to the boiler (using the thermostatic radiator valves or TRVs) and open up the access on the radiators further away. In this way the hot water is circulated around all of the heating system. Radiator valves come in many shapes and styles and we compare the majority of them in our comprehensive Guide to TRVs
For a modern gas or oil fired heating system, the temperature of the water as it goes back to the boiler has to be below 54 degrees (ideally lower) in order for the boiler to operate in ‘condensing mode’. If the system is not properly balanced then the temperature of the water back to the boiler will be over 54 degrees.
The boiler will still work, but it won’t be efficient. Fortunately there are a number of radiator valve products available that will ensure the system stays balanced which increases the efficiency enormously provided they are set up correctly.