Blog - The Importance of Balancing Radiators

The balancing of radiators on heating systems during commissioning is often overlooked but is vitally important. On heat pumps, many of which utilise variable speed pumps, this can be more difficult, especially with direct circulation to the emitters on open loop projects.

For a radiator, correctly sized at the design stage, to output the required amount of energy when installed and commissioned, it’s important that the correct flow temperature and water flow rate are delivered under design conditions. Too little flow rate and the Delta T (difference between flow and return temperature) will start to widen.

The effect of this drops the radiator mean water temperature (MWT), thus reducing the output.

As an example:

500W radiator output based on, 21°C Room temperature, 45/40°C F&R (DT5), giving a radiator MWT of 42.5°C.

Widening to DT20, 45/25°C F&R, the radiator MWT drops to 35°C, and this has a dramatic effect on the radiator output, nearly halving it to 287W.

This reduction is purely due to the flow rate, the radiator is correctly sized, but the energy required simply isn’t getting there.

Devices such as the Flow Balancing Valves give an Indication of the amount of Flow (Energy) being delivered when the DT is known and allow for easier commissioning. They can also help identify potential flow issues which may be down to other factors, such as pipe or pump sizing.