Calculating your heat output requirement from a radiator and finding the appropriate size of radiator can be confusing.

For example:

You provide your room measurements and your radiator specialist, Joe Bloggs Radiators, recommends that you need 1200 Watts heat output from your radiator. Consequently they recommend a radiator that meets your requirements; X radiator in white, 600mm high x 1000mm wide, which gives out 1264 Watts.

However, your plumber tells you that the same radiator, X radiator in white, 600mm high x 1000mm wide but from his supplier, ACME Radiators, only gives out 1000 Watts. How can this be?

The answer is probably that Joe Bloggs Radiators are advertising their heat outputs at the British standard whereas ACME Radiators are advertising their heat outputs using the newer European standard.

To explain, heat outputs can be measured in 2 different ways; the way they are measured is done against the “delta T” or “Δt” of the system.

In the UK, the standard for calculating heat outputs is illustrated by the following example:

• Flow water temperature (on entering the radiator)  keluaran hk  – assumed to be at 90˚C
• Return water temperature (on exiting the radiator) – assumed to be at 70˚C
• This means the average water temperature running through the system is assumed to be 80 ˚C
• From this figure, you minus the average room temperature – assumed to be 20 ˚C
• This equates to the Δt60 ˚C standard.

In Europe, the standard for calculating heat outputs is illustrated by the following example:

• Flow water temperature (on entering the radiator) – assumed to be at 75˚C
• Return water temperature (on exiting the radiator) – assumed to be at 65˚C
• This means the average water temperature running through the system is assumed to be 70 ˚C
• From this figure, you minus the average room temperature – assumed to be 20 ˚C
• This equates to the Δt50 ˚C standard.

To be clear, there is no difference in the radiator, it is just a different way of recording the performance. Like metric versus imperial; the numbers may be different, but they mean the same thing.