# Different Companies Sometimes State Different Heat Outputs for the Same Radiators, Why?

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

For example:

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

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) – assumed to be at 90ËC
• Return water temperature (on exiting the radiator) – assumed to be at 70ËC
• This means the average water temperature running through the system is assumed to be 80 ËC
• From this figure, you minus the average room temperature – assumed to be 20 ËC
• This equates to the Δt60 Ë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 75ËC
• Return water temperature (on exiting the radiator) – assumed to be at 65ËC
• This means the average water temperature running through the system is assumed to be 70 ËC
• From this figure, you minus the average room temperature – assumed to be 20 ËC
• This equates to the Δt50 Ë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.

The reason that retailers still often use the original British Δt60 ËC is because most domestic plumbers and heating engineers still calculate heat requirements to this standard. Although most manufacturers now using the European standard of Δt50 ËC.

The important thing is to compare like with like. Check whether your heat output requirement has been calculated at the Δt60 ËC or Δt50 ËC standard then match the radiator output using the same standard.

It is easy to convert a Δt50 ËC heat output to a Δt60 ËC heat output and vice versa:

• To convert Δt50 ËC to Δt60 ËC, multiply Δt50 ËC figure by 1.264.
• To convert Δt60 ËC to Δt50 ËC, divide Δt60 ËC figure by 1.264.