The majority of standard central heating systems within the UK run off Delta 60 calculations. In plumbing this refers to the difference in the temperature between the water circulating in the central heating system and that of the ambient temperature. For example, the temperature into the cast iron radiator is 80° and the desired room temperature is 20°. 80 degrees minus 20° = 60° (This is why we quote at Delta 60). For most of our UK based customers using standard central heating systems, we use Delta 60. For systems such as ground source heat pumps a lower delta may be required such as Delta 50, please speak to your plumber and they will be able to offer advice. For Example One of our customers recently had a situation where the temperature into the cast iron radiator was 75° and he wanted his room temperature to be 20°. So he needs Delta 55 figures. As shown below – he needed to up his radiator size by a factor of 1.11 For example, if the requirement would have been for 10 sections of cast iron radiator in a normal situation (Delta 60) then he now needed to go up to 11 sections. Please see the information below on how to calculate the number of sections required when the radiator output per section is based on Delta 60. Delta T = 60° x 1 Delta T = 55° x 1.11 Delta T = 50° x 1.28 Delta T = 45° x 1.43 Delta T = 40° x 1.67 Delta T = 35° x 1.95 Delta T = 30° x 2.36 Delta T = 25° x 2.96 Delta T = 20° x 3.91 Delta T = 15° x 5.60 Click Here To Build Your Bespoke Cast Iron Radiators