Guidance on BTUs and Watt output for cast iron radiators

All retailers of Cast Iron Radiators in the UK use either British Thermal Units BTUs or Watts to specify the projected heat output of their various castings. When selecting a cast iron radiator you should talk carefully to your plumber to understand the heat requirements of the room you are putting your cast iron radiators in. Different rooms require different suggested average temperatures and therefore different levels of heat input. Furthermore, factors such as whether there are external walls, the quality of your boiler, whether you have double glazed windows and the heat insulation you have in your property will all effect the heat requirements of your room.

If you see a cast iron radiator that is advertised with a suspiciously high BTU heat output, you should also ask to what Delta standard the BTU heat output figure is. As a manufacturer of cast iron radiators in the UK, we see many retailers selling the same cast iron radiators with different suggested BTU heat output figures. Perhaps they do this to confuse customers, perhaps to try to suggest that their casting is in some way better than an identical casting bought elsewhere or perhaps it is to justify their higher prices.

The industry standard is to quote BTU heat output figures or Wattage heat output figures using a Delta 50 figure - however, many retailer use Delta 60 figures to make their radiators appear to have a higher heat output. However, when you speak to your plumber they may suggest that even this is a little high. Many heating professionals prefer to work with a Delta 50 figure.

However, there are retailers in the UK that publish BTU heat output figures using a Delta 80 figure - this is deliberately misleading and if you see castings with suspiciously high heat output you should proceed with caution. Buying cast iron radiators using a misleading delta 80 heat output figure would almost certainly mean that your cast iron radiators are not big enough to heat the room.

If you have any questions or if you want to talk to an expert, please do not hesitate to contact us on 01723 321 000.