To use Castrads' heat requirement calculator, simply enter the values in each field and click on calculate to display your heat requirements.
To calculate how big your cast iron radiator will need to be, simply divide the number of Watts required by the heat output of your chosen cast iron radiator. You can find the heat output for Castrads' cast iron radiators here.
The heat calculator is based on a delta T value of 60, that is the water circulating through your cast iron radiators is 60° warmer than the ambient temperature of your house. This may not be the case.
Correction factors for a range of delta T values are shown below. To correct your calculated value, multiply the BTUs or Watts required by the factor shown.
Both ground and air source pumps can be used with Castrads' cast iron radiators. The water heated by this method is typically around 50°C at best, so a correction factor of between 2.36 and 2.96 should be applied.
The fluid used in source heat pumps is usually propylene glycol or methyl alcohol mixed with water. Both of these solutions are safe to use with cast iron radiators. Please contact your heat pump engineer for more information.
The U Values used for the calculations are taken from BRE publications (formerly Building Research Establishment). The calculator provides Wattages for a delta T value of 60. The correction factors shown above should be applied to obtain realistic values. Castrads' heat calculator should never be used in place of a professional heat loss survey. Castrads accepts no liability for incorrect heat requirement values obtained using The Heat Calculator.