All radiators have a wattage rating depending on surface area [which amounts to heat dissipation] so a twin radiator will be twice the rating as a single of the same size,there is also radiators with single or double fins on the back which ups the rating even more, to calculate visit. http://www.simplifydiy.com/plumbing-and-heating/radiators/power which will help you to calculate the total kilowatts required as against the boiler which is 24 kw
toptrish, January 2014
