For Condensing boilers, the temperature of the water coming back from the radiators needs to be 45C in order to hit the advertised efficiency and eponymous "con

For Condensing boilers, the temperature of the water coming back from the radiators needs to be 45C in order to hit the advertised efficiency and eponymous "condensing", this is why their real measured efficiency is more like 75-85% than 96+% Same fix, larger, double vaned radiators and better insulation which is why some people are pleasantly surprised they don't need to switch radiators when moving from a modern condensing boiler setup.