The Grant Vortex Pro external models combine our existing proven condensing boiler technology with the latest Riello RDB low NOx compact burner. The Vortex Pro External modules offer a factory fitted multi-directional flue, high quality external powder coated casing, built in frost protection, mains isolating switch and a test switch. The range has some of the highest energy efficiency ratings in the UK which not only significantly lowers fuel bills but also considerably reduces greenhouse gas emissions and lessens the environmental impact of domestic hot water and heating systems.