@gemlog @FaithfullJohn I have a house with a back boiler, there's a tank of water in the chimney and heat from the coal fire can be directed to it to heat the hot water and radiators. I'm less familiar with this setup, with a full range, but presumably it's similar, there's a tank in the chimney that gets heated by the fire? I've boosted your question as I'm sure someone will know how a range works