Flue Gas Recovery (Condensing Boilers)

A boiler's flue is the most reliable waste heat source on most sites: hot, continuous whenever the boiler fires, and concentrated in one accessible duct. A conventional boiler sends its combustion gases up the stack at 150 to 200 °C, carrying away energy that was paid for as fuel. Two measures reclaim it: an economiser recovers the sensible heat, and condensing operation goes further by reclaiming the latent heat in the flue's water vapour. This lesson covers both, their economics, and the practical catches that decide whether they work.