Hot water central heating boiler - has smoke jacket round waterways traversed by part of flue gases to increase efficiency

摘要

The boiler has a smoke pipe with a branch taken from this to a jacket round the waterways of the boiler. An outer insulated jacket surrounds the smoke jacket. The gases flowing through the jacket are returned by a fan to the main flue outlet. They give up additional heat to the water and are cooled to a temp. only just above the dew point. This increases the efficiency of heat extraction from the fuel without causing condesation. It also reduces radiation losses from the outer jacket. The fan keeps the additional flue gas pass below ambient pressure so that if any joints are not tight air is pulled in but no gas can leak out.