🔍 Key Concepts

• How unwanted excess air entering a boiler (not through the burners) affects heat transfer and combustion efficiency • Relationship between stack temperature and boiler efficiency • What is meant by boiler panting and whether air leaks in casings are a common cause

💭 Think About

• Think about what happens to the hot flue gases when cool outside air leaks into the gas path around the boiler • Consider whether extra air entering where it is NOT controlled by the burner improves or worsens the combustion process • Ask yourself which option fits the idea of heat being carried away the fastest from the boiler surfaces

✅ Before You Answer

• Verify whether cool air mixing with hot gases will raise or lower gas temperature at the stack • Consider if air leaks around casings directly affect combustion quality in the furnace or mainly the gas path after combustion • Check which option best matches the overall effect on heat transfer to the water/steam vs heat lost up the stack