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Refrigeration & Air Conditioning Mechanic Red Seal · Question

Which of the following describes the most precise method to determine the combustion efficiency of a gas-fired warm air furnace?

Combustion efficiency is accurately determined by analyzing the components of the flue gas, specifically measuring the net stack temperature and either the oxyg

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Question: Which of the following describes the most precise method to determine the combustion efficiency of a gas-fired warm air furnace?

Answer options: ✅ Measuring the flue gas temperature and oxygen (O₂) or carbon dioxide (CO₂) concentration.

  • Observing the flame characteristics and colour, and the presence of any soot.
  • Comparing the gas input rating to the measured temperature rise across the heat exchanger.
  • Checking the furnace filter cleanliness and adjusting the fan speed settings.

Correct answer: Measuring the flue gas temperature and oxygen (O₂) or carbon dioxide (CO₂) concentration.

Explanation: Combustion efficiency is accurately determined by analyzing the components of the flue gas, specifically measuring the net stack temperature and either the oxygen (O₂) or carbon dioxide (CO₂) levels.

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