OFTEC Combustion Efficiency Testing 1 — Questions and Answers
Question 1: What is the primary instrument used to measure combustion efficiency on an oil-fired appliance?
- Electronic flue gas analyser (Correct answer)
- Manometer
- Multimeter
- Thermographic camera
Correct answer: Electronic flue gas analyser
An electronic flue gas analyser measures CO, CO2, O2, flue gas temperature, and calculates combustion efficiency. It is the essential tool for commissioning and servicing oil-fired appliances to OFTEC standards.
Question 2: What is the recommended CO2 reading for a kerosene pressure jet burner operating correctly?
- 10-12% (Correct answer)
- 3-5%
- 15-18%
- 20-25%
Correct answer: 10-12%
A correctly adjusted kerosene pressure jet burner should produce CO2 readings of 10-12%. Below 10% indicates excess air (wasting heat), while above 12% indicates insufficient air (risk of CO production).
Question 3: What is the maximum acceptable CO reading in the undiluted flue gas for an oil-fired appliance?
- 50 ppm (Correct answer)
- 200 ppm
- 500 ppm
- 1000 ppm
Correct answer: 50 ppm
The maximum acceptable CO reading is 50 ppm in undiluted flue gas. Readings above this indicate incomplete combustion and potential danger. The appliance should be adjusted or taken out of service if this cannot be achieved.
Question 4: What does a smoke number of 0 on the Bacharach scale indicate?
- Clean combustion with no visible smoke or soot (Correct answer)
- Maximum smoke output
- The test was not performed correctly
- The filter paper was faulty
Correct answer: Clean combustion with no visible smoke or soot
A Bacharach smoke number of 0 indicates clean, complete combustion with no measurable soot. For kerosene burners, the target is a smoke number of 0. For gas oil, a reading of 0-1 is acceptable.
Question 5: What is the Bacharach smoke test used to measure?
- The level of soot particles in the flue gases (Correct answer)
- The temperature of the flue gases
- The oxygen content of the flue gases
- The draught in the flue
Correct answer: The level of soot particles in the flue gases
The Bacharach smoke test draws a measured volume of flue gas through a filter paper. The resulting soot stain is compared against a numbered scale (0-9) to assess the level of incomplete combustion.
Question 6: Why is it important to measure the flue gas temperature during combustion testing?
- High flue gas temperature indicates heat is being lost up the flue, reducing efficiency (Correct answer)
- It determines the CO content
- It measures the draught
- It indicates the fuel flow rate
Correct answer: High flue gas temperature indicates heat is being lost up the flue, reducing efficiency
Flue gas temperature, combined with room temperature, gives the net flue gas temperature. High readings (above 250-300°C) indicate the heat exchanger may be fouled or the appliance is operating inefficiently, with usable heat being lost.
OFTEC Combustion Efficiency Testing 1
What is the primary instrument used to measure combustion efficiency on an oil-fired appliance?