Combustion Efficiency Testing Flashcards

What is the theoretical maximum CO2 reading for the complete combustion of kerosene?

Answer: 15.2%

The stoichiometric (theoretical maximum) CO2 for complete combustion of kerosene with zero excess air is approximately 15.2%. In practice, some excess air is always needed for safe combustion, so 10-12% is the target range.

What happens to combustion efficiency if the burner air band is opened too far?

Answer: Efficiency drops because excess air carries heat up the flue

Opening the air band too far admits excessive combustion air. This extra air absorbs heat from the combustion process and carries it up the flue, reducing the overall combustion efficiency of the appliance.

How is the efficiency of a condensing oil boiler measured differently from a conventional boiler?

Answer: It must account for latent heat recovery from condensing water vapour in the flue gases

Condensing boilers recover latent heat from water vapour in flue gases. Efficiency is calculated on either a gross or net calorific value basis. Net CV efficiency can exceed 100% because it includes recovered latent heat that gross CV does not.

What safety action should a technician take if they detect CO levels above 100 ppm in the room?

Answer: Immediately shut down the appliance, ventilate the room, and warn occupants

Room CO levels above 100 ppm represent an immediate danger to life. The appliance must be shut down, the area ventilated by opening windows and doors, occupants warned, and the source of CO identified before any further operation.

What does the term 'stoichiometric combustion' mean in relation to oil burner efficiency?

Answer: The theoretically perfect combustion with exactly the right amount of air for complete fuel burning

Stoichiometric combustion is the theoretically ideal process where exactly the correct amount of oxygen is provided to completely combust all the fuel. In practice, this is unachievable and some excess air is always needed for safe operation.

Why is it important to record combustion test results on the service report?

Answer: To provide a benchmark for comparison at future services and evidence of safe operation

Recording results provides a documented history of the appliance's performance. Trends can be identified (e.g., gradually increasing CO or smoke) and results serve as evidence that the appliance was left in safe, efficient condition.