OFTEC Oil Burner Types and Operation 4

Question 1

What does the term 'delayed ignition' mean in relation to oil burners?

Accepted Answer

Oil is being delivered but fails to ignite immediately, causing a build-up

Answer

Delayed ignition occurs when atomised oil enters the combustion chamber but does not ignite immediately. When it does ignite, the accumulated oil vapour causes a potentially dangerous 'puff back' or small explosion.

Question 2

What is the correct electrode gap setting typically specified for a domestic oil burner?

Accepted Answer

3-4mm between electrode tips

Answer

The standard electrode gap for most domestic oil burners is approximately 3-4mm. Too narrow a gap may cause carbon bridging, while too wide a gap may prevent spark generation. Always refer to the manufacturer's specifications.

Question 3

Why must an oil burner fan run for a pre-purge period before ignition?

Accepted Answer

To clear any residual oil vapour from the combustion chamber

Answer

The pre-purge period allows the fan to push fresh air through the combustion chamber, clearing any residual oil vapour that could cause a dangerous puff back when ignition occurs. This is a critical safety feature.

Question 4

What is the purpose of the fire valve in an oil supply system?

Accepted Answer

To automatically shut off the oil supply in the event of a fire

Answer

A fire valve is a fusible link valve installed on the oil supply line near the appliance. In a fire, the fusible link melts (typically at 68°C), closing the valve and cutting off the fuel supply to prevent the fire being fed.

Question 5

What is a common cause of oil burner short cycling?

Accepted Answer

An oversized burner or incorrect thermostat differential

Answer

Short cycling occurs when the burner fires and shuts down too frequently. Common causes include an oversized burner for the heat load, too narrow a thermostat differential, or a faulty aquastat. This reduces efficiency and increases wear.

OFTEC Practice Test

OFTEC Practice Test

OFTEC Oil Burner Types and Operation 4