OFTEC Oil Firing (OFT101/105E) key terms

The air deliberately supplied to a burner to mix with fuel oil so that complete burning can take place. It is separate from ventilation air used to dilute or remove fumes from the room.

The theoretical minimum quantity of air needed to burn a given amount of fuel completely, with no oxygen left over. Real burners always supply more than this figure to ensure clean combustion.

The extra air supplied above the theoretical requirement, usually expressed as a percentage. Too little causes smoke and carbon monoxide; too much wastes heat by carrying it up the flue.

A scale reading from a smoke pump test that grades the darkness of flue gas deposits on filter paper, typically 0 to 9. A low number indicates clean combustion; high numbers show incomplete burning.

A colourless, odourless and toxic gas produced when fuel burns with insufficient oxygen. Even small concentrations in a room are dangerous, so appliances must be checked for spillage and correct combustion.

The measurement of oxygen, carbon dioxide and temperature in the exhaust gases to assess combustion efficiency and confirm correct burner settings. Results guide adjustment of the air damper and oil pressure.

The proportion of heat released by the fuel that is usefully transferred to the system rather than lost up the flue. It is calculated from flue temperature and oxygen or carbon dioxide readings.

A light domestic heating oil with low viscosity and low sulphur, commonly used in pressure-jet burners for vaporising and room-sealed appliances. Its name comes from a standard flow test time of about 28 seconds.

A heavier heating oil than kerosene, with higher viscosity and energy content, typically used in larger commercial burners and older installations. It usually needs preheating before atomisation.

A measure of a liquid's resistance to flow. It affects how easily oil can be pumped and atomised, and it changes with temperature, so preheaters are sometimes fitted to heavier oils.

The amount of heat energy released when a unit quantity of fuel is completely burned, usually quoted in megajoules per litre or per kilogram. It is used to calculate appliance heat output and efficiency.

The lowest temperature at which a fuel gives off enough vapour to ignite briefly when a flame is applied. It is a key safety property used to classify oils for storage and handling.

The process of breaking liquid oil into a fine spray of droplets so it can mix with air and burn efficiently. Pressure-jet nozzles achieve this by forcing oil through a small orifice at high pressure.

The burner component that atomises oil into a spray pattern at a rated flow, marked by size and spray angle. A worn or blocked nozzle causes poor combustion, smoke or unreliable ignition.

The pressure at which the fuel unit delivers oil to the nozzle, usually measured in bar at a gauge port. Correct pressure is essential for the rated nozzle output and good atomisation.

The pair of metal rods that create the spark to ignite the oil spray. Their gap and position relative to the nozzle must be set to the manufacturer's specification for reliable light-up.

An electrical component that steps up mains voltage to a high potential, producing the spark across the electrodes. Failure to spark is a common cause of lockout at start-up.

A light-sensitive device that detects the presence of flame in the combustion chamber and signals the control box. If it sees no flame, or is dirty or misaligned, the burner will lock out.

The safety function that confirms a flame has established and remains present during operation. It uses a photocell or similar detector linked to the control box to shut off fuel if flame is lost.

The electronic unit that sequences the burner through pre-purge, ignition, flame establishment and running, and enforces safety lockout if any stage fails. It governs timings and safety checks automatically.

A safety state in which the control box stops the burner and holds it off after a fault such as no flame. It usually requires a manual reset before the burner can restart.

A timed period before ignition during which the fan blows air through the combustion chamber and flue to clear any unburnt fuel or gases. It reduces the risk of explosion on light-up.

A timed period after the burner shuts down during which the fan continues to run to clear residual combustion products from the appliance and flue. It helps prevent odours and corrosion.

A raised, impermeable wall or container around an oil tank that holds at least 110 percent of the tank's capacity, so any leak is contained. It protects ground and water from pollution.

The vessel that holds heating oil for the installation, made from steel or plastic and sited to allow safe filling, venting and inspection. It must meet capacity, support and secondary containment requirements.

A pipe that allows air in and out of the tank as oil is drawn or delivered, preventing pressure or vacuum build-up. It must be correctly sized, positioned and fitted with a flame arrestor where required.

The connection where a delivery tanker discharges oil into the storage tank. It must be clearly labelled, secure and positioned so spills can be seen and contained.

A device fitted in a drainage line to trap oil before water reaches a drain or watercourse. It is required where tank areas drain to surface water systems.

A safety device that shuts off the oil supply to the burner if the temperature rises excessively, typically triggered by a fusible element or remote sensor. It prevents fuel feeding a fire.

A manually operated valve for shutting off the oil supply to allow servicing or emergency isolation. It should be accessible and clearly identified for the user.

The pipework carrying oil from the storage tank to the burner, which may be a single-pipe gravity or two-pipe pumped system. It must be leak-free, correctly sized and protected from damage.

A check that confirms combustion products are being drawn safely up the flue rather than escaping into the room. It is carried out with the appliance running and any draught diverter or door disturbed.

The upward pull created by the difference in temperature and density between hot flue gases and outside air. Adequate draught removes combustion products and supports steady, safe burning.

A device that admits air into the flue to limit excessive draught, protecting the burner from unstable combustion and preventing flame lift. It is often combined with a draught diverter.

The outlet at the top or end of the flue where combustion products discharge to outside air. Its position and clearance must prevent fumes re-entering the building through windows or vents.

Fresh air admitted to the room to replace air used by the appliance and to dilute any fumes. Permanent openings must be correctly sized and kept clear to keep the appliance safe.

The process of setting up and testing a newly installed appliance and burner to confirm safe, efficient operation before handover. It includes combustion checks, safety device tests and recording results.

The stage where the completed installation is explained to the user, with documentation, operating instructions and safety information provided. Records of commissioning and any tests are passed on.

A written log of maintenance, tests and adjustments carried out on an appliance over time. It supports fault diagnosis, proves compliance and helps the next engineer work safely.