OFTEC Oil Firing (OFT101/105E) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Kerosene flash point

Kerosene has a flash point above 38 °C, classifying it as Class C2. It is not highly flammable but its vapour can ignite at the burner under the right conditions.

Stoichiometric air requirement

Complete combustion of kerosene requires approximately 14.4 kg of air per kg of fuel, equivalent to about 12 cubic metres of air per litre of kerosene.

Target CO2 pressure jet

A correctly set domestic pressure jet burner typically produces 11.5-12.5% CO2 in the flue gas, with a smoke number of 0-1 on the Bacharach scale.

Nozzle flow rating

Nozzle flow is rated in US gallons per hour at 7 bar (100 psi). Actual flow varies approximately with the square root of the pump pressure ratio.

Electrode gap setting

Pressure jet electrodes are typically set with a 3-4 mm gap and tips positioned 2-3 mm forward of the nozzle face, per the manufacturer's gauge.

Photocell function

The photocell (cad cell) detects flame presence. Its resistance is high in darkness and falls when flame is detected, proving combustion to the control box.

Control box lockout time

On flame failure the control box locks out after a safety time, typically 5-15 seconds, shutting the oil solenoid and requiring manual reset.

Fire valve operation

A fire valve closes the oil supply on temperature rise, using either a fusible head (about 90 °C) or a capillary sensor located above the burner.

Bund capacity requirement

Where oil storage regulations apply, a bund or secondary containment must hold 110% of the largest tank's capacity, or 110% of the total where tanks share a bund.

Tank outlet height

The tank draw-off outlet should be at least 100 mm above the tank base so that water and sludge settle below the outlet and are not drawn into the line.

Flue terminal clearance

A flue terminal must be at least 600 mm from an opening window and clear of combustible materials, with exact clearances taken from the manufacturer's instructions.

Chimney termination height

Under Part J a chimney should terminate at least 2.3 m above a flat roof or 0.6 m above the ridge of a pitched roof, per the applicable diagram.

Draught stabiliser purpose

A barometric draught stabiliser maintains constant flue draught where natural draught varies or exceeds the manufacturer's limit, preventing excess air and efficiency loss.

Condensate trap requirement

Oil condensing boilers need a condensate drain of at least 22 mm with a trap giving a water seal, typically 75 mm, plus frost protection for the discharge.

Sealed system components

A sealed heating system requires an expansion vessel, a pressure relief valve typically set at 3 bar, a pressure gauge, and a filling loop.

Annual service scope

An annual oil service includes cleaning the heat exchanger, baffles, burner head, electrodes and photocell, plus replacing the nozzle and recording combustion readings.

Nozzle replacement rule

The nozzle must be replaced at every service and never cleaned and refitted, because the precision spray pattern cannot be restored once worn or blocked.

Lockout fault causes

Common lockout causes include air in the oil line, incorrect electrode gap, a dirty photocell, a faulty control box, or loss of oil supply.

Water in oil symptom

Water contamination in the tank causes flame pulsation and repeated lockout. Drain water from the tank bottom and check the oil filter for water.

Combustion efficiency factors

Combustion efficiency is derived from flue gas temperature and CO2 or O2. A 20 °C reduction in flue temperature improves efficiency by roughly 1%.

Air-free CO measurement

Air-free CO corrects the measured CO for excess air and is the true indicator of incomplete combustion; a well-set pressure jet should be below 100 ppm.

Two-pipe oil supply

A two-pipe system returns surplus oil to the tank and is used where the tank outlet is below the burner or suction lift is marginal.

Single-pipe bypass plug

A single-pipe supply requires a bypass plug fitted in the pump so surplus oil recirculates internally; it is used where lift is within the pump's limits.

Pressure jet atomisation

A pressure jet burner atomises fuel at 7-14 bar through a nozzle; domestic pumps are commonly set at 8-10 bar depending on the nozzle specification.

Vaporising burner fuel

Vaporising (pot) burners rely on heat to vaporise fuel at atmospheric pressure and must use kerosene; gas oil will not vaporise reliably and causes coking.

Combustion air ventilation

Open-flue oil appliances require permanent high and low level ventilation sized to the appliance input per BS 5410 and the manufacturer's instructions.

Overheat thermostat

The overheat (limit) thermostat is manual reset and set above the control thermostat; it interrupts the burner on overheat and must not be bypassed.

Electrical supply requirement

Oil appliances are typically supplied via a fused spur with a 3 A fuse and a double-pole isolator, wired to BS 7671 with RCD protection where required.

COSHH fuel requirement

COSHH requires a risk assessment and safety data sheets for fuel and chemicals used on site, with suitable controls and PPE specified for handling.

Manual handling drum weight

A 205-litre drum of kerosene weighs roughly 170-180 kg, so mechanical assistance or a two-person lift is required for handling.

Commissioning sequence

Commissioning order: pre-check installation, fill and vent the oil line, set pump pressure, adjust air for CO2 and smoke, then measure CO and flue temperature.

Handover documentation

Handover must include the commissioning certificate, benchmark or checklist, user instructions, fuel type, servicing schedule, and building control notification.