OFTEC Oil Firing (OFT101/105E) cheat sheet

COSHH applies to oil, kerosene fume, and combustion products; safety data sheets must be available before handling fuel.

Kerosene (Class C2) flash point is above 38 °C; it is not classified as highly flammable but vapour can still ignite at the burner.

Confined-space entry for tanks or flues requires a permit, atmospheric testing (O2, CO, flammable gas) and a rescue plan.

Manual handling: a 205-litre drum of kerosene weighs roughly 170-180 kg; two-person or mechanical handling is required.

Fuel oil can cause dermatitis; nitrile gloves and eye protection are minimum PPE for burner and nozzle work.

Isolate and lock off electrical supply before opening burner or control panel; prove dead with a tester.

Carbon monoxide is odourless; never commission or service a combustion appliance in a poorly ventilated space without a working CO alarm and personal monitor.

Reportable incidents under RIDDOR include specified injuries, over-7-day absences, and dangerous occurrences such as fires or explosions.

Building Regulations Part J (England and Wales) covers combustion appliances, oil storage, flues and ventilation; equivalent requirements apply in Scotland and Northern Ireland.

OFTEC registration covers three scopes: OFT101 (domestic pressure jet), OFT105E (domestic vaporising), plus tank installation and commissioning/ servicing where held.

BS 5410-1 covers domestic oil firing installation and maintenance; BS 5410-2 covers commercial/industrial.

Work on oil storage must comply with the Control of Pollution (Oil Storage) Regulations where applicable (England, Scotland, Wales, NI thresholds differ).

Gas Safety style notification does not apply to oil, but building control notification is required for controlled work such as replacing a boiler or installing a new flue.

Competent person self-certification schemes (e.g. OFTEC) allow registered businesses to notify controlled work without separate building control application.

Manufacturer's instructions must be followed; deviation requires documented justification and must not reduce safety.

The Pressure Systems Safety Regulations apply to pressure jet burners only where the fuel pump/pressure system falls in scope; domestic burner pumps are typically exempt but must be maintained.

Single-skin domestic tanks require a bund or secondary containment of 110% of tank capacity where oil storage regulations apply.

Tank base must be non-combustible, level, and capable of supporting the full tank weight (kerosene ~0.82 kg/litre).

Minimum separation from a non-fire-rated boundary is 1.8 m for tanks up to 3500 litres; fire-rated walls allow reduced separation.

Tank outlet should be at least 100 mm above the base to allow sludge and water to settle below the draw-off point.

Fill point must be within sight of the delivery hose and fitted with a lockable cap, overfill prevention and a label stating fuel type and capacity.

Vent pipe sizing: typically 50 mm minimum for domestic tanks, terminating with a flame arrestor and turned down, above flood level.

Tanks should be sited to allow inspection of all sides and access for filling; sight gauge or contents indicator must be visible.

Plastic tanks must be protected from UV degradation and supported across their full base; steel tanks require internal and external corrosion protection.

Kerosene (C2, 28-second oil) calorific value approx 46.2 MJ/kg; gas oil (C1, 35-second oil) approx 45.5 MJ/kg.

Kerosene density approx 0.82 kg/litre at 15 °C; gas oil approx 0.85 kg/litre.

Viscosity determines atomisation: kerosene ~1.5-2.5 cSt at 40 °C, gas oil ~3-6 cSt; preheaters are used for heavier grades.

Two-pipe (return) supply is used where the tank outlet is below the burner or where lift is marginal; single-pipe uses a bypass plug in the pump.

Oil line should be continuously rising from tank to burner where possible to allow air to vent back to tank.

Maximum suction lift for a single-stage pump is typically around 3.5 m with a two-pipe system; consult pump data for exact limits.

Pipework should be in annealed copper or approved plastic-coated steel, protected from mechanical damage, with accessible isolation valve at the tank.

Fire valve: a fusible-head or capillary fire valve must be fitted, with the sensor located above the burner and the valve closing on temperature rise (typically 90-95 °C).

Pressure jet burners atomise fuel at 7-14 bar through a nozzle; vaporising (pot) burners rely on heat to vaporise kerosene at atmospheric pressure.

Vaporising burners are kerosene-only; gas oil will not vaporise reliably and causes coking.

Pressure jet boilers are typically rated 15-70 kW domestic; output is set by nozzle size, pump pressure and combustion air.

Heat exchanger materials: cast iron for conventional boilers, stainless steel or aluminium for condensing; condensing boilers recover latent heat below dew point (~55 °C return).

Vaporising appliances include range cookers, room heaters and some small boilers; they require a natural draught flue and constant level oil control.

Combustion chamber and baffles must be correctly positioned; missing or misplaced baffles reduce efficiency and raise flue gas temperature.

Balanced-flue and room-sealed oil appliances take combustion air directly from outside, reducing ventilation requirements.

Oil-fired condensing boilers require a condensate drain with a trap and frost protection; the plume must be sited away from windows and boundaries.

Stoichiometric combustion of kerosene: approx 14.4 kg air per kg fuel (about 12 m³ air per litre of kerosene).

CO2 in flue gas indicates excess air: typical pressure jet target 11.5-12.5% CO2, vaporising 9-11%.

Smoke number target for pressure jet is 0-1 (Bacharach scale); anything above 2 indicates poor atomisation or air imbalance.

Flue gas temperature for non-condensing oil boilers typically 180-250 °C; high temperature with low CO2 suggests excess air or fouled heat exchanger.

CO should be below 100 ppm (air-free) for a well-set pressure jet appliance; rising CO with falling CO2 suggests air starvation or blocked flue.

Excess air (lambda) of 1.15-1.25 gives clean combustion with acceptable efficiency for pressure jet burners.

Flame colour: correct pressure jet flame is orange-yellow with a bright incandescent core; a smoky or long lazy flame indicates under-aeration or worn nozzle.

Combustion efficiency is calculated from flue temperature and CO2/O2; a 20 °C reduction in flue temperature improves efficiency by roughly 1%.

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

Nozzle spray angles: 60° for narrow chambers, 80° for most domestic boilers, 45° for wide/low chambers; hollow cone for pressure jet boilers.

Electrode gap typically 3-4 mm with tips 2-3 mm forward of the nozzle face; incorrect gap causes ignition failure or delayed ignition.

Pump pressure adjustment via pressure regulator screw; typical domestic setting 8-10 bar (higher for some nozzles).

Photocell (cad cell) detects flame; it must be clean and correctly aligned, with resistance falling when flame is present.

Solenoid valve on the pump controls oil supply; it opens on demand and closes on shutdown to prevent after-drip.

Blast tube and turbulator/air swirl plate position must match the manufacturer's dimensions; incorrect insertion depth affects flame shape.

Combustion air damper setting is adjusted with a CO2/smoke test to achieve the specified CO2 and smoke number at the correct draught.

Boiler must be mounted on a non-combustible base, level, with manufacturer's clearances to combustible materials maintained.

System design: sealed systems require expansion vessel, pressure relief valve (typically 3 bar), and filling loop; open vented systems require feed and expansion tank.

Pipe sizing for heating circuits based on flow rate and allowable pressure drop; typically 0.5-1.0 m/s velocity for domestic.

Oil line isolation valve must be accessible and labelled; fire valve must be fitted upstream of the burner and operate independently of the electrical supply.

Condensing boilers require a condensate drain of at least 22 mm ID with a trap providing a water seal (typically 75 mm) and frost protection.

System must be flushed and inhibited before commissioning; sludge and flux residues cause premature failure and block heat exchangers.

Boiler house/compartment ventilation: high and low level openings sized to manufacturer's requirements; typically free area based on appliance output.

Electrical supply to the appliance must be via a double-pole isolator with a 3 A fuse (or as specified) and RCD protection where required.

Flue draught for natural draught oil appliances typically 0.05-0.15 mbar (5-15 Pa) measured at the test point.

Chimney/flue must terminate above roof level per Part J: typically 2.3 m above a flat roof or 0.6 m above the ridge of a pitched roof.

Flue terminal must be at least 600 mm from an opening window, and clear of combustible materials and boundaries per manufacturer.

Flue must be suitable for the fuel and appliance type: stainless steel or vitreous enamel for conventional, plastic or approved condensing flue for condensing.

Combustion air: open-flue appliances require permanent ventilation; typical domestic requirement is based on kW input plus a fixed allowance (consult BS 5410).

Draught stabiliser (barometric damper) maintains constant draught; must be fitted where flue draught varies or exceeds manufacturer's limit.

Flue must be swept and inspected; a blocked flue causes CO rise and flame failure. Flue integrity test with smoke pellet confirms draught and no leakage.

Room-sealed/balanced flue terminals must be sited to avoid recirculation of products and comply with manufacturer's terminal clearances.

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

Oil line must be bled at the pump until clear bubble-free oil flows before attempting ignition.

Combustion analysis: record CO2, O2, CO, flue temperature, smoke number, and draught; compare to manufacturer's data.

Nozzle output verification: measure oil flow over a timed period (e.g. 1 minute) at set pressure to confirm rated output.

Handover pack: installation/commissioning certificate, benchmark/checklist, user instructions, fuel type, and servicing schedule.

Building control notification or competent person self-certification must be completed and copy provided to the customer.

Electrical checks: polarity, earth continuity, RCD trip test, and correct fuse rating at the isolator.

Record all settings (nozzle size, pump pressure, CO2, smoke number) on the appliance/service label and in documentation.

Service interval for oil appliances is typically annual; includes cleaning heat exchanger, baffles, burner head, electrodes, photocell and nozzle replacement.

Nozzle should be replaced at every service; never clean and refit, as the spray pattern cannot be restored.

Common faults: no ignition (electrodes, transformer, photocell), lockout (photocell dirty, flame failure, air in line), pulsating flame (water in oil, incorrect nozzle, air).

Lockout on start-up: check oil supply, electrode gap, photocell cleanliness, and control box reset - do not repeatedly reset without finding cause.

Smoky flame: check nozzle size/type, pump pressure, air damper setting, and flue/combustion air blockage.

Water in tank causes flame pulsation and lockout; draw off from tank bottom and check for water in filter.

Combustion analysis before and after service demonstrates improvement and confirms safe operation; record results.

Fault finding sequence: verify electrical supply and controls, then oil supply and pressure, then ignition components, then combustion settings.

Control box sequence: pre-purge (fan and air), ignition, oil valve open, flame proven by photocell, then run; on flame failure, lockout after safety time (typically 5-15 s).

Photocell resistance: high (dark) = high resistance; low resistance when flame detected; check with meter and clean lens.

Fire valve types: fusible head (operates at ~90 °C) and capillary (remote sensor); must be wired to close oil supply independent of electrical power.

Overheat thermostat (limit stat) on boiler must be manual reset and set above the control thermostat; it interrupts the burner on overheat.

Wiring must comply with BS 7671; oil appliances typically supplied via a fused spur with 3 A fuse and double-pole isolation.

Safety devices must not be bypassed; any bypass found must be corrected and recorded as a defect.

Solenoid valve and photocell circuits are low voltage on many burners; check control box terminal diagram for correct connections.

Annual electrical checks include earth continuity, insulation resistance, and functional test of overheat stat, fire valve and lockout.

COSHH assessment required for all chemicals used (fuel, cleaning agents, inhibitors); safety data sheets on site.

Personal protective equipment: nitrile gloves, eye protection, and suitable footwear for fuel handling and servicing.

Working at height for flue terminals and tank inspection: use ladders safely, three points of contact, or scaffold for extended work.

Electrical safety: isolate and prove dead before work; use RCD-protected tools where required.

Fire precautions: no smoking, no naked flames, extinguisher suitable for fuel fires (foam/dry powder) available.

Waste oil and contaminated materials must be disposed of via licensed waste carrier with waste transfer note.

Report accidents and dangerous occurrences per RIDDOR; keep accident book.

Lone working: risk assessment, communication plan, and first aid arrangements must be in place.

Building Regulations Part J requires notification for replacement appliances and new flues; competent person schemes allow self-certification.

BS 5410-1 is the primary installation standard for domestic oil firing; BS 5410-2 for commercial.

Oil Storage Regulations apply in England (above 200 litres at most premises), Scotland (above 200 litres), Wales and NI with different thresholds.

Manufacturer's instructions are the primary source for appliance-specific settings and clearances.

OFTEC registration requires periodic assessment and continuing professional development.

Waste transfer and disposal of oil-contaminated waste must comply with environmental legislation.

Electrical installation must comply with BS 7671 (IET Wiring Regulations).

Gas/oil interlock and notification requirements apply where multiple fuels are present.

Bund capacity must be 110% of the largest tank's capacity where multiple tanks share a bund.

Tank must be sited on a base extending at least 300 mm beyond the tank footprint and impermeable to oil.

Fill point and vent must be sited so spillage does not enter drains or watercourses; drip tray under fill point recommended.

Tank labelling: fuel type, capacity, and 'No smoking' / 'Flammable' signage.

Inspection: check for corrosion, splits, bund integrity, and clear sight gauge at each service visit.

Pipework from tank to appliance should be protected and not buried without protection; use approved sleeving where passing through walls.

Tank replacement requires disposal of old tank via licensed waste contractor and notification where applicable.

Plastic tanks have a limited design life; check manufacturer's guidance and inspect for UV degradation.

Kerosene is the standard domestic fuel; gas oil (35-second) is used in some larger or commercial appliances.

Fuel oil must be clean and water-free; filters should be fitted at tank outlet and at burner.

Pipework should be sized to maintain adequate flow at the burner; undersized pipe causes pressure loss and air ingress.

Two-pipe system returns surplus oil to tank; single-pipe requires bypass plug and is used where lift is within pump limits.

Fire valve must be fitted at the tank or where pipe enters the building, with sensor above the burner.

Oil line should be pressure-tested after installation; typically 10 bar for 10 minutes on pressure systems, or as specified.

Copper pipe must be protected from contact with mortar/cement which causes corrosion; use sleeving.

De-aeration: air in oil line causes lockout; bleed at pump and check for loose connections.

Pressure jet burner components: pump, nozzle, electrodes, transformer, photocell, control box, blast tube, fan, air damper.

Vaporising burner components: constant level valve, wick or pot, carburettor, flame ring, and natural draught flue.

Condensing boilers require a condensate trap and drain; the plume is visible and must be sited per manufacturer.

Boiler output must match heat loss; oversizing causes short cycling and reduced efficiency.

Heat exchanger cleaning restores efficiency; soot deposits act as insulation and raise flue temperature.

Baffles must be refitted in correct order after cleaning; incorrect fitting causes hot spots and efficiency loss.

Combustion chamber insulation (if fitted) must be intact; damaged insulation affects flame and efficiency.

Appliance data plate gives model, output, fuel type, nozzle size, and pump pressure - always check before servicing.

Air-free CO measurement corrects for excess air and is the true indicator of incomplete combustion.

CO2 reading falls with excess air; a rising CO2 with falling O2 indicates reducing excess air.

Smoke pump (Bacharach) test: draw flue gas through filter paper and compare stain to scale 0-9.

Flue draught measured with a manometer at the appliance test point; too much draught cools the flue and reduces efficiency.

Combustion efficiency tables use flue temperature and CO2 (or O2) to derive efficiency; typical domestic target 85-90% net for non-condensing.

Incomplete combustion produces CO; causes include air starvation, blocked flue, incorrect nozzle, and flame impingement.

Excess air increases stack losses; too little air produces CO and smoke - aim for the manufacturer's CO2 with smoke 0-1.

Ambient CO testing around the appliance confirms no products escaping into the room.

Nozzle markings: flow rate (gph), spray angle (e.g. 80°), and spray pattern (hollow/solid).

Pump pressure gauge fitted at pump test point; adjust to manufacturer's specification (commonly 8-10 bar domestic).

Electrode position: tips set to manufacturer's gauge; typically 3-4 mm gap and 2-3 mm ahead of nozzle.

Photocell must be clean and aligned with flame; test by covering and confirming lockout.

Air damper adjustment affects CO2 and smoke; set after pump pressure and nozzle are correct.

Turbulator/air swirl position affects flame shape; set per manufacturer's dimension from blast tube.

Ignition transformer output typically 10-12 kV; check for spark at electrodes with tester.

Solenoid valve and pump coupling must be secure; loose coupling causes erratic oil supply.

Boiler clearances to combustibles per manufacturer; typically 50-100 mm sides, more at front for access.

Sealed system components: expansion vessel pre-charge, pressure relief valve, and pressure gauge.

Condensate drain must fall continuously to a suitable discharge point; trap must be primed.

System flush and inhibitor required before commissioning; record inhibitor concentration.

Oil line fire valve and isolation valve must be accessible and labelled.

Electrical supply: double-pole isolator, correct fuse, and RCD where required.

Ventilation openings must be permanent and not obstructed; size per manufacturer and BS 5410.

Commissioning certificate and handover documentation must be completed and given to the customer.

Flue terminal clearances: 600 mm from openings, 300 mm from combustible materials (check manufacturer).

Chimney height: minimum per Part J; typically 2.3 m above flat roof or 0.6 m above ridge.

Draught stabiliser fitted where flue draught exceeds manufacturer's limit; maintains constant draught.

Flue integrity test: smoke pellet confirms draught and no leakage; visual inspection of joints.

Combustion air openings sized for appliance input; high and low level where required.

Room-sealed appliances take air directly; terminal must avoid recirculation.

Flue must be swept and inspected at service; soot and debris cause CO and efficiency loss.

Condensing flue must be suitable for wet products; plastic or approved stainless.

Bleed oil line at pump until bubble-free before ignition.

Set pump pressure and nozzle per manufacturer; verify output by timed flow measurement.

Adjust air for correct CO2 and smoke number; record readings.

Measure CO, flue temperature, and draught; compare to manufacturer's data.

Electrical checks: polarity, earth continuity, RCD trip, fuse rating.

Complete commissioning certificate and service label; record all settings.

Handover: user instructions, fuel type, servicing schedule, and notification.

Demonstrate safe operation and explain controls to the customer.

Annual service: clean heat exchanger, baffles, burner head, electrodes, photocell; replace nozzle.

Nozzle replacement every service; never clean and refit.

Lockout causes: oil supply, electrode gap, photocell, control box, air in line.

Smoky flame: nozzle, pump pressure, air damper, flue blockage.

Water in oil causes pulsation and lockout; drain tank and check filter.

Combustion analysis before and after service to confirm improvement.

Fault sequence: electrical, oil supply, ignition, combustion settings.

Record defects and advise customer; do not leave unsafe appliance in operation.

Control box sequence: pre-purge, ignition, oil valve, flame proven, run; lockout on failure.

Photocell resistance changes with flame; clean and test.

Fire valve: fusible head or capillary; closes oil supply on temperature rise.

Overheat thermostat: manual reset, interrupts burner on overheat.

Wiring per BS 7671; fused spur with 3 A fuse and double-pole isolation.

Never bypass safety devices; correct and record any bypass found.

Check control box terminal diagram for correct connections.

Annual electrical checks: earth continuity, insulation resistance, functional tests.

COSHH assessment for fuel and chemicals; safety data sheets on site.

PPE: nitrile gloves, eye protection, suitable footwear.

Working at height: safe ladder use or scaffold for extended work.

Electrical safety: isolate and prove dead; RCD-protected tools.

Fire precautions: extinguisher suitable for fuel fires; no smoking.

Waste oil disposal via licensed carrier with waste transfer note.

RIDDOR reporting for accidents and dangerous occurrences.

Lone working risk assessment and communication plan.

Part J requires notification for replacement appliances and new flues; competent person self-certification.

BS 5410-1 domestic; BS 5410-2 commercial.

Oil Storage Regulations thresholds differ by nation.

Manufacturer's instructions primary for settings and clearances.

OFTEC registration requires periodic assessment and CPD.

Waste transfer and disposal per environmental legislation.

Electrical installation per BS 7671.

Multi-fuel interlock and notification requirements.

Bund 110% of largest tank where multiple tanks share.

Base extends 300 mm beyond tank footprint, impermeable.

Fill point and vent sited to avoid drains/watercourses; drip tray.

Labelling: fuel type, capacity, flammable signage.

Inspection: corrosion, splits, bund integrity, sight gauge.

Pipework protected and sleeved through walls.

Tank replacement via licensed waste contractor and notification.

Plastic tank design life and UV inspection.

Kerosene standard domestic; gas oil for larger/commercial.

Fuel must be clean and water-free; filters at tank and burner.

Pipe sizing to maintain flow; undersized causes pressure loss and air.

Two-pipe returns surplus; single-pipe with bypass plug within lift limits.

Fire valve at tank or entry point, sensor above burner.

Pressure test oil line after installation.

Copper protected from mortar/cement; use sleeving.

Bleed at pump; check for loose connections.

Pressure jet components: pump, nozzle, electrodes, transformer, photocell, control box, blast tube, fan, damper.

Vaporising components: constant level valve, wick/pot, carburettor, flame ring, natural draught flue.

Condensing requires condensate trap and drain; plume siting per manufacturer.

Output match to heat loss; oversizing causes short cycling.

Heat exchanger cleaning restores efficiency; soot insulates.

Baffles refitted in correct order.

Combustion chamber insulation intact.

Data plate gives model, output, fuel, nozzle, pressure.

Air-free CO corrects for excess air; true incomplete combustion indicator.

CO2 falls with excess air; rising CO2 with falling O2 indicates reducing excess air.

Smoke pump test: stain compared to 0-9 scale.

Flue draught measured with manometer; too much cools flue.

Efficiency from flue temperature and CO2/O2; target 85-90% net non-condensing.

Incomplete combustion causes: air starvation, blocked flue, wrong nozzle, impingement.

Excess air increases stack losses; too little causes CO and smoke.

Ambient CO test confirms no escape into room.

Nozzle markings: flow (gph), angle, pattern.

Pump pressure gauge at test point; 8-10 bar domestic typical.

Electrode gap 3-4 mm, tips 2-3 mm ahead of nozzle.

Photocell clean and aligned; test by covering for lockout.

Air damper set after pressure and nozzle correct.

Turbulator position per manufacturer's dimension.

Transformer output 10-12 kV; check spark.

Solenoid and coupling secure; loose causes erratic supply.

Clearances to combustibles per manufacturer; access at front.

Sealed system: expansion vessel, PRV, pressure gauge.

Condensate drain falls continuously; trap primed.

Flush and inhibitor before commissioning; record concentration.

Fire valve and isolation valve accessible and labelled.

Electrical: double-pole isolator, correct fuse, RCD.

Ventilation permanent and unobstructed per BS 5410.

Commissioning certificate and handover documentation.

Terminal clearances: 600 mm openings, 300 mm combustibles (check manufacturer).

Chimney height per Part J: 2.3 m flat roof, 0.6 m above ridge.

Draught stabiliser where draught exceeds limit.

Smoke pellet test for draught and leakage.

Combustion air openings per input; high and low level.

Room-sealed terminal avoids recirculation.

Sweep and inspect flue at service.

Condensing flue suitable for wet products.

Bleed oil line bubble-free before ignition.

Set pressure and nozzle; verify output by timed flow.

Adjust air for CO2 and smoke; record.

Measure CO, flue temperature, draught.

Electrical checks: polarity, earth, RCD, fuse.

Complete certificate and service label.

Handover instructions, fuel, schedule, notification.

Demonstrate safe operation to customer.

Annual service: clean heat exchanger, baffles, burner, electrodes, photocell; replace nozzle.

Nozzle replaced every service.

Lockout causes: oil supply, electrode gap, photocell, control box, air.

Smoky flame: nozzle, pressure, damper, flue.

Water in oil: pulsation and lockout; drain and filter.

Combustion analysis before/after service.

Fault sequence: electrical, oil, ignition, combustion.

Record defects; do not leave unsafe appliance.

Control sequence: pre-purge, ignition, oil valve, flame proven, run; lockout on failure.

Photocell resistance changes with flame; clean and test.

Fire valve: fusible or capillary; closes oil on temperature rise.

Overheat thermostat manual reset; interrupts burner.

BS 7671 wiring; fused spur 3 A, double-pole isolation.

Never bypass safety devices; correct and record.

Check control box terminal diagram.

Annual checks: earth, insulation, functional tests.