Mixed Deck — All OFTEC Topics Flashcards

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

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

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.

What is the net flue gas temperature and why is it important?

Answer: Flue gas temperature minus room temperature — it indicates how much heat is being lost

Net flue gas temperature is calculated by subtracting the ambient room temperature from the measured flue gas temperature. This figure is used with the CO2 reading to calculate combustion efficiency and assess heat losses.

What is the maximum penalty for causing oil pollution to controlled waters?

Answer: An unlimited fine and/or imprisonment

Pollution of controlled waters is a criminal offence. Penalties include unlimited fines and/or imprisonment. Additionally, the polluter can be liable for the full cost of clean-up operations, which can run to hundreds of thousands of pounds.

What does excess air in combustion mean for boiler efficiency?

Answer: It reduces efficiency as heat is wasted heating unused air that goes up the flue

Excess air beyond what is needed for combustion absorbs heat as it passes through the boiler and carries that heat up the flue. While some excess air is necessary for safe combustion, too much wastes energy.

What does a high oxygen (O2) reading in the flue gas indicate?

Answer: Too much excess air is entering the combustion process

High O2 readings (above 6-7% for kerosene) indicate excessive air entering the combustion zone. This lowers CO2, reduces efficiency, and may cause flame instability. The air band or damper needs adjusting.

What is the environmental benefit of installing a condensing oil boiler versus a non-condensing model?

Answer: It uses less fuel for the same heat output, reducing both CO2 emissions and running costs

Condensing oil boilers are 10-15% more efficient than non-condensing models, meaning less fuel is burned to produce the same heat. This directly reduces CO2 emissions (by the same percentage) and lowers fuel costs for the householder.

What is a benchmark commissioning checklist used for in oil heating?

Answer: To record a standardised set of commissioning tests and results that prove the installation is safe and compliant

The benchmark checklist provides a standardised format for recording all commissioning tests, measurements, and settings. It proves the installation was properly commissioned and provides a baseline for future service comparisons.

What is the OFTEC technician's responsibility regarding oil spillage on site?

Answer: To contain the spill, prevent it reaching drains or watercourses, and clean up using absorbent materials

Any oil spill must be immediately contained using absorbent materials or barriers to prevent it reaching drains, watercourses, or soaking into the ground. The contaminated absorbent must then be disposed of as controlled waste.

What is a Smoke Control Area and how does it affect oil-fired appliances?

Answer: A designated area where smoke emissions are restricted — oil appliances must burn cleanly

In Smoke Control Areas, it is an offence to emit smoke from a chimney. Oil-fired appliances are generally exempt provided they burn approved fuel (kerosene or gas oil) and are properly maintained to avoid producing smoke.

What size permanent air vent is typically required for a conventional flue oil boiler?

Answer: 550mm² per kW of rated input over 5kW

For conventional flue oil appliances, a permanent air vent of 550mm² per kW of rated input above 5kW net is typically required. This ensures adequate combustion air supply. The vent must be non-closable and positioned to avoid draughts.

What safety device must be tested during the commissioning of an oil-fired boiler?

Answer: The overheat thermostat (limit stat) must be tested to confirm it shuts down the burner

The overheat thermostat (high-limit or limit stat) is a critical safety device that shuts down the burner if the boiler water temperature exceeds a safe limit (typically 90-100°C). It must be tested to ensure it operates correctly.

What is bio-oil (FAME/HVO) and why is it relevant to oil heating's environmental impact?

Answer: A renewable fuel that can replace or blend with kerosene to reduce carbon emissions

Bio-oil (such as HVO — Hydrotreated Vegetable Oil) is a renewable liquid fuel that can be blended with or replace kerosene in oil boilers. It significantly reduces net carbon emissions and is part of the UK's strategy to decarbonise off-grid heating.

What is the minimum separation distance for an oil flue terminal from an opening window?

Answer: 600mm from any openable window, air vent, or other opening

An oil flue terminal must be at least 600mm from any openable window, air vent, or other building opening to prevent combustion products from re-entering the building. Greater distances apply for terminals below openings.

Under the Oil Storage Regulations, what is the trigger point for mandatory secondary containment in domestic properties in England?

Answer: Tanks over 2,500 litres in specified locations, or any tank where there is a pollution risk

In England, domestic oil storage requires secondary containment where the tank is over 2,500 litres or where there is a risk of oil reaching controlled waters. Building Regulations also impose bunding requirements based on location and risk.

What component converts 240V mains supply to the high voltage needed for the ignition electrodes?

Answer: The ignition transformer

The ignition transformer steps up the 240V mains supply to approximately 10,000V to create a spark between the electrodes. Some modern burners use electronic ignition modules instead of traditional transformers.

When is a remote fill point required for an oil storage tank?

Answer: When the tank cannot be safely accessed by the delivery tanker within the 30m hose length

A remote fill point is installed when the delivery tanker cannot park within 30 metres of the tank or cannot safely access the tank directly. The remote fill pipe runs from the accessible fill point to the tank connection.

What is the correct procedure for priming an oil burner after the system has run out of fuel?

Answer: Loosen the bleed screw on the pump, run the burner to expel air, then tighten when oil flows steadily

After refuelling, air must be bled from the oil supply line. Loosen the bleed screw on the fuel pump, operate the burner (it will lockout), and air will be expelled. When pure oil flows from the bleed screw, tighten it and reset the burner.

What is the purpose of a flue liner in a masonry chimney used for an oil-fired appliance?

Answer: To protect the chimney from corrosive combustion products and ensure gas-tight integrity

A flue liner (typically flexible stainless steel) protects the masonry from acidic condensates in oil flue gases. It also ensures the flue is gas-tight and correctly sized for the appliance, preventing leakage and improving draught.

What is the role of the Energy Performance Certificate (EPC) in relation to oil-fired heating?

Answer: It rates the energy efficiency of a property, and the heating system type significantly affects the rating

EPCs rate a property's overall energy efficiency. Oil-fired heating typically receives a lower rating than gas or heat pump systems due to higher carbon emissions. The efficiency of the boiler and controls directly affects the property's EPC rating.

Why is it important to measure the flue gas temperature during combustion testing?

Answer: High flue gas temperature indicates heat is being lost up the flue, reducing efficiency

Flue gas temperature, combined with room temperature, gives the net flue gas temperature. High readings (above 250-300°C) indicate the heat exchanger may be fouled or the appliance is operating inefficiently, with usable heat being lost.