Oil Boiler Service: How It Differs From a Gas Boiler Service

An oil boiler should be serviced once a year, the same as a gas boiler, but the service is carried out by an oil technician, usually one registered with OFTEC, not by a Gas Safe engineer. Gas Safe registration covers natural gas and LPG (see how an LPG boiler service differs from a mains gas one). It does not cover oil-fired appliances. An oil service also involves work a gas service does not, such as replacing the burner nozzle, changing the oil filter and checking the tank and supply line. We service gas boilers. If yours runs on oil, this guide explains what to ask for, so you book the right person.

Who Can Service an Oil Boiler?

An oil boiler should be serviced by a technician trained and registered for oil-fired equipment. OFTEC is the main registration scheme for oil heating technicians in England and Wales.

This is the most common mistake people make when booking. A Gas Safe registered engineer is qualified for gas work, and that registration says nothing about oil. Some firms employ engineers qualified for both, but you should check the individual engineer's oil registration rather than assume. If you are asking a company for a quote, tell them the fuel type at the start, as well as the make and model of the boiler.

How Do You Know Your Boiler Runs on Oil?

If you have an oil tank on the property and no gas meter, your boiler almost certainly runs on oil. Oil boilers are uncommon in London, where most homes are on the gas network, but they do exist in properties on the edges of Greater London that are not connected to mains gas.

Other clues are a louder burner when the boiler fires up, a fuel line running from the tank to the boiler, and the boiler's data badge, which states the fuel. If you have moved into a property and are unsure, the previous service record or the installation paperwork will say.

What an Oil Boiler Service Covers

An oil service covers the burner, the combustion process and the fuel supply. The main parts of the work are:

• Burner nozzle. The nozzle that sprays oil into the combustion chamber is normally replaced at each service, because wear affects how cleanly the oil burns.
• Oil filter. The filter on the supply line is changed or cleaned so debris from the tank does not reach the burner.
• Burner head, electrodes and fan. These are cleaned and set up so ignition is reliable.
• Heat exchanger and combustion chamber. Soot and deposits are cleaned out. Oil produces more soot than gas, so this matters more than on a gas boiler.
• Combustion test. A flue gas analyser confirms the boiler is burning safely and efficiently, and the burner is adjusted if needed.
• Flue, seals and safety controls. These are checked in the same spirit as a gas service, including the fire valve that cuts off the oil supply if there is a fire.

You should receive a written service record at the end, just as you would for a gas boiler. Most manufacturers need an unbroken annual service history to keep a warranty valid, whatever the fuel.

The Oil Tank Is Part of the Job

A good oil service includes a look at the tank and the supply line, not just the boiler. Problems with the tank are one of the most common causes of breakdowns on oil systems.

The technician will look for water and sludge in the tank, which can block the filter and nozzle, and check the tank, its base and the supply pipe for damage, corrosion or leaks. An oil leak is an environmental problem as well as a heating one, so any sign of weeping or staining around the tank or pipe should be raised straight away. On older single-skin tanks, the technician may advise you on the tank's condition and whether it is reaching the end of its life.

How an Oil Service Differs From a Gas Service

The two services share the same aim, safe and efficient combustion, but the work is different. A gas service rarely involves replacing parts as routine. An oil service almost always does.

Because the nozzle and filter are consumable parts, an oil service tends to take longer than a gas service on a similar boiler, and the price will reflect the parts as well as the time. An oil boiler also relies on the fuel supply you manage yourself, so running the tank very low can draw sludge into the system and cause a breakdown that a gas boiler owner would never see. Carbon monoxide is a risk with oil as well as gas, so a carbon monoxide alarm in the room with the boiler is sensible, and for landlords in England it is a legal requirement. Our guide to carbon monoxide warning signs applies to both fuels.

Oil Boiler Service Plans

Service plans for oil boilers exist, but many plans are written for gas boilers only. Before signing up, confirm in writing that the plan covers oil-fired boilers and that the engineers who will visit are registered for oil work.

It is also worth asking whether routine consumables such as the nozzle and filter are included in the annual service, whether the plan covers the tank and supply line or only the boiler, and what happens if a breakdown turns out to be caused by the fuel supply. Our boiler service plan comparison guide sets out the general questions to ask any provider. The same questions apply to oil, with the fuel check added first.

Landlords With Oil Heating

There is no oil equivalent of the gas safety record in law, but landlords are still responsible for keeping heating and hot water installations in repair and in proper working order. An annual oil service with a written record is the clearest evidence that you are doing that.

If a rented property has both oil heating and a gas appliance, such as an LPG or mains gas hob, the gas appliance still needs an annual gas safety check by a Gas Safe registered engineer. In that case you will need two different engineers, or one who holds both registrations. If your boiler runs on gas, you can send us the make and model and we will arrange the service.