Oil boiler servicing

Why oil boilers need this more than gas boilers do

Gas arrives at the burner already clean. Oil does not. Kerosene is a liquid fuel that has to be atomised into a fine mist by a nozzle with an orifice measured in thousandths of an inch, then ignited by two electrodes sitting a couple of millimetres apart in a blast tube. Everything in that chain degrades: the nozzle erodes and its spray pattern widens, the electrodes pit and their gap opens up, the photocell that proves the flame gets a film of soot on it, and the fuel itself drops sediment and water into the tank, which the filters then have to catch.

The result is that an oil boiler drifts out of tune in a way a gas boiler largely does not. It will keep working while it drifts, which is exactly the problem – the boiler still lights, the house still gets warm, and nothing obvious tells you that the burner is now running rich, sooting up the heat exchanger and quietly costing you ten or fifteen per cent more fuel than it did a year ago. By the time it actually locks out, the combustion chamber has usually been carbonising for months.

This is also why an annual service on oil is not really comparable to an annual service on gas, and why the two should not be priced as though they are the same piece of work. On oil, the burner physically comes out of the boiler.

What we actually do on the day

A service that follows the OFTEC procedure takes a reasonable amount of time, and most of it is spent on the burner bench rather than standing next to the boiler.

1. Check it before touching itWe run the boiler from cold and take a combustion reading before any cleaning, because the ‘before’ figure tells you how the boiler has actually been running for the last year. Cleaning first and only measuring afterwards hides the evidence.
2. Isolate, and pull the burnerElectrical isolation, fuel isolation at the tank valve, then the burner comes off the boiler and onto a sheet. Nothing is cleaned in situ.
3. Renew the nozzleNew nozzle every service, correct size and spray angle for that appliance. Nozzles are not cleaned and refitted – the orifice is machined and once it has eroded, no amount of cleaning restores the spray pattern.
4. Set electrodes and check the pumpElectrode gap and position reset to the manufacturer’s figures with a gauge, not by eye. Pump pressure checked against a gauge on the pressure port and adjusted to the appliance data plate.
5. Clean the combustion chamber and fluewaysBaffles out, chamber brushed and vacuumed, flueways cleared. This is the dirty half-hour that determines whether the boiler transfers heat into your water or sends it up the flue.
6. Both filtersTank-side filter and the burner filter. Changing one and not the other is common and it is not a service.
7. Flue and safety checksFlue integrity, terminal position, seals, fire valve operation, and the condition of the oil line and any flexible connections.
8. Recommission and analyseBurner refitted, boiler run to temperature, then smoke test and a full combustion analysis with a calibrated analyser – CO2 or O2, flue gas temperature, net efficiency and CO.

What the readings tell you

Most people never see these figures, which is a shame, because they are the most useful thing about the whole visit. They are not difficult to interpret once somebody explains them.

Keeping the tickets in a drawer gives you something genuinely valuable: a trend. A boiler whose flue gas temperature has climbed steadily over four services is telling you something about its heat exchanger that no single visit would reveal.

When a service turns into a repair

Sometimes we open a boiler up and find something that a service will not fix. We will tell you on the day, with the part in our hand, and we will tell you whether it needs doing now or whether it will see out another winter.

• Perished combustion chamber – the chamber lining in an older appliance breaks down and starts to crumble. Repairable on some models, terminal on others.
• Baffles that have warped or corroded through – usually a sign the boiler has been running badly for years.
• A pump that will not hold pressure – common on higher-hours appliances, and a fairly routine replacement.
• A photocell or control box fault – often the real cause behind a boiler that has been intermittently locking out.
• Water in the fuel – the filter bowl tells you immediately. That is a tank problem, not a boiler problem, and cleaning the filter alone just buys a few weeks.

We would rather have an awkward conversation in October than an emergency call-out in January. If a boiler is genuinely near the end, we will say so plainly, and we will not push a replacement you do not need.

Servicing and your warranty

Every oil boiler manufacturer makes the warranty conditional on an annual service by a competent person, with the service record completed. Miss a year and you can find a five- or seven-year warranty has quietly evaporated at the point you most need it. Keep the paperwork, and keep it with the appliance rather than in an email you will not be able to find.

The same applies if you are letting the property out. There is no statutory oil equivalent of the landlord gas safety certificate, but an oil-fired rental with no service history is a liability, and most letting agents and insurers will ask for the record.

Where we do this

Oil boiler servicing is the largest single part of what we do, and it is why we built the business around oil rather than treating it as a sideline. Norfolk has one of the highest concentrations of off-grid properties in the country, and a lot of those homes are on their third or fourth oil boiler.

We cover Norwich and the surrounding villages routinely, and the rest of Norfolk on planned days. See the areas we cover, or read what actually happens during a service in more detail.