Oil Boilers FAQs

Our Experts Answer Your Questions


The Lowdown on Oil Boilers

How does an oil boiler work?

An oil boiler operates like a gas boiler. The oil (rather than gas) is ignited in a combustion chamber, which then heats cold water via a heat exchanger. A combi oil boiler uses water straight from the mains, while a regular boiler heats water that is stored in a tank. The hot water is piped to radiators and taps to provide central heating and hot water. The only difference between a gas boiler and an oil boiler is that the oil for an oil boiler needs to stored in a tank on your property rather than being delivered by a mains connection, as is the case with natural gas.

Does an oil boiler use electricity?

Yes. Oil-fired boilers need electricity to ignite, and to run the pumps and fans necessary to distribute the fuel and water through the heating system. Sometimes they have LED displays or controls which are also powered by electricity. The amount of electricity consumed by an oil heating system is, however, minimal.

Does running out of oil damage your boiler?

Most oil boilers have a safety mechanism which turns off the burner to protect damage if the oil runs out. If it doesn’t turn off, or in the “dry” period before it turns off automatically, the filters and fuel lines could become clogged and will need to be cleaned by an Oftec registered engineer before the boiler is restarted. Being empty can also cause problems to your oil tank. When it is empty the inside of the tank may experience condensation, meaning that when it is topped up water may mix with the oil and damage your heating system. It’s best to keep a check on your oil supply tank and not let the level fall below 12 inches before arranging a refill. 


Common Questions About Oil Boilers

Does an oil boiler heat water?

Yes. Oil-fired boilers provide hot water for both central heating systems, including radiators, and hot running water for your taps. A combi oil boiler provides hot water on demand with the water being heated as it runs through the boiler system. A conventional oil boiler will have a separate water storage tank with pipes to feed the hot water around the house to where it is required.

What happens if you don’t service your oil boiler?

Your oil boiler should be serviced by a qualified Oftec registered engineer at least once a year to check that it is safe and running efficiently and to replace the oil nozzle.. If you don’t have your oil boiler serviced the manufacturer’s warranty could become invalid; minor problems might be missed until they turn into expensive repairs; your boiler will not run fuel-efficiently, costing you more in heating oil; and your boiler may not be running safely, emitting fumes or leaking oil.

Is heating a house with oil expensive?

Oil is more expensive than gas, but if you’re not on the National Grid for a gas supply, oil-fired central heating is the best alternative cost-wise. Oil is cheaper than electricity for heating, averaging at 4.81p per kWh. Oil is a fossil fuel which emits carbon emissions, just like gas, but is thought to be a little more “green” than gas because oil boilers produce more heat for your money, with a fuel efficiency of more than 90%.


Pressing the Right Buttons

When do I need to press the reset button on my oil boiler?

Every oil boiler has a reset button, usually a red button which is there to restart the boiler if it has automatically shut off because of a fault or malfunction, or if it has been switched off accidentally. It’s unwise to try resetting the boiler yourself, unless you are sure that whatever made it turn off in the first place has been dealt with. If you do want to reset the boiler, press the reset button only once. Hold it down for a few seconds before releasing it. If the boiler doesn’t restart, call an engineer – don’t repeatedly press the reset button because it is likely to make matters worse. 

Why do I have to keep resetting my oil boiler?

If you find that you keep having to reset your oil boiler, there is most likely a fault either with the boiler itself, the heating system or the flue, which is causing your boiler to “lock out”. If your boiler is a modern, fairly new model then as well as locking out it may also be displaying a fault code on the display panel, or a flashing red light. Common causes for oil boiler lock out are a leak in the heating system; a faulty pump or electric part; low pressure; overheating; insufficient air intake from the flue; or a blocked plate heat exchanger. Whatever the cause, if you repeatedly need to reset the boiler there is a problem that requires an investigation by a qualified oil boiler technician. 

How often should you replace your boiler?

The average life for a well-maintained oil boiler is 15 years, but if you want to make sure you have a high efficiency boiler that is cheaper to run and has lower carbon emissions you should change your old oil boiler for a modern one as soon as possible. Once your boiler reaches the stage where it is having frequent breakdowns with worn parts that need replacing, it is more cost effective to replace the whole appliance than to keep having it repaired.

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