Oil boilers are less common that gas boilers, however there are over four million homes in the UK that aren’t connected to the gas main. This means that these four million homes need to be heated in other ways. An oil boiler is often the best way to do this. The oil tank can be fitted on site and filled with oil as and when it’s needed and, in most cases, can be a cheaper heating solution than electric. 

But how does an oil boiler work?

An oil boiler works in a very similar way to a gas boiler. The fuel, in this case oil, is ignited in the combustion chamber and a heat exchanger warms up cold water, either from the mains in a combi system or from a cold water tank in a conventional system. The heated water can be used in your radiators, taps and showers to provide your home with heating and hot water.

An oil boiler should reach the same efficiency as a gas boiler. According to building regulations, oil boilers must have an energy rating of at least 86 per cent, or A+. A condensing oil fired boiler will usually have an efficiency of 90 per cent or higher. Oil is a more efficient fuel than gas. This is because oil boilers use nearly all of the heat and additional gas that’s created from the burning of fuel, turning this into extra heating energy so there’s less wastage. This means you’ll get a good return on every unit of energy.

The main difference between a gas and an oil boiler is the way the appliances store their fuel. A gas boiler doesn’t need to store gas because it is connected to the mains, which means it has a constant supply of fuel. In contrast, an oil boiler requires a tank to store the oil until it is needed.

The oil tank should be located on your property and there are certain installation regulations that need to be followed. The base of the tank must be strong enough to support the weight of the tank and its contents. The tank must sit on solid ground, either concrete or paving slabs that are at least 42 mm thick and that extend out at least 300 mm beyond the perimeter of the tank. If the tank is located quite close to your house, a fire wall must be positioned between the tank and your home. 

The tank should have an automatic shut off valve installed, which would prevent a fire in the boiler from spreading to the tank. This would be extremely dangerous and could result in a fire in your oil tank.

Modern oil tanks are usually made of plastic and are relatively easy to maintain. The tank will need to be refueled as necessary to ensure that you don’t run out of oil at any point. Some people will only need the tank to be refilled once a year, however for larger homes with more radiators, you may find that the tank has to be refilled a couple of times each winter.

Just like in a gas heating system, your home should have at least one thermostat that tells you the room temperature. This thermostat should be placed away from a radiator and out of direct sunlight so it is providing an accurate measurement. The thermostat and the boiler should be wired in an interlock. This will prevent the boiler from continuing to heat your home after the set temperature has been reached. Your radiators should all have thermostatic radiator valves as an additional way to control the heat in your home.

Can I use diesel in my oil boiler?

There are two types of oil you can use to fuel your boiler: red diesel and kerosene.

Red diesel is the same as the diesel that we put in our cars, however it is dyed red to show that it isn’t being used for road vehicles. Fuel that’s used for road vehicles is taxed differently to fuel that is used for other purposes. For example, a farm with lots of equipment could use red diesel as long as their vehicles aren’t driving on public roads. So a tractor would most likely need white diesel whilst a combine harvester that only drives on privately owned land could use red diesel.

Technically, you could put diesel in your tank that you’ve purchased from a petrol station, however you will pay much more for that diesel than you would for reduced-tax red diesel. Red diesel is also known as 35-second oil or gas oil.

The other kind of oil used to power boilers is kerosene, otherwise known as 28-second or heating oil. The second measurement refers to the thickness of the oil. Oil was originally measured by the time it takes for a ball bearing to pass through a set distance of the oil. This means that kerosene isn’t as viscous as diesel. Kerosene is the most popular type of heating oil in the UK because it’s more efficient than diesel.

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How to clean an oil fired boiler

Just like any other heating system, an oil boiler will need cleaning to ensure there isn’t any dust, soot or debris present that could be reducing its efficiency.

If you want your boiler to have a thorough clean, you should get a suitably qualified engineer to do this for you. They will be able to check the condensate drain, clean the siphon and clean the combustion chamber/heat exchanger surfaces.

You shouldn’t try to remove the boiler casing yourself in order to clean it. This should only be done by an OFTEC registered engineer, otherwise your warranty may be void. 

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