How do oil boilers work? 

In principle, an oil boiler works in the same way as a gas boiler in that it uses fuel to create hot water. This hot water is then distributed to the radiators around the house and is used to create warmth. The same hot water is also supplied to the taps in the house.

The key difference between oil and gas boilers is the fuel used. Rather than being connected to a gas supply, an oil boiler is connected to an oil tank, where fuel is stored until it is needed.

Unlike conventional oil boilers, Viessmann’s oil condensing boilers come prepared for the future and reduce users’ reliance on fossil fuels. They are designed to be used with fuel oil mixed with bio-oil, which means they can be partially run on renewables. 

Do I need a new oil boiler?

YOil boilers are designed to be robust and durable. Often, they can last for up to 15 years, or even longer if they are well maintained. However, there will come a point in every oil boiler’s life when it stops functioning as it should and therefore needs to be replaced. Clearly, if your appliance stops working and can’t be fixed, you’ll need to get a new one. However, there are many other less obvious signs that you could benefit from a replacement oil boiler. These include:

  • Frequent breakdowns
  • Failing to meet the heating and hot water needs of your home
  • Unexplained rise in energy bills
  • Difficulties finding replacement parts for repairs
  • Not supporting smart technology

Does it have to be an oil condensing boiler? 

In England, Wales, Scotland and Northern Ireland, boilers need to be condensing unless your installer requests a formal exemption from OFTEC.

Condensing boilers utilise heat that would be wasted in traditional non-condensing appliances. The latent heat from the exhaust gases is extracted and re-used, making these appliances significantly more efficient than older models. In fact, Viessmann condensing oil boilers have an unbeaten high efficiency of 98 per cent relative to gross calorific value.

Who can install an oil boiler? 

If you decide to replace your current boiler and you’re looking for a specialist to complete your new oil fired boiler installation, it’s recommended to choose an OFTEC registered engineer. The OFTEC Association (which is short for the Oil Firing Technical Association) is a trade organisation that recognises competence for people who work with oil fired appliances, including boilers.

An OFTEC registered engineer is able to not only perform the installation, but also to declare it compliant with the relevant building regulations. In contrast, if you get a non-registered engineer, they will have to have their work checked by someone else to certify it.

How much does oil boiler installation cost?

The cost of an oil boiler installation will depend on a range of factors, including the complexity of the job. For example, if you will require a flue to be relocated or new pipework or extra radiators to be fitted, you can expect to pay more. Replacing a water tank will also cause the installation costs to increase, and if you need your heating system to be powerflushed, this will add to the price too.

On average, installations can cost anything from £800 to £2,000. This is for the labour and installation; you’ll also need to factor in the price of the appliance itself.

To ensure you benefit from the most competitive installation price, it’s recommended that you get quotes from a few OFTEC registered engineers.

What happens during the installation?

Simple installations can generally be completed within a day, but more complex jobs can take longer. Your engineer will be able to give you a schedule before they start work so that you know what to expect.

Good engineers will bring all the materials they need to complete the task as efficiently as possible, and they will cover your floors and surfaces as they work to protect them. They will also clean up after themselves.

Once the work is completed, they will provide you with the relevant certification for your new appliance and they will run you through the controls. Make sure you pay attention to this as it will help you to operate your new oil boiler as efficiently as possible.

How are oil boilers rated?

Oil boilers are now rated using the ErP Directive, with their performance ratings shown on energy efficiency labels just like all other heating products. For heat generators, the best efficiency class is designated with A++ and the worst with G.

Are oil boilers noisy?

We have specifically developed our boiler systems to feature a low level of operating noise. However, boiler noise levels will always vary depending on the location within your property and any other background noise.

When replacing my oil boiler, do I also need to replace my oil storage tank?

We would definitely recommend it. When you replace your oil boiler, you are not legally required to change your oil storage tank, unless installing the boiler makes the oil tank non-compliant. However, if an incident occurs and your oil storage tank does not comply with the current legislation, you could have trouble making an insurance claim..

Is an external air break required when a condensate pipe is terminated into a rainwater downpipe?

Yes, if you are using your rainwater downpipe as a termination point for your condensate pipe, it is important that an air brake is installed between the boiler’s condensate outlet and the drain pipe connection. This must be external to your property in order to avoid flooding during adverse weather conditions.

What do I need to know to maintain my new oil boiler?

Once you’ve installed a new oil boiler, you’ll no doubt want to ensure it continues to operate effectively and efficiently for as long as possible. The key to this is regular servicing. This will help to keep the appliance in excellent condition. There are other useful pieces of advice to bear in mind too. Keep reading to discover more.

Should I turn my oil boiler off when my oil tank is being filled?

Yes, whilst filling your oil tank it is always recommended that you turn your boiler off. It is also recommended that you ensure your boiler remains switched off for 30 minutes afterwards. The reason for this is to ensure any sediment from the base of the tank is not drawn into the fuel line.

How can the condensate be drained in an oil condensing boiler?

With a Viessmann oil condensing boiler, the condensate can be drained from the following places:

  • Internal stack pipe
  • Waste pipe
  • External drain
  • Rainwater hopper
  • Purpose-made soakaway

What can cause an oil boiler burner to lockout?

A lockout in the burner of your oil boiler could be caused by a leak in the pipeline. It can also happen because there is no oil or because the oil is contaminated. Contamination can occur for a number of reasons, including damage to the tank caused by condensation, sludge, water ingress or corrosion. To prevent these problems, take care of your oil tank - and replace it when necessary. Also, make sure your tank is always topped up before the fuel runs out.

We hope this oil boiler installation guide has been useful. If you would like further guidance, don’t hesitate to contact our team.

Find the perfect heating system

Looking for a new heating system?

Find the perfect system in 3 simple steps

Most read articles
Viessmann Vitodens, Gas Boiler range

Which heating system is the best for you?