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Mistral Boiler Service & Maintenance

Rob Wells
By: Rob Wells
Updated: 9th December 2021

With the right care and maintenance a Mistral boiler could heat your home for 10-15 years and the simplest way to get the most out of your boiler is by arranging an annual service.

An annual boiler service by a qualified engineer will ensure that your boiler is running safely, efficiently and could bring any potential faults to the attention of a professional before developing into something more serious.

Is your oil boiler due a service?



What is a boiler service?

A boiler service is an all-over check of the unit to make sure that it's operating the way that it should do – safely and efficiently.

They should only be done by a qualified heating engineer which means that engineers servicing a gas boiler should be Gas Safe registered and oil boilers should be serviced by an engineer with OFTEC registration.

As Mistral boilers use oil, the engineer carrying out the service should be registered with OFTEC. You can find a list of OFTEC registered technicians on the OFTEC website but you should also check to see their credentials when they arrive at your property to carry out the oil boiler service. A typical oil boiler service takes around 30 minutes but this could be longer depending on the type of boiler you have and whether the engineer discovers any issues with the unit.

Boiler service checklist

Once you've seen that the engineer has the qualifications to conduct the service, there will be a series of operational, efficiency and safety checks.

  1. The engineer will begin by checking the boiler over for corrosion, any indication that the unit has been leaking.
  2. The heat exchanger, burner, main injector, safety devices and spark probe all require cleaning, which means taking off the casing and getting to the inside of the boiler.
  3. It's then important for the engineer to inspect the flue terminals which will ensure that it's been fitted correctly and that there's nothing blocking the terminals. As part of these checks, the engineer will also see that the seals, water and pipework are all intact.
  4. A pressure reading will be taken and the flow settings will be checked.
  5. To end, the engineer will fire up the boiler to observe it in operation and see if any parts need to be repaired.

Here are some of the key things an OFTEC engineer will be checking during an oil boiler service:

  • Too much smoke or partially burnt fuel can lead to a build up of soot on the heat exchanger which restricts how much heat is passed to water. A clean heat exchanger means a more efficient boiler.
  • The oil nozzle controls how much oil passes through the burner. Nozzles wear out as the boiler ages which will affect both efficiency as too much fuel may be passing through the boiler and can also affect the boiler's ability to operate as too much oil can cause a build up of soot on the heat exchanger.
  • Photocells are a safety feature in oil boilers which detect when the boiler is lit. Photocells can become dirty over time and won't be able to tell if the boiler is lit or not. If an oil boiler is turning itself on and off for no reason this may be the cause.
  • Electrodes are the components which produce the spark which ignites the oil. Electrodes will age and attract soot meaning that the boiler may not light.

In addition to the boiler, your oil storage tank also need to be checked for signs of water contamination, oil leaks or filter elements which may need cleaning or replacing.

You'll be given a boiler service report once the service has been completed, which provides you with details of everything that the engineer did during the service. This is your opportunity to ask the engineer any questions you might have before they leave.

Is your oil boiler due a service?



Why it’s important to service your Mistral boiler


The safety of your home is obviously at the utmost importance, which makes an annual boiler service incredibly important. Arranging a boiler service for your oil boiler will bring any existing or potential faults to the attention of a professional before they get any worse.

One of the big threats to safety when it comes to poorly operating boilers is a carbon monoxide leak. Carbon monoxide is a colourless and odourless gas that can cause serious health issues and even death if it goes undetected.

Keep heating bills low

Boilers lose their efficiency over time which can mean that your heating bill could start to rise. However, thanks to an annual boiler service, the engineer will ensure that the boiler runs as its most efficient for as long as possible.

Prevent breakdowns

A breakdown is the last thing you want so getting an engineer to spot a potential fault ahead of it turning into a major problem could save you from having to fork out for a large repair bill.


Throughout the warranty period, you're covered by the manufacturer if there's an issue with the boiler. Mistral boilers come with a 2 year warranty on the parts and 5 years on the heat exchanger as standard but to keep this valid, the boiler must be serviced annually by an OFTEC registered engineer. Should a 12 month period pass without a boiler service then the warranty will become void.

Mistral boiler service costs

An average boiler service will come to a total of £60 – £120 but depending on where you live, the type of boiler and the engineer you hire, the total price will vary.

If you're looking to save money on an annual service, we recommend arranging one during the summer when engineers aren't as busy. Getting your boiler serviced when the weather is warmer means that you can be confident it's ready to heat your home when the temperature drops in winter.

NEVER attempt to carry out an oil boiler service yourself. Always hire an OFTEC registered engineer.

Is your oil boiler due a service?



Boiler service plans

Rather than paying a set fee for a boiler service, you can take out a boiler service plan which involves paying a fixed monthly fee for a period of 12 months. During the 12 months, you'll be covered for any repairs as well as a boiler service.

This is a great idea if your boiler warranty has come to an end as you can still have the peace of mind that you're covered. Should you boiler still be under warranty then you'll be better off paying the boiler service fee each year, rather than taking out a boiler service plan.

Boiler maintenance

There's no need to wait a year until the next service to make sure that your boiler is running efficiently, you can do the following yourself.

Insulate the pipes

Insulating your pipes will help to prevent them from freezing during the winter months when they're at their most vulnerable. This is a major concern because it can lead to the boiler pressure increasing, leaks or a boiler breakdown. When insulating the pipes do so with lagging – mineral or glass wool, polyethylene or foam.

Watch the pressure

Checking that the boiler pressure isn't too low or too high is a simple check to make as it simply involves taking a look at the pressure gauge. When taking a reading, you should ideally see the needle pointing somewhere between 1 and 1.5 bar. Anything lower than 1 and the boiler pressure is too low which can prevent the boiler from operating as it should. On the other hand, a high boiler pressure could cause the boiler to stop working altogether.


Your boiler will have to work much harder to reach the desired central heating temperature if heat is escaping through window seals for example.

Annual service

While you can do a lot to help your boiler operate safely and efficiently, it will only get you so far. Only doing the above is not enough and should always be in addition to an annual service. You can get a free quote for your next boiler service by letting us know you’re looking for a local heating engineer. We’ll take care of the rest.

Back to the main Mistral page.

Rob Wells

About the author

Rob Wells

Rob is another of our resident home heating experts. He manages our external partnerships, making sure you get the most up to date information.

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