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  • System Boiler Replacement

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  • System Boiler Replacement

    Updated: February 27, 2024

    System boilers are ideal for homes that have a high hot water demand. Getting a system boiler replacement might involve different tasks. The complexity of the job will differ for each home. 

    Why should you replace your system boiler?

    Condensing technology has become a standard legal regulation for all modern boilers since 2005. As a result, new system boilers use condensing technology. Non-condensing boilers can be less efficient. In fact, they are 30% less efficient than modern condensing boilers. Old boilers are less efficient because heat energy can be lost when it escapes out of the flue pipe. 

    With the use of condensing technology, this extra heat will be captured and used to provide additional energy. So a condensing boiler will use less fuel to produce the same amount of heat. Your boiler will reach an efficiency rate of 92 to 99%.

    Older boilers that use condensing technology can lose their efficiency over time. In this case, getting a boiler replacement has the protection of saving you money on your energy bills. 

    Other signs that indicate a need for boiler replacement include your boiler not being able to provide sufficient hot water or heating or that it requires frequent maintenance and repairs. Constant repairs can be costly and in that case, it might be more cost-effective to get a new boiler. 

    Keep in mind that your energy bills can rise due to having an inefficient system boiler. This issue can be easily prevented by simply getting a boiler replacement. 

    What are the benefits of replacing an old system boiler?

    There are many benefits of replacing your old boiler. These can include more comfort and optimal heating. You will also make use of modern technology that comes with newer boiler generations. 

    If you notice any signs indicating that your boiler is unsafe, then you should switch it off and make sure to have it checked by a Gas Safe Engineer who is licensed without delay. An important sign would be if you smell gas. 

    When should I replace my system boiler?

    Modern boilers can last as long as 10 to 15 years. Some boilers can last for 20 years but they will be prone to having various issues and their efficiency will decrease in time. In some cases getting a new boiler is more cost-effective than expensive repairs. 

    What to consider before replacing a system boiler

    After it has been decided that you need to replace your boiler, you would need to think of what the installation includes based on your current heating system. 

    Less time and effort will be required if it is a like-for-like boiler swap. Let’s say that you are replacing your system boiler with another system boiler. This can also save you money on Installation cost. This will be possible because other parts such as the pipes and the hot water cylinder will remain in their place and only the boiler unit will need to be installed. 

    System Boiler Replacement
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    Replacing your regular boiler with a system boiler

    Additional work will be needed when replacing a regular boiler with a system boiler. This work will include removing the cold water feed tank from your loft and, without a doubt, additional pipework. Although these tasks may cost extra, it’s a good investment in the long run. System boiler can meet with a high level of hot water demand, maintain high water pressure and save you some space in your home. 

    However, before deciding to replace your regular boiler with a system boiler, it’s better to consult a heating engineer to see if your pipework and radiators can withstand the high water pressure of a system boiler. 

    Replacing your combi boiler with a system boiler

    When replacing your combi boiler with a system boiler you will need a hot water cylinder. So make sure that you have the space required for the cylinder in your home before going ahead with your plans. 

    Keep in mind that a combi boiler cannot support more than one bathroom at the same time. If you have more than one shower or tap turned on at the same time, you might get low water pressure with a combi boiler. That being said, there are some combi boiler types that can support more than one bathroom but these will consume more energy. 

    In conclusion, a system boiler is more suitable for medium and large homes with multiple bathrooms because of its ability to store hot water in a hot water cylinder. 

    How much does a new system boiler cost?

    A new system boiler can cost between £500 – £1,500. And some premium models can cost up to £2,800.

    Which system boiler should I get?

    In order to get the system boiler that suits your home best, you will need to estimate the energy demand of your home. After that you would just match it with the required boiler according to the boiler’s size, measured in (kW) kilowatts. 

    It is of importance to get this right so that you wouldn’t waste energy by using an oversized boiler or a boiler that is insufficient and can meet your hot water demand. 

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    Output size of your system boiler

    You will be able to estimate the size of the boiler you need by the number of radiators you have in your home. 

    Number of radiatorsOutput size
    10 radiators9-18 kW
    15 radiators18-26 kW
    Over 20 radiators 27-40 kW

    Which hot water cylinder should I get?

    Copper or stainless steel are usually used to make hot water cylinders. Generally speaking, water cylinders need to be replaced after 8-12 years. The benefit of having a hot water cylinder is that it can store hot water which is ready to be used even when you have multiple outlets running at the same time. In short, you don’t need to wait for the water to heat. 

    As for the capacity of your hot water cylinder, it will depend on the size of your home. Hot water cylinders can store between 120-300 litres of water.

    Types types of cylinders are available. These are vented and unvented. They differ in the manner in which the water is fed into the tank and where the water comes from. Vented cylinders take their water by depending on gravity from a cold water tank that is usually placed in the loft of your home. 

    System boilers use unvented cylinders which are fed water from the mains water supply directly. That is why system boilers do not need a cold water tank. It is preferable that you use a system boiler if you live in an area with high water pressure so that you can make the best of your system boiler.


    Are system boilers suitable for large homes?

    System boilers are very convenient in large homes with high demand for hot water. 

    Are system boilers efficient?

    Yes, they are. System boilers can reach an efficiency rate of 94%. 

    What is the difference between a regular and a system boiler?

    System boilers don’t need as much space as regular boilers because they only require space for the boiler and the hot water cylinder. On the other hand, a regular boiler requires a cold water tank. In conclusion, system boilers can save you some space and due to having less part they will require less maintenance.

    Do system boilers use gas or electricity?

    System boilers have a heat exchanger that can provide hot water for your home. This heat exchanger takes its energy from burning fuel. With an electric system boiler, an electric element is used for heating the water.