System Boilers

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Information about System Boilers

A system boiler, often referred to as a sealed system boiler, pumps hot water directly to the radiators and a sealed hot water storage cylinder. Many of the important components of the heating and hot water systems such as the pump and expansion vessel are built into a system boiler, resulting in a quicker, easier and more efficient installation process. The system boiler removes the need for a feed and expansion cistern. However, a cold water tank is still necessary (unless you have a pressured hot water cylinder).

System boilers combine high performance and convenience with exceptional 'green' credentials and are therefore an ideal choice for the modern household, which has a high demand for hot water and needs every inch of the valuable storage space.

If you're considering the installation of system boilers, GreenMatch provides you with a free of charge and with no obligation service that allows you to request quotes and compare different systems, so that you can find the most suitable for you. Just fill in the form on the right to request offers.

Types of System Boilers

There are two types of system boilers: vented and sealed system boilers. A vented system boiler requires an expansion tank in the loft, while a sealed system boiler has a built in expansion tank together with other safety controls. Both types require a hot water cylinder, however, if a sealed system boiler is combined with an unvented cylinder, there is no need for a cold-water storage tank.

What Is a System Boiler?

A system boiler heats water straight from the mains (just like a combi boiler) making it an ideal option for flats or households, where a dry roof space is required. The hot water is pumped directly from the system boiler through the heating system to the radiators and hot water cylinder, generating a fast response and reduced running costs.

By keeping the hot water in a storage tank, the system boiler can provide hot water for more than one outlet and at a higher pressure than a combi boiler. The storage of hot water in the hot water cylinder means that system boilers are less dependent on the flow of water from the cold water mains. System boilers can be used in areas where the water pressure is too low for a combi boiler to be used.

Advantages of a System Boiler

    • Suitable for larger properties with higher hot water demand. The large tank of stored hot water will allow you to use several taps at once.
    • There is no need for a feed and expansion tank in the loft.
    • The installation of a system boiler is quick, easy and efficient.

Disadvantages of a System Boiler

    • Unless the hot water cylinder is very well insulated, it generally loses heat into its surroundings, thereby wasting energy.
    •  Hot water cylinder-reliant hot water systems take up more space than, for example, a combi boiler system.
    • The amount of hot water you can use is limited by the size of your cylinder.

System Boilers Prices

System boilers prices depend greatly on its heating capacity, efficiency, fuel type etc. The system boiler is cheaper than a combi boiler but still more expensive than simply repairing your old system—installation fees are around £500-700, while the fittings would cost around  £1,000-2,500. System boilers reviews prove that they're cheaper and better. Typically the costs for sealed combustion boilers are higher than for traditional atmospherically vented boilers. Overall, cheap system boilers are highly accessible.Boiler Collage


How much will I save by installing a new system boiler?

According to the Energy Saving Trust, it is possible to save up to £310 a year by replacing an old standard efficiency boiler with system boiler. 

Is a sealed system boiler the right choice for me?

A system boiler is great for larger households or places that have several water outlets. A high hot water demand that cannot be met by a combi boiler makes the system boiler ideal option, as it does not require much space, however, it does need a tank in the airing cupboard.

Will I need a separate expansion tank in the loft of the system boiler?

There is no need for a feed and expansion cistern in the loft if you have a pressured unvented hot water cylinder. However, if you have an open vented hot water cylinder, you will need a cold water storage cistern in the loft.

Are system boilers economical to run?

A system boiler reduces the amount of time it takes for the house to heat up by pumping hot water straight to the radiators and hot water cylinder, thus minimising running costs. System boilers are also compatible with solar thermal domestic hot water systems.

What is the appropriate source of heat for a system boiler?

There are wide ranges of system boilers available for different fuel types including natural gas as well as LPG and Oil ranges that are ideal for off gas areas.

What is a condensing system boiler?

It is a legal requirement in the UK for all types of boilers to be condensing. Condensing system boilers are more energy efficient, cost-effective and environmentally friendly, as they capture and reuse some of the heat, which would escape from the flue of a non-condensing boiler. They also use less fuel and power and have lower CO2 emissions, which makes them the greener alternative.

Read more: Green Energy Grants