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What is a System Boiler?

systm boiler diagram

With so many different boilers on the market it can be a minefield to know which one is best suited to your home and lifestyle. However, before you even start to consider which are the best brands, you need to be sure you’ve identified the right type of boiler for your home. Here we explore the features and benefits of a System boiler over both a Regular (Conventional) and more modern Combi boiler.

For more information on choosing the right type of boiler for your home, be sure to visit our Boiler Buying Guide.

What is a System Boiler?

To really explain the key features of a System boiler we need to talk about Regular and Combi boilers too.

Regular Boilers

A Regular boiler is also referred to as Conventional or Traditional because it is the oldest heating system of the three. A Regular boiler requires a large feed and expansion tank to be stored in the attic. This tank is filled with cold water from the mains; this water is then fed down to the boiler which is usually installed downstairs. This is because the pressure of the water flow relies on gravity so the higher the elevation of the tank the better the flow of water from your taps. The Regular boiler will heat this water and send it through pipes to your radiators. The feed and expansion tank will also provide water for a hot water storage cylinder (usually kept in an airing cupboard) which will heat the water for your taps.

Combi Boilers

A Combi boiler is the most recent invention of the three types of boiler. It is an all-in-one unit which takes its water supply directly from the mains and produces hot water on demand for both heating and taps. For this reason it doesn’t require either a feed and expansion tank or a hot water cylinder.

System boilers feature aspects of both a Regular boiler and a Combi. Like a Regular boiler, a System boiler needs a hot water storage cylinder to heat and store hot water for your taps. It doesn’t, however, need a feed and expansion tank in the attic as – like a Combi boiler – it takes its water supply directly from the mains.

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Is a System boiler the right choice for your home?

It’s important to seek professional advice when deciding which boiler is best suited to your requirements. In general, a System boiler is a good choice if you have a large home with multiple bathrooms and several outlets needing hot water simultaneously. If you are replacing a Regular boiler with a System boiler you will be able to remove the large tank in the attic and free up some space but it will still meet a high hot water demand. A Combi boiler will also mean you can remove the hot water tank and hot water cylinder, but it will not meet a high demand for hot water.

Remember, always seek advice from a professional and arrange for more than just one quote so you can compare prices.


Advantages of System Boilers

Faster response & lower running costs

A System boiler will provide a faster response to demand than a Regular boiler as the water is supplied at mains pressure and only has to travel through the boiler and hot water tank. This should also result in reduced running costs.

Easier installation

Installing a System boiler is simpler than installing a Regular boiler as all the components are built into the unit. A simpler installation should be quicker and therefore cheaper in terms of trade hours paid for. Arguably, a System boiler’s more compact design is more attractive than a Regular boiler.

High hot water demand

A System boiler incorporates a large tank of stored hot water which means it can supply multiple outlets at once without losing pressure. This is not the case with a Combi boiler which has to split the flow to meet a high level of demand making pressure weaker. This makes a System boiler perfect for larger households with multiple bathrooms and lots of inhabitants.

No need for a cold water feed tank

There’s no need for a feed and expansion tank which saves a huge amount of space in your attic and, if you don’t have an attic, means you can still install a heating system to meet high demand. This also reduces the likelihood of leakages as the fewer components to the system the less there is to develop faults.

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Things to consider…

System boilers need more space

While their lack of a feed tank means they take up less space than a Regular system, the System boiler itself tends to be larger as it includes the expansion vessel, filling loop and pump within it. Also, a System heating setup is bulkier than a Combi as it requires a hot water tank.

Hot water cylinder

Make sure the hot water cylinder is the right size for your needs. A cylinder that is too small will not be able to meet hot water demand and a cylinder that is too big will mean you have to use extra energy and spend more money on heating water you do not need. The hot water storage cylinders should be insulated to prevent heat loss and energy wastage. This is relatively easy and inexpensive to do.

The Best System Boilers

Vaillant System Boilers

Vaillant is a global heating corporation operating in over 20 countries including the UK. Despite their worldwide presence they remain a family-owned company and have been a leading presence in the heating industry for over 140 years. Today the company’s core business is designing and manufacturing high quality heating, cooling and air conditioning solutions for both domestic and commercial settings.

Vaillant’s range of gas fired domestic System boilers includes their ecoTEC Green iQ 627 which has several energy saving features such as a modulation range of up to 1:10, an extra-condensate heat exchanger. The boiler itself is also 85% recyclable at the end of its life.

Other System boilers by Vaillant include the ecoTEC plus and the ecoFIT pure, both of which are available in a range of sizes from 12kW to 37kW. These boilers are A rated with ErP efficiency of at least 89% and come with a 2 year warranty as standard. This warranty is extended to 7 years when the boiler is installed by a Vaillant registered engineer and a 10 year warranty is also available to purchase. Vaillant also manufacture high output boilers of 46kW and 65kW which are suitable for both domestic and commercial installation.

Worcester Bosch System Boilers

From a Worcester based company producing oil fired heating equipment in 1962 to the international Worcester Bosch Group of today, this company has become synonymous with heating solutions. They produce a range of leading oil fired and gas fired boilers for both domestic and commercial use. Worcester Bosch boilers are ErP rated A and include standard warranties of between 2-5 years with a 10 year warranty available in some cases.

Worcester Bosch gas fired boilers include the Greenstar i which is their standard, compact fit unit for domestic installations available in a range of outputs between 9-24kW. For homes with a higher demand they also offer this compact, kitchen cupboard fit model in 27kW and 30kW. Larger homes with an even higher hot water demand may be better served by the Greenstar CDi Classic which is available in 30kW or 35kW. The largest gas fired system boiler is the GB162 which is suitable for commercial settings (and some of the largest homes) with output choices of 50kW and 65kW.

If you’re looking for an oil fired boiler the Greenstar Danesmoor System range by Worcester Bosch is available in three output choices: 12/18, 18/25, 25/32kW. In addition to the standard model for kitchen installation they also offer a model for utility and external siting.

Baxi System Boilers

Baxi Heating have been designing and producing boilers in the UK since 1866. Today the company is part of the BDR Thermea Group which operates in over 70 countries across the globe. The company focuses on sustainable, smart climate and sanitary hot water solutions including a range of high efficiency, easy to maintain and reliable gas boilers.

Baxi offer two System boiler ranges: the EcoBlue System and the MegaFlo System. Both are ErP rated A with minimum efficiency levels of 88% and both include a free 7 year warranty as standard. The key difference lies in their dimensions as the EcoBlue is compact enough to be installed in a 300mm deep cupboard while a MegaFlo is slightly larger. The EcoBlue is available in outputs of 12-32kW while the smallest MegaFlo output is 15kW.

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Cost of System Boilers

The price of a System boiler will usually fall between £800 and £2,500. However, depending on brand and size, this could be as much as £3,400 for the largest outputs. You will also need to factor in the cost of the hot water cylinder (if you do not have one already) and the installation.

It’s a very good idea to compare multiple quotes for installation from both leading national companies like British Gas and independent installers. Websites like Boiler Guide can source free, no obligation quotes for you to help you compare the prices and services on offer.

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