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    Installing central heating and boilers


    Summary: Advice for installing central heating and boilers, comparing the different types of boilers, combination (or 'combi' boilers), system boilers and open vent boilers.



    Choosing a heating system with a high efficiency condensing boiler with the correct heating controls can make a huge difference to your heating bills over time.

    The type of boiler you need will depend on a number of factors, such as the size of your house and your hot water requirements.


    Different types of boiler

    There are different types of boiler:

    • Combination boilers (or combi boilers) - heat water instantaneously on opening a hot tap, so there is no need for a storage cylinder.
    • System boilers - these are designed to generate heat for your home as well as hot water that can be stored in a separate hot water storage cylinder. This can be situated anywhere in your home with no need for a separate tank in the loft.
    • Heat only boilers - work in conjunction with a hot water storage cylinder and cold water top up tanks to provide both central heating and hot water.

    The role of the boiler

    Most of us are familiar with the main parts of a central heating system: the boiler, the radiators and the piping that connects it all. The boiler heats the water and this is usually circulated through the pipework and radiators by a pump, before returning to the boiler. From this basic arrangement a number of different systems and boilers have been developed; below you'll find a guide to the 3 types most commonly found in British homes.


    What is a condensing boiler?

    You've probably heard of the term 'condensing boiler' and you may be thinking how does it fit with the 3 boiler types we show?

    Essentially, a condensing or High Efficiency boiler can be a combi, system or open vent boiler. Condensing boilers work on the principle of reusing heat that would normally be rejected into the atmosphere from the flue of standard efficiency (non-condensing) boiler.

    As a result, the temperature of the gases from the flue of a condensing boiler is typically 50-60°C compared with 120-180°C in a current non-condensing boiler. This creates a condensate (hence the name 'condensing'), which is harmlessly expelled as vapour through a flue and as liquid through a convenient drain point.

    All new condensing boilers installed in the UK must be High Efficiency Condensing models.


    Combination or 'combi' boilers

    This is the most popular type of boiler in the UK, now found in around 70% of homes. Combi boilers provide central heating and hot water without the need for a separate tank to store water; hence you can easily tuck them away under the stairs or in kitchen cabinets. They are most suited to: Homes with one bathroom, households with single people, couples, families with one child Usually available in following outputs: kw 24 30 35

    Benefits:

    • Instant, unlimited domestic hot water
    • Compact, easy to fit if space is limited

    Disadvantages:

    • Unable to run multiple showers or baths at the same time
    • Lower flow rate for hot water than an open vent or system boiler
    Combination or 'Combi' Boilers - lets-do-diy.com

    System boilers

    A system boiler (sometimes known as a 'sealed system') provides central heating and hot water via a storage cylinder housed in an airing cupboard - no need for water tanks in the loft, as with an open vent boiler.

    Most suited to: Larger homes with multiple bathrooms/ensuites; families. Usually available in following outputs: kw 12 15 18 24 30 38

    Benefits:

    • High flow rate for domestic hot water
    • No tank(s) in your loft
    • More than one hot tap / shower can easily operate at same time

    Disadvantages:

    • Hot water is not instant.
    • Once the water in the storage cylinder runs out you have to wait for it to reheat.
    • You'll need to find space for the cylinder (usually an airing cupboard)
    System Boilers - lets-do-diy.com

    Open vent boilers

    Open vent boilers are a peculiarly British invention. An open vent (sometimes known as heating only) provide central heating and hot water via a boiler, a storage cylinder housed in the airing cupboard and water tanks in your loft. If you're looking to do a full system overhaul most people opt to remove the tanks from the loft and turn their open vent system into a sealed system.

    Most suited to: Larger homes with an existing open vent boiler. Usually available in following outputs: kw 12 15 18 24 30 38

    Benefits:

    • High flow rate for domestic hot water
    • More than one hot tap / shower can easily operate at same time

    Disadvantages:

    • Once the water in the storage cylinder runs out you have to wait for it to reheat.
    • You'll need to find space for the cylinder (usually an airing cupboard)
    • The bulk feed and expansion tanks are usually sited in the loft - this can create a problem if you're considering a loft conversion.
    Open Vent Boilers - lets-do-diy.com



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