Choosing Your Heat Source: A Guide to the 3 Types of Boilers steffan@warmzilla.co.uk April 12, 2024

Choosing Your Heat Source: A Guide to the 3 Types of Boilers

Choosing Your Heat Source: A Guide to the 3 Types of Boilers
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    3 types of boilers illustrated - WarmZilla Blogs.

    Key Takeaways

    • The 3 types of boilers are Combi, Heat Only and System boilers.
    • Combi Boilers are single units that provide hot water and heating.
    • Heat Only boilers only produce heating, there is a separate expansion tank and larger cold water storage.
    • System boilers have a hot water tank and the boiler

    What are the 3 types of boilers?

    There are three main types of boilers that you can have installed in your home. Those are:

    • Combi (or Combinations) Boilers
    • Heat Only (AKA Regular or Conventional) Boilers
    • System Boilers

    Now you know the 3 types of boilers, you may have some questions such as, “What boiler type do I have?” Or “Should I swap to another boiler type?”. We’ll break down each boiler type for you, and you should know enough about the boiler types to answer these questions.

    What is a Combi Boiler?

    A Combi (or Combination) Boiler is a single unit that provides your home with heating and hot water. There are no tanks or cylinders attached to these boilers and they are the most popular boiler in England, with 54.8% owning one as of 2019 according to Statista.

    How does a Combi Boiler work?

    A Combi Boiler works by being connected directly to the mains cold water, and can heat the water as needed inside the unit.

    It heats the water using a component called an “integral heat exchanger”, and when you expect hot water, it instantly heats up the cold water from the mains as it passes over it.

    How a Combi Boiler works

    Combi Boiler Advantages

    • You get instant hot water and heating.
    • As they don’t have a separate tank, they take up less space.
    • They’re easier to install because you only need to install one unit.
    • They’re more efficient, with new combi boilers claiming over 90% efficiency.
    • Due to this efficiency, they may help lower your bills.
    • Easier to maintain because the combi boiler is so popular, nearly all engineers are trained on how to work on them.
    • Fresher water, as the water hasn’t been stagnant in a tank

    Combi Boiler Disadvantages

    • There can be pressure problems. As the boiler functions directly into the mains, it is reliant on the pressure of the mains supply being consistent. If there is a poor flow rate, this can be an issue.
    • Flow rate can drop if it is pulled from more than one source, so multiple bathrooms and showers sourcing water can cause the flow rate to drop.
    • Combi boilers don’t work with power showers as this shower type relies on a hot and cold water feed from a gravity fed system.
    • Due to the nature of the combi design, there can be more potential for things to break.

    Who is a Combi Boiler for?

    Combi Boiler is a great option but in particular it would suit a home that is smaller; with only one bathroom. The home would ideally have 10 or less radiators and have no loft to put a hot water tank in.

    What is a Heat Only (Regular or Conventional) Boiler?

    Heat Only Boilers are one of the oldest types of boilers that you’ll find in households (barring the odd few with coal boilers), and are also known as ‘Regular’ or ‘Conventional’.

    In the boiler industry, we call them ‘Heat Only’ simply because they produce hot water for central heating but not for hot water outputs like sinks, taps, baths, showers, etc. The ’Heat Only’ boilers requires a larger cold water storage cistern in your loft space and a hot water cylinder tank, which is used when you need a hot water output.

    How does a Heat Only (Regular or Conventional) Boiler work?

    The cold water tank is filled from the mains supply and feeds into the hot water cylinder, where it is warmed up by a heat exchanger in the boiler. A pump sends the hot water through the central heating system to supply radiators, taps, and showers.

    How a heat only Boiler works

    Heat Only (Regular or Conventional) Boiler Advantages

    • They are cheaper to replace generally, though the market and demand can change this.
    • Lots of outputs can be used, with hot water available to multiple taps and outputs.
    • Heat only boilers don’t rely on mains pressure, so the pressure is better.
    • You can have a redundancy in place if your boiler breaks down, with an electrical immersion heater installed. This means that if your boiler breaks, you still have access to hot water.

    Heat Only (Regular or Conventional) Boil Disadvantages

    • They aren’t as efficient as combi boilers as there is heat loss during the storage of water in the cylinder.
    • They do take up more space, as the system relies on a tank and the boiler.
    • You’ll need to wait for hot water, as the cylinder needs time to heat up.
    • Once the water in the tank runs out, it needs to refill before you can have more hot water.
    • They can be more expensive to install if you don’t already have a water tank.

    Who is a Heat Only (Regular or Conventional) Boiler for:

    A heat only boiler is a great option, but it is particularly suited to older households that are larger, have more than one bathroom and has low mains pressure.

    What is a System Boiler?

    System boilers are similar to Heat Only boilers: they need a hot water cylinder. The difference is that they do not need a cold water tank, and the components (pumps & valves) that are separate in heat only are built into the design of a system boiler.

    How does a System Boiler work?

    System boilers combine a hot water tank (cylinder) and the boiler to provide the heating and hot water to your home.

    System boilers do not have cold water tanks like heat only boilers, and are essentially a more advanced upgrade to how the traditional heat only boilers work.

    How a system Boiler works

    System Boiler Advantages

    The advantages of a System boiler are:

    • System boilers have many of its components internalised. This means that the amount of space it takes up is less.
    • Less components externally also means that the system boiler is easier and faster to install.

    System Boiler Disadvantages

    The disadvantages of a System boiler are:

    • It does share a pressure issue with the combi boilers in which the functionality is dependant on the mains pressure.

    Who is a System Boiler for:

    A system boiler is a good heating system, particularly for homes that don’t have low mains pressure and for whom the central heating system is more modern or up-to-date.