What Is A Combi Boiler?

January 27, 2020 | Boilers

Boiler Replacement & Installation Service

Are you considering a new boiler for your home? You’ve probably heard about combi boilers, but you might not be sure what they are. If you’re asking the common question “What is a combi boiler?” read on to find out expert guide that tells you everything you need to know about this popular type of boiler.

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What Is A Combi Boiler?

A combination (or combi) boiler is a compact single unit that provides both hot water and heating to your home. Combi boilers are a space-saving solution, heating water on demand instead of heating it then storing it thus eliminating the need for a cold-water storage tank or hot water storage cylinder – something that was necessary with an older boiler system.

What Is A Condensing Boiler?

Some homeowners become confused about combi boilers and condensing boilers thinking that they are two different things. In fact, combi boilers are simply a form of condensing boiler. Condensing boilers are just water heating appliances which run on either oil or gas and which improve the energy efficiency of your central heating by turning water vapour condensation into heat. Not all condensing boilers are combi boilers, however, and this is where some of the confusion comes from.

Condensing boilers work by having two heat exchangers inside them to recycle the heat into the system rather than losing it to the atmosphere. Condensing boilers have no need for the pilot light to burn constantly as they ignite only when heat or hot water is demanded.

If you aren’t sure whether you have a condensing boiler, one way of determining the answer is to work out when it was installed. If the installation date was after April 2005, you probably have a condensing boiler. This is because new regulations were introduced that required every replacement or new boiler installed after that date to be a condensing boiler.

Another way to tell is to read the user manual supplied with your boiler or to check its flue terminal. This will usually be sticking through one of the external walls close to the boiler site. If it’s plastic and has white steam coming through it whenever the boiler is operational, you probably have a condensing boiler. A non-condensing boiler will usually have a flue that is made from metal and there may be no visible gases.

Whether you have an old non-condensing or a condensing boiler, you can have yours replaced with a modern combi boiler that will make your home even more energy efficient.

How Do Combi Boilers Work?

To supply you with hot water, your combi boiler will always be on standby, connected to your home’s mains water supply. If you turn the hot tap on, the boiler will be triggered to switch on and heat the water via a heat exchanger, giving you hot water on demand whenever you want it. Combi boilers follow the same heating process as conventional boilers, however their expansion tank is inside the boiler itself, allowing the water to be heated inside the boiler before it’s sent out to your radiators.

Should I Get A Combi Boiler?

All households are different and have different heating requirements. Combi boilers offer several advantages but they may not be the right choice for everybody. Some of the benefits include:

  • They save space – they can easily fit into a regular-size kitchen cabinet
  • No large water tanks or storage cylinders are required
  • The boiler has less pieces so there’s a lower risk of the pipes freezing
  • They’re usually easier, cheaper and quicker to install than a standard boiler

There are, however, a couple of downsides:

  • If you live in a busy, large household with several bathrooms, water pressure could be lost
  • All the heating will take place in a single central unit. That means if you turn on the hot water your central heating pauses

What Size Combi Boiler Do I Need?

There are many different combi boilers available, with several outputs and each suited to different central heating requirements and different homes. A boiler with an output of 28kW would be suitable for a home of medium-size with regular heating and hot water needs, while a boiler with a 40kW boiler may be better for a larger household that has a higher demand for central heating. It can be difficult to determine which output you’ll need for your home, therefore here is a brief guide to some of the most common kW outputs paired with the type of home they would best suit:

  • An output of 24-27kW suits a property with 1 or 2 bedrooms, up to 10 radiators and a single bathroom
  • An output of 28-34kW best suits a property with 3 or 4 bedrooms, up to 15 radiators and one or two bathrooms
  • An output of 35-42kW best suits a home with four or more bedrooms, up to 20 radiators and two or more bathrooms

If you aren’t sure which size boiler is best for your needs our team of heating engineers can offer you expert advice tailored to your individual circumstances.

How Much Will It Cost To Install A Combi Boiler In My Home?

The price of combi boiler installation varies depending on which size, brand, maximum flow rate and output you choose. A more powerful boiler will usually cost more, but rather than cutting costs, it’s best to choose a new combi boiler to suit your home’s requirements.

Of course, price is sure to be a key factor when you’re selecting a new boiler and therefore you should do some research to determine which type is most cost-effective for you. If you’re looking for expert advice about choosing the best boiler for your home, contact our qualified team of Gas Safe Heating Engineers today. We’re on hand to give you all the information you need and to arrange your boiler installation so your home can stay warm and comfortable all year round.

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