Combi boilers explained
What is a combi boiler?Combi boilers are one of the most popular types of boiler in the UK. Also known as combination boilers, they act as both water heaters and a central heating boiler without the need for additional water storage systems.
Their compact nature means they’re perfect for small to medium-sized homes, and this factor, combined with their simplicity makes them an ideal choice for many households.
How does a combi boiler work?Functioning as both a water heater and a central heating boiler, combi boilers can heat water directly from the mains when you turn on any hot tap in the system. They have two independent heat exchangers – one for the radiators and the other for the hot water supply. The primary heat exchanger focuses on your radiators and carries hot water around your home. The secondary exchanger is for heating the water that comes out of your taps. This heats an external clean water pipe that runs through the system, feeding it out to the taps in your home.
Condensing combi boilers
Condensing combi boilers are far morethan non-condensing, which are believed to account for around 16% of the world’s CO2 emissions. The heat exchangers in a condensing boiler recover more heat from the burning gas, which is then used to heat the water. As a result, they can be up to 25% more energy and cost efficient than their non-condensing counter-parts.
It is now compulsory that all new boilers must be condensing.
Pros and cons of a combi boiler
Benefits of a combi boiler
- They're generally very economical and energy efficient, as the water for your home is heated instantly, meaning you can have a hot shower without having to pre-heat the water.
- They’re compact, so perfect for smaller homes with little or no loft space – many other boilers require hot water storage tanks.
- Installation is often cheaper, as less pipework is required to feed hot water and warmth around your home.
- They’ll be easier to get fitted - most boiler engineers are trained to repair them as they’re so common.
Disadvantages of a combi boiler
- You may suffer from reduced water pressure if you’re using multiple taps and/or the shower at the same time; which could be an issue for larger households or with homes that have to cater for several people.
- There are several moving parts in the boiler unit, meaning there’s more chances for something to go wrong than with a conventional boiler.
- You’re entirely reliant upon your boiler for both hot water and heating – if this breaks down you will lose both. Other systems with hot water tanks can still rely on these even when the boiler is experiencing issues.
- Hot water is delivered at mains pressure so you’re unlikely to be able to support a power shower.
Potential problems with a combi boilerIn areas with very hard water and a high scale content, the heat exchanger can ‘fur up’ with limescale if and water flow can slow. Most savvy engineers will use limescale reducer to prevent the build-up in the first place, however, once the heat exchanger plate is covered in limescale, you’ll probably have to get it replaced.
Different fuel types for a combi boiler
Whilst there’s a range of different fuel types that can be used to power a combi boiler, the three most popular are gas, electric and oil-fired. Find out the pros and cons of each below:
|Gas Combi Boilers||Gas boilers are the most popular fuel type.
Gas is supplied from the mains and feeds directly into the boiler, which burns the gas to make hot jets that play on the heat exchanger to heat up the water.
|Electric Combi Boilers||The second most popular fuel type.
Rather than burning fuel to heat the water that powers the central heating system, electricity is used to heat elements within the boiler, which then heats water.
|Oil Combi Boilers||Oil boilers work in very much the same way as gas or electricity boilers, except they will be powered by a supply of oil, which will need to be delivered and stored in a tank somewhere in your home or garden.||
|LPG Combi Boilers||LPG combi boilers are similar to oil combi boilers but instead of using oil as a fuel supply, they use LPG (Liquid Propane Gas) instead.
Similar to an oil boiler, you’ll need it delivered to your home and a storage tank to store your gas.
You’ll most likely have seen caravans running their cooking appliances off smaller portable LPG gas tanks but larger storage tanks are available to rent or buy for your home.
How much does a combi boiler cost?
Prices* will range across different brands, but the following provides a rough guideline:
|Boiler type||Price range|
|Gas combi||£499 - £1400
|Oil combi||£1,107 - £3,770|