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What is a combi boiler?

For those worried about energy efficiency and the cost of heating their home, a combination boiler may be the simplest solution! Not only does this handy utility mean your entire household heating system operates from one space-saving unit (no water cylinder or tank needed!), it also saves you money with installation and running costs, and even gives you all the benefits of a power shower without requiring a pump.

How does a combi boiler work?

Controlling both your central heating and hot water, a combi boiler is an all-in-one solution that serves as both a central heating boiler and hot water cylinder. An almost ‘intuitive’ fit for any household, a combi boiler reacts when a hot water tap is turned on, or when it detects the household is below than the pre-set temperature. Automatically responding by sending hot water to the required tap, or firing up the central heating, a combi boiler means hot water is available 24/7 and delivered at mains pressure, so no pump is required for a ‘power shower’.

A type of condensing boiler, it also makes the most of the exhaust gases by turning them into liquid condensation and using the latent heat that regular boilers would waste. In other words, a combi boiler brings together the very best of heating efficiency, space-saving, and cost-effectiveness, for an optimum home heating solution.

Why choosing the right combi boiler is important

Choosing the right boiler is essential to guarantee the correct flow of hot water through your home’s taps and showers, and to ensure your energy bills remain level. The wrong boiler type could lead to long delays for hot water and high energy bills.

Combi boilers have different flow rates, central heating outputs, and hot water outputs. As a rule of thumb, the higher the flow rate, the more likely you’ll be able to run a bath without any issues. Otherwise, most combi boilers will offer enough hot water for a shower and the usual taps installed in your property for up to two bathrooms and 3 bedrooms.

How do I know if a combi boiler is right for my home?

There are a couple of ways to tell if a combi boiler is right for your home. The first and most obvious way to tell is the current layout of your central heating system. If your home only has a boiler installed but doesn’t have a loft tank and hot water cylinder installed, your current boiler is a combination boiler. For an engineer, this tends to be the easiest boiler replacement as it’s just a simple swap between boilers.

If you have a cylinder or tank installed, but experience reduced water pressure when using your shower or running taps, it’s possible that your mains pressure is insufficient for a combination boiler to be installed.

What are the advantages of a combi boiler?

The most obvious benefit of a combi boiler is having both hot water and central heating on demand, with high responsivity to temperature and tap usage that makes them incredibly user-friendly. Pre-empting manual operation of central heating, as well as eliminating any waiting period for hot water, they serve as one of the most convenient types of boiler system. Other benefits include:

  • Space-saving, ideal for those who want a boiler without a water tank
  • Does not require loft space
  • Unlimited heating and hot water when you need it
  • No need for water cylinders
  • Requires less pipe-work on installation, leading to easier maintenance
  • Delivers water at mains pressure

What are the disadvantages of a combi boiler?

Unfortunately, there are some downsides to the compact convenience of the combi boiler, and in some cases, it may not be the most effective choice for heating your home:

  • Not ideal for homes with low water pressure
  • Cannot deliver a high capacity of hot water to multiple places i.e. two showers
  • Not suited to larger households
  • Power showers cannot be installed with these boilers

Combi boiler alternatives

Combi Boilers are fast becoming one of the UK’s top choices for domestic boilers, available in electric and gas models, and increasingly the go-to choice for boiler replacement units. One of the best types of boiler for those looking to reduce heating bills, with water available on demand; unable to be wasted and left to cool again.

However, multiple models are available for those looking for a new boiler installation, and it’s well worth comparing different types of boilers to make sure you find a boiler that best fits your home:

Regular boilers (also called conventional or traditional boilers) require both a cylinder and a tank, usually installed in the loft. These remain a suitable choice for homes with multiple bathrooms or where hot water will be required for more than one faucet at one time. They are able to provide large volumes of hot water, but require time to heat – and then a period of re-heating should the hot water remain unused.

System boilers require a water cylinder but not a tank. Like regular boilers, they can provide multiple taps with hot water simultaneously. System boilers are a relatively economical choice, and the lack of tank also assists with easier maintenance. They require time to heat up, and unused hot water will cool again.

What are the most energy-efficient boilers?

Combi boilers have become the UK’s favourite boiler system, and for good reason – when it comes to boiler efficiency ratings, combi systems are among the best A-rated boilers. The self-contained unit means that energy and heat isn’t wasted like it is with a water cylinder, and for smaller households this makes it an ideal choice for reducing energy bills, especially if your current boiler system is tank-based and better suited to multiple bathrooms. For larger households, these benefits still apply, however it may be better to consider a green energy approach like solar panels while maintaining the capacity of a water cylinder, as these are not compatible with combi boilers.

Gas Safe boiler installation

Combi boiler installation is relatively complicated compared to other boiler types, making it even more vital that only a qualified professional ensures its safe and proper installation. For gas combi boilers it is especially important that only a Gas Safe registered boiler engineer is ever booked to install, maintain, or fix your domestic boiler. This is easily verified by asking for the identity card all registered engineers must carry with them – boiler advice or servicing from an unqualified engineer can invalidate your manufacturer warranty/guarantee and could be incredibly dangerous.

Combi boiler replacements that update old boiler systems may also involve:

  • A power flush of your pipes, performed with a high pressure pump and chemical cleaners
  • Closer inspection and maintenance of pipes, or new pipe installation
  • Safe disposal of the old unit

For these reasons it is important that only experienced, qualified professionals deal with any boiler services you may require.

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