What is a Combi Boiler?

For most of the time we don’t think about our boilers, they just do their work in the background.  We only really think about them when:

If you are in the position that it’s time to replace your boiler with a new one you could easily find that you are looking at a multitude of different types by looking on-line.  You will likely be surprised at how many options there are.

If the residence you have is of an average size and you have spoken to a heating engineer about your needs, it is a good chance that their recommendation was for a Combination (aka: Combi) boiler.  In light of this you may want to find out:

  • What is a combi boiler?
  • How does a combi boiler work?

If you are asking yourself these questions, then you are reading the right article as we have answered these questions below.

The basics of Combi boilers

Combi boilers: why should I choose one?

  • The combi boiler is very much by a long margin the most often selected gas powered boiler system in the U.K..
  • For an average household in the U.K. they are usually the recommended choice as they provide the heating and hot water in the most efficient way.
  • All the parts of the boiler are in a single cabinet. This means minimal impact on your living space.  There are even extra compact models on the market.
  • They are:
    • Relatively simple to install so costs are less
    • Simple to operate
    • Simple to maintain

A combi boiler: what is it?

The combi boiler has this name as it combines within a single cabinet the facility to generate both:

  • Heating.
  • Hot water.

A great attraction a lot of people find regarding this type of boiler is there is no requirement to have a separate water heater.  You are likely to be aware that in a good number of older properties they had:

  • An immersion heater that was usually located in an airing cupboard
  • A water supply tank in the attic.

In the above older type of system, you needed to think ahead and make sure the immersion heater was turned on and give it time to heat up the water.  As you are likely imagining this is a less efficient approach to that provided by a combination boiler.  Also, the old approach took up a lot more space in your home that could be put to more useful purposes.

Gas powered Combination boilers: how come they are more efficient?

The main reasons combination boilers are more efficient are:

  • The combination boiler only heats water when you demand it by turning on a hot water tap!
  • They are specifically designed to focus fuel/energy usage to heat the water requested it does not waste energy heating up water that you may not use!

Therefore, the combi boiler not only has the ability to reduce your energy bills but also reduces your carbon footprint compared to older systems, so it is kinder to the planet.

Combination boilers: how do they work?

The combination boiler heating system pulls water directly from the mains supply to the property.           As you turn on a hot water tap the system senses it and the gas burner in the boiler ignites and a heat exchanger transfers the heat energy into the water.  This smart system means you get hot water flowing through the pipes of your property very very quickly.

In addition, in order to get hot water to your tap as soon as possible they have an in-built pre-heat system.  This means the boiler keeps a small amount of water at a good temperature so that it can provide hot water very very quickly when you turn on a hot water tap.  If you have ever wondered why a combination boiler quickly turns on and off when no one is running a tap and heating is off now you know it is the pre-heat system.

Condensing technology: what is it and why do I need to know?

The U.K.s building regulations now have a requirement that all gas-powered combination boilers incorporate condensing technology.  This new rule ensured homeowners who put a combination boiler in their property would reap the reward of significantly improved efficiency.  You may be surprised to learn with older boilers that up to 50% of the heat energy was being completely lost due to it escaping via the flu.  Within a modern boiler that is of a condensing type it is different and the heat that is in the combustion gases is used to pre heat the cold-water stream as it comes into the system.  As you will no doubt have recognised this means:

  • The environment is more protected by bringing down the CO2 emitted.
  • It is more fuel efficient so reduces fuel bills.

Of all the sizes of combination boiler which one do I need?

When looking at the right size of combination boiler for your property there are a number of factors, but the main ones are:

  • How much demand for hot water do you have?
  • How many radiators are you looking to run?

However, to give you a bit more of an idea it is rule of thumb that a combination boiler of 20-35kW has the capability to be an effective choice for an average design three to four-bedroom house.  If this size of house also has ensuite bathrooms you are likely to need a 30-35kW system.  If, however you are fortunate enough to live in a bigger property you are likely to need a system of 35-42kW.  It should be noted though that if you are in this larger size of property you should consider the option of a system boiler.

What are the other considerations to think about when choosing a combi boiler for my property?

When looking at the right combi boiler for you it is best to also look at what controls are available to control the heating aspect.

You will find a number of combi boilers have the option of having a computer control and modern thermostats.  These have the ability to make sure efficiency is maximised and so reduce your fuel bills.

You may also want to give some thought as to if you want/need to be able to have control of your heating from a smart phone.

Contact Add Heat today for to talk through your combi boiler options

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