What are the Different Boilers?

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Boilers are the heart of any central heating system and should be serviced on a regular basis.

installing a boiler

However, there will come a time when your boiler will need to be replaced either because it is no longer serviceable or it has come to the end of its lifespan.

When your boiler is being replaced you will need to choose the type of boiler that you are going to have installed, and unless you are a heating engineer you will not know the difference between the boilers that you can have installed.

This article will look at the different Central Heating Boilers that can be installed in your home.

Back Boilers


These types of boiler are fitted to a heating stove or open fireplace and are hidden behind the chimney in the home.

Although back boilers are not the first choice when buying a new boiler, however this type of boiler would be recommended if it was too complicated or too expensive to install a condensing boiler.

There are off course advantages and disadvantages to this type of boiler.


  • Cheaper to replace if this is your existing system
  • Reliability which reduces the chances of the  system breaking down
  • Will save you space as it is hidden behind the wall


  • They are more expensive to run and are not as efficient as other boilers
  • Difficult to install due to new regulations
  • Greater chance of Carbon Monoxide fumes leaking in to your property due to the open flume
  • Requires two tanks normally one in the attic and one in a cupboard
  • Limited choice
  • Draughty & Noisy

Condensing Boilers

All new boilers that are installed in the United Kingdom should be condensing boilers unless there are exceptional circumstances that a condensing boiler cannot be fitted.

Condensing boilers have been showing to be more energy efficient with most cases seeing a 90% increase in efficiency.

There are three types of condensing boilers, Regular, System Boilers and Combi Boilers and the all have one thing in common they extract heat from flue gasses.

As with all boilers there are off course advantages and disadvantages to this boiler


  • Up to 90% more energy efficient
  • Energy bills could be reduced by £130 a year
  • Conforms to new laws


  • Cost a lot more to buy however with lower energy bills extra cost can be recouped over a couple of years
  • Droplets from the flue can be nuisance

Combination Boilers

The combination Boiler or Combi Boiler as it is generally known is the most popular type of boiler installed in our homes.  On average 70% of boilers purchased every year are Combi Boilers.

There are a number of advantages of choosing a Combi boiler which include how economical they are to run and the size of them.

Designed to give you a constant flow of hot water any time you need it however the water pressure on these boilers is not as high as other boilers.

There are off course advantages and disadvantages to the Combi Boiler


  • As they are smaller they can fit in a kitchen cupboard and eliminates the need for a storage cylinder
  • Energy efficient which means they are cheaper to run
  • Instant unlimited Hot Water
  • Can produce 18 litres of water per minute at 35°C depending on the age of the boiler
  • You can purchase Storage Combi boilers


  • Hot water flow can be interrupted if a tap is turned on elsewhere in your home
  • Low volume of water
  • Lower water pressure
  • Not suitable if you live in a bigger house

System Boilers

This type of boiler is the middle ground between the smaller Combi Boilers and the larger Condensing boilers.

Although system boilers eliminate the need for cold water feed tank you still require a hot water storage tank.

As with the other types of boilers there are advantages and disadvantages to a system boiler


  • Increased Water Pressure
  • More space in your loft
  • Compact installation
  • Suitable for larger homes
  • Easier and neater to install


  • Expensive to install and repair
  • Still require space for a Storage Cylinder

Mark Turnbull works for a company that specialise in Central Heating Installation in Edinburgh and gas boiler replacements.