
A Combi Boiler is a central heating boiler and water heater combined into one packaged unit. There is usually no separate hot water cylinder. No additional water storage tank or F&E(Feed and Expansion tank). Where space is limited combi boilers are usually fitted. In the past they were usually suited to flats and small properties. However large combi and storage combi’s have emerged that can meet the requirements of larger homes. Technical sizing and specification requirements still have to be done to determine suitability.
The only drawbacks of a combi boiler is that no backup immersion heater is available. Additionally if important components goes down, you could be without both hot water and heating. An electric shower can be fitted if a backup is required.
If you are looking for more information on combi boilers or looking for installation, please feel free to contact us.
Recommended Products for Maximum Life
For a combi boiler’s life to be prolonged, we recommend the installation of the items shown below. We have preferences of what we install, however as long as an equivalent is installed, it’s perfectly ok.
- Controls – Preferred choice is direct modulating controls otherwise Tado or Drayton Wiser. You may also use OpenTherm controls if your boiler supports it, to save further on your heating bills. See OpenTherm Boilers and Controls
- Central Heating Filter – Preferred choice Fernox Omega TF1 or Spirotech MB2
- Central Heating De-aerator – Preferred choice Spirovent RV2 / IMI Zeparo Deaerater
- DHW Expansion vessel mini – Preferred choice Caleffi Mechanical Shock arrestor
- Limescale Prevention – Preferred choice is water softener. At minimum, an Inline Magnetic Limescale Filter
Installation Best Practice

Having carried out many installations we have determined that the installation shown in the above picture will produce a highly maintainable system and one which minimises corrosion. There are a few key aspects of this method of installation that have very high benefits for the homeowner. There are some variations required dependent on your particular boiler model that are not shown here. You may contact us for a consultation to provide model specific information that will help you get the most out of your system with a very long life system.
Tools and Resources
Reduce the Flow Temp for upto 8 percent savings.
Combi Boiler Fault Finding information
Combi Boiler Condensing savings calculator