With a combination boiler, you can combine your gas central heating with your domestic hot water with one, easy-to-use box.
It serves to provide you with a continuous stream of on-tap hot water water heaters as well as heating a hydronic heating system in a large house.
When your domestic hot water (DHW) is run off, combi central heating boilers will divert all power to instantly heating the DHW. Upmarket combi central heating boilers often combine the stored water and gas or to give a faster tap flow rate.
Large commercial units are also available. High flow rate combination boilers can simultaneously supply two showers.
Single combination units can even be used to supply separate heating zones – for a higher level of temperature control and the possibility of multiple bathrooms.
Alternatively, you can have one unit for one bathroom and a different one for another. This provides a back up in case of a breakdown.
Central heating installation costs for combination boilers are significantly lower than other methods and much less space is required – since no water tanks, added controls or additional pipes are needed.
With a market share of 70%, combination central heating boilers are highly popular in Europe.
However, combination boilers are not without disadvantages. The flow rate in higher when using a storage cylinder instead of a combi boiler, particularly in winter. And, although heating water on demand does improves energy efficiency, it limits the volume of water available.
A flow regulator valve may be needed to control the amount of water used because the water supply pressure cannot be too low.
Combination central heating boilers also have many moving parts and so are less reliable than tank systems.