System boilers are often referred to as sealed system boilers because the system is filled to approximately 1 bar pressure and sealed. They are connected to a hot water storage cylinder, usually installed in an airing cupboard. This type of boiler does not need an expansion tank in the roof.
Who needs a System Boiler?
They are particularly good for homes with more than one bathroom because the combination of boiler and hot water cylinder can deliver hot water quickly to several outlets simultaneously. A system boiler heats your central heating system directly and produces hot water for your cylinder
Firstly, many of the major individual components of the heating and hot water system are built into a system boiler, which means that installation is quicker, neater, easier and more efficient.
Secondly, the hot water is pumped from the system boiler through the heating system to the radiators and hot water cylinder, resulting in a fast response and more economical running costs. The system boiler removes the need for a feed and expansion cistern.