Which Boiler?


What is a system boiler?

An example of a central heating and hot water system layout using a system boiler with an unvented hot water cylinder

System boiler layout Enlarge image

An example of a central heating and hot water system layout using a system boiler with a pressurised hot water cylinder

System layout unvented Enlarge image

Unlike a combi, both a system boiler and a regular (conventional) boiler work on the principle of stored hot water - but a system boiler differs from a regular boiler in some important respects.

Firstly, many of the major individual components of the heating and hot water system are built in, which means that installation is quicker, neater, easier and more efficient.

Secondly, the hot water is pumped from the boiler through the 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.


i System boilers

  • 90.1% A
  • EST registered 
  • LPG boiler available
  • Solar compatible

    Image of Unique new features logo for Greenstar 12i System

    The Greenstar i System series is part of a market-leading range of energy-saving condensing gas-fired boilers from Worcester. They can cut heating and hot water bills by between 15-20% - and they're up to 30% cheaper to run than an older boiler.

    Greenstar condensing boilers deliver this energy-saving performance by recycling exhaust gases to extract and re-use latent heat - a highly efficient use of energy which also significantly reduces carbon dioxide in the atmosphere.

    • SEDBUK* A-rated - environmentally friendly
    • 12kW output (24kW output also available for this boiler)
    • Compact dimensions - space saving and siting flexibility
    • Compatible with Greenskies solar water heating
    • Proven cast aluminium heat exchanger
    • One man lift- 27kg
    • Wall mounting frame with pipes behind - no exposed pipework
    • Low NOx and CO2 emissions - environmentally friendly
    • 2 year** warranty with 10 year** warranty on primary heat exchanger

    *Seasonal Efficiency of Domestic Boilers in the UK

    30 CDi System boiler

    Suitable for the larger property, with all the above features.