The Greenstar 4000 30kW Combination Boiler is the direct upgrade for it's predecessor the Greenstar 30i and is most suited to small to medium sized homes with one bathroom. It features a modern new design, a full colour text display that is easy to use and it is exceptionally quiet too. The Greenstar 4000 has a wide power range to meet all of your heating and hot water needs, whilst doing so efficiently.