Worcester Bosch Greenstar 4000 Natural Gas Boiler 21 kW is encompassing features from our range topping 8000 Style, informed by insights from installers and featuring real advances in fixing flexibility, it takes what was the nations favourite boiler and makes it even better.

• Ease of installation simple switch to previous Worcester i system models with pre-piping jig offering rear piping as standard
• Flexibility of siting provided by long flue lengths (up to 12 m with 60 mm/100 mm flues) and a 500 ml integrated condensate siphon to reduce the risk of freezing
• Wide modulation range designed to optimise efficiency when heating demand is low
• High-end design, quiet operation (up to 42 dB (A)) with an intuitive, long text and colour boiler display for ease of use
• 7 Years guarantee extended to 8 years when installed with any greenstar system filter
• Quiet operation from 42 dB (A)
• Modulates down to 3 kW central heating output (1:10)
• Compatible with our Greenstar intelligent filling system
• Intuitive full-colour long-text display
• 100 Percentage planet friendly packaging