Worcester Bosch Greenstar 4000 21kW System Boiler Including Flue & 15mm Scale Reducer

The Worcester Bosch Greenstar 4000 21kW System Boiler Including Flue & 15mm Scale Reducer is a premium heating package designed for modern homes with a sealed heating system and an unvented hot water cylinder. Supplied with a horizontal flue kit and a 15mm Scale Reducer, this complete solution delivers reliable central heating while helping to reduce limescale build-up in hard water areas, protecting the boiler and maintaining long-term efficiency. Combining Worcester Bosch's renowned engineering with quiet operation and smart control compatibility, the Greenstar 4000 is an ideal choice for homeowners seeking dependable, energy-efficient heating.

Designed for small to medium-sized homes, the Greenstar 4000 21kW System Boiler features a sleek contemporary design, intuitive full-colour display, and compatibility with Worcester Bosch EasyControl. Its compact dimensions allow for flexible installation while providing consistent heating performance and outstanding reliability.

Key Features

• 21kW System Boiler
• Includes Horizontal Flue Kit
• Includes 15mm Scale Reducer
• Fuel Type: Natural Gas
• Designed for sealed heating systems with a separate hot water cylinder
• ErP A Rated for heating
• Up to 94% central heating efficiency
• Quiet Mark certified
• Contemporary full-colour display
• EasyControl compatible
• Solar compatible
• Wide modulation range for improved efficiency
• Compact wall-mounted design
• Up to 10-Year manufacturer's warranty (subject to installation, registration, and Worcester Bosch warranty terms)

Ideal for Modern Heating Systems

The Worcester Bosch Greenstar 4000 21kW System Boiler is ideal for small to medium-sized homes with a sealed heating system and separate hot water cylinder. It provides reliable heating performance while delivering stored hot water efficiently throughout the home.

The included 15mm Scale Reducer helps minimise limescale formation, making this package particularly suitable for homes in hard water areas and helping to protect the boiler's heat exchanger over time.

Powerful Central Heating Performance

Delivering a 21kW central heating output, the Greenstar 4000 System Boiler provides consistent warmth while operating with excellent energy efficiency. Its advanced condensing technology and wide modulation range help reduce gas consumption, lower heating bills, and maintain comfortable indoor temperatures throughout the year.

Compact Contemporary Design

Designed with modern homes in mind, the Greenstar 4000 features a stylish appearance and a compact footprint that allows installation in kitchens, utility rooms, or cupboards where space is limited.

Dimensions

• Height: 724mm
• Width: 400mm
• Depth: 310mm

The included horizontal flue and 15mm Scale Reducer provide a complete installation package while helping to ensure long-term system performance.

Advanced Energy Efficiency

With an ErP A rating and up to 94% central heating efficiency, the Greenstar 4000 uses advanced condensing technology to maximise heat recovery while reducing fuel consumption.

Its wide modulation ratio automatically adjusts output to match heating demand, helping improve efficiency and reduce unnecessary energy use.

Smart Heating Control Compatibility

The Greenstar 4000 is fully compatible with Worcester Bosch EasyControl, allowing homeowners to manage heating schedules remotely using a smartphone or tablet. It is also compatible with solar thermal systems, offering greater flexibility for future renewable heating upgrades.

Reliable Performance & Easy Maintenance

Built to Worcester Bosch's renowned quality standards, the Greenstar 4000 features a durable internal design, Quiet Mark certified operation, and a clear full-colour display for straightforward monitoring and control.

Its installer-friendly layout and easy servicing access help simplify installation and ongoing maintenance.

Warranty & Peace of Mind

The Worcester Bosch Greenstar 4000 21kW System Boiler Including Flue & 15mm Scale Reducer includes up to a 10-Year manufacturer's warranty when installed and registered in accordance with Worcester Bosch's qualifying warranty conditions, providing long-term confidence and dependable after-sales support.

Why Choose the Worcester Bosch Greenstar 4000 21kW System Boiler Including Flue & 15mm Scale Reducer?

• Premium Worcester Bosch system boiler
• 21kW heating output
• Includes Horizontal Flue
• Includes 15mm Scale Reducer
• Quiet Mark certified
• Up to 94% central heating efficiency
• EasyControl compatible
• Solar compatible
• Contemporary full-colour display
• Up to 10-Year manufacturer's warranty