Worcester Greenstar 4000 21kW System Boiler
The Worcester Greenstar 4000 21kW System Boiler is a reliable and efficient choice for medium to large homes, especially those that use a stored hot water cylinder. Designed to deliver consistent heating performance, this model balances energy efficiency with everyday practicality.
Its compact, lightweight build makes installation straightforward, even in tighter spaces. The boiler comes with a built-in pump and expansion vessel, helping installers achieve a tidy and efficient setup. Homeowners can also enhance comfort and control through a wide range of optional heating controls, including modern smart thermostats for improved efficiency.
Key Features
Compact, space-saving design
Built-in pump and expansion vessel
Optional plug-in diverter valve
Compatible with a wide range of optional heating controls
Ideal for medium to large homes using a hot water cylinder
Technical Information
Manufacturer: Worcester Bosch
Model: 4000
MPN: 7733600383
SKU: 79146
GTIN: 4057749856722
Product Type: Gas System Boiler
Performance:
CH Output: 21kW
CH Output (BTU): 71,000
ErP Heating Rating: A Rated for Heating
Dimensions:
Height: 724mm
Width: 400mm
Depth: 310mm
Weight:
Gross Weight inc Packaging: 40kg
Warranty:
7 Years (Subject to manufacturer T&Cs)
FAQs
Is the 21kW output suitable for my home?
The 21kW model is ideal for **medium to large properties**, particularly those with several radiators and a stored hot water cylinder.
Do I need a hot water tank with this boiler?
Yes — as a **system boiler**, it works with a hot water cylinder but does not require a loft-installed cold water tank.
Can I add smart controls to this boiler?
Absolutely. The Greenstar 4000 range supports a variety of **optional and smart heating controls**, including wireless and app-based options for better efficiency and convenience.
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