Worcester Bosch Expansion Vessel 87161055450 (6L)

Genuine Worcester Bosch OEM expansion vessel for sealed heating systems on selected Greenstar appliances. The vessel absorbs water expansion on heat-up to stabilise pressure and protect boiler components.

• Manufacturer: Worcester Bosch
• Part type: Expansion vessel (sealed system)
• Capacity: 6 litres
• Connection: 3/8
• MPN: 87161055450
• GTIN / EAN: 4010009680352

Compatible ranges & examples*

Used across multiple Greenstar families (model/year dependent). Common compatibles include:

• Greenstar i / i System e.g. 12i System, 24i System
• Greenstar i Junior (RSF) 24i & 28i (NG/LPG)
• Greenstar Si 25Si / 30Si (NG/LPG)

*Always verify against your boilers data plate/parts list using MPN 87161055450 before ordering.

What this part does

The vessels air charge cushions pressure rises as water expands, reducing PRV discharge and protecting the heat exchanger and seals.

When to replace

• Frequent pressure loss or PRV dripping
• Rapid pressure increase on heat-up
• Vessel fails to hold pre-charge (membrane failure)

What’s in the box

• 1 Worcester Bosch expansion vessel 87161055450 (6L)

Installation & safety

Must be fitted and pre-charged by a qualified Gas Safe engineer. After installation, set pre-charge to spec and check system pressure/operation.