What does the Worcester Bosch Greenstar Si F40 fault code mean?
The F40 fault code on the Worcester Bosch Greenstar Si indicates a problem with the expansion vessel, which is responsible for maintaining pressure within the heating system. A faulty expansion vessel can lead to pressure fluctuations, causing the boiler to operate inefficiently or shut down.
Common Causes
- Loss of Air Pressure: Over time, the air pressure in the expansion vessel can diminish, leading to inadequate performance.
- Water Leakage: A rupture or leak in the expansion vessel can cause water to enter, compromising its function.
Can I fix it myself? (DIY)
It is advisable to call a Gas Safe Engineer to address this issue, as working with gas appliances can be dangerous. Attempting to fix the expansion vessel without proper training may lead to further complications.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for replacing a faulty expansion vessel on a Worcester Bosch Greenstar Si is around £200 to £300. This includes the cost of the part and labour, reflecting the complexity of the repair and the need for a qualified engineer.