Worcester Bosch · Greenstar Si Compact ErP
C6 215Fan running too fast
This code applies to Greenstar 25Si Compact ErP, Greenstar 30Si Compact ErP. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Do not open the case or inspect the fan or flue yourself.
- Arrange a Gas Safe registered engineer.
How an engineer may fix it
Check fan movement and speed feedback, wiring and connectors, air/flue restrictions and the control board; repair or replace the defective part and verify combustion.
Manufacturer source: Worcester Bosch — Greenstar Si Compact ErP Installation, Commissioning and Servicing Instructions (6 720 813 278). Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.