How to Replace a Worcester Bosch Greenstar 25i Flow Sensor (UK)
Fit a new flow sensor on the Worcester Bosch Greenstar 25i. UK part number, isolation and torque steps.
Worcester Bosch
Part number
The Worcester Bosch Greenstar 25i uses the turbine flow sensor 87161425540. Check the GC serial number sticker inside the case — Worcester Bosch revised the flow sensor at least once during production.
Isolate
Turn off the gas at the isolation cock. Switch off 230 V at the fused spur. Drain to just below the flow sensor: on the Worcester Bosch Greenstar 25i, the drain-off is on the return pipe.
Fit
Unclip the flow sensor. Transfer the O-rings if OEM includes new ones — always fit the new seals supplied. Torque any brass unions to 25 Nm. Refill to 1.2 bar, bleed and fire for a wet check.
Frequently asked questions
- OEM or compatible?
- For gas-carrying components on the Worcester Bosch Greenstar 25i always fit OEM. Non-gas parts (fans, PCBs, pumps) — OEM keeps the warranty valid.
- Do I need to re-commission?
- Yes — record combustion CO/CO₂ ratio after any gas-side work per BS 6798.
Shop the spares
Browse boiler spares — 14,820 live parts.
View Boiler Spares