How to Replace the Primary Heat Exchanger on a Worcester Bosch Greenstar Ri 15 (UK)
Step-by-step UK guide to replacing the aluminium/stainless primary HEX on a Worcester Bosch Greenstar Ri 15. Part numbers, torques, commissioning.
The part
Replace the primary heat exchanger on Worcester Bosch Greenstar Ri 15 when you see combustion products blowing back, F62/L9 faults or sooting on the burner.
Isolate safely
Drain and cap all four connections on Worcester Bosch Greenstar Ri 15. The HEX weighs 12–18 kg — get a second pair of hands.
Fit and commission
Torque new HEX unions to the OEM figure (typically 40 Nm for cast, 28 Nm for stainless) and refit new burner and door gaskets.
Recommission checklist
Refill the Worcester Bosch Greenstar Ri 15 to 1.2 bar cold. Bleed high-point radiators and the internal AAV.
Run a full flue-gas analysis after 15 minutes. Log the reading against the OEM commissioning envelope in the Benchmark book.
Frequently asked questions
- Warranty implications?
- A HEX swap on an in-warranty Worcester Bosch Greenstar Ri 15 must be logged with the manufacturer — otherwise the labour claim voids.
- System clean first?
- Mandatory — power-flush and fit a magnetic filter or the new HEX will block within two years.
- Do I need to notify the manufacturer?
- Only if the Worcester Bosch Greenstar Ri 15 is in warranty — Worcester Bosch require log of any part swap for labour claims.
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