How to Replace the Fan on a Main Eco Compact 25 (UK)
Step-by-step UK guide to replacing the combustion fan on a Main Eco Compact 25. Part numbers, torques, commissioning.
Main
The part
Swap the combustion fan on Main Eco Compact 25 when you get low-speed lockouts (F28/F29 Vaillant, EA Worcester, F1 Ideal) or bearing whine.
Isolate safely
Remove the case, disconnect the fan plug and Venturi. Note the fan's part number stamped on the motor housing.
Fit and commission
On Main Eco Compact 25 the fan is torqued to 8–10 Nm — over-tightening cracks the composite plenum.
Recommission checklist
Refill the Main Eco Compact 25 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
- Which speed sensor connector?
- The Hall-effect sensor on Main Eco Compact 25 uses a 4-pin JST plug. Do not swap L1/L2.
- Do I need a new gasket?
- Always fit the OEM Viton gasket — the old one hardens and leaks flue gases into the case.
- Do I need to notify the manufacturer?
- Only if the Main Eco Compact 25 is in warranty — Main require log of any part swap for labour claims.
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