Fit the highest point of the Worcester Bosch Greenstar 4000 25 circuit — that is where entrained air collects.

How often should I service?

Annually — the float sticks with sludge in unfiltered systems.

Do I need to notify the manufacturer?

Only if the Worcester Bosch Greenstar 4000 25 is in warranty — Worcester Bosch require log of any part swap for labour claims.

Fit a new AAV on Worcester Bosch Greenstar 4000 25 when the boiler airlocks on start-up or the pump makes gurgling noises after refilling.

Isolate flow and return, unscrew the AAV from the top of the pump head or air separator on Worcester Bosch Greenstar 4000 25.

Loosen the AAV cap one full turn once refitted — a fully-closed cap defeats the float.

Refill the Worcester Bosch Greenstar 4000 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.

Any special height?: Fit the highest point of the Worcester Bosch Greenstar 4000 25 circuit — that is where entrained air collects.
How often should I service?: Annually — the float sticks with sludge in unfiltered systems.
Do I need to notify the manufacturer?: Only if the Worcester Bosch Greenstar 4000 25 is in warranty — Worcester Bosch require log of any part swap for labour claims.

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