UK trade guideBoiler Spares 5 min readUpdated 11 July 2026

How to Replace the Pressure Sensor on a Alpha E-Tec Plus 33 (UK)

Step-by-step UK guide to replacing the hydraulic pressure transducer on a Alpha E-Tec Plus 33. Part numbers, torques, commissioning.

Alpha

The part

Fit a new pressure transducer on Alpha E-Tec Plus 33 when the display shows correct pressure at rest but locks out on heat-up.

Isolate safely

The transducer on Alpha E-Tec Plus 33 threads or clips into the hydraulic block. Drop pressure to zero before removal.

Fit and commission

Refit with a new O-ring; over-tightening cracks the plastic body.

Recommission checklist

Refill the Alpha E-Tec Plus 33 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

Digital or analogue?
Alpha E-Tec Plus 33 runs a 5 V ratiometric transducer — the display board reads voltage directly.
Calibration?
None — the PCB self-references at 0 bar and 1.5 bar; recommission per OEM sheet.
Do I need to notify the manufacturer?
Only if the Alpha E-Tec Plus 33 is in warranty — Alpha require log of any part swap for labour claims.
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