LOCKOUT: d Emergency

Potterton LOCKOUT: d Fault Code

Also written as LOCKOUTD — same fault.

The Potterton LOCKOUT: d fault code means: your boiler has shut down because the exhaust fumes are not being cleared away safely through the chimney or flue.. It appears on 2 Potterton models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: INADEQUATE FLUE DRAUGHT

What causes the Potterton LOCKOUT: d fault?

This fault occurs when the boiler's safety sensors detect that harmful exhaust gases are not being pulled out of your home effectively. The most common reasons include a failing internal fan that isn't spinning fast enough, a blocked flue pipe, or a faulty sensor that is incorrectly reporting a lack of airflow.

This issue can occur during periods of high winds, which can create back-pressure in the flue and prevent the boiler from venting correctly.

Typical repair cost £120-280 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Potterton models that show the LOCKOUT: d fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Potterton LOCKOUT: d fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026