20 High

Halstead 20 Fault Code

The Halstead 20 fault code means: your boiler has stopped working because it cannot detect a flame, meaning it is currently unable to produce heat or hot water.. It appears on 8 Halstead models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: No flame - Gas valve V1-V2 failure
Typical repair cost £150-300 (including labour)

Engineer required

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

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Halstead models that show the 20 fault code

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

Source

Halstead 20 fault code information on this page is sourced and cross-checked against the official Halstead service / installation manuals for each affected model.

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