S.28 Medium

Heatline S.28 Fault Code

Also written as S28 — same fault.

The Heatline S.28 fault code means: your boiler has temporarily stopped heating your hot water cylinder because it has reached a protective safety limit meant to prevent the system from overheating.. It appears on 8 Heatline models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: The boiler blocks tank reheating after a reheating cycle.
Typical repair cost £120-250 (including labour)

Engineer required

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

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Heatline models that show the S.28 fault code

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

Source

Heatline S.28 fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026