21.0 Low

Grant 21.0 Fault Code

Also written as 210 — same fault.

The Grant 21.0 fault code means: this code indicates that your boiler is currently running at its maximum factory-set heating capacity and is likely a status display rather than a mechanical failure.. It appears on 7 Grant models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Maximum heat output (Kerosene) (kW)

Engineer required

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

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Grant models that show the 21.0 fault code

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

Source

Grant 21.0 fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.

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