BoilerFaultCodesGrant EE4 Fault Code
The Grant EE4 fault code means: your boiler has detected that the electrical wiring coming into the unit is connected the wrong way round.. It appears on 2 Grant models in our database.
Technical description: Supply L and N are reversed
What causes the Grant EE4 fault?
This fault occurs when the live and neutral electrical connections are swapped, meaning the power is flowing into the boiler through the wrong wire. It typically happens after recent electrical work has been carried out near the boiler, or if a new fused spur was installed incorrectly. Because this is a safety risk, the boiler's control board will automatically stop the unit from firing until the wiring is corrected.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Grant models that show the EE4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Grant EE4 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 27 April 2026