BoilerFaultCodesRemeha C4 Fault Code
The Remeha C4 fault code means: your boiler is simply notifying you that it is currently busy heating your tap water and there is no actual fault.. It appears on 2 Remeha models in our database.
Technical description: Boiler is operating for DHW
What causes the Remeha C4 fault?
This code appears when the boiler detects a demand for hot water from a tap or shower. It is a status indicator rather than a malfunction, showing that the internal components are currently prioritising your hot water over central heating. Once the tap is turned off, the code should disappear as the boiler returns to its normal standby or heating mode.
DIY fix possible
No action is required as this is a normal status message.Wait for the hot water tap to be turned off and the boiler will return to its normal standby or heating mode.
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Gas Safe Register →Remeha models that show the C4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Remeha C4 fault code information on this page is sourced and cross-checked against the official Remeha service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026