BoilerFaultCodesRemeha E03 Fault Code
The Remeha E03 fault code means: your boiler has shut down because it detected that the exhaust gases are getting too hot, which is a safety measure to protect the internal components.. It appears on 7 Remeha models in our database.
Technical description: Flue gas thermostat exceeded
What causes the Remeha E03 fault?
This fault occurs when the internal heat exchanger becomes blocked with debris or limescale, preventing heat from being transferred to the water effectively. As a result, excessive heat escapes through the flue system, causing the safety sensor to trip and shut down the boiler to prevent melting or fire damage. The most common reason is a lack of annual servicing, which allows buildup to restrict the airflow and heat transfer within the unit.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Remeha models that show the E03 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Remeha E03 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