BoilerFaultCodesRemeha 3 0. Fault Code
Also written as 30 — same fault.
The Remeha 3 0. fault code means: your boiler has shut down because the water is not circulating properly, causing it to overheat too quickly.. It appears on 3 Remeha models in our database.
Technical description: Max.water temp.: Difference between flow and return temperature too high
What causes the Remeha 3 0. fault?
This fault occurs when the boiler's internal sensors detect that heat isn't leaving the unit fast enough, causing a dangerous spike in temperature. The most common reason is a failed pump that isn't pushing water around your radiators, or a blockage caused by sludge and debris that has built up inside the pipework over time.
This issue often comes to light during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump parts to seize.
DIY fix possible
Check that your pump is running and hasn't seizedEnsure all radiator valves are fully openCheck the system pressure and top up if it is below 1.0 barBleed all radiators to remove trapped air blocks
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Gas Safe Register →Remeha models that show the 3 0. fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Remeha 3 0. 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