BoilerFaultCodesRemeha b5 Fault Code
Also written as B5 — same fault.
The Remeha b5 fault code means: your boiler has temporarily paused because it has reached the required temperature too quickly and is waiting for the system to cool down before restarting.. It appears on 3 Remeha models in our database.
Technical description: Control stop from 3 till 10 minutes: set flow temperature (t1) has already been reached and the heating demand still exists.
What causes the Remeha b5 fault?
This happens when the water inside the boiler gets hot much faster than the rest of your radiators, often because the heat cannot escape the boiler quickly enough. It is usually caused by restricted water flow, which can happen if your pump is slowing down, your heating filter is blocked with debris, or too many radiator valves are turned off at once.
This code is more common in autumn and spring when your heating is only needed in short bursts or when individual radiator thermostats are mostly closed.
DIY fix possible
Check that all radiator valves are fully open to allow heat to escapeEnsure the central heating bypass valve is not closedWait up to 10 minutes for the boiler to automatically restart
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Gas Safe Register →Remeha models that show the b5 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Remeha b5 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