BoilerFaultCodesRemeha B@% Fault Code
Also written as B — same fault.
The Remeha B@% fault code means: your boiler is overheating too quickly because water isn't moving through the system fast enough, causing it to take a ten-minute break to cool down.. It appears on 7 Remeha models in our database.
Technical description: Maximum acceptable flow temperature rise exceeded. The boiler will shut off for ten minutes, then restart. Should the flow temperature conditions remain the same after 5 attempts, this code will be recorded as a shut-down failure. Boiler will not lockout.
What causes the Remeha B@% fault?
This fault occurs when heat cannot be carried away from the boiler's heat exchanger quickly enough, leading to a rapid and unsafe rise in temperature. The most common reason is a failing internal pump or a blockage in the system pipework that restricts the flow of water. It can also be triggered by a build-up of limescale or sludge within the heat exchanger itself, which prevents efficient heat transfer.
This issue often surfaces during the first cold snap of autumn when the heating is turned on after a long summer break, as pumps can seize or sludge can settle while the system is inactive.
DIY fix possible
Check that all radiator valves are fully openEnsure the central heating bypass valve is openCheck that the boiler pressure is between 1.0 and 1.5 barBleed all radiators to remove trapped air
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Remeha models that show the B@% fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Remeha B@% 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 7 July 2026