Medium
Block 11 on Atag A200

Your boiler is overheating because the water is not flowing through the system quickly enough to take the heat away.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Maximum ΔT of flow and return sensor in central heating has repeatedly been exceeded. During the block normal operation of the hot water supply is possible. The pump continues to operate at minimum capacity during the block.

DIY fix possible

Check that all radiator valves are fully open including the lockshield valvesEnsure there are no blockages in the magnetic system filter if one is fittedCheck that the boiler pressure is between 1.0 and 1.5 bar

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