Medium Lockout
Fault 51 122 on Worcester Bosch Greenstar CDi Compact

Your boiler has detected that the wrong type of temperature sensor has been installed or configured for your hot water cylinder.

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

Collector temperature sensor type used as cylinder temperature sensor (T2).

What causes this fault?

This fault happens because the boiler’s control board is receiving an electrical signal from a temperature sensor that it doesn't recognize as the correct type for your hot water tank. It usually occurs if the wrong part was fitted during a repair or if the sensor has developed an internal electrical fault that mimics a different component. In some cases, it can also be caused by a glitch in the boiler's internal settings following a power surge.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

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