Medium Lockout
E50 on Potterton Promax Combi HE Plus

Your boiler's hot water sensor has malfunctioned, meaning the system can no longer accurately measure the temperature of the water coming out of your taps.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

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

Hot Water NTC Fault

What causes this fault?

This fault occurs when the thermistor responsible for measuring your hot water temperature has failed or is sending an incorrect electrical signal to the control board. The most common reason is that the sensor has either degraded over time due to heat stress or has developed a small internal short circuit. This prevents the boiler from knowing how hot the water is, causing it to stop heating for safety reasons.

Engineer required

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

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Related fault codes

E20View →E28View →

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