Medium Lockout
E50 on Potterton Gold HE

Your boiler's hot water temperature sensor has developed a fault, meaning the system cannot accurately measure or provide hot water.

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 internal sensor responsible for monitoring your hot water temperature fails or sends an incorrect signal to the main control board. The most common reason is that the sensor has physically degraded over time or developed a lime-scale coating, preventing it from reading the water temperature accurately.

Engineer required

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

Find a Gas Safe engineer
Search the official register →

Related fault codes

E20View →E28View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →