F8
FAULT CODE
Ideal
Flow Thermistor - Out of Range High
High Severity
Engineer Required
The flow temperature sensor is reading higher than its maximum expected value, indicating a sensor fault or extremely high temperature.
Step-by-Step Fix Guide
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Step 1
Do not try to continue operating the boiler
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Step 2 Engineer only
Call a Gas Safe engineer to test the flow thermistor
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.