F7 displayed, heater does not start or shuts down, flow temperature reading is incorrect

Safety first: Isolate power and allow the appliance to cool fully before touching the heat exchanger or pipes.

• Locate primary NTC: Identify the flow temperature sensor on the primary heat exchanger or flow pipe.
• Check mounting: Ensure the sensor is firmly clipped or inserted into its pocket and making good contact with the metal surface.
• Inspect cable and connector: Look for signs of overheating, moisture, or mechanical damage. Reseat the connector at both the sensor and PCB ends.
• Test sensor: Measure resistance and compare with Protherm's NTC table. Replace if readings are out of specification.
• Dry moisture: If condensation has entered the connector, dry it thoroughly and correct any cause of water ingress.

Warning: Do not operate the heater with the flow sensor disconnected; overheating and damage to the heat exchanger may occur.