F1
Drazice
External Heat Source Sensor / Communication Fault
Drazice combined electric/indirect water heater shows F1; boiler or external heat source is not recognized.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Faulty boiler temperature sensor on coil, broken sensor wiring, incorrect connection to boiler control terminals, misconfigured control board settings
How to Fix / Troubleshooting
Safety: Isolate both the water heater and the boiler from mains power before working on control wiring.
Steps:
- Locate the sensor used to monitor the boiler or heating circuit temperature (often attached to the coil return pipe or inserted into a well).
- Check wiring continuity from the sensor to the Drazice control board; repair any breaks or loose terminals.
- Measure sensor resistance and compare with the specified NTC curve; replace if defective.
- Verify that control wiring between the boiler and the Drazice heater (e.g., thermostat contacts) is correctly connected as per the wiring diagram.
- Enter the installer menu (if available) and confirm that the external heat source function is enabled and configured correctly.
- Restore power and check if F1 clears.
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Repair Difficulty
Hard
4/5
Required Part
Boiler Circuit Temperature Sensor
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