Display shows F15 and unit reports internal memory error

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.

Possible Causes

Corrupted configuration data, Power surge damage, Control board hardware failure

Safety first: This is an electronic fault; do not open hydraulic components.

Power cycle: Disconnect power for at least 5 minutes, then reconnect. Check if F15 clears.
Factory reset: If allowed by the manual, perform a factory reset and re-enter all commissioning parameters.
Surge protection: Ensure the softener is connected through a surge-protected outlet to prevent future damage.
Board replacement: If F15 persists after reset, the Viessmann control board will likely need replacement by an authorized service technician.

Hard 4/5

Viessmann Control Board

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