Vaillant smart thermostat shows F.17 and reports that maximum number of devices or zones has been exceeded.

Safety: Configuration only; no electrical work.

• 1. Check controller capacity: Refer to the Vaillant manual for the maximum number of zones and devices supported by your thermostat or system controller.
• 2. Remove unused devices: In the device management menu, delete any old or unused room units, sensors, or actuators.
• 3. Re‑assign zones: Ensure each room unit is assigned to only one zone and that there are no duplicate assignments causing conflicts.
• 4. Split system if needed: For very large installations, consider using an additional Vaillant controller to split zones, following Vaillant’s design guidelines.
• 5. Reset and re‑pair: If conflicts persist, factory reset the controller and re‑pair devices one by one, checking for F.17 after each addition.