Display shows E15, unit may not respond to external demand (e.g., BMS or room thermostat)

Safety: Low-voltage control circuits still require power isolation before modification.

• 1. Verify demand signal: Check that the external thermostat or BMS is actually calling for heat (contacts closed or correct voltage present).
• 2. Check wiring: Compare the wiring to the ACV terminal strip with the installation manual. Ensure the correct terminals are used and that any required links are in place.
• 3. Test with link: Temporarily bridge the demand terminals on the ACV control board (if allowed by the manual). If the unit starts, the external control or wiring is faulty.
• 4. Parameter check: In the installer menu, verify that the control mode is set correctly for external thermostat or BMS operation.
• 5. Replace faulty control: If the thermostat or BMS output is defective, replace or repair it.

If E15 persists with correct wiring and configuration, the control board input may be damaged and require replacement.