Is your Danfoss VFD showing Err 84? Learn how to fix the Local Control Panel (LCP) communication error on VLT FC51, FC101, and other models with our expert guide.
Danfoss Drive Err 84 or Error84 indicates LCP Communication Lost. This means the Local Control Panel (LCP)—the keypad or display unit—has lost its data link with the main control board of the frequency converter.
Danfoss Drive Troubleshooting: Err 84
Fault No. – Err 84
Standard Message: LCP Communication Lost
In the world of Danfoss VLT drives, Err 84 is a very specific communication error. It indicates that the Local Control Panel (LCP)—the keypad or display unit—has lost its data link with the main control board of the frequency converter. When this happens, you lose the ability to monitor or control the drive through the physical interface.
Common Causes of Err 84
- Physical Disconnection: The LCP is not seated properly in its cradle or the mounting screws have loosened over time due to vibration.
- Faulty Connection Cable: If the LCP is remote-mounted, the serial cable (RS485) between the drive and the panel may be pinched, cut, or corroded.
- Baud Rate Mismatch: The communication speed (baud rate) or protocol settings on the LCP do not match the drive’s internal settings.
- Electrical Noise (EMI): High-frequency interference from nearby power cables can disrupt the low-voltage communication signal to the display.
- Firmware Bug: Specifically on the FC 101 series, certain older firmware versions are known to trigger Err 84 when specific parameters are changed.
Step-by-Step Solutions
- 1. Reseat the Keypad: The most common fix. Remove the LCP entirely from the drive, check for dust or bent pins on the connector, and snap it back into place firmly.
- 2. Inspect Remote Wiring: If your display is on a cabinet door, check the cable continuity. Ensure the cable is shielded and the shield is properly grounded.
- 3. Perform a “Two-Finger” Initialization: To reset communication parameters:
Procedure: Power off the drive. Press and hold the [Status] and [Main Menu] (or [OK] + [Menu] depending on model) buttons simultaneously while powering the drive back up. This initializes the drive to factory defaults (Note: Back up parameters first if possible). - 4. Try a Different LCP: If you have a second identical drive, swap the keypads. If the error moves with the keypad, the LCP is faulty. If the error stays with the drive, the control board’s port is damaged.
Expert Tip for FC 101 Users: If you are running firmware V2.90 and see Err 84, it is a documented defect. The ultimate solution is upgrading the firmware to V2.93 or higher.
Applicable Models
This error is most frequently reported in the following series:
VLT® Micro Drive FC 51VLT® HVAC Basic Drive FC 101VLT® AutomationDrive FC 301/302VLT® AQUA Drive FC 202