Danfoss Error 1027

If you work with industrial automation or commercial HVAC, you have likely seen the green display of a Danfoss drive flash an alarming code: Alarm 1027. Unlike simple overvoltage or overcurrent faults, Error 1027 points to something more elusive: the communication network.

Danfoss drives (including the popular VLT® HVAC Drive, VLT® AutomationDrive, and VACON® series) rely on robust fieldbus communication for speed reference, start/stop commands, and feedback. When Error 1027 appears, the drive is essentially saying, "I cannot hear the master controller." Ignoring this fault can shut down a production line, freeze a chiller plant, or halt a conveyor system.

This article provides a deep technical dive into Danfoss Error 1027. We will cover what it means, its common causes, step-by-step diagnostic procedures, and both field-level and long-term solutions. danfoss error 1027

From the PLC or network scanner:

Locate the option card (left side of the control card on VLT units). Interpret LEDs: If you work with industrial automation or commercial

| LED State | Meaning | |-----------|---------| | Steady green | Normal data exchange | | Flashing green | No configuration / waiting for master | | Red flashing | Timeout or bus error | | Steady red | Option card failure or hardware fault | | Off | No power or card not detected |

For Profinet (MCA 101): Flashing green on BF (Bus Fault) indicates Error 1027. From the PLC or network scanner: Locate the

For EtherNet/IP (MCA 104): Red “Mod” LED means network timeout.

The problem isn’t the drive — it’s the PLC. If the master stops sending cyclic I/O due to a program crash, power loss, or halted scanner task, all slave drives will log 1027 simultaneously.

If the master resumes cyclic communication before the timeout time expires, the drive may auto-clear the alarm (depending on Parameter 8-07 Diagnosis Trigger).

Follow this field-tested workflow. It assumes you have a multimeter, a laptop with Danfoss MCT-10 or VACON® NCDrive, and physical access to the drive.