SMA Sunny Boy Error Code 401

SMA PLC & VFD Major Grid

Model: Sunny Boy | Code: 401

Applicable Systems
Sunny Boy

Symptoms

Grid frequency out of range. The grid frequency is outside the allowed range (typically 47.5-51.5 Hz for 50Hz grids).

Possible Causes

  • Grid frequency from utility outside standard range
  • Grid instability from high renewable penetration
  • Grid generator frequency regulation fault
  • Inverter frequency measurement circuit calibration error

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code 401 as active
  2. Step 2: Verify all electrical connections, wiring harnesses, and connector seating
    All connections secure, no corrosion, loose pins, or damaged wires
  3. Step 3: Measure the input power supply voltage at the equipment terminals with a multimeter
    Voltage reading is within the equipment's specified operating range
  4. Step 4: Inspect the power input wiring, breakers, and fuses for damage or degradation
    Wiring intact, breakers closed, fuses continuous
  5. Step 5: Check for transient voltage events or power quality issues using a power analyzer
    No sustained overvoltage, undervoltage, or phase imbalance detected
  6. Step 6: Reset the fault after correcting the power issue: fix root cause, then press RESET or power-cycle
    Fault clears and equipment resumes normal operation

How to Reset

To reset: 1) Identify and fix the root cause described in the fault symptoms. 2) Press RESET on the HMI or controller, or power-cycle the equipment. 3) If the fault recurs, contact manufacturer service. Caution: Document the fault code and context before resetting.

Frequently Asked Questions

  • Q: What does fault code 401 mean on the SMA Sunny Boy?

    Fault 401 on the SMA Sunny Boy indicates: Grid frequency out of range. The grid frequency is outside the allowed range (typically 47.5-51.5 Hz for 50 Hz grids). Refer to the equipment manual and manufacturer support for specific troubleshooting steps.

  • Q: Can I continue operating the equipment with fault 401 active?

    No. The equipment has detected a fault condition and has taken protective action (typically stopping or derating). Continuing to operate without fixing the root cause may cause further damage. Always investigate and fix the fault before resuming operation.

Related SMA Fault Codes

Source: SMA Sunny Boy Inverter Installation and Operation Manual, SMA Official Documentation

Category: PLC & VFD