SMA Sunny Boy Error Code 3901

SMA PLC & VFD Minor DC Input

Model: Sunny Boy | Code: 3901

Applicable Systems
Sunny Boy

Symptoms

Waiting for DC start. The inverter is waiting for the PV DC voltage to reach the minimum start voltage beforebeginning MPPT.

Possible Causes

  • PV voltage below minimum start voltage due to low irradiance
  • PV array too small for inverter DC start threshold
  • PV string partially shaded reducing voltage below start threshold
  • Inverter DC start voltage parameter set too high

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code 3901 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: Check the system diagnostic buffer or event log for detailed fault information
    Diagnostic buffer shows the specific fault cause and timestamp
  4. Step 4: Verify power supply stability and environmental conditions
    Power supply stable, environment within specifications
  5. Step 5: Restart the equipment or power-cycle the control system
    Equipment restarts and enters normal operating state
  6. Step 6: Contact manufacturer support if the fault persists after all checks
    Support provides specific troubleshooting guidance

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 3901 mean on the SMA Sunny Boy?

    Fault 3901 on the SMA Sunny Boy indicates: Waiting for DC start. The inverter is waiting for the PV DC voltage to reach the minimum start voltage before beginning MPPT. Refer to the equipment manual and manufacturer support for specific troubleshooting steps.

  • Q: Can I continue operating the equipment with fault 3901 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