Huawei SUN2000 Error Code 121

Huawei PLC & VFD Critical DC Input

Model: SUN2000 | Code: 121

Applicable Systems
SUN2000

Symptoms

PV input short circuit detected. The inverter has detected a short circuit condition on the PV input. The DCinput protection activates to prevent damage to the inverter and PV array.

Possible Causes

  • PV cable insulation damage causing short between positive and negative conductors
  • Water ingress in PV junction box causing internal short
  • PV connector (MC4) cross-threaded or damaged causing short
  • PV module bypass diode failure causing internal short

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code 121 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 121 mean on the Huawei SUN2000?

    Fault 121 on the Huawei SUN2000 indicates: PV input short circuit detected. The inverter has detected a short circuit condition on the PV input. The DC input protection activates to prevent damage to the inverter and PV array. Refer to the equipment manual and manufacturer support for specific troubleshooting steps.

  • Q: Can I continue operating the equipment with fault 121 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 Huawei Fault Codes

Source: Huawei SUN2000 Series Inverter User Manual, Huawei Official Support (support.huawei.com)

Category: PLC & VFD