E25
Himoinsa Synchronization Failure (Voltage/Frequency/Phase Mismatch)

The generator controller displays E25, and the unit will not synchronize or close the breaker in parallel applications.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Incorrect synchronization parameters in the controller, a faulty sync check relay, inaccurate voltage or frequency sensing, or a communication error between Himoinsa controllers.

How to Fix / Troubleshooting

Safety: Parallel operation involves complex protections. Only qualified personnel should adjust synchronization settings.

  • Verify sensing: Confirm that voltage and frequency readings for both the bus and the generator are accurate on the controller. Check VT/CT wiring.
  • Check synchronization settings: In the controller, verify permissible voltage, frequency, and phase angle windows for synchronization. Adjust to Himoinsa recommended values.
  • Test sync check relay: If a separate relay is used, test its operation with a simulator or test set. Replace if faulty.
  • Communication: Ensure CANbus or other communication links between Himoinsa controllers are intact and correctly terminated.
  • Test synchronization: Attempt a manual synchronization under supervision, monitoring phase angle and breaker closure. If E25 persists, consult Himoinsa technical support.
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Repair Difficulty

Professional Required 5/5

Required Part

Sync Check Relay
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