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

Generator controller displays E25 and the unit will not synchronise or close 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 sync parameters in controller, Faulty sync check relay, Inaccurate voltage or frequency sensing, Communication error between Himoinsa controllers

How to Fix / Troubleshooting

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

  • Verify sensing: Confirm that voltage and frequency readings for both bus and generator are accurate on the controller. Check VT/CT wiring.
  • Check sync settings: In the controller, verify permissible voltage, frequency, and phase angle windows for synchronisation. 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 synchronisation: Attempt a manual sync 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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