Main Circuit Undervoltage

What does uU mean?

This warning indicates that the DC voltage of the main circuit has dropped below its low-voltage detection level while the Inverter is stopped. This typically points to an issue with the incoming power supply or its connection to the inverter. Prolonged undervoltage can prevent proper inverter startup or operation.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Verify that the terminal block screws for the power input are securely tightened to ensure good electrical contact.