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Q: Why does my pump stop working with an Overload OFF(AC out O-A) error?

Step 1: Identify the Specific Error

Look at the message on your inverter's screen to determine which type of overload has occurred:

  • "OFF (Over Load)" (Error E1): This means the solar input power is exceeding the maximum power rating of the inverter.
  • "OFF (AC Out O-A)" (Error E8): This means the AC output to the pump is overloaded.

Step 2: Verify Power Ratings

Check that your inverter is correctly sized for your pump:

  1. Locate the specification sticker on the right-hand side of the inverter and the label on your pump motor.
  2. Ensure the inverter’s rated power is equal to or greater than the pump’s rated power.
  3. Warning: You must not run a pump with a higher power rating than your inverter, as this will cause consistent overload failures.

Step 3: Electrical Troubleshooting (Resistance Test)

If the ratings are correct, you must test the pump and its cable for internal shorts using a multimeter.

How to set up and use your multimeter for this test:

  1. Multimeter Settings: Turn the dial to the Resistance setting, marked with the Omega symbol (). If your meter has ranges, choose a low one like 200 .
  2. Safety: Press the On/Off button to stop the pump, turn off the solar isolator, and wait 5 minutes for the electricity to discharge.
  3. Prepare the Wires: Unplug the AC output plug or disconnect the motor wires (U, V, W, and Ground) from the inverter.
  4. Take Measurements: Touch the metal probe tips to the bare ends of the motor wires in pairs: U to V, V to W, and U to W.

Interpret your results:

  • For Three-Phase Motors: All three readings must be identical. If any reading differs by more than 1 Ohm, the motor or the cable is faulty.
  • For Single-Phase Motors: The readings will be different, but the sum of the two lowest readings must equal the highest reading. For example, if you measure 3.2 and 5.3 , the third reading must be 8.5 . If they differ by more than 1 Ohm, a fault exists.

Step 4: Mechanical Troubleshooting (Check for Jams)

If the electrical tests pass, the overload may be caused by the pump being physically stuck.

  1. Pull the pump out of the water.
  2. Remove the cable cover by undoing the two small screws on the side of the pump body.
  3. Separate the pump head: Use a 13mm spanner to remove the four bolts connecting the pump head to the motor and lift them apart.
  4. Test the Pump Head: Use pliers to turn the impeller shaft. It should spin freely in both directions. If it is jammed or sounds like it is grinding against sand, it may need repair or replacement.
  5. Test the Motor: Turn the motor shaft by hand. It should turn with moderate effort and a smooth, "clunking" magnetic feel. If it feels like it is grinding through sand or is very difficult to turn, the bearings may be damaged.

Step 5: Check Inverter Settings

Ensure the AC Output Max Current (Password: 9579) is set correctly. This should generally be set to 1.5 times the motor's rated current. For example, a 10A motor should have the inverter set to 15A. If it is set too low, the system will trigger an overload error prematurely.

If these steps do not resolve the issue, take photos of the error message and the specification stickers on the Inverter and contact technical support.