When a solar pump inverter will not start, work from the symptom first, not from a guess: check whether the display is alive, whether PV voltage is in range, and whether the pump is being asked to run at all. Most no-starts are a power, signal or protection problem, not a failed drive, and the fault code only narrows the cause after those three checks.
Before you touch anything: the safety boundary
Isolate the PV and mains supplies before opening terminals, and treat the DC bus as live until a qualified electrician has discharged and verified it. Never megger-test a motor while it is still connected to the drive, and never bypass a protection input to force a start. If you are not qualified for DC work, stop at observation and call for service.
How to troubleshoot, step by step
- Record the phenomenon. Note exactly what happens: no display, display with no run, run then immediate trip, or running with no water.
- Read the code. Write down the exact fault code and the conditions at the time: sun level, water level and whether the pump had just been stopped.
- Check PV power. Compare measured DC voltage with the model’s recommended range. For the IDEEI IP65 solar pumping VFD, the 220 V branch recommends DC 200-400 V with an MPP of 330 V, and the 380 V branch recommends DC 300-750 V with an MPP of 550 V. Below the start range, the drive may correctly refuse to run.
- Check the run command. Confirm the start signal, remote or auto mode, and any water-level or pressure switch that could be holding the pump off.
- Check the pump load. A dry well, a blocked intake or a seized pump can trip dry-run or overload protection. Confirm water availability before suspecting the drive.
- Match code to cause, then act once. Use the table below, fix the identified cause, and only then reset.
- Test under load and watch the first run. Confirm current, pressure or flow and that the fault does not return within the first minutes of operation.
Phenomenon, code, cause and action
| Phenomenon | Fault family | Likely cause | Action |
|---|---|---|---|
| No display, nothing happens | None shown | No PV or supply power, blown fuse or loose DC connection | Check supply, fuses and terminations with the system isolated; confirm DC voltage is in range |
| Display alive, pump never runs | None, or start inhibited | Missing run command, low water level, or auto/manual mode mismatch | Confirm start signal, mode and level switches before changing drive settings |
| Starts, then trips at once | OC, OV or UV | Overcurrent from a blocked or seized pump, overvoltage from PV, or undervoltage at low sun | Clear the load or PV cause first; do not raise limits to force a start |
| Runs but delivers no water | Dry-run protection | Well level low, intake blocked, or air in the pump | Confirm water source and priming; check the dry-run setting against the manual |
| Trips after running a while | OL or OH | Overload or overheat from blocked airflow, high ambient or an overloaded pump | Clear heatsink airflow, reduce load where possible, and check the motor current |
| Earth or insulation trip | GF | Damaged cable, wet junction box or motor insulation fault | Isolate and call a qualified electrician; never megger-test with the motor connected to the drive |
Exact code labels vary by model and manual, so use the generic families OC, OV, UV, OL, OH and GF only as a starting map. The Solar Pump Inverter Fault Codes and Dry-Run Protection article explains the solar-specific codes, and VFD Troubleshooting: Fault Codes and What They Mean covers the wider VFD families. For a drive that must survive outdoors while it is being diagnosed, the IP65 solar pumping VFD (0.4-37 kW, MPPT) and the cabinet-based QB100-PV solar pump inverter are the two product lines to compare.
Reset or repair: where the boundary sits
| Situation | Reset | Repair or service |
|---|---|---|
| One trip, cause found and fixed | Yes, after fixing the cause and checking the first run | No, if the run stays stable |
| Same fault returns after a reset | No further resets | Yes, the cause is still present or the drive or motor needs testing |
| Burning smell, damaged cable or wet junction box | No | Yes, isolate and call a qualified electrician |
| Fault code cannot be identified in the manual | No | Yes, send the exact code, model and conditions with the inquiry |
Frequently asked questions
Will repeatedly resetting the fault eventually fix it?
No, and this is the trap. A reset clears the trip, not the cause. If the same fault returns, each reset risks more stress on the pump and drive. Find and fix the cause, then reset once and watch the first run.
Why does the pump not start on a cloudy morning?
Because PV voltage or power may be below the start range. That is normal protection behaviour, not necessarily a fault. Check measured DC voltage against the model’s recommended range before changing settings.
The display is dead. Is the drive faulty?
Not necessarily. A dead display most often means no usable supply: check PV input, fuses and DC terminations with the system isolated before concluding the drive has failed.
Can I megger-test the motor to check for a fault?
Only with the motor disconnected from the drive, and only if you are qualified. Never megger-test a motor while it is still connected to the drive, because the test voltage can damage the drive.
What should I send with a repair inquiry?
The exact fault code, the phenomenon in order, measured DC voltage, water-level state, pump model and power, and whether the fault returns after one reset. That list lets support distinguish a site problem from a drive problem.
Send the phenomenon, the exact code and the conditions at the time of the trip with your inquiry, and state clearly whether the fault returns after a single reset. That one sentence saves a round of guessing.