A solar pump inverter that keeps tripping is almost always protecting something: the pump, the motor, or itself. The five usual causes are overload, a short or earth fault, overheating, voltage outside the working range, and dry running. Work through them in order, and never defeat a protection to keep the pump running.
What
Tripping is the inverter cutting output and showing a fault code instead of letting a bad condition damage the motor or the machine. A single trip after a storm is a nuisance; trips that return every day are a symptom with a cause that will not fix itself.
Why
Each protection exists for a failure that costs real money: dry running burns a pump, overload overheats a motor, a short circuit damages windings and wiring. The trip is the cheap event; the damage it prevents is the expensive one.
When
Trips at midday in hot weather point to heat or overload; trips at dawn or in cloud point to voltage at the edge of the MPPT window; trips the moment the pump starts point to a wiring or pump fault. Note the time of day and the code before resetting, because the pattern is the diagnosis.
Where
Trips happen most on remote or unattended sites, where nobody sees the first warning. The won’t-start troubleshooting flow sets out the same check order for a pump that will not start at all, and the fault-code article explains what each code means.
How
- Write down the fault code and the time of day before touching anything.
- Check the easy causes first: is the water source low, are the vents blocked, is the cabinet hot to the touch?
- Check the panel string voltage is inside the MPPT window, using the MPPT window article’s method.
- Check the pump is not jammed and the wiring shows no heat marks or damage; switch off and isolate before opening anything.
- Reset once, and only once: if the same trip returns, stop resetting and work the fault-code table instead.
- If the code points to a short circuit, an earth fault or a pump fault, send the code, the pump nameplate data and photos of the wiring for a service check.
Cause, clue, first check
| Cause | Clue | First check |
|---|---|---|
| Overload | Trips under full sun at midday | Pump duty against inverter rating, using the sizing article |
| Short or earth fault | Trips the instant the pump starts | Wiring and motor insulation, with power isolated |
| Overheating | Trips on hot afternoons, cabinet hot | Vents, fan, shade, and cabinet seals |
| Voltage out of range | Trips at dawn, in cloud, or at noon | String voltage against the MPPT window |
| Dry running | Trips with low source level | Water level, level sensor, and dry-run protection setting |
Reset or stop
| What happened | Sensible call |
|---|---|
| One trip after a storm, code clears, pump runs normally | Monitor, note it in the log |
| Same trip twice in a day | Stop resetting, work the fault-code table |
| Trip with burning smell, heat marks, or a short-circuit code | Switch off, isolate, and call for service |
| Trip that returns every hot afternoon | Check cooling and sizing before the next dry spell |
Frequently Asked Questions
Is it safe to keep resetting a tripping inverter?
No: one reset to clear a nuisance trip is fine, but repeated resets hide a fault that is getting worse.
Can a bigger array stop the tripping?
Only if the cause is low voltage in weak light; it does nothing for overload, heat, or a pump fault.
Why does it trip only in the afternoon?
Heat builds through the day, and a hot cabinet plus full load is when overload and over-temperature protections act.
If I switch off dry-run protection, will the tripping stop?
The trips may stop, but the pump can then run dry and burn out, which is the damage the protection exists to prevent.
When must I call for service instead of checking myself?
For any short-circuit or earth-fault code, any burning smell or heat marks, or any trip that returns after one reset.
To get a tripping diagnosis for the QB100 PV Solar Pump Inverter, send the fault code, the time-of-day pattern and the pump nameplate data.