The W03 fault is probably one of the more confusing warnings you’ll come across on a Deye or Sunsynk inverter. At first glance, “Grid Phase Wrong” sounds like the incoming phases have simply been connected incorrectly, but that’s not always the case.
I’ve personally seen this fault caused by more than one issue, so it’s important not to jump straight to swapping phases around. A few simple checks first can save you a lot of unnecessary work.
TheW03 fault is the inverter is basically telling you that it isn’t happy with the grid supply it’s seeing. This could be because the phase sequence is incorrect but it can also be caused by other grid related problems that prevent the inverter from synchronising correctly.
1. Confirm the incoming phase rotation
If you’re working on a three-phase inverter, this is always the first thing I’d check.
Using a phase rotation meter, confirm that the incoming supply has the correct phase sequence. If the utility supply itself has the wrong rotation, the inverter will quite rightly refuse to synchronise.
If the supply is correct, move on to the inverter settings before changing any wiring.
2. Check the inverter phase rotation setting
This is one I’ve personally come across before.
Some Deye and Sunsynk models allow the phase rotation to be configured within the inverter settings. If this doesn’t match the actual supply, the inverter can generate a W03 warning even though the incoming grid is perfectly healthy. Before moving any cables around, double check this setting.
3. Check the grid voltage
Low grid voltage can also cause synchronisation problems. If one phase is significantly lower than the others, or outside the inverter’s acceptable operating range, the inverter may refuse to connect and generate grid related warnings. Measure your phase-to-phase voltages and phase-to-neutral voltages, if any of these values are outside of the inverters low or high accepted grid voltages, this can trigger a W03 Phase Rotation fault.
4. Inspect the AC wiring
It’s also worth checking the basics as this could be a cause of bad incoming grid voltages. A low voltage may not really be from your utility supply but rather on a connection point somewhere between your main supply point and the inverter itself.
Look for loose terminals, incorrect phase connections, damaged breakers or high resistance joints. These faults can all create strange grid behavior that may lead to synchronisation problems.
If I arrived on site with a W03 fault, I’d normally work through it in this order:
- Verify the incoming phase rotation.
- Check the inverter’s configured phase rotation.
- Measure all three phase voltages.
- Check the grid frequency.
- Inspect the AC wiring and terminations.
- Review the inverter event history to see when the warning first appeared.
Working through the fault logically is much quicker than immediately swapping phases and hoping the warning disappears.