Solis UN-G-V01 (Alarm 1011) — Grid Under-Voltage
What it means: In Solis's own words, UN-G-V means the grid voltage is lower than the protective value set in the inverter for the selected grid standard. The inverter disconnects and waits, because feeding a collapsed supply is neither safe nor useful. Solis logs it as alarm 1011 and the LCD shows UN-G-V01 or UN-G-V02, which are two thresholds of the same protection. It is a reading about the supply arriving at the inverter's terminals — which is not always the same as the supply arriving at your meter.
Why does Solis show UN-G-V01?
- Genuine low feeder voltage — the normal condition on overloaded and end-of-line Pakistani feeders at peak evening load
- A loose, corroded or undersized AC connection between the meter and the inverter. The Solis manual's remedy for this row is to check connections and the grid switch, and to check the grid voltage inside the inverter terminal
- Wrong grid standard selected, so the inverter is protecting to a threshold that does not match the local supply
- A tripping or high-resistance AC isolator, MCB or connector on the inverter's own circuit
- The inverter's AC voltage sampling out of calibration, which shows as the display and a meter disagreeing
The Pakistan factor
This is the most Pakistani code on the list. On overloaded urban feeders and long rural spurs, evening voltage sag is routine rather than exceptional, and a solar system that works perfectly all afternoon will drop off around the time everyone's ACs and pumps come on. That is the inverter doing its job. The genuinely dangerous variant is the one that looks identical on the screen: an aluminium-to-copper joint, a hand-twisted connection in the AC box, or an undersized service cable that drops voltage only under load. It shows up as low volts at the inverter and normal volts at the meter, and it heats up every evening until something melts. If your neighbours' lights are steady while your inverter reports under-voltage, that is the case you are in — get an electrician to it rather than living with the alarm.
How to fix it (safe to try yourself)
- Read the voltage on the inverter's display and note the time. Under-voltage almost always follows the load curve, so a few days of readings will show whether it is an evening supply problem or something happening at random.
- Measure at a wall socket on the same phase with a plug-in meter at the same moment. If both read low together, the supply is low and the inverter is behaving correctly.
- If your socket reads normal but the inverter reads low, stop and treat it as wiring. A connection that drops voltage under load is a resistive joint, and a resistive joint gets hot. This is the version of UN-G-V that starts fires, and it is not a DIY diagnosis — call a qualified electrician rather than opening the AC box yourself.
- Check whether your own AC isolator or MCB for the inverter is fully on and not partly tripped. Switching an external isolator is fine; opening the distribution board is not.
- Ask your installer to confirm the grid standard is right for the site, to check the AC cable size against the run length, and to torque every AC connection with the supply isolated. The Solis manual restricts the settings menu where grid standards live to fully qualified and accredited technicians — do not go in there yourself.
- Do not ask anyone to simply widen the under-voltage limit to make the alarm stop. The manual's User-Def range for UN-G-V1 is 170–210 V and for UN-G-V2 is 110–210 V, and any change inside that range needs your electricity company's agreement. The protection exists because running your house on a badly sagging supply damages motors and compressors long before it damages the inverter.
- If the wiring is sound, the supply measures normal, and UN-G-V still latches, that points at the inverter's own measurement. Note the model, serial number, firmware version and grid standard — Solis asks for exactly those — and go to the service centre. Do not open the unit.