Warning What does this mean?
Your system is down or running degraded, but this is not an immediate safety danger. Work through the safe steps below.
Fronius Inverter Code 223 — Undervoltage on L2 Explained
Fronius code 223 means "Undervoltage at L2-N": the inverter measured the voltage between line 2 and neutral below its permitted limit and paused grid feed-in. It is a class 2 status code — temporary by design. The inverter keeps testing grid conditions and resumes automatically once the voltage on L2 is back in range. Check your grid connections, and call your installer if the code keeps coming back.
What should I do first?
Two quick questions — we'll point you to the right starting point.
Is this code still showing on your inverter's display?
Is your system producing power right now?
What this code means
Fronius organizes its status codes into classes, and class 2 is the "wait it out" class: grid-side conditions the inverter watches until they normalize. The official Fronius Operating Instructions for the Primo 208-240 list the family plainly — 212 "Overvoltage at L1-N," 213 "Undervoltage at L1-N," 222 "Overvoltage at L2-N," and 223 "Undervoltage at L2-N." Your code is the last of those: the second line of your split-phase or three-phase supply sagged too low. The documented behavior is reassuringly boring: "Grid conditions are being tested and as soon as they are back within the permissible range, the inverter will resume grid power feed operation."
A quick note on a common confusion: some third-party error-code websites describe 223 as an overvoltage fault. The official Fronius documentation says otherwise — 223 is undervoltage on L2, full stop. Trust the manufacturer's table over aggregator sites; the overvoltage sibling is 222.
Why would one line sag while the others behave? On a split-phase 208–240V supply, heavy single-sided loads — a large air conditioner, a well pump, an EV charger pulling hard on L2 — can drag that leg down momentarily. Loose or corroded connections add impedance that turns normal current into abnormal voltage drop. And sometimes it is simply the utility: a sagging feeder, a switching operation, or a fault elsewhere on the network. The L2-N specificity is actually useful diagnostic information — it tells your installer exactly which leg to investigate, rather than waving at "the grid" generally.
What is this downtime costing you?
Rough estimate while your system isn't producing. Adjust the numbers to match your setup.
≈ – kWh of lost production per day.
Estimate only — assumes ~80% real-world output vs. nameplate. Actual losses depend on weather, shading, panel direction, and your tariff.
Common causes
- A heavy 120V load on the L2 leg (air conditioning, well pump, EV charger) dragging that phase down.
- A loose, corroded, or overheated connection on the L2 conductor at the inverter, disconnect, or panel.
- Utility-side voltage sag on one leg from feeder issues or network switching.
- Undersized or long AC conductors causing excessive voltage drop under load.
- A failing L2 breaker or disconnect with high internal resistance.
- Incorrect country/grid-code setup applying the wrong undervoltage threshold (rare).
Safe steps to try
Work top to bottom, ticking off each step as you complete it. 0 of 5 done.
Is your inverter still under warranty?
Before paying for a repair, check — your installer may fix this free.
Based on typical standard warranty terms — always confirm with your warranty card or installer paperwork, as terms vary by model, region, and purchase date.
When to call an electrician
Contact your installer if code 223 recurs frequently, appears with no heavy loads running, or is joined by flickering lights or warm/burning smells at the panel (call immediately in that case). Fronius's official rectification for this code is: check grid connections, and if the status code keeps recurring, contact your system installer. The installer can measure L2-N voltage under load, inspect and re-torque connections, and verify the country setup.
Frequently asked questions
Is 223 an overvoltage or undervoltage code?
Undervoltage — specifically "Undervoltage at L2-N" per Fronius's official operating instructions. Some third-party sites mislabel it as overvoltage; the overvoltage code on the same line is 222.
Will the inverter restart on its own?
Yes. Code 223 is a class 2 status: the inverter continuously tests grid conditions and resumes feed-in automatically once L2 voltage is back within limits. No reset needed.
My air conditioner was running when 223 appeared. Related?
Very likely. A big single-leg load can sag L2 enough to trip the undervoltage monitor, especially with long or undersized conductors. If it only happens with that load running, mention it to your installer — the fix may be wiring, not the inverter.
How is 223 different from code 103?
Code 103 is the general "AC voltage too low" class 1 status for the whole supply; 223 is the per-line variant pinpointing L2-to-neutral specifically. Class 1 codes are broader grid events; class 2 codes like 223 are line-specific monitoring trips.
Need a professional?
This fault may need professional diagnosis. Contact a qualified solar electrician in your area.
Sources: meaning and troubleshooting verified against the manufacturer's documentation — Fronius Operating Instructions, Fronius Primo 208-240 (doc 42,0410,2116), official Fronius documentation — Class 2 status codes: 212 = "Overvoltage at L1-N", 213 = "Undervoltage at L1-N", 222 = "Overvoltage at L2-N", 223 = "Undervoltage at L2-N"; behavior: grid conditions tested, feed-in resumes automatically when back in range; rectification: check grid connections, contact installer if recurring.