Inverex Nitrox Fault Codes 2026: Technician’s Complete Decode List for F01 to F64

Inverex Nitrox Fault Codes 2026: Technician’s Complete Decode List for F01 to F64

One evening, a shop owner called me. His Inverex Nitrox had stopped sending power to the grid. The screen showed F35. He had already turned the inverter off and on three times. The code came back each time. He asked me one simple question. Is my inverter dead, or is this a small problem?

This guide answers that question for every Nitrox code. You will learn what the F-codes on an Inverex Nitrox on-grid inverter mean. You will learn which codes point to the grid, which point to your solar panels, and which point to a fault inside the inverter. You will also learn the safe first check for each group, and when you must stop and call a technician.

This guide is for home owners and for repair technicians. A home owner will learn what to check without opening the inverter. A technician will get the full decode list in one place, with the manual meanings for F01 to F64. At the end, you will get a short checklist. You can use it the next time any code shows up on the screen.

Trust nudge: SunTech Mall runs its own inverter and UPS repair service center. Every day, we open inverters with fault codes like these. We test them. We fix them. So what you read here comes from real bench work and from the official manual, not from guesses.

What You Will Learn in This Guide

• How to read a Nitrox F-code, and why you must never mix it up with other brands’ codes
• The full decode list for F01 to F64, in plain words
• What F35, F36 to F48, F55, F56 and F64 really mean, and what to do first
• How to shut down and restart a Nitrox inverter in the safe way
• When you can check it yourself, and when you must call a technician
• Which parts technicians check for these faults, and where to find them

First, Read This: Nitrox Codes Are Not the Same as Other Inverex Codes

Many people mix up two code systems, and that mix-up leads to a wrong fix. Some older Inverex hybrid inverters use plain numbers, like 01, 02, 07 or 09. Those numbers mean fan, heat, battery or bus faults on that family. The Nitrox on-grid string inverter uses a different system. Its codes start with the letter F, like F35, F36 or F55.

Do not use a plain-number table for a Nitrox F-code, and do not use a Nitrox F-table for a hybrid inverter. A wrong table leads to a wrong part. This guide only uses the F-code family from the Nitrox three-phase string inverter manual. That manual covers the Nitrox 12, 15, 20 and 25 kW three-phase string models.

Note: Codes can change a little from one model to another, and with firmware. Firmware is the built-in software inside the inverter. The Nitrox 6 kW three-phase on-grid model sold by SunTech Mall belongs to the same on-grid family, but before you make a big choice, match the code with the fault table in your own manual. If your code does not match the table below, do not guess. Take a photo of the screen and ask a technician.

How to Read a Nitrox Code

When a fault happens, the LCD screen shows an alarm message. The inverter may stop feeding energy into the grid. That stop is a safety step, not a punishment. The inverter stops so that a bad grid, a bad panel string, or a bad part inside cannot cause more harm.

When you note a code, do not just write the number. Also write these five facts. First, the exact model and size of your inverter. Second, the code on the screen, plus the colour and state of the LED lights. Third, what the grid was doing at that time. Was the power off? Was the voltage low? Fourth, what the weather was like. Was it very hot, or was there a storm? Fifth, what changed just before the fault. Did you add panels? Did a breaker trip?

These five facts help a technician a lot. In our workshop, these are the first five questions we ask for every Nitrox fault. A photo of the screen, taken before you restart, is worth more than a long story after you restart.

Bonus Tip: Before you restart, take a photo of the code and the LED lights. Note the time, the load, and the grid state. When you show this photo to a technician, the problem becomes much easier to understand.

Quick Triage: Three Groups, Three Different First Moves

Every Nitrox F-code falls into one of three groups. If you know the group, you know the first move.

Group 1: Grid codes. These codes say the grid is outside its normal range, or a phase is missing. Examples are F35, F36, F37, F38 and F41 to F48. The first move is to check the grid itself, not the inverter. If your neighbours also have a problem, the grid is the likely cause. Wait for the grid to come back to normal, then restart once in the safe way.

Group 2: Solar panel and DC codes. These codes say something is wrong on the DC side, the solar panels, the wiring, or the earth. Examples are F01, F02, F03, F23, F24 and F55. The first move is to check the outside wiring only, and only when it is safe. Never touch live DC wires. If a code in this group keeps coming back, a qualified installer must check the strings and the earthing.

Group 3: Inside codes. These codes say a part inside the inverter has failed, or the control system cannot work right. Examples are F09, F11, F12, F19, F30 and F64. The first move is simple. Keep the inverter off and call a technician. Do not keep restarting. Each restart puts stress on the board.

Full Decode List: F01 to F64

The table below gives the manual meaning for every Nitrox string-inverter code, in plain words, with the first thing to do. More detail on the most common codes comes after the table.

From this table, you can tell at once where to look first. Grid codes mean you look at the grid. DC codes mean you look at panels, wiring and earthing. Inside codes mean you stop and hand the job to a technician. That one habit saves a lot of wrong parts and wasted money.

F35: No AC Grid — The Code People Ask About Most

F35 means the inverter cannot find the AC grid. In plain words, the grid power is gone, or the inverter cannot connect to it. This is the most common code on an on-grid inverter, and it is often not a fault in the inverter at all.

Here is what to check first. Is there a power cut in your area? Is the AC breaker for the inverter tripped? Is one phase missing? On a three-phase system, a lost phase can stop the inverter even when some lights in the house still work. The manual troubleshooting table also links F35 to a grid failure, so start with the grid, not with the board.

What should you do? First, check the main breaker and the inverter AC breaker. Then check if your neighbours have power. If the grid is down, wait. Do not keep restarting. When the grid comes back to normal, restart once in the safe way, as shown below. If the grid is fine but F35 keeps coming back, a qualified installer must check the AC wiring and the grid connection. A loose AC wire or a lost phase is an installer job, not a guess job.

A lived line from our workshop: most F35 calls we get after a storm end with one answer. The grid was the problem, and the inverter was doing its job by staying off. An on-grid inverter must stay off when the grid is gone. That rule keeps line workers safe, and it keeps your system safe.

F36, F37 and F38: Phase Problems on a Three-Phase Inverter

A three-phase Nitrox must see three healthy phases. F36 means an AC grid phase error. F37 means the three-phase voltage is not balanced. F38 means the three-phase current is not balanced. In plain words, the three phases do not match each other the way they should.

Why does this matter? A three-phase inverter shares its work across three phases. If one phase is weak, missing, or wired wrong, the inverter cannot feed power in a safe and even way. So it stops and shows the code. This is a protection step, not a dead board.

What should you do? Check if the problem is in the whole area or only in your house. If the grid in your street is uneven, wait for it to settle, then restart once. If the grid looks fine but the code stays, call your installer. Phase wiring, phase order and load balance across phases are installer jobs. Do not swap AC wires by guess. A wrong phase wire can make the fault worse.

Note: If you run a net metering system, a phase problem can also stop your export to the grid. Your meter will show less export, or no export, until the phase fault is fixed. Fix the phase fault first. Do not blame the meter before the inverter code is clear.

F41 to F48: Grid Voltage and Frequency Out of Range

Codes F41 to F46 all mean the grid voltage on one pair of lines is too high or too low. F41 and F42 are for lines W and U. F43 and F44 are for lines V and W. F45 and F46 are for lines U and V. F47 means the grid frequency is too high. F48 means the grid frequency is too low.

The manual troubleshooting table groups F41 to F48 together with one plain cause: the grid voltage is outside the normal working range. That is a key point. When the grid itself is out of range, the inverter must disconnect. It is not allowed to feed power into a grid that is out of range.

What should you do? First, wait. Grid voltage often comes back to normal on its own. Then restart once in the safe way. If the code comes back at the same time each day, note the time. A pattern, like low voltage every evening, helps your installer and your power supplier find the real cause. If the code stays even when the grid looks normal on a meter, call a technician. The sensing circuit inside the inverter may need a check.

Do not try to fix grid voltage with a setting change you do not understand. Grid settings must match your local grid rules. A wrong grid setting can stop the inverter, or worse, can let it feed power when it should not.

F01, F02, F03, F23 and F24: DC Side, Insulation and Leakage

These codes are the most serious ones for safety, so read them with care. F01 means the DC input polarity is reversed. That means the positive and negative panel wires are joined the wrong way. F02 and F24 mean the DC insulation is faulty. Insulation is the safety layer that keeps DC power from leaking to earth. F03 and F23 mean leakage current, power leaking where it should not.

The manual troubleshooting table links F23 to a ground error, or a panel wire shorted to ground. It links F24 to panel wires whose resistance to ground is too low. In plain words, water, a damaged wire, a cracked panel, or a bad connector can let power leak to earth. The inverter sees that leak and stops.

What should you do? Keep the inverter off. Do not touch DC wires while they may be live. Solar panels make power whenever light falls on them, even when the inverter is off. Only a qualified installer should open DC connectors, test insulation, and find the leak. A home owner must never wash, cut, or rejoin DC wires to clear these codes.

Note: If these codes show up after rain, a storm, or roof work, tell the technician that fact. Water and roof work are common clues for insulation and leakage faults. That one detail can save hours of searching.

F55 and F56: DC Bus Voltage Too High or Too Low

Inside the inverter, there is a DC bus. Think of it as a main power road inside the machine. F55 means that road voltage is too high. F56 means it is too low. The manual troubleshooting table links F55 and F56 to solar voltage that is too high or too low.

F55 often points to the solar strings. If the string voltage is higher than the inverter can take, the bus voltage climbs too high. String voltage rises in cold weather, so a string that worked in summer can trip in winter. That is why a string design must be checked, not just restarted. F56 can mean a lost string, a poor connection, or a hardware fault inside.

What should you do for F55? Keep the inverter off and get the strings checked by your installer. Do not keep restarting. A high bus voltage is not a code to push through. What should you do for F56? Check that all strings are connected and no DC breaker is tripped, then restart once. If F56 stays, call a technician. The cause may be a lost phase, a poor connection, or a fault inside the inverter.

F09, F19 and F64: Inside Power and Heat Faults

F09 means an IGBT is damaged by too much drop voltage. An IGBT is a power switch inside the inverter. It handles heavy power. When it fails, the inverter cannot switch power in a safe way, so it stops. F19 means a combined hardware failure. Both codes are technician-only faults. There is no safe home fix for them.

F64 means the IGBT heat sink is too hot. A heat sink is a metal part that pulls heat away from the power parts. If the heat sink gets too hot, the inverter stops to save itself. The cause can be simple, like blocked air flow, direct sun, or dust on the heat sink. Or it can be a deeper fault in the power stage.

What should you do for F64? First, let the inverter cool down. Clear anything that blocks air flow around it. The manual says to clean dust from the heat sink with a soft brush, but only after the inverter is off and cool, because the surface can be very hot. Never use solvents or rough materials to clean it. If F64 comes back after cooling and cleaning, call a technician. The power stage may need a test.

For F09 and F19, do not open the inverter. Power parts inside can hold dangerous voltage even after switch-off. A technician will test the power stage with proper tools before any part is changed. If a part is changed, it must match the full part number, not just the size.

How to Shut Down and Restart in a Safe Way

Restarting also has a right way. A wrong restart does not help, and it can hide the real fault. Here is the safe way from the manual. To shut down, first switch off the AC breaker. Wait for 30 seconds. Then turn off the DC switch, or disconnect the DC input connector. The LCD and all LED lights will close within two minutes after these steps.

To start again, do the steps in reverse order, and leave a few seconds between each step. First, join the DC side. Then switch the AC breaker on. Then let the inverter start and watch the screen. If the same code comes back, stop. Do not restart again and again. One safe restart is enough to tell you if the fault was a one-time event.

The manual also gives a factory reset path, under Setup, System Param, Factory data reset. Do not use a factory reset to clear a fault code unless a technician tells you to. A reset can wipe settings that your installer set for your grid and your strings. A wiped setting can bring a new fault.

Bonus Tip: If you must call a technician, give these five details, as the manual asks for them. Your inverter serial number, your installer or dealer, the install date, a full description of the problem with the code and LED state, and your contact details. With these five details, the technician can start work at once.

When to Fix It Yourself, and When to Call a Technician

You can do these jobs yourself. Note the code and take a photo. Check the grid state and the breakers. Clear air flow around the inverter. Restart once in the safe way. These jobs are safe. You do not need to open the inverter for them.

Give it to a technician when the code keeps coming back, when you smell burning, when a connector looks melted or black, when a DC or leakage code shows up, or when you see an inside code like F09, F11, F12, F19, F26, F30 or F64 that will not clear. Opening the inverter and testing power parts is a technician job. Touching power parts by guess can be risky.

If you have a general guide to error codes, read it too. Our general guide, Solar Inverter Error Codes in Pakistan, explains the safe first steps for any brand. For a Fronus hybrid, the codes are different, so read Fronus PV 7200 Error Codes 2026 instead of this guide. And if your inverter will not turn on at all, read Solar Inverter Not Turning On 2026 before you change any part.

Where to Find Parts, and What to Watch

For Nitrox grid and power faults, the part is rarely the first answer. The grid, the strings, the wiring and the earthing come first. Only after a real diagnosis should a part be changed. When a diagnosis does point to a power part, the part must match the full number and package. A wrong part can bring the same fault back.

Parts that technicians often check for inverter faults include the full MOSFET category, the NCEP 85T16 MOSFET and the HY3215 MOSFET. For the inverter itself, see the Inverex Nitrox 6KW-3Ph On-Grid Solar Inverter on SunTech Mall. That model is a three-phase on-grid inverter with dual MPPT, IP65 protection, up to 98.3 percent max efficiency, and a 5-year warranty, as listed on its product page. Check the live price on the website.

SunTech Mall has one wholesale price rule for everyone. One piece or many pieces, the rule stays the same. Check the live price on the website. Orders go by TCS all over Pakistan within 24 hours. If you do not want to repair it yourself, SunTech Mall has its own repair service center. You can send your inverter there for repair.

Other inverters in the same shop include the Inverex Yukon II 3500W and the Suntech HYB-10KW. Those models use different code systems, so do not use this Nitrox F-table for them. Match the guide to your exact model, every time.

Frequently Asked Questions (FAQ)

What does F35 mean on my Inverex Nitrox?

F35 means no AC grid. Check the grid and the AC breakers first. If the grid is down, wait for it to come back, then restart once in the safe way. If the grid is fine but F35 stays, get the AC wiring and grid connection checked by your installer.

Can I restart my Nitrox again and again to clear a code?

No. Restart once in the safe way. If the code comes back, stop. Turning it on and off again and again puts stress on the board and can make the damage worse, most of all for inside and bus faults.

Are Nitrox F-codes the same as other Inverex codes?

No. Older Inverex hybrid models use plain numbers like 01, 02 or 09. Nitrox on-grid string models use F-codes like F35 or F55. Always match the code table to your exact model and your own manual.

My Nitrox shows a grid voltage code. Is my inverter broken?

Not always. Grid codes like F41 to F48 often mean the grid itself is out of range. Wait for the grid to settle, then restart once. If the code stays when the grid is normal, a technician should check the sensing circuit.

What should I do for a leakage or insulation code?

Keep the inverter off and call a qualified installer. Leakage and insulation faults can mean a damaged wire, a cracked panel, or water in the system. Solar panels make power in daylight even when the inverter is off, so DC work is not a home job.

What does F64 mean, and can I fix it myself?

F64 means the IGBT heat sink is too hot. Let the inverter cool, clear the air flow, and clean dust with a soft brush only after it is off and cool. If F64 comes back, call a technician, because the power stage may need a test.

Where can I find Nitrox parts and help?

See the Inverex Nitrox 6KW-3Ph On-Grid Solar Inverter and the MOSFET category on SunTech Mall. Check the live price on the website and reach out on WhatsApp.

Final Thoughts

A fault code is not your enemy. It is the inverter telling you where the problem is. A person who learns the code can solve half the problem right there. The other half is solved with the right check, and the right hands, in the right order.

My advice is simple. For every fault, note the code. Take a photo. Check the grid first, then the outside wiring, then the air flow. If the problem turns out to be inside, or on the DC side, give it to a technician soon. A small problem can turn big if you wait, and a wrong restart can turn a small fault into a board fault.

If your Inverex Nitrox is stuck on a code, do not worry. Use the links above to see the model and parts that fit, or send a photo of the code on WhatsApp. SunTech Mall has served Pakistan with solar products and repair work since November 2022.

Sources: For the full F01 to F64 table: Inverex Nitrox 12KW user manual, error code table (F01 to F35) and Nitrox 12KW manual, error code table continued (F36 to F64) and troubleshooting. For Nitrox 6KW model facts (dual MPPT, IP65, 98.3 percent max efficiency, 5-year warranty): Inverex Nitrox 6KW-3Ph On-Grid Solar Inverter on SunTech Mall. For the general safe-first-steps method: Solar Inverter Error Codes in Pakistan.

Published: 25 October 2026 | Updated: 25 October 2026 | SunTech Mall — Charsadda/Tangi Office, Tangi Moor, Tangi Charsadda