solar isolation fault

Isolation Fault Error Message on Inverter

Do you have an ‘Isolation Fault’ Error message appearing on the screen of your solar inverter?

If this is the first time you have seen this Isolation Fault it may be very daunting. Let me assure you that generally, the news is not good! If your solar system is within 3 years old. It could possibly pass in the next few days. I say this because this has happened to my very system during periods of rainy wet weather. I got the Fronius State 475 error code up for a few days a couple of years ago, and never again. Weird, but it happened, I;ve also witnessed it a few other times since then too. Give it a few days of clear weather to dry everything out.

What does the Isolation Fault on a solar inverter mean?

If your Fronius inverter is throwing up a State 475 Error, or your cheaper Chinese inverter just says on the screen ‘isolator fault’, it means that there is a problem (a short) somewhere in the DC area of the solar system.

fronius state 475 error code

This means the solar inverter error isn’t actually broken, or usually, it isn’t the solar inverter failing.

Most likely it’s a problem with the solar panels. They are getting water in them and causing the system not to work. For a few months to a year, the system will keep limping along and starting up around 10:30 am in the morning, once all the water and moisture has evaporated and dried out of them.

The solar system’s solar inverter shows the Isolation Fault error message every morning – what does this mean?

This means what I stated earlier, the water is getting in the solar panels, sometimes you can get lucky and it’s only an isolator switch that the water is getting in. However more than likely, it’s the solar panels getting water inside them as they were poorly built.

Why are solar panels causing the Isolation fault error message to appear on the solar inverter?

Solar panels from China, even Tier 1 mid-range panels built in the 2010s are starting to fail by the masses. This includes QCell, Jinko, Trina, and Canadian solar panels. The list well and truly goes on. This is also a list of the better panels that are dying at the 7-8 year mark. A lot of cheaper, budget solar panels installed in 2016 had died before 2021. Panels such as Hannover. When we first seen this start to happen we made a note of not selling the cheapest solar panels on the market anymore.

water in solar panels causing an isolat fault and ground fault in a solar system

They didn’t even last 5 years! and the ‘mid-range. I don’t want the most expensive solar panels, but I definitely don’t want the cheapest solar panels’ Well you buyers got conned here too it appears. Unless you bought a solar panel like LG, Sunpower or SolarWatt, it really doesn’t look like you escaped the wrath of the hot Australian sun and poorly built solar panels.

How can I test what is causing the solar inverter to show an Isolation ground fault message appearing on the solar inverter?

You can do a quick test at home to try and find what the culprit is that is causing this isolation fault showing on your solar inverter’s display.

This is how you can test what is causing the solar isolation fault.

  1. Wait until the sun is shining and the inverter is working, as with this error, you will find it works intermittently.
  2. Grab a friend, spouse, or neighbor.
  3. Grab your garden hose
  4. Aim it at an end of the solar system, the panels on the roof.
  5. Yell out to your assisting partner, “Turn the bastard on!”
  6. Spray, and drench from one need to the other. While waiting for your mate to tell you when the failure occurs.
  7. Now you can use your brain to try and determine if it’s’ coming from cabling, an Isolator, or a panel on the roof.


What can I do to fix the Isolation Fault on my solar system and get the solar inverter working again?


Call us and we can arrange for Julian or one of the electricians of our solar installation team to come out and check on it if we feel it’s worthy. Otherwise, being honest you just replace the solar system with quality German-made solar panels, like Solarwatt so it doesn’t happen again. These solar panels are built differently. Glass in the front, and also glass on the back – Water cannot get inside them.

We also have a range of other solar panels we sell that we can replace your broken solar system with.

Give us a call and get in contact with us if you would like some advice on you solar isolation ground fault that you are experiencing.


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