We don’t really specialise in Victron systems where I’m currently working, but I have worked with them quite a bit in the past. One error that I’ve seen more often than I ever expected is the Error 8 – Ground relay test failed.
I never properly documented a real-world case of this one, but it’s actually a very easy fault to recreate. That makes it a good example to walk through both what causes it and how to troubleshoot it properly.
So first off, what does Error 8 actually mean?
In most cases (I’d say 99% of the time unless you’ve got an actual hardware failure), it means there is a neutral-to-earth leakage somewhere downstream of the inverter. The inverter picks this up when it switches from island mode back to grid, and performs its ground relay test. If it detects any leakage during that test, it throws the error.
The important thing to understand here is that the Victron inverter creates its own neutral-earth bond when it’s in island mode. It does not want to see any external neutral-to-earth connection on the output side.
The most common issue I’ve found is a neutral conductor somewhere downstream that is leaking to earth. Not enough to trip an earth leakage, but enough for the inverter to pick up.
For context, in South Africa, an earth leakage will typically trip at around 20mA. The Victron, however, is a lot more sensitive than that — it will detect much smaller leakage currents and still throw Error 8 without ever tripping the earth leakage.
To demonstrate this, I recreated a small leakage fault.
All I did was wire a 20kΩ resistor between neutral and earth on a standard plug. This introduces a small leakage current, enough to trigger the inverter, but not enough to trip the earth leakage. Pretty similar to what you’d see in a real installation.
Plug that into any wall socket and switch it on, now we’ve got a “hidden” leakage fault in the system.
Next step is to force the inverter to run its test:
- Switch off grid supply to put the inverter into island mode
- Wait a minute or two
- Switch grid supply back on
As soon as it reconnects and performs the ground relay test, we get:
Error 8 – Ground relay test failed
So now we’ve got a clean, repeatable example of the fault.
Diagnosing this is actually quite straightforward.
First thing I’ll do is switch off the inverter’s output breaker. Then I repeat the same test:
- Grid off
- Wait
- Grid back on
This forces the inverter to run the relay test again.
If the error does not come back, we’ve already learned something important, the inverter itself is fine. The problem is somewhere downstream on the installation.
From there, the next step is an insulation test between neutral and earth on the load side (with the output breaker still off).
In this case, the test fails, confirming there is leakage present. Again, not enough to trip earth leakage, but enough to trigger Error 8.
Now we need to isolate where it’s coming from.
I’ll usually head to the main DB and test between the neutral busbar and earth. If that fails as well, we know the issue is somewhere on that neutral bus.
From here, there might be faster ways to do it, if you’ve got one, I’m keen to hear it, but what I typically do is start isolating neutrals one by one.
Disconnect each neutral from the bus and test individually until you find the one with the leakage.
Once you’ve identified the faulty neutral, you can trace it back to the circuit. In this case, it pointed to one of the plug circuits.
At that point, it’s just a matter of checking each socket on that circuit until you find the fault.
In this demo, that “fault” is just the plug with the resistor.
With the fault removed, we reset everything and run the test again:
- Grid off
- Wait
- Grid back on
This time, no error, the system passes the ground relay test as expected.
Error 8 almost always comes down to a small neutral-to-earth leakage somewhere downstream. The tricky part is that it often won’t trip an earth leakage, which makes it easy to miss.
But once you understand how the inverter is testing for it, and you follow a structured isolation process, it’s actually a very manageable fault to track down.