Inverter - FE not connected error

[megaohm]

I've been trying to find out what is up with my mother's solar panel system - as a DIYer, I'm comfortable with domestic electrics but have no experience of solar PV systems. The inverter won't start up and is displaying the error 'FE not connected' which according to the manual means protective earth not connected.

The system is grid tied with 16 panels in a single string connected to a Stecagrid 3600 inverter, its probably around 8 - 10 years old. I've checked the earthing which seems fine (Ze 0.21 Ohms at distribution board, and 0.5 Ohm at inverter). I've also been up on the roof and visually checked the panel wiring - all seems fine, and I've tried removing panels from the string four at a time to see if the fault disappears - it doesn't.

If the panels are isolated from the inverter, the error message can be cleared but reappears as soon as the panels are reconncted.

I suspect the inverter is duff, but before I commit to changing it, can anyone offer any advice - is there any other test that can be done, or does anyone know of a fault condition that can cause that error other than a bad earth?

 

[James]

Most diy posters do not give a ze figure to work with,
I assume you have more knowledge and test equipment than the average diy ”Bob”

I can only think of a couple of ways that the inverter could confirm that it has a functional earth connection.

1 it tests the loop using D.C. injection just like an earth loop tester
2 it pushes a little current down the earth and checks that the voltage does not rise.

 

[megaohm]

Yes - I have a Kewtech tester and sufficient knowledge to measure Ze, but there it ends. I'm happy that the earth connection is good, so either the inverter is measuring incorrectly or perhaps something else (no idea what) is causing an issue which is resulting in a spurious fault code - similar to the way faults in car electrics can sometimes result in fault codes that are seemingly unrelated to the actual problem.

 

[James]

Bit of a long shot, but check the voltage between N and E at the inverter supply
if there is a difference, it might see it as a ground fault.
other than that, it’s the manufacturers help desk I think.

 

[megaohm]

Good idea, but its only 3mV so not the issue.

 

[megaohm]

Just to update, the inverter has now been replaced with a Solis inverter and the system is working normally again, so hopefully anyone else who see's a 'FE not connected' error on a Steccagrid inverter can be fairly confident that its an inverter fault (assuming of course that the earth is connected properly).