Replacing Fronius IG 4000 Questions

[jjoeg]

I have a 22 panel Kyocera 210 system that was installed in 2011.The inverter is a Fronius IG 4000. The inverter has been replaced twice under warranty (each lasted almost exactly 4.5 year), repaired twice under warranty, and repaired 3 times out of my pocket. It has failed again and I want to replace it . The last repair person told me the system in "groundless" or grounded on the positive side. Does that make sense?
I would like to replace it with a larger unit (6kw) to allow future expansion. I want to keep my existing NEM 1.0 so am looking to do it myself. I was looking at a Fronius Primo which I'm told would be a fairly straight forward swap. But I have little confidence in the reliability with my experience. Plus, I guess they aren't really available anywhere.
I'm looking for suggestions and advice, please.
Thank you
Joe

 

[Hedges]

Fronius is a quality brand, as is SMA which I use. Should not die in 4.5 years. I had 5 inverters for 17 years, two failures. MTBF about 32 or 34 years.

Transformerless systems are ungrounded, PV+ maybe above positive AC peak and PV- below negative AC peak. Later transformerless (or non-isolated) inverters may have high frequency transformer, and PV string voltage doesn't have to be greater than AC Vpeak, but is still ungrounded.

Older inverters were negative ground, then some positive ground to avoid "PID" degradation of some PV modules.

Excess PV voltage, overheating, power surges, coupled lighting are possible damage mechanisms.

Measure PV voltage with AC breaker shut off. PV+ to PV-, PV+ to ground, PV- to ground.

Looks like HF, probably ungrounded inverter. 500V max.

After confirming operating voltage, I would consider replacing it with a used or new old stock Sunny Boy. Or, select a hybrid inverter and get battery backup.

https://www.fronius.com/~/downloads/Solar%20Energy/Datasheets/SE_DS_Fronius_IG_US_EN.pdf

 

[jjoeg]

Fronius is a quality brand, as is SMA which I use. Should not die in 4.5 years. I had 5 inverters for 17 years, two failures. MTBF about 32 or 34 years.

Transformerless systems are ungrounded, PV+ maybe above positive AC peak and PV- below negative AC peak. Later transformerless (or non-isolated) inverters may have high frequency transformer, and PV string voltage doesn't have to be greater than AC Vpeak, but is still ungrounded.

Older inverters were negative ground, then some positive ground to avoid "PID" degradation of some PV modules.

Excess PV voltage, overheating, power surges, coupled lighting are possible damage mechanisms.

Measure PV voltage with AC breaker shut off. PV+ to PV-, PV+ to ground, PV- to ground.

Looks like HF, probably ungrounded inverter. 500V max.

After confirming operating voltage, I would consider replacing it with a used or new old stock Sunny Boy. Or, select a hybrid inverter and get battery backup.

https://www.fronius.com/~/downloads/Solar%20Energy/Datasheets/SE_DS_Fronius_IG_US_EN.pdf

Thank you