Using a SunPower positive-to-ground module with a modern Tigo TS4 MLPE system or Tigo EI Inverter does not affect the Tigo Warranty or product operation. However, there is no way to predict how much PID (potential induced degradation) the array will suffer when connected to a modern transformer-less inverter (like the Tigo EI Inverter).
Older SunPower PV modules (pre-2012) were great at reducing the PID associated with the degradation of other module manufacturers of that era. To do this, they required transformer-based inverters that were also positively grounded.
Since then, the industry has switched to transformer-less inverters (which require an array with no internal grounding).
Now, that the older transformer-based inverters are getting harder to find, thousands of SunPower systems are now aging out, and customers need a replacement solution. If the Installer cannot find a refurbished older model Inverter, they find themselves replacing the old transformer-based inverter with a transformer-less inverter (like the Tigo EI or GO inverter).
Note: Although a newer inverter will work, there are some considerations (related to the PID). However, there is no way to measure the potential induced degradation they will suffer over time.
There are PID boxes available on the market that can reduce positive-to-ground module degradation caused when these modules are connected to transformer-less inverters. Tigo is investigating several manufacturers so that we can bundle our MLPE, Inverter, and PID boxes as a packaged solution for these systems. Once this solution is available, we will update this article.
If you have any questions, please contact our Customer Success team.
Affected Sunpower PV Modules:
The following Sunpower PV panel models require positive grounding, where ### is replaced with the power value of the panel, usually 200 to 230 watts:
These are the most common inverters that SunPower installed in their customer network:
- Fronius IG and IG+ series with positive grounding (this inverter has a transformer)
- SMA SB3000 to SB7000 series with positive grounding (this inverter has a transformer)