Nybergs ElKonsult AB
Independent solar PV consultant, Sweden
I tested a 200 kWp system where the client suspected module degradation. The Z300 showed string resistance values between 0.8 and 1.1 ohm across most strings, but two strings came in at 4.2 and 6.7 ohm. That was enough to locate two faulty MC4 connectors that would never have been found with a standard IV curve tracer. The repair cost was minimal. The energy loss had been going on for over a year.
Finding faults that other instruments miss
Richard Nyberg runs Nybergs ElKonsult AB as a solo consultancy, specialising in solar PV design, installation and inspection across Sweden. As an independent consultant, every site visit has to deliver clear, defensible results he can stand behind when presenting findings to clients and installers.
He had worked with standard IV curve tracers and insulation testers before investing in the Z300. The turning point came on a 200 kWp commercial rooftop where the owner reported lower-than-expected yields but no obvious faults. A standard inspection had found nothing actionable.
The connector fault that cost a year of yield
Using the Z300 to measure series resistance (Rs) on every string, Richard found that the majority of strings measured between 0.8 and 1.1 ohm. Two strings returned values of 4.2 and 6.7 ohm respectively. Values that high pointed directly to a contact resistance fault rather than module degradation.
Physical inspection of the two outlier strings confirmed two degraded MC4 connectors. The connectors were replaced in under an hour. Yield monitoring in the weeks following the repair showed the affected strings back within normal range. The fault had been present and undetected for over a year.
Why Rs measurement changes the inspection workflow
For Richard, the value of the Z300 is not just in finding faults, it is in being able to show clients exactly where the fault is and why. A single number from a standard insulation tester tells you something is wrong. An Rs value of 6.7 ohm on one string while everything else reads below 1.1 tells you where to look and what to look for.
As a solo consultant, being able to test an entire rooftop array and identify outliers without an assistant or complex setup has changed how he prices and structures his inspection services. The cloud platform means all measurements are logged and exportable before he leaves the roof.