Inverter only producing half power

[littleharbor]

Testing Voc and Isc will tell you 99% of what you need to know. If it passes those two tests, there's very little else that can be wrong with it.

The thing is there's no load in panels when checking either Voc. or Isc. Granted these two tests will definitely weed out a malfunctioning panel in many cases. Panels will many times show fine with no load on them but they really need to be under load, and if possible when fully heated by the sun to bring out some problems.

[jflorey2]

The only real effective way to determine if panels are functioning properly is with an IV Curve trace. OC Voltage only tells you so much.

Testing Voc and Isc will tell you 99% of what you need to know. If it passes those two tests, there's very little else that can be wrong with it.

[emartin00]

The only real effective way to determine if panels are functioning properly is with an IV Curve trace. OC Voltage only tells you so much.

[inetdog]

Yes, he reported equal amperage from both arrays. If the array was bad then the voltage input to the inverter would be sagging under load. Didn't see that happening. The two parallel arrays are joined at the roof. Only one pair of wires coming down to the DC disconnect and then to the inverter.

Not true. That is not how an MPPT input stage works. If the array is only capable of putting out half power, the maximum power voltage, Vmp, will not be any different from the situation with full array output.

[JerryA]

Yes, he reported equal amperage from both arrays. If the array was bad then the voltage input to the inverter would be sagging under load. Didn't see that happening. The two parallel arrays are joined at the roof. Only one pair of wires coming down to the DC disconnect and then to the inverter.

[inetdog]

Voltage equal on the arrays? Did he check Amperage?

The voltage could be fine with a defective cell in one panel keeping the whole string from producing much at all. If he suspects one half of the inverter, just disconnect one half of the array at a time and then move each half to the other set of terminals.

[Ampster]

Voltage equal on the arrays? Did he check Amperage?

[JerryA]

My system is about 5 years old. When first installed I would see about 2000 watts max, typically less. On a hot summer day perhaps only 1100 watts. During the last 6 months I am only seeing about 500 to 700 watts. A technician has been out twice. He checked the panels, two parallel arrays, and voltage was equal on both sets. The inverter is a Fronius IG 3000. The only error code showing is the "it got dark last night" normal one. The tech thinks it is the inverter but can not replace it without an error code. Some of these inverters have two units internally. Could one have stopped without an error code? Any suggestions? - Jerry