My Gridtie system is 48 Kyocera 120-1's and they simply rock. I had the two systems curve traced last week and each array of 24 panels was identical in output

There not the cheapest but I would recommend them to anyone who understands the benefits of well matched panels vs bargin basment price per watt [img]images/smiles/icon_smile.gif[/img]

I've got a low output problem on one of my 6 strings (of 4 each) KC-120s. There is an ammeter on each string, and while 5 of the strings are reading 4 amps, there is one string that reads 1-2 amps. They used to be all about equal.

The problem right now is how to isolate the weak component. I tried covering one panel at a time, and the entire string goes to zero if I cover any panel of a string. The hope was that there would be some difference that would identify a weak panel. Since the KC-120s are hard wired, I'd rather narrow down which component is weak before undoing everything in sight. Are there any techniques for identifying one weak panel while it is connected in a string of 4? The panels are connected to an ST2500, which goes into a snit whenever the power level changes.

Should be simple ...

First pull the DC fuses on the ST combiner board.

Using an amp meter , just put the amp meter across the + and minus in each panel. The Amp meter will short the panel and you will be reading the short circuit current which for the KC-120 should be about 7.4 amps in full sun ...

4 amps is WAY to low for KC-120's but that is probably the ST not loading the array properly

[img]images/smiles/icon_razz.gif[/img] [img]images/smiles/icon_razz.gif[/img]

Rob,

You should be able to isolate the problem fairly easily. It is more than likely not a panel problem but check for short circuit current like Solar Guppy posted. If you don't find a weak panel, put back the fuses in the ST combiner board and measure the voltage from the negative terminal of the first panel in the string to the positive terminal of the 4th panel. If the voltage is higher than the same measurement for the properly working strings, you have a bad connection between the panels and the inverter. If the voltage is about the same, the connections between panels needs to be checked. Check the voltage between the plus of the first panel and the minus of the second panel. It should be much less than 1 volt. Next check the voltage between the plus of the 2nd panel and the minus of the 3rd panel. Last, check the voltage between the plus of the 3rd panel and the minus of the 4th panel. Wherever you read a higher voltage will be a poor connection. It's actually easier to do than to describe.