Thanks for the help SG. I still don't know what caused the Ground Fault condition. The inverter has operated normally ever since it cleared. That in itself seems wrong according to the manual. Beyond the ground fault the inverter seems to be returning to normal function. After I got home and checked it all out we discovered there was a convergence of factors conspiring to collaboratively undermine our photovoltaic production. Try saying that three times fast, LoL. Anyway, not only was it very hot and very humid, about 95 degrees Fahrenheit and 95% humidity causing loss due to heat and loss due to atmospheric haze, but there was also a nearly uniform layer of gunk from pollen, dust, and other air born contaminants as well as the all inhibiting Bird Poo. Once cleaned, the panels seemed to miraculously regain around 450 watts of output. We used a swimming pool brush with a thick rag rapped around the hard bristles to prevent scratching. We also used plain water from a pressure washer. I read you can't use soap on these panels though because it could react with the anti-reflective coating on the Sunpower panels and cause it to cloud up and possibly begin to erode or at least be damaged. Anybody know of anything I can use to clean them? Anyway I checked out all the wiring on the outside of the wiring boxes as I did not look inside them because I was in a hurry, I had plans to Hike Mt.Tumbledown this past Saturday and a party to attend Sunday so I didn't have time to do a complete check. However the GF condition has not returned and the array output has increased due to cleaning and cooler days. We have been seeing average mid day outputs now of around 2650watts or so, that’s pretty normal for hot summer days of 85 to 95 degrees. Also when we got the GF we tested the arrays 2 strings (Before Cleaning) they were within 100watts of each other which is less than a 7% variation (Compared to full output) and could have been due to un-even cleanliness or un-even shadows from unknown sources, but I wasn't there so who knows. Also the grounding is accomplished through the main fuse box ground/neutral bus, which is grounded to the ground rod previously mentioned. The old battery based solar system and secondary fuse box is also grounded to the same rod. That should keep all grounds and neutrals at the same potential. None of our systems has an independent ground. Any comments are welcome; I will be keeping an eye on it and will check the GF fuse as soon as I get a chance. Unless the GF returns though, I will assume the inverter to be in correct working order. Thanks again everyone!

Hi guys, me again. This inverter still isn't right. The output has normalized and all seemed fine till this past friday. The inverter kicked out and ground faulted again, but once again, did not blow the fuse. We shut it off and turned it back on and it came right back online and cleared the fault. It's been normal ever since. All I can say is WTF!?!? All the wiring is fine, I checked it. So I guess Im stuck with sending it back for service again. What do you guys think?

Thought I would come and take a look in here to see what everyone thought of the Recall that I recieved notice of from Alt Energy Systems and realized that I never posted the resolution the the previously posted issue. Turned out after the inverter went back to Xantrex, they held it for a month waiting for info from me but never called to ask me for it. When I finnally called the check up, I found out the issue was simply that they last person to work on the inverter (someone from Xantrex) did not tighten the screws connecting the wiring box to the inverter and it was loosing its ground. Simply tightening those bolts with the star washers worked and the inverter has been fine ever since I got it back from them.
Now I am contemplating my next upgrade, connecting the 3kw Sunpower Positive Ground array to the 16 Us-Battery L16 type Deep Cycle cells that currently only has a 750watt array connected to it. From what I understand, the Xantrex MPPT 80 Charge Controller (due out in Q1 2011) should be able to handle the whole array. Im hoping to have it switchable between the charge controller and the original GT inverter that I have now. I need some new batteries too as the 13 year old batteries we have now seem to peak at about 25volts on a 24volt system, not good.