First, many many thanks to Mr. Henry Cutler for this website and the 2002 article on inverter comparison.

I have a tracked array of 18 ea. Matrix PW1650's, a total of 2850 Watts.
The tracking mounts (9 ea, 2 panels each) is my own design, completed earlier this year. The two panels on each mount are wired in series for 48 volts (nominal), the 9 pairs then wired in parallel.

I am running a ST2500 with rev 03.0 software and have experienced the very disappointing performance that I am now finding has been well documented for years. The inverter is located on an interior wall in a ventilated, and unaircondition space.

I have never seen more than 2000 Watts from this arrangement, and if I get 5 minutes of cloud cover, the inverter backs down to 1450 Watts and happily stays there when the sun come back out. Obviously this bites, especially after going to the trouble of building a tracked system.

Is there an inverter you kind folks can recommend that can replace the ST2500, 48V input, 240 VAC output?

Are there any concessions by Xantrex for the ST2500 such as replacement or discount on a new model?

It is possible to reconnect the 9 each 48 volt pairs in series if this scheme opens up more inverter options.

Thanks,

Juan

My limited knowledge would say you would be a good candidate for a new Xantrex GT3.0 but you would have to do some rewiring since it is a string inverter requiring about 300volts minimum. Someone correct me if I'm wrong but I don't tink anyone makes a low voltage inverter like the ST's were. If you are turned off by your current Xantrex and want to switch you could go with an Outback.

For the 18 panels, the OCV is 675, just a bit over specs (GT and SunnyBoy are 600V max) The PW1650's are not matched, 12 are 155W and 6 are 165W. Not a big deal, but they share current in the parallel arangement.

Is there any willingness from Xantrex to upgrade the software for these old inverters? Is rev 03.0 the latest version?

Thanks,

Juan

2 strings of 9 panels would work nice. When I was looking to add to my array Guppy told me that 102w and 110w would be fine together so I'll assume that would hold true for your 155 and 165's. Someone correct me if I'm wrong.

Splitting into two arrays may be the answer. The avitar photo shows the system with the original 12 155W panels (now 18 panels). To split the array exactly in half would require connecting the south 9 panels as one array and the north 9 panels as the second. This would require a second run of #10 wire pair up through the upright, coiled around for the flex loop and down the panel mount tube to the panels. Negligible fun there.

A 3-3-3 slpit would work well as they are currently grouped as 3x3 as to the underground conduit runs. 3x48 = 144V Is this a suitable voltage for one of the available inverters? (should it be 3x55 = 165)

A 4-5 split would possibly work, voltages being 192 and 240 respectively.

Adding another 2 panels and mount for a 5-5 split would be ideal, but I thought I was done cutting metal...

I (with help from Xantrex) have painted myself into a corner.

Check out the sizing tool for the GT inverters

http://www.xantrex.com/support/gtsizing ... p?lang=eng

2 string of 9 seems like your best option

Your best bet is to have two strings of 9 panels.

You shouldn't have to do much for the extra two wires, since your already home running more wires than needed!!

Rewire as needed at the ARRAY, this will reduce the total wire lenght, for example instead of having the "+" of panels 1-4 be a home run , rewire at the array to connect to the "-" of panels 5-8. This will free up 4 wires on your array of which you only need two to make the 9X2 for a GT. Better yet, just do all the rewiring at the panels and only home-run the 4 wires

Someone else posted that Xantrex is offering new GT2.5's for 999.00 if your inverter needs "repair" , call service and tell them you need to replace the ST with " issues" and you should get the 999 deal. Be mindful, that it's apparent you bought a used Suntie as the model you have has not been produced since 2002.

On my array, I have mixed 155's and 165's ... it makes no detectable loss intermixing the two, just try and get the same number of each ( 155 or 165's ) in the string. What will happen is the 165's will operate at a slightly higher voltage to match the lower current of the 155's. As longs as the number of 155's is the same on the parallel string, you should be fine.

Thank you folks very much for your input. I am going to use the string connection, and GT3.0. I can jumper the Matrix panels for 12V instead of 24V. This will allow minimal wiring changes and it gets the voltages correct for that inverter.

Juan

P.S. The string connection should be much more exciting when I give it the screwdriver voltage test!!