Hello all this is a great site!!
I'm very new to this. I have alot of questions about my ST2000 suntie.
I have 4 Sharp 165w panels installed, on the LCD I see 87vdc of power going in to the inverter.
If I disconnect 1 string (2 panels) I still see 87vdc going in, should the input dc voltage change when I have more PV inputs?
Now the input watts change when ever I disconnect one string, that will be 300 - 320
with 2 strings and 130 - 160 with just the 1 string. Part of my problem is I don't have a older ST2000 oper manual. Any thoughts???
Thanks,
Gus

Gus,

Each 'string' of panels will be in parallel with the other one(s), so your input voltage will not change as you add more strings. And as you saw, the watts did change as would be expected. You removed one string and the power dropped in half.

[ 03-16-2004: Message edited by: Mark Lopez ]

87 Volts seem very high for an operational voltage from the array.

If your refering to the open circuit (no load) than that makes sense ..

What is the displayed voltage when producing 300 watts ?

The LCD shows 87v & 300 - 320 watts.
Now the Voc is 43.1 x 2 = 86.2....right?
Are you guys saying the highest voltage I should see is 34.6 * 2 = 69.2 ?? No mater how many PV input strings I have?
Thanks,
Gus

I agree that the 87v seems high (if being read during operation). On my system (using sharp 165w panels), the DC input voltage maxes out at about 72v before the inverter starts working (i.e. open circuit) and will usually be around 62v during operation.

But to answer your question, the voltage will pretty much stay the same regardless of how many strings you use because you are just putting them in parallel. You are connecting the strings (2 panels per string)in parallel aren't you?

Can you please discribe you your panels are wired ? (interconnect wise and to the Suntie

Also , have you connected a DVM to the inverters input to make Sure the Suntie is reporting the true voltage

In average say 70 deg day , you would expect to see the voltage about 60 volts if the inverter is tracking vmp correctly , I'm guessing the Suntie is toast in regards to the Voltage it is measuring ...

[ 03-17-2004: Message edited by: Solar Guppy ]

Well... this is VERY late reply to this post, but I seem to have similar problem with my ST2500? The MPPT tracking does not seem to work.

To put my story short, I purchased cheap (less than $200) ST2500 from eBay. (OK.. now you can stop laughing...) It was known to be DOA unit, that I had to fix first. (Problem was that the AC line voltage and frequency was not shown in the display. To fix I found two optocouplers bad, those were easy to replace.) Now, that it appear to work (at least it sees line voltage and starts up), it just still doesn't seem to work properly. With two 24V (128W each) panels, the Voc was 82V. Once the inverter started the panel voltage dropped only slightly, to about 78-79V. Correct MPPT voltage should be about 60-66V. During test it only made some intermittent 0-40W of power. To get "any" continuous power out from the ST2500 I had to add one extra 12V panel in series to the existing panels get the voltage to 101V open circuit. During operation it lowered to about 90V, and I got about 100-140W of AC power out.

One question is that is my solar array too small to get this thing running? I think I read somewhere that array size should be over 400W for the MPPT to work properly on ST2500?

If the answer is that it should work... then does anyone know what might be the problem? Maybe one more optocoupler... (There is a ton of them inside the ST2500!)

I know that I need to upgrade to something like GT3.0, and probably will once I find a good deal on GT3.0 and once I get my array built to some reasonable scale...

The original ST2500 needed more like 400-500 watts to do much of anything, more like 1000 watts to have mppt that tracks in clear weather, but forget about partly cloudy conditions.

DONT RUN AT 100VOC, you'll toast the inverter in no time!

The UPG version, manufactured after Jan 2003 and software version 5.0 displayed on power-up is better at low power operation, it would probably work at 200 watts OK

For 200 bucks, you did OK, I see old Sunties ( Non UPG ) selling for 500, UPG's for about 1k

The GT is a great inverter, but you need about 220VDC , VMP for good performance which is more like at minimum 8 24V panels

Solar Guppy,

Thanks for the reply! In other words my ST2500 is propably OK but I need more solar panels. Help is on the way, since 20 new panels (Matrix solar PW-750, 85W) should arrive in few days. Unfortunately my house (condo) I can not put the panels on the roof and my little backyard (where the panels will go) is shaded by the building this time of year. Most likely next time I can really test it sometimes late February...

With the new 20 panels The GT3.0 should be happy...

But to think about something positive: By that time I may be able to find the GT3.0 (or GT2.5? It should be about as good...) with good price...