Have a STXR2500UPG which recently dropped in performance, it only harvest about 50% of what I would expect from a week earlier.
Normally (up to a week ago) I would see about 1400W-1500W power at noon time and totaling about 12-13kWh harvest for the day.
But now I monitor only about 700W at noon time and harvesting about 6.5kWh by the end of each day.
I do not see any restarting or reconnecting, the display shows no error what so ever, all appears to operate normal.
The normal 'ticking/tracking' sound, too. When it started about 1 week ago I also noticed a buzzing sound, which by now is gone.
Any help or troubleshooting tips is appreciated

If you logging with fishbowl, that would help to see if there are any error's happening.

Two thoughts, you maybe having issues with you solar array ( Kyocera comes to mind ) or possibly your fan is no longer working and the unit is thermally limiting the power output ( this would be in the Fishbowl log or the LCD screen

Also, make note of the Mppt voltage and is it where you would expect it to be

Let us know what you find or more symptoms

SG

It took a while to get the COM port working, but managed at the end, just before I had to leave to work this morning.
The attached file is the day's worth of data. (one scan every 15min)
If needed I also have the same data in a 5MB file as one scan/sec.

Something is up with the AC reported watts, if you look at the power in to power out ( or the efficiency column ) the units is reporting that half the energy is not making it into the grid. If this was really happening, the unit would be over temperature ( > ~70C ) on the Heat Sink reported temperature

Its also odd the the Ambient Temperature looks to be in C and the Heat Sink is in F.

If the unit isn't physically scorching hot mid day, I would say the energy is actually going into the grid and it is the reporting of AC power that's gone south.

Your inverter is close to 8 year's old and the oldest one in the field I know off

I left the temp check box on, for C, and it seems that the temp for the HS is reported in F (probably a software issue), Unless there is a 2nd checkbox for the temperature of the HS reporting I missed.
Tomorrow I'll be home during the day and can monitor the unit. maybe the fan control is not working and it never kicks in so the HS does not get the air it needs.
Is there a temperature table to see at what temp the fan should turn on and at what speed?

And yes 8years it has been, like a workhorse. Maybe because I never had the max. panels connected?

Besides checking the fan and possible add additional air-flow, is there anything else I can test/verify?

When I left for work this morning, the temp for HS was at 85 and the fan was not running.

If the unit was over heating, it would report it in the log, which it is not

So what else could cause the drop in efficiency?

Is the HS just getting hot because the excess energy has to be 'burned' off rather sending it into the grid?

Are there any TP I can probe on and verify certain values?

Its only the reporting that is in error, your still getting the watts to the grid, the Suntie is just not reporting correctly the actual AC power. It has no effect on how the unit operates or how much solar is harvested.

If half the power was turning in to heat, the unit would over temp and shutdown in minutes, along with error messages on the LCD and in the Fishbowl logs

Nothing you can do about it, if you really want to know how many watts per day are being harvested, put a old style electric meter ( spinning disc ) on the output to total your kwhr.

I am using a clamp meter to read the AC amps coming out and list the numbers belows

Also I made some other observations:
- there is a buzzing sound from the unit (I try to tape it and post the sound)
- only the right HS has a temp sensor and this is the one I can feel getting hot
- the left HS remains rather cool, cannot feel any heat (will keep on monitoring it during the day)
- the fan does spin, I had it in my hand while it was running and could feel an unbalance
- the voltage on the open socket for the fan was reading about 120V~ (that was at 200W on the display)
- both the unit display and the remote monitor display seem to reflect what fishbowl is showing
- the unit's display wattage is what fishbowl shows as Watts AC


A~ | W~ | W= | V~ | V=
0.9 | 360 | 400
1.2 | 418 | 495
1.4 | 450 | 540 | 242 | 67.5
1.7 | 525 | 650 | 242 | 64.9
2.8 | 671 | 1020 | 242 | 62.0
3.0 | 686 | 1100 | 242 | 63.3
3.2 | 700 | 1180 | 241 | 61.0
3.7 | 692 | 1322 | 241 | 58.0 @ 10:07 AM 4/30/2010
4.8 | 719 | 1697 | 242 | 54.0 @ 12:49 PM 4/30/2010
4.6 | 707 | 1640 | 241 | 54.0 @ 1:37 PM 4/30/2010
4.4 | 710 | 1590 | 242 | 54.0 @ 2:07 PM 4/30/2010
3.5 | 685 | 1280 | 242 | 55.0 @ 3:27 PM 4/30/2010
0.9 | 340 | 400 | 242 | 65.0 @ 5:33 PM 4/30/2010
0.5 | 155 | 155 | 241 | 64.0 @ 5:48 PM 4/30/2010