I just installed a STXR2500UPG with 960W solar array. Unfortunately the cloud cover was so heavy it required having to turn the light on in the house to read the instruction manual. But it was able to churn out 180 watts with bursts of 500 watts. This is the first day of use so I am not sure whats normal. Intermittanly I heard a odd knocking sound at about a 2 hz rate. Has any one else experianced that? Is that the fan running on slow speed? Also is it also normal to it to continually go through the restart delay at the end of the day as the last of the sun sets? It stopped when the sun whent down.

Thanks

PS I originally bought a ST1500 (pre UPG) It took 20 minutes to find the what it thought was the MPP the UPG is almost instant!

First , Understand 960 watts is at "Standard Conditions" , that being the cells are getting 1000 watt/meter/square irradiance , and the cell tempature is 25C (77F)

solar panels if roof mounted are typically in the 50-75C range and I have yet seen a location that gets 1000 wmsq in clear conditions

solar panels (12 volt nominal) drop there voltage output .08volts per "C" above the 25C rating. So if your at 50C , thats 25 * .08 or 2 volts ...

Solar panels are rated by voltage time current. This is call vmp (voltage maximum power) . Silcon Solar panels this is typically 17.2 volts ... so if your panel is rated at 7 amps , it would be a 7 * 17.2 = 120 watt panel. This same panel at 50 C would be 15.2 * 7 = 106 watts. Now throw in that typically peak irrances is in the 900-920 range (not 1000) and we have a real world picture of the panels performance of 15.2 * 7 * .92 = 97 watts

If the above is a bit confusing short story is your 120 watt panel peak performance will typically be 80% of what its labeled at.


Next is the Suntie itself. It is rated at 91% at 1400 watts ... at 500 watts , its in the mid 80% ( all inverters run at lower effficiencys at less than the peak efficiency power point)


So add all this together and you have a 960 watt array * .80 (panel deratings) * .85 ( inverter efficiency) = 650 watts peak AC


In cold weather or in partly cloudy weather where the sun get maginifed by the edge of cloud refraction , you will see higher peaks , but for a good expectation , 650 is what to expect. This assumes you have use approprate wire for the solar panel and inverter interconnections

The womp-womp is the AC fan , it is modulated for speed control and has some noise , while not silent , it is way better than the on full at 100 watts and above the older models did ..

Yes at low light conditions , the Suntie will loop trying to restart power harvesting , nothing to worry about there

If you want to have fun with your Suntie , read up on FishBowl , get and otpo isloator and you can watch from the comfort of your home the performance of your Suntie and also log its performance

Hopefully you get some good sunnydays soon to watch it perform

Thanks for the info My main consern was the noise and repeated restarts. I was expecting around 767 watt which is the CEC rating for this combination. Today cleared up and I saw it at 830 watts. I was thinking as the fan is mounted horiz every time the power is pulsed it pull the rotor of the fan up and makes the knocking sound. I hope that when the pulse rate increases the noise will stop. We'll see...

I was wondering this when I tested first time my ST2500... Why in the earth the fan needs to run at ~100W power level when the weather was cool (60F)? When I was repairing the SunTie I noticed a thermocouple or PTC or NTC resistor glued to the heat sink. Since the inverter is mostly software controlled shouldn't take too much code to add adaptive fan control that measures the heat sink temperature and output power and then decide when to turn on the fan... I guess the new version of SunTies have this "fixed" as you explained...

I'm more thinking now to dump my ST and get the fanless GT series inverter...

The issue is the Suntie Fan is a 230VAC fan. AC motors to be speed controlled need to be variable frequency, adjusting the voltage doesn't do much but stall and burn up the motor

The UPG uses and algorthim that at 60HZ, pwm's the fan. So for example, for 50% speed, every other 60hz, the control triac is turned off. Since the Micro is synced to the line frequency, it actually does a fair job at speed control and with the UPG, its varable to the heatsink tempature.

A proper design would use a DC fan and have varable voltage control, but I did the best with what was there and its way better than full speed at > 100 watts your model does