Hello,

I have a old ST 2500 Watt Inverter (XSTXR2500UPG) that has performed admirably the last 5 years. Lately its production has dropped by about 50% which seems to be due to multiple AC Voltage Faults and the associated 5 minute restarts throughout the day. When I have been able to catch it during one of its "faults", the message "AC NOT PRESENT" is on the LCD. When I measure the voltage and frequency on the Inverter side of the AC Breaker, everything is in spec as best I can measure, so I am very skeptical that is an actual voltage fault. Some time later the fault will clear and the Inverter will function as normal with the production very good.

Has anybody had a similar problem? Is there any chance of a loose connection somewhere inside the ST that I could check? I have not ruled out replacing the unit but for this site, the low voltage strings of the ST are actually ideal. I have 32 BP 75 Watt 12 Volt modules wired as 8 strings of 4 modules. There is significant shade from different sources throughout the day which may shut down a few strings at a time but the others keep producing. If I were to replace the ST with a GT2.8, I would have to wire is as 2 strings of 16 modules. Some shade with that configuration could take out 50% of the power output easily and I would not be much better off than where I am now.

Any info would be appreciated.

Id check all the connections to the breakers and the wires connections that go into the main board, the lugs can loosen over time and could cause intermittent issues

Hi Solar-Guppy,

Thanks for the quick reply. I did check all connections up to the Main Board. I even bypassed the Breaker in the unit and disconnected the surge arrestor just to be safe. I measured good voltage on the terminal block on the Main Board right behind the Comm Board.

Have you ever seen this sympton in all your testing of the ST Inverters? Thanks for your help.