My wonderful STXR2500 is having it's problems today. The weather in Southern California today is great, it's late morning, seventy degrees and the inverter is in the shade. Power production has been down for the last few days so I was keeping an eye on the inverter/datalogger. When the power dropped off to about 250 watts, I checked the sky, no clouds. So I looked at the inverter display and it's indicating "Thermal Derating" and cycling through a 256 watt and 1024 watt max condition.

So, my question is: is there anything I can do? Check the fan, clean the heat sink? I am a hands-on kind of EE so I don't mind getting my hands dirty. Anything but the dreaded RMA and return to the factory.

Thanks,

Tom

All of the above sound like places to start. The fan on my ST runs at anything above 100 watts so if your is the same do you hear it running?
If you are out of warranty there is no RMA on those old models. If you are lucky enough to be in the warranty period Xante will offer a sweet deal on a new GT.

Since the unit is displaying thermal derating, you must have a UPG unit.

This would indicate the unit thinks the heatsink is over tempature, so check that the airflow is clear and the fan is working, beyond that, you have to send it in for service

The old ST/XR are totally different, they turn the fan on regardless at 100 watts (full blast) and don't have derating code, just over temp shutdown

I had one of my develpoment units do this after a lighting storm, a strike took out the CPU card, so if the heatsink isn't hot and or fan is working, its probably something that can't be field repaired

I know they built 500 units ( main boards ) for feild repair stock, so you should be able to have a warrenty unit repaired

The STXR2500 has been so much quieter since the upgrade that I had not noticed that the fan was not running. The unit is hot, the fan spins freely, but it just is not spinning. I assume it's a control or drive circuit. So, it's back to the factory.

I posted on this board after registering a support request with Xantrex. And, after giving up on fifteen minutes of music-on-hold. They automatically sent me a case number. But here I already have two responses. This is a great board. Xantrex support, on the other hand, is not very responsive.

Other things I forgot to mention: The unit is under warranty for six more months. About two years it went down totally and was given a new main board. And, it has another issue:

In the morning, after sun rise but before sun is directly on the panels, the unit hums and my data logger indicates negative power. For a few hours on most mornings it's humming and consuming power, sometimes a couple hundred watts. But this does not happen every day.

I talked to Xantrex support about this problem but it was new to them and they had no clue about what to do. My wild guess is that a leakage path has developed, maybe a FET in the output. I'm not sure that issue will be resolved if it goes back for the fan problem. I'll certainly document the issue but, I'm worried, it might not get fixed.

Sounds like your unit is verifying my over temp code

There is not much to that circuit, turn off the breakers, wait a few minutes, then pull off the front cover and make sure that the fan connectors are plugged into the main board , also give a tug on the two wires, my guess is its either a bad crip on one of the wires or it's not firmly plugged into the main board

also make sure the CPU cable is firmly in place into the main board, if that is lose it could cause what your seeing

When you first turn on the breakers, the fan will come on for a second or two ( this is from memory, as I no longer have any Sunties)

ON the hum, thats NOT good, sound like its not properly calabrated, send it back for this reason alone ( just say it goes into over temp ) and request the main board be swapped

I checked the fan cable connection to the main board. It’s a latching connector and was not loose. Removing and replacing it several times should have “cleanedâ€￾ the contacts.

The ribbon cable between the main board and the controller had the extractor levers glued in place. But, that didn't stop me from giving them a good wiggle. Again trying to improve the contact.

None of that has helped. The fan is still not spinning-up. Since I put it back together it’s putting out about 1500 watts and not doing the Thermal Derating thing. But, the fan is not spinning. Today the weather is fine but a little cooler that yesterday.

After about fifteen minutes it did start the derating again. I will attach a power monitor view.

Send it back for repair, it needs the main board replaced, possibly also the fan

The reverse power flow at low power is very bad, indicating the main board is out of calabration, the fan not working could be fan, main board or cpu card

Feel free to print this out for the techs

I sympathize with your fan issue as I just went through something similar. My Suntie was off warrantee 5 months ago and I went to the garage where my unit is mounted and at 9:30 pm 2 hours after dark I could hear my Suntie Growling, never hearing this before I removed the cover and the fan was quite hot and spinning very slowly. I contacted Xantrex and waited through 45 minutes of muzak and finally got someone who told me they're resident expert on these units wasn't in but maybe the fan is bad. Being an Power systems tech myself I told him well the Drive circuit for the fan must be bad. Well he tried to say its the fan if you want more call tomarrow.
Well I called the next day and got another tech after the long wait.
He talked to me and seemed like he wanted to help. He then gave me a different phone number for a bench tech who works on Sunties but told me
" Don't tell him who gave you this number cause He'll kill me." I promised I wouldn't and called this gentleman. I explained my problem and he responded I need to send it in and couldn't give me a price, and "Who gave you this number" he asked. I responded, a gentleman who cares about customer service, he did offer the $999.00 price on the new unit however I think Xantrex made a mistake following all the other inverter companies with string inverters. My system has areas which shading occurs and in a large series string kiss that power goodbye if one panel gets shaded in the string. Too bad they now swim with the other fish. After removing the main board and tracing the fan control circuit, Its just a triac coupled by an optocoupler to the CPU somewhere. I fixed my inverter with a 1 uf cap in series with the fan, controlled by a relay whose coil is energized by my array or "the input." It works great now. I cannot recommend this type of thing to others however it is frustrating that the inverter itself is already failing and it hasn't paid for itself yet. And on top of that its just the fan control circuit, not the inverter.