I just bought a house that had an existing PV system using a STXR-2500, manufacture date April 2002, probably been in service since early 2003 when the house was built. I haven't observed it closely, but on avg it seems to generate about 6-10 kwh per day (panels are angled about 30 degrees to the west, so not ideal placement). I don't know what the expected output is, I'm new to solar.

The inverter unit makes a fairly loud rumbling noise while generating, which I assumed was the cooling fan. I opened it up to clean out the dust and check the fan, and it seems to spin freely and smoothly. It could still be a fan problem, but I thought I'd ask if it's normal for the unit to make noise?

Is there any way to get more data to show on the LCD so I can tell if everything is working properly? Currently it only shows kwh output for the day. I did read about fishbowl, but it sounds like I'd need to track down an opto isolator to be able use that.

Also, I'm wondering if I should just replace this inverter rather than futz around with it? From reading other threads here, it sounds like few STXR units are still in service, and there might be the possibility of getting a discounted upgrade through a loyalty program? I would appreciate any info or advice about that.

Thanks

If your LCD only show kwh than its an older unit that didn't get the updates in 2003, which do make a difference in harvest. In very general terms, take the name plate wattage of the PV on the roof and multiply by 4 for a sunny day and that is a ballpark what you should see for kwh for the day.

As to changing out the inverter, if you call up the customer support and tell them you have a dead Suntie, they will likely offer you a discount for a new GT2.8 for 999.00 or that was the deal I last heard about. Keep in mind, the Suntie is a 48V-100V input and the new GT's are 200V-600V, which means you have to run the panels in series, which requires technical knowledge to do.

Or, leave it as is to the inverter dies ... its free power even if its isn't harvesting 100% of what it should

Thanks Solar Guppy!

I confirmed that the noise is coming from the fan, so at a minimum I need to replace that.

Regarding the output of the system, I got out a ladder today and checked the modules. There are 55 modules, BP Solar Millennia model MST45IHS, rated at 45 watts max. (I can't find any data sheets for these modules, but it appears that these were originally designed by Solarex, which later became part of BP.) Since they are 8 yrs old, I'll consider them to be 40 watt modules. Applying your rule of thumb, 55 * 40 * 4 = 8.8 kwh. Today was mostly clear and sunny, and the harvest was about 9.2 kWh according to the Suntie, so that's in the ballpark.

I also ran the pvwatts v1 calculator to estimate the system output (http://rredc.nrel.gov/solar/calculators ... /version1/). According to it, the avg daily output for June should be about 9.7 kwh (with the panels derated by 10% due to age). Today's harvest should have been above average, given the clear weather, so according to this calculator the system does seem to be under-performing.

Any other thoughts or suggestions? Thanks!