Did it blow that fuse even when there was no devices (load) applied to the inverter? Perhaps something downstream is bad, and the inverter is protecting itself the hard way.
The fact that Xantrex no longer makes them is suspicious, and would make me think they had some sort of inherent fault they didn't want to admit too.
Just like most old electronics, the first thing I'd check is for bad or bulging electrolytic capacitors. be VERY careful if you poke around in one of those, as charge caps of the size they use can seriously hurt or kill you!
I prefer to do this type of troubleshooting at dawn or dusk just in case I make a stupid mistake. Before I put in the new fuse, the PV panel strings were generating about 200 VDC and HECO's bus voltage was 240 Vac. The inverter went through its five-minute startup cycle and then displayed "Insufficient solar energy" since there wasn't enough sunshine to convert DC to AC. ("Not enough sunshine" is rated at 195 volts DC or less from the PV panels.) After that it displayed its typical night-time "Inverter offline" message.
I didn't time the next event, but it was suspiciously close to a minute later that the replacement fuse blew. The inverter probably tried to check something (DC voltage? HECO's AC voltage?) and that let through electrons higher than 250 Vac or 20 amps. The circuit breaker between the inverter and HECO's grid is also rated at 20 amps and that never tripped. I think the problem is inside the inverter's AC circuitry, perhaps exacerbated by whatever power is present on the DC side and getting across to the AC side.
I'm not sure whether "downstream" refers to the PV panel DC voltage or HECO's AC bus voltage. But some circuit component seems to have failed and is letting through way too much power.
Xantrex made a pretty good grid-tied inverter 10 years ago, but today the field is very crowded. It's hard to tell whether they've abandoned their gear or decided to move into different markets.
Just like most old electronics, the first thing I'd check is for bad or bulging electrolytic capacitors. be VERY careful if you poke around in one of those, as charge caps of the size they use can seriously hurt or kill you!
Agreed with this. 10 years ago was kind of the peak of "stuff breaking because of bad capacitors". Crack it open and start looking. The bad caps are easy to spot, cheap to source, and easy to replace. All you've got to lose is a couple hours of time :)
I can only see about half of the components without taking off the cooling fins, but all the capacitors that I can see look good.
This inverter has spent 12 hours/day of the last 10 years converting 600 volts DC (and several amps of current) into 240 volts AC. I'd hope that if a capacitor or some other component went bad then I'd see large stains or scorch marks. After I swap it out I'll have to take it apart for a full postmortem and see whether I can fix it.
I'm leaning toward a SMA Sunny Boy in the 4000-6000 watt range. They're a German company but their gear has been around the island for at least the last five years. (I remember snickering about the name the first time I saw it.) They include two MPPT processors to extract the most out of each of the two strings of PV panels, which is probably worth doing for these aging cells. Unlike most grid-tied inverters, it even has a little backup receptacle for limited house power if HECO goes down. 10-year warranty. Better yet, Inter-Island Solar says it's in stock.
http://files.sma.de/dl/18726/SB5000TL-US-DUS143847.PDF (that link downloads the PDF spec sheet)
