Xantrex Grid Tie Inverters Work Intermittently

CoinMLS

I have an 8.5 year old 8kW system with 2 Xantrex GT 3.8 Inverters (3.8kw). One inverter was replaced after about 6 months of use but has been fine since. The installer is no longer in business. I am very handy and have an Electrical Engineering degree but I don't have much experience in this area. The whole array is on the same surface with the same sun exposure in Phoenix, AZ.

Lately I have had noticed that the system is working intermittently. Sometimes one inverter is online producing 2500-2800W (fairly normal value) and the other is "Inverter Offline." Then sometimes the other system works and the other is offline. Sometimes they are both working. Today it was sunny all day, they were both off until around 2pm when one of them started working. The other never did.

Here is what I have determined so far:

1. There are no faults displayed by the unit

2. Both units show ~300Vdc coming in from the solar array on my DVM whether the inverter is online or not. I think this rules out array or wiring issues to the array.

3. Fuses in both units are fine.

4. I have not yet removed the cooling fins to inspect behind those components.

5. I have tried switching them on and off

Any ideas? I find this to be really a peculiar failure mode, and I'm really surprised that it affects both units.

mike95490

Try using the multimeter to measure your household AC line voltage.  With a lot of solar in neighborhoods, or sometimes with insufficient feeder wire gauge, the Line voltage can rise ABOVE spec and the system shuts down.

CoinMLS

Thanks for the reply. I don't think either of those are the problem, after all, the system has worked for over 8 years. The wire appears to be 10 or 12 AWG which should be fine. L-L voltage was 241V, each leg was 120Vac. Voltages similar on both units. And again today, one was working, the other was not at one time. Today, 1 unit ran for 2 hours, the other for about 4, and they should have run all day, it was not cloudy at all. It seems to be consistently that they run late in the day.

littleharbor2

Maybe unrelated but thought I'd mention. These inverters had a problem (I honestly don't know what the problem was) that was fixed by xantrex. The indicator, as I understand it is the addition of the small label at the very bottom right of the data label on these inverters. The ECO-7779 label on the upper photo is the one I'm referring to.  Not sure if this repair was required on the 3.8 Kw models.

 

CoinMLS

I was just looking at that last night. I did submit a recall claim 2 years ago and they sent me some kits that I never got around to installing. Looks like it is to replace 2 capacitors near where the solar voltage comes in. The problem was that these capacitors were exploding. Mine look fine. I'm going to take the fins off and visually inspect the rest of the caps today. I'm thinking it's got to be capacitor related as maybe it takes several hours of generation to get it to work with some degraded/damaged capacitors.

BB.

There was an issue with input capacitors on some of Xantrex's product line. There were something like 4 capacitors that failed... Two or three they could read the lot code (all from one lot). And another that they could not... So, being conservative, they decided to replace all the capacitors.

As I recall, these were polyester capacitors--And if they fail (overheat/arc?) they release acetylene gas as they decompose (possible flammable/explosive issues).

This was from a hand full of years ago. I don't have any other information.

-Bill

CoinMLS

I can't seem to figure out how to "get the fins off." The units are still hanging on the wall and connected, I'm trying to avoid disconnecting and taking them down if I can avoid it. I'm wondering if there's something I need to pry or persuade a little bit but I don't want to damage or bend anything. I removed screws on the top and on one side. Any help or ideas are appreciated.

mike95490

You don't take the fins off. That's about 10lbs of extruded heat sink with lots of circuitry built on the backside (that's the FETs and drivers)    The whole works (box) is on a hanger and you take it off the wall, and the dealer gives you a replacement.    Unless you made pry marks and dents trying to open a box with no consumer replaceable parts.  

CoinMLS

Thanks for the info. Not sure I'll get a replacement unless I buy one, it's out of warranty. Nice thought that someone would just give me one though. I wanted to check the condition of the capacitors, if there are any more behind the fins. I haven't caused any damage. Is there anything else to look for then?

mcgivor

This link has info regarding the capacitors.
https://solarindustrymag.com/schneider-recalls-xantrex-solar-inverters-due-to-injury-hazard/

CoinMLS

I did install the new capacitors, no improvement (I didn't expect any). I guess I will call the inverter repair people.