Xantrex AC voltage fault problem

[solarix]

I'm looking for help on a puzzling problem. Have a site we installed dual Xantrex inverters (2.8 + 5.0kW) inverters about 4 years ago back before anybody made a 7.7kW size. About 8 months ago the smaller one started having AC voltage faults. Being a dual installation, with the two of them on the same AC combiner - we figured it had to be a faulty inverter and Schneider replaced it no problem under warranty. We never were able to observe the AC voltage being abnormal and the larger inverter has never had any sign of the same problem. There is also an SMA inverter on the house next door. Then after about 4 more months, the replaced inverter starts having the same problem intermittently. We checked it and checked it, replaced the breakers in the combiner, AC voltage always ok - even all the way into the main board of the inverter. Schneider had us replace it again. Now guess what? - the 3rd one is doing it again! They promise me this is not some generic problem with these inverters and are having us get permission from the utility to allow modifying the software to increase the AC voltage range. I'm dubious. The standard upper limit is already 261Vac. We've never seen more than 246Vac at this site. The only thing that hasn't been replaced is the Xantrex DC disconnect switch. Another clue is that I happen to have a similar vintage 3.3kW Xantrex inverter as part of my own system and I've found that it's indicated AC voltage as high as 259V even though when I measure it directly with a meter it is actually 246Vac. People wonder why I'm strident about inverter reliability....
Anybody else seeing AC voltage problems with their Xantrex inverter?

[Mike90250]

Check the wire connections between the inverter and the transformer on the pole (or underground vault).
You may have a bad splice, copper creep under a set screw in your disconnect or breaker box, or meter box. Also,
see about getting a power quality monitor, that can measure and log spikes, line voltage, phase imbalance. That may help show up something.

[SunEagle]

Check the wire connections between the inverter and the transformer on the pole (or underground vault).
You may have a bad splice, copper creep under a set screw in your disconnect or breaker box, or meter box. Also,
see about getting a power quality monitor, that can measure and log spikes, line voltage, phase imbalance. That may help show up something.

Good suggestion about using a power quality meter. Surprising even a minimal amount of transient voltage spikes (or harmonics) generated by the POCO can hurt electronic equipment like an inverter.

[inetdog]

Good suggestion about using a power quality meter. Surprising even a minimal amount of transient voltage spikes (or harmonics) generated by the POCO can hurt electronic equipment like an inverter.

And it would not be surprising if the two size inverters had a different sensitivity to spikes and dips. Especially if one is an older design than the other.