Weird Inverter Issues

Early this winter, I wrote the following to a well-known Trace/Xantrex tech in Redmond, Oregon. The saga continues, with recent developments, but this is the background through late November. (For those who will immediately jump on the China Diesel/Mecc Alte combo, some of these things were occurring before with a Yamaha EF12000DE, too.)

Anyway, flashback to November...

[I have a fully off-grid setup with a Trace SW4024D Integrated Power Panel, self-installed in 2001. My current genset is a 1998 Hardy Diesel (Shanghai Tractor variety) with Mecc Alte 15Kw. Got this with less than a hundred hours on it from an unfulfilled Y2k survivalist in Northern Idaho--runs great, churns out a steady 120/240 supply on teaspoons of diesel.

My #1 inverter, though, has taken to drawing the voltage on its leg up, up, and up--until it either loses sync, or pops the 35-amp breaker out, or simply stops drawing power even though it's still showing sync on the display. While #2 shows 120 volts inverter and maybe 121 or 122 genset, and draws steadily at or near max charge amps, #1 starts that way and then drifts steadily up until inverter voltage is as high as 130, genset voltage at 133 to 135. If it doesn't pop the little breaker, it'll sit there showing sync but with 0 input amps. I've tried several different diagnostic configurations on consultation with Erick Bentsen and "Thomas" at Schneider Electric, who currently handle tech support.

With minor variations according to the scenario, this behavior from #1 occurs in all the following configurations: 1) swapped hot leads from the generator between #1 and #2--no change whatsoever; 2) Moved inputsfrom AC2 to AC1--no change; 3) Removed series stacking cable--no change in #1, but #2 now shows a corresponding DROP in inverter and genset voltage, as you might see with an unbonded neutral when the two legs vary widely but still add up to 240. Genset always shows balanced voltage at about 122 or 123 when breaker to inverters is open--nor does it seem to vary much when I bypass the inverters and apply loads to either leg.

I'm assuming that whatever is happening is on the charger side, as the inverter function still seems to be perfect on both legs of the household circuit--120 volts on the nose, with no peculiarities.

I'd appreciate any guidance you can offer. I believe my present difficulty may be a further evolution of the "hunting" problem back when--a wandering demand from the #1 inverter that surely contributed to the demise of the Yamaha. Now, though, we're rapidly approaching the point where there'll be no load on the leg to #1, which will eventually trash the generator. Thus far, the genset doesn't seem much troubled--I guess it's a big enough set that even this unbalanced draw isn't working it too hard--but that can't go on forever.]

End flashback. Update--on Dean Abney's advice, I did some tinkering with the max charge amps, max volts, and whatnot between the two inverters, and achieved a reasonable balance. At least the 35 breaker button quit tripping. THEN, however, as we've always had plenty of extra power in the summer, and because our Crystal Cold gas fridge was giving us trouble, we bought a Kenmore 21-cubic foot electric fridge for summer use. What I've discovered with this, now, is that when I'm charging the batteries, I can't turn off the generator while the fridge compressor is running--or, when I come back into the house and look at the power panel, the top inverter is buzzing and showing an error light AND AN AC INPUT LIGHT...as if the bottom inverter was somehow backfeeding through the fridge compressor motor into the top inverter, or...or...or... Hell, I don't know. Anyway, if I go in and turn off the fridge and turn it back on, the problem goes away--no error light, no AC Input light, and normal operation is back. If I wait until the compressor is not cycling to go turn of the genset, no problem.

Any ideas, folks?