SW Tripping DC 250 Breaker [RE-wrenches]

[Travis Creswell, Ozark Solar]

Hello All,

I've recently set up a weekend hunting property with a pair of rebuilt
SW4024MC's stacked for a 120/240 output.  One string of Surrette 4KS25PS
rated 1904 AH @ C/100.  Outback PSDC with a 250 amp breaker for each
inverter, a pair of 4/0 cables less than 8' long for each inverter.

Batteries have been equalized. All cells check out fine with the
hydrometer with no variance and their voltage stays within .05 volts
loaded and resting.

The inverters start and run the 2 wire 3/4 hp 240 well pump easily.
Trimetric read less the 65 amps for the well pump.  No problem with the
120 volt RV rooftop Air Conditioner either.  TM reads 80-85 amps while
it's running.  Unable to get starting surge readings with my clamp-on
meter that day since it had failed.  From my experience the TM meter
doesn't read near as fast as a clamp on with the "peak" feature.  My
estimate is that starting surges are twice I'm seeing on the TM.

If the RV air is running WHEN the well pump tries to start, the 250 amp
breaker trips on the SW4024 that the RV AC is on before the pump can
start. I can watch the amps on the TM climb to just under 400 before the
breaker trips.  Remember that the TM is a little slow so I'm guessing
that means something like 600-800 amps.  The 4/0 battery cables don't
even get warm while this is going on.  My fluke 87 was working that day
and I was able to record the lowest AC voltage as 205 from phase to
phase.  The TM shows the battery gets pulled down to the lower 21's.  I
did this at least 5 times and not once did the inverter give an over
current error message.  I'm really confused at this point because I set
up a lot of stacked pairs of SW's and they have always ran anything I've
asked them to.

While on site I called Xantrex tech support.  They suggest switching the
RV air conditioner from one inverter to the other but not to reverse the
well pump.  After doing that, everything works fine?????  The tech
support person wasn't really able to adequately explain to me what was
going on (I don't think he really knew) but he blames it on the well
pump.  So what's going on?  Is it the well pump?  If it is how do I
articulate this to the well service guy and the customer?

Thanks in advance,

Travis Creswell
Ozark Energy Services, Inc.
Joplin, MO 

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