Bill:
Good question. I called Enphase back and they say it is definitely a
hardware problem. There are at least two registers that indicate AC line
voltage and in this case they disagree, with VRMS indicating zero. Enphase
has advanced diagnostics they can call up on-line, apparently.
William
At 09:49 AM 11/27/2012, you wrote:
William
Double check your voltage drop on the AC branch circuits, and make sure
that you consider your wiring between inverters. Remember that voltage
drop is additive and each inverter will see a slightly lower voltage drop
which could account for the voltage over error, especially if you are
seeing it at the end of the string. Enphase does have a white paper on
that and they are now recommending splitting long strings int he middle to
make to branch circuits out of one now to alleviate this problem. The
White Paper explains this in more detail. There was also a Solar Pro
article describing how voltage drop can result in voltage rise at the
inverter, and I have seen and measured this with a meter. Maybe the
inverters are correctly reporting the voltage rise?
Bill
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