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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hello Wrenches,</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We’ve installed 2 sunny island systems, and were
planning to install three or four more, until we identified what I consider to
be a serious functional deficiency with the product. In commissioning the first
two inverters (different customers, but around the same time) I found that the Sunnyboy
inverters that were feeding the island would error out for AC frequency tolerance
exceeded when the inverter was in backup mode (no grid signal present) and the
batteries were mostly charged with charge current coming in from the array. The
SI frequency modulates to reduce battery charge current and control battery
voltage to absorption or float voltage – this causes the SB to error,
wait 5 minutes (because frequency returns to normal once charging stops) then
restart and error out again. This is particularly problematic with a smallish
battery bank and largish array as voltage can go high fast.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>When I first reported this to SMA tech support it was
described as a communication problem. Apparently if the two inverters are
communicating, the SB is informed by the SI that it needs to operate in
off-grid mode and it should disregard the normal grid frequency tolerance. So
after a few return trips with new RS-485 cards and checking and double checking
the com wires to no avail, I was told that this was a firmware bug and that a
fix could be expected in some months, but with no solid time frame commitment. An
alternative was presented that the SB can be reprogrammed to run in off-grid
mode permanently, but since our systems have an inverter bypass transfer switch
in then we could not do that, because if that switch is switched then the SB would
be connected directly to the grid without the isolation of the SI, and would
take responsibility for anti-islanding. That’s clearly a no-no. </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The transfer switch at the time was a requirement of the
utility (all loads must be able to be served directly by the utility if
necessary). This requirement was just removed by the </span></font><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>PRC</span></font><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>, but there
are serious design issues that are unacceptable in my eyes with removing the
bypass. </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>1)<font size=1
face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font></span></font><font size=2 face=Arial><span style='font-size:
10.0pt;font-family:Arial'>If the sunny island breaks, there is no option to power
the critical loads directly from the grid. We sell battery backup systems so
that people have reliable power to their critical loads. This would be clearly
a better designed system if the inverter could be bypassed. The other backup
systems, like outback and Xantrex (DC coupled) have easily integrateable and supported
transfer switches for this purpose – as they should. </span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>2)<font size=1
face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font></span></font><font size=2 face=Arial><span style='font-size:
10.0pt;font-family:Arial'>If the inverter was out for repair (say it’s
out of warranty, and has to be sent for repair, not just quickly swapped out)
the sunny boy would be down too as there is no alternate path to the grid. With
a bypass/transfer, the customer could still be producing power and net metering
while the backup system is down.</span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>3)<font size=1
face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font></span></font><font size=2 face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Because the SI is 120Vac, and the SBs are all 240 V, this
means there must be a transformer, or two inverters (and most people don’t
need 10Kw of backup power). Some customers would choose to forgo the automatic
backup in favor of eliminating the efficiency loss of the transformer in day to
day grid-tie operation by leaving the bypass switch activated except during a
power outage, and manually activate the backup system only when it’s
needed. This is a less critical issue, but having the option would be better.</span></font></p>
<p class=MsoNormal style='margin-left:.25in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Page 122 of the SI manual warns that if the batteries are
full, the frequency shifts and the inverter shuts down, but this is not quite
true. If the battery is small relative to the array size, the voltage will
shoot up fast, even when it is at a lower state of charge. It appears to be an
all or nothing charge – no tapering. I watched as one system continued to
go down In SOC until it got to the low eighties. I did not stick around to see
how low it would get. I reconnected the grid and promised the customer to try
to get to the bottom of it. 95% of the time during this test the SB was
completely disconnected. Because it waits 5 minutes to reconnect, it doesn’t
even work as well as the old series charge controllers (like the Trace C30A).</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>When we were designing the systems, we sent one-line
drawings to SMA to make sure it would work the way we wanted, and they were given
the thumbs up. This includes a more complex arrangement on a 3-phase service that
has not been installed yet and is on hold. We do not want to install any more
of them until this is resolved. We have customers with battery-less systems
that would like to retrofit. We’ve told many of our customers that if
they want to add battery backup later they can. I’m anxious to see the
fix.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Has anyone else seen this problem?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Does anyone have a solution?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Do any of you have systems that might have this problem, but
haven’t been put to the test?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Am I missing something in the programming and tech support
just hasn’t caught it?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Any help would be greatly appreciated</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks,</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoAutoSig><font size=5 color=green face=Coronet><span
style='font-size:18.0pt;font-family:Coronet;color:green'>Mark Drummond</span></font></p>
<p class=MsoAutoSig><font size=3 face="Palatino Linotype"><span
style='font-size:12.0pt;font-family:"Palatino Linotype"'>Field Manager</span></font></p>
<p class=MsoAutoSig><font size=3 face="Palatino Linotype"><span
style='font-size:12.0pt;font-family:"Palatino Linotype"'>Positive Energy, Inc.</span></font></p>
<p class=MsoAutoSig><font size=2 face="Palatino Linotype"><span
style='font-size:10.0pt;font-family:"Palatino Linotype"'>NABCEP Certified PV
installer</span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
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