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<p class=MsoNormal><span style='color:#1F497D'>Phil,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Good advice. Assuming 48V and a
large system, what would you use as a diversion load and controller in this
application? As I understand it, this would be a DC diversion load, such as a
wind gennie air heater, that would be gradual, resistive, and noncritical for
occasional use in this rare scenario.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Thank you.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Allan Sindelar<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'><a
href="mailto:Allan@positiveenergysolar.com">Allan@positiveenergysolar.com</a></span><span
style='font-size:11.0pt;color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>NABCEP
Certified Photovoltaic Installer</span><span style='font-size:11.0pt;
color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>EE98J
Journeyman Electrician</span><span style='font-size:11.0pt;color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;color:#1F497D'>Positive
Energy, Inc.<o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>3201 Calle
Marie<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Santa Fe, New
Mexico 87507<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>505 424-1112<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'><a
href="http://www.positiveenergysolar.com/">www.PositiveEnergySolar.com</a></span><span
style='font-size:11.0pt;color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Kirpal, </span><span
style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'>The biggest challenge
when mixing brands is dealing with the 300 second timeout after grid
disturbance (what I call 5 minute PWM) make for less than ideal system
operation. There needs to be a better way to regulate power than kicking
the string inverter offline.</span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Imagine, say, a 7kW
array pumping energy into the home on a beautiful sunny day. The grid
goes down, but the battery based inverter (BB) picks up the slack and the
grid-tied batteryless inverter (GT) stays online. Home is drawing less
power than the array’s output (~6kW worth), and the batteries are
full. Battery voltage hits the regulation voltage, and the BB inverter
(or the voltage controlled switch) activates a relay to open the circuit to the
GT inverter, effecting a blackout on that circuit. Suddenly the BB
inverter and the battery bank is hit with the full 6kW of load. The
batteries are a little undersized because that was the easiest portion of the
system to cut costs on, and they’re a little old and dried out from years
of sitting in an uncooled garage, so their voltage sags under the load.
The voltage controlled switch senses the drop, and closes the relay to
the GT. However, the GT has to stay offline for another 299 seconds and
the battery voltage continues to fall…..</span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I’ve been
worried about just this scenario for some time, especially as systems age.
Therefore, I’ve been suggesting to anyone interested in using mixed
brands of inverters (or those who don’t want to use RS485 communications
with SB/SI combos) that they strongly consider installing a diversion load and
controller capable of absorbing at least the majority of the expected surplus
energy. A blackout relay can be used as a secondary control mechanism.
I think that this is going to provide the most reliable operation,
ultimately.</span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Phil
Undercuffler</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Director,
Battery-based and Off-grid</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Distribution
Sales Group</span><o:p></o:p></p>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Conergy</span></b><span
style='font-size:10.0pt'> </span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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