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<div class=Section1>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Kirpal,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Lots of good suggestions so far here, but here’s my take:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Unless there is a very high water need during the daytime hours,
most of the time the PV array will be sitting there just doing nothing, which
is what happens in most pressure systems. You would be better off just using an
AC pump (like the Grundfos AC-only SQ pumps) run from grid power. Then put the
PV on an intertie system to offset the power usage. Since a PV-direct pump won’t
give you water during a grid failure at night, the idea of running the pump
with the PV at all is not very useful. How often goes the grid go out during a
sunny day?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If the grid goes out a lot, you should install a grid-tie system
with battery back-up. That’s the only way to also have water at night
during a power failure.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Another thing that you could do is to go ahead and use an SQFlex
pump, but match the PV array voltage to a grid-tie inverter so that most of the
time it’s connected to, and selling to, the grid. If you do have a power
failure during the day, use a manual transfer switch to switch the array output
directly to the pump (the SQFlex can handle DC up to 300V). You could probably
automate this if you use a DPDT transfer relay held closed by the grid, but
defaulting to PV direct if the grid goes down.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Unless you have some compelling reason, I just don’t see
having a PV array just sit there most of the time not being used.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Brian Teitelbaum<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>AEE Solar<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Kirpal
Khalsa<br>
<b>Sent:</b> Thursday, May 20, 2010 12:28 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> [RE-wrenches] Grundfos SQ FLEX AC/DC auto switching<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi Folks.....I am working on putting together a domestic
water pumping system using a grundfos 11 - SQF - 2. This system will be
connected to a standard pressure tank and cistern and have a solar array
providing primary power. However at night and on cloudy days we would
like the system to switch back over to AC power from the grid. I know
that the grundfos IO 101 switch box allows the pump to use an AC source and
when the AC source is removed it<u> automatically</u> switches back to DC.
What I am looking for is when the DC source (solar) is not available it <u>automatically</u>
switches over to AC power (grid) ( the reverse of what the IO 101 switch does)
and when the DC becomes available again it again <u>automatically</u>
switches back to the DC power (solar). <o:p></o:p></p>
<div>
<p class=MsoNormal>Has anyone done this? Any recommendations for
configuring this set up. We are looking to provide solar water pumping
during the day both when grid is present and when their is a power outage and
AC pumping at night or cloudy weather all without battery back up.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Thanks in advance for any advice.!<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>-- <br>
Sunny Regards,<br>
Kirpal Khalsa<br>
NABCEP Certified Solar PV Installer<br>
Renewable Energy Systems<br>
<a href="http://www.oregonsolarworks.com">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o<o:p></o:p></p>
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