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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Hi Gary,
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">The SQFlex is current limited to 8.4A regardless of voltage. I have not had positive experiences running SQFlex from DC voltage from
a battery. It can work, but you will not get full output volume if you are restricted to 48VDC. The SQFlex is really designed to work with higher DC voltages up to 300 VDC from PV arrays. We run many at 120VDC PV direct and that works well. I expect, not tested,
that a 120VDC battery bank would also run it well but that is uncommon. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Have you considered having a second small inverter from the battery to fulfil customer's request for redundant power supply? Lots simpler.
That is what we ended up doing on a few sites we did try DC, 24V 600W inverters are low cost and simple. Or could you switch some of the PV to use as DC-direct as a backup?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Kevin<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> RE-wrenches [mailto:re-wrenches-bounces@lists.re-wrenches.org]
<b>On Behalf Of </b>Gary Higbee<br>
<b>Sent:</b> August-21-18 11:18 AM<br>
<b>To:</b> re-wrenches@lists.re-wrenches.org<br>
<b>Subject:</b> [RE-wrenches] DC-DC converter for SQFlex<o:p></o:p></span></p>
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<p class="MsoNormal">Hi Wrenches,<o:p></o:p></p>
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<p class="MsoNormal">I\u2019m assisting a customer and well person in replacing a failed Lorentz ETApump (after 15 years of intermittent use). We\u2019re looking for a quality DC-DC converter to power a not-yet- ordered Grundfos SQFlex 6 SQF-3 from a 24 V Surrette battery
bank (wish it was 48!). The pump draws a max of 8.4A and the curves say we\u2019ll need about 600 watts so I figure we\u2019d want at least 70 volts out. Ideal would be a higher DC output, say 200V (save a couple hundred feet of larger copper, greater efficiency) and
at least 3A (see questions).<o:p></o:p></p>
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<p class="MsoNormal">The primary power source will be 240V AC but my customer wants a fallback for battery operation. We plan to use the Grundfos IO 101 SQFlex switch box, which will switch to DC if the AC fails. Also the CU 200 SQFlex control unit, so we can
accommodate the existing float switch up the hill, etc.<o:p></o:p></p>
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<p class="MsoNormal">The Grundfos tech person I spoke with today said the DC system should be able to supply 8.4A, regardless of the DC voltage.The pump curve says we need 600W for maximum performance at the lift we\u2019ve got. It seems to me that if we\u2019ve got
200V and need 600W we\u2019d be drawing 3A. Yet if the Grundfos factory line is there should be 8.4A available that\u2019s 1680W. The tech guy said he didn\u2019t have specific information why we\u2019d need 8.4A regardless of pump input voltage. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The Grundfos Product Guide says:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>Max. ratings are as follows:</b><o:p></o:p></p>
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<p class="MsoNormal"><b>\u2022 Maximum power input (P1) of 1400 W</b><o:p></o:p></p>
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<p class="MsoNormal"><b>\u2022 maximum current of 8.4 A</b><o:p></o:p></p>
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<p class="MsoNormal"><b>\u2022 maximum speed of 3600 rpm </b>(think I read somewhere it\u2019s 3000 rpm for this helical rotor model)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>The pump delivers its maximum performance when one of the above parameters is reached.</b><o:p></o:p></p>
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<p class="MsoNormal">Two questions:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">1) Do any of you have experience running the SQFlex on DC, and what to make of the 8.4A at any input voltage factory recommendation? Maybe basic amps/volts/power calculations aren\u2019t applicable given the pump electronics?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">2) Are you aware of any DC-DC converters that will get us from a nominal 24V battery bank to 200V, or somewhere between 70 and 200V, with an appropriate current limiting amp rating to get us at least 600W (depending on thoughts regarding
the above question)?<o:p></o:p></p>
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<p class="MsoNormal">Thank you,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Gary<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Gary Higbee<br>
Windstream Solar<br>
Oregon License 17LRT<br>
Renewable Energy Consulting<br>
<a href="mailto:gary@windstreamsolar.com">gary@windstreamsolar.com</a><br>
541-954-3881<o:p></o:p></p>
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