Wrenches, Thanks, all, for your responses. This recently retired ER Doc customer does have an inverter system (old SW’s, one not so good on the scope). Grid and also two generators, Wanted a DC solution also. I like the Grundfos pumps so far, not their opinion to double the battery bank so it’s 48 and use their charge controller. I see their expertise is AC only, or PV-direct DC. Yes, there’s likely a DC-DC solution, somewhere out there, and it can be worked out given enough money and research. Seems Grundfos somewhat admits this. Good pump no matter, it seems. AC or PV-direct.
Take care, Gary Gary Higbee Windstream Solart g...@windstreamsolar.com 541-954-3881 > On Aug 21, 2018, at 11:17 AM, Gary Higbee <g...@windstreamsolar.com> wrote: > > Hi Wrenches, > > I’m assisting a customer and well person in replacing a failed Lorentz > ETApump (after 15 years of intermittent use). We’re 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’ll need about 600 watts so I figure we’d 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). > > 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. > > 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’ve got. It seems to me that if we’ve > got 200V and need 600W we’d be drawing 3A. Yet if the Grundfos factory line > is there should be 8.4A available that’s 1680W. The tech guy said he didn’t > have specific information why we’d need 8.4A regardless of pump input > voltage. > > The Grundfos Product Guide says: > > Max. ratings are as follows: > • Maximum power input (P1) of 1400 W > • maximum current of 8.4 A > • maximum speed of 3600 rpm (think I read somewhere it’s 3000 rpm for this > helical rotor model) > > The pump delivers its maximum performance when one of the above parameters is > reached. > > Two questions: > > 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’t applicable given the pump electronics? > > 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)? > > > Thank you, > > Gary > > Gary Higbee > Windstream Solar > Oregon License 17LRT > Renewable Energy Consulting > g...@windstreamsolar.com <mailto:g...@windstreamsolar.com> > 541-954-3881
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