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Wrenches:<br>
The situation: Two Grundfos SQFlex stand-alone pump systems, each
with IO101 AC switch and CU200 controller in a remote application,
filling a common tank two miles away for a community water supply.
As a float switch can't be used to shut off the pump when the tank
is full, the mainstream pump company doing the full community water
supply installation (we have contracted only the pumps and PV power)
has specified and supplied a pressure transducer-based system called
P2Flow (<a class="moz-txt-link-abbreviated" href="http://www.p2flow.com">www.p2flow.com</a>) as a stand-alone way to control pump
operation using a high-accuracy pressure transducer at the well
outlet to signal a programmable controller. The P2Flow control unit
draws 40mA when "on" and 30mA when "off", running on 10-30 VDC,
which I am supplying with PV. As 40mA @24 hours is one Ahr/day, I
have specified a 10W module and 7 Ahr sealed battery at each well.<br>
<br>
The problem: The float switch control Grundfos CU200 controller is
preprogrammed to "close on rise" - that is, continuity between the
terminals turns the pump off. The P2Flow system is "close on fall",
as would be used to directly interrupt continuity of power to the
pump when the tank is full. These are opposite logics. How can I
reverse the action in the simplest (for reliability) and
lowest-power way? I could add a second relay to reverse the action,
but that would increase the power consumption beyond what this tiny
power supply can produce: at 0.9 VA coil current rating, an ice-cube
relay would draw double the current of the P2Flow unit itself. I
have heard of using a 10K ohm "pull-up resistor" but have no idea
how it works. <br>
<br>
Any good ideas, please?<br>
<br>
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<p class="MsoNormal" style=""><span class="il"><b style="">Allan</b></span><b
style=""> Sindelar</b><span style="font-size: 10pt;"><br>
<a href="mailto:Allan@positiveenergysolar.com"
target="_blank"><span class="il">Allan</span>@positiveenergysolar.com</a><br>
NABCEP Certified Photovoltaic Installer<br>
EE98J Journeyman Electrician<br>
<b style="">Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b style="">505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/"
target="_blank">www.positiveenergysolar.com</a></span></p>
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