[RE-wrenches] Grundfos SQ FLEX AC/DC auto switching

[Exeltech]

Could be as simple as installing a DC relay of appropriate coil voltage and contact configuration & ratings.  Then, use the PV to power the relay and the contacts to select your preferred power source.  The necessary hysteresis inherent in relays would be present.  Select a relay for the environment (enclosed is usually best), and wire it safely.  This is just one option - but it uses off-the-shelf parts and ought to be easy to configure.


Dan



--- On Thu, 5/20/10, Kirpal Khalsa <solarworks at gmail.com> wrote:

From: Kirpal Khalsa <solarworks at gmail.com>
Subject: [RE-wrenches] Grundfos SQ FLEX AC/DC auto switching
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Thursday, May 20, 2010, 2:28 PM

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 automatically switches back to DC.  What I am looking for is when the DC source (solar) is not available it automatically switches over to AC power (grid) ( the reverse of what the IO 101 switch does)  and when the DC becomes available again it again automatically switches back to the DC power (solar). 
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.
Thanks in advance for any advice.!-- 

Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems
www.oregonsolarworks.com

541-218-0201 m
541-592-3958 o