Kirpal, Lots of good suggestions so far here, but here's my take:
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? 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. 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. 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. Brian Teitelbaum AEE Solar From: [email protected] [mailto:[email protected]] On Behalf Of Kirpal Khalsa Sent: Thursday, May 20, 2010 12:28 PM To: RE-wrenches Subject: [RE-wrenches] Grundfos SQ FLEX AC/DC auto switching 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<http://www.oregonsolarworks.com> 541-218-0201 m 541-592-3958 o
_______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
