I think you're going to have trouble with the array direct to the relay coil. a 12 v relay may burn long term, as suspected, but the 24 v relay probably won't close reliably at the lower voltage.
R. Walters r...@solarray.com Solar Engineer On May 20, 2010, at 3:37 PM, Mick Abraham wrote: > I believe Allan's suggestion won't work because the utility AC is > <always> present so the system cannot use PV unless there's a grid > blackout on a sunny day. > > Dan's suggestion sounds more likely: a "double pole double throw" DPDT > relay which requires DC for the coil. > > Consider devoting a small 17v PV module to only drive the relay coil > on/off in a sun synchronous manner. Depending on its wattage relative > to the coil requirement, a 17v module may overheat a 12v coil but may > be OK with a 24v coil. Setting up one mini-module just for the control > function reduces the number of elements which otherwise add "fear > uncertainty & doubt" to the equation. > > Jolliness, > > Mick Abraham, Proprietor > www.abrahamsolar.com > > Voice: 970-731-4675 > > > > On Thu, May 20, 2010 at 2:38 PM, Allan Sindelar > <al...@positiveenergysolar.com> wrote: >> Kirpal, >> I did this about 5 years ago, on an array-direct irrigation pump with the >> ability for the client to run a generator when needed. Yes, it's all >> automatic, and no additional relay is needed. When the IO101 senses AC it >> automatically closes a contactor - AC coil, NO is the AC, NC is the PV. >> Simple as that. The wiring diagram is a funky single page diagram that comes >> with the IO101 - but it's accurate. >> >> Allan Sindelar >> al...@positiveenergysolar.com >> NABCEP Certified Photovoltaic Installer >> EE98J Journeyman Electrician >> Positive Energy, Inc. >> 3201 Calle Marie >> Santa Fe, New Mexico 87507 >> 505 424-1112 >> www.positiveenergysolar.com >> >> Exeltech wrote: >> >> 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 <solarwo...@gmail.com> wrote: >> >> From: Kirpal Khalsa <solarwo...@gmail.com> >> Subject: [RE-wrenches] Grundfos SQ FLEX AC/DC auto switching >> To: "RE-wrenches" <re-wrenches@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 >> >> >> >> >> >> _______________________________________________ >> List sponsored by Home Power magazine >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> 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 >> >> >> >> >> _______________________________________________ >> List sponsored by Home Power magazine >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> 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 >> >> >> > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > 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 > > _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org 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
