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

Mick Abraham mick at abrahamsolar.com
Thu May 20 14:37:56 PDT 2010


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
<allan at 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
> Allan at 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 <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
>
>
>
>
>
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