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

[Mick Abraham]

Good points, Allan & Ray~

I think Rays caveats can be mitigated depending on the wattage of the
solar module relative to what the coil requires. If the 17v solar
module is somewhat oversized it will run closer to its open circuit
voltage which would make it more likely that a 24v relay coil would
pull in.

OR if a 17v module is somewhat undersized it would tend to operate
below the max power voltage point...maybe enough lower to not overheat
a 12v coil.

********************************************************

Side note: I believe AEE Solar had some small modules with
non-standard number of cells (not 36 cells). I think they had
something small wattage but 40 cells, which would match better with a
24v coil...unless the wattage is so great that the module voltage
moves up toward its open circuit voltage.

**********************************************************

Best choice might be to get plenty of silicon then use a "linear
current booster" (Solar Converters being one brand to look at) which
would deliver a more steady voltage to the "load"...in this case the
relay coil.

Jolliness,

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675



On Thu, May 20, 2010 at 3:52 PM, R Ray Walters <ray at solarray.com> wrote:
> 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
> ray at 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
>> <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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