12 volt differential controller [RE-wrenches]

[Darryl Thayer]

Hi Mark
What is the pump and what size and type pump do you
use?  How big is the SDHW, and what type.  I ask just
for myself and other wrenches that normally do just
110 volt AC DHW.  I have a customer that wants both
DHW and PV installed, so I am thinking of doing 2kW PV
and to steal some DC for the SDHW.  
Daryl

--- "Mark Downing, Hurshtown Alt. Power"
<solarman4 at yahoo.com> wrote:
> Yes I've thought of building my own, but not
> designing it.
> I was given a tip that Ivan Labs makes the
> controller I need, and I am for
> the time being going to see about getting one of
> these.
> 
> --- Darryl Thayer <daryl_solar at yahoo.com> wrote:
> > Is not a differencial controller a comparator with
> > hysterisis?  A Schmitt trigger?  That is a simple
> > circuit to build, have you thought of building
> your
> > own? 
> > Daryl
> > 
> > --- "Carl Emerson, Free Power Ltd."
> > <freepower at freepower.co.nz> wrote:
> > > Kurt,
> > > 
> > > I would like to swap to this approach but I
> suspect
> > > that it would take 
> > > some time to optimize the threshold or
> insolation
> > > level that the pump 
> > > comes on at.... or do you not bother.
> > > 
> > > Also the pump will continue to run when the
> water is
> > > fully up to 
> > > temperature unless there is a thermostat control
> as
> > > well.
> > > 
> > > Maybe a combination of the two is needed and
> would
> > > be more efficient.
> > > 
> > > Carl Emerson
> > > Free Power Ltd.
> > > Auckland. NZ
> > > 
> > > sunwise wrote:
> > > 
> > > >Greetings Mark,
> > > >
> > > >I'm not going to be much help regarding the 12
> volt
> > > controller but I
> > > >will mention a trend I see in the industry that
> > > does away with
> > > >differential controllers completely.  Instead
> of
> > > using such a
> > > >controller, a small (20 watt) solar panel is
> wired
> > > directly to a 12 volt
> > > >circulating pump (typically a Hartel HEH10). 
> When
> > > the sun is shinning
> > > >on the flat-plate collectors it is also on the
> pump
> > > panel, etc.  These
> > > >systems work great, especially in off-grid
> homes.
> > > >
> > > >Kurt Nelson
> 
> 
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