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Circulators for solar hw

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Posted by rustics on October 27, 2005, 7:49 pm
 
Hi folks. I have inherited some solar hw panels and am setting them up.
Panels are mounted and tank in place, need to run pipe and make the
connections next.  I have been researching pumps for a while. In my
installation I will have 22-23 feet (approx 7m) of static head. This
will be a drainback system, circulating pure water. I was hoping to be
able to configure a PV-driven pump, but I cannot find details of any
proven, affordable installation that will deal with this much head and
provide adequate flow.  I am probably going to end up using a Taco
model 009 pump driven off mains power.  I have found details of several
makes of low-voltage pumps, including March, Hartnell and the "El Sid",
but none of them appear to be up to the task. Multiple pumps in series
may be workable in theory, but probably not very affordable given the
size of PV panel(s) required , plus current booster(s). Have I missed
something? It would be really nice to use PV power for circulating the
water, but it doesn't look practical to do so. I am in NB eastern
Canada.


Posted by Solar Flare on October 27, 2005, 11:49 pm
 
I hope you get a reasonable answer to this. I am designing the same dilemma and
am considering the Taco 009 or 010
I can;t seem to find anybody knowledgable in these pump specs. The published
specs say they won't do it, save the two mentioned ones.

Also, does anybody know if the power draw on these pumps goes down upon
restrictions or lack of head or restrictions?



Posted by Ecnerwal on October 28, 2005, 1:20 am
 

Handy company, also from eastern Canada...

http://www.thermo-dynamics.com/solar_pumps.html

--
Cats, coffee, chocolate...vices to live by

Posted by Gary on October 28, 2005, 1:42 am
 rustics wrote:

These guys appear to offer a high head PV powered pump:
http://www.thermo-dynamics.com/solar_pumps.html

You might also look at the  Dankoff site here:
http://www.conergy.us/Desktopdefault.aspx/tabid-157/224_read-1768/

They appear to have some PV driven pumps with high head capability,
although they don't list DHW as an application they might work?
Dankoff appears to have changed hands?

I remember reading a HomePower article that stated that drainback
systems (which have higher head requirements on startup than a closed
loop system) normally cannot be driven by a PV powered pump.

I also wonder if a differential control (Goldline style) does not do a
better job of deciding when to turn the pump on (based on collector
temperature AND storage tank temperature) than a PV driven pump, which
just turns the pump on when there is enough sun to drive it?

--


Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects









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Posted by Solar Flare on October 28, 2005, 2:16 am
 I tend to agree with your doubt on a PV logic pump. When it is really cold out
ans sunny your solar pump should be running top speed and you may be pumping
warmer water to the collectors to radiate heat into the cold blue sky.

It would seem to me on a very clear cold day we would need to only circulate
slowly from the collectors in order to warm up the return water the most. There
may be a phase lag where we would only be pumping below 0C solution back to the
heat reserve when the sun first shines. Also there may be a nicely warmed
roof/attic area capable of supplying more BTUs after the sun goes behind the
clouds.

Maybe some NiMh batts to may a delay from the bright sunshine. They need to
charge before the pump starts and continue for 20-30 minutes after the sun goes
away.


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