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Looking for good information about active system

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Posted by Oliver Wendell Douglas on January 15, 2012, 10:13 am
Specifically, for antifreeze system with pump, collectors, storage,
etc. I have done a little
reading, enough to know what I think I want to build as a dyi water
heating system to
supplement our electric water heater . There's so much  info out there
though, that I figured
it was time to ask for some guidance before I spend a lot more time
chasing info down.

We live in a sunny area in the southwest U.S., where it routinely
freezes at night during winter.
I have room outside by the house to build a shed or something for the
storage tanks, and
room some good-sized collectors . I can do, or figure out as I do ,
plumbing , wiring, whatever , but I want to
know wtf I'm doing . I don't necessarily need 'blueprints', because
this will be designed around the way the house and existing water
heater and space are arranged , but I do need details of  basic
designs and components , and the supporting educational material (so I
actually do know wtf ) .

I don't mind buying a book or cd or whatever, as long as it's what I
actually need.
DS (OWD was my TV-series name (^;   )

Posted by v8z on January 15, 2012, 5:45 pm

We own and live in a passive solar home that I designed and had built.
http://www.mildevco.net/house2  . We are planning on installing a
solar-thermal dhw system this spring, so I've been doing a lot of research
recently.  The solar thermal collectors will be located on the long shade
roof attached to the south side, which provide the passive overhangs for the
basement windows.

I installed the internal plumbing and wiring prior to finishing the basement
ceiling in anticipation of putting the system in later.   I had a couple of
local solar contractors quote me systems for comparison, and their labor
figures were more than the equipment.  The equipment they quoted was very
similar to what I had researched and planned, confirming my choices.  My
equipment and material only costs will be approx. $500 and with natural gas
prices at current levels will be 5-6 year payback.  Collectors & pumps are
warranted for 20 years.  Installation comprises doing some simple sweating
of copper pipe & fittings, some low voltage wiring, and the manual labor of
moving and installing the collectors.

In your location you need a closed-loop system circulating food grade
propylene gycol anti-freeze ( non-toxic)  through the collectors and using
either a tank with a built-in heat exchanger, or a brazed plated external
heat-exchanger in a well insulated box adjacent to a tank.  This keeps the
anti-freeze loop separated from the water side.

There are lots of collectors that fit the bill, but only a few tanks with
built-in exchangers.  Your storage tank will have to be within conditioned
space so it can't freeze.  Interesting article here
http://www.solartubs.com/solar-water-tank.html  regarding converting an
electric hot water tank to a storage tank with an external h/e.  This guy
http://www.dudadiesel.com/choose_item.php?id=tank251  has really good prices
on h/e tanks and h/e's.

If you plan on using photovoltaics ( PV ) for running your circulating
pump(s), you'll also want an electronic differential controller - fancy name
for a microprocessor based temperature sensing device that determines when
to turn on the juice to your pump.  It uses a sensor at the collectors to
measure the temperature of the fluid in the collector.  On freezing cold
mornings, the sun can come up and generate enough PV power to run the
pump(s), but hasn't had enough time to heat up the collectors - you don't
want to circulate freezing cold gycol through you system, you want to wait
until it has usable heat in it.  The differential controller handle this.
Laing Ecocirc D5 solar pump is your best bet for pumps
http://shop.solardirect.com/product_info.php?products_id0  and Eagle
controllers are highly rated

There are several other pieces of hardware needed for the loop - an
pressurized expansion tank ( like used with well-water systems only
smaller), an air vent valve to purge the system, various other valves to
fill and service the system, and guages to keep track of temps and

Probably one of the best sites to learn from as a DIY'er is
http://www.solarroofs.com/DIY.html   Lots of pictures, diagrams, descriptions
of equipment packages, and installation manuals.  Spend a few hours hunting
and reading on their site.   Their collectors are not the most efficient
however, and polycarbonate glazing has issues which you can research as

Posted by Oliver Wendell Douglas on January 15, 2012, 8:49 pm

I appreciate the links and info ; just what I wanted as next steps .


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