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Solar Storage Tank Questions

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Posted by amdx on September 2, 2008, 4:40 pm
 
I have some questions regarding a diy solar water heater setup.
Refering to my picture posted on alt.binaries.schematics.electronic
Subject line "Solar Storage Tank"
it is modeled after the drainback system here,
http://www.azsolarcenter.com/technology/solarh20.html

If you have a better place for pics, please advise and I'll post the pic
there.

Family of four, Florida panhandle, no collectors yet, just planning
and collecting parts.


I want to use my existing electric water heater, to do this I
would use the drain connection as shown in the red oval. I'd
remove the the faucet, install a 4" nipple, a 4 way, then reinstall
the faucet. I'm trying to imitate the input and output that are on the
lower part of the storage tank in the example.

Would this piping method do the proper job?

This is supposed to be a drainback system.

When the pump is off, can the water trickle backwards through the pump
to drain the collector?   (see the green box)

Is it standard to fill a collector from the bottom?

How many feet of pipe should the heat exchanger have?

What diameter?

Regarding the existing water heater,
Is there a standard depth that the fill pipe goes into the tank.
(thinking about that 1/3 from the bottom shown)

                Thanks for you help,
                              Mike



Posted by amdx on September 8, 2008, 11:21 am
 


Anyone have a suggestion regarding better places to get answers to these
type of questions?
 Forums, groups, etc.
           Thanks, Mike



Posted by gary on September 11, 2008, 3:07 pm
 Hi Mike,
I would probably put a comment up if I could see your picture, but was
not able to get to it.
Maybe something like one of the Photobucket type places would be
better so more could see the picture?

Another group that does this subject area is the Yahoo Solarheat
group.

Gary




Posted by amdx on September 12, 2008, 11:56 am
  Hi,
Maybe that's why I got no response, here's a photo bucket picture.

http://i395.photobucket.com/albums/pp37/Qmavam/SolarWaterHeater.jpg
                                            Thanks, Mike


Hi Mike,
I would probably put a comment up if I could see your picture, but was
not able to get to it.
Maybe something like one of the Photobucket type places would be
better so more could see the picture?

Another group that does this subject area is the Yahoo Solarheat
group.

Gary




Posted by gary on September 14, 2008, 2:54 pm
 Hi Mike,

...

I don't see why not.
Have you thought about using the point where the T&P relief valve goes
in?  I believe you can put a T in there as long as the stem of the T&P
still extends down into the tank.
But, be sure to confirm that the T&P can be moved up a little before
you do this -- hot water tank explosions are very destructive.

You have a somewhat unusual drainback system in that the drainback
tank is large and is (I guess) quite a bit of the storage capacity.
This means that you probably need a way to run the pump that transfers
heat from the db tank to the regular hot water tank when the hot water
tank needs heat -- this might be anytime, including non-sun periods.
So, I think you need a 2nd differential controller (or the equivalent)
to take care of this?  Otherwise, if you use a lot of hot water at
night, you will get to a situation where the hot water heater has to
turn on because its water is getting cold, but at the same time you
may have lots of hot water left in the db tank.

You might want to disconnect the lower electric element?


Yes, for all the usual Grundfos and TACO HVAC pumps, or probably any
centrifugal pump.


And, the line that returns water from the top of the collectors must
terminate above the water line of the drain back tank, else the water
won't drain out of the collectors.  The drain back tanks must also be
vented to the atmosphere.



The HP article listed below says 30 ft of half inch copper.


Home Power has a very good series of articles on solar water heating
system -- the one on drainback systems is in Issue 97.   If you do the
digital subscription, I believe you get access to all of them (and the
whole HP archive) -- including a lot of articles over time on homemade
solar water heating systems.

More stuff here:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

Gary





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