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stmbtwle

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Reply with quote  #61 
I'm sure the heat exchanger would work, and I like their use of two smaller collectors. It would make installation a lot easier.

While using your existing tank saves money, a larger tank will store more, probably requiring less backup heat and saving in the long run.

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jterp50

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Reply with quote  #62 
Hello.  My name is John T.  I am new to the sight and solar energy.  I have been reading a lot of the post and am about to build my first water solar collector.  I have glass for a ground mount 3'10" X 25" collector.  I was going to try a CPVC collector, but, wanted to make sure, in your opinion what type is best suited. I live in northern Arkansas.  I would like to combine hot water and home heating like Scott has done.  Any input would be helpful.  Like I said I am new to this and open to try anything.  I will be running water apx 100' to house using insulated PEX.

Thanks, this forum is great!!
netttech

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Reply with quote  #63 
Welcome John T!

INSULATE is a KEYWORD.

If you plan on pumping water 100' from the panel to your home......INSULATE EVERY WELL!

CPVC collectors are very easy to build, requires very little tools.

The panel size you mention, will likely need to be bigger for both DHW & heating. If that's the glass you have available, build the panel, experiment to discover what solar can do.

I'm sure someone here has stats to prove that point, but don't be discouraged. Solar can provide your desired goal, but there are some physical properties about solar thermal, we can't deny.

In the solar panel world....bigger is better. [smile]

Wlecome again & keep asking questions...we can likely answer everyone.

Jeff
Central IL
jterp50

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Reply with quote  #64 
Thanks Jeff.  Actually I have quiet a bit of glass.  I just got 30'+ (5 pcs) of 46"X76" double glaze, tempered to add to the job .
I was wondering if the CPVC method was the best way to go.  I had read that some folks were having trouble with it de-forming.

Thanks
John T
netttech

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Reply with quote  #65 
Sorry John,

I must have mis-read the amount of glass you had. No harm done & you have enough to make a nice sized panel. [smile]

To answer your question, yes, but I believe it occurred after stagnation. I don't remember which member had the problem, but it did occur.

I also have CPVC hot water panel. I've had 'some' deforming, but it was my fault.

My CPVC pipes are laid out horizonally. I believe most CPVC pipe layouts are verticle. I chose horizonal because I wanted to utilize serpentiened copper piping I originally used in last years parabolic panel.

As you can see in the picture below, I have some sagging pipe (CPVC) issues. This is due to a 'freeze-up' issue & plus I was 'lazy'.

The panel got real hot (180+) 1 day, when the lines froze (0-5 degrees) between the house & panel. I discovered 'critters' had pull the insulation away from the pipes for their use. I had to cover my panel with big sheets of cardboard until I could thaw out the lines. It got VERY HOT & registered 180+ degrees when I finally got the water to flow again.

The 2nd reason is I decided to NOT secure the pipes on the right side (picture) with straps, like the rest of the panel (lazy). I ran out of the straps I was using & decided that Silicone caulk would work. [frown]

The silicone may have worked if the freeze-up hot panel didn't occured. lol

If I was going to build another CPVC panel, it would be with verticle piping layout. The best part about CPVC is it's easy to cut out those sagged pipes & fix it.

I may end up rebuilding this panel, removing the copper & if I do the piping will be verticle.

Jeff
Central IL
PB241281.JPG 

SolarInterested

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Reply with quote  #66 
BIS has a post about a CPVC thermosyphon solar water heater

http://www.builditsolar.com/Projects/WaterHeating/CostaRicaThermosyphon/CostaRicaThermosyphon.htm

Quote:
While I would normally be reluctant to use CPVC for a glazed collector that gets this much sun Peter has taken steps to protect the collector from overheating and damaging the CPVC. The steps include the fact that the thermosyphoning of the water though the collector insures that there will always be flow through the collector to cool it, and since the system is unpressurized, the temperature will never go above the boiling point of water. Since the thermosyphoning does not rely on pumps or controllers, it should provide nearly failure proof overheat protection. In addition, Peter did not seal the glazing down, so there is some flow of air under the glazing to cool the absorber.

Really a nice simple and effective design for situations where freeze protection is not required, or where the system could be drained during freezes.

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stmbtwle

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Reply with quote  #67 
I'm quite impressed with that thermosiphon unit. Even without thermosiphon, it looks like an easy to build system that should still work in the southern US.

Back to the subject of the CPVC/aluminum units, has anyone tried aluminum foil for the "fins"?  It's soft and easy to shape around the tubes, and should take a minimum of silicone.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
SolarInterested

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Reply with quote  #68 
Quote:
Originally Posted by stmbtwle
... Back to the subject of the CPVC/aluminum units, has anyone tried aluminum foil for the "fins"?  It's soft and easy to shape around the tubes, and should take a minimum of silicone.

I don't think anyone has tried it but it might not work so well. The 'fins' transfer heat via conduction and thinner metal will not conduct heat as well. Flashing is used because it's a good trade off between thickness and it's relatively easily bent/formed to fit to the risers/hisers.

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Both temperature rise and airflow are integral to comparing hot air collectors
stmbtwle

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Reply with quote  #69 
Thanks.  I was wondering about the thickness/conduction issue..
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
GaryBIS

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Reply with quote  #70 
Hi,
There is a calculator that allows you to calculate how well a fin will perform based on its material, fin thicknes, and fin width here: http://www.builditsolar.com/References/Calculators/FinEficCalc/FinEficCalc.htm


If you assume alum foil is about 0.001 inch thick (which I think is about right), the fin efficiency comes out at 53% -- compared to about 95% for an 0.018 inch thick fin.

Gary

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