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Scott Davis

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Reply with quote  #1 
My pex collector was working well, but it had a high flow resistance, so I decided to experiment with CPVC in a parallel configuration. 

Conventional copper / aluminum collectors usually put the risers six inches apart.  Since CPVC doesn't conduct heat as well as copper, but since CPVC is cheap and really easy to work with, I decided to put the risers only 3 inches apart to provide a better thermal connection.  It turns out that this design works really well - almost as well as copper / aluminum collectors, is easy and requires no soldering at all! 

Just be careful to build at a high tilt angle (better for winter space heating anyway) because at lower tilt angles, if your pump ever stops while the sun is shining, your collector could reach over 220F and your CPVC may melt!

Here is a video detailing the project:



The CPVC design is definitely outperforming the pex design, probably because the risers are so much closer together.  Gary did a side by side test on the performance of the CPVC with 2" spacing to copper and it turns out they were almost equal!

http://www.builditsolar.com/Projects/WaterHeating/CPVCCollector/CPVCCollectorTest.htm

Have you built a CPVC solar collector? Please reply and tell us about it here! Please be sure to include pictures if you can!

Do you have questions about the CPVC solar collector? Please reply, this is the place to ask about it! We will do our best to help!


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Adriano

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Reply with quote  #2 
Hello there,
I live in Delft (Holland) and in Gubbio (Italy) and I've seen the videos of Scott Davis. I'm interested in that system and I like to hear from you about the Construction and Parts of that beautifull system.
Thanks in advance.
Ciao
Adriano
Scott Davis

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Reply with quote  #3 
Hi Adriano,

I moved your post to the CPVC Collector thread.  I list all the parts I used in the video above. 

Take care,
Scott

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MitchInNC

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Reply with quote  #4 
Hi Scott, Could you add another pump to increase water flow? Mitch in NC
tsodak

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Reply with quote  #5 
I am gathering materials to build a large collector on this design. I am definately concerned about the stagnation overtemp risk, but I think I have come up with a plan for the mount to make the tilt easy to adjust from a winter tilt to a summer vertical with a overhanging shade.

Anyway, I have been thinking a lot about riser spacing and orientation. Since I presently have glass on hand for a 6 footX36 foot collector, that is my present plan. It will be ground mounted and the feed pipes will be ground installed just like Scotts. I do not believe I will be able to get a drainback set up, although I will be looking at the options. I also like the idea of having fluid in the collector at all times in the event of a stagnation so I would guess I will be utilizing a glycol solution and heat exchanger. I am going to look at inground tank options that would facilitate the drainback.

My real question at this point is riser layout for a large array of this design. I think I would have to have a three tier riser with valves to get balanced flow across the riser. By which I mean a main header feeding a secondary riser to feed a series of possibly 4 6X9 foot riser assemblies.

Or alternatly, has anyone done a layout with a single center riser??? Imagnine a series of individual t's stacked with one going each direction to allow an outlet leaving the central column. Send an individual line to the end of the array put two 90*elbows on and bring it back to the center of the panels, to an outlet riser identical to the source riser placed directly over the top of the source riser but offset to accept the return.  This allows a low resistance flow as the individual channels are short.

Final thought would be again to go horizontal, but simply go from one end of the panel all the way to the other and back again. This doubles the length of the iindividual flow path, but maybe 72 feet would not be a problem. Thoughts???

I like the idea of the paralel tubes two inches apart as it balances the total heat loading of the collector. In other words, I could take in all the cold water on one end and exit all hot on the other, but the discharge end is going to run much hotter and I worry about possible warm weather overtemps.

Any thoughts from folsk who have done something similiar???
Scott Davis

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Reply with quote  #6 
Hi Tsodak,

For a 6 foot high, 36 foot wide panel, I would definitely go with hizers (horizontal risers).  It requires less Ts and your "risers" are much shorter, so you can expect more even flow.  Just feed at the lower left and exit at the upper right (or vice versa).  I would tilt the hizers very slightly upwards towards the exit side so that they are all sure to fill and air is easier to purge.

Your plan for mitigation summer stagnation sounds good and will definitely be needed with glass.  I just used Suntuf here.  You might want to design in a few vent holes (maybe 4" PVC that you can cap during the winter and open during the summer for additional security.

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farmerj11

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Reply with quote  #7 
Has anyone ever tried putting cpvc on both sides of the aluminum? I know the backside doesnt get as hot but it could preheat the water before it goes through the front. Also I would think it would make it more efficient. Any thoughts anyone?

Jake
Scott Davis

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Reply with quote  #8 
That's a really interesting idea Jake!  I'm not aware of anyone that has given that a try.  On the plus side, there is more thermal contact, so it should harvest more heat.  The minus is more thermal mass inside the collector, which could increase loses before the heat is harvested.  The only way to know for sure is a side by side test.
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kcl1s

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Reply with quote  #9 

I can see no benefit in putting the cpvc behind the aluminum. If you want to use more pipe the cpvc hizers/risers are flexible enough so you could double up, stack and offset the headers to get almost complete coverage by the cpvc alone in front, in direct sunlight. 

Keith

Scott Davis

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Reply with quote  #10 
Hi Keith,

Good thoughts and I agree.  I think that putting the CPVC close enough (maybe a double layer) to eliminate the need for the metal absorber would be a more advantageous approach.

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