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Scott Davis

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Reply with quote  #21 
Sounds like a great plan Dan!
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SolarInterested

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Reply with quote  #22 
Scott I probably missed this in your video but what diameter of CPVC did you use in your collector? It looks like it was the same for the headers and risers too?
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Scott Davis

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Reply with quote  #23 
Hi SolarInterested,

I used 1/2" CPVC for both the risers and headers.  Flow seems to be fine.


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SolarInterested

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Reply with quote  #24 
Scott thanks.

Mike

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SolarInterested

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Reply with quote  #25 
Quote:
Originally Posted by Scott Davis
The way the CPVC Ts are constructed, it is tough to get the risers much closer than 2" spacing.  So, if you built two risers assemblies, each with 2" spacing and then stacked them, you would essentially have 1" spacing.


There has been further discussion on this in the various member project threads. It looks like the closest riser spacing for 1/2" tees, which are 1 3/4" in length, is 1 3/4" on centers when there is no space between tees. This results in only 1/4" gaps between risers when two are stacked. Keith R explains the math clearly:

If you are on 1.750" centers and deduct .625" outside dia. of pipe you would have 1.125" gap between. If it is double layer staggered you would deduct .625" from 1.125" and have .500" now divide that by 2 and you have .250"
http://simplysolar.supporttopics.com/post/show_single_post?pid=1278603215&postcount=19

So flashing is probably not necessary but possibly silicon caulking to fill the 1/4" gaps might be worthwhile although testing would be needed. 

This CPVC 'Corduroy' collector could be a good performer although as Gary mentions in his tests

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

further testing at different riser spacings is needed to determine the optimum spacing.

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SolarInterested

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Reply with quote  #26 
Quote:
If you are on 1.750" centers and deduct .625" outside dia. of pipe you would have 1.125" gap between. If it is double layer staggered you would deduct .625" from 1.125" and have .500" now divide that by 2 and you have .250"


Some photos to illustrate the math above


Minimum Spacing 1/2" CPVC Tees



1/2" CPVC Pipe Staggered Double Layer Spacing



1/2" CPVC Staggered Double Layer Riser Spacing

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Garage_Hermit

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Reply with quote  #27 
aha ! Thanks for that, SolarInterested

("an image speaks louder than a 1000 words")
(napoleon bonaparte...)
(note use of minuscules...)
============

Otherwise (more importantly...), this makes me wonder about flashing: could it not be "simply" slid between the risers.  So, front risers in front of flashing, and rear risers behind) (with or without copper-wire ballasts).

G_H

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solardan1959

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Reply with quote  #28 
Solar Interested,
   Nice photos, one big concern.  It is very hard to apply silicone caulking after it is set in place with this kind of spacing.  Ideas would be welcome.   With no flashing is the caulking needed?
   Another idea may be small  ^ type bits of flashing that would sit with the point between the risers kind of like this 0^0^0 but the ^ would be lower.  You could then caulk each side where it contacts the pipe.  This would also work nicely with slightly wider spaced pipes and I think would work better than the flat flashing though it is more difficult to do.  I think this would be a neat idea with a single layer, more difficult with the dual layer.
Dan
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Reply with quote  #29 
Dan, I was thinking exactly the same myself !
Add FLAT *caulkless* flashing, it could even be "bowed" or flexed between the tubes; then caulk down the lengths of the pipes once the flashing is in place. Period.

Alternateive to flashing is steel wool, plced over the lower set of tubes before the upper set is applied: that way, the steel wool is trapped between the tubes: no need for caulk.

Alternative to flashing or steel wool: simple aluminium kitchen foil, folded to several thicknesses thick...
Should be a lot cheaper than anything else...  Slightly hand-crumpled might be better...

Or, pinching HandyMan's idea: flattened beer tins or soda cans: at last, one way to get rid of the d***Rn things !).

I also thought of a pseudo-adaptive material: painted CPVC pipe, rolled in iron filings while paint still wet...  Could be messy, but could also obviate need for ... FLASHING !

Back_to_Work

G_H



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SolarInterested

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Reply with quote  #30 
All good questions guys. Here are my random thoughts on caulking at this spacing:

1. From the BIS site caulking conducts heat 10 times better than air. Without flashing caulking between the risers would still effectively make the absorber the entire size of the interior of the collector (similar to a coroplast sheet)

2. Without doing the geometry I think sunlight would only hit the back of the collector through the voids over a limited period of a day. Direct sunlight is the best so for best performance the sunlight should mostly hit the caulking only when it would shine through the gaps and hit the back of the collector. I think this means the caulking should be below the center line of the riser pipes but I have a hard time visualizing this.

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