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Old 11-14-08, 07:38 PM   #11
GaryGary
Apprentice EcoRenovator
 
Join Date: Nov 2008
Location: SW Montana
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Quote:
Originally Posted by Daox View Post
This is the quote from the FAQ.




The thing is, in the design, the PEX is covered with either aluminum sheet or paint. The aluminum for sure is going to block any sunlight from degrading the PEX. The paint may not be the best blocker for sunlight, but its still not in direct light. That, or it could be covered up with something else (more aluminum perhaps).

I'm not saying the design is perfect. But, I do think you could make it totally workable and reliable.
Hi,
Right -- The PEX is all protected from exposure to UV.
The first layer of protection is the SunTuf polycarbonate glazing -- it has a very aggressive UV cut off built into the outer layer. They add this coating to protect the glazing itself, but it also protects the PEX.
The 2nd layer is the aluminum sheet that covers all of the PEX except the bends at the ends of the serpentine runs. The tubing at the bends is protected a couple coats of the same black paint that I paint the absorber with, but you could use a more bombproof protection if you are concerned about it.

On the PEX crimp tool.
I tried to make the thing so as not to require any special tools. Within the collector, there are not joints at all -- its just one continuous run of PEX. To make the connections for the supply and return, I used SharkBite push on fittings. These are really easy to use -- they literally just push on. They are approved for for residential water supply plumbing, even if hidden walls -- so, they should stand up to the almost zero pressure in a drain back system with no problem. The Home Depot in our area sells a good selection of them -- the only down side is that they run about $6 per fitting.
A 2nd small problem is that they don't fit all PEX -- I found that I had to take out the inside bushing in the SharkBite to make them work with the PEX-AL-PEX I was using.

The thing to read very carefully on the PEX collector is the cautions on avoiding high stagnation temperatures. I don't think that it should see temperatures higher than about 230F. I avoid these high temps on mine at stagnation by using a high tilt angle (about 70 degrees) -- this keeps the stagnation temps down in the summer because the sun is so high that the incidence angle is very large. This works out well for me in that it also increases winter collection (when the sun is low), and gets more benefit from reflection off the snow. But, if you can't live with the stagnation temp limitation, the copper alternative (that still uses alum fins) is only a few bucks more, and (as mentioned above) is more efficient. All in all, I think the copper collector is probably better for most people.

The solar heated water storage tank and plastic pipe coil heat exchanger actually end up saving even more money than the cheap collector, and they can be used with (just about) any collector.

Gary

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