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Re: Pex vs. Copper [vs CPVC]

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  • Wayne
    An interesting thought Peter, Thanks! W.
    Message 1 of 10 , Apr 26 1:24 PM
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      An interesting thought Peter, Thanks!

      W.


      --- In SimplySolar@yahoogroups.com, "Peter J. Thomas" <pj_thomas@...> wrote:
      >
      > On 4/26/2012 3:19 PM, Wayne wrote:
      > >
      > > Hi Scott, Thank you for the details!
      > >
      > > I might also add, the purpose of this initial build is to supply heat
      > > for hot water.
      > > - If I can sustain enough heat in the winter (doubtful), I may
      > > consider hooking up a heat exchanger to my HVAC unites as well.
      > >
      > > I hadn't seen anything about using CPVC (or this vid)...you may just
      > > have me convinced. :-)
      > > - If I were to do this (closed loop):
      > > -- I have space for a 6' x 8' collector.
      > > -- I could space CPVC horizontally 2" on center.
      > > -- Increase performance by bending flashing... (thoughts?)
      > > -- Automatic cooling fan in collector triggered at 210 *F
      > > ---- Fan could run off of same PV power as the circulation pump.
      > >
      >
      > I contemplating my first solar build. Still in the idea/planning
      > stage. One idea I had to deal with stagnation was to install a pair of
      > automotive cooling thermostats. These are the automatic thermostats in
      > the auto's water cooling system that open and close at a preset
      > temperature. They use the expansion of a wax pellet to open and close a
      > valve at a specific temperature. Prices vary but you could could pick
      > them up for about $6 a piece. One placed on top at about 195 degrees F
      > and one on the bottom at 185 degrees F. This setup would require no
      > wiring and would seal watertight in the normal operating temperature.
      >
      > Again, just an idea, I've never tried it.
      >
      > Peter Thomas
      >
      > >
      > > BIG question now...stick with Plex of go with copper in the heat
      > > transfer/storage tank?
      > > How many feet of heat exchanger tube should I plan on using (either
      > > plex or copper).
      > >
      > > If you don't mind double checking my thoughts/ideas, please tell me if
      > > I'm missing something obvious with this part of my planning.
      > >
      > > Thanks again,
      > >
      > > Wayne
      > >
      > > --- In SimplySolar@yahoogroups.com
      > > <mailto:SimplySolar%40yahoogroups.com>, Snkdavis <SNKDavis@> wrote:
      > > >
      > > >
      > > > Hi Wayne,
      > > >
      > > > Great questions! Responses inserted:
      > > >
      > > >
      > > >
      > > > -----Original Message-----
      > > > From: Wayne <wm.changetheworld@>
      > > > To: SimplySolar <SimplySolar@yahoogroups.com
      > > <mailto:SimplySolar%40yahoogroups.com>>
      > > > Sent: Wed, Apr 25, 2012 4:30 pm
      > > > Subject: [SimplySolar] Pex vs. Copper
      > > >
      > > >
      > > >
      > > >
      > > > Preface - I'm in the research phase and getting ready to put
      > > together a build list for a hydro solar collector.
      > > >
      > > > I'm sure you have already answered this question(s) and I'm
      > > overlooking it!
      > > >
      > > > 1. Are you still satisfied with the performance of the Pex tubing
      > > (ie: doesn't copper conduct much better and last longer in high temps?)?
      > > >
      > > > ** The pex collector is still working great after several years, but
      > > I'm even more excited about the CPVC collector. Please see this video
      > > before continuing:
      > > >
      > > > http://www.youtube.com/watch?v=WP8H5IOTwYU
      > > > ** Copper conducts much better, but that is only part of the story.
      > > There is a heat transfer bottle neck resulting from the flowing fluid
      > > that negates much of the otherwise good heat transfer benefits of
      > > copper. With the much lower cost of CPVC, you can have quite a bit
      > > more contact area, for less cost, which in early testing appears to
      > > efficiently offset the copper benefits.
      > > >
      > > > ** Also, Gary just did a test within the past few days showing CPVC
      > > should be okay to 220F for our applications. If you build at a high
      > > tilt angle for the winter sun, that should be sufficient to survive a
      > > stagnation event.
      > > >
      > > > 2. If you were to build another, would you go with Pex or Copper?
      > > > ** CPVC.
      > > >
      > > > 3. Are you still satisfied with your choice of single Horizontal vs.
      > > Vertical collector?
      > > >
      > > > ** The video shows a 8' X 8' with 32 parallel risers. If I retrofit
      > > my 24' X 8' collector, I will run the parallel risers horizontally
      > > (hisers).
      > > >
      > > > 4. If you had it to do all over again, is there anything that you
      > > would change about your design?
      > > > ** Using CPVC will add a lot of contact area and overcome the low
      > > flow resistance of a long single run of serpentine pex.
      > > >
      > > >
      > > > Hope that's not too much...AND Thank You in advance!
      > > > ** Glad to help!
      > > >
      > > > Take care,
      > > > Scott
      > > > MD
      > > >
      > > > Wayne
      > > >
      > >
      > >
      >
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