Hello I have done many drain back systems with very little failure. I usually think it is in the subtleties in the piping/pumping loop when a freeze occurs. So if you are to drain back, use only water.
I have done many antifreeze systems with ethylene glycol and have had corrosion in the piping if the antifreeze is not changed. I have had systems run for more than 10 years before the system has a corrosion leak. I have never done a antifreeze drain back system. However they seem to be more popular as time goes on. This is of course a sealed drain back with anti-freeze instead of water. Then if your piping or pumping loop has design problems you will not freeze. It would sure be possible to use nitrogen or argon as a cover gas to prevent oxidation of the anti-freeze and acidic corrosion of the piping/collectors. Darryl --- On Thu, 4/23/09, Troy Harvey <tahar...@heliocentric.org> wrote: > From: Troy Harvey <tahar...@heliocentric.org> > Subject: Re: [RE-wrenches] Heat dump or Stagnate? > To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> > Date: Thursday, April 23, 2009, 1:10 PM > Apparently this is the "modern" design method used > in many european systems. It scares me too. But from several > sources, this seems to be considered one of the most > reliable design methods for closed loop systems (ie. it > works even without electronic controls working, power > outages, etc). > > Standard glycol. The main point seems to be the design of > the pipes and collectors need to facilitate collector > draining from the steam pushing the fluid back into the > expansion tank, so the collectors empty themselves. Its > closed loop, but effectively becomes a "pressurized > drainback" in over heating conditions. > > Here is a couple of links: > http://www.aee-intec.at/0uploads/dateien48.pdf > http://www.suterconsulting.com/CISBAT.pdf > > I'm hoping to find someone with experience with this > kind of system to overcome my fears > > Troy Harvey > --------------------- > Heliocentric > 801-453-9434 > tahar...@heliocentric.org > > > On Apr 23, 2009, at 11:04 AM, Dana wrote: > > > I have only seen boiled glycol turn to a cola like > syrup that had to be > > purged and removed. > > > > What kind of system & glycol is this? > > Where would you expand that much? > > > > Can you provide a link to this paper? > > > > We use heat dumps. > > > > > > > > > > Dana Orzel > > > > Great Solar Works, Inc > > www.solarwork.com > > E - d...@solarwork.com > > V - 970.626.5253 > > F - 970.626.4140 > > C - 970.209.4076 > > "I'd put my money on solar energy. I hope we > don't have to wait 'til oil and > > coal run out before we tackle that." > > -Thomas Edison, in conversation with Henry Ford and > Harvey Firestone, March > > 1931 > > > > -----Original Message----- > > From: re-wrenches-boun...@lists.re-wrenches.org > > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On > Behalf Of Troy Harvey > > Sent: Thursday, April 23, 2009 10:43 AM > > To: RE-wrenches > > Subject: [RE-wrenches] Solar Combi-systems: Heat dump > or Stagnate? > > > > I'm wondering how many of you out there have > installed medium sized > > solar hot water systems (6-8 panel) that were designed > to stagnate > > during summertime over production as opposed to > diverting to a heat > > dump or radiator? The International solar agency has a > couple of > > papers that show a properly designed system should be > able to stagnate > > in a way that the boiling glycol mix vapors in the > panels, purge the > > panels of fluid, turning off the system without > degrading the glycol. > > > > That doesn't seem to be a typical way to design > systems in the U.S. , > > we've usually gone to a heat dump. Does anyone > have experience with > > this? > > > > > > Troy Harvey > > --------------------- > > Heliocentric > > 801-453-9434 > > tahar...@heliocentric.org > > > > _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
