[RE-wrenches] Heat dump or Stagnate?

[Darryl Thayer]

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 <taharvey at heliocentric.org> wrote:

> From: Troy Harvey <taharvey at heliocentric.org>
> Subject: Re: [RE-wrenches] Heat dump or Stagnate?
> To: "RE-wrenches" <re-wrenches at 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
> taharvey at 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 - dana at 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-bounces at lists.re-wrenches.org
> > [mailto:re-wrenches-bounces at 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
> > taharvey at heliocentric.org
> > 
> >