[RE-wrenches] Heat dump or Stagnate?

Fri Apr 24 11:46:58 PDT 2009

Hi Troy -

We've installed a good deal of Schuco systems with Slim V collectors which
are supposed to utilize steam back. Being a mechanical engineer, I still
have my doubts about the steam back principle but I don't have any real
world data proving it does or doesn't work. I can't say anything bad about
it, however.

Our installed systems are all relatively new so it is hard to say how
they'll hold up in the long term. Our first Schuco systems were installed in
2006. We routinely check the glycol ph and haven't found it going acidic yet
although I've noticed the color (Schuco's glycol is pink) is turning a bit
brown. We've also revamped a large system where we disassembled the copper
piping and found quite a bit of dark pink sediment in the rooftop pipes.

The bottom line is that the more times the system overheats the faster the
glycol inhibitor is going to degrade in any system. Since all these systems
are so new it is hard to say how long this will take. The danger I see is
that it is easy to forget older systems and before you know it they start
failing. 

On another note, Heliodyne is also packaging closed loop glycol systems and
they aren't touting the steam back principle. Their system operates at
higher pressures and use Dowfrost HD. Dow's website indicates that HD is
good up to 325 deg F which is cooking - I doubt flat plate collector
stagnation temps will reach that high at least in our area. See spec sheet
here:

http://www.dow.com/PublishedLiterature/dh_0040/0901b80380040bd2.pdf?filepath
=heattrans/pdfs/noreg/180-01315.pdf&fromPage=GetDoc

I guess I better get back to work... Anyone else have experience with
degrading systems?

Best, 

August

August Goers

Luminalt Energy Corporation
O:  415.564.7652
M:  415.559.1525
F:   650.244.9167
www.luminalt.com
august at luminalt.com

-----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 11:10 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Heat dump or Stagnate?

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
>
>
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