glycol and drainback systems [RE-wrenches]

[Darryl Thayer]

Hi all
I just tested a glycol system, I used the Cryo tek
test strips.  The system is 4 years old, selective
surface single glazed collectors, The freeze
protection was still good, BUT the reserve alklinity
was marginal, This means soon the fluid will turn
acid.  I had some fluid that had not been in the
system, excess left behind, it tested excellent.  

Inother case I had I tested after ten years and found
the fluid was still in good shape in both freeze
protection and in reserve alkilinity.  This system was
single glazed, painted surface. 
Darryl 

--- "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
wrote:

> I'm obviously not seeing the entire picture.  Why
> even use glycol in a drain
> back system? 
> 
> -----Original Message-----
> From: Bill Loesch, Saint Louis Solar
> [mailto:bill_loesch at compuserve.com] 
> Sent: Thursday, September 22, 2005 4:22 AM
> To: RE-wrenches
> Subject: glycol and drainback systems [RE-wrenches]
> Fellow RE-wrenches,
> 
> Tom Lane asked me to forward these comments about
> drainback hot water
> systems.
> 
> Thanks,
> 
> Bill Loesch, Solar 1 - Saint Louis Solar
>  
> From:	"Tom Lane", INTERNET:tom at ecs-solar.com
> 	
> Date:	9/21/2005 10:18 AM
> 
> RE:	glycol and drainback systems
> 
>  
> The lack of information about drainback systems is
> common. The use of glycol
> 
> with drainback systems has been common for 25 years.
>  First, a tilt of 23 
> degrees or more results in almost all fluid draining
> back in the reservoir. 
> Second, at zero pressure a 50% solution of
> water/glycol starts vaporizing at
> 
> 130 degrees F.-a 40% solution of water/glycol starts
> vaporizing at 120 
> degrees F. The vaporizing of any fluid in the
> collectors well below 160 
> degrees F. results in a fluid film vaporizing out of
> the collector into the 
> reservoir. Glycol/water completely boils at 216
> degrees. (-30% glycol 
> solution) to 222 degrees F.(50% glycol solution).  I
> have examined (during
> reroofing) 20 to 25 year 
> old thermal collectors which were using a
> glycol/water mixture and the 
> absorber headers all looked brand new. All
> pressurized anti-freeze systems 
> that old when examined revealed erosion of the
> copper walls.  
> Brandon Levett at Solar Service Inc., has been
> installing commercial and
> residential
>  drainback systems in the Chicago area since 1977.
> Their
> website,www.solarserviceinc.com 
> provides photographs of large commercial drainback
> systems that have been
> glycol drainback
> 50% solution for over 25 years.
> 


		
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