Specific gravity as glycol mix indicator [RE-wrenches]

[Michael Welch]

Hi Geoff. Check out the download and other links for Dowfrost HD on this web page:
http://www.dow.com/heattrans/prod/glycol/dowfrost.htm

Also, Tom is on this list so he may be able to chime in. You also might try popping an email to Chuck Marken at AAA Solar.

Geoff Greenfield wrote at 08:26 AM 02/13/2007:
 

>A glycol direct thermal customer had some -4F weather, his pressure shot up
>to 40 psi and he had no typical temp differential on his supply and return
>(and the pump was getting really hot).  He couldn't get a hold of me and was
>about to leave town, so he dumped his glycol mix into buckets and turned
>things off.  He couldn't blow air through (he has a low point in
>unconditioned attic space) and concluded that he had frozen pipes.
>
>We used a 50/50 mix of dowfrost HD that should be good for freeze protection
>down to -30.
>
>Does anyone know of a formula or chart where I can calculate the
>%concentration based on specific gravity?  The measured SG of the solution
>is 1.027 (at 66F - I can have the customer remeasure at 60 if need be).  The
>dowfrost literature says 1.053-1.063 at 60F.  Water is 1.  Is this a linear
>thing where I should expect a 50-50 mix to be the average of those two?
>(1.0265-1.0315).
>
>Any guidance/feedback would be great.  I did look in Tom Lane's book and
>read (page 55)that (counter-intuitively) a greater concentration than 50% of
>glycol would have less freeze protection, so I don't just want to tell him
>to add more glycol!
>
>For a brighter energy future,
>
>Geoff Greenfield
>NABCEP Certified PV Installer
>
>"Clean Energy, Expertly Installed"
>
>Third Sun Solar & Wind Power Ltd.
>340 West State Street
>Athens, OH 45701
>www.third-sun.com <http://www.third-sun.com>
>
>(740) 597-3111   ( Fax: 1548)
>
>
>
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------------------------
        
Michael Welch
Sr. Editor
     Home Power magazine
     www.homepower.com


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