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  1. #1
    Join Date
    Jun 2006
    Location
    Charlotte, NC area
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    87

    Propylene or ethylene glycol?

    I am looking for pros and cons of using propylene or ethylene glycol in small chilled water systems that may be exposed to freezing conditions during cold weather. My background is design so I am aware of the physical properties of each product, I am looking for input more on the practical (cost, hard to get, etc.) side of things.

    Thanks in advance.

  2. #2
    Join Date
    Mar 2003
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    7,321
    propylene is not considered toxic yet, whereby ethylene is not allowed to go down a drain as it is considered toxic. broke pipe or drain down needs to be considered in any piping system.

  3. #3
    Join Date
    May 2009
    Location
    Bardstown, KY
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    94
    ethylene is considered more "toxic" but has better heat transfer properties.

  4. #4
    Join Date
    Apr 2010
    Location
    Red Deer, Alberta
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    653
    Quote Originally Posted by flange View Post
    propylene is not considered toxic yet, whereby ethylene is not allowed to go down a drain as it is considered toxic. broke pipe or drain down needs to be considered in any piping system.
    Yes, have used 50% propylene (aluminum compatible with inhibitor) in my outside fired boiler system for the last 30 years, replace every 4 or 5 years at a very reasonable price for a five gallon (U.S) pail. I believe the heat transfer properties are about 97% that of water though some posts at http://www.eng-tips.com/viewthread.c...=155955&page=8 may be of help to you...

  5. #5
    Join Date
    Mar 2003
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    7,321
    round here they do testing intermittently of fluids coming into pumping stations and water treatment facilities. If they find something unusual like ethylne glycol, they go looking. This means in any place they can get to. if they find traces, fines are issued. With water getting soo expensive to treat both coming in and going out, it is getting to the point where it isnt worth the little bit of extra heat transfer to get a potential big fine later on. hell, its getting so expensive to treat wastewater, rainwater etc, the city of phila just went after owners of commercial property and raised rates based upon their land and not their consumption, thinking large property owners would have more runoff. So, with this in mind, a small commercial building with three toilets and say ten acres of land, would pay more by a lot than say a fifty story high rise with a jillion toilets. times are a changing when it comes to wastewater.

  6. #6
    Join Date
    Aug 2007
    Posts
    971
    Polypropylene is used where there may be any chance whatsoever of cross contamination with potable.


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  7. #7
    Join Date
    Sep 2007
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    Somewhere in the world.
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    1,595
    Propylene
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  8. #8
    Join Date
    Sep 2010
    Posts
    66
    Propylene is the way to go for safety and liability. Make sure you calculate properly. Glycol is expensive.

  9. #9
    Join Date
    Aug 2007
    Posts
    971
    If you don't have a refractometer buy one one for glycol.


    Expect nothing, yet expect the unexpected.
    Press on Regardless, Endeavor to Persevere.

  10. #10
    Join Date
    Mar 2003
    Posts
    7,321
    We jsut started up a recool system for or's in a hospital, and the engineer wanted to pull a sample of the glycol to send to a lab to determine concentration. When my guy pulled out a refractometer it was like he was some kind of immortal soul. cheap insurance, you can get a nice one from graingers for a buck or so.

  11. #11
    Join Date
    May 2001
    Location
    Western Wa
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    1,820
    Next time you're at the grocery store, look at the labels on pre mixed cake frosting.
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  12. #12
    Join Date
    May 2008
    Location
    Central Pennsylvania
    Posts
    438
    Quote Originally Posted by flange View Post
    We jsut started up a recool system for or's in a hospital, and the engineer wanted to pull a sample of the glycol to send to a lab to determine concentration. When my guy pulled out a refractometer it was like he was some kind of immortal soul. cheap insurance, you can get a nice one from graingers for a buck or so.
    Yep bout $100 from Grainger, I've seen them new for $25 on ebay, but don't know if their worth a crap. Good tool to have in the truck, I check my glycol concentration during fall PM's to help prevent any freezing issues during the winter.

    Propylene is the way to go, yes ethylene has slightly better heat transfer but also has a slightly higher specific gravity, so you need slightly more pump with ethylene.

  13. #13
    Join Date
    Jun 2006
    Location
    Charlotte, NC area
    Posts
    87
    Looks like the consensus is Propylene is the way to go. Thanks for all the great input!

    Chillerguy you obviously know how to deal with us engineering types – give us two properties that offset each other (heat transfer and specific gravity) and while we do a bunch of research and calculating you fill the system with propylene glycol and get it up and running!

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