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Thread: Glycol %

  1. #1
    Join Date
    Jun 2006
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    New Jersey
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    Glycol %

    So I'm getting into more process cooling for medical equipment. Many have been speccing max 30% prop level. On the comfort chillers in my region, we always maintained 25% for burst protection down to 0 degrees. These process chillers run 24/7 year round, so don't I need to worry about freeze protection. To have them protected down to 0 degrees, I need a 36% mix.

    I talked to a couple of the manufactures, and they told me 30% is enough. That gets me down to 10 degrees. Is that enough? I usually not one to argue with manufactures.

  2. #2
    Join Date
    Mar 2004
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    ottawa canada
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    I wouldnt go more than 30% especially with propylene . Its heat transfer capability sucks the more you concentrate the solution . you will have equipment issues with flow and low temp trip issues if you make it too strong a solution . Also Glycol does not freeze it turns to a jello like consistency at the freeze point it doesnt freeze solid like water and expand causing a burst issue . If the systems are running 24/7 then your only worry is an extended power failure as long as theres flow it cant freeze . if their process chillers their probably on emergency power so no problem as long as theres flow .
    If you have air handlers with outside air and glycol in the coils , and there on a BAS system just have the BAS guy programme the pumps to run for 10mins every couple of hours if the ambient temp gets below a certain point just to mix up the solution and move things around .
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
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  3. #3
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    Quote Originally Posted by graham View Post
    I wouldnt go more than 30% especially with propylene . Its heat transfer capability sucks the more you concentrate the solution . you will have equipment issues with flow and low temp trip issues if you make it too strong a solution . Also Glycol does not freeze it turns to a jello like consistency at the freeze point it doesnt freeze solid like water and expand causing a burst issue . If the systems are running 24/7 then your only worry is an extended power failure as long as theres flow it cant freeze . if their process chillers their probably on emergency power so no problem as long as theres flow .
    If you have air handlers with outside air and glycol in the coils , and there on a BAS system just have the BAS guy programme the pumps to run for 10mins every couple of hours if the ambient temp gets below a certain point just to mix up the solution and move things around .
    The only thing I'm worried about is the redundant pumps and lines. They sit dormant(outside) until needed. There is no pump rotation programmed into these units.

    There are no air handlers associated with these units. They are mostly outside chillers that cool electrical, helium, and feed air to medical equipment.

  4. #4
    Join Date
    Mar 2004
    Location
    ottawa canada
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    There is no pump rotation programmed into these units.

    Then change this ??
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  5. #5
    Join Date
    Sep 2011
    Location
    Heartland
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    25
    There are two things to consider when looking at a glycol chart: freeze temp and burst temp. According to Dow chemical, if the system is not in use during the winter, you only need to have enough concentration to protect to the burst temp. (Which changes very little once you go thicker than 25%. If the system is in use, then you are to protect to 5 degrees below the lowest anticipated temp using the freeze temp.
    The problem with this is that it is in direct conflict with a lot of the chiller manufacturers. Many, if not most, recommend no greater than 30ish percent glycol. What it really boils down to is what the machine was engineered for. If you run a stronger concentration than it was designed for, the heat transfer will go to crap and the life expectancy & reliability of the machine will suffer.
    You'll find that as glycol % increases, so does approach temp... drastically. Efficiency suffers too. I did a calculation for a customer last year and found that a 5% increase of glycol caused a 9% increase in power consumption.

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