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  1. #1
    Join Date
    Feb 2012
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    Kansas
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    9

    glycol in chilled water system

    Wondering if there is a rule of thumb on how much a system is derated when glycol is added to a system. Example per say 300 ton chiller with 30% glycol you actually get 225 tons due to the heat transfer characteristics of the glycol.

    thanks

  2. #2
    Join Date
    Jun 2006
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    New Jersey
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    4,337
    Quote Originally Posted by pipefittermarks View Post
    Wondering if there is a rule of thumb on how much a system is derated when glycol is added to a system. Example per say 300 ton chiller with 30% glycol you actually get 225 tons due to the heat transfer characteristics of the glycol.

    thanks
    I don't know of any rule of thumb. But most manufactures have charts showing the capacity vs glycol %.

  3. #3
    Join Date
    Mar 2004
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    ottawa canada
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    Depends if its Ethylene or Propylene
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
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    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
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  4. #4
    Join Date
    Aug 2011
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    Chicago
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    51
    My experience any thing over 20% is a problem if it was designed for straight water. Approach temperatures increase to where chiller will drop out on refrig temp or pressure while chilled set point not made. Real problem on small DX systems because less engineering seems to be involved. Larger Centrifugal installs chiller more likely to be designed for anti freeze mix

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    Quote Originally Posted by Jimmyhat 597 View Post
    My experience any thing over 20% is a problem if it was designed for straight water. Approach temperatures increase to where chiller will drop out on refrig temp or pressure while chilled set point not made. Real problem on small DX systems because less engineering seems to be involved. Larger Centrifugal installs chiller more likely to be designed for anti freeze mix
    That's a good point. A system designed for use with glycol might have a larger or different evaporator configuration. Larger chillers always get designed as a custom package.

  6. #6
    Join Date
    Dec 2010
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    Down by the river
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    the buiding coils need to be sized for glycol as well. You loose capacity all the way around as well as pump performance.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  7. #7
    Join Date
    Feb 2007
    Location
    Helena, Montana
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    2,155
    Quote Originally Posted by Southern Mech View Post
    the buiding coils need to be sized for glycol as well. You loose capacity all the way around as well as pump performance.
    Ah the pumps....
    Don't worry zombies are looking for brains, you're safe...

  8. #8
    Join Date
    Mar 2011
    Posts
    258
    Quote Originally Posted by Healey Nut View Post
    Depends if its Ethylene or Propylene
    How do you tell the difference?

  9. #9
    Join Date
    Dec 2010
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    Down by the river
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    Quote Originally Posted by TheChillerMan View Post
    How do you tell the difference?
    Taste

  10. #10
    Join Date
    Mar 2003
    Posts
    7,326
    depending upon the evaporator design, it can range in the 10-15% area with propylene. This doesnt account for the added horsepower requirement of the pump(s).

  11. #11
    Join Date
    Apr 2004
    Location
    Winnipeg,MB,Canada
    Posts
    93

    Glycol in chillers

    You lose approximately 25% of your heat transfer rate in a 50/50 mix. You're gonna run lower suction pressure, or higher head pressure, equipment needs to be selected for expected fluid concentrations, for proper operation.

  12. #12
    Join Date
    Sep 2008
    Location
    Delaware
    Posts
    243
    Bottom line is looking at the SYSTEM. If you add glycol to a closely sized system that was designed for water if could be trouble. The chiller. coils. pumps and concentration of glycol all need consideration.

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