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  1. #1
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    Carrier chillers --- Approach temperatures

    I have been searching in Carriers product data books for design approach temperatures for the gt,rb,ra,gx,hx chillers but cannot find anything.

    Do they not publish this info? If you do not know the design approach temperature how do you figure out if your approach temp. is too high due to dirty tubes,scaling etc.?

  2. #2
    Join Date
    Oct 2003
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    tidewater, va
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    Chill,

    Could you get the local Carrier office to provide start up sheets on the machines?


    r404a

  3. #3
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    I thought approaches were pretty standard unless you use anything except fresh water. I know there are exceptions to that.

  4. #4
    Join Date
    Jan 2007
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    Greensboro, NC
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    128

    Approach is listed in start-up Manual

    Quote Originally Posted by licensed to chill View Post
    I have been searching in Carriers product data books for design approach temperatures for the gt,rb,ra,gx,hx chillers but cannot find anything.

    Do they not publish this info? If you do not know the design approach temperature how do you figure out if your approach temp. is too high due to dirty tubes,scaling etc.?
    The start-up manual lists the Delta T as 10 degrees at full load with the listed water flow.
    If your water flow is more or less the Delta T will vary. Find the rated pressure drop for your chiller to verify flow.
    On the 30GB the info is found in Table 7.
    If your entering water temp. is high the EXV will limit the system capacity until the temp. comes down.
    Some of the chillers you listed are DX with the refrigerant in the tubes, and the others are flooded evaporators with the refrigerant around the tubes. The flooded evap's. are the only ones that can have the tubes rodded.
    You need a good chemical company to clean the chilled water circuit on the DX chiller barrels.
    Try Carriers web site for the manual you need.

  5. #5
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    Jul 2005
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    south
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    Manuals, product data sheets, I have all of that, thats not an issue.
    The fact is nothing is in the literature concerning approach temperatures.
    Say for example i have a 120 ton 30hx machine running fully loaded and i have a 6 degree approach temp. on the condenser. Is 6 degrees too high ,too low, normal? Or a 30ra machine with 10 degree approach on the evaporator. High, low, normal? I know you can look at design gpm and delta t on heat exchangers to find machine tonnage, But without a design approach how do you determine how fouled a heat exchanger is and whether or not it needs to be brushed or chemically cleaned?

  6. #6
    Join Date
    Sep 2007
    Location
    Yuma, Arizona
    Posts
    252
    I had a meeting today with a Carrier customer assurance manager about (2) new 30hxc106. I asked him what was the right condenser approach temperature and he will be emailing me the info soon.

    As for the cooler approach I recall reading it in the manual and I believe it was 3degrees. I'll repost when I get the condenser approach.

  7. #7
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    Feb 2003
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    Wichita Ks
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    on HX machines and GX, both have flooded evaps. GT, Ra and so on do not have flooded evaps. Flooded evaps will have lower approaches. Dx evaps will be higher and the machines with glycol will have higher approaches.

  8. #8
    Join Date
    Oct 2003
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    tidewater, va
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    Good discussion here. Freonrick hit the nail on the head with flooded showing lower approaches and glycol running higher than a water machine. Rotary, looking forward to that info. To original poster, a start up sheet may or may not have the information, but if you could get that information, it would make life easier when troubleshooting the chiller.

    r404a

  9. #9
    Join Date
    Jul 2005
    Location
    south
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    The problem is the last start-up sheet i looked at where the machine was run tested at the factory was not at 100% capacity. They listed suction/discharge temps/pressures/exv position bla bla bla but machine was only run at 80% capacity. Your suppose to check approaches at full load right?

    With the internet and access to information these days, why is this so hard to get.

    I'm just trying not to be like most techs and just guessing at a diagnosis.

  10. #10
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    30 RB approach is 5-7 with freshwater.

  11. #11
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    Goodlistner, where did you obtain that number?

  12. #12
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    Jan 2008
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    In some Carrier literature is all I can say.

  13. #13
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    Goodlistener, You have been hanging around Carrier people too long,
    always wanting to keep info top secret.

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