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  1. #1
    Join Date
    Jan 2012
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    Demand coolling on low temp hussman

    I noticed on a hussman protocol low temp rack , whose subcooller txv was pending replacement that the rack was runnin freakin hot.
    Everyone of the compressors has a demand coolling module but non of them where working.
    The discharge temperature sensors where installed on the discharge line 6 inches from the compressor. And I was at about 218*f at the sensor.
    Did some investigating and found a document saying that the demand coolling will engage from 258*f 3820 ohms and disengage at 237*f 5000ohm
    Alarm lockout at 286*f 2620ohm.
    Room temp 77*f 86000 ohms.
    I confimed all this later with a potential meter.
    Those operating temps seemed high so I called copeland . They said no more than 220 6 inches from compressor. Thats their safe operating envelope. More than 220*f we are putting strain on compressor.
    These scrolls have a little crevice on the top covered by a little plastic cap.
    I stuck a thermocouple and some heat transfer paste and low and behold at the head I was 275*f with 6 inches from the compressor measuring 218.*f . I stuck the Demand cooling modules sensor in there covered my some aluminum tape.
    It maintained 180*f avg.
    I have since noticed on all the hussman low temp racks at all the stores that the same wrong position of that sensor.
    Am I missing something?

  2. #2
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    Whats the model of the scrolls man?

    Sent from my SM-G975U using Tapatalk

  3. #3
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    Thread Starter
    ZF18KVE-TFE-262

  4. #4
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    Thread Starter
    Ive been meaning to call hussmann about it and ask them. Just haven't got around to it.

  5. #5
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    Thread Starter
    Hausmann is gonna get back to me. Ill keep you guys posted.

  6. #6
    Join Date
    Jan 2010
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    Every Discus rack with Demand cooling runs hot that I have ever seen...in fact I am pretty sure that their bulletin regarding it shows a graph with higher discharge temps than you would normally expect.

    Not sure if the scrolls are using the same module though.

    Sent from my SM-G965W using Tapatalk

  7. #7
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    Thread Starter
    The discus racks with the sensors screwed into the heads are maintaining cooler discharge temps than these.. ...
    Correction. If the subcooller is online and feeding cool vapor into the compressor. All is good. If that valve is defective or solenoids on the economizer are closed . With this setup , compressor discharge temps remain high. Demand coolling never engages.

  8. #8
    Join Date
    Jul 2000
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    Guayaquil, EC
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    Copeland AE4-1327 Economized Vapor Injection (EVI) for ZF*KVE and ZF*K5ECompressors:

    https://opi.emersonclimate.com/CPID/...AEB/ae1327.pdf

  9. #9
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    Mar 2015
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    Medford, N.Y.
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    Quote Originally Posted by icemeister View Post
    Copeland AE4-1327 Economized Vapor Injection (EVI) for ZF*KVE and ZF*K5ECompressors:

    https://opi.emersonclimate.com/CPID/...AEB/ae1327.pdf
    Ahhh! You just put a "face" to that Cope AEB that I read awhile back!Tks!

  10. #10
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    Jan 2012
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    Thread Starter
    Yes, This is the document I referenced .

  11. #11
    Join Date
    Jun 2019
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    Austin TX
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    I believe scrolls use a DTC valve, not the demand cooling module you see on a reciprocating compressor.

    Regarding the position of the DTC valve temp sensor, the small hole on the top of the compressor is the correct location. The bulb does not go on the discharge line. Allowable discharge temperatures are higher for scrolls.

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