Design problem on a commercial Chiller/Freezer
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  1. #1

    Confused Design problem on a commercial Chiller/Freezer

    Hi,
    i have been called to checked a temperature problem on a freezer, since it cannot come below -11 degC ( designed for -20 degC).
    I checked the installation and noticed that the expansion valve is installed at 6 meter away from the Evaporator inlet, and the bulb clamped at 6 m away from the Evaporator outlet.
    I am wondering how this system had worked for so many years, and how efficient it could be....
    I am facing a big problem to adjust the TEV since its freezing either all the way upwards or downward the 6 m line.
    Anyone has already seen this type of installation ?

  2. #2
    Join Date
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    Southold.calm
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  3. #3
    Join Date
    Jun 2012
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    Tenn
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    My first question would be how "Commercial" is this walk in freezer? I've seen a few "Locally Manufactured" walk ins at several ma/pa convience stores and resturants. There are plenty of times that I go somewhere and someone has made some pretty bad alterations to a system, almost always a walkin. On smaller units it is not that uncommon that someone who worked on the machine prior to me to have shortened a cap tube. I have what I call a "Grooming Fee" on my jobs for such things. It isn't more money per hour. It merely seperates my doing regular repairs from correcting what others may have done wrong.

  4. #4
    Join Date
    Jun 2009
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    DFW, TX
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    639
    Well, are you there to evaluate how efficient the system is? Or are you there to make it get back to -20*C like it has been for years? Stay focused! True, the 6m of pipe between TXV and evaporator is like wasted BTU's. But in reality, if you insulate the pipe, and especially considering if it has worked for years, why try to redesign it? Sure, if you end up having to replace the evaporator or TXV, you can redo it all to your liking. But my opinion is - unless that's the reason it broke, then don't fix it.

  5. #5
    Join Date
    Jun 2012
    Location
    Tenn
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    The bulb being where the OP says could affect the box temp as described. I do respect what you are saying about us not being the design engineers, and we're not in the business to redesign everyone's refrigeration equipment. From the bottom of my heart I agree to a far point. I can't deny that prior alterations and design issues do from time to time cause the trouble that is noted on the trouble call. It is undeniable that there are times that we have to correct problems from those who either installed, designed or previously worked on the equipment.

  6. #6
    Join Date
    Jun 2009
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    DFW, TX
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    639
    Yes, you are correct. Sometimes you CAN'T really diagnose the issue until you correct the "alterations." You just have to make sure that you're not overlooking the real issue because you see all the "hackery"!

    I guess my concern is that the OP's complaint is that he can't adjust TXV without it frosting up the lines... well, freezers will always have frosted lines...that's why we have armaflex pipe insulation. This leads me to question whether he really knows what the problem is? Back to pecmsg's post which is absolutely correct - the OP just didn't give us any information.

    To answer OP's question, no, I have never seen a setup like that. And no it doesn't really sound "right". Good luck!

  7. #7
    Join Date
    Sep 2008
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    Western PA
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    Quote Originally Posted by trippintl0 View Post
    I guess my concern is that the OP's complaint is that he can't adjust TXV without it frosting up the lines... well, freezers will always have frosted lines...that's why we have armaflex pipe insulation.



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