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Thread: True prep table

  1. #1
    Join Date
    Mar 2006
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    cincinnati, ohio
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    258

    True prep table

    I've been working on older true prep table. The evaporator keeps freezing up. I've replaced the cap tube with same size and length and dryer. Ive brazed in access fittings on high and low it's a R134a system. The thermostat went bad on it also so I replaced it. Then I've replaced the evaporator fan too. At start my cabinet temp was 80 degrees. My ambient 95 degrees. My suction was 17 degrees and head 250. Any help would be appreciated!
    Knowledge comes with experience

  2. #2
    Join Date
    Jan 2010
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    6,061
    Looks like a restriction with that hi of head pressure. Of course if your condenser is plugged you would get the same result.

  3. #3
    Join Date
    Mar 2006
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    cincinnati, ohio
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    I overcharged it about 4-6oz to get suction up. I'm wondering if I need to shorten length of cap tube to raise suction pressure. It ran good for a week but now froze up again.
    Knowledge comes with experience

  4. #4
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    Jan 2010
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    What's the nameplate charge say ?

  5. #5
    Join Date
    Mar 2006
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    cincinnati, ohio
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    11oz. It's a True TSSU 48-12
    Knowledge comes with experience

  6. #6
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    Jan 2010
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    Pull the charge and weigh in the exact amount. Your overcharged.

  7. #7
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    Mar 2006
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    cincinnati, ohio
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    When I first weighted it in my suction was at 3-4psi. That's why I overcharged. Shouldn't my suction on a refrigerator with 134 be around 25 psi?
    Knowledge comes with experience

  8. #8
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    Jan 2010
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    On a hot pull down it can go low at first.

  9. #9
    Join Date
    Jan 2010
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    6,061
    Quote Originally Posted by nickellhead View Post
    Shouldn't my suction on a refrigerator with 134 be around 25 psi?
    Well at 26 psig your coil would be 30* add a 10* TD and your at 40* air temp.

  10. #10
    Join Date
    Oct 2011
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    Chicagoland Area
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    134a I like seeing 16-19psi on the suction side. Your head is way too high.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

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    Liberalism-Ideas so good they mandate them

  11. #11
    Join Date
    Mar 2006
    Location
    cincinnati, ohio
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    258
    When I weighted it in I let it cool down but suction pressure nor head changed. It stayed at 3-4&160ish. And it took cabinet forever to get down to 38 degrees. I just don't understand how it's freezing up when I have it overcharged? I'm wondering also if maybe new thermostat is acting up. The probe goes into a well inside middle of evaporator. I've always seen the probes clipped on outside of evaporator. Name:  ImageUploadedByTapatalk1346297324.052569.jpg
Views: 423
Size:  34.5 KB here's a pic of the top of the evaporator.
    Knowledge comes with experience

  12. #12
    Join Date
    Jan 2010
    Posts
    6,061
    What was the head pressure when you first weighed it in ? With a cap tube and no receiver the only place the extra refrigerant could go to was the condenser. This would reduce your condensing surface area. And yes the temp. control cap tube belongs in that well. Take a closer look at the condenser coil to be sure it is clean.

  13. #13
    Join Date
    Oct 2011
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    Chicagoland Area
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    Does this unit have pans on top? If so, are they keeping pans in it overnight or just a cover? Need to keep pans in it.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

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