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  1. #1
    Join Date
    Nov 2007
    Location
    NC
    Posts
    137

    Open Air Display Cause Issues

    I'm stressing.
    We got a new account with a local meat market. They had a shorted to ground compressor on the initial call for their big display cause. Got a new compressor. Went through the whole process, replaced, worked for a week....shorted out again.
    Turns out the thing was packed with acid....flushed it out on the first go around with new driers etc...but apparently not enough. So we through a new compressor in there...cut the 2 evaps loose, isolate lineset, flush all components in condenser etc. Just clean it up really good. New compressor put in with driers...all is good. Has run great since. Unit is a pump down system...maintains 35 deg box temp, pumps down to around 5 psi and shuts off.
    I just dont want to lose another compressor and since its lasted twice as long this time around I am pretty sure I got it nailed with just cleaning the system up.
    However I checked it today and, although it was working well, the hot gas line off the compressor seemed extra HOT....put a probe on it, running at 225-235 degrees. I always though 225 was max before stuff starts breaking down and burning up, can I sleep easy tonight?
    Since the last compressor it has been working fine. Good system charge. Both valves maintaining around 10-15 superheat...one valve hunts a bit but not enough to cause problems.
    Operating pressures are around 30/230. 2 Condenser fans on seperate cycling controls...kick in at oh around 245 on the first fan annnnd....like 270 on the second? Thats from memory, dont hold me to it.
    Its running 22.

  2. #2
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,551
    Open your TXVs.

    Your superheat is a bit on the high side.

    I'd like to see 6-8 depending on the unit.

    Your suction pressure is low, too.

  3. #3
    Join Date
    Nov 2007
    Location
    NC
    Posts
    137
    What kind of suction pressure should i be seeing. Havent worked much on these types of boxes...
    And what should I be looking for since its low?

  4. #4
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,551
    Well, I tend to look for an 18-20 degree evap on most meat applications.

    Very cold would be down around 14-15.

    You're down near 10 degrees.

    As far as what to look for, get the SH down and see how it's running. You may find the suction pressure goes up.

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,551

  6. #6
    Join Date
    Jun 2012
    Location
    Afghanistan
    Posts
    16
    First of all I'd only cycle one of the fans. Set the control to cycle from 275 - 225. Let the other fan run all the time. If your still wondering if you have acid in the system do an acid test kit. It only takes a minuite.

  7. #7
    Join Date
    Sep 2007
    Location
    NH
    Posts
    1,146
    Quote Originally Posted by Ice Man In The Desert View Post
    First of all I'd only cycle one of the fans. Set the control to cycle from 275 - 225. Let the other fan run all the time. If your still wondering if you have acid in the system do an acid test kit. It only takes a minuite.
    Especialy if the compressor is a air cooled compressor.

  8. #8
    Join Date
    Jun 2012
    Posts
    41
    R-22 runs hot. You should aim for 38 psi on the suction. Is the compressor undersized? Is there a compressor fan kit installed? Is there proper oil level in the system? Is refrigerant line set properly sized? 10-15 SH is probably higher than what the manufacturer calls for. Get Evap model info and research to see what the case spec's call for. One of my accounts has R-22 parallel racks with Tyler cases that call for 6-8F SH on the meat coffins.

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