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  1. #1
    Join Date
    Feb 2008
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    Uneven produce temps

    So we had a tech go out on a call for produce sections freezing product. This is a multi deck produce loop on a rack. The cases are fitted with non adjustable expansion valves. The tech recommended that we install stem kits on the valves and adjust superheats. But the service manager recommended installing an EPR because the cases are controlled by pump down right now and he was told by manufactures that non adjustable valves should not be used on pump down systems. Due to poor superheated control.

    Can anyone verify that statement.

  2. #2
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    I have never heard of that either.
    I love the smell of phosgene first thing in the morning:

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  3. #3
    Join Date
    Jul 2000
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    In my experience, pumpdown control is probably the least desirable for temperature control of an open single or multideck case where you're controlling from DA temperature...which I assume is what you have here.

    I don't think the non-adjustable TEVs has anything to do with it.

    Since this run is on a loop, I'd opt for the EPR with a suction stop as a low limit.

  4. #4
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    Jul 2009
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    Quote Originally Posted by crackertech View Post
    I have never heard of that either.
    News to me! Is this something new?

  5. #5
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    Yeah, I went to the store and found an orit-6 in the case. Set it up for 25SST and get 33 DA across all cases. I agree pump down is poor control. It's just sometimes the service manager is a smart fella.... Then he says things like this. Lol.

  6. #6
    Join Date
    Feb 2008
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    SW MO
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    I'm with icemeister, I don't think poor temperature control has anything to do with the non-adjustables. but if the tstat is cycling frequently, I can see it affecting superheat control, adjustable or not.

    evaporator/equalizer pressure is a closing force on the tev.

  7. #7
    Join Date
    Apr 2010
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    Richmond, Virginia
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    Back when I was doing wallyworld star-ups all the hussmann cases had nonadjustable expansion valves. Before walmart would sign off on the store all case temps. had to be within specs wich ment ------ Novar looks at case B setpoint.case A has to be within 2* of B and case C has tobe within 2* of B. On the hussmann cases the only way to achieve this was to move the txv bulb. Temp. control is stickly done by energizing and denergizing the SORIT. Walmart wants 100% run time on all the SORITS (no cyclng) the superheat at the valves will not be effected on neither the nonadjustable or the adjustable!

  8. #8
    Join Date
    Jun 2001
    Location
    Michigan
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    12,077
    Pump down on any line up sucks. I use to be told, "it's cheaper that way". No. It means you produce more service calls and that creates income.

    There is no fricken reason for it but just poor practices.

    I have seen new jobs go in with pump down on fresh meat and just shake my head.
    People who think they know everything are a great annoyance to those of us who do.

  9. #9
    Join Date
    Jun 2001
    Location
    Michigan
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    Quote Originally Posted by NANOTECH View Post
    Back when I was doing wallyworld star-ups all the hussmann cases had nonadjustable expansion valves. Before walmart would sign off on the store all case temps. had to be within specs wich ment ------ Novar looks at case B setpoint.case A has to be within 2* of B and case C has tobe within 2* of B. On the hussmann cases the only way to achieve this was to move the txv bulb. Temp. control is stickly done by energizing and denergizing the SORIT. Walmart wants 100% run time on all the SORITS (no cyclng) the superheat at the valves will not be effected on neither the nonadjustable or the adjustable!
    But I will tell you what. When a Walmart store is finished with commissioning, it runs and runs well and there is very little problems. I have been a part of a few of them and I would get bent out of shape trying to tweak them. But once it's dialed in, them racks purr like kittens.
    People who think they know everything are a great annoyance to those of us who do.

  10. #10
    Join Date
    Feb 2008
    Location
    SW MO
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    Where did you move the TEv bulb?

    and are you saying the valves hunted with the bulb mounted in its standard position? which affected the case temps?

  11. #11
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    Quote Originally Posted by stonewall View Post
    Where did you move the TEv bulb?

    and are you saying the valves hunted with the bulb mounted in its standard position? which affected the case temps?

    Do tell.
    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


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  12. #12
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
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    304
    Example: 36' Dairy -- (Hussmann) Temp. sepoint 36* case A 33* case B 36* case C 39* To bring case A up to within 2* of B you would have to move the bulb out from the evap. coil! To bring case C down to within 2* of B you would move the bulb closer to the evap. Prior to doing this you would see on the graph where the SORIT has been cycling after, the graph will show a staight line (100%) run time! ---- NO PUMP DOWN. After beeing tweaked I have checked the superheat on each case and have them very as much as 4 degrees but wamart is more concerned with the 2* strategy rather than the superheat!

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