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Thread: 40-50 degree ambient subcooling

  1. #1
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    40-50 degree ambient subcooling

    So tonight I got a service call for a couple high temp cases. I checked everything out on the rack and it seemed ok however I noticed my sight glass was sitting low but not flashing. My receiver gauge was at 35 percent so naturally I checked pressure drip accords my filter cores. There was no pressure drop but I noticed that when I was hooking up my hoses gas came out instead of liquid like usual. I checked my subcooling and I had 1 -3 degrees varying. My head pressure was 120. Drop leg temp 57. I canít really seem to understand whatís going on but my rack is not set to start holding back pressure untill 100 when the LPA pump is set to come on. I would like some guidance on this one as it is not a usual problem. Any help with would be appreciated. I can answer any questions if you need more information Thankyou.

  2. #2
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    What is a high temp case?
    What refrigerant?
    What is a drop leg?
    What is ambient?
    What is high temp case temp?
    What is piping like?
    What is inside the SGMI? Vapor/liquid? What is in the refrig system where you hooked up the gauges? Vapor? Liquid?
    LPA pump?
    How many comps on this rack? What else is on this rack?
    What is receiver gauge supposed to be showing ,normally?
    What is evap SH? What is comp SH?
    What is comp discharge line temp?

  3. #3
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    What
    What
    What

    Damn Terry............I didn't know you studded?

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  5. #4
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    Quote Originally Posted by TechmanTerry View Post
    What is a high temp case?
    What refrigerant?
    What is a drop leg?
    What is ambient?
    What is high temp case temp?
    What is piping like?
    What is inside the SGMI? Vapor/liquid? What is in the refrig system where you hooked up the gauges? Vapor? Liquid?
    LPA pump?
    How many comps on this rack? What else is on this rack?
    What is receiver gauge supposed to be showing ,normally?
    What is evap SH? What is comp SH?
    What is comp discharge line temp?
    In other words you want a log sheet?

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  7. #5
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    Quote Originally Posted by pecmsg View Post
    What
    What
    What

    Damn Terry............I didn't know you studded?
    LOL, some stuff I know,some stuff I don't know, Some stuff makes me wonder. And some stuff makes me laugh like hell. Tks pecmsg.

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  9. #6
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    Quote Originally Posted by ehsx View Post
    In other words you want a log sheet?
    Well now, maybe that would have been easier to say. And a LOL to you also.

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  11. #7
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    A higher temp case is a term used in supermarket refrigeration for coolers and freezers. Reach ins, walk ins bunkers all tied into a rack.
    An LPA pump is a liquid pump used on racks to pump liquid out to the freezers in low ambient when it allows the pressure to drop down to 100 psi to make up for the loss in pressure drop.
    A drop leg is a term also used for liquid line after leaving condenser but before the filter drier and receiver.


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  13. #8
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    Quote Originally Posted by Jbtone73 View Post
    A higher temp case is a term used in supermarket refrigeration for coolers and freezers. Reach ins, walk ins bunkers all tied into a rack.
    An LPA pump is a liquid pump used on racks to pump liquid out to the freezers in low ambient when it allows the pressure to drop down to 100 psi to make up for the loss in pressure drop.
    A drop leg is a term also used for liquid line after leaving condenser but before the filter drier and receiver.


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    My lack of Supermarket Rack system knowledge shines very brightly. Tks for the info

  14. #9
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    Not a rack guy either....

    What's your normal receiver level for the current ambient? 35% seems low if you're not flooding for head pressure control.

    Were you just having problems with a few cases, or all of them?

    At 57*, it sounds like your drop leg was full, so you should have had a full liquid feed to all your cases.

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  16. #10
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    You are going to get little to no useful help until you tell us what refrigerant this system is using.


    If only a couple cases are warm why are you focusing on the rack? The only reason I would be looking at the rack for 2 cases would be if they were the farthest from the rack than all others.
    Quote Originally Posted by Jbtone73 View Post
    So tonight I got a service call for a couple high temp cases. I checked everything out on the rack and it seemed ok however I noticed my sight glass was sitting low but not flashing. My receiver gauge was at 35 percent so naturally I checked pressure drip accords my filter cores. There was no pressure drop but I noticed that when I was hooking up my hoses gas came out instead of liquid like usual. I checked my subcooling and I had 1 -3 degrees varying. My head pressure was 120. Drop leg temp 57. I canít really seem to understand whatís going on but my rack is not set to start holding back pressure untill 100 when the LPA pump is set to come on. I would like some guidance on this one as it is not a usual problem. Any help with would be appreciated. I can answer any questions if you need more information Thankyou.
    Sent from my SM-G965W using Tapatalk

  17. #11
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    Quote Originally Posted by BALloyd View Post
    You are going to get little to no useful help until you tell us what refrigerant this system is using.


    If only a couple cases are warm why are you focusing on the rack? The only reason I would be looking at the rack for 2 cases would be if they were the farthest from the rack than all others.

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    Imagine being his / her service manager daily!

  18. #12
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    Itís R404a and I said a couple but I meant multiple. Basically I got to the site and saw that my rack was around 65 degrees superheat and really only looked into the rack because of those 3 things. All the cases were slow pull downs out of defrost and that was all on the work order. Typically when I have 4 or more cases temping high and slow pull downs out of defrost I look into the rack before I go into the store to make sure everything checks out. And it didnít so thatís why I came to the forum but some guys just want to ridicule for whatever reason. I can give you everything from that night below.
    Discharge pressure 120
    Drop leg temperature 57
    Suction pressure 14
    Suction line temp 35-40
    Superheat 58-63
    Subcooling 0-3
    4 comps running out of 6 wasnít staging down or up
    No pressure drop across filter drier
    Liquid gas mix in the drop leg (my biggest concern)
    Receiver 35% is normal itís typically what is wanted
    Receiver actual was about that.
    Condenser was running 100 percent no split
    Vfd 40hz
    Liquid sight glass wasnít full but wasnít flashing


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  19. #13
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    What brand rack is this?

    Is this a low temperature rack with all freezer cases or med temp with all coolers? Or is a split rack?

    What control system is on the rack?

    Where did you read the receiver level? Is it mechanical or digital?

    The condenser was not spilt? As in it has no provision for splitting or it was not running in split mode?

    VFD was at 40 percent? VFD for what????

    How many circuits and cases on the rack were warm then if it was more than a couple? 25 percent? 50 percent? 75 percent?

    What happens if you valve off half the circuits?

    What is the receiver level if you pump down the rack?



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  20. #14
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    Quote Originally Posted by Jbtone73 View Post
    so that’s why I came to the forum but some guys just want to ridicule for whatever reason.
    You have to understand that we have people come here regularly that want help, but don't post enough information to even get an idea of what could be going on. then they never return after the initial post.....

    racks are specialized systems, and all are slightly different, so the more info the better.

    Don't let it bother you, if we were all standing in the equipment room together, we'd prolly be busting your balls the same way....you just don't get any of the humor or sarcasm through the keyboard! LOL!

    hang out and participate, we need some more rack guys on here!

  21. #15
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    So I pumped down the rack and it came up to 100 percent and then I opened it back up. It is a low temp rack and I would say about 25percent of the cases were not at setpoint with half of that 25 percent temping high. I have a mechanical receiver gauge that controls a magnetic gauge that your acre on. I checked the magnet and itís working and also there is a digital receiver level that alarms below 15 percent receiver. It is a mechanical arm that has a digital read out either open or closed. So thereís two. And they both were reading ok. I didnít close any of the circuits off. Itís a novar control system and a kysor warren rack.


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  22. #16
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    Vfd is there to maintain a certain drop leg for the condenser. Really to control fan speed as the temperature outside drops. Kind of Like fan cycling except with variable speed instead of on or off.


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  23. #17
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    Iím just asking for help and Pecmsg is making it like I donít have the makings of a varsity athlete. Itís a tremendous blow to my self esteem.


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  24. #18
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    Quote Originally Posted by Jbtone73 View Post
    I’m just asking for help and Pecmsg is making it like I don’t have the makings of a varsity athlete. It’s a tremendous blow to my self esteem.


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    We need Information!!!

    All I know is your working on a Rack system

    Reread Techman Terrys questions and give us some information

    What is a high temp case?
    What refrigerant?
    What is a drop leg?
    What is ambient?
    What is high temp case temp?
    What is piping like?
    What is inside the SGMI? Vapor/liquid? What is in the refrig system where you hooked up the gauges? Vapor? Liquid?
    LPA pump?
    How many comps on this rack? What else is on this rack?
    What is receiver gauge supposed to be showing ,normally?
    What is evap SH? What is comp SH?
    What is comp discharge line temp?

  25. #19
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    Quote Originally Posted by Jbtone73 View Post
    I’m just asking for help and Pecmsg is making it like I don’t have the makings of a varsity athlete. It’s a tremendous blow to my self esteem.


    Sent from my iPhone using Tapatalk
    When I first joined the forum pecmsg bothered me too. But after a while, I realized pecmsg is only trying to be helpful by asking required information and quite honestly it made me grow more and more not only by providing as much information as possible on the next question in the forum but in the field I try to ask myself what they are going to ask and try to get my ducks in the row, etc. just let it roll of the back and move forward! You got this!

    And please please please apply (free by the way) for pro status and become a regular, keep coming back because the pro forums have a treasure trove of knowledge.
    ďHappiness can be found, even in the darkest of times, if one only remembers to turn on the light.Ē
    "Ha! Memory is RAM!"

  26. #20
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    OP take the lead, I filled out what I could for you.

    Quote Originally Posted by pecmsg View Post
    We need Information!!!

    All I know is your working on a Rack system

    Reread Techman Terrys questions and give us some information

    What is a high temp case?
    What refrigerant?
    404A
    What is a drop leg? Liquid Line between the condenser and receiver
    What is ambient?
    What is high temp case temp?
    65
    What is piping like?
    What is inside the SGMI? Vapor/liquid? What is in the refrig system where you hooked up the gauges? Vapor? Liquid?
    LPA pump?
    Liquid Pump for low ambient
    How many comps on this rack? What else is on this rack? 4 running 6 total
    What is receiver gauge supposed to be showing ,normally?
    What is evap SH? What is comp SH? 58-63 WHERE?
    What is comp discharge line temp?
    ďHappiness can be found, even in the darkest of times, if one only remembers to turn on the light.Ē
    "Ha! Memory is RAM!"

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