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Condenser split

Discussion in 'Refrigeration' started by icy78, Aug 11, 2017 at 2:55 PM.

  1. icy78

    icy78 New Member

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    504
    What's the expected CS on prep tables? freezers? I don't see them much , but had a few this summer since one of our guys quit. The one today was a TUC-48F.
    Had 365/28 when I got there. ended up being the shroud was slid back too far so the fan recirced. And dirty. Pulled charge ,cleaned cond and fan blade, and left dryer in. Someone had put in an 083, I didn't have one. Vac, new charge, 241/11 at 82 ambiant. That's a 20 CS about. So, is that typical? Pressures typical? 404a.

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  2. pecmsg

    pecmsg Junior my ASS

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    Get a frost line at the pump and back it off.
     
  3. crackertech

    crackertech assholiness *

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  4. icy78

    icy78 New Member

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    That's not my question tho. The case is cooling fine now. Just wanted to know if that's typical for those cases.

    Running at 11 SP would be -28f r404. So I would expect to have frost consistently at the comp (with a decent SH.) If I run to frost and back it off, that's over 32f most likely, giving 60 SH.

    Place was too busy and case was at 23f so couldn't check at setpoint.

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  5. R/HVAC

    R/HVAC selfemployed

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    Location:
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    can't answer about the split but I think your cap tube is partially restricted. Cabinet is 23º and SS is -28º so your TD is 51º if I use 23º as the air entering the coil. True tends to run their coils at 20º TD. Call and ask them they are good folks. Just my 2¢
     
    Rather B Riding likes this.
  6. Rather B Riding

    Rather B Riding Behind bars

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    Medium temp and low.tep are way different. 30 over and 20 under will help you a lot. So as a general rule of thumb 30 over ambient is your suggested head pressure. ie. 82° ambient +30°= 245 # head pressure. Medium temp evap is box temp 40° so 20 under boil point =54 #.

    Low temp just adjust the boil point to the evap temp you need but instead of the -20 rule it's more like -10 -15 . You are looking to achieve a -5 to -10 degree box temp you need a -15 to -20 degree boil point.

    365/28 you have a restriction. 241/11 same thing under charged. What is CS?
     
    Fred Meebley and R/HVAC like this.
  7. Fred Meebley

    Fred Meebley New Member

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    Location:
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    Are you saying you remove a little refer, or close the txv a touch, once you see the line freeze up to the compressor?
     
  8. crackertech

    crackertech assholiness *

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    Close the txv a touch, or if it's a cap tube remove a little juice
     
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  9. icy78

    icy78 New Member

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    504
    Thanks. By CS I mean condenser split, (what you posted about the 82 plus 30.) That would be 112f condensing temp then, or 280 HP . I have a 20 split at 240 HP. Actually its LL pressure but close. I weighed in the charge adding for the nonOEM dryer, so I should be close. I know the suction seems too cold but True seems to always run a low suction. I went to one class about 10 years ago. They said their freezers ran 7-12 r404. Pretty low!

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  10. 404eh

    404eh New Member

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    A hot box will have more heat, check running at cold box. Head pressure is just a median of acceptable numbers, your compressor heat is removed in the refrigerant as well.
    As long as they aren't a restricted looking pressure I wouldn't get to into it
     
    coldsnap likes this.
  11. mike1020

    mike1020 entitled millennial

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    There isn't a good standard for the condenser split.

    Some manufacturers will oversize the condenser because they know it will be in a hot environment and nobody will ever clean it.

    Some manufacturers will have a correctly sized condenser.

    And most manufacturers will have a condenser that's too small, to what degree varies between manufacturers.
     
    coldsnap and R/HVAC like this.
  12. icy78

    icy78 New Member

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    504
    I'll go with that. The reason I was using it was I had weighed the charge in, but could not stay until the case cooled due to usage. So I wanted another way to double check. I think I'm undercharged tho because the box was warm so my condenser should be been hotter. I'll see if they let me in to find out. These guys look like "reluctant service callers." Thanks guys.

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  13. pecmsg

    pecmsg Junior my ASS

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    Its difficult to weigh in a few Oz unless you are using @crackertech's charging Cylinder. That's why we get it to temp, frost line to pump and back off. Check the SH at the pump also 20 - 30
     
  14. Rather B Riding

    Rather B Riding Behind bars

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    Yes 112=280 sorry read itwrong. 30 over is just a general rule. If the system has a receiver, which your system probably does, it will only hold true with a clear evap and a full load. As it runs the head will tend to drop off a little. My concern was low suction. I have seen a -28 evap temp just not in most freezers. Some ice cream freezers are designed for a -15 to -20. Just not the norm in the restaurants. Like I said med. Temp and low temp are different. Med. I pay more attention to the pressures than low temp. Still use some of my rule of thumb methods but the bottom line is can it pull it down to set point. Heat transfer. That's all that matters. Sorry never heard CS before. Remote condenser or self contained.
     
  15. coldsnap

    coldsnap -20 on the money

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    I agree with these guys. I don't check temp split on small reefer stuff, just operating pressures. Also, I would be more concerned about liquid line temp than condenser split.
     
    icy78 likes this.
  16. mike1020

    mike1020 entitled millennial

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    Mike the Hack goes off suction pressure on small cap tube systems.
     
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  17. icy78

    icy78 New Member

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    504
    Yes self-contained cap tube system.
    Thanks for all the input guys.
    Just a question pecmsg and cracker. Do you use the frost line method on cap tube low temps too? If so, how do you ensure sufficient suction line superheat? Or has experience shown that the return gas temp is sufficient for compressor cooling?

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  18. pecmsg

    pecmsg Junior my ASS

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    19,862
    Location:
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    SH 20 - 40 at the pump.
     
    icy78 likes this.
  19. crackertech

    crackertech assholiness *

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