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R134a

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johnjohn89
johnjohn89 Member Posts: 100
in A-C, Heat Pumps & Refrigeration
Hi everyone one thing I don’t understand for r134a for beer cooler 
Someone set lpc cut in 31 psi (36f)
11 differential ,so cut out 20 psi(22f)
evorparator coil below box temperature about 10 to 15 degree 
If keep box desire temp 36f that means
my coil about 26f or less,
so I dont understand why coil not freezing up since coil only 26f ? 
What is freezing temperature for r134a at sea level?
for ac r410a coil below 32f ( at sea level) ice forming ( because air contain water vapor it’s below the dew point)
but why r134a not forming ice when running below the 32f 
can someone explain please thanks 🙏 

Comments

  • Ironman
    Ironman Member Posts: 7,376
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    Moisture will turn to ice on any evaporator coil that’s below 32*. It doesn’t matter what refrigerant is in the coil, 32* is 32*.

    Why is yours not icing? Assuming that everything is operating correctly in the system, it’s probably because the RH in the box is low enough that it hasn’t reached dew point and that the defrost system is working.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • johnjohn89
    johnjohn89 Member Posts: 100
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    Ironman said:
    Moisture will turn to ice on any evaporator coil that’s below 32*. It doesn’t matter what refrigerant is in the coil, 32* is 32*.

    Why is yours not icing? Assuming that everything is operating correctly in the system, it’s probably because the RH in the box is low enough that it hasn’t reached dew point and that the defrost system is working.
    Yeah! That’s what am I think 
  • mattmia2
    mattmia2 Member Posts: 9,662
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    It may have some sort of defrost control. If it has relatively large and spare fins the fins will stay closer to cabinet temp and it will only ice near the actual refrigerant passages. Frost free refrigerators with freezers have a heater that defrosts the evaporator that is controlled by some combination of a timer and a thermostat.
  • johnjohn89
    johnjohn89 Member Posts: 100
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    mattmia2 said:
    It may have some sort of defrost control. If it has relatively large and spare fins the fins will stay closer to cabinet temp and it will only ice near the actual refrigerant passages. Frost free refrigerators with freezers have a heater that defrosts the evaporator that is controlled by some combination of a timer and a thermostat.
    Oh yeah! Walking cooler med temp!
    Use air defrost ..
  • pecmsg
    pecmsg Member Posts: 4,859
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    johnjohn89 said:
    Hi everyone one thing I don’t understand for r134a for beer cooler 
    Someone set lpc cut in 31 psi (36f)
    11 differential ,so cut out 20 psi(22f)
    evorparator coil below box temperature about 10 to 15 degree 
    If keep box desire temp 36f that means
    my coil about 26f or less,
    so I dont understand why coil not freezing up since coil only 26f ? 
    What is freezing temperature for r134a at sea level?
    for ac r410a coil below 32f ( at sea level) ice forming ( because air contain water vapor it’s below the dew point)
    but why r134a not forming ice when running below the 32f 
    can someone explain please thanks 🙏 
    Is this a Cap Tube or X - Valve system?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,539
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    Although coils can freeze and frost below 32 degrees typically if air is blowing across the coil they will be less likely to freeze at 32. Around 26 is right.

    You could have electric defrost, hot gas defrost or no defrost except for natural "off cycle" defrost which may be enough to keep the coil from icing.

    Many walk in coolers operate at 40 box temp with a 30 degree coil with no defrost. Depends on coil temp, fin spacing on evap coil and how it was designed. Most are designed to run 16-18 hours out of 24 and defrost naturally when on the off cycle

  • pecmsg
    pecmsg Member Posts: 4,859
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    Walk in coolers usually operate with a 15° Delta.
    I have meat walk-ins that operate between 33 and 38°F product, that's an 18°F coil yet they don't freeze.

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