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  1. #40
    Join Date
    Sep 2007
    Location
    NH
    Posts
    1,110
    Quote Originally Posted by R&J-R View Post
    Maybe someone taught you that Subcooling is what it is? Did you know Subcooling plays a huge roll in capacity. Ontop of that did you know you cannot achieve a solid column of liquid to the metering device without Subcooling? You should change your line to "Why aren't you using Subcooling in refrigeration?". Subcooling = Capacity / Superheat = Efficiency

    You sound like a supermarket installer. You've taken 4° SH and slapped it on every freezer application. Do you know where the job is located? If the walkin is inside or outside of the facility? What the humidity is? If the door has a kill switch. Tuning lower SH = more refrigerant in the Evap = lowering subcooling/capacity = faster frosting = less surface area to transfer heat = impeeding air flow = iced coil = liquid refrigerant reaching the compressor.

    He said he cleared the coil and couldn't go below 22F because of frosting. His suction saturation averages at -6/-5F. Superheat reading averages 9°-10°. It's obviouse that since he's trending at 22F, SH was the right thing to check. Subcooling let's him know if he has refrigerant/capacity. Choking the expansion valve will lower refrigerant metered into the Evap = raising Subcooling/capacity = less frosting at the coil = more surface air to transfer heat = unrestricted air flow through the coil. At 22F he shouldn't be reading a 10° SH. Should be more like 16°-26° SH. Once he reaches set point (which I'm guesstimating is 0F) his SH should be closer to 8°-12°. From there he should tune SH to Evap spec if available. After which he should then charge the system and bring his Subcooling up to 8°-12° if needed.

    If the thought of just lowering SH to 4° is going to do the trick then why not just go all the way with 0°SH? Maybe you can explain how lowering SH and metering in more refrigerant on a coil that ices up at 22F with 10° SH will help?

    Regardless of what he does
    -Lowering SH risks compressor damage.
    -Raising SH risks a higher temperature trend.
    If it was my 4 point of contact on the line, you best believe I'd skip the risk of compressor damage first.
    Don't think "choking the expansion valve" will raise subcooling.... Unless some one removed the receiver.

  2. #41
    Join Date
    Jun 2009
    Location
    DFW, TX
    Posts
    569
    How on earth are multiple people coming up with 25-30# suctions means likely moisture in the system?

    Id be looking at condensate not draining well, doors that don't shut well, employees propping door open, etc. Or like freezer next to a big dishwasher, saw that once, never gets below 15*f, Everytime door opens steam fills box.

    I'm not familiar with saturated panels but it sure makes sense too.

    I all agree that at 22 degree box, 10* superheat would not worry me.

  3. #42
    Join Date
    Sep 2010
    Location
    New England
    Posts
    42

    Moisture

    Isn't any moisture in system going to freeze in expansion valve and restrict flow to evaporator

  4. #43
    Join Date
    Sep 2010
    Location
    New England
    Posts
    42
    Is there a trap on your drainline

  5. #44
    Join Date
    Aug 2002
    Posts
    70
    How old is the time clock, i had a freezer that would freeze up and time clock checked out good. Froze up a couple of times eveything checked out good, finally found time clock would not advance right new clock and no more problem.

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