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Thread: Capacity Loss

  1. #14
    Join Date
    Dec 2003
    Location
    Location!, Location!
    Posts
    929
    I've used longer .050 caps- up to 30' on cascades. I wonder if the unit isn't going into a sort of pump-down. What are your equalization times like? Have you tried adjusting the charge or derating(blocking ) condenser temporarily to see if suction pressure increase will change anything? Maybe add 1/2 to 1 oz? Which poe is it, 32,68,100? Who is manufacturer of comp? Is the compressor part of an OEM condensing unit or added to the prototype as separate compnent?

    here is a site with some specs for POE- really only one has flow point below -40

    http://www.gas-servei.com/en/content/products/lubdb.htm

  2. #15
    Join Date
    Nov 2004
    Posts
    18
    Thanks to all of you for your advices on this issue. It looks that freezer is running properly now. After changing high pressure gauge and re-starting, there was some minor capacity loss during first hour or two of pulldown and cycles. The cycles are consistent now, compressor cycles off at -20F, with 2 cycles/hr at 85F ambient. Pressure equalization time is around 4-5 minutes. The small leak on high pressure gauge seems to be the reason for capacity loss. This freezer is intentended for ice cream merchandising.
    The compressor manufacturer is Embraco. The compressor is rated for -40F minimum SST at 100F condensign temperature. I am not sure which PEO they use to charge this hermetic compressor. We are not changing the oil. The compressor is not part of the OEM condensing unit. My experience with cap tubes has been that large diameter and longer length give more stable operation compared to smaller diameter and shorter length. I have seen freezers and coolers with cap tubes longer than 16ft, and they have worked for many years.

    Thanks again.

  3. #16

    Talking

    Have you tried using an expansion valve in stead of a cap tube on this unit? That's probably the direction I'd recommend. I'm also a little curious to know what discharge temperature your running when the unit is near temp.

  4. #17
    Join Date
    Nov 2004
    Posts
    18
    I have not tried an expansion valve because bottom condensing unit is designed to slide in/out for easy service. Suction line is helic coil type to allow this movement. An expansion valve would require another similar coil, and there is no space for another coil. Freezer cost is additional reason to stay with cap tube. When cabinet reaches -20F (the temeprature of air entering evaporator), the evaporator air discharge temperature is around -26F.

  5. #18
    Join Date
    Dec 2004
    Location
    Richmond VA
    Posts
    1
    Basic stuff 1st: If this is a test set-up what type of insulation are you using? might be a problem with condensation. Also is the room temp controled.

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