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  1. #1
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    Emerson core sense 2 red flashes

    I'VE been a tech for 15 years and only work on commercial refrigeration. We install walk-in coolers and freezers. We installed the one in question about four years ago.
    Got a walk-in freezer with the emerson core sense module. It's on a copeland discuss compressor about 7HP. It has been randomly tripping on two flashes. Motor overheating. It has one evap, outdoor unit, superheat is good. The differential on the low pressure switch was a little narrow and witnessed short cycle once during a pumpdown. Increased the differential but customer says it is still tripping about every 2-3 days. Oil level is good and clean. Has any one had this issue?
    I was considering adding a delay on make on the compressor contactor.
    Last edited by Refer Rick; 03-12-2020 at 09:04 AM. Reason: Spelling errors

  2. #2
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    Look for high head pressure possibly from a faulty condenser fan or dirty condenser coil.
    What's your ambient and head pressure control type ?

  3. #3
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    Thread Starter
    It has a Headmaster. Head pressure is good. Around 190-200. Full sight glass. Clean condenser. Ambient temp. 30-50 degrees.

  4. #4
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    Thread Starter
    Also has an accumulator and normal amp draw.

  5. #5
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    I first started seeing this short-cycling on shutdown about 10 years ago with Copeland scrolls, both low and medium temp. typically it was just one or two quick re-cycles but sometimes I observed up to a dozen re-cycles in rapid succession which would certainly be enough to cause an overheat trip, I never had a unit with Core-sense, but I sure it would have tripped when that happened.

    Heatcraft first suggested adding an external check valve in the compressor discharge line and when that didn't work use a time delay or widen the differential on the LP control.

    From my experience, forget the check valve and LPC differential and just go with the time delay. I set mine at 3 minutes. No more short-cycling.

    Some will say the cause is a defective discharge check valve in the compressor, but in fact it's simply the result of the re-expansion of the compressed gas inside the scrolls which rush back to suction. This slight bump in suction pressure is sufficient to cause the (usually) intermittent short-cycling events.

    Widening the differential on the LPC will work but can lead to problems if it's an outdoor unit subject to very cold conditions.

  6. #6
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    Go with a delay on Break timer.
    3 - 5 Minutes

  7. #7
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    Quote Originally Posted by Refer Rick View Post
    It's on a copeland discuss compressor about 7HP.
    icemeister he stated here it's a Copeland Discus compressor.
    OP what's your condensing unit model number ?
    Also what refrigerant and what was the ambient when you took those pressure readings ?

  8. #8
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    Quote Originally Posted by VTP99 View Post
    icemeister he stated here it's a Copeland Discus compressor.
    Sorry....I had a brief BIden event.

    The time delay would still be the way to go to eliminate the possibility of excessive short-cycling. If the Core Sense still trips at least you've eliminated one potential cause.

    If the TXV is an MOP pressure limiting type (like a ZP) the post-defrost pulldown periods when the TXV is restricting flow could cause suction superheat high enough to result in high motor temps. I always preferred the standard Z charge and a CPR valve. The TXV then can better control superheat during pulldown.

  9. Likes N2fords liked this post.
  10. #9
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    Quote Originally Posted by icemeister View Post
    Sorry....I had a brief BIden event.
    Now that's funny good one icemeister 😂

  11. Likes crazzycajun liked this post.
  12. #10
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    OP,I kinda do not like the description of ''good'' when an actual # is much more accurate and helpful to all. What refrigerant?

  13. #11
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    Heatcraft condensing units use a delay on break LP control on start up.
    On start up the system can pull into a vacuum until things stabilize.

  14. #12
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    Thread Starter
    I thank everyone for there advice. I dont have the model number at the moment. It is 404A. The TXV advice is one thing I haven't considered. I do believe i eliminated superheat being a problem. I'm going to check if all wires are tight also.
    Ambient temp is low. No higher than 50 degrees this time of year. Head pressure is low.
    Its not a scroll so I'm not getting that sudden expansion during shutdown. I had problems with that before with a low pressure peanut. I installed an adjustable pressure switch. I see the new scroll condensers are now coming with backflow preventers on suction lines to stop that problem. We had one installed backwards from the factory.

  15. #13
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    Quote Originally Posted by Refer Rick View Post
    I thank everyone for there advice. I dont have the model number at the moment. It is 404A. The TXV advice is one thing I haven't considered. I do believe i eliminated superheat being a problem. I'm going to check if all wires are tight also.
    Ambient temp is low. No higher than 50 degrees this time of year. Head pressure is low.
    Its not a scroll so I'm not getting that sudden expansion during shutdown. I had problems with that before with a low pressure peanut. I installed an adjustable pressure switch. I see the new scroll condensers are now coming with backflow preventers on suction lines to stop that problem. We had one installed backwards from the factory.
    backflow preventers?

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