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Thread: Highest S.H.

  1. #1
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    Just curious..(I need ammo), what's the highest superheat on LT 22 rack seen(at comp) without tripping demand cooling.



  2. #2
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    Sep 2001
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    East Stroudsburg, PA
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    I've seen them at 90 degrees or more not tripping the DC switch, OFTEN.

    As far as NEVER tripping them, as far as I know, 50-60 degrees probably would hold for a long time.

    I've also seen a lot of failed DC controls that didn't fail tripped, so it's hard to say at what point you can start frying eggs on the heads....

    Not a good idea to run them over about 30 degrees, though.

  3. #3
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    I have a H.P. rack at 90* now.When it was first started up ,we had the end bells at 35*.Rack ran great. Then the store's refrigeration consultant came through and was whining about the ice on the suction lines.He wanted it all gone. We tried to tell him that ice is a good thing.....well he got his way.Thursday the D.C. started tripping. I found a 4D with a bad plate gasket.

    I told the manager get ready for summer.

  4. #4
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    most of the time in the Philippines
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    Consultant- someone who borrows your watch to tell you the time.

  5. #5
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    Does that DC cycle or does feed all the time. With that head gasket blown I would think it was always on.

    If your DC does not cycle you are gonna have problems with tripping. Your also gonna have problems with that compressor.

    Not to mention the load your sacrificing with all that additional work the DC is causing. Demand cooling is a good thing, but it is not without it's cost. Your comp has to pump that extra gas.
    A Diamond is just a piece of coal, that made good under pressure!

  6. #6
    Join Date
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    Gold Coast of Connecticut
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    DC cycles on the temp of the discharge via that little probe in the head. If turn on when hot then cycles off. I have NEVER seen one continously. Maybe you needs a new DC module or sensor.

  7. #7
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    Nope. They need to put the SH back where it was, and get rid of the frost-fearing consultant.

    90 degrees is a pump killer.

  8. #8
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    I belive that the switch trips on continuous feed. I'll have to look that up, though.

    I can't recall ever seeing one feed all the time/

  9. #9
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    Originally posted by condenseddave
    I belive that the switch trips on continuous feed. I'll have to look that up, though.

    I can't recall ever seeing one feed all the time/
    It does..that's why the DC reset.The head gasket was blown on the sensor head(was reading 255*),the other head was 50-60* cooler. The DC was constantly running then would trip.

    I was taking infa-red readings on the front of the heads,where the discharge gas exits comp.

    Love that I.R.

    By the way it was fixed that day...I just wanted to see how high you have seen them(superheat)

  10. #10

    Oh, that poor motor...

    Don't forget that high SH doesn't just cause high discharge temp, but also might cause the motor to overheat and trip. The Copeland envelope is based on 65F RG. At -25, 90F SH is right on the edge. There is no good reason to run more than 50-60F SH on a low temp rack, and at those temps you will likely see frost...but no liquid. Frost is not the enemy.

  11. #11
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    Yup, don't fear the frost, the frost is your friend.

  12. #12
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    Emerson, do you know what the parameters for a compressor module to open are?

    I have seen compressors with a a 500 ohm difference between thermistors run.

    How much differance can there be, before the module opens.

    I believe the thermistors are rated 500 ohms dead cold, and 20,000 ohms cooking bacon. what is the trip point?

    Thanks in advance
    A Diamond is just a piece of coal, that made good under pressure!

  13. #13
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    From Copeland pdf on Motor protectors



    I highlighted the important part, hope it's legible, that's about as small as I can make the page and still not blow half Don's bandwidth...

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