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  1. #1
    Join Date
    Jan 2019
    Location
    huntington beach calif
    Posts
    7
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    York ycav 307 # screw compressor low discharge superheat

    Hi guys new to the site here, but not new to the Hvac business, been doing it since 1977, I am a contractor in Southern California, well I got a york ycav that is really twisting my tail, got called out to site and I am told the # 2 compressor is failing on low discharge superheat, I look it over and see feed and drain valves are new and also the liquid level sensor in the flash tank, this chiller is air cooled and about 10 years old, the stepper modules are still original, so I reset it and watched for about 2 hours, r134 refrigerant, chiller set point 42 degrees, had 36 suc 130 discharge at 62 ambient, suction superheat 14.5 discharge super heat 5.4 and fighting to get up to 10 degrees, motor temps T1 68 T2 77 T3 78, 66% speed, economizer valve on,
    Drain valve 75% feed valve 45 %, now the flash tank showed 0 % and bouncing to 5 and back to 0% , oil level on sperarator is just show a little in upper sight glass, but after 15 min of operation the motor temps were in the dumpster avg 66 degrees, failed low discharge super heat around 4 degrees, I did verify the drain and feed valves in service mode are opening and closing, customer assures me that he was there when the charge was weighed in 177lbs, the level sensor and valves were installed 3 weeks ago and customer said it will stay on line for more that 10 mins, if I remember correctly 10 mins is the max time for this Chiller wit low super heat on suction or discharge, the level sensor is the PEEK sensor and you are able to calibrate it,I thought that maybe the refrigerant is oil laden, and also going calibrate the level sensor, the amp draw looked ok, need to get the reading on that, also thought economizer is pulling liquid off of flash tank if the level is high flooding the lobes, can’t dischar above 105 degrees, well got invited Back on Wednesday to do some more digging on this chiller, well sorry to be the new guy here and drop a bomb, but any feed back would be helpful thanks for taking the time to read this book-lol

  2. #2
    Join Date
    Jan 2019
    Location
    huntington beach calif
    Posts
    7
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    Thread Starter
    the suction sensor was reading high by 12 degrees, causing drain vale to flood evaporator, replaced sensor and all good!

  3. #3
    Join Date
    Nov 2011
    Location
    East Side
    Posts
    5,897
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    what did your flash tank level do after the sensor was replaced?

    at 100% load, with 35% level setpoint, correct charge, and a true level in the tank (at or above the glass), I would expect to see the valves in the 30-50% range (depends on conditions).


    get your post count up and apply for PRO membership. we can get very in depth, and share more information in the Locked forums of the board!


    there are some service bulletins about putting new valves on older chillers.

  4. #4
    Join Date
    May 2004
    Location
    Salt Lake City/Tooele
    Posts
    5,154
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    Seems like it always a sensor/transducer on these things. Creeeeeeeepy, just dealt with this exact issue Wednesday. I have gotten to the point whether it is a York, Trane, Carrier, or whatever the hoo-haw packaged chiller I am dealing with, that I first focus on any sensor that is utilized by the unit's brain to assist the proprietary algorithms to fart out a fault/error code. The tight tolerances or envelopes of operation that these manufactures have created to protect their screw compressors that if the readings of a sensor are a few degrees, psi's, inWC, off that it creates a chain reaction that will ultimately lead to faults as you have encountered.
    In a nutshell, first verify proper operation of the sensors/transducers.

    As stated by 71Chops, join the PROS!

  5. #5
    Join Date
    Jan 2019
    Location
    huntington beach calif
    Posts
    7
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    Thread Starter
    Hey chops 71 , yep for sure you need to manually verify all pressure and temperature readings before believeinf what the front end is saying, once I got it back on line the level sensor was reading high, but I did ntshow level on the flash tank, I let everything marinate for about 1 hour and started to see a level change, I was reading like 48 % , with nothing in the sight glass, 23 degrees discharge superheat, 12 on suction, so long story short, I drove the drain valve to 0% and feed to 100% and restarted chiller and got about half sight glass and recalibrated my level, it has the peek level sensors on it, you albe to Cali are them as apposed to the older sensors, went by yesterday to do a recheck and running like a champion-lol, never say that to loud right,
    Monday cvhf 910, low oil diff, hoping for a easy cheesy on that one, hey thanks for sroppontme a line and I will try to increase my posts, later gator 🐊

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