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  1. #14
    Join Date
    Jul 2009
    Posts
    4
    Thats a good thought, thanks, it is the only CRAC against a wall.

  2. #15
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790
    Setpoints and sensitivity?

    How far into your conditioned space is the unit's T/H sensor?
    It's great to be alive and pumping oxygen!

  3. #16
    Join Date
    Mar 2005
    Posts
    53
    Hey hutch if your tech was qualified you would not be here seeking information he would. If not here then with Leibert tech support. Like I said Qualified is the key here

  4. #17
    Join Date
    May 2006
    Location
    Western NY
    Posts
    4,356
    You have to know the password to change settings. That is for good reason too.
    "Excellence is the gradual result of always striving to do better"
    -Pat Riley

  5. #18
    Join Date
    Jun 2008
    Location
    Apopka, Florida
    Posts
    110
    Hutch,
    You had indicated that there are other units in the space;

    The units are about 10 yrs old, in a Data Center. The temp settings are set close to maintain a steady temp... and the other lieberts, 2 other crac and 3 ACU units are all set at the same settings and I don't have this problem with the others.

    Questions for you and your tech:

    1) Are the other ACU's, Data Center units that are able to control humidity or just straight cooling?

    2)Is there any outside air coming into the Data Center?
    Data Center units work with 0% outside air and must have a proper vapor barrier for the consistent control of the room.

    3)Has your Load changed or have been lighten to cause the short cycling to occur?
    Total Load tonnage(kw) vs. Total Cooling Capacity (kw)

    Keep us posted,

    Domcort

  6. #19
    Join Date
    Apr 2006
    Location
    Michigan
    Posts
    110
    Quote Originally Posted by schomaker9253 View Post
    Hey hutch if your tech was qualified you would not be here seeking information he would. If not here then with Leibert tech support. Like I said Qualified is the key here
    That is a very important distinction between those of us who care and those who don't. There are days I wish I was capable of leaving the job at work but thats not what makes us who we are. Like so many others here I've lost track of my time spent researching problems on my own time.

  7. #20
    Join Date
    Nov 2003
    Location
    Rochester, New York
    Posts
    392
    Hot gas bypass? Elec rh? HWRH? All will help with cycle if there working.

  8. #21
    Join Date
    Sep 2011
    Location
    Dallas Texas
    Posts
    1
    The new Crac units have a setting in the Service Menu that allows you to use PI, Proporational or Intelligent. I found that Intlligent setting will cause the unit to overshoot at times but will not allow a short cycle.
    The last proporational band I changed had 10,000 starts and a total of 71 hrs of work. Very hard on the unit causing a PDF problem.

  9. #22
    Join Date
    May 2011
    Location
    Fort Worth, Texas
    Posts
    49
    I've run across this a couple times on Liebert units.

    There's a good chance your LLSV is leaking-by causing the unloader to pump the compressor down. The problem is after 5 restarts within an hour, it actuates the short-cycle alarm. You can test this by gauging-up to your suction service valve and monitoring the psi's. If the psi starts to rise after the unloader has pumped the compressor-down to the LPCO more than once (sometimes there's enough gas to raise it causing one more pump down), then your LLSV is leaking-by.

    If that is your problem you will probably need to replace the LLSV unless you just want to disable that alarm. You can disable the alarm by going into the alarm menu on the control panel. If you don't know the password, you can disable the password protection by turning microswitch #6 to the off position.

    Last but not least, increase your deadbands also! They're set at 3 degrees by default (which is about as high as you can go), however they might be set to less.

    Hope this helps!

  10. #23
    Join Date
    May 2009
    Location
    Bardstown, KY
    Posts
    94
    I agree with Lafittejdubb on the leak through. Have seen it a few times myself. Also, did they load this end of the server room more so than the rest? Have seen that a few times as well.
    Also, guys, he is in the AOP section as a owner, so why not help instead of dogging him? Just saying.

  11. #24
    Join Date
    Sep 2007
    Location
    Boise, ID
    Posts
    4,259
    Quote Originally Posted by HeyBob View Post
    CRAC=Computer Room Air Conditioner

    ACU Air Conditioning Unit
    I think he was pointing out the irony of his request not to abbreviate.
    If a nation expects to be ignorant and free, in a state of civilization, it expects what will never be. (Thomas Jefferson 1816)

  12. #25
    Join Date
    Feb 2011
    Location
    Sacramento, CA
    Posts
    147
    How about a model number? Does it have a semi hermetic compressor? If so have you checked the valve plates by testing to see if they hold pressure? Let the system pump down, front seat the suction valve, does your pressure in your compressor body rise? If so you are leaking through the discharge valves. If not try front seating the discharge valve with the suction valve open after pump down, if pressure rises you have a bad solenoid valve. The bad discharge valves has been the cause for 90% of my short cycle alarms in the past because most of my CRAC's see constant loads. I have seen one solenoid valve bad and it had something stuck in it not allowing it to close off properly. A burn out that was not properly cleaned up, clogged the TXV as well.
    I have done so much with so little for so long, that now I can do almost anything with nothing at all.

  13. #26
    Join Date
    Apr 2008
    Posts
    155
    Quote Originally Posted by GoColts View Post
    How about a model number? Does it have a semi hermetic compressor? If so have you checked the valve plates by testing to see if they hold pressure? Let the system pump down, front seat the suction valve, does your pressure in your compressor body rise? If so you are leaking through the discharge valves. If not try front seating the discharge valve with the suction valve open after pump down, if pressure rises you have a bad solenoid valve. The bad discharge valves has been the cause for 90% of my short cycle alarms in the past because most of my CRAC's see constant loads. I have seen one solenoid valve bad and it had something stuck in it not allowing it to close off properly. A burn out that was not properly cleaned up, clogged the TXV as well.
    Ding. Two months to get to this

    Liebert (ie Carlyle) back about then apparently had some 'new improved valves that tend to leak. (Liebert support indicated to me they set them (carlyle) straight once the warranty stuff started coming in I guess.

    Hey there Sac'..

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