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  1. #14
    Join Date
    May 2008
    Jax Fl.

    Mitsubishi PLA-A36BA Issues

    Posted in wrong post
    Last edited by JRINJAX; 09-10-2008 at 02:08 PM. Reason: Dumb mistake

  2. #15
    Join Date
    Dec 2006
    Middle Tennessee


    bob_scheel;1985123Liebert's have redundancy built in.

    what happens when the blower motor goes bad?


  3. #16
    Join Date
    Sep 2008
    Cedar Rapids, IA
    [QUOTE=Airmechanical;1985903]what happens when the blower motor goes bad?

    Bldg maint is there 24/7 and they are capable of changing it. They have a spare ready to go. Worst case they open the door to the adjacent office and prop it. There's not much heat load left in this "computer room" now that all of the big machines are gone. About 4 PC sized servers and a couple of big line printers. The management decided that it was costing too much to maintain/repair the older Liebert so out it came.

  4. #17
    Join Date
    Sep 2006
    Rhode Island
    Generally there aren’t many people that actually work in a server room at any given time so very little or no outside air makeup is required. The first thing to check is the actual RH in the room and at what level they need to keep it. I like to use a sling psychrometer.... It’s easy to use and doesn’t cost as much as the really good digital RH meters and it’s dead accurate if you use it right. Check for outside air dampers if there are any. Check for any openings where air from outside the room might be coming in. Also check to see if the AC unit has a humidifier that could be malfunctioning. Also ask them if they leave the door open.... Server room doors should be closed at all times. Most server room’s operate at several degrees below normal room temperature and it is very hard to maintain temperature and RH if the door is open.

    In order to control humidity in a room with your cooling coil you also need to reheat the air after leaving the cooling coil or else you will drive the room temperature down during de-humidification. This will also tend to drive the RH up. Which means while you are running the cooling coil to remove moisture at the same time without reheat you are dropping the room temperature which is trying to raise the RH.

    Most IT types have funny ideas about server room temperatures. They tend to want to over cool the room. I recently had a problem with high RH in a server room. When I arrived there to check it out I noticed the room felt colder than it normally did. I took the temperature in the room with my digital thermometer. It was 65 deg F. I checked out the AC unit and everything worked fine but it just wasn’t keeping up with the humidity load. I asked the Server Room Manager why he had the room temp set so low. He was new there and was standing in for the regular guy that was on vacation. He said at his last job they kept the server room’s as cold as possible. I told him I would like to raise the temp setting up 2 degrees to see if we can get this RH under control. He agreed. The next day I checked back and the room temp was 67 and the RH was at set point. Personally I don’t think they need those server rooms any colder than 70 degrees... Lol but try telling that to some IT types.

  5. #18
    Join Date
    Aug 2008
    I know this may be a simple way of looking at it, but I know from expierience I have seen porr designsd of server rooms in buildings with no vapor barriers, and single pane windows in the server room. Before you think it is the equipment make sure you have little to no infiltration of outside air. Just my .02.

  6. #19
    Join Date
    Jan 2007
    Charm City--the city that bleeds
    I hope your excursion with the York goes better than some other applications with RTUs in a server room. For example, the Predator has had issues operating late fall/early winter with time delays related to outdoor air temp and minimum off cycles which were precipitated by low pressure (no fan cycling). That much said, it was the only time that the unit got behind, which in that case was temp, not humidity. But it can still "generate customer concern"
    It was the exception and not the rule, but no fun while on call in the dark on a ladder with strong winds, new site. yada, yada, yada.

    Is this RTU set up for low ambient? Is the outdoor air minimum at 0% ?
    Don't ya just love it when people park a comfort cooling unit on a server room?

    And isn't the latent load in a server room generally 10%/ sensible 90% ?

    As for producing condensation, I guess I've not measured the difference in the volume of condensate produced here vs. that from comfort cooling, but if I were you, I would expect to continue to see condensate being produced any time you're cooling. Not sure why it's being said about "no condensate".
    It's great to be alive and pumping oxygen!

  7. #20
    Join Date
    Dec 2006
    New Manchester, WV

    That doesnt make any sense....

    Quote Originally Posted by Airmechanical View Post
    sounds like that was a bad decision

    there goes your redundancy

    i would of left that system there in case of the primary unit breaking down!

    Doesn't that train of thought go against all IT Logic?? I havent met an IT person yet who can figure out that it only makes sense to have redundancy if it costs you big $$$$ if the servers go down.

    I have an account that has 6 Lieberts running 100% cooling 24/7. If one goes down, the servers start going down in about 10 minutes. If the whole room goes down, it is costing them $2,000,000 (yes that is million) an hour.

    They are putting in another Liebert only cause they are adding MORE servers. When I mentioned adding units for redundancy, they just looked at me like I was stupid......
    Character is like a tree and reputation like its shadow. The shadow is what we think of it; the tree is the real thing.

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