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  1. #14
    Join Date
    Dec 2004
    Location
    Chicago area
    Posts
    1,453
    Quote Originally Posted by internala/c View Post

    Did you say 48% -52% RH? That is important to the circuit boards right? Well have you seen the size of those condensate pumps in the mini-splits? They don't look like they can handle that kind of humidity. I'd be pumping that out onto a sub-freezing roof top too. Oh this is getting time consuming.

    Internala/c
    48-52% RH too much above 50 and condensation can cause boards to short, too much below and static will occur.

    Dedicated computer room equipment is designed with a different set of rules then comfort cooling. The first and likely the biggest is operational hours.

    A comfort cooling unit is designed to operate about 2300 hours a year, while a a computer room unit is designed to run about 7800 hours a year.

    The other is humidity control a computer room unit moves the air faster, so the humidity in the air stays in the air, has the ability to run heat and cool at the same time to dehumidify, they can humidify, run in heat, run in cool, or any combination it sees fit to maintain the tolerance of the room.

  2. #15
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790
    Quote Originally Posted by internala/c View Post
    . Oh this is getting time consuming.
    Speaking of time consuming, you might want to examine this thread here

    It's called cooling a small server room. Make sure to start at post # 1.
    It's great to be alive and pumping oxygen!

  3. #16
    The mitsubishis are 2.5, 2.5, and 3.0 tons the emer. backup really never runs so yea it still equals around 15 tons of cooling. The minisplits are "low ambient" capable but are not "0' deg." capable. thats a factory option. I have put a call into the Liebert rep.
    I will look into the APC set up to see if they know anything about HVAC.

    Internala/c

  4. #17
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    6,364
    Quote Originally Posted by internala/c View Post

    I will look into the APC set up to see if they know anything about HVAC.

    Internala/c
    I think they know a little something about server rooms.

  5. #18
    Join Date
    Dec 2007
    Location
    Midwest
    Posts
    638
    Quote Originally Posted by internala/c View Post

    mikesands,
    Point well taken. I will propose a dedicated server room unit and at least they'll be aware of a more reliable solution. Although, What modifications were you thinking of?
    I was referring to the modifications that you were proposing , adjusting the economizer etc,,, those are modifications to their system.

  6. #19
    It sounds like one of the usual ad-hoc server room expansions. 12 pounds of crap stuffed in a 10 pound bag.

    Liebert and Stultz ATS are your two best options. Stultz will likely be cheaper, but it doesn't come with all the bells & whistles.

    First, if you are redesigning this, get an engineer. A server room going down on your watch is the last thing you want to do to your company & your bank account. Get the engineer to take the risk and (over)size everything for you. Be sure to get very specific direction from that engineer so you can simply point the finger if the shat hits the fan. Maybe that engineer will say it isn't worth the effort or risk to revise what they have.

    The economizer mode could work; however, there will need to be decent mixing to avoid any trouble with freezing, whether in the unit or in the space. Modifying it might be some trouble if its not configured already. You could go well above 20*F for the economizer and still be running it at 100%. You'd need to calc what the loads vs. temps are based on the existing equipment. The controls would need to be modified to provide a good buffer for when the temperature changes so it doesn't need to react & recover too fast.

  7. #20
    Join Date
    Mar 2005
    Location
    Pacific Time Zone
    Posts
    4,228
    Data Aire is another option - www.dataaire.com
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  8. #21
    Join Date
    Apr 2007
    Posts
    7
    I would suggest contacting a mechanical firm that has data center engineer experience. From the sounds of the setup you're working with, the owner hasn't wanted to fork over the money to do it right and instead continues to apply band-aids to their setup as they continue to add more devices. I predict things will get dicey very quickly in it's current state.

    Economizers are a great thing, if done, and controlled correctly in a data center environment. I am looking forward to opening my new 8000 sq ft data center on air-side for approximately 90% of the year. No need to go to 20F, 65 is a much more usable number.

    Also, 48-52% RH is absolutely too stringent. The old ASHRAE spec called for 40-55% and the 2008 Guidelines call for 5.5*C DP to 60%RH and 15*C DP. I currently run my data centers at 20-80% RH. They've also updated allowable temperature ranges. Give it a look, if interested - http://tc99.ashraetcs.org/documents/...Aug_1_2008.pdf

    Best of luck.

  9. #22
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790
    One issue with ever having to preheat outside air for economiser is that you will be periodically heating moths, and oak leaves.
    Try managing that with an FM 200!
    Hope you like going into work.

    1800 543 2378
    It's great to be alive and pumping oxygen!

  10. #23
    Join Date
    Mar 2008
    Location
    Northeast
    Posts
    128
    Humidity control is only a small part of data room environment (20-80%) is both to low and to high.....

    More important to server board life is (TROC) Temperature Rate of Change... computer chips are very sensitive to the rate of change in amb air temp....

    A proper level 3 data center would want to see a TROC of about
    1 to 9 degree/Hour.


    normal AHU controls almost never take troc into consideration but Leibert,data Aire and others designed for this application do.

    -V-

  11. #24
    Join Date
    Apr 2007
    Posts
    7
    Yes. It is a small part of the environment, but 20-80% is neither too low or too high. If it was, I would have been having issues the last 2 years I've been running this way.

    There is this fear, especially from IT people, that the band is too wide. You tell them that running @ 77F inlet temp is acceptable and there is a look of horror on their faces.

    But I have heard of problems related to TROC, mainly due to the expansion/contraction of tape and hard disk platters and the data not being readable in extreme swings of temp from when they were first written.

    There are a lot of fears and stigmas related to data centers and I will admit to going the way of those who like to push the envelope on new ways of thinking.

  12. #25
    Quote Originally Posted by marauderx View Post
    It sounds like one of the usual ad-hoc server room expansions. 12 pounds of crap stuffed in a 10 pound bag.

    Liebert and Stultz ATS are your two best options. Stultz will likely be cheaper, but it doesn't come with all the bells & whistles.
    We certainly agree that an engineer should be consulted with! However, we respectfully disagree that Stulz doesn't come with all the bells and whistles.

    As a matter of fact, Stulz comes with more features than Liebert. But at the end of the day, bells and whistles aren't what keeps your load cool. A high quality, reliable unit is!

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