Page 96 of 99 FirstFirst ... 46868990919293949596979899 LastLast
Results 1,236 to 1,248 of 1276
  1. #1236
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560
    Dear ACCMan,

    Well said, or shall I say......well posted.

    The really sad ending of this project is the fact that the original Trane split system “might” have been adequate for this project had the original installing contractor installed the right components to modify this stand system, and if he had provided a complete and comprehensive commissioning of the system.

    Welcome to this forum and hopefully we’ll see more of you later in other threads. I would offer this one suggestion to you though………fill in your personal profile so we can all see who we are posting to.

    Have a great day!

    Respectfully Submitted,
    John J. Dalton

  2. #1237
    Join Date
    Sep 2004
    Location
    Newbury Berkshire
    Posts
    490
    Couldn't resist it.. 3 x 10kw Daikin cooling only splits...





    Cheers

    Richard

  3. #1238
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560

    Don't get me started Guys.........

    Dear Barty,

    Where to start.......?

    1: Normal AC = 400 CFM/ton
    Server Room AC: 500 - 750 CFM/ton
    Daikin AC = 300 CFM/ton..........so much for sensible heat efficiency.

    2. Hot isle, cold isle, short circulation loop on the short end of the Server Rm.

    3. Server room filtration...Daikin sponge rubber filters.....enough said.

    4. Low server room ambient conditions.....Diakin to the rescue......NOT!

    5. Ect, ect, .........

    Sorry....coundn't resist.

    Respectfully Submitted,
    John J. Dalton CM

  4. #1239
    Join Date
    Apr 2002
    Posts
    11,808
    Quote Originally Posted by barty View Post
    Couldn't resist it.. 3 x 10kw Daikin cooling only splits...





    Cheers

    Richard
    Richard

    You would pretty much have to mismatch those daikins in my opinion, really over size the fan coils, maybe see the thread over at marcs. Don't argue with dear john, he does cray supercomputers
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  5. #1240
    Join Date
    Sep 2004
    Location
    Newbury Berkshire
    Posts
    490
    Quote Originally Posted by Carnak View Post
    Richard

    You would pretty much have to mismatch those daikins in my opinion, really over size the fan coils, maybe see the thread over at Marc's. Don't argue with dear john, he does cray supercomputers

    The current range of Daikin inverters have a 'data room' option which will enable the software to control in these environments. For some time there has been a conflict about inverters/non inverters in these applications (these are non FYI) It now appears inverters are the best option.

    We had some problems with these units which upon many many discussions and from the experience of this installation and others led to the article.As an example, these do not have suction accumulators, and the refrigerant charge was reduced...The mismatch option a 10kw indoor + 7.1kw outdoor inverter was discussed and would have been our prefered option but due to non technical reasons sadly rejected. However lessons have been learnt for sure..

    I don't think it has swayed me against using these units just be more exacting on application and specification. I still see the need for close control systems but feel they are such crude 'wind and tin' devices and need to incorporate many of the features seen on the most basic minisplit..



    Cheers

    Richard

  6. #1241
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560

    One size DOES NOT fit all

    Dear Richard,

    The fundamental problems I see when incorporating ductless mini-split systems for high density server or date rooms is as follows:

    1. The minimum CFM/ton of cooling should be in the range of 500 to 750 CFM/ton, at best these are what…. 250 CFM/ton, the sensible/latent heat ratio of these units make the system inefficient from the start.

    2. The air changes per hour of these newer denser server or data rooms are increased from the normal 4 to 8 AC/Hr. that one would see in a typical office area to well over 200 AC/Hr. making air filtration an extremely important factor. These units are equipment with minimal return air filter area with minimal efficentency.

    3. The air characteristics of a modern dense server or data room call for specific airflow of both the return and the supply air into and out of the room, these systems do not poses the flexibility of other than normal window unit type airflow and directional movement.

    4. What do these units poses in way of a low evaporator heat load condition in the room? What about low ambient operating temperatures when full cooling is required in the room?

    Inverter control of the compressor in DX systems have made a small, but important dent in the more conventional chiller type systems for close capacity control, but there has to be more to a server or data room system than this alone.

    Given the way things are progressing in our industry, I’m sure that in time, these systems will be designed, built, and installed specifically for these types of rooms, but until then, lets not make one size system fit all.

    Just my option…………

    Respectfully Submitted,
    John J. Dalton CM

  7. #1242
    Join Date
    Sep 2004
    Location
    Newbury Berkshire
    Posts
    490
    I wonder why there seems to be a real lack of cohesive thinking about server room a/c.

    Most don't use floating head or heat recovery. They use electric heaters whilst discharging heat outside.Precious few use the free cooling.Poor design poor layout. Huge server farms with little or no consideration to airflow just get her to 16 , or for the use of plastic curtaining to give the room cold & hot spots for better efficiency etc.

    Wasteful wasteful in the extreme.

    Inverter drives are never used and electronic expansion offered as an expensive add on.

    These systems given the fact that they are 24/7 should be forced to have an energy rating at least equal (all factors considered) to a cheapo ebay special.

    These wall mount comfort cooling units have never caused the slightest hiccup with the servers and the team are real happy with the performance. The also have a high seer rating.

    We must get these manufacturers to drag themselves and the buyers of these systems into the modern world by legistlating if necessary with huge carbon taxes for poorly engineered, spec'ed and bought server room set ups.

    Cheers

    Richard

  8. #1243
    Join Date
    Sep 2007
    Location
    Newark, Ohio
    Posts
    112
    Quote Originally Posted by airtoo View Post
    It's unfortunate that your area contractors couldn't provide you with better service. How about a mechanical engineer? They may be a little expensive but how important is the equipment you are trying to cool or the data they store and transmit.
    Something to consider if your real comfortable with your own calculations. If 53482 is all sensible than you need to find a system(s) that will provide you with that sensible capacity. A 5-ton will provide you at best 60,000 BTu total, but of that only 38000 to 39000 btu of sensible, the rest is latent capacity.
    You may want to call your area Leibert supplier. They specialize in computer room a/c. As much as we don't like it, alot of them sell direct to owners, and recommend a contractor to do the work.
    I am having trouble understanding the sensible/latent capacity of the A/C. Can someone explain how this is determined?

  9. #1244
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,779
    If understood correctly, Daikin has a variable refrigerant flow line of product which even can charge itself with refrigerant, as well as can vary the output of cooling to 50% of rated output. (could cool for 2 ton load upon demand while being a "4 ton" system.)

    Bet Mr. Slim is going to put up the "prevent D".
    It's great to be alive and pumping oxygen!

  10. #1245
    Join Date
    Apr 2005
    Location
    where the beer flows like wine
    Posts
    2,871
    chuck,

    Sensible heat removal refers to the type of heat a regular thermostat measures for example heat gains from sun light, lamps, equipment, people etc, latent loads refers the removal of moisture or the condensation of water vapors on the coils surface.

  11. #1246
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,779
    Quote Originally Posted by Chuckg222 View Post
    I am having trouble understanding the sensible/latent capacity of the A/C. Can someone explain how this is determined?
    I'm way down the totem pole on the total explanation but let's continue the conversation anyway...

    Latent heat is not as much of a factor in most server rooms, when proper room seals/vapor barriers are applied. The heat load from many if not all of today's servers is more sensible--approximately 90%/10% sensible-latent as opposed to typical cooling ratios which have more latent heat. Latent heat has more to do with moisture content in the air.

    Computer rooms have a "higher density" heat load or concentration than you will typically find in comfort cooling, and so computer rooms need more airflow to change the air while cooling that load. On the other hand, in typical cooling, the number of air changes per hour can be reduced, which will subsequently remove more of the moisture. Hence, we slow the blower speed in dehumidification, even in some server rooms.

    But the lion's share of cooling in server rooms/phone rooms/computer, etc. is removing sensible heat which in these rooms is more dense.

    In certain places, such as switch rooms for cell phone providers, for example, at close of business day, the room will heat up more rapidly than at non-peak times of cell usage, because people get in their cars, shout "yabba dabba doo", and pick up the cell phone. Thus, the heat load in a phone room there will increase in direct relation to the computer processing. But not to get too far off the beaten path....
    yes, but it's a dry heat.
    It's great to be alive and pumping oxygen!

  12. #1247
    Join Date
    Sep 2007
    Location
    Newark, Ohio
    Posts
    112
    I understand the difference between sensible and latent but why is the 60,000 BTH unit only capable of 39000 BTU of sensible and the rest is latent?

  13. #1248
    Join Date
    Apr 2005
    Location
    where the beer flows like wine
    Posts
    2,871
    Quote Originally Posted by Chuckg222 View Post
    I understand the difference between sensible and latent but why is the 60,000 BTH unit only capable of 39000 BTU of sensible and the rest is latent?
    A unit could be engineered to provide a given sensible to latent heat removal ratios. I dont think a generic DX unit right out of the crate will have a set ratio, it would float all over the place depending on the space conditions.

Page 96 of 99 FirstFirst ... 46868990919293949596979899 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event