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Old 01-16-2012, 08:54 PM
bline bline is offline
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Default Downflow CRAC w/o raised floor

Has anyone heard of using a downflow CRAC without a raised floor? The reason I ask is for a hot air containment setup with return air ducting back to the CRAC.

Any pros/cons or alternate methods of HAC without a raised floor?

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Old 01-16-2012, 09:13 PM
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KenB KenB is offline
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This white paper from APC discusses the pros and cons of a variety of raised floor and hard floor data center cooling options: http://www.apcmedia.com/salestools/N...N9QM_R2_EN.pdf

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Old 01-16-2012, 11:59 PM
vincent_byrne vincent_byrne is offline
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There is nothing wrong with this method of design in theory and if you were to gain access to many of the fresh air cooled data centres around the world you would see this design in action. Although many of these designs use the complete room side walls to deliver the air into the room so that the airspeed is reduced and pressure is correct.

There is a number of things to be aware of when distributing your air in this fashion.
Firstly the air will be entering the room at very high speeds especially if you have a large room which requires large amounts of air volume.
Here are some suggestions to overcome this problem.
1 Firstly position the CRAC units perpendicular to the rows.
2 It may be possible to reduce the velocity of the air by positioning the CRAC;s so that it is opposite the HOT aisles. This will mean it has to hit the containment doors first and then go around the corner into the cold aisle.
3 You will also need a good gap between the CRAC units and the start of the rows. (At least three tiles)
4 You will need wide cold aisles.

One other factor to consider is what happens during CRAC failure especially failure of the the end units, ie the last CRAC in the row. There is a high possability of creating a hot spot.
NOTE all CRAC units will need to be maintained at regular intervals so this condition will arrise at least twice a year.

I have worked on data centre layouts for many years and always used our inhouse CFD to proof the airflow patterns and this is definitely one design concept that will have to be modelled.

But In theory it can be worked.


Last edited by vincent_byrne; 01-17-2012 at 12:04 AM.
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Old 04-02-2012, 06:10 PM
DC Electro-Mech DC Electro-Mech is offline
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I have actually designed and built a small DC (less than 5K sqrft) using this method. Cost was the major reason a raised floor was not put in place. Plus the fact that most areas require ramps for their raised floor which eats into the DC real estate.

We had this done and we were able to sufficiently cool the DC and we provided the proper ducting to direct the supply and return air streams to help "optimize" the plan. I stay in frequent touch with the DC and they are running just fine and we are looking at additional capacity for growth.

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