In modern data Centers drop ceiling is installed. The reason being you can create a AIR plenum. If your not going to have a air plenum then you should not have a drop ceiling. If you look at the in the link below you will see were the red arrows are thats were you would installed drop ceiling perferated tiles. Then the crack you will have a housing that sits ontop of the crack unit connected the ceiling to it and pulls air in. [1]http://www.panduit.com/stellent/groups/marketing-corp/documents/land ing_pages/~export/CMSCONT_034718~13/34864-5.gif Jmercado May 2, 2009 06:53:16 AM, [2]jbates@brightok.net wrote: William Herrin wrote: > You shouldn't even *have* a drop ceiling in a modern computer room. > You want the room to be as tall as practical so that the air from the > hot aisles has somewhere to go on its way back to the HVAC, other than > back through and around the cabinets. > I love my 30' ceiling. Even with all the things that are wrong with our HVAC setup, the servers survive due to that ceiling. > Personally, I've found that there's a pretty wide disparity between > HVAC professionals that are capable of hooking up a CRAC and turning > it on versus HVAC professionals that understand the holistic picture > including hot aisles, cold aisles, humidity control and flow. I > wouldn't want to call in a professional without first understanding > the problem well enough to assess whether I was getting a competent > answer. I had this issue. They hooked up the redundant systems, but didn't bother with much else. The return feed is below the units pulling ambient air, and the cold air is injected 15+ feet above the isle behind the servers, intermixing with the hot air as it rises up the wall. At least it works, but it could be better and changes will need to be made before I can reach 50% capacity in the racks. Jack References 1. http://www.panduit.com/stellent/groups/marketing-corp/documents/landing_page... 2. mailto:jbates@brightok.net