Raised floors provide better cooling efficiency for basic principle. The principle is air flows from cold to hot and from bottom to top. In case of elevated floors, Cooling is being done from under the flooring. This use cooling to maximum and provide you efficient cooling.
why do we even need raised floors? don't hot aisles and cold aisles basically take care of cooling needs more efficiently? won't it interfere with the whole idea of containing hot and cold air and not letting the two mix?
Sweetgreen, no. the cooling devices are not fitted under the raised floors. the air is merely directed to the room. with this, one is better off cooling the entire room. they come in both forms, meshed and solid plates.
raised floors have been there for some decades now. but that does not mean it is the most effective. data centers these days prefer omitting the raised floor altogether. cables are becoming thicker. it obstructs air flow to the room disrupting the sole the reason for its existence. most data centers are going in for overhead cabling these days.
It makes perfect sense to me. All of the equipment has fans to keep it cool. Raising the floor is just another way of helping the air flow. Sort of like how your laptop gets hot if the holes on the bottom are obstructed.
Raised floor that's used for cabling AND for mechanical space has some benefits. Keeping the plumbing out of sight allows more usable floor space for access around racks and their contents while allowing the mechanical and electrical systems to be reasonably out of the way and protected from casual damage.
On the flip side it requires a higher deck to deck spacing for your structure. And you MUST make sure that you're not obstructing airflow when you use the raised floor space as your plenum air supply path.
The best setups seem to have a 3'-4' raised floor which allows for plenty of space for pipework and electrical lines as well as it's installation and maintenance and then 20'+ above the floors for the hot air to rise and then slowly circulate down to the air handlers. Generally, these sorts of spaces work best when the data cabling is then placed above the racks on 1-2 layers of ladder racking.
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CNN Internet Technologies
Data Center Manager
It's simple physics; hot air rises. That's why the raised floor has always been seen as the quintesential data center design for HVAC. Hot/cold aisle don't have anything to do with the concept of a raised floor and is only standard for companies that can't afford to keep throwing money at their data center infrastructure. Larger corporations sometimes ignore the hot/cold aisle concept because they can invest more dollars into just adding more HVAC capacity. Smaller data centers where this expense isn't available turn to concepts such as hot/cold aisles, blanking panels, and air stop technology. Though it's all good practice to do all of those things in any event for any data center.
The main reason why companies opt out of raised floor is cost and front-end convenience. Raised floor tend to be more efficient with cool air distribution, more asethetic, and functional for being able to isolate electrical conduits and piping.
In a raised floor the CRAC units are on floor level and are called "down flow" units which blow the air under the floor through an opening on which they sit. Larger data centers will have an airhandler that will plenum the cool air under the raised floor if down flow CRAC units aren't being used.
The primary challenge to a raised floor environment is airflow obstruction because of underfloor infrastructure such as cable trays, conduits, cabling, and piping. That's why a smart underfloor design and execution is critical. You wouldn't run cables and cable tray down an area that would impede sufficient airflow to critical systems. Most data centers get a poor rating for this as they don't actively practice being pro-active and smart in their underfloor design. Newer data centers will combine the concept of raised floor for cooling and overhead trays for cabling.
I believe the standard for the height of a raised floor is 36" minimum though this seems to keep changing over the years. But you need sufficient height to be able to squeeze an average sized human under it.
raised floor
