A History of Perforated Panels in Computer Rooms
The brilliant idea to take advantage of using a raised floor as a supply plenum came to life in 1960 when computers and raised floors became synonymous. Raised floors offered flexibility to the growing data center. When equipment was upgraded, air flow grilles could be relocated, and the cooling loads could easily be balanced. (CRAC) Computer Room Air Conditioning units were installed with raised floors and these units directed huge volumes of conditioned air under the raised floor. Strategic openings were needed in the computer floor to distribute the air flow.
Air Flow Grilles were the standard for many years. Grilles were available in several sizes, both with and without operable dampers which could be adjusted without removing the grille from the raised floor panel. Each grille could be dropped into place using a simple rectangular cutout in the computer room floor.
Each grille could be inserted either horizontally or vertically along the row of computer hardware to adjust the flow of air and keep the equipment at optimal operating temperature. These grilles had aluminum vanes which were spaced close together to keep small objects from falling into the subfloor and to keep high heels from catching in the grille. Grilles were originally available only in cast aluminum, however; later on both plastic and lexan grilles were used.
Standard perforated floor panels replaced grilles fairly quickly. Perforated panels are the same size as a standard solid access floor panel and are available both with and without operable dampers. The open area of a standard perforated panel is 25% of the entire surface of the access floor panel. This means that there is one square foot of open area in each perforated panel. Perforated panels became popular for two main reasons. First, the load on air conditioning increased as the rows of equipment became more dense in the computer room and perforated panels offered more open area for air distribution. Second, perforated panels were available in matching surface coverings so they presented a more harmonious appearance. Perforated panels are typically available with either high pressure laminate, conductive laminate or conductive vinyl. There are several hole patterns, each associated with a specific manufacturer. Perforated panels were offered in the same 24” x 24” size that a solid access floor panel was manufactured. The perforated panel was also constructed to withstand heavier loads than previously available. Perforated panels are typically available in concentrated loads of 800 pounds, 1000 pounds and 1250 pounds. Since perforated panels are the same size as a standard access floor panel they can be placed anywhere in the data center. They are easily moved from one location to another without disturbing the working environment. Perforated panels are also used in office environments in combination with carpeted access floor panels.
Perforated panels in the office allow for individual climate control and for offices with a high churn rate repositioning is simple and fast. Originally the holes in perforated panels were drilled straight down from the top, however, in later years the holes were chamfered to facilitate the use of perforated panels in a closed air system. Perforated panels are used extensively in clean rooms. They allow air forced from the ceiling to pass through the chamfered holes to the subfloor and be collected, cleaned and recirculated.
High velocity grates are the most recent addition to the raised floor air distribution menu. High velocity grates are 24” x 24” and require the support of a bolted stringer understructure. They are not compatible with stringerless understructure. High velocity grates are interchangeable with standard access floor panels with high pressure laminate coverings. High velocity grates are typically provided in die cast aluminum both with and without dampers. These grates are available in a range of finishes including brushed aluminum with a mill finish, powder coated and epoxy coated. Many high velocity grates have a conductive coating. High velocity grates are made for most access floor systems, including woodcore, all steel, concrete filled steel and aluminum. High velocity grates allow for between 55% and 65% open area, thus providing much more air flow and cooling capacity than ever before. These grates have rigid vanes or a distinct punched pattern on the surface. The newest high velocity grates are made with adjustable legs or feet which allow them to be adjusted from above and interface with obsolete access floors. Some of the newest options include subfloor fans, built in temperature controls and directed flow of air to the face of equipment.