| LOW-VOLTAGE CABLE ROUTING
Few industrial or commercial applications use as much low-voltage wiring as medical facilities, with many new hospitals having more than two dozen different systems. Determining where to install this cable—underfloor or overhead—is an important decision that should be closely assessed.
Cabling has gone from overhead to below the raised floors because there is better airflow through the raised floor plenum. Additionally, raised floors are a welcome option for installations that include a large number of cables, such as in a hospital. Instead of running cables overhead, they can be easily installed and rapidly changed under the raised flooring.
For communications cabling, raised flooring has a number of advantages, such as an outlet can be located anywhere on the raised floor and any number of conductors may be routed to that outlet. Further, radiology equipment may be updated or replaced many times during the life of a hospital. Raised floors are common in radiology equipment rooms, such as CAT scan and MRI rooms, which generally include new control cabinets in different room locations and new cables and routes.
While running the communications cabling under the floor has some advantages, it also presents design and installation challenges. If other systems will be running underfloor, such as electrical, HVAC, plumbing, communications, and fire suppression, it will take a lot of coordinating between all of the trades. Everyone has to work together to make this a success.
The negatives of underfloor cabling include the potential for cables to block airflow, possible space constrictions, and some unintended consequences of removing a floor tile to access the cable.
Underfloor cabling design
Cables must be rated for the location where they are installed, which would require a plenum- or riser-rated cable. A few manufacturers have developed products that are both plenum and wet-rated, but the electrical contractor may not always know in advance whether that type of cable will be installed. To avoid this issue, it is always best to extend the underground or in-slab conduit—for both floor boxes and any outlet outside—to the serving communication room and stub it up there.
Defining the depth of the underfloor space must depend on a careful consideration of its uses. Otherwise, the layout of flexible conduit from a power-distribution unit could block the airflow from an HVAC unit. Chilled-water-pipe diameter, flanges, and insulation must all be taken into consideration in order to facilitate proper system operation and to provide adequate maintenance work space. Once the dimensions are determined, the architect and structural engineer must make the necessary accommodations to ensure these dimensions are achieved so that there is a smooth transition into the raised-floor area.
Raised flooring is a vital part of how a facility operates. By elevating the working floor surface from the subfloor, a useful space is created for air distribution, power cables, and data and voice wires. Once only used in data centers and electrical control rooms, many architects and facility owners/operators are realizing the benefits of raised floors.
Matt Odell, RCDD, is the director of technology for S2N Technology Group, a technology contractor and wholly owned subsidiary of Clark Construction Group. He serves as the company’s central point of contact for customized design, installation, and support for information technology (IT) services for new construction and renovations. Odell may be contacted via e-mail at email@example.com.