Arlyn S. Powell, Jr.
The World Bank (Washington, DC) is installing an innovative modular wiring system in its new, 18-story headquarters building, scheduled for completion next spring.
The result of a collaboration among the World Bank organization`s technical staff, electrical contractor Dynalectric Co. (Sterling, VA), and two equipment vendors, AMP Inc. (Harrisburg, PA) and America Cable Systems (ACS, New Bedford, MA), the cabling plant consists of a prefabricated, factory-built, modular zone-wiring system that combines power, voice, and data communications. The system is deployed under a modular raised floor and delivers services through floor boxes.
The electrical contractor has estimated that using such a modular system has substantially reduced the total cost of wiring the building. "The savings in installation [costs] is about 30% over a conventional hardwired approach," says George Minor, project manager for the World Bank job. "For example, we figure a crew of five or six can install a whole floor in a single shift using this system. With a conventional hardwired system, you`d need at least two or three more in the crew, just for handling all the different material and equipment you need."
Another advantage of such a modular system is that it can incorporate built-in spares. "The voice and data cables," explains ACS Vice President Richard E. McGrail, "consist of a bundle of 18 conductors, of which 12 are assigned and 6 are spares. They can be used for new services, or as backup. In case of a line failure, the interrupted function can be reassigned to spare conductors."
Such changes can be made at zone distribution boxes spread around the floor, simply by unplugging from the faulty line and plugging into a spare. If a box is being fully utilized, other alternatives are to use a spare on a nearby box or make the switch on the punchdown board in the wiring closet. "Service can be maintained with minimum intervention and a high degree of reliability," McGrail adds.
The zone distribution boxes make the World Bank installation unique, in that this is one of the first major construction projects in the world in which the power and data wiring systems are so closely integrated--and the two systems come together in these boxes.
David Salak, senior information officer in the Information and Technology Services Department of the World Bank, thinks the new system has the potential to generate substantial long-term benefits for the bank. "With this distributed wiring system," Salak says, "disturbances in the office layout only ripple back from the point of the change as far as the zone distribution box. They don`t ripple all the way to the wiring closet."
A crucial factor for Salak is that retermination is not necessary for moves, adds and changes. "The connections into the floor-access box are all preconnectorized, plug-in connections," he says, "so you just unplug them and replug them. And it`s usually easy to pull the wires over to the new location, because there are no stringers under the floor to block the path."
Salak estimates that there is a 30% annual churn factor in his organization, which means that one of three employees moves each year. At a cost of $200 per office drop to make a change, the World Bank expects to show substantial savings with its flexible new system.
Dynalectric, the electrical contractor for the project, also remains enthusiastic about modular zone wiring. The company estimates that approximately 10% of its projects currently embrace this technology. "We believe that percentage will go up," says Minor, "because there are so many advantages in terms of reduced installation cost versus conventional hardwired systems using pipe and connector boxes or even flexible cable." The modular system eliminates all on-site measuring, cutting pipe and conduit, pulling cable and making box connections.
A modular system can also be a benefit in open-office environments. If slack is left in the underfloor cables, floor boxes can be moved when the building owner or tenant wants to change the office layout. In this case, you can move the floor boxes as well as office partitions without calling in a contractor. "Less downtime and less disruption for tenants are major concerns," Minor concludes. "It translates into money."
Bernie Long, foreman for Dynalectric (Sterling, VA), installs a prefabricated and integrated power and telecommunications system at the World Bank project in Washington, DC. The system was manufactured by America Cable Systems (New Bedford, MA).