High-Wire Act

By Barbara Horwitz-Bennett, Contributing Editor September 1, 2006

Electrical and communications systems design for today’s high-rise buildings calls for a flexible approach to accommodate the inevitable future adds, moves and changes.

CSE: What are some of the best ways to build flexibility into electrical wiring and communications cabling in high-rise facilities, especially to accommodate MACs (moves, adds and changes)?

VOLTAGGIO : There are a number of important considerations, all of which minimize the time, expense and disruption associated with MACs. They include the following:

  • The provision of adequate capacity in the initial installation to accommodate anticipated levels of growth.

  • Strategic placement of equipment and infrastructure to readily facilitate MACs.

  • Efficient access to equipment and cabling.

  • Establishment of repetitive, modular installations, which simplify the management of the final installation for maximum efficiency.

MAKWINSKI : Building flexibility into a system requires close attention to wire and cable pathways. The conventional method of running wires and cables through the walls and using fixed-position outlets makes it difficult to accommodate changes in the physical layout, the popularity and efficiency of open space environments and advances in technology. Integrated pathway solutions are specifically designed to provide the accessibility and flexibility required for efficient building function. These systems allow easy access for cabling change-outs and flexibility for non-invasive MACs. Solutions include:

  • Surface raceway that manages wires and cables on the wall, not within it.

  • Infloor ducts, poke-through systems and floor boxes that bring services closer to the user in open spaces.

  • Cable tray systems that manage wires and cables in easily accessed plenum space or under raised floors.

  • Architectural columns that bring voice and data closer to the workstation and reduce size and complexity of the communications closet.

NARIMAN : The first order of business should be to discuss with one’s client what degree of flexibility the business model calls for, and more importantly, how much of the construction budget should be allocated to it. The degree of flexibility is really only limited by what premium the client is willing to pay for it. For instance, things like raised floors and trench ducts serving cellular floor decks deliver superb flexibility, but come at a premium in terms of cost.

One of the most flexible, yet economical ways to distribute power in high-rises is a bus riser. Through careful sizing and layout, additional bus taps can serve future panels or transformers on upper floors. Just remember to provide the space for future equipment in the electrical closets.

If a bus riser is not specified, another cost-effective way to provide flexibility is upsizing riser conduits so that larger feeders can be pulled for additional capacity.

On the telecom side, we always advocate stacked telecom rooms (TRs) on each floor of the building directly over the main distribution frame (MDF). In this way the TRs can be used as an accessible backbone pathway that makes it much easier to pull in new backbone cables in the future. As far as horizontal cable pathways are concerned, again, the level of flexibility is tied to the available budget. In descending order of cost, systems such as raised floor, cellular floor decks, cable trays, surface raceways and power/telecom poles all deliver flexibility, depending on the application.

In both electrical and telecom rooms, I always try to organize equipment so that there is some vacant wall space that can be used for future riser cables or conduits to pass. In electrical rooms it can be used for future electrical gear. In a nutshell, delivering flexibility is as much about space planning as it is about equipment selection.

CSE: What are the challenges in cable distribution design and installation for high-rises?

VOLTAGGIO : Some of the challenges are installation of accessible, vertically aligned cable pathways; implementation of diverse routing pathways for security and redundancy; and coordination of routing paths—horizontal and vertical—with structural, architectural and mechanical systems.

MAKWINSKI : For the designer, it’s maximizing building function by meeting current and future space and technology requirements without compromising aesthetics. The designer needs to understand the owner’s key criteria in terms of structure, density plan, intended use for present and future capacity needs and churn rate.

Another challenge is funding—not only for the material and labor of initial installation, but more importantly, for life-cycle cost. And with the advent of 10-Gig cable, network issues such as cable bend radius, pull tension and fill capacity must also be addressed.

NARIMAN: I’d have to say that one of the more challenging aspects of high-rise cable distribution is coordinating with ductwork, piping and gypsum board ceilings. These and other obstructions may render the most flexible distribution systems useless.

Another challenge is designing to avoid excessive voltage drop. On the telecommunications side, a related concern is not exceeding maximum backbone cable length. We also try to avoid having more than one intermediate cross-connect in the backbone cable path.

CSE: What specification tips can you offer to help navigate the hurdles?

MAKWINSKI : Keep in mind the objectives: accommodating the requirements of the facility while providing maximum functionality, lowering life-cycle cost and maintaining the aesthetic appearance the owner—and tenant—envisioned. Understanding the relative advantages of various pathways enables the designer to avoid antiquated delivery systems for wire and cable infrastructure.

NARIMAN : In terms of specifications, we often call for oversized bus risers, conduits, pull boxes and support systems that can continue to be used even as occupant demand increases. For telecom, we have had success specifying plenum-rated cables in basket-type trays. We also specify equipment racks with space for additional patch panels to be installed in the future. These allow telecom cabling to be easily added or moved in the future.

Also, we often have requirements in our specifications for complete coordination drawings to be developed by the contractor before construction begins. These drawings should show, in detail, the routing of ductwork, piping, cable trays and large conduits, as well as elevation details for systems above corridor ceilings. These identify conflicts and ensure that necessary access is provided.

VOLTAGGIO : Navigating the challenges is critically related to project design philosophy and process. At the core of this philosophy is an acknowledgement of the positive impact on the project life cycle derived from proper installation of cabling and equipment. Once this priority is established, it is essential that the process includes key design and implementation considerations for electrical and communication systems from inception. This degree of early participation facilitates incorporation of flexible, cost-effective solutions while minimizing impacts to architectural/structural considerations.

CSE: What else can designers do up front to avoid future problems with abandoned, mislabeled, mixed-up or improperly secured wiring?

NARIMAN : Again, I believe having the contractors take the time to develop coordination drawings sets the stage for a neat and organized installation. We also encourage our clients to keep complete and up-to-date drawings of their building systems. Up-to-date master drawings make future projects go much smoother. They identify what cables and equipment are present and allow engineers to determine whether they need to be removed, abandoned or modified. I’ve recently worked on several projects whose sole purpose was to survey an electrical system and create up-to-date master one-line diagrams. The facility users found these documents invaluable for maintenance and planning.

MAKWINSKI : Part of the answer comes back to pathways—specifying a complete, integrated, end-to-end pathway solution. In situations where standard products don’t quite fit the bill, inquire whether the manufacturer can provide a custom solution. Designing such a solution in advance is preferable to trying to improvise something in the field.

One area that should never be neglected is firestopping. Specifying a firestop system that is compatible with the cabling pathway is a far better option than leaving the choice to an installer who may be unfamiliar with current technology.

VOLTAGGIO : And one mustn’t forget about crafting project specifications that establish a policy regarding abandoned cable and equipment. Well-run facilities remove abandoned cable and equipment on a continuous basis. Avoiding mislabeled, mixed up and improperly secured wiring is a function of specifying proper management techniques, coupled with thorough field commissioning to identify and remediate conditions that deviate from specified requirements.

CSE: What should be anticipated as far as the effects of the electrical and telecom cabling on a building’s HVAC systems?

VOLTAGGIO : The major impact on HVAC systems does not necessarily flow from the cabling itself, but rather from the equipment that it is connected to. The heat generated by electrical and telecom equipment has a significant impact on HVAC systems, because appropriate ventilation and cooling strategies are essential to proper functioning of this equipment. And with the advent of new data system technologies, this challenge is intensifying.

Electrical and communication systems present physical coordination challenges as well. Horizontal conduit and cable tray routing in ceiling and raised-floor cavities is an area where mechanical ductwork and piping impacts can be expected.

MAKWINSKI : Actually, I think raised access floors are the only emerging pathway strategy where HVAC and wire and cabling coexist. While raised access floors provide future flexibility, many designers encounter cost-related objections, and so they must pursue alternative pathway strategies that separate the cabling infrastructure from the HVAC systems.

NARIMAN : As HVAC systems become smarter and more efficient, this creates challenges for cabling in terms of power quality. For example, equipment like adjustable-speed drives used for HVAC often cause harmonic distortion on the building electrical distribution system. Consequently, it is recommended to segregate HVAC power distribution from sensitive building loads. With respect to telecom cabling, in the future, Internet-based and wireless HVAC controls will facilitate integration into the building’s overall structured cable-distribution system. It will eventually end the days of separate cabling and pathways for telecom and controls. This will lead to a more flexible and organized cabling system.

CSE: What new products are available to help efficiently organize cable in high-rises?

MAKWINSKI : One of the fastest-growing aspects of communications is audio/video. There is a tremendous demand for A/V connectivity. New products have been designed to incorporate A/V poke-through devices, floor boxes and other pathway solutions. Yet another family of products is enclosures and other housings for wireless access points. These devices can be concealed in a wall, an architectural column, above the ceiling or even within a perimeter raceway.

NARIMAN : One new product is a recessed floor box for raised-floor applications. The product is applicable anywhere a high degree of flexibility is needed in raised-floor environments, like telecom equipment rooms. The boxes are connected to an underfloor plug-in bus via flexible armored cables. The armored cables come with factory terminated plug ends, and the box has receptacles pre-wired to the flex cable with space for data jacks. Several manufacturers have similar products at this time. The floor boxes can be moved around or added to suit rack-mounted equipment as needed. Consequently, owners can move the floor boxes around without shutting down the whole system. Since the boxes easily plug into the bus, owners can do it themselves without having to hire an electrician. In a nutshell, it is a very flexible and economical system.

VOLTAGGIO : All the traditional products are still in widespread use today. But inrecent years, a number of competing software packages have emerged, designed to streamline the ongoing task of system and cable management.


Mark Makwinski

Director of Advanced Engineering


West Hartford, Conn.

Garrett Nariman, P.E., RCDD, LEED AP

Senior Electrical Engineer

The RMH Group

Lakewood, Colo.

Tom Voltaggio, P.E.

Sr. Vice President


Systems Design