Structured Cabling Systems

Creative Compromise -
Interior Layout of the Telecommunications Room by Chuck Siebuhr

In the November 1999 article, "Creative Compromise," I reviewed an example design for an individual business tenant in a multifloor commercial building. With all horizontal link distances being well within distance limitations, the total office area is served by one telecommunications room (TR). Understanding that there is rarely a single solution, any number of alternatives might have been considered, but there were certain physical and cost constraints that had to be factored into the final decision, hence the term "creative compromise."

Ideally, the equipment could have been placed in one larger room, rather than two smaller rooms. However, in this case, the ideal solution was not an option. After carefully measuring and calculating the overall usable square footage of the area to be served and reviewing the client's minimum requirements, it was determined that one work area outlet (WAO) would be required for every 62 square feet. (TIA standards recommend a basic minimum of one WAO for every 100 square feet of usable floor space.)

In this example, the space provided for equipment proved to be more than adequate, even though segregated. In fact, the division of space might be considered positive by many, since it provides an unmistakable distinction between voice services and LAN/data terminations.

Future Proofing?
Realistically speaking, there is no sure way to future-proof anything, but panels and patch cords could prove to be a forward-thinking decision as technologies continue to evolve. Opinions will vary, of course, as will individual site-specific requirements. Again, there is no single right way, but there are numerous wrong ways. Only carefully conceived and executed plans will survive the test of time, as well as the ever-increasing demand for higher performance at lower long-term costs.

Options, Design Considerations and Cost
As is often the case, the system designer may offer options that are declined by the client, usually because of concerns over total cost. Reflecting this reality, the example presented here is another example of compromise, but with the end-result remaining the same as the original concept. The designer envisioned terminating all horizontal cabling for voice lines on rack-mounted patch panels and LAN/data lines on patch panels that were inside equipment cabinets.

One reason for proposing this approach for voice terminations is the ease of administering MACs (moves, adds and changes) over the life cycle of the system. MACS would require little more than an appropriate patch cord and accurate record keeping. In addition, it would pre-position every WAO to support LAN/data service if required in the future. All too often, today's voice outlet suddenly becomes tomorrow's data location. And then there are also aesthetics to be considered. A carefully configured rack of panels presents a more structured, neat and orderly appearance than rings or troughs full of cross-connect wire. Reduced long-term maintenance and administration cost savings could easily offset the difference in initial installation costs in a relatively short time, depending on the volume and frequency of MACs.

In this particular example (after much discussion), the client ultimately focused on budgetary concerns and elected to reduce initial costs by using a more familiar configuration for voice services, such as punch down blocks and cross-connect jumpers. There is nothing wrong with taking this approach for exclusively voice systems at the present time. However, it seems obvious that the rack, panel and patch cord concept would provide more future flexibility and offer an embedded redundant infrastructure in the event of any upgrades or technical surprises.

coated with two coats of fire-retardant paint. Terminating blocks and equipment fields are identified by colors that conform with TIA recommendations. Detail drawings should represent exact placement within room(s): width, height, cable pathway and cross-connect routing paths, placement of power receptacles (equipment or convenience) and any/all pertinent construction notes. Indicate the points of the compass on the drawings, with the top of the page as north.

In Room 521, two four-inch conduits are indicated in the northwest corner of the room. One provides a pathway for the telco/LEC from the building entrance facility (EF). The second is also a pathway from the EF, but it is left vacant and capped for future use. The location of the conduits takes advantage of what would typically be unusable space just inside the doorway. Drawings should indicate locations of fire extinguishers, emergency lighting, internal WAOs, reserved (future) equipment wall space or cabinet footprint/dimensions. Additional care should be taken to provide unobstructed free workspace and adequate room for door or panel openings. Include physical properties to be considered, such as overhead ladder racks, tray or conduit routes, suspended cable pathways, lighting fixtures, paging speakers, sprinklers, security cameras and sensors. HVAC requirements and dedicated equipment power outlets should all be distinctively identified on all plans, prior to any work activity being performed.

Detailed drawings are essential and if they are not furnished, there will certainly be varying degrees of penalties that can be traced back to assumptions. Carefully prepared drawings can eliminate, or at least minimize future problems.

Almost everyone has access to a simple drawing program, if not a higher level of CAD or perhaps VISIO, but even a clean hand-drawn copy is better than nothing. Again, no detail is unimportant. It doesn't require any special drafting abilities or formal construction education to prepare a detailed working drawing. As long as the plan is accurately dimensioned and includes all site-specific information, it will serve admirably as a template to build from. Clean as-builts can be prepared at the completion of the project and updated as the need arises.

Some of the most important questions during the conceptual design phase are deceptively simple:

• "Did anything get overlooked?"
• "Will everything fit in the allocated space?"
• "Is the plan clear enough so some-one unfamiliar with the site could interpret how and what must be done to satisfy the intent of the proposal?