Installation standards are a baseline performance level, not the ultimate achievement.
Mark Armstrong / Kent Datacomm
In the day-to-day installation of structured cabling systems, industry standards do not always cover a specific aspect of the work to be performed. In these cases, a cabling contractor is required to make some very important decisions about how best to address the specific installation issues in question. Those decisions are generally based on performance requirements, aesthetics, manufacturers' recommendations, the customer's needs, and costs that may be saved or incurred. An informed cabling contractor will use this knowledge to provide a solution that best meets the needs of the customer.
The ability to respond with a positive solution requires that the cabling contractor consider the standards as they are written today and know what is being proposed for the future. Knowledge of general construction practices and local and national codes, as well as good common sense, is also required. The real world of construction requires a well-informed project-management team that can make these important decisions daily-even hourly.
A data center on a raised floor allows the user to implement an underfloor cable-routing system, such as the one shown here.
Even though today's standards may not cover every detail required to complete a project, they have definitely improved the quality of work that has been performed in recent years. Before the cabling industry and its customers were aware of these standards, the quality and craftsmanship in cabling suffered. These were the days when cable routing of getting from Point A to Point B meant that the cable was usually laying on the ceiling tiles and fluorescent lights or tie-wrapped to an electrical conduit or sprinkler system in the ceiling. It was not unusual to see cables spliced in the ceiling and going off in several different directions. The wiring closets were usually janitor storage rooms or walls within break rooms. Cables would be lying on the floor, draped across furniture, stapled to the wall, or hanging across a room like a clothesline. Systems were installed in dirty, dusty, musty, wet, dark rooms that were usually more than 100°F in the summer and below freezing in the winter.
From darkness to enlightenment
Those were the dark days of cabling, when there was little training, and installation speed was more important than the quality of the work. Data networks were in their infancy and divestiture of the telephone industry had created opportunity for those with little or no experience in telephony, much less cabling. Cabling was not even considered a discipline of its own. Quality was not part of the cabler's vocabulary because there were no standards for measurement. As long as the device being installed worked, it made no difference how it was cabled.
But those who know and understand the standards and consider cabling to be a craft appreciate that it is no simple task to install a cable that will be used for today's high-demand networks. A voice transmission can be made across two strands of barbed wire, but barbed wire is not recognized as an acceptable medium in the standards. The knowledge and acceptance of the standards have changed the cabling industry to a respectable, as well as required, engineered discipline.
Now that the standards have been embraced by the cabling industry, they must still be closely examined, interpreted, enhanced, and considered how best to execute. Bringing an existing facility up to current standards is not always easy or cost-effective. In these cases, performance is usually the driving force behind the decisions made by the customer based on network requirements. New construction does offer the opportunity to build the networks and supporting structures to standards. Even in new construction, the cabling contractor still must rely on the construction engineers to have a specific knowledge of cabling requirements and standards. Cabling customers are becoming more sophisticated in their knowledge of these requirements, and there is some positive change in the designs that are being released for construction.
It must be understood that standards are just standards, not codes. Codes must be met or exceeded in all cases, but there is also room for improvement in the specifications published in today's codes. Cabling contractors should do their best to meet or exceed the standards and codes, but decisions must be made outside of those parameters. With that in mind, following are some examples of decisions made in cases where published independent standards or codes do not exist. The lessons learned on these projects may help you the next time you must make a difficult on-the-job decision.
A public school campus has eight buildings within a city block that must be networked with a fiber backbone. The school district has designated the library-one of the eight buildings-as the data center. The high school building was about a mile down the road from the library. Wireless media were considered, but ultimately the district decided to use fiber for the interbuilding connectivity. An easement agreement with the local electrical provider allowed the school district to attach its fiber to an existing pole line.
The amount of electronics in some of today's installations, particularly at Internet service providers, requires more planning for the layout and administration of cabinets, racks, and other equipment.
Specifications called for 24 strands of multimode fiber and 12 strands of singlemode fiber to run from each building to the data center. The school district had separately contracted the installation of buried conduit to facilitate the outdoor-rated fiber. The original scope of work specified that the fiber be terminated in wall-mounted fiber enclosures.
After the work was underway, the school district made the decision to buy and install wall-mounted cabinets for security reasons since some of the terminations were in classrooms. The cabinets had locks installed to keep students from accessing the network hardware that was required in these cabinets. The cabinets were hinged so that the outer enclosure would swing open for access to the front of the 19-inch rack, and the 19-inch rack would also swing open for access to the back of the 19-inch rack. This arrangement makes for easy access from the front or back by a technician, but creates an issue of movement of the terminated cables.
There is no standard that addresses how to enter, attach, or manage copper or fiber cable in this situation. The manufacturer of the cabinet and the manufacturer of the fiber cable were consulted on this issue; neither had standards, but both suggested solutions. Everyone agreed that entry and attachment should be made at the hinged side of the cabinet, then a second attachment to the rack-mounted fiber enclosure. There was a difference of opinion as to whether the outer sheath of the fiber should be stripped back to the first attachment or second one. The fiber-cable manufacturer agreed that either way would satisfy its requirements. The school district decided to have the outer sheath in place up to the fiber enclosure.
Regardless of where the attachments were made, there will still be movement of terminated fiber every time that 19-inch rack swings open. One other issue concerned how to attach the multiple outdoor fiber cables to a single fiber enclosure. The manufacturer had established standard practices on how to attach one cable but not multiple cables. The school district decided to attach the first cable according to the manufacturer's standards, then simply tie-wrap the remaining cables to the first one. The fiber was also in innerduct and there were no recommendations from any of the manufacturers as to where or how to terminate the innerduct. That decision was left to the cabling contractor. In this case, the contractor decided to terminate the innerduct and attach the innerduct, at its point of entry, to the cabinet.
Industry education works overtime
A utility management group had four buildings in a campus environment with a fiber backbone that had 2,500 users. The project scope called for all 2,500 workstations to be cabled with gigabit-speed-ready copper cabling. Because the project was being carried out in an existing facility, the cabling crew had to do its work after-hours. Working at night is nothing new to cabling installers, but when issues pop up that require involvement of other entities, the logistical challenge of getting all involved parties together can be significant.
At the time, no standards existed for testing the copper cable to meet the customer's gigabit-speed performance requirement. The cable manufacturer stood behind its own test results-in the lab and in the field-that the cable would perform to the customer's requirements. The test-equipment manufacturer, specified by the customer, had the ability to test to the customer's requirements. But again, at that time there were no official standards addressing the customer's requirements.
This was another good example of where technology was in place before the standards were published. It happens quite often. All parties involved believed they knew what the standards would be and, in fact, they were correct. Technology will always be ahead of the standards, and that is why it is important a cabling contractor stays informed of any new technological developments. Education and training are essential and mandatory for a successful cabling business.
Inside an ISP
An Internet service provider (ISP) wanted to cable a customer collocation data center. Walls secured the ISP's network area from the customer's collocation cabinets. The original scope of work called for a fiber backbone from the ISP's network to the end of each row of 20 customer cabinets, then copper distribution from that point to each cabinet. When it was determined that copper could be placed from the ISP's network to all the cabinets and stay within distance standards, the fiber was eliminated.
The entire data center was on a raised floor. Separate underfloor raceway was installed for high- and low-voltage cables. Then, 16-port patch panels were installed in the cabinets with six 4-pair copper cables terminated. This arrangement turned out to be a highly concentrated number of copper cables in a fairly small area, necessitating a large number of patch panels in the ISP's network area. As it turns out, a fiber backbone was required in the ISP's network area because of the distances required for patching to the various networks, which were located in eight rows of seven equipment racks.
Interestingly, the structured cabling standards that apply to cabling a cabinet are the same standards that apply to cabling workstations or desktops. The grounding and bonding design became an issue because standards and codes vary from site to site. Codes are not specific to this design, and interpretation of what is published is always fodder for debate. There should be a consideration for life, health, and property. Those three reasons should be enough for further development of these codes and standards.
Each of the cables shown here required an extra twist-provided manually in the field-to one of its conductor pairs so the user could be eligible for the manufacturer's extended warranty.
In this installation, the consultant representing the owner decided that a number 6 ground to the end of each row of 20 cabinets, and bonding the cabinets to each other with a number 6 strap, would meet local code. Here is another example of why one person's interpretation should be clearly specified in a published code or standard. The cabling contractor has a very difficult task of estimating grounding-requirement costs when there are differing opinions and no documentation to support any solution. In the past, grounding applied to only a few racks and cabinets here and there. In today's market, an installation can easily include more than 500 racks and cabinets in a single data center.
A new county justice center required connectivity on 17 floors. It was a typical structured cabling system, with a fiber backbone from the data center to each floor and copper cable to the desktop. The fiber backbone included singlemode and multimode fiber, in line with the recent trend toward singlemode in campus and even building backbones.
In this project, "desktop" had multiple meanings, which challenged the installation. Judges' chambers, judges' benches, prisoners' holding cells, jury-deliberation rooms, and other secured areas all were considered "desktops," and all required cabling. Routing around the thick concrete walls required interesting and creative approaches. Because the county required that the project be certified to the cabling manufacturer's extended warranty, the manufacturer's representative had to inspect and approve the installation.
With work still in progress, the manufacturer's representative made a routine inspection. While on the site, he instructed a cabling technician to add a twist to one of the copper cable's four pairs before terminating the cable to the jack or patch panel. The manufacturer's research showed that this additional twist improved system performance. And even though industry-standard installation practices do not require installers to manually add a twist to a copper pair, the manufacturer did require such twisting for system certification.
This is an example of the manufacturer going a step beyond industry-standard practices in an effort to improve the performance of copper terminations. This is also an excellent issue for installers to bring up with manufacturers because of the high percentage of failures in copper-system terminations.
Standards a good starting point
There are many examples of work that really must be performed in a cabling project but are not covered by industry standards. Routing the last 10 ft of any cabling into a wiring closet is a decision that is made with very little support or guidance from the standards. Those final 10 ft are usually 90% of what your customer will see, and their perception of your craftsmanship is frequently judged solely by this part of the project. This portion of the work usually is a good indicator of the entire project's quality, so it is important that we institute standards that more specifically address cable routing and attachment in these crucial areas.
A quality-conscious cabling contractor will take the time to route and comb cables in organized and manageable bundles, taking into consideration the specifics of each job. There are varying opinions as to how these bundles should be routed to their termination points, and each argument has its merits. But for what is considered a critical portion of the cabling installer's work, there must be more specific standards for our industry.
In no way do I intend this information to be a negative opinion of existing standards. The standards in place today have very much changed our industry for the better. Cabling has emerged from being an afterthought to being a thriving, growing industry with ample opportunity for many individuals and companies. The standards have also given the industry a template for training technicians who are faced with installation decisions daily.
The standards are a great building block that we must continue to support. Standards-based training is available in many forms, and those responsible for high-speed network installations should take advantage of this training. An installer who is trained in standards will be much more productive and cost-effective as an employee. We as an industry must return to the craft of cabling and emphasize pride in the work we perform. The standards are a good place to start.
Mark Armstrong, RCDD, is the Austin, TX-based national services manager for Media Distribution Services, the cabling division of Kent Datacomm. The company develops end-to-end solutions for integrated voice, video, and data networks. He can be reached at e-mail: email@example.com.