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Cabling Considerations for Networks and Telecommunications

The condition and appropriateness of the cabling within a building is almost always an afterthought for owners and tenants alike, according to Tom Wales, a Telcom consultant. This is true despite the growing importance of telecommunications and power systems in buildings. According to Dennis St. Jean, of Graybar Electric, the telecommunications department of this 100-year old electrical supply company has grown to equal the size of the conventional power supply division just in the last ten years.

Yet building owners pay relatively little attention to these systems when purchasing a building, assuming it is the tenant who will be responsible anyway. And most tenants don’t yet have the sophistication to anticipate their cabling needs before signing a lease. These systems are analagous to the circulatory and nervous systems of the human body. Without them, the building dies. When connections fail, the building deteriorates, a condition that might be compared to senility.

Types of cable

Three types of cable predominate. Copper wire is the most common. The old CAT 1 cable that we are all familiar with, used for phone lines, has been replaced with faster and faster unshielded twisted pair (UTP) cable. This cable also replaced coaxial cable in most workplaces. Today, however, fiber optic cable is the preferred choice for speed, space, and security. Wireless connections are becoming more common between computers and their hosts, but the communications backbone is still cable.

Some of the old issues regarding safety and durability remain concerns with fiber optic cables as well. Because they are glass, many assume that they are not susceptible to lightning strikes. But because they often have a metal central member, fiber optic cables may be as susceptible as any other cable. Surprisingly, fiber optic cable also deteriorates when wet. As a result, where the cable enters the building and how it is protected is an important consideration.

What does a PCA cover?

Most companies, as part of their due diligence, will order a Property Condition Assessment (PCA) before they purchase a building. Cabling systems, however, are not normally covered by engineering firms conducting such assessments. These systems are also excluded from ASTM Standard 2018-99 that covers most PCAs.

It is not realistic to assess telecommunications systems as part of a PCA, partly because technology changes so fast. New technologies like Power Line Communication (PLC) may make old cabling systems obsolete.

In a standard PCA, there are some covered areas, however, that may be helpful in evaluating these systems. Most office buildings of any size will have a room (or closet) dedicated to telecommunications equipment and electrical switchgear. Some larger buildings in fact may have one such room on each floor. The condition of those rooms is an important indication of the condition of the systems.

  • Is the space conditioned? We have found examples of such rooms that are not part of the conditioned space. Exposure to extremes of heat, cold, and moisture take their toll on such systems.
  • Is the space clean and orderly? Very often, this space is used as additional storage space. Boxes, spare furniture, even trash often block access. That is a good sign that the systems have not been maintained.
  • Are there service contracts? Buildings large enough for a separate room for switchgear and telcom equipment should also have contracts to maintain that equipment. Are contracts in place and what is the service history?

Problems with cabling

Telecommunications cabling has special considerations.

  • Has the cable been stretched? Cables are rated with tensile strength less than most electrical cables. Electricians used to pulling cable through conduit and chases may apply too much pressure which, in turn, causes a degradation in cable performance.
  • Has the cable been bent? Telcom cable, especially fiber optic cable, have limits on the bending radius that may be used. Fiber optic cables may not be bent in diameters less than 40X the diameter of the cable itself. Overbending causes degradation as well.
  • Is the cable near devices that cause electro-magnetic inteference? These include copiers, monitors, power supplies, UPS units, electric heaters, printers, TVs, fluorescent lights, power cables, transformers, compressors, microwaves, etc.
  • Is the cable properly shielded? Telecommunications cable should not be run in the same conduit as power cables.
  • Does the cable have the correct fire rating? Cables run in plenums (ceilings or under floors) must be of the Communications Plenum (CMP) type, not the less expensive riser cable (CMR).
  • Is it hung correctly? Plastic hangers and cable ties should be used. The cable ties should be snug without being overtightened. 

What should a buyer/owner look for?

The buyer of an existing building may want to know what type of cabling is installed. If possible, both the buyer and tenant will want to avoid running new cable. Since most transmission losses occur at the connections or as a result of devices, these can generally be upgraded without replacing the cable.

Buyers and owners should investigate when the cable was installed and when it was last upgraded. If you cannot read the cable type from the jacket, tracing with pencil and paper (similar to grave rubbings) may reveal the type of cable installed. It is also important to know where the service entrance is (aerial or ground) and whether there is room to pull more cable. Another consideration is the redundancy in the system. If one floor goes out, does the whole building go out.

What does a tenant want to know?

Tenants are also concerned with the cabling in place. If fiber optic cable has been installed, they are way ahead of the game. However, most buildings still have copper wire. The current state of the art is referred to as CAT 5, 5e, or 6. These categories refer to the speed of data transmission, with CAT 5 rated for 100Mbps, and CAT 5e and 6 rated for 1000Mbps. CAT 3, rated for 10Mbps, is still serviceable, however, since most computing equipment except for the very fastest systems, can use this adequately.

How does one evaluate telcom and network cable?

Many of the above-referenced conditions can be evaluated by eye. But the true test of cabling is not what it looks like, but how it performs. Quality cable, properly installed, should be capable of transmitting data at 10 Mbps to 100 Mbps (million bits per second). .

Tools are now available to measure this throughput. In fact, the best installers will actually guarantee throughput for the life of the system. Obtaining such guarantees is one way to improve the marketability of the space.

 Who can help? 

With the industry changing so rapidly, it is possible to hire consultants to help you evaluate your communications systems. These can be found in the phone book or through equipment suppliers. Your local phone utility company representative is often an excellent place to start. The web site may also be useful. Criterium Engineers can also help coordinate this service as part of our total building evaluation services.

Volume 14, Number 1

February 2003

Copyright © 2003

The Engineering Advisor is intended to enhance your knowledge of technical issues relating to buildings.  For additional information on any subject, please feel free to call us.  Our commitment is to provide you with timely, accurate information.