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There’s money to be made, but hidden costs as well
Low-voltage cables and wires are often installed as part of the initial electrical installation for a facility and used to connect communications systems, control wiring, speakers, fire alarms, computers and other limited-power applications to their related equipment. In a remodel or when equipment is being upgraded or added, old cables are usually abandoned and new cable installed. Must these old cables be removed when installing new cables or can the cables be left for future use? Whose responsibility is it to remove the old cables and is it a hidden cost to the job or additional revenue?
Seemingly hidden within various low-voltage articles in the 2002 National Electrical Code (NEC) are definitions and sections of the articles dealing with abandoned cables. Based on the 2002 NEC, abandoned cables must now be removed. This can add a substantial amount of hidden labor to a job where the contractor is not familiar with these clauses in the NEC and has not added this into the overall bid. If the particular job has been competitively bid, the other bidders may or may not have figured this cost into their bid and the added cost to your bid may mean the loss of the job. Either way, an electrical inspector may require all abandoned cables to be removed, even those cables that were abandoned during previous installations, adding hidden costs to the job.
Since the type of termination and the cable use is slightly different for each system, each definition of “abandoned” varies slightly. The abandoned cable definition for Class 2, Class 3 and PLTC cables reads: “Installed Class 2, Class 3 and PLTC cable that is not terminated at equipment and not identified for future use with a tag.” The definition was written to ensure that only cables that are not spare and truly abandoned in place must be removed. At first glance, the simple answer may be to label all cables for future use but this also requires extra labor that may not have been figured into the job. However, the responsible contractor will understand the reason for the cable removal and will remove any excess cable.
Within the application portion of each article for low-voltage and communications cables is a sentence stating that abandoned cables shall not be permitted to remain. Based on the definition of abandoned cable, any cable that is not tagged or labeled for future use and not terminated at the equipment must be removed. A close examination of this definition indicates that the cable must be terminated at the equipment and identified for future use with a tag or a label; however, the intent was to permit either termination at the equipment or tagging of the cable to identify the cable for future use. Check with the design engineer or the electrical inspector for the installation for a clarification on this issue and what will be required for your particular installation.
Even though most cables installed in a facility are limited-smoke or low smoke-producing fire-resistant cable, the proliferation and expanded use of computers, sound systems, fire alarms, telephones and similar applications has resulted in a massive amount of cables in a facility. Cables installed in ducts, plenums, and other spaces for environmental air, as well as those in other areas of the building, are required to comply with certain NFPA and Underwriters Laboratories Inc. standards for low smoke emission and fire resistance.
NFPA 262, the Standard Method of Test for Flame Travel and Smoke of Wires and Cables for Use in Air-Handling Spaces, limits the maximum peak optical density of the smoke produced to 0.5 and the maximum average optical density to 0.15. The purpose of the test for the maximum optical density level of smoke is to ensure that, in a fire situation, only a certain of amount of smoke will be produced where cable is installed in an environmental air duct, plenum, or other space.
UL 1581, the Reference Standard for Electrical Wires, Cables, and Flexible Cords provides a method of testing the cables for fire resistance and uses a vertical cable tray with cables installed to test whether a fire in the cables will spread to the top of the cable tray. This test is commonly called the vertical tray flame test and is very effective in determining the fire resistance of the cable.
If large amounts of smoke are produced in these areas, the air movement in the ducts, plenums, or other spaces will cause the smoke to be spread to other areas within the occupancy and may affect the successful and safe evacuation of the building. Responsible removal of abandoned cable will limit the amount of smoke produced in a fire and provide a safer facility. EC
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at [email protected].
About The Author
ODE is a retired lead engineering instructor at Underwriters Laboratories and is owner of Southwest Electrical Training and Consulting. Contact him at 919.949.2576 and [email protected].