The National Electrical Code (NEC) requires the removal of some, but not all types of abandoned wiring. The mandate is generally applicable to what is commonly called low-voltage wiring, although this term never occurs in the NEC. The requirement is repeated in substantially the same form in various Code articles such as those covering coaxial, fiber optic, telephone, fire alarm and other types of communication cable. Strangely, it has never been extended to cover wiring for power and lighting.
废弃的电线被定义为段d wiring that is not terminated at equipment other than a connector and not identified for future use with a tag. Abandoned wiring that is not accessible needn’t be removed. Accordingly, a group of data conductors that is within conduit or raceway is exempt from the requirement. This makes sense, because if the cabling is so enclosed, there is no danger that it would ignite, or that the product of combustion would be a hazard.
In many commercial facilities, especially office buildings, a succession of tenants with differing requirements may have had generation upon generation of low-voltage wiring installed — under floors, fished behind finish walls, and especially above suspended ceilings. This wiring is energized at low levels or not at all unless power wiring accidentally becomes connected to it through some mishap. Thus there is little chance of its igniting nearby combustible material.
But if fire from an outside source should spread into a large bundle of abandoned cabling, huge amounts of thick, heavy smoke will be the result. Toxic effects aside, the presence of a lot of heavy smoke can displace available oxygen, causing injury or death by affixation. (There are far more fatalities from electrical fire than electrical shock, and smoke inhalation is a more frequent cause of death than burning.)
So there is good reason that abandoned wiring should be removed. But who should bear the expense? Owner, tenant, designer, electrician – any of these individuals may become liable. And abandoned wire removal is exacting and expensive work.
In an operating facility, there is the chance that in-use data cabling could be removed, causing a costly outage. Adjacent cables can be disrupted. Fire alarm cable is sensitive and there is the potential of initiating a false alarm, interrupting the workflow, and giving workers reason to disregard a genuine alarm in the future.
Where data or other low-voltage wiring is to be installed in a commercial or industrial building, decision makers should proceed with caution lest problems from the past should surface, causing unexpected difficulties.
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