As usual, never consider the following commentary associated with these photos as a formal interpretation of the National Electrical Code (NEC). Without criticizing anyone or any product, the following scenarios present us with serious electrical safety questions.
A metal wireway is a sheet metal trough with a hinged or removable cover used for housing and protecting electric wires and cable. Typically, the conductors are laid in place after the wireway has been installed as a complete system (376.2). The Code doesn't permit you to locate wireways where they're subjected to severe physical damage or severe corrosive environments [376.12(1) and (2)].
This installation was discovered near Baltimore's Inner Harbor in a downtown parking structure. Almost all of the exposed wiring methods located on the ceiling at street level were found in this condition. The local environmental conditions probably caused the corrosion. All materials are required to be suitable for the environment in which they're to be installed. See 300.6 for rules concerning protection against corrosion.
Throughout Chapter 3 of the NEC, a Fine Print Note (FPN) calls attention to 300.4(F), Insulated Fittings. This rule requires the use of insulated fittings when raceways containing ungrounded conductors 4 AWG or larger enter a cabinet, box enclosure, or raceway. A substantial fitting providing a smoothly rounded insulating surface usually provides the protection for the conductors, unless the conductors are separated from the fitting or raceway by substantial insulating material that is securely fastened in place. Conduit bushings constructed wholly of insulating material can't be used to secure a fitting or raceway. The insulating fitting or material must have a temperature rating not less than the insulation temperature rating of the installed conductors. This cabinet violates that rule because the fitting at the bottom right is metal. As a side note, this cabinet was also being used as a storage bin for the spare circuit breakers located in the bottom of the cabinet.
Check Ribbon Installation
The NEC requires the location of underground service conductors not encased in concrete or buried 18 in. or more below grade to be identified with a warning ribbon placed in the trench at least 12 in. above the underground installation. [300.5(D)(3)]. Where the cables are energized at more than 600V, as in this installation, Table 300.50 notes the minimum cover requirements required by the Code.
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