In an industrial installation, 5kV rated, multi-conductor, interlocked, armored, tray-rated cables are installed in cable trays as branch-circuit conductors for motors operating at 4,160VAC. What requirement, if any, is there for shielding these individual conductors within the multi-conductor cables?
A) The individual conductors shall have an ozone-resistant insulation, shall be insulated for the proper voltage and shall be shielded
B) Must have minimum insulation rating of 600 volts
C) Must have minimum insulation rating of 173%
D) No requirement
Explanation: Per a 2005 change, 310.6 requires that conductors operating at voltages over 2,400V must be shielded without exception. At 2,400V, nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use if conditions (a), (b), and (c) are met.
This requirement applies to single-conductors of multi-conductor cables or single conductors installed in raceways, cable trays or cable-bus.
Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at firstname.lastname@example.org.