Stumped by the Code? Permitted Uses of Cable Trays

All questions and answers are based on the 2017 NEC.

Q. What uses of cable trays are not permitted by the NEC?

A. Cable tray systems aren’t permitted in hoistways or where subject to severe physical damage [Sec. 392.12].

Q. What uses are permitted by the Code for flexible cords and flexible cables?

A. Flexible cords can be used for the following applications [Sec. 400.10(A)]:

(1) Pendants [receptacles [Sec. 210.50(A)] and boxes [Sec. 314.23(H)]].

(2) Wiring of luminaires [Sec. 410.24(A) and Sec. 410.62(B)].

(3) Connection of portable luminaires, portable and mobile signs, or appliances [Sec. 422.16].

(4) Elevator cables.

(5) Wiring of cranes and hoists.

(7) Prevention of the transmission of noise or vibration [Sec. 422.16].

(8) Appliances where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance and repair, and the appliance is intended or identified for flexible cord connections [Sec. 422.16].

(9) Connection of moving parts. Note: Flexible cords are permitted for fixed permanent wiring by Sec. 501.10(A)(2) and (B)(2), Sec. 501.140, Sec. 502.4(A)(1)(e), Sec. 502.4(B)(2), Sec. 503.3(A)(2), Sec. 550.10(B), Sec. 553.7(B), and Sec. 555.13(A)(2).

As outlined in 400.10(B), attachment plugs are required for flexible cords used in any of the following applications:

• Portable luminaires, portable and mobile signs, or appliances [Sec. 400.10(A)(3)].

• Stationary equipment to facilitate its frequent interchange [Sec. 400.10(A)(6) and Sec. 422.16].

•Appliances specifically designed to permit ready removal for maintenance and repair, and identified for flexible cord connection [Sec. 400.10(A)(8)]. Note: An attachment plug can serve as the disconnecting means for stationary appliances [Sec. 422.33] and room air conditioners [Sec. 440.63].

Q. When does the Code require ground-fault protection of equipment on electrical services?

A. Service disconnects and feeder circuits rated 1,000A or more, supplied from a 4-wire, 3-phase, 277/480V wye-connected system must be protected against ground faults in accordance with Sec. 230.95 [Sec. 240.13]. The requirement for ground-fault protection of equipment doesn’t apply to:

(1) Continuous industrial processes where a nonorderly shutdown will introduce additional or increased hazards.

(2) Installations where ground-fault protection of equipment is already provided.

(3) Fire pumps [Sec. 695.6(H)].

Q. What is the GFCI requirement in the Code for electric space-heating cables?

A. GFCI protection for personnel is required for electric space-heating cables that are embedded in concrete or poured masonry floors of bathrooms and kitchens, and hydromassage bathtub locations [Sec. 424.44(E)]. See Sec. 680.27(C)(3) for restrictions on the installation of radiant-heating cables for spas and hot tubs installed outdoors [Sec. 680.40].

Q. What does the NEC require regarding disconnects for duct heaters?

A. The disconnect for the duct heater must be accessible and be installed at or within sight from the controller [Sec. 424.65].

Where the disconnecting means is not within sight of the controller, the disconnecting means must be capable of being locked in the open position [Sec. 424.19(A)].

These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code.