Stumped by the Code?

Aug 14, 2008 4:25 PM, By Mike Holt, NEC Consultant

Q. What are the NEC requirements when using Type MC or NM cable as the feed and switchleg for a singlepole switch?

A. The white conductor within the cable must be used to supply the power to the switch, and it must be permanently reidentified at each location where the conductor is visible to indicate its use as an ungrounded conductor [200.7(C)(2)]. The black conductor is to be used as the switch leg to the luminaire.

Q. What are the rules for terminating more than one conductor on a terminal?

A. The general requirement is that all terminals are rated for the termination of only one conductor. Terminals suitable for more than one conductor must be identified for this purpose, either within the equipment instructions or on the terminal itself [110.14(A)]. Some circuit breakers that are rated 30A or less are listed for the termination of two conductors, and this information is contained in the product instructions.

Q. What are working space requirements for telecommunications equipment?

A. The working space requirement for power equipment contained in 110.26(A) does not apply to communications equipment [90.3]; however, the telecommunications equipment cannot be located in the required workspace for power equipment.

Q. Can a receptacle for a LCD projector that is cordandplugconnected be located above a suspended ceiling?

A. No. Cords are not permitted to be run through holes in structural or suspended/dropped ceilings [400.8(2)]. They are also not allowed to be concealed by walls, floors, or ceilings, or located above suspended or dropped ceilings [400.8(5)].

Q. What are the cable fill limitations when installing telecom cable in a raceway?

A. Where communications cables are installed in a Chapter 3 raceway, the raceway must be installed in accordance with Chapter 3. The raceway fill requirements of Chapter 3 and Chapter 9 do not apply [800.110].

Q. Is a disconnect required to be within sight of electric spaceheating equipment if the unit has a factoryinstalled circuit breaker?

A. No. A unit switch with a marked “off” position that is an integral part of the equipment can serve as the heater disconnecting means, if it disconnects all ungrounded conductors of the circuit [424.19(C)].