All questions and answers are based on the 2005 NEC.
Q. Is GFCI protection required for a single-phase, 208V, 30A coffee maker receptacle in a commercial kitchen?
A. No, only 15A and 20A, 125V receptacles installed in commercial kitchens (Fig. 1) need to be GFCI protected [210.8(B)(2)].
Q. Can a GFCI-type receptacle be installed on an AFCI-protected circuit?
A. Sure. As a matter of fact, some manufacturers have listed circuit breakers that incorporate both GFCI and AFCI protection.
Q. Can copper wire be used to secure EMT in a metal stud wall?
A. This is really up to the authority having jurisdiction (AHJ). Electrical metallic tubing must be securely fastened within 3 feet of every box, cabinet, or termination fitting, and at intervals not exceeding 10 feet [358.30]. The NEC doesn't spellout specifically how the support is to be done, but all installations must be “approved” by the AHJ [90.4].
Q. What are the NEC rules for splicing copper and aluminum conductors to each other?
A. Copper and aluminum conductors must not make contact with each other, except within a device that is listed and identified for this purpose [110.14].
Q. Am I required to “pigtail” conductors at receptacles and switches, or can the screws (one on a terminal) provided on the devices be used to maintain the circuit continuity?
A. Conductor pigtailing is generally not required, but the continuity of the grounded (neutral) conductor of a multi-wire branch circuit must not be interrupted by the removal of a wiring device. Therefore, the grounded (neutral) conductors of multi-wire branch circuits must be spliced together, and a pigtail must be provided for the wiring device [300.13(B)].
Q. Can I use MC cable for luminaires located at 8 feet above a patient care area?
A. Branch circuits that serve patient care areas must be installed in a metal raceway or listed cable with a metallic armor or sheath that qualifies as an effective ground-fault current path in accordance with 250.118.
Typically, the outer metal sheath of interlocked Type MC cable isn't listed as a suitable ground-fault current path [250.118(10]). Therefore, it is not permitted to supply branch circuits in patient care areas of health care facilities [517.13(A)].
However, the metal armored sheath of Type AC cable is listed as a suitable ground-fault current path (it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)]) and can be used to wire the luminaires located in the patient care area [517.13(A)].
Note: Exception No. 2 of 517.13(B) exempts the redundant equipment grounding (bonding) conductor; it does not exempt the type of 517.13(A) required wiring method in a patient care area. Patient care areas include patient rooms as well as examining rooms, therapy areas, examining and treatment rooms, recreational areas, and some patient corridors (see 517.2 Patient Care Areas).
Q. Can I gang three extension rings on to each other?
A. Yes. According to the UL listing requirement, extension rings are listed as a Metallic Outlet Box (QCIT), and this standard allows one or more extensions to be used [110.3(B)].
Q. Do I have to identify GFCI-protected receptacles with the “GFCI-protected” stickers that come with the devices?
A. Yes, if the instructions supplied with GFCI-protected receptacle state that the enclosed “GFCI-protected” labels be placed on all GFCI-protected receptacles [110.3(B)].
Q. When GFCI protection is required by the NEC for receptacles, must I use receptacles of the GFCI type, or can I protect the receptacles on the circuit with a GFCI circuit breaker?
A. A GFCI-type receptacle or a GFCI circuit breaker can be used to provide the protection required by the NEC.
Q. If an outdoor hot tub has integral GFCI protection, do I still need to provide GFCI for the equipment?
A. Additional GFCI protection isn't required for a listed self-contained spa or hot tub unit or listed packaged spa or hot tub assembly marked to indicate that integral GFCI protection has been provided for all electrical parts within the unit or assembly [680.44(A)].
Q. What is the minimum distance a receptacle must be located away from a sink?
A. The NEC doesn't specify a minimum distance that a receptacle must be located from a sink.
Q. What is the minimum distance a dry-type transformer must be installed from an inside wall?
A. Transformers rated 112.kVA or less must be located at least 12 inches from combustible materials, unless separated by a heat and fire-resistant barrier [450.21(A)]. Transformers with ventilating openings must be installed so that ventilation is adequate to dispose of the transformer full-load losses without creating a temperature rise that is in excess of the transformer rating [450.9].
As always, be sure to comply with the Listing requirements [110.3(B)] for your particular installation. This typically calls for 6 inches of clearance.
Q. Is a service disconnecting means required to be installed on the outside of a building?
A. This is really a judgment call that has to be made by the AHJ. The service disconnecting means must be placed at a readily accessible location either outside the building or structure, or inside nearest the point of service conductor entry [230.70(A)(1)].
Check with the AHJ on what “nearest the point of entry” means — to some it means a back-to-back installation; others permit up to 10 feet of service conductor within the building.