2011 NEC Questions and Answers - November 2010 Part 1

NEC Questions and Answers – BASED ON THE 2011NEC
November 2010 – Part 1 of 2

By Mike Holt for EC&M Magazine
Here’s the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent yesterday so you can see how you did.

Q1. What are the field marking requirements for available fault current at electrical service equipment?
A1 Service equipment in other than dwelling units must be legibly field-marked with the maximum available fault current, including the date the fault current calculation was performed and be of sufficient durability to withstand the environment involved [110.24(A)]. Figure 110–13

When modifications to the electrical installation affect the maximum available fault current at the service, the maximum available fault current must be recalculated to ensure the service equipment ratings are sufficient for the maximum available fault current at the line terminals of the equipment. The required field marking(s) in 110.24(A) must be adjusted to reflect the new level of maximum available fault current [110.24(B)]..

Exception: Field markings aren’t required for industrial installations where conditions of maintenance and supervision ensure that only qualified persons service the equipment.

Q2 What are the GFCI requirements for dwelling units?
A2 Ground-fault circuit interrupter protection for personnel must be provided as required in 210.8(A) through (C). The Ground-fault circuit-interrupter device must be installed at a readily accessible location. Figure 210–6
GFCI protection is required for all 15A and 20A, 125V receptacles located in dwelling units in the following locations [210.8(A)]:

Author’s Comment: See the definitions of “GFCI” and “Dwelling Unit” in Article 100.

(1) Bathroom Area. GFCI protection is required for all 15A and 20A, 125V receptacles in the bathroom area of a dwelling unit. Figure 210–11
(2) Garages and Accessory Buildings. GFCI protection is required for all 15A and 20A, 125V receptacles in garages, and in grade-level portions of accessory buildings used for storage or work areas of a dwelling unit. Figure 210–12
(3) Outdoors. All 15A and 20A, 125V receptacles located outdoors of dwelling units, including receptacles installed under the eaves of roofs, must be GFCI protected. Figure 210-7

Ex: GFCI protection isn’t required for a receptacle that’s supplied by a branch circuit dedicated to fixed electric snow-melting or deicing or pipeline and vessel heating equipment, if the receptacle isn’t readily accessible and the equipment or receptacle has ground-fault protection of equipment (GFPE) [426.28 and 427.22]. Figure 210-8

(4) Crawl Spaces. All 15A and 20A, 125V receptacles installed in crawl spaces at or below grade of a dwelling unit must be GFCI protected.
(5) Unfinished Basements. GFCI protection is required for all 15A and 20A, 125V receptacles located in the unfinished portion of a basement not intended as a habitable room and limited to storage and work areas. Figure 210–16

Ex: A receptacle supplying only a permanently installed fire alarm or burglar alarm system isn’t required to be GFCI protected [760.41(B) and 760.121(B)].

(6) Kitchen Countertop Surfaces. GFCI protection is required for all 15A and 20A, 125V receptacles that serve countertop surfaces in a dwelling unit. Figure 210–17
(7) Sinks. For other than kitchen sinks, GFCI protection is required for all 15A and 20A, 125V receptacles located within an arc measurement of 6 ft from the outside edge of the sink. Figures 210–9 and 210–10
(8) Boathouses. GFCI protection is required for all 15A and 20A, 125V receptacles located in a dwelling unit boathouse. Figure 210–20

Q3 What are the GFCI requirements for other than dwelling units?
A3 GFCI protection is required for all 15A and 20A, 125V receptacles installed in the following commercial/industrial locations [210.8(B)]:

(1) Bathrooms. All 15A and 20A, 125V receptacles installed in commercial or industrial bathrooms must be GFCI protected. Figure 210–21
(2) Kitchens. All 15A and 20A, 125V receptacles installed in an area with a sink and permanent facilities for food preparation and cooking [Article 100], even those that don’t supply the countertop surface, must be GFCI protected. Figure 210–22
(3) Rooftops. All 15A and 20A, 125V receptacles installed on rooftops must be GFCI protected. Figure 210-11
(4) Outdoors. All 15A and 20A, 125V receptacles installed outdoors must be GFCI protected. Figure 210-12

Ex 1 to (3) and (4): GFCI protection isn’t required for a receptacle that’s supplied by a branch circuit dedicated to fixed electric snow-melting or deicing or pipeline and vessel heating equipment, if the receptacle isn’t readily accessible and the equipment or receptacle has ground-fault protection of equipment (GFPE) [426.28 and 427.22].

(5) Sinks. All 15A and 20A, 125V receptacles installed within 6 ft of the outside edge of a sink must be GFCI protected. Figure 210–13

Ex 1: In industrial laboratories, receptacles used to supply equipment where removal of power would introduce a greater hazard aren’t required to be GFCI protected.

Ex 2: Receptacles located in patient bed locations of general care or critical care areas of health care facilities aren’t required to be GFCI protected.

(6) Indoor wet locations. All 15A and 20A, 125V receptacles installed indoors in wet locations must be GFCI protected.
(7) Locker Rooms. All 15A and 20A, 125V receptacles installed in locker rooms with associated showering facilities must be GFCI protected.
(8) Garages. All 15A and 20A, 125V receptacles installed in garages, service bays, and similar areas where electrical diagnostic equipment, electrical hand tools, or portable lighting equipment are to be used must be GFCI protected. Figure 210–14

Q4 What are the requirements for the installation of arc fault circuit interrupters (AFCIs) for new construction?
A4 The combination AFCI is a circuit breaker that protects downstream branch-circuit wiring as well as cord sets and power-supply cords; an outlet branch circuit AFCI (receptacle) is installed as the first outlet in a branch circuit to protect downstream branch-circuit wiring, cord sets, and power-supply cords.

All 15A or 20A, 120V branch circuits in dwelling units supplying outlets in family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas must be protected by a listed AFCI device of the combination type [210.12(A)]. Figure 210–15

Ex 1: AFCI protection can be of the branch-circuit type located at the first outlet if the circuit conductors are installed in RMC, IMC, EMT, or Type MC or steel armored Type AC cable meeting the requirements of 250.118, and the AFCI device is contained in a metal outlet or junction box.

Ex 2: Where a listed metal or nonmetallic conduit or tubing is encased in not less than 2 in. of concrete for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, an outlet branch-circuit AFCI at the first outlet is permitted to provide protection for the remaining portion of the branch circuit.

Ex 3: AFCI protection can be omitted for an individual branch circuit to a fire alarm system in accordance with 760.41(B) and 760.121(B), if the circuit conductors are installed in RMC, IMC, EMT, or steel sheath Type AC or MC cable that qualifies as an equipment grounding conductor in accordance with 250.118, with metal outlet and junction boxes.

Q5 Are there any AFCI requirements for circuit modifications or additions to existing circuits?
A5 Yes, according to 210.12(B), where the branch-circuit wiring in a dwelling unit is modified, replaced, or extended in any of the areas specified in 210.12(A), the branch circuit must be protected by:
(1) A listed combination AFCI located at the origin of the branch circuit; or
(2) A listed outlet branch circuit AFCI located at the first receptacle outlet of the existing branch circuit.

Q6 Can receptacles installed above the kitchen counter also be used to meet the 6 ft requirements of 210.52(C)?
A6 Not according to newly added Section 210.4(A)(4). Let's look at the requirements for receptacles in a dwelling unit.

A receptacle outlet must be installed in every kitchen, family room, dining room, living room, sunroom, parlor, library, den, bedroom, recreation room, and similar room or area of a dwelling unit in accordance with 210.52(A) (1), (2), and (3): Figure 210–17

(1) Receptacle Placement. A receptacle outlet must be installed so that no point along the floor line of any wall is more than 6 ft, measured horizontally along the floor line, from a receptacle outlet.

Author’s Comment: The purpose of this rule is to ensure that a general-purpose receptacle is conveniently located to reduce the chance that an extension cord will be used.

(2) Definition of Wall Space.
(1) Any space 2 ft or more in width, unbroken along the floor line by doorways and similar openings, fireplaces, and fixed cabinets. Figure 210–18
(2) The space occupied by fixed panels in exterior walls.
(3) The space occupied by fixed room dividers, such as freestanding bar-type counters or guard rails.
(3) Floor Receptacle Outlets. Floor receptacle outlets aren’t counted as the required receptacle wall outlet if they’re located more than 18 in. from the wall. Figure 210–19
(4) Countertop Receptacles. Receptacles installed for countertop surfaces as required by 210.52(C), can’t be used to meet the receptacle requirements for wall space as required by 210.52(A). Figure 210–20

Q7 What are the NEC requirements for the installation of receptacles in a dwelling unit foyer?
A7 Foyers in a dwelling unit that aren’t part of a hallway [210.52(H)] having an area greater than 60 sQft must have a receptacle located on any wall space 3 ft or more in width and unbroken by doorways, floor to ceiling windows, and similar openings [210.52(I)] Figure 210–36

Q8 What is the minimum vertical clearance for overhead service conductors above a roof?
A8 Overhead service conductor spans must maintain the vertical clearances as follows [230.24]:
(A) Above Roofs. A minimum of 8 ft above the surface of a roof for a minimum distance of 3 ft in all directions from the edge of the roof.

Ex 2: If the slope of the roof exceeds 4 in. of vertical rise for every 12 in. of horizontal run, 120/208V or 120/240V overhead service conductor clearances can be reduced to 3 ft over the roof.

Ex 3: If no more than 6 ft of conductors pass over no more than 4 ft of roof, 120/208V or 120/240V overhead service conductor clearances over the roof overhang can be reduced to 18 in. Figure 230–4

Ex 4: The 3 ft vertical clearance for overhead service conductors that extends from the roof doesn’t apply when the point of attachment is on the side of the building below the roof.

Ex 5: If the voltage between conductors doesn’t exceed 300V and the roof area is guarded or isolated, a reduction in clearance to 3 ft is permitted.

Q9 What are the requirements for bonding of service raceways?
A9 According to 250.92(A), the metal parts of service equipment indicated below must be bonded together in accordance with 250.92(B). Figure 250–62
(1) Metal raceways containing, enclosing, or supporting service conductors.
(2) Metal enclosures containing service conductors.

Author’s Comment: Metal raceways or metal enclosures containing feeder and branch-circuit conductors are required to be connected to the circuit equipment grounding conductor in accordance with 250.86. Figure 250–63

(B) Methods of Bonding. Bonding jumpers around reducing washers or oversized, concentric, or eccentric knockouts are required. Standard locknuts are permitted to make a mechanical connection of the raceway(s), but they can’t serve as the bonding means required by this section. Figure 250–64

Electrical continuity at service equipment, service raceways, and service conductor enclosures must be ensured by one of the following methods:
(1) Neutral Conductor. By bonding the metal parts to the service neutral conductor. Figure 250–65
(2) Threaded Fittings. By terminating metal raceways to metal enclosures by threaded hubs on enclosures if made up wrenchtight. Figure 250–67
(3) Threadless Fittings. By terminating metal raceways to metal enclosures by threadless fittings if made up tight. Figure 250–68
(4) Other listed devices, such as bonding-type locknuts, bushings, wedges, or bushings with bonding jumpers.

Q10 Are flexible metal conduit and liquidtight flexible metal conduit allowed to serve as equipment grounding conductors by the NEC?
A10 In order for flexible metal conduit or liquidtight flexible metal conduit to serve as an equipment grounding conductor, the following conditions must be met [250.118]:

Note: The equipment grounding conductor is intended to serve as the effective ground-fault current path. See 250.2.

(5) Listed flexible metal conduit (FMC) where: Figure 250–85
a. The raceway terminates in listed fittings.
b. The circuit conductors are protected by an overcurrent device rated 20A or less.
c.   The combined length of the flexible conduit in the same ground-fault current path doesn’t exceed 6 ft. Figure 250–86
d. If flexibility is required to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor of the wire type must be installed with the circuit conductors in accordance with 250.102(E), and it must be sized according to 250.122, based on the rating of the circuit overcurrent device.

(6) Listed liquidtight flexible metal conduit (LFMC) where:
Figure 250–87
a.    The raceway terminates in listed fittings.
b.    For 3⁄8 in. through ½ in., the circuit conductors are protected by an overcurrent device rated 20A or less.
c.    For ¾ in. through 1¼ in., the circuit conductors are protected by an overcurrent device rated 60A or less.
d.    The combined length of the flexible conduit in the same ground-fault current path doesn’t exceed 6 ft.
e. If flexibility is required to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor of the wire type must be installed with the circuit conductors in accordance with 250.102(E), and it must be sized in accordance with 250.122, based on the rating of the circuit overcurrent device.