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NEC Questions and Answers – Based on the 2011 NEC
July 2012
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, so you can see how you did.
Q1. What are the NEC requirements for sizing receptacles?
A1. A single receptacle on an individual branch circuit must have an ampacity not less than the rating of the overcurrent device [210.21(B)(1)].
Note: A single receptacle has only one contact device on its yoke [Article 100]; this means a duplex receptacle is considered as two receptacles.
If a receptacle is connected to a branch circuit that supplies two or more receptacles, the total cord-and-plug-connected load must not exceed 80 percent of the receptacle rating [210.21(B)(2)].
Author’s Comment: A duplex receptacle has two contact devices on the same yoke [Article 100]. This means even one duplex receptacle on a circuit makes that circuit a multioutlet branch circuit.
According to 210.21(B)(3), if the receptacle is connected to a branch circuit that supplies two or more receptacles, the receptacles must have an ampere rating in accordance with the values listed in Table 210.21(B)(3).
Q2. What is the Code limitation for sizing circuits that supply cord-and-plug connected equipment?
A2. Cord-and-plug-connected equipment not fastened in place, such as a drill press or table saw, must not have an ampere rating more than 80 percent of the branch-circuit rating [210.23(A)(1)].
Author’s Comment: UL and other testing laboratories list portable equipment (such as hair dryers) up to 100 percent of the circuit rating. The NEC is an installation standard, not a product standard, so it can’t prohibit this practice. There really is no way to limit the load to 80 percent of the branch-circuit rating if testing laboratories permit equipment to be listed for 100 percent of the circuit rating.
Equipment fastened in place (other than luminaires) must not be rated more than 50 percent of the branch-circuit ampere rating if this circuit supplies luminaires, receptacles, or both [210.23(A)(2)].
Question: Can a whole house (central) vacuum motor rated 13A be installed on an existing 20A circuit that supplies more than one receptacle outlet?
Answer: No, an individual 15A or 20A branch circuit will be required.
Q3. What are the Code requirements for placing receptacles on “wall space” in dwelling units?
A3. 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 in accordance with (1), (2), and (3) [210.52(A)]:
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 [210.52(A)(1)]
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.
Definition of Wall Space [210.52(A)(2)].
- Any space 2 ft or more in width, unbroken along the floor line by doorways and similar openings, fireplaces, and fixed cabinets.
- The space occupied by fixed panels in exterior walls.
- The space occupied by fixed room dividers, such as freestanding bar-type counters or guard rails.
A new requirement added in 210.52(A)(4) specifies that 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).
Q4. What are the Code rules about using floor receptacles to meet the receptacle wall outlet requirements in a dwelling wall space?
A4. Floor receptacle outlets aren’t counted as the required receptacle wall outlet if they’re located more than 18 in. from the wall [210.52(A)(3)].
Q5. What are the NEC rules on placing receptacles for counter tops in a dwelling unit kitchen?
A5.A receptacle outlet must be installed for each kitchen and dining area countertop wall space 1 ft or wider, and receptacles must be placed so that no point along the countertop wall space is more than 2 ft, measured horizontally, from a receptacle outlet [210.52(C)(1)].
Ex: A receptacle outlet isn’t required on a wall directly behind a range, counter-mounted cooking unit, or sink, in accordance with Figure 210.52(C)(1) in the NEC.
Author’s Comment: If the countertop space behind a range or sink is larger than the dimensions noted in Figure 210.52(C)(1) of the NEC, then a GFCI-protected receptacle must be installed in that space. This is because, for all practical purposes, if there’s sufficient space for an appliance, an appliance will be placed there.
At least one receptacle outlet must be installed at each island countertop space with a long dimension of 2 ft or more, and a short dimension of 1 ft or more [210.52(C)(2)].
At least one receptacle outlet must be installed at each peninsular countertop with a long dimension of 2 ft or more, and a short dimension of 1 ft or more, measured from the connecting edge [210.52(C)(3)].
Author’s Comment: The Code doesn’t require more than one receptacle outlet in an island or peninsular countertop space, regardless of the length of the countertop, unless the countertop is broken as described in 210.52(C)(4).
When breaks occur in countertop spaces for rangetops, refrigerators, or sinks, each countertop space is considered as a separate countertop for determining receptacle placement [210.52(C)(4)].
If a range, counter-mounted cooking unit, or sink is installed in an island or peninsular countertop, and the depth of the counter behind the range, counter-mounted cooking unit, or sink is less than 12 in., the countertop space is considered to be two separate countertop spaces.
Author’s Comment: GFCI protection is required for all 15A and 20A, 125V receptacles that supply kitchen countertop surfaces [210.8(A)(6)].
Receptacle outlets required by 210.52(C)(1) for the countertop space must be located on or above, but not more than 20 in. above, the countertop surface. Receptacle outlet assemblies listed for the application can be installed in countertops [210.52(C)(5)].
Note: Receptacles must not be installed in a face-up position in countertops or similar work surface areas in a dwelling unit [406.5(E)].
Ex: The receptacle outlet for the countertop space can be installed below the countertop only for construction for the physically impaired or when wall space or a backsplash isn’t available, such as in an island or peninsular counter. Under these conditions, the required receptacle(s) must be located no more than 1 ft below the countertop surface and no more than 6 in. from the countertop edge, measured horizontally.
Receptacle outlets rendered not readily accessible by appliances fastened in place, located in an appliance garage, behind sinks, or rangetops [210.52(C)(1) Ex], or supplying appliances that occupy dedicated space don’t count as the required countertop receptacles.
Author’s Comment: An “appliance garage” is an enclosed area on the countertop where an appliance can be stored and hidden from view when not in use. If a receptacle is installed inside an appliance garage, it doesn’t count as a required countertop receptacle outlet.
Q6. When is ground fault protection of equipment required for feeder circuits?
Each feeder disconnecting means rated 1,000A or more supplied by a 4-wire, three-phase, 277/480V wye-connected system must be provided with ground-fault protection of equipment in accordance with 230.95 and 240.13 [215.10].
Author’s Comment: See the definition of “Ground-Fault Protection of Equipment” in Article 100.
Ex 2. Equipment ground-fault protection isn’t required if ground-fault protection of equipment is provided on the supply side of the feeder and on the load side of the transformer supplying the feeder.
Author’s Comment: Ground-fault protection of equipment isn’t permitted for fire pumps [695.6(H)], and it’s not required for emergency systems [700.26] or legally required standby systems [701.17].
Q7. What are the NEC rules for the identification of circuit conductors?
A7. Grounded (neutral) conductors 6 AWG and smaller must be identified by one of the following means [200.6(A)]:
(1) By a continuous white outer finish.
(2) By a continuous gray outer finish.
(3) By three continuous white stripes along its entire length on other than green insulation.
(4) Wires that have their outer covering finished to show a white or gray color but have colored tracer threads in the braid identifying the source of manufacture are considered to meet the provisions of this section.
Author’s Comment: The use of white tape, paint, or other methods of identification isn’t permitted for grounded conductors 6 AWG or smaller.
(6) A single-conductor, sunlight-resistant, outdoor-rated cable used as the grounded conductor in photovoltaic power systems as permitted by 690.31(B) can be identified by distinctive white marking at all terminations.
Grounded (neutral) conductors 4 AWG or larger must be identified by one of the following means [200.6(B)]:
(1) A continuous white outer finish along its entire length.
(2) A continuous gray outer finish along its entire length.
(3) Three continuous white stripes along its length.
(4) White or gray tape or markings at the terminations.
If grounded conductors of different voltage systems are installed in the same raceway, cable, or enclosure, each system grounded conductor must be identified by [200.6(D)]:
(1) A continuous white or gray outer finish along its entire length.
(2) The grounded conductor of the other system must have a different outer covering of continuous white or gray outer finish along its entire length or by an outer covering of white or gray with a readily distinguishable color stripe (other than green) along its entire length.
(3) Other identification allowed by 200.6(A) or (B) that distinguishes the grounded conductor from other systems.
200.7 Use of White or Gray Color.
A conductor with white insulation can only be used for the ungrounded conductor in circuits of 50V or more as follows [200.6(C)]:
(1) Cable Assembly. The white conductor within a cable can be used for the ungrounded conductor, if permanently reidentified by marking tape, painting, or other effective means at each location where the conductor is visible to indicate its use as an ungrounded conductor. Identification must encircle the insulation and must be a color other than white, gray, or green.
The white conductor within a cable can be used to supply power to single-pole, 3-way, and 4-way switch loops, as well as travelers for 3-way and 4-way switching if permanently reidentified at each location where the conductor is visible to indicate its use as an ungrounded conductor.
(2) Flexible Cord. The white conductor within a flexible cord can be used for the ungrounded conductor for connecting an appliance or equipment as permitted by 400.7.
Note: Care should be taken when working on existing systems because a gray insulated conductor may have been used in the past as an ungrounded conductor.
Author’s Comment: The NEC doesn’t permit the use of white or gray conductor insulation for ungrounded conductors in a raceway, even if the conductors are permanently reidentified.
Equipment grounding conductors can be bare, covered, or insulated. Insulated equipment grounding conductors size 6 AWG and smaller must have a continuous outer finish either green or green with one or more yellow stripes [210.5(B), 250.119].
On equipment grounding conductors 4 AWG and larger, insulation can be permanently reidentified with green marking at the time of installation at every point where the conductor is accessible [250.119(A)].
Ungrounded conductors must be identified as follows [210.5(C)]:
- If the premises wiring system contains branch circuits supplied from more than one voltage system, each ungrounded conductor must be identified by phase and system at all termination, connection, and splice points.
- Identification can be by color coding, marking tape, tagging, or other means approved by the authority having jurisdiction.
- The method of identification must be documented in a manner that’s readily available or permanently posted at each branch-circuit panelboard.
Author’s Comments:
- When a premises has more than one voltage system supplying branch circuits, the ungrounded conductors must be identified by phase and system. This can be done by permanently posting an identification legend that describes the method used, such as color-coded marking tape or color-coded insulation.
- Conductors with insulation that’s green or green with one or more yellow stripes can’t be used for an ungrounded or neutral conductor [250.119].
- Although the NEC doesn’t require a specific color code for ungrounded conductors, electricians often use the following color system for power and lighting conductor identification:
– 120/240V, single-phase—black, red, and white
– 120/208V, three-phase—black, red, blue, and white
– 120/240V, three-phase—black, orange, blue, and white
– 277/480V, three-phase—brown, orange, yellow, and gray; or, brown, purple, yellow, and gray
Q8. When are overcurrent devices restricted from being installed?
A8. • Overcurrent devices must not be exposed to physical damage [240.24(C)].
Note: Electrical equipment must be suitable for the environment, and consideration must be given to the presence of corrosive gases, fumes, vapors, liquids, or chemicals that have a deteriorating effect on conductors or equipment [110.11].
• Overcurrent devices must not be located near easily ignitible material, such as in clothes closets [240.24(D)].
• Overcurrent devices aren’t permitted to be located in the bathrooms of dwelling units, dormitories, or guest rooms or guest suites of hotels or motels [240.24(E)].
Author’s Comment: The service disconnecting means must not be located in a bathroom, even in commercial or industrial facilities [230.70(A)(2)].
• Overcurrent devices must not be located over the steps of a stairway [240.24(FC)].
Author’s Comment: Clearly, it’s difficult for electricians to safely work on electrical equipment that’s located on uneven surfaces such as over stairways.
Q9. What is the Code rule regarding wiring under roof decking?
A9. Cables, raceways, and enclosures under metal-corrugated sheet roof decking must not be located within 1½ in. of the roof decking, measured from the lowest surface of the roof decking to the top of the cable, raceway, or box. In addition, cables, raceways, and enclosures aren’t permitted in concealed locations of metal-corrugated sheet decking type roofing [300.4(E)].
Note: Roof decking material will be installed or replaced after the initial raceway or cabling which may be penetrated by the screws or other mechanical devices designed to provide “hold down” strength of the waterproof membrane or roof insulating material.
Ex: Spacing from roof decking doesn’t apply to rigid metal conduit and intermediate metal conduit.
For more NEC Practice purchase Mike Holt's NEC Practice Questions book, Based on the 2011 NEC.
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