Article 110 Requirements for Electrical Installations; Article 210 Branch Circuits; Article 220 Branch Circuit, Feeder, and Service Calculations; Article 310 Conductors for General Wiring; Article 334 Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS; Article 358 Electrical Metallic Tubing: Type EMT; Article 406 Receptacles, Cord Connectors, and Attachment Plugs (Caps); Article 410 Luminaires (Lighting Fixtures), Lampholders, and Lamps; Article 430 Motors, Motor Circuits, and Controllers; Article 440 Air Conditioning and Refrigerating Equipment
The 2007 edition of the “Guide Information for Electrical Equipment (White Book)” published by Underwriters Laboratories Inc. (UL) also is mentioned.
Outdoor receptacles for dwelling unit
A 15-ampere, 125-volt receptacle is installed on the wall outside a detached garage, which is part of a two-family dwelling unit. The garage is at the rear of the dwelling unit, and the outdoor receptacle is approximately 12 feet from the back of the house. Does this receptacle satisfy the requirement for an outdoor receptacle at the rear of the dwelling?
Yes, 210.52(E) requires a receptacle accessible at grade level (6.5 feet or less) at the front and back of the dwelling. There is no requirement for the receptacle to be installed on the dwelling, and there is no requirement for the maximum distance from the building to the receptacle.
Outdoor receptacles must be protected by ground-fault circuit interrupters to comply with 210.8(A)(3), and 406.8(B)(2)(a) requires weatherproof covers, regardless of whether the receptacles are in use.
Incandescent luminaires in closets
Does the National Electrical Code (NEC) permit surface-mounted incandescent (medium-base lampholders) luminaires with spiral-type fluorescent lamps (120 volts, 14 watts) in a clothes closet? How about light-emitting diode (LED) luminaires?
An incandescent luminaire cannot be installed in a clothes closet without a completely enclosed lamp. This requirement is in part (B) of 410.8 and in 410.8(C) “Luminaire (Fixture) Types Not Permitted. Incandescent luminaires (fixtures) with open or partially enclosed lamps and pendant luminaires (fixtures) or lampholders shall not be permitted.”
The 2005 edition of the NEC does not mention LED luminaires, but the 2008 edition permits them. According to 410.16(A)(3), “Luminaire Types Permitted. (3) Surface-mounted fluorescent or LED luminaires identified as suitable for installation within the storage area.”
Electric range circuit-conductor size
I roughed in 8 AWG copper NM cable for an electric range in a one-family dwelling. The owner provided a 16.8-kilowatt (kW) range, which was connected to the 8 AWG branch circuit protected with a 2-pole, 40-ampere circuit breaker. The electrical inspector said the conductor size had to be increased to 6 AWG copper with a 50-ampere overcurrent device to comply with 220.55 and Table 220.55. Do the wire size and overcurrent device have to be increased to comply with the NEC?
Yes, they do. The calculation, using 220.55 and the table, is as follows: An electric range with a kilowatt rating not exceeding 12 will allow an 8-kW demand (for related information, see Code in Focus, page 64). Note 1 to the table requires an increase of 5 percent of the demand for each kilowatt or major fraction by which the nameplate rating exceeds 12; therefore, (0.05 × 5 × 8,000) 2,000 watts are added to the 8,000 watts demand for a total of 10,000 watts. Dividing this figure by 240 volts results in a total current of approximately 42 amperes. According to Table 310.16, this current requires a 6 AWG copper conductor, since 8 AWG copper can carry only 40 amperes. Although 8 AWG copper with 75°C insulation has an ampacity of 50, Article 334.80 limits the ampacity of conductors in Type NM cable to the 60°C column in Table 310.16.
The inspector is correct: 6 AWG copper Type NM cable protected by a 50-ampere, two-pole circuit breaker must be used to comply with the NEC.
Large equipment door requirements
Doors must open in the direction of egress and be equipped with panic hardware or a pressure plate that unlatches the door under simple pressure where electrical equipment is rated 1,200 amperes or more. How far beyond the equipment does this requirement extend?
For equipment rated 1,200 amperes or more that contains overcurrent devices, switching devices or control devices, two doors are required. There must be one at each end of the working space as indicated in Table 110.26(A)(1). Where the working space is twice the distance required by the table, a single door is acceptable. The requirement does not state the maximum distance in which it applies. However, the 2008 edition of the NEC has a revision that extends the distance to 25 feet.
Until the 2008 NEC is adopted, the authority having jurisdiction (AHJ) determines how far from the working space the requirement for door swing and panic hardware applies.
Securing electrical metallic tubing
The electrical inspector has asked for midspan supports for two 2-inch electrical metallic tubes (EMT), which are 3 feet, 9 inches long and connect two switchboards together. Is this a requirement of the NEC?
Yes, Article 358.30(A) requires that electrical metallic tubing be secured within 3 feet of each termination.
A new part (C) is added to 358.30 in the 2008 edition of the NEC that clarifies the requirement for unsupported EMT between enclosures. The addition allows EMT to be unsupported in lengths of 18 inches or less, where oversized, concentric or eccentric knockouts are not involved and the EMT is in unbroken lengths (no couplings).
Cord-and-plug connected motors
Will a 2-horsepower, cord-and-plug-connected motor satisfy the NEC? If the answer is yes, is the cord cap an acceptable disconnecting means?
For cord-and-plug-connected motors, 430.109(F) applies. This part allows a cord-and-plug-connected motor with a horsepower-rated attachment plug and receptacle that are not less than the horsepower rating of the motor to serve as the disconnecting means. A horsepower-rated attachment cap and receptacle are not required for appliances mentioned in 422.33 or room air conditioners covered by 440.63.
Horsepower ratings for receptacles and attachment caps (plugs) are listed in the 2007 edition of the UL White Book. The following is information taken from the tables in the UL White Book, which offers some examples of attachment plug/receptacle combinations that are acceptable for disconnecting a 2-horsepower motor: 277-volt, single-phase, 15-ampere, two-wire, three-pole NEMA Type 7-15; 250-volt, single-phase, 20-ampere, two-pole, three-wire NEMA designation 6-20. There also are three-phase, 277/480-volt, three- and four-pole with four- and five-wire terminations receptacles with matching attachment plugs listed for disconnecting motors up to and including 10 horsepower.
The long lists of various NEMA configurations of receptacles and matching attachment caps vary in horsepower ratings from 0.5 to 10.
Fluorescent lamp ballast disconnect
Have wire connector manufacturers developed a small disconnecting device that may be installed in fluorescent fixtures to satisfy the requirement in 410.73(G)?
Yes, they have. I have seen samples of these devices at International Association of Electrical Inspectors conventions. This is a new requirement in the 2005 edition of the NEC, which has been revised and moved to 410.130(G) in the 2008 edition of the NEC. Part of the rule reads, “Disconnecting Means. In indoor locations, other than dwellings and associated accessory structures, fluorescent luminaires (fixtures) that utilize double-ended lamps and contain ballast(s) that can be serviced in place or ballasted luminaires that are supplied from multiwire branch circuits and contain ballast(s) that can be serviced in place shall have a disconnecting means either internal or external to each luminaire (fixture) to disconnect simultaneously from the source of supply all conductors of the ballast, including the grounded conductor if any.” The line-side terminals of the disconnecting means must be guarded, and the disconnecting means must be accessible to qualified people who will service and maintain the luminaire(s). There are five exceptions to this requirement.
The disconnects I have seen are small male-female connectors that may be installed in the luminaire (fixture). They are rated 3--–5 amperes, 2-wire. The female part connects to the power supply. The male part connects to the ballast.
When adding receptacles in an existing bedroom in a one-family residence, is it necessary to provide arc-fault circuit interrupter protection for the existing branch circuit?
Yes, a new branch circuit to the bedroom for the receptacles would require the branch circuit conductors to be protected by an arc-fault circuit interrupter (AFCI). Before adding receptacles to an existing branch circuit in the bedroom, obtain a ruling from the AHJ, as the NEC does not cover this situation. Although the Code is not retroactive, the addition of receptacles is modifying the existing wiring, and the AHJ should be consulted for a ruling on the installation of an AFCI because the branch circuit is being extended.
Small hole usage in weatherproof disconnect switch
May the one-fourth-inch hole in the bottom of a 60-ampere raintight (3R) disconnect switch be used for a 6 AWG solid copper grounding-electrode conductor?
The one-quarter-inch hole in the bottom of a weatherproof disconnect switch is there to allow any moisture that may accumulate in the enclosure to drain; however, that does not prevent the hole from being used for the grounding-electrode conductor, provided this conductor does not completely close the hole.
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.