You’re reading an outdated article. Please go to the recent issues to find up-to-date content.
There were 3,688 proposals for changes to the National Electrical Code (NEC) and approximately 2,500 comments processed by National Fire Protection Association staff at NFPA headquarters in Quincy, Mass. The following is part two in a series of significant changes for the 2008 NEC. Part one appeared in the July issue of ELECTRICAL CONTRACTOR and can be found here. The 2008 NEC was formally adopted in August 2007, and new copies were available as of September 2007.
The following are some of the most important changes.
Strikethrough text shows deletions, and underlined text shows additions. Commentary denoted by red text also follows some changes for explanation.
Dwelling Unit Receptacle Outlets.
(E) Outdoor Outlets. Outdoor receptacle outlets shall be installed in accordance with (E)(1) through (E)(3).
(1) One-Family and Two-Family Dwellings. For a one-family dwelling and each unit of a two-family dwelling that is at grade level, at least one receptacle outlet accessible while standing at grade level and located not more than 2.0 m (6½ ft) above grade shall be installed at the front and back of the dwelling.
(2) Multi-Family Dwellings. For each dwelling unit of a multifamily dwelling where the dwelling unit is located at grade level and provided with individual exterior entrance/egress, at least one receptacle outlet accessible from grade level and not more than 2.0 m (6½ ft) above grade shall be installed. See 210.8(A)(3).
(3) Balconies, Decks, and Porches. Balconies, decks, and porches that are accessible from inside the dwelling unit shall have at least one receptacle outlet installed within the perimeter of the balcony, deck, or porch. The receptacle shall not be located more than 2.0 m (6½ ft) above the balcony, deck, or porch surface.
Exception to (3): Balconies, decks, or porches with a useable area of less than 1.86 m2 (20 ft2) are not required to have a receptacle installed.
The new item (3) the panel added requires a receptacle be installed on any porch, deck or balcony where the porch, deck or balcony is accessible from inside the dwelling unit. The panel intends this receptacle to be in addition to those that are installed to meet (1) or (2).
Comment 2-225 adds text to clarify that at least one receptacle must be accessible while standing at grade level. The word “located” was added to make the language more technically correct.
Comment 2-227 clarifies that porches, decks and balconies accessible from inside the dwelling units must have at least one receptacle outlet installed within the perimeter of the porch, deck or balcony. The receptacle also must be located at not more than 6½ feet above the porch, deck or balcony.
Comment 2-230 adds an exception to not require that a receptacle be installed for a porch, deck or balcony that has a usable area of less than 20 square feet, expecially if these areas are used for decorative or architectural purposes.
At least one receptacle outlet shall be installed
directly above a show window for each 3.7 linear m (12 linear ft) or major fraction thereof of show window area measured horizontally at its maximum width.
At least one receptacle outlet shall be installed
within 450 mm (18 in) of the top ofa show window for each 3.7 linear m (12 linear ft) or major fraction thereof of show window area measured horizontally at its maximum width.
Requiring show window receptacles to be placed at a height of not greater than 18 inches above the show window will provide easy access to the receptacles and will limit the use of extension cords in these applications.
Identification for Feeders.
(C) Ungrounded Conductors. Where the premises wiring system has feeders supplied from more than one nominal voltage system, each ungrounded conductor of a feeder, where accessible, shall be identified by system. The
means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means and shall be permanently posted at each feeder panelboard or similar feeder distribution equipment.
Identification for Feeders.
(C) Ungrounded Conductors. Where the premises wiring system has feeders supplied from more than one nominal voltage system, each ungrounded conductor of a feeder, where accessible, shall be identified by phase or line and system. The method utilized for conductors originating within each feeder panelboard or similar feeder distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each feeder panelboard or similar feeder distribution equipment.
Requiring identification of each ungrounded conductor of the feeder by phase or by line in a single-phase system and identification by system will help electrical installation and maintenance personnel identify each phase of the system. The last line in this section has been revised to require the identification posted at the panelboard or be documented in a manner that is readily available to identify the conductors that originate at each panelboard.
Rating of Disconnect.
The feeder or branch-circuit disconnecting means shall have a rating of not less than the calculated load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits, Parts III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. Where the branch circuit or feeder disconnecting means consists of more than one switch or circuit breaker, as permitted by 225.33, combining the ratings of all the switches or circuit breakers for determining the rating of the disconnecting means shall be permitted. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D).
Adding the word “calculated” agrees with changes made throughout the Code in 2005. The second change involves an added sentence for dealing with multiple disconnects. Since a disconnecting means is a device or group of devices, permission is inherent to add each device to reach a total rating in compliance with this section. The new revised text will eliminate any confusion regarding the inherent permission for breakers to be additive in calculating the rating of a disconnecting means. For example, where the feeder or branch-circuit disconnecting means is required to be not less than 60 amperes, the ratings of each of the multiple disconnects can be combined. Two 30-ampere disconnects would satisfy the minimum 60-ampere requirement.
Cable tray systems shall be permitted to support service-entrance conductors. Cable trays used to support service-entrance conductors shall contain only service-entrance conductors.
Exception: Conductors, other than service-entrance conductors, shall be permitted to be installed in a cable tray with service-entrance conductors, provided a solid fixed barrier of a material compatible with the cable tray is installed to separate the service-entrance conductors from other conductors installed in the cable tray. Cable trays shall be identified with permanently affixed labels with the wording “Service-Entrance Conductors.” The labels shall be located so as to be visible after installation and placed so that the service-entrance conductors may be readily traced through the entire length of the cable tray.
Text has been added to the exception where conductors other than service-entrance conductors are installed in cable trays with service-entrance conductors. Where these other conductors are added, they must be separated by a fixed solid barrier, but now, in addition, labels must be installed with the wording “Service-Entrance Conductors” readily visible after installation and placed so the service-entrance conductors can be easily traced through the entire length of cable tray.
Location in or on Premises.
(F) Not Located Over Steps. Overcurrent devices shall not be located over steps of a stairway.
New 240.24(F) does not permit overcurrent protection devices to be located over the riser steps of a stairway since anyone trying to work on the devices would not be able to have a level workplace, and it may be dangerous. However, many stairways have horizontal landings that could prove suitable for installations where appropriate working space exists, so this new section applies only to the riser part of the stairs.
(A) Selected Under Engineering Supervision in Existing Installations. The series rated combination devices shall be selected by a licensed professional engineer engaged primarily in the design or maintenance of electrical installations. The selection shall be documented and stamped by the professional engineer. This documentation shall be available to those authorized to design, install, inspect, maintain, and operate the system. This series combination rating, including identification of the upstream device, shall be field marked on the end use equipment. The marking shall be readily visible and state the following:
CAUTION – SERIES COMBINATION SYSTEM
REPLACE WITH: TYPE BREAKER
For calculated applications, the engineer shall ensure that the downstream circuit breaker(s) that are part of the series combination remain passive during the interruption period of the line side fully rated, current-limiting device.
The new sentence that was added provides some clarification to the overall application of calculations for existing installations. Devices that are part of the series combination system must be passive downstream during the reaction time of the upstream device, and the engineer must be able to ensure that the downstream devices are passive as part of the overall calculation. The passive downstream device ensures increased impedance will not occur due to arcing between the contacts of the downstream device. EC
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at [email protected]. James G. STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the NEC and OSHA, as well as other standards. Contact him at 817.581.2206. JAMES W. STALLCUP is vice president and senior editor at Grayboy.