Revisions for the 2014 NEC, With Cover, First Printing

2014

N

Revisions for the 2014

E

National Electrical Code®

NOVEL ENGINEERING

Patrick S. Ouillette, P.E. 449 WashingtonStreet C a m de n, M ai ne 04

With Maine Appendices

84 3

A textbook for continuing education

w w w. no ve le ng in ee rin g. co m

www.novelengineering.com

Patrick S. Ouillette, P.E. Novel Engineering 1/1/2014

Revisions for the 2014 National Electrical Code® With Maine Appendices

A program for continuing education

By Patrick S. Ouillette, P.E. Published by: Novel Engineering 449 Washington Street Camden, Maine 04843 www.novelengineering.com

Copyright © 2013 by Patrick S. Ouillette Printed in the United States of America

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the copyright owner.

Acknowledgements Any reprinted information is done with permission from NFPA 70 ®-2014, National Electrical ® Code , Copyright © 2013, National Fire Protection Association, Quincy, MA. This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety. ®

®

NFPA 70 , National Electrical Code and NEC , frequently referred to in this text, are registered trademarks of the National Fire Protection Association, Quincy, MA.

Disclaimer Great care has been taken in the preparation of this text to ensure accuracy of the material herein, both technical and typographical. However, the author and publisher will not be liable for any errors that may exist within the text, or for any information in the text that may be misconstrued or misapplied.

Preface This text is intended to familiarize the reader with the major changes contained in the 2014 National Electrical Code. ® The book is suited for both distance learning (self-study) and for the traditional classroom setting. It is suitable for anyone exposed to the NEC ® at any level. Those well experienced in the Code will find depth in the coverage. Less experienced Code users will find the information understandable. The author attempts to tie the entire NEC together through the study of the changes, Code Refreshers, and through key concepts and NEC basics weaved throughout the book. The text addresses Code revisions that apply to all types of occupancies: residential, commercial, and industrial. Visual learning is a major objective of the book’s presentation of the Code changes. The layout and the method of presentation will enable Code users to easily navigate through the changes. Through the heading(s) at the beginning of each Code change addressed in the text, the reader will readily identify the section affected by the change and the specific subject being discussed. The Significance section serves as an introduction to the Code change under discussion. An Analysis of the Code change follows, with explanation where necessary to help the student understand the revision, its background, and the logic of the change. Graphics, photographs, examples, or calculations are used to illustrate the change and to enhance learning. The Summary is a brief re-statement of the highlights of the Code change. An Application Question, with Answer and key to the correct answer, is included at the end of each Code section studied for exercise in applying the change and to broaden learning. Many of the sections analyzed contain a Code Refresher that addresses existing Code requirements related to the change.

Patrick S. Ouillette. P.E.

Notes Page 210.12(A)

2014 NEC

Table of Contents Code-Wide Changes ........................................................................................................................... 1

Chapter 1 – General Article 100 – Definitions ........................................... .............................................. ............................ 4 Article 110 – Requirements for Electrical Installations

110.16 – Arc-Flash Hazard Warning .......................................................................................................... 6 110.21(B) – Field-Applied Markings .......................................................................................................... 7 110.25 – Lockable Disconnecting Means .................................................................................................. 8 110.26(C)(3) – Spaces About Electrical Equipment – Entrance to and Egress from Working Space – Personnel Doors ........................................................................................................ 9 110.26(E)(2) – Part II. 600 Volts, Nominal, or Less – Spaces About Electrical Equipment – Dedicated Equipment Space – Outdoor ............................................................................................. 10

Chapter 2 – Wiring and Protection

_____________

Article 200 – Use and Identification of Grounded Conductors

200.4(B) – Neutral Conductors – Multiple Circuits ................................................................................. 11 Article 210 – Branch Circuits

210.5(C)(2) – Identification for Branch Circuits – Identification of Ungrounded Conductors – Branch Circuits Supplied from Direct-Current Systems ..................................................................... 12 210.8(A)(9) – Ground-Fault Circuit-Interrupter Protection for Personnel – Dwelling Units – Bathtubs or shower stalls ................................................................................................................... 14 210.8(A)(10) – Ground-Fault Circuit-Interrupter Protection for Personnel – Dwelling Units – Laundry areas ..................................................................................................................................... 15 210.8(B)(8) – Ground-Fault Circuit-Interrupter Protection for Personnel – Other Than Dwelling Units – Garages, service bays, and similar areas other than vehicle exhibition halls and showrooms .................................................................................................................................. 16

210.8(D) – Ground-Fault Circuit-Interrupter Protection for Personnel – Kitchen Dishwasher Branch Circuit ..................................................................................................................................... 17 210.12(A) – Arc-Fault Circuit-Interrupter Protection – Dwelling Units .................................................. 18 210.12(B) – Arc-Fault Circuit-Interrupter Protection – Branch Circuit Extensions or Modifications – Dwelling Units ....................................................................................................... 24 210.12(C) – Arc-Fault Circuit-Interrupter Protection – Dormitory Units ................................................ 27 210.13 – Ground-Fault Protection of Equipment .................................................................................. 29 210.17 (and Article 625) – Part I. General Provisions – Electric Vehicle Branch Circuit ........................ 30 210.19(A)(1) – Conductors—Minimum Ampacity and Size – Branch Circuits Not More Than 600 Volts 215.2(A)(1) – Minimum Rating and Size – Feeders Not More Than 600 Volts................................... 31 210.52(E)(1) and (E)(2) – Dwelling Unit Receptacle Outlets – Outdoor Outlets – One-Family and Two-Family Dwellings – Multifamily Dwellings ........................................................ 32 210.52(E)(3) – Dwelling Unit Receptacle Outlets – Outdoor Outlets – Balconies, Decks, and Porches ............................................................................................................ 33 210.52(G)(1) – Dwelling Unit Receptacle Outlets – Basements, Garages, and Accessory Buildings – Garages ............................................................................................................................................... 34 210.64 – Part III. Required Outlets – Electrical Service Areas ................................................................ 35 Article 220 – Branch-Circuit, Feeder, and Service Calculations

220.12, Exception – Part II. Branch-Circuit Load calculations – Lighting Load for Specified Occupancies – Exception .................................................................................................................... 36 Article 240 – Overcurrent Protection

240.87 – Part VII. Circuit Breakers – Arc Energy Reduction ................................................................... 37 Article 250 – Grounding and Bonding

250.64(B) – Grounding Electrode Conductor Installation – Securing and Protection Against Physical Damage ................................................................................................................................. 38 250.66(A) and (B) – Size of Alternating-Current Grounding Electrode Conductor – Connections to a Rod, Pipe, or Plate Electrode(s) – Connections to Concrete-Encased Electrodes ....................... 39 250.68(C)(2) – Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes – Grounding Electrode Connections ................................................................................. 40 250.68(C)(3) – Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes – Grounding Electrode Connections – A concrete-encased electrode............................. 41 Table 250.102(C) – Bonding Conductors and Jumpers – Size – Supply-Side Bonding Jumper ............... 43

250.130(C)(4) – Part VII. Methods of Equipment Grounding – Equipment Grounding Conductor Connections – Nongrounding Receptacle Replacement or Branch Circuit Extensions ...................... 45 250.167 – Part VIII. Direct-Current Systems – Direct-Current Ground-Fault Detection ........................ 46 250.186 – Part X. Grounding of Systems and Circuits of over 1000 Volts – Ground-Fault Circuit Conductor Brought to Service Equipment............................................................................... 47 250.194 – Part X. Grounding of Systems and Circuits of over 1000 Volts – Grounding and Bonding of Fences and Other Metal Structures ................................................................................. 48

Chapter 3 – Wiring Methods and Materials Article 300 – General Requirements for Wiring Methods and Materials

300.22(C)(1) – Wiring in Ducts Not Used for Air Handling, Fabricated Ducts for Environmental Air, and Other Spaces for Environmental Air (Plenums) – Other Spaces Used for Environmental Air (Plenums) – Wiring Methods......................................................................................................... 50 Article 310 – Conductors for General Wiring

310.15(B)(3)(c) and Table – Ampacities for Conductors Rated 0-2000 Volts – Tables – Adjustment Factors – Raceways and Cables Exposed to Sunlight on Rooftops ................................. 51 Table 310.15(B)(7) – Ampacities for Conductors Rated 0-2000 Volts – 120/240-Volt, Single-Phase Dwelling Services and Feeders ...................................................................................... 53 Article 330 – Metal-Clad Cable: Type MC

330.30(D)(3) – Securing and Supporting – Unsupported Cables ............................................................ 56 Article 338 – Service-Entrance Cable: Types SE and USE

338.10(B)(4)(b) – Uses Permitted – Branch Circuits or Feeders – Installation Methods for Branch Circuits and Feeders – Exterior Installations .......................................................................... 57 Article 348 – Flexible Metal Conduit: Type FMC

348.30(A), Exception No. 4 (and others) – Securing and Supporting – Securely Fastened .................... 58 Article 376 – Metal Wireways

376.22(B) – Part II. Installation – Number of Conductors and Ampacity – Adjustment Factors ........... 59 Article 392 – Cable Trays

392.10(A) and Table 392.10(A) – Used Permitted – Wiring Methods .................................................... 60 392.18(H) and Exception – Cable Tray Installation – Marking ................................................................ 61 Article 393 – Low-Voltage Suspended Ceiling Power Distribution Systems ............................................ 62

Chapter 4 – Equipment for General Use Article 404 – Switches

404.2(C) – Switch Connections – Switches Controlling Lighting Loads ................................................... 65 404.8(C) – Accessibility and Grouping – Multipole Snap Switches ......................................................... 66 Article 406 – Receptacles, Cord Connectors, and Attachment Plugs (Caps)

406.3(E) – Receptacle Rating and Type – Controlled Receptacle Marking ............................................. 67 406.4(D)(4) – General Installation Requirements – Replacements – Arc-Fault Circuit-Interrupter Protection ............................................................................................................ 69 406.9(B)(1) – Receptacles in Damp or Wet Locations – Wet Locations – Receptacles of 15 and 20 Amperes in a Wet Location ............................................................................................... 70 406.15 – Dimmer-Controlled Receptacles .............................................................................................. 71 Article 408 – Switchboards, Switchgear, and Panelboards

408.55(C) – Part IV. Construction Specifications – Wire-Bending Space Within an Enclosure Containing a Panelboard – Back Wire-Bending Space ....................................................................... 72 Article 422 – Appliances

422.23 – Tire Inflation and Automotive Vacuum Machines ................................................................. 73 Article 424 – Fixed Electric Space-Heating Equipment

424.66(A) and (B) – Part VI. Duct Heaters – Installation – General – Limited Access .......................... 74 Article 445 – Generators

445.11 – Marking .................................................................................................................................... 75 445.20 – Ground-Fault Circuit-Interrupter Protection for Receptacles on 15-kW or Smaller Portable Generators .......................................................................................................... 77 Article 450 – Transformers and Transformer Vaults

450.10(A) – Grounding – Dry-Type Transformer Enclosures .................................................................. 79 450.11(B) – Marking – Source Marking .................................................................................................. 80 Article 480 – Storage Batteries .................................................................................................................. 81

Chapter 5 – Special Occupancies Article 517 – Health Care Facilities

517.18 – General Care Areas – Patient Bed Location – Patient Bed Location Receptacles .................... 82

517.19 – Critical Care Areas – Patient Bed Location Branch Circuits – Patient Bed Location Receptacles ...................................................................................................... 84 517.19(C) – Critical Care Areas – Operating Room Receptacles ............................................................ 85 517.30(G) – Essential Electrical Systems for Hospitals – Coordination .................................................. 87 Article 547 – Agricultural Buildings Article 555 – Marinas and Boatyards

547.5(F) – Wiring Methods – Separate Equipment Grounding Conductor 555.15(B) – Grounding – Type of Equipment Grounding Conductor ..................................................... 89 Article 551 – Recreational Vehicles and Recreational Vehicle Parks

551.71 – Part VI. Recreational Vehicle Parks – Type Receptacles Provided ........................................ 90 Article 590 – Temporary Installations

590.4(I) and (J) – General – Termination(s) at Devices – Support .......................................................... 91

Chapter 6 – Special Equipment Article 600 – Electric Signs and Outline Lighting

600.6(A)(1) – Disconnects – Location – At Point of Entry to a Sign Enclosure ....................................... 92 Article 646 – Modular Data Centers .......................................................................................................... 93 Article 680 – Swimming Pools, Fountains, and Similar Installations

680.22(B)(6) – Part II. Permanently Installed Pools – Lighting, Receptacles, and Equipment – Luminaires, Lighting Outlets, and Ceiling-Suspended (Paddle) Fans – Low-Voltage Luminaires ....... 95 680.42(B) and (C) – Part IV. Spas and Hot Tubs – Outdoor Installations – (B) Bonding – (C) Interior Wiring to Outdoor Installations ....................................................................................... 96 Article 690 – Solar Photovoltaic (PV) Systems

690.12 and 690.56(C) – Rapid Shutdown of PV Systems on Buildings ................................................... 97 Article 694 – Wind Electric Systems ........................................................................................................... 99

Chapter 7 – Special Conditions Article 700 – Emergency Systems

700.8 – Surge Protection ....................................................................................................................... 100

700.16 – Part IV. Emergency System Circuits for Lighting and Power – Emergency Illumination ....... 101 Article 728 – Fire-Resistive Cable Systems .............................................................................................. 102 Article 750 – Energy Management Systems............................................................................................ 104 Article 770 – Optical Fiber Cables and Raceways

770.110 – Part V. Installation Methods Within Buildings – Raceways and Cable Routing Assemblies for Optical Fiber Cables ................................................................................................. 106

Chapter 8 – Communications Systems Article 800 – Communications Circuits ........................................ ............................................... ..... 107

Chapter 9 – Tables INFORMATIVE ANNEX J ............................................ .............................................. ........................ 108 _____________________________________________________________________________________ Other Important Changes ........................................................................................................................ 109 Maine Appendices

Appendix A – Common 2011 National Electrical Code® Violations ............................................................ Appendix B – Maine Amendments to the 2011 National Electrical Code® ................................................ Appendix C – Important Statute Changes ................................................................................................... Appendix D – Important Rule Changes .......................................................................................................

Code-Wide Changes

2014 NEC

Four New Articles and New Informative Annex J Article 393 – Low-Voltage Suspended Ceiling Power Distribution Systems New Article 393 provides rules for distribution of low voltage current through suspended ceiling grid designed for power distribution for the supply of luminaires, sensors, and other low power devices and equipment located within, on, or suspended below the ceiling grid. Equipment is supplied by Class 2 circuits using approved cables and connectors. Article 646 – Modular Data Centers New Article 646 – Modular Data Centers contains requirements for prefabricated structures or enclosures that house IT equipment and related systems such as power, backup power, HVAC, and others. The article contains specific new requirements and directs Code uses to applicable existing requirements in other articles. Article 728 – Fire-Resistive Cable Systems New Article 728 – Fire-Resistive Cable Systems contains detailed requirements for installation of fire-resistive cable systems. Its purpose is to enhance the survivability of critical circuits to ensure continued operation for a specified period of time under fire conditions. The components of fire-resistive cable systems are tested and listed as a system and shall not be interchangeable between systems. The systems must be installed in accordance with this Code and all instructions included in the listing. Robust securing and supporting of fire-resistive cable systems shall be in accordance with the listing and manufacturer’s instructions. Fire-resistive cable systems are part of Electrical Circuit Protective Systems, UL Category FHIT. Article 750 – Energy Management Systems Article 750 – Energy Management Systems (EMS) contains rules that prohibit energy management systems from overriding load shedding controls that are in place to ensure minimum capacity requirements for fire pumps, emergency systems, and other required standby and critical power systems. An EMS shall not be permitted to disconnect power to circuits supplying emergency lighting, essential electrical systems in health care facilities, ventilation equipment exhausting hazardous gas, or power to elevators, moving walks and similar equipment. An EMS may not cause any service, feeder, or branch circuit to become overloaded. Also, an EMS is prohibited from overriding any control necessary for ensuring continuity of alternate power sources for critical loads. Informative Annex J The 2014 NEC includes Informational Annex J, ADA Standards for Accessible Design, to assist Code users in considering electrical design constraints for electrical and other building systems in buildings required to comply with ADA, e.g., requirements for switch and receptacle heights.

These new articles and Informative Annex J are covered in more detail within this textbook.

Copyright 2013 by Patrick S. Ouillette, P.E.

1

Code-Wide Changes

2014 NEC

Lockable Disconnecting Means Many sections of the NEC require a disconnecting means to be capable of being locked in the open position, sometimes as a requirement for permitting an exception to the rule. Further, the provisions for locking or adding a lock to the disconnecting means shall remain in place with or without the lock installed. This language has been inserted into new Section 110.25. Instead of rewriting this requirement in various sections throughout the Code, those sections now state that the disconnecting means shall be “lockable in accordance with 110.25.” Section 110.25 is covered in more detail within this textbook. Requirements for DC Systems Requirements for DC systems integrated throughout the NEC is a result of the NEC DC Task Force that was established to review the Code’s existing DC requirements and make recommendations in the form of proposals, where the NEC was deemed lacking in addressing new DC technologies. The increasing use of on-site generation and utilization of DC power from such sources as photovoltaic systems is one example of the need for expanded NEC coverage of DC systems. Electric vehicle charging, DC microgrids, and wind electric generation systems require NEC rules for safe installations. Some of the DC-related changes in the 2014 NEC are new Article 393 – Low-Voltage Suspended Ceiling Power Distribution Systems, revisions to Article 480 – Storage Batteries, revisions to Article 690 – PV Systems, switchboards and panelboards for DC systems in Article 408, and new sections to identify ungrounded branch-circuit and feeder conductors supplied from DC systems. This textbook analyses several Code articles/sections related to DC systems. Use of the Term Switchgear Incorporated throughout theNEC The term switchgear has replaced metal-enclosed power switchgear in Article 100 and throughout the Code. The definition of switchgear is essentially the same as the former definition of metalenclosed power switchgear. All switchgear subject to NEC requirements is metal enclosed. Switchgear rated 1000 V or less may be identified as “low-voltage power circuit breaker switchgear.” Switchgear rated over 1000 V may be identified as “metal-enclosed switchgear” or “metal-clad switchgear.”

Article 408 – Switchboards and Panelboards is re-titled “Switchboards, Switchgear, and Panelboards.” Article 490 – Equipment Over 1000 Volts, Nominal now uses the term switchgear in place of metal-enclosed switchgear and metal-enclosed power switchgear. Other places in the Code have replaced metal-enclosed switchgear with switchgear. Several Code sections add switchgear where switchboards are listed. Voltage Threshold: Changed from “Over 600 Volts” to “Over 1000 Volts” Some wind generating systems operate above the existing 600-V threshold (690 volts AC is common) and solar photovoltaic (PV) systems operate in a range of DC voltages up to and including 1000 V and higher. The “High Voltage Task Group” was appointed by the Technical Correlating Committee to review existing Code and submit new proposals to address the need for installation rules for circuits and systems operating at over 600 volts.


2

Code-Wide Changes

2014 NEC

As a result of their work, several Code articles now address Over 1000 Volts in place of Over 600 Volts. Some articles retained the 600-V threshold, particularly where there were safety concerns. This process will continue to evolve. Equipment must be manufactured and tested for the new voltage level. Changes may be needed to tools, electrical testers, and safety equipment, including safety clothing. Conductor insulations, equipment and terminal spacings, work space clearances, and more will be affected. Article 690 – Solar Photovoltaic (PV) Systems and Article 694 – Wind Electric Systems are among the articles that contain requirements for systems operating over 1000 volts. UL currently lists PV cable and other equipment for operation over 600 volts. Article 250 – Grounding and Bonding began to address grounding of systems and circuits of 1 kV and over in the 1981 edition of the NEC.


3

Article 100

Definitions

2014 NEC

Coordination (Selective) [revised definition] “Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.” The revision makes it clear that selective coordination is the isolation of downstream overcurrent conditions over the complete range of available overcurrents and associated opening times.

Premises Wiring (System) [new Informational Note] “Interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all their associated hardware, fittings, and wiring devices, both permanently and temporarily installed. This includes (a) wiring from the service point or power source to the outlets or (b) wiring from and including the power source to the outlets where there is no service point.” “Such wiring does not include wiring internal to appliances, luminaires, motors, controllers, motor control centers, and similar equipment.” “Informational Note: Power sources include, but are not limited to, interconnected or stand-alone batteries, solar photovoltaic systems, other distributed generation systems, or generators.”

The new Informational Note provides some examples of premises wiring systems. Not all premises wiring is supplied by a utility service, i.e., there may not be a service point. Portable generators and their associated wiring constitute premises wiring, unless used to serve installations not coved within the scope of the NEC in 90.2(B).

Readily Accessible [revised definition] “Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to actions such as to use tools, to climb over or remove obstacles, or to resort to portable ladders, and so forth.” Where a disconnecting means is required to be readily accessible, even the use of a simple screwdriver to access the disconnect renders the disconnect not readily accessible (only accessible). This can be the case in certain HVAC equipment where a built-in disconnect is located behind an access panel that requires a screwdriver to remove or open.

Retrofit Kit [new definition] “A general term for a complete subassembly of parts and devices for field conversion of utilization equipment.” The term “retrofit kit” is used in Article 410 – Luminaires, Lampholders, and Lamps, and in Article 600 – Electric Signs and Outline Lighting. For use within the scope of these articles, retrofit kits are required to be listed. With the move toward energy-efficient lighting, retrofit kits used to upgrade lighting sources (many to LED lighting) are increasingly popular.


4

Article 100

Definitions

2014 NEC

Separately Derived System [revised definition] “An electrical source, other than a service, having no direct connection(s) to circuit conductors of any other electrical source other than those established by grounding and bonding connections.” Separately derived systems are not services. Only a utility company supplies power via a service. Grounding the neutral of a separately derived system (e.g., a transformer) in a building to metal water piping or structural steel in the vicinity of the separately derived system will nearly always form a connection to another system’s grounded conductor. The electrode used (structural steel or metal water piping) to ground the separately derived system must qualify as a grounding electrode. The revised definition clarifies that a common grounding electrode conductor used to ground multiple separately derived systems, as permitted in 250.30(A)(6), does not disqualify the systems from being separately derived systems.


5

110.16

Requirements for Electrical Installations

2014 NEC

Arc-Flash Hazard Warning Significance Arc-flash hazard warning labels that are factory applied meet the marking requirements of this section. Analysis Electrical equipment such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers, that are in other than dwelling units, and are likely to require examination, adjustment, servicing, or maintenance while energized shall be

marked to warn qualified persons of potential arc flash hazards. This Code revision permits equipment to be either field marked or factory marked. Many manufacturers are marking equipment with appropriate arc flash warning labels, so there is no need for field marking. The installer, though, is ultimately responsible for compliance with this section. The marking shall be located such that it is clearly visible to qualified persons who will examine or service the equipment. Also new in this Code edition is the requirement that the marking meet the provisions of 110.21(B), which is itself new to the 2014 NEC. According to Section 110.21(B), labels shall be permanently affixed to the equipment or wiring method, shall be of sufficient durability to withstand the environment, and shall adequately warn of the hazard using effective words and/or colors and/or symbols. Like the 2011 NEC, the 2014 Code does not specify the content and details of the warning label, since this information is deemed related to workplace safety rather than installation, and thus, beyond the scope of the NEC. Informational Note No. 1 makes reference to NFPA 70E2012, Standard for Electrical Safety in the Workplace, which provides guidance in determining the level of exposure, planning safe work practices, arc flash labeling, and selecting personal protective equipment (PPE). Informational Note No. 2 references ANZI Z535.4, Product Safety Signs and Labels for guidelines for the design of safety sign and labels.

WARNING

This label meets both the 2014 NEC and NFPA 70E-2012 requirements.

Ar c Fl ash and Sho ck Hazard Requires arc-rated protection for

6.8 calories/cm

2

Working distance = 18 inches Nominal system voltage: 480Y/277 Arc flash boundary: 4 ft

Note: Factory marking of the information required by 70E is generally not feasible due to the variety of equipment applications.

Summary: Arc flash warning labels may be field or factory applied. Field-applied marking shall meet the requirements of new 110.21(B), which contains general requirements for field marking. Application Question

Does the NEC require the available incident energy to be marked on electrical equipment? Answer: No, but NFPA 70E does. Section 130.5(C) of 70E-2012 requires equipment to be field marked to specify either the available incident energy, in calories/cm2, or the minimum arc rating of PPE, also expressed in calories/cm2; the nominal system voltage; and the arc flash boundary.


6

110.21(B)


2014 NEC

Field-Applied Markings Significance A new subsection had been added to 110.21 that contains requirements when implementing the DANGER, WARNING, and CATUTION markings required by theNEC. Analysis Various sections of the Code require field marking using one of these signal words: “DANGER”, “WARNING”, or “CAUTION.” This Code change seeks to provide consistency in the required marking by establishing the visual format, durability, and suitability criteria for these three types of markings. The marking/label shall adequately warn of the hazard using effective words and/or colors and/or symbols. The label shall be permanently affixed to the equipment or wiring method and shall be of sufficient durability to withstand the environment involved. Labels shall not be hand written, except where they are variable or could be subject to change. Informational Notes reference ANSI Z535.4-2011, Product Safety Signs and Labels, which provides guidelines for suitable font sizes, words, colors, symbols, and placement requirements for safety signs and labels. The labels below are examples of safety labels that conform to ANSI Z535. Labels should include a description of the hazard, a way to avoid the hazard, and consequences if ignored (partly understood by having knowledge of the label’s meaning). The DANGER label below will probably satisfy most AHJs as compliant with 110.21(B) and 110.34(C). It would be better if it included the consequence, e.g., “Contact will cause electric shock or burn.” Safety alert symbol

Signal word

DANGER HIGH VOLTAGE – KEEP OUT

Indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury.

Red background and exclamation point

WARNING Orange background and exclamation point

CAUTION Yellow background and exclamation point

Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury. Indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate injury. The signal word without the safety alert symbol is sometimes used when the message addresses only a hazard to property and not to persons.

Summary Where DANGER, WARNING, or CAUTION labels are required by the NEC, field-applied labels shall be permanently affixed to the equipment or wiring method, shall be of sufficient durability to withstand the environment, and shall adequately warn of the hazard using effective words and/or colors and/or symbols. Application Question: What safety label requirements are included in Article 110 that require signal words? Answer: Sections 110.22(B) and (C), CAUTION (for series combination systems); 110.34(C), DANGER (for over 600 volts); and possibly 110.28(C), “conspicuous warning signs” (forbidding unqualified persons to enter rooms or locations containing exposed live parts). Copyright 2013 by Patrick S. Ouillette, P.E.

7

110.25


2014 NEC

Lockable Disconnecting Means Significance Several sections of the new Code require disconnects to be “lockable in accordance with 110.25.” Analysis Many sections of the NEC require disconnecting means to be lockable in the open position. Further, the provision for locking must remain in place with or without the lock installed. This facilitates lockout/tagout (LOTO). Instead of repeating the rules for a “lockable open” disconnecting means in various sections of the Code, the 2014 NEC places the provisions in

Article 110. The 2014 Code adds an exception for cord-and-plug-connected equipment that might require the equipment to be locked off/open. There are products on the market designed to be placed over a cord plug and locked, thereby preventing use of the plug. The plug lock is stored on the cord while the equipment is energized. The exception recognizes that this provision for locking cannot remain in place. Some sections of the NEC permit a cord and plug to serve as the required disconnecting means, but do not require any cord-and-plug disconnecting means to be lockable open. However, OSHA regulations in 29 CFR 1910-147 do require certain cord-andplug-connected equipment to be lockable open, except where the plug is under the exclusive control of the employee servicing the equipment. Examples of Code sections that require disconnecting means to be “lockable in accordance with 110.25” are 430.102(B), Exception, for motor disconnecting means; and 422.31(B), for permanently connected appliances rated over 300 volt-amperes. Summary New 110.25 contains rules that must be complied with for

a disconnecting means to qualify as lockable open. An exception recognizes that where the disconnecting means is permitted to be a plug for cord-and-plug-connected equipment, the provision for locking cannot remain in place.

This lockout kit contains locking devices and accessories for several sizes of single-pole and multi-pole circuit breakers. Courtesy of Brady Worldwide, Inc.

Application Question There is a simple metal locking device available that fits over a standard size single-pole breaker handle and uses a set screw to “lock” the breaker in the ON or OFF position. Does this device comply with 110.25? Answer: No. The device may be useful to help ensure that certain circuit breakers remain ON or OFF, but the “locking” provision is not suitable, since it can be defeated with a simple screwdriver.


8

110.26(C)(3)


2014 NEC

Spaces About Electrical Equipment – Entrance to and Egress from Working Space – Personnel Doors Significance The threshold at which listed panic hardware is required on egress doors from electrical equipment working spaces has been reduced from 1200 A to 800 A. Analysis Specifications for personnel doors intended for entrance to and egress from electrical equipment working spaces are only concerned with the safety of persons. The threshold of 1200 A relates to

the number of personnel doors required, but equipment ratings less than 1200 A pose significant exposure to arc flash. Code-Making Panel 1 has chosen 800 A as the minimum equipment rating where egress doors within 25 feet of the working space require listed panic hardware to facilitate egress by persons who may have been injured while examining or working on equipment. The doors must open in the direction of travel. The 800-A rating is not cumulative. Two separate 400A rated pieces of equipment will not trigger the requirement.

Equipment rated 800 A or more that contains overcurrent devices, switching devices, or control devices

3

′

Working space

Equip. rated 800 A or more that contains overcurrent, switching, or control devices

3

′

3

′

Working space

3

′

′

4

′

Electrical Room

4

5 2

′

n a h t s s e L

Note: Only 1 personnel door is required.

This door is intended for entrance to and egress from the electrical equipment working space.

Listed panic hardware – typical for rooms containing electrical equipment rated 800 A or more

These doors must open in the direction of egress and must be equipped with listed panic hardware.

Summary All doors intended for entrance to and egress from any room where electrical equipment rated 800 A or more is installed, and are less than 25′ from the nearest edge of the working space, shall open in the direction of egress and be equipped with listed panic hardware. Application Question T F Rooms that are not dedicated electrical equipment rooms are exempt from the rules

specifying the number of egress doors required and the specifications for the doors. Answer: False. Any room where electrical equipment is installed must comply with working space and applicable egress door requirements. Any area where electrical equipment is installed must comply with applicable working space requirements.


9

110.26(E)(2)


2014 NEC

Part II. 600 Volts, Nominal, or Less – Spaces About Electrical Equipment – Dedicated Equipment Space – Outdoor Significance Dedicated equipment space is now required for certain outdoor electrical equipment. Analysis Electrical distribution equipment is sometimes located outdoors, along with HVAC equipment, PV system inverters and disconnects, generator equipment and disconnecting means, etc. This may be especially true for slab-on-grade construction. It makes sense for large electric loads and

electrical sources to be in close proximity, but proper design is necessary to ensure safe working space about all equipment. Working space in 110.26(A) is for the protection of the worker, while dedicated equipment space is to ensure future wiring access to the equipment and protection of electrical equipment from intrusion by non-electrical equipment. In the existing Code, rules for working space about electrical equipment include outdoor locations, but dedicated equipment space for outdoor locations is new in 2014. The space equal to the width and depth of the equipment and extending from grade to a height of 6 ft above the equipment shall be dedicated to the electrical installation. This permits unobstructed access for conduits and cables to be installed in and out of electrical panelboards and other equipment. No piping or other equipment foreign to the electrical installation is permitted in this space. Gas piping, water piping, refrigeration lines, compressed air lines, and phone and internet equipment are examples of foreign equipment that must not be installed above or below a panel or certain other electrical equipment in the dedicated space. Service disconnect and branch circuit breakers (panelboard)

Summary Dedicated equipment space shall be provided for switchboards, switchgear, panelboards, and motor control centers installed in outdoor locations. The space shall be equal to the width and depth of the equipment and extend from grade to a height of 6 ft above the equipment. Application Question What are the working space and dedicated equipment space requirements for outdoor electrical equipment? Answer Per 110.26(E)(2)(a), the working clearance space includes the zone described in 110.26(A): 3-4 ft

deep, depending on the voltage and other conditions; the greater of 30 in. or the width of the equipment; and the greater of 6½ ft or the height of the equipment. The dedicated equipment space for outdoor switchboards, switchgear, panelboards, and motor control centers (equipment that is likely to require future wiring access) is the space equal to the width and depth of the equipment and extending from grade to a height of 6 ft above the equipment. Copyright 2013 by Patrick S. Ouillette, P.E.

10

200.4(B)

Use and Identification of Grounded Conductors

2014 NEC

Neutral Conductors – Multiple Circuits Significance Neutral conductors are generally not protected by overcurrent devices. It is necessary to be able to correctly identify circuit conductor pairs (grounded and ungrounded conductors of the same circuit) when splicing and terminating conductors to prevent overloading and miswiring. Analysis Where conduit raceways are used to enclose home-run conductors run into a panel, or where wireways are used near panels to transition from a cable wiring method to conduit to run into a

panel, it is not uncommon to find more than one neutral/grounded conductor in a conduit with several ungrounded conductors. This Code revision requires that grounded circuit conductors be identified or grouped in enclosures to correspond with the ungrounded conductor(s) of the same circuit. This can be accomplished by using wire markers, cable ties, or similar means in at least one location within the enclosure (all enclosures). There are two exceptions. Indentifying or grouping is not required where: (1) the branch-circuit or feeder conductors enter from a cable or raceway unique to that circuit so that the conductor association is obvious, and (2) branch-circuit conductors pass through a box or conduit body without a loop as described in 314.16(B)(1) or without a splice or termination. Some contractors have established the practice of using number labels to identify neutral conductors. Certainly this is an acceptable means of identification. This change will facilitate maintenance and troubleshooting and will help to prevent overloading of neutral conductors. Note that there is a separate existing requirement for grouping or identifying all conductors of a multiwire circuit in 210.4(D), which was new in the 2008 NEC. Multiple neutral/grounded conductors in the same raceway

Summary Where there is more than one grounded conductor within an enclosure, the grounded conductors shall be matched with their corresponding ungrounded conductors by marking, grouping, or other effective means, unless the conductor association is obvious or where conductors pass directly through the enclosure. Application Question T F This new requirement for grounded conductor identification/association applies only where there is more than one voltage system within a building. Answer False. Neutral identification where the premises wiring is supplied by more than one voltage system is a separate requirement in 200.6(D) for branch circuits and in 215.12(A) for feeders.


11

210.5(C)(2)

Branch Circuits

2014 NEC

Identification for Branch Circuits – Identification of Ungrounded Conductors – Branch Circuits Supplied from Direct-Current Systems Significance Where AC and DC circuits exist together in premises wiring, identification of circuit conductors of different systems is necessary for safety and is generally accepted wiring practice. Analysis Thomas Alva Edison’s argument for DC over Nikola Tesla’s AC remains inferior, but a resurgence in popularity of DC systems is occurring with the use of photovoltaic (PV) systems,

microgrids, low-voltage suspended ceiling power distribution systems (new Article 393), Article 411 lighting, etc. DC circuits can be used in premises wiring directly from sources without conversion power loss. The 2014 NEC has included rules to identify DC branch circuits. The new identification rules apply to ungrounded DC circuit conductors operating at more than 50 volts. Sizes 4 AWG and larger conductors shall be identified by polarity at all termination, connection, and splice points by marking tape, tagging, or other approved means. Ungrounded conductors sizes 6 AWG and smaller shall also be identified by polarity at all termination, connection, and splice points. The identification means shall be as follows: Positive Polarity, Sizes 6 AWG or Smaller • •

•

A continuous red outer finish A continuous red stripe along the length of the conductor on other than green, white, gray, or black insulation Imprinted plus signs (+) or the word POSITIVE or POS marked on an insulation color other than green, white, gray, or black at intervals not exceeding 24 inches in accordance with 310.120(B) Red insulation Red stripe on blue insulation Blue insulation

POSITIVE

POS

+

Negative Polarity, Sizes 6 AWG or Smaller • •

•

A continuous black outer finish A continuous black stripe along the length of the conductor on an insulation color other than green, white, gray, or red Imprinted minus signs (–) or the word Negative or NEG marked on other than green, white, gray, or black insulation at intervals not exceeding 24 inches in accordance with 310.120(B) Black insulation Black stripe on blue insulation Blue insulation


NEGATIVE

12

NEG

̶

210.5(C)(2)

Branch Circuits

2014 NEC

The identification means employed for conductors srcinating in each branch-circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branchcircuit distribution equipment. This posting requirement is the same as existing 210.5(C)(1)(b) for AC branch circuits. Previously, the rule in 210.5(C)(1) could have been used by the AHJ to apply to DC circuits, where more than one voltage system existed. New subsection (2) provides specific rules for DC circuits as one of the voltage systems, or where only DC circuits exist in premises wiring. In many instances, the DC circuits will be installed in existing buildings with an AC utility supply system. This new requirement for identifying ungrounded DC conductors is also applied to feeders supplied from direct-current systems in 215.12(C)(2). It has not been applied in Article 690, since Article 690 already has established rules for identifying and marking of PV cables and raceways. Summary Ungrounded branch-circuit and feeder conductors supplied from DC panelboards or similar distribution equipment shall be identified by polarity at all termination, connection, and splice points. Sizes 4 AWG and larger conductors shall be identified by marking tape, tagging, or other approved means. Ungrounded positive polarity conductors of sizes 6 AWG and smaller shall be identified by a continuous red outer finish; a continuous red stripe on insulation other than green, white, gray, or black; or imprinted plus (+) signs or the word POSITIVE. Ungrounded negative polarity conductors of sizes 6 AWG and smaller shall be identified by a continuous black outer finish; a continuous black stripe on insulation other than green, white, gray, or red; or imprinted minus (–) signs or the word NEGATIVE. The identification means shall be documented in a manner that is readily available or shall be posted at each panelboard or distribution equipment. Application Question What means of identification is required for the grounded conductor of a DC circuit? Answer For both DC branch circuits and feeders, this new identification requirement applies only to the ungrounded conductors. The requirement contains specific marking for both positive and negative polarities, but in both cases ungrounded conductors. The grounded conductor of a DC circuit is subject to the general rules for identifying grounded conductors in 200.6. Also relevant, new Section 250.167 (covered separately in this text) requires ground-fault detection systems for ungrounded DC systems and permits ground-fault detection for grounded DC systems. Section 250.167(C) requires marking to indicate the grounding type employed, i.e., ungrounded, negative or positive polarity grounded, resistance grounded, or mid-point grounded. Code Refresher Question Is there a neutral conductor in a 2-wire DC circuit (positive and negative polarity) that is not

“earthed” at any point? Answer No, regardless of whether the circuit has either polarity connected to earth. A conductor connected to earth is a grounded conductor. A 3-wire, DC system contains a neutral point (at its mid-point).


13

210.8(A)(9)

Branch Circuits

2014 NEC

Ground-Fault Circuit-Interrupter Protection for Personnel – Dw elling Units – Bathtubs or shower stalls Significance The new Code mandates expanded use of ground-fault circuit-interrupters (GFCIs) in dwelling units. Analysis All 125-volt, single-phase, 15- and 20-ampere receptacle outlets installed within 6 ft of the outside edge of a bathtub or shower stall shall be GFCI protected. This change recognizes that not all

bathtubs and showers are installed in rooms that qualify as bathrooms per the NEC definition. Where bathtubs or showers are installed in rooms or areas that require AFCI protection, both AFCI and GFCI protection are required for a receptacle within 6 ft of the tub or shower. These areas may have tile or other conductive floors that, when wet, increase the hazard of using receptacles located in the area that are not GFCI protected. Note that this change resembles existing 680.71, which requires GFCI protection for receptacles located within 6 ft horizontally of the inside walls of a hydromassage bathtub. Summary In dwelling units, all 125-volt, single-phase, 15- and 20-ampere receptacle outlets installed within 6 ft of the outside edge of a bathtub or shower stall shall be GFCI protected. Not all bathtubs and shower stalls are located in bathrooms, where GFCI protection is

already required. Application Question Does this Code change apply to guest rooms and guest suites? Courtesy of Interiorholic.com

Answer The new GFCI requirement does not apply to guest rooms and guest suites unless they qualify as dwelling units. Code Refresher  According to the NEC, a bathroom is an area that includes a basin and one or more of the following: a toilet, a urinal, a tub, a shower, a bidet, or similar plumbing fixtures.  According to the NEC, a dwelling unit is a single unit, providing complete and independent living facilities for one or more persons, including permanent provisions for living, sleeping, cooking, and sanitation.


14

210.8(A)(10)

Branch Circuits

2014 NEC

Ground-Fault Circuit-Interrupter Protection for Personnel – Dw elling Units – Laundry areas Significance Dwelling unit laundry rooms or areas have been added to the list where ground-fault circuitinterrupters (GFCIs) are required. Analysis All 125-volt, single-phase, 15- and 20-ampere receptacle outlets installed in dwelling unit laundry rooms or areas shall be GFCI protected. These circuits will also require AFCI protection (see the

change in 210.12(A)). The requirement includes all such receptacles in laundry areas, not just the receptacle that supplies a clothes washer. According to existing Section 210.11(C)(2), at least one 20-ampere branch circuit shall be provided to supply the laundry receptacle outlet(s) required by 210.52(F). This circuit shall have no other outlets. Section 210.52(F) requires that, in dwelling units, at least one receptacle outlet be installed in areas designated for the installation of laundry equipment, unless an exception applies. Laundry equipment includes clothes washers, gas clothes dryers (the 120-volt pilot, etc.), clothes irons/flatirons, etc. The principal reason for the change is that laundry areas involve electrical appliances and water, with a resulting increased risk of electric shock. Summary All 125-volt, single-phase, 15- and 20-ampere receptacle outlets installed in dwelling unit laundry rooms or areas shall be GFCI protected. Application Question

Where the laundry equipment and provisions are located in an area rather than a room, how is the border determined between laundry receptacles and receptacles that are not considered in the laundry area? Answer This will be up to the AHJ. It seems reasonable that receptacles intended for and located to serve laundry related equipment would require GFCI protection.

Code Refresher  Appliance receptacle outlets installed in dwellings for specific appliances, such as laundry equipment, shall be installed within 6 ft of the intended location of the appliance. 



[210.50(C)] A load of not less than 1500 volt-amperes shall be included for each 20-A laundry branch circuit installed in a dwelling. [220.52(B)] The load for household electric clothes dryers installed in dwellings shall be either 5000 watts (VA) or the nameplate rating, whichever is larger. [220.54]


15

210.8(B)(8)

Branch Circuits

2014 NEC

Ground-Fault Circuit-Interrupter Protection for Personnel – Other Than Dwelling Units – Garages, service bays, and similar areas other than vehicle exhibition halls and showrooms Significance This Code change expands the requirement for GFCI-protected receptacles to most types of nondwelling garages whether or not electrical hand tools or other electrical equipment are to be used. Analysis The garages covered by this rule are nondwelling garages not within the scope of Article 511,

Commercial Garages, for which GFCI protection for certain receptacles is already a requirement. Article 511 covers areas used for service and repair operations in connection with self-propelled vehicles in which volatile flammable liquids or flammable gases are used for fuel or power. A flammable liquid is any liquid that has a closed-cup flashpoint below 100°F (37.8°C). Garages for the service and repair of diesel-fueled vehicles are not within the scope of Article 511, since diesel fuel has a flash point above 100°F. DOT Maintenance Garage Jim’s RV Sales and Service

The “Volt” - Showroom

Joe’s Electric Moped Repair

Owl’s Head Transportation Museum

School Bus Garage Jerry’s Auto Detail

Mag ellan ’s GFCI Yac protection not required ht Stor

Magellan’s Yacht Storage GFCI protection required

age

This Code change applies to nondwelling unit garages (including diesel garages), service bays, and similar areas whether or not electrical diagnostic equipment, electrical hand tools, or portable lighting equipment are to be used. The diagram above shows examples of garages where the rule applies. The Code specifically exempts vehicle showrooms and exhibition halls from the GFCI requirement. See 555.19(B)(1) for GFCI requirements for Magellan’s Yacht Storage. Summary All 125-volt, single-phase, 15- and 20-ampere receptacles installed in nondwelling garages, service bays, and similar areas shall have GFCI protection for personnel. Vehicle showrooms and exhibition halls are exempt from the GFCI requirement. Application Question Does the NEC define garage? Answer Yes, in Article 100: “A building or portion of a building in which one or more self-propelled vehicles can be kept for use, sale, storage, rental, repair, exhibition, or demonstration purposes.”


16

210.8(D)

Branch Circuits

2014 NEC

Ground-Fault Circuit-Interrupter Protection for Personnel – Kitchen Dishwasher Branch Circuit Significance At some point it seems likely that whole-house GFCI and AFCI will be the norm. The change in 210.8(D) is one of the instances where the 2014 Code requires both GFCI and AFCI protection. AFCI protection is required for the entire circuit; GFCI protection is required for the appliance. Analysis GFCI protection shall be provided for outlets that supply dishwashers installed in dwelling unit

locations. GFCI devices have proven effective in reducing shock hazards and are particularly important where an electric appliance or equipment is used within reach of grounded surfaces or objects, such as metal sinks or other grounded metal appliances in kitchens. This Code change is not placed within subsection (A) of 210.8, since it address outlets rather than receptacles. The new requirement applies to both cord-and-plug connected and hard-wired dishwashers. A new AFCI requirement for kitchen circuits (including the DW circuit) is covered in Section 210.12(A). An AFCI can be used in conjunction with GFCI protection to provide both arcing fault protection and 5 mA ground-fault protection for persons. One way to provide both types of protection is to use an AFCI circuit breaker and a GFCI receptacle. AFCIs that incorporate 5 mA GFCI protection into the same package should become available in the near future. Both AFCI and GFCI devices must be installed in readily accessible locations. Visit www.AFCISafety.org for a wealth of information on arc-fault circuit interrupters and use of AFCI and GFCI on the same circuit. Summary Dishwashers in dwelling units shall be GFCI protected.

GFCI protection is required for outlets that supply dishwashers in dwelling units.

Application Question Where would you locate a GFCI receptacle that serves the dishwasher in a dwelling?

Answer Since the GFCI receptacle must be readily accessible, a standard receptacle could be located behind the dishwasher (a common practice) connected downstream from a dead-front/blank face GFCI receptacle located on the wall above the kitchen countertop. Code Refresher  For cord-and-plug-connected appliances, an accessible plug and receptacle is permitted to serve as the required disconnecting means. [422.33(A)]


17

210.12(A)

Branch Circuits

2014 NEC

Arc-Fault Circuit-Interrupter Protection – Dwelling Units Significance Whole-house protection from the effects of electric arc faults has been the goal of many entities, including the Consumer Products Safety Commission (CPSC). With expanded arc-fault circuitinterrupter (AFCI) requirements in the 2014 NEC, we’re almost there. Analysis The requirement for AFCI protection for 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets or devices in dwelling units has been expanded to include all such

circuits in kitchens and laundry areas. Many dishwasher fires have been reported, so the dishwasher circuit is a reasonable addition to the AFCI requirement. Kitchen appliance circuits, circuits for food waste disposers, lighting circuits, etc. are included in the expanded protection. The AFCI protection for the applicable laundry circuit(s) includes circuits that supply lighting and receptacle outlets in laundry rooms or laundry areas. The only 120-volt, 15- and 20-ampere branch circuits that are exempt from AFCI protection are those that supply outlets in bathrooms, garages, outdoors, and basements, except for basement rooms included in the list of rooms or areas in 210.12(A) requiring AFCI protection (e.g., laundry outlets in a basement require AFCI protection). Foyers are rooms or areas similar to hallways and should be wired to comply with the AFCI requirement. The 2014 NEC requires all AFCI devices to be installed in a readily accessible location. This will facilitate resetting and testing. Testing should be performed monthly. An AFCI receptacle installed beneath a kitchen sink cabinet to supply a food waste disposer does not meet the definition of readily accessible, “Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles….” AFCI circuit breakers are readily accessible by compliance with existing 240.24(A), which requires overcurrent devices to be readily accessible. This provision for ready access applies to all subsections of 210.12, including new subsection (C), Dormitory Units. The 2014 NEC presents six options/methods for accomplishing AFCI protection. The methods can be viewed as a systems approach to compliance. The combinations of prescribed devices and wiring methods are deemed to provide AFCI protection equal to that of combination type AFCIs, detecting and mitigating both series and parallel arc faults. Outlet branch circuit (OBC) type AFCIs are becoming available. These receptacles along with combination type and branch/feeder type AFCI circuit breakers are the AFCI components used in the systems approach to AFCI protection of branch circuits. These three devices are pictured on the following page, emphasizing the marking of the AFCI type. Each of the six options for AFCI protection is described on subsequent pages. Following the description, the system is shown in pictorial form to assist in understanding the details of the requirements.


18

210.12(A)

Branch Circuits

Siemens Q115AFC 15-amp, 1 pole, 120-volt combination type AFCI

Siemens Q115AF 15-amp, 1 pole, 120-volt branch/feeder AFCI

®

Leviton AFTR1 SmartlockPro , 15-amp, 125-volt outlet branch circuit AFCI receptacle


2014 NEC

19

210.12(A)

Branch Circuits

2014 NEC

These are the options for providing AFCI protection: (1) A listed combination type AFCI installed to provide protection for the entire branch circuit. There are no additional requirements when this method is used. The system is pictured below.

Standard receptacle outlets

Combination type AFCI breaker in panel

NM cable or other wiring method permitted by the NEC

(2) A listed branch/feeder type AFCI installed at the srcin of the branch circuit in combination with a listed outlet branch circuit (OBC) type AFCI installed at the first outlet box on the circuit. The first outlet box in the circuit shall be marked to indicate that it is the first outlet of the circuit. The system is pictured below. Marked to indicate it is the first outlet on the circuit Outlet branchcircuit type AFCI

Standard receptacle outlet

Branch/feeder type AFCI breaker in panel


(3) A listed supplemental arc protection circuit breaker installed at the srcin of the branch circuit in combination with a listed outlet branch circuit (OBC) type AFCI installed at the first outlet box on the circuit, provided the following conditions are met: (a) the branch circuit wiring is continuous from the overcurrent device to the OBC type AFCI, (b) the maximum length of the branch circuit wiring from the overcurrent device to the AFCI device does not exceed 50 ft for a

14 AWGtoconductor or 70 for first a 12outlet AWGof conductor, and (c)supplemental the first outlet box in the circuit is marked indicate that it isft the the circuit. The arc protection circuit breaker concept is being developed by the circuit breaker industry specifically for this application, based on selected requirements from UL 1699, Standard for Arc-Fault Circuit-Interrupters. The system is pictured below.


20

210.12(A)

Branch Circuits

2014 NEC

Marked to indicate it is the first outlet on the circuit Outlet branchcircuit type AFCI


Supplemental arc protection circuit breaker

NM cable or other wiring Continuous wiring, 70 ft max. for 12 AWG, 50 ft max. for 14 AWG

method permitted by the NEC

(4) A listed branch circuit overcurrent protective device (e.g., a standard circuit breaker) installed at the srcin of the branch circuit in combination with a listed outlet branch circuit (OBC) type AFCI installed at the first outlet box on the circuit, provided the following conditions are met: (a) the branch circuit wiring is continuous from the overcurrent device to the OBC type AFCI, (b) the maximum length of the branch circuit wiring from the overcurrent device to the AFCI device does not exceed 50 ft for a 14 AWG conductor or 70 ft for a 12 AWG conductor, (c) the first outlet box in the circuit is marked to indicate that it is the first outlet of the circuit, and (d) the combination of the branch circuit overcurrent device and the AFCI receptacle is identified as meeting the requirements for a “System Combination” type AFCI and is listed as such. This option introduces the concept of certifying a branch circuit overcurrent device and OBC type AFCI in specific

system combinations that have been tested and certified to comply with UL 1699 using a new outline of investigation. After this outline is developed, it will be published as UL Subject 1699C.The system is pictured below.

Marked to indicate it is the first outlet on the circuit The combination of the circuit breaker and the AFCI receptacle must be identified as meeting the requirements for a “System Combination” type AFCI.

Outlet branchcircuit type AFCI


Standard circuit breaker

Continuous wiring, 70 ft max. for 12 AWG, 50 ft max. for 14 AWG


21


210.12(A)

Branch Circuits

2014 NEC

(5) Where RMC, IMC, EMT, Type MC cable, or steel armored Type AC cables meeting the requirements of 250.118 for equipment grounding conductors, metal wireways, metal auxiliary gutters, and metal outlet and junction boxes are installed for the portion of the branch circuit between the overcurrent protective device and the first outlet, it shall be permitted to install a listed OBC type AFCI device at the first outlet to provide protection for the remaining portion of the branch circuit. Metal wireways or large junction boxes installed above panels are a convenient way to transition from horizontally run branch circuits to vertical raceways between the panels and the wireway or junction box located above the panel. As such, they become part of the raceway system for the branch circuits. The system is pictured below. Outlet branchcircuit type AFCI in metal box


Standard circuit breaker

MC cable from panelboard to AFCI receptacle or any of these methods

RMC, IMC, EMT, MC cable, steel armored AC cable, metal wireways, and metal auxiliary gutters are permitted.


(6) Where a listed metal or nonmetallic conduit or tubing or Type MC cable 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, it shall be permitted to install a listed OBC type AFCI device at the first outlet to provide protection for the remaining portion of the branch circuit. The system is pictured below.


Outlet branchcircuit type AFCI in metal box Standard circuit breaker OR RMC, IMC, EMT, or continuous run of MC cable suitable for concrete encasement can be used for the portion of the circuit not encased in concrete.

Or other wiring method permitted by the NEC

PVC encased in a minimum 2 in. of concrete. Any listed metal or nonmetallic conduit or tubing or Type MC cable suitable for encasement in concrete may be used.


22

210.12(A)

Branch Circuits

2014 NEC

Exception Where an individual branch circuit for a fire alarm system installed in accordance with 760.41(B) or 760.121(B) is installed in RMC, IMC, EMT, or steel-sheathed Type AC or MC cable meeting the equipment grounding requirements in 250.118, with metal outlet and junction boxes, AFCI protection shall be permitted to be omitted. Sections 760.41(B) for non–powerlimited fire alarm circuits and 760.121(B) for power-limited fire alarm circuits state that the fire alarm branch circuit shall not be supplied through AFCI or GFCI devices. Single- and multiplestation smoke alarms in dwellings powered by circuits that are protected by GFCI or AFCI devices shall have a secondary power source [see 29.6.3(5) of NFPA 72-2013, National Fire Alarm and Signaling Code].

“ FIRE ALARM CIRCU IT”

Panel LP

Exempt from AFCI protection Fire Alarm Control Panel

The circuit disconnecting means shall have red identification . FIRE ALARMCIRCUIT

Supply overcurrent device located in Panel LP

MC cable or any of these methods from panelboard to fire alarm control panel

Standard circuit breaker RMC, IMC, EMT, or steelsheathed Type MC or AC cable

Summary The requirement for AFCI protection for 120-volt, single phase, 15- and 20-ampere branch circuits in dwelling units has been expanded to include all such circuits in kitchens and laundry areas. The only branch circuits that are exempt from AFCI protection are those that supply outlets or devices in bathrooms, garages, outdoors, and basements, except for basement rooms included in the list of rooms or areas in 210.12(A) requiring AFCI protection (e.g., laundry outlets in a basement require AFCI protection). The 2014 NEC requires all AFCI devices to be installed in a readily accessible location to facilitate resetting and testing. The 2014 Code presents six options/methods for accomplishing AFCI protection. The methods can be viewed as a systems approach to compliance. The most common methods for providing AFCI protection for branch circuits will likely be by use of combination type AFCI circuit breakers, or by combining standard circuit breakers with outlet branch circuit type AFCIs (AFCI receptacles) as a systems approach to branch circuit AFCI protection. Application Question: When using a standard circuit breaker in combination with an OBC type AFCI to provide AFCI protection for a branch circuit installed in wood framing members, what wiring method(s) are permitted to be used between the overcurrent device and the first outlet? Answer: RMC, IMC, EMT, Type MC cable, or steel armored Type AC cable meeting the requirements of 250.118, metal wireways, metal auxiliary gutters, and metal outlet and junction boxes can be installed for the portion of the branch circuit between the overcurrent protective device and the first outlet to provide AFCI protection for the remainder of the branch circuit. Copyright 2013 by Patrick S. Ouillette, P.E.

23

210.12(B)

Branch Circuits

2014 NEC

Arc-Fault Circuit-Interrupter Protection – Branch Circuit Extensions or Modifications — Dwelling Units Significance A new exception has been added to this subsection that will help to clarify when AFCI requirements are applicable to circuit extensions or modifications to existing wiring. Analysis The new exception states that the AFCI requirement is not applicable for dwelling unit branch circuit extensions, where the circuit extension is not more than 6′ in length and no additional

outlets or devices are added to the circuit. When an existing panel is replaced or upgraded, the branch circuit wiring is not always long enough to connect to the panel overcurrent devices. The exception will allow existing branch circuits to be spliced and extended up to 6′ in cable length without requiring AFCI protection for the branch circuits. This will accommodate panels being moved out of clothes closets and bathrooms, service panels (during service upgrades) being moved closer to where the service-entrance conductors penetrate the outside wall of a building, panels being moved to readily accessible locations, and other situations. The existing AFCI requirement remains the same. In any of the areas specified in 210.12(A), where branch-circuit wiring is extended, modified, or replaced, the branch circuit shall be protected by either • •

A listed combination-type AFCI located at the srcin of the branch circuit, or A listed outlet branch-circuit type AFCI device located at the first receptacle outlet of the existing branch circuit.

This subsection applies also to kitchens and laundry rooms or areas, since these rooms have been added to the list in 210.12(A). The AFCI devices must meet the new requirement at the beginning of 210.12 for ready access. Summary AFCI requirements are not applicable to dwelling unit branch circuit extensions, where the circuit extension is not more than 6′ in length and no additional outlets or devices are added to the existing branch circuit. Application Question Statistics show that the majority of electrical fires occur in older homes. How does this exception promote enhanced safety of older circuits that would be better protected by AFCI devices?


24

210.12(B)

Branch Circuits

2014 NEC

Answer It doesn’t. However, it does encourage other safety enhancements like moving panels to Codecompliant locations, upgrading from fuses to circuit breakers, or increasing the size of an overloaded service (all of which may require circuit extensions), without necessitating the extra cost of AFCI devices. For some, particularly in hard economic times, this extra cost could be a deterrent from making a service or panel upgrade, or from moving a panel. Note that the exception does not apply to circuit modifications or replacements—only short extensions of existing branch circuits, where no outlets or devices are added. Technical Update

You may be wondering how an AFCI receptacle installed at the first receptacle outlet on an existing circuit compares with a combination-type AFCI circuit breaker in terms of protection of the entire branch circuit. Outlet branch-circuit (OBC) type AFCIs provide both upstream and downstream protection from series arc faults, but provide only downstream protection from parallel arc faults. So, how is the “home run” (that portion of a circuit from the overcurrent device to the first outlet) protected against parallel arcing faults? Studies have shown that the home run portion of a circuit is, on average, approximately 35% of the total branch circuit length. The magnetic trip (instantaneous) function of a conventional circuit breaker will usually clear a parallel arcing fault in the portion of the circuit from the circuit breaker to the AFCI receptacle. This is contingent on the available fault current at the panel being high enough (approximately 500 A), the instantaneous trip value of the circuit breaker being low enough (less than 200 A), and a low conductor impedance from the circuit breaker to the location of the fault. The conductor impedance depends on the conductor length, size, and material. These parameters were used in writing some of the options in 210.12(A). The home run of a circuit is generally less vulnerable to a fault, being enclosed by construction and not containing splices or cord extensions. The home run conductors are continuous from the circuit breaker to the AFCI device, except perhaps for a switch outlet in an existing branch circuit that could be between the circuit breaker and the AFCI receptacle. In existing NM cable installations, the AFCI receptacle option cannot be guaranteed to provide equivalent protection to that of a combination-type AFCI installed at the srcin of the circuit. Only the options in 210.12(A) provide combination-type AFCI protection or its equivalent. Note that options (5) and (6) of 210.12(A) require more robust protection for the home run than Type NM cable affords.


25

210.12(B)

Branch Circuits

2014 NEC

Install combination-type AFCI circuit breaker in panelboard or install outlet branch-circuit type AFCI here. Branch-circuit extension 120-V, 15- or 20-A existing branch circuit in dwelling unit panelboard

R

Any room or area specified in 210.12(A), where branchcircuit wiring is modified, replaced, or extended

Sectio n 210.12 (B), general ru le, 2011 a nd 2014

120-V, 15- or 20-A existing branch circuit in dwelling unit panelboard Circuit extension not more than 6

′

R

No AFCI protectio n required Relocated panelboard

Existing panelboard

Any room or area specified in 210.12(A), where branchcircuit wiring is modified, replaced, or extended

Section 210.12(B), Excepti on, 2014


26

NEC

NEC

210.12(C)

Branch Circuits

2014 NEC

Arc-Fault Circuit-Interrupter Protection – Dormitory Units Significance A new subsection has been added to the requirement for AFCI protection of certain branch circuits. Analysis This new subsection addresses AFCI protection for certain branch circuits in dormitory units. All 120-volt, single phase, 15- and 20-ampere circuits installed to supply outlets in dormitory unit living rooms, bedrooms, hallways, closets, and similar rooms now require AFCI protection using

any of the methods in (1) through (6) of 210.12(A). In a typical dormitory room, all branch circuits will require AFCI protection. Some living facilities for students at colleges and other institutions are apartments rather than dormitories. They qualify as dwelling units per the definition of dwelling unit and must be wired as such. As used in this subsection, dormitory unit does not envision a bathroom or cooking provisions within the dormitory unit (compartment). A portable microwave oven does not constitute permanent provisions for cooking.

AFCI protection in dormitory units

The AFCI protection requirement now includes dormitory units.

Summary All 120-volt, single phase, 15- and 20-ampere circuits installed to supply outlets in dormitory unit living rooms, bedrooms, hallways, closets, and similar rooms require AFCI protection using any of the methods in (1) through (6) of 210.12(A).


27

210.12(C)

Branch Circuits

2014 NEC

Application Question Does this new AFCI requirement apply to modification, extension, or replacement of branch circuit wiring in existing dormitory units? Answer: No. It applies only to newly installed branch circuits that require AFCI protection. Code Refresher  Receptacle placement in dormitory units is permitted to accommodate permanent furniture layout, but the quantity of receptacles installed must be in accordance with 210.52(A) for dwelling units. At least two receptacle outlets shall be readily accessible. Where receptacles are installed behind a bed, the receptacle shall be located to prevent the bed from contacting any attachment plug that may be inserted or the receptacle shall be provided with a suitable guard. [210.60]


28

210.13

Branch Circuits

2014 NEC

Ground-Fault Protection of Equipment Significance This new section will not find wide use but is significant because it involves an expansion of the ground-fault protection of equipment (GFPE) requirement. Analysis New Section 210.13 requires that each branch circuit disconnect rated 1000 A or more and installed on solidly grounded wye electrical systems operating at more than 150 volts to ground, but not exceeding 600 volts phase-to-phase, be provided with GFPE in accordance with the

provisions of 230.95. This protection is designed to limit damage to conductors and equipment when a fault occurs. Each ground-fault protection system must be performance tested and documented in accordance with the requirements in 230.95(C). A 1000 amp branch circuit is rare, but could exist in industrial settings. The new section includes an informational note and two exceptions that are essentially the same as follows Section 215.10, which address GFPE for feeders. The informational note reminds Code users that 517.17 must be considered for buildings that contain health care occupancies. Exception No. 1 addresses a continuous industrial process where a nonorderly shutdown will introduce additional or increased hazards. Exception No. 2 waives the GFPE requirement where GFPE is installed on the supply side of the branch circuit and on the load side of any transformer that supplies the branch circuit.

Summary Each branch circuit disconnect rated 1000 A or more and installed on solidly grounded wye electrical systems operating at more than 150 volts to ground, but not exceeding 600 volts phaseto-phase, shall be provided with ground-fault protection of equipment. Application Question T F

A GFPE device will protect persons from shock hazard.

Answer False. A 5 mA-trip GFCI (Class A) device is designed to protect persons from electric shock. GFPE devices are available that trip at ground faults of 30 mA and higher.


29

210.17 (and Article 625)

Branch Circuits

2014 NEC

Part I. General Provisions – Electric Vehicle Branch Circuit Significance This is a new section providing rules for branch circuits for electric vehicle charging equipment. Analysis An outlet(s) installed to supply electric vehicle charging equipment shall be supplied from a separate branch circuit. This branch circuit shall not supply any other outlets (other than electric vehicle charging equipment). This is not the same as requiring an individual branch circuit, which by definition can supply only one utilization equipment. Note that this new section does not fall

within Part III. Required Outlets, therefore a receptacle for electric vehicle charging equipment is not required to be installed. The charging equipment is considered a continuous load. The load must be calculated at 125% of the rated load. This can be a significant load and could affect the adequacy of an existing service. There is a related change in 625.41, which states that where an automatic load management system is used, the maximum electric vehicle supply equipment load on a service and feeder shall be the maximum load permitted by the automatic load management system. Article 625 – Electric Vehicle Charging System has undergone a total re-write. The most significant changes are more detailed rules pertaining to supply cords and receptacles for electric vehicle charging equipment and cords between the charging equipment and the vehicle. Summary If an outlet(s) is installed to supply electric vehicle charging equipment, it shall be supplied by a separate circuit that has no other outlets. The load shall be 125% of the rated load or the maximum permitted by an automatic load management system. Application Question T F A receptacle for the connection of electric vehicle charging equipment is required to be installed for all new dwellings. Answer False. It is not a required outlet. Courtesy of Leviton Manufacturing Co., Inc. Cord-connected electric vehicle charging station 16-A, 240-V, 3.8 kW output


30

210.19(A)(1) Branch Circuits

215.2(A)(1) Feeders

2014 NEC

Conductors—Minimum Ampacity and Size – Branch Circuits Not More Than 600 Volts Minimum Rating and Size – Feeders Not More Than 600 Volts Significance These revisions are intended to provide clarity on sizing conductors that supply continuous loads. Analysis The existing Code language in 210.19(A)(1) for branch circuits and 215.2(A)(1) for feeders has caused confusion in their application. Code users have found it difficult to interpret the Code rules for wire sizing, where continuous loads and adjustment or correction factors are involved.

The 2014 revision to these sections attempts to clarify the application of these rules. Two separate calculations are specified, and conductors are sized based on the larger of the two resulting conductor sizes, where the separate calculations result in different conductor sizes. Conductors shall be not smaller than the larger of the sizes calculated in accordance with subsections (a) or (b) of 210.19(A)(1) or 215.2(A)(1) as applicable. (a) Where a branch circuit or feeder supplies continuous loads or a combination of continuous and noncontinuous loads, the minimum conductor size shall have an ampacity not less than the noncontinuous load plus 125 percent of the continuous load. (b) The minimum branch-circuit or feeder conductor size shall have an ampacity not less than the maximum load to be served after the application of any adjustment or correction factors. Example A 3-phase, 4-wire feeder supplies a continuous, nonlinear lighting load of 60 amperes. The feeder circuit conductors are installed in EMT. The conductors that will be used are rated 90°C.

Terminations are rated 75°C. What size aluminum conductors are required to supply the load? Calculations based on subsection (a): 60 x 1.25 = 75 A (minimum required conductor ampacity) From Table 310.15(B)(16): A 3 AWG aluminum conductor is permitted (75 A, 75°C column). Calculations based on subsection (b): The second paragraph of Section 310.15(B) permits applying adjustment or correction factors to the table ampacity listed for the conductor insulation, provided the adjusted or corrected ampacity does not exceed the ampacity listed for the temperature rating of the terminations in accordance with 110.14(C). From Table 310.15(B)(3)(a): Adjustment for four current-carrying conductors = 80% or 0.80 From Table 310.15(B)(16): The 90°C ampacity for a 3 AWG aluminum conductor is 85 A. 85 A x 0.80 = 68 A (adjusted ampacity for a 3 AWG aluminum conductor rated 90°C) 2 AWG aluminum conductors rated 90°C are required. Summary There is a change in the method of sizing branch-circuit and feeder conductors where a portion of the load, or the entire load, is continuous, and adjustment or correction factors, or both, are required to be considered.


31

210.52(E)(1) and (E)(2)

Branch Circuits

2014 NEC

Dwelling Unit Receptacle Outlets – Outdoor Outlets – One-Family and Two-Family Dwellings – Multifamily Dwellings Significance This change now permits an interpretation of Code that some electrical inspectors have already been using for locating the required outdoor receptacles at dwellings. Analysis Rather than “accessible while standing at grade level” the required outdoor receptacles for dwelling units are now permitted to be “readily accessible from grade.” In the 2011 NEC, in order

for a receptacle located on a deck or open porch with steps to grade to serve as one of the required outdoor receptacles, the receptacle had to be located near enough to the edge of the deck or porch to be reached while standing at grade level. The 2014 Code allows a receptacle that is readily accessible from grade and located on a deck or porch to serve a twofold purpose: as one of the required outdoor receptacles, and as the required receptacle for decks and porches in 210.52(E)(3). Where a deck or porch exists, most outdoor receptacle use will be for electrical equipment on the deck or porch. Where a deck or porch is covered (damp location), this new permission will enable safer use of outdoor outlets by avoiding locating a receptacle in a wet location. Of course, additional outlets accessible while standing at grade level can be installed.

Receptacles readily accessible from grade

The rule is essentially the same for multifamily dwellings. For each unit at grade level and provided with individual exterior entrance/egress, at least one receptacle readily accessible from grade and not more than 6½ ft above grade level is required. Summary The required outdoor receptacles for one-family dwellings, each grade-level unit of two-family dwellings, and for each grade-level unit of multifamily dwellings with individual exterior entrance/egress, the required outdoor receptacle outlet(s) shall be readily accessible from grade and not more than 6½ ft above grade level. Application Question: If one of the required outdoor receptacles is on a deck or porch with steps to grade, is there a maximum height or number of steps that would make this deck or porch receptacle not qualified to serve as a required outdoor receptacle? Answer: The Code substantiation suggested “not up more than a few steps.” The receptacle cannot be more than 6½ ft above grade level. One interpretation is that the receptacle cannot be more than 6½ ft above the level of the deck or porch walking surface as in 210.52(E)(3).


32

210.52(E)(3)

Branch Circuits

2014 NEC

Dwelling Unit Receptacle Outlets – Outdoor Outlets – Balconies, Decks, and Porches Significance The new Code allows flexibility in locating outdoor receptacles to serve holiday lighting and other loads at small decorative balconies, decks, and porches. Analysis In the 2011 NEC, a receptacle was required to be located within the perimeter of a dwelling unit balcony, deck, or porch, where this area was accessible from inside the dwelling unit. For small decorative balconies, it proved difficult to locate the receptacle within the perimeter of the

balcony, since doors often spanned most or all of the available exterior wall space. This change permits the required 125-volt, 15- or 20-ampere receptacle to be installed at a location that is accessible from the balcony, deck, or porch. As in the previous Code, the receptacle cannot be located more than 6½ ft above the balcony, deck, or porch walking surface. This subsection also has been revised to apply only to decks and porches that are dwelling unit.

attached to

the

Receptacle accessible from balcony

Summary Balconies, decks, and porches that are accessible from inside the dwelling unit shall have at least one receptacle outlet accessible from the balcony, deck, or porch. The receptacle outlet shall not be located more than 6½ ft above the walking surface of the balcony, deck, or porch. Application Question Besides the requirements in this section, what other rules apply to an outdoor receptacle for a balcony, deck, or porch of a dwelling unit? Answer The receptacle must be GFCI protected [210.8(A)(3)], tamper resistant [406.12(A)], be a listed weather-resistant (WR) type, and be equipped with a weatherproof enclosure suitable for either a damp or wet location, whichever is the case [406.9(A) and (B)(1)].


33

210.52(G)(1)

Branch Circuits

2014 NEC

Dwelling Unit Receptacle Outlets – Basements, Garages, and Accessory Buildings – Garages Significance Most new single-family dwellings include 2- or 3-car garages. This has prompted a change to the receptacle requirement for residential garages. Analysis The rule requiring only one receptacle for a single-family garage, in addition to any receptacles required for specific equipment, is outdated. Garage space has become larger and has seen uses in

addition to vehicle parking, such as recreational vehicle storage, workshops, home hobbies, etc. If only one receptacle is available in a multicar garage, odds are good that extension cords will be needed for car cleaning and other maintenance, and for a host of do-it-yourself projects. The 2014 Code requires at least one receptacle for each car space/lane. Each required receptacle should be placed to conveniently serve a vehicle space. The circuit(s) for this receptacle(s) is not permitted to supply outlets outside of the garage. This rule will also help to accommodate the increase in use of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs). A Level 1 EV charger is supplied from a standard 125-volt receptacle (16 A maximum on a 20-A circuit). If it is known that the garage will be used for an electric vehicle, a separate branch circuit for charging should be installed in accordance with new Section 210.17.

This 3-car garage requires a minimum of three receptacles, in addition to any receptacles required for specific equipment.

Summary For a single-family dwelling attached garage, or a detached garage with electric power, at least one receptacle outlet shall be installed for each car space, in addition to any receptacles provided for specific equipment. The branch circuit(s) supplying this receptacle(s) shall not supply outlets outside of the garage. Application Question Can the circuit supplying the receptacles for car spaces also serve garage lighting? Answer Yes. It can supply lighting outlets within the garage. It is not clear whether lighting and receptacle outlets on the outdoor side of the exterior garage wall can be supplied. Copyright 2013 by Patrick S. Ouillette, P.E.

34

210.64

Branch Circuits

2014 NEC

Part III. Required Outlets – Electrical Service Areas Significance A convenience receptacle is required at electrical service areas. Analysis This is a new section in 2014 that requires at least one 125-volt, single-phase, 15- or 20-ampererated receptacle outlet to be installed within 50 ft of the electrical service equipment. The outlet is not required in one- and two-family dwellings. The purpose is to accommodate electrical data acquisition and other test equipment and to facilitate maintenance, without the need to run

extension cords into adjacent rooms or areas. The rule is not limited to indoor installations of service equipment. Indoor service equipment room

Outdoor service equipment

GFCI

The electrical equipment in a separate building supplied from another building is not service equipment and is not subject to the new requirement. The separate building might contain an electric room where a feeder enters the building, but the rule pertains only to an electric room that contains the electrical service. A feeder electrical entrance into a building is covered in Art. 225. New Section 210.64 is similar to the existing requirement in 210.63, which requires a convenience receptacle located on the same level and within 25 ft of heating, air-conditioning, and refrigeration (HVAC) equipment. Summary For other than one- and two-family dwellings, at least one 125-volt, single-phase, 15- or 20ampere-rated receptacle outlet shall be installed within 50 ft of the electrical service equipment to accommodate electrical data acquisition and other test equipment and to facilitate maintenance. Application Question Does the required receptacle have to be located in the electrical service room? Answer Interestingly no. Most electrical rooms do not measure 50 ft in any direction! Ask the AHJ.


35

220.12, Exc.

Branch-Circuit, Feeder, and Service Calculations

2014 NEC

Part II. Branch-Circuit Load Calculations – Lighting Load for Specified Occupancies – Exception Significance The 2014 NEC has made provisions to permit the lower general lighting load allowance specified by energy codes. States must adopt specified model energy codes or their equivalent. Analysis Two popular model energy codes, ASHRAE/IES 90.1-2010, Energy Standard for Buildings Except Low-Rise Residential Buildings and IECC 2012, International Energy Conservation Code

contain standards for energy reduction and efficiency, including standards for lighting. A key concept of energy codes is the limit that is set on lighting power density (LPD, measured in watts/ft2). Automatic lighting controls are also a major component of energy codes. The LPD values have decreased over the years with implementation of increasingly efficient lighting technologies. Smaller electrical services will result in cost savings and reduced levels of fault current and arc flash energy; smaller transformers will reduce the amount of lost energy. Section 220.12 specifies the minimum lighting load for specified occupancies. Where a municipality has adopted an energy code, the lighting load allowed by that energy code will be significantly less than that permitted in the NEC. For instance, the typical energy code LPD for offices is .9 W/ft 2, 1.4 W/ft2 for retail occupancies, and .6 W/ft2 for warehouse buildings. Example: Retail store lighting load calculation: 40 ft x 60 ft = 2400 ft 2 total floor area

NEC Energy code

2400 x 3 VA = 7200 VA 2400 x 1.4 W/ft2 = 3360 W, a 53% reduction from the NEC value

The NEC contains a new exception that permits use of the lighting load value determined in accordance with an adopted energy code provided that: 1. A power monitoring system is installed that will provide continuous information regarding the total general lighting load of the building, 2. The power monitoring system is set with alarm values to alert the building owner or manager if the lighting load exceeds the values set by the energy code, and 3. The demand factors in 220.42 are not applied to the general lighting load. Summary The general lighting load is permitted to be calculated according to the adopted energy code in lieu of the values specified in 220.12 of the NEC, where the load is continuously monitored and the building manager will be alerted if the load exceeds the value set by the energy code. The demand factors in 220.42 may not be applied to the general lighting load. Application Question

For a 1000 ft 2 office, what is the difference in the lighting load allowance between the NEC and typical energy codes? Answer 2600 VA. (1000 x 3.5) – (1000 x .9) = 3500 – 900 = 2600 VA.


36

240.87

Overcurrent Protection

2014 NEC

Part VII. Circuit Breakers – Arc Energy Reduction Significance Section 240.87 was introduced in the 2011 Code and has been revised in the 2014 Code cycle. It contains rules for reducing incident energy caused by arcing fault currents. Analysis Where the highest continuous current trip setting for which an overcurrent device installed in a breaker is rated (or can be adjusted to) is 1200 amps or higher, one of the means listed below shall be provided to reduce clearing time. Documentation as to the location of the circuit breaker shall be available to those authorized to design, install, operate, or inspect the installation.

1. Zone-selective interlocking – Upstream and downstream circuit breakers communicate with each other and determine whether the upstream breaker should trip without intentional delay or after a preset time delay, depending on the location of the fault. 2. Differential relaying – The current flowing into the upstream breaker is compared with the current flowing out of the downstream breaker. Under normal conditions, the difference is zero. A fault between the upstream and downstream breakers will result in a difference current that will reach the level of a preset setting and cause the upstream breaker to trip without delay. 3. Energy-reducing maintenance switching with local status indicator – A worker can set the trip unit to “no intentional delay” whenever working within the flash protection boundary, and then back to the normal setting when finished. 4. Energy-reducing active arc flash mitigation system (a new option in the 2014 Code) – Helps in reducing arcing duration in the electrical distribution system. No change in the circuit breaker or the settings of other devices is required during maintenance when a worker is working within an arc flash boundary. (Arc Flash Boundary is defined in NFPA 70E, Standard for Electrical Safety in the Workplace.) 5. An approved equivalent means – This allows for new technology and innovation. Digitrip 520MC, Model 5ARMLSIG trip unit for a Magnum DS Power Circuit Breaker Courtesy of Eaton Corporation and BREAKER OUTLET Circuit Breakers

“Maintenance Mode” “Arc Flash Reduction Setting”

Summary Where the highest continuous current trip setting for which an overcurrent device installed in a breaker is rated (or can be adjusted to) is 1200 amps or higher, an approved means shall be employed to reduce clearing time. Application Question Does an instantaneous trip function in a circuit breaker meet the requirements in this section? Answer Yes. However, this is not clear in the actual text of the NEC. It seems the intent is for this rule to apply only where the breaker is (1) intentionally delayed under short-circuit conditions, and (2) does not have an instantaneous trip function, and (3) does not have an instantaneous override, or the instantaneous override is set higher than the potential arcing current. Copyright 2013 by Patrick S. Ouillette, P.E.

37

250.64(B)

Grounding and Bonding

2014 NEC

Grounding Electrode Conductor Installation – Securing and Protection Against Physical Damage Significance This change will clarify the requirements for installing grounding electrode conductors and grounding electrode bonding jumpers underground. Analysis Table 300.5 Minimum Cover Requirements, 0 to 1000 Volts, Nominal, Buried in Millimeters (Inches) contains cover depths for various wiring methods installed in seven location categories.

Direct burial cables and conductors must be buried 18 in. or 24 in., depending on the location of the wiring. This Code revision clarifies that this requirement does not apply to grounding electrode conductors (GECs) or grounding electrode bonding jumpers connecting to any type of qualified grounding electrode(s). The intent may have been to exempt GECs and grounding electrode bonding jumpers from only the cover requirements in 300.5(A), but the Code language is “Grounding electrode conductors and grounding electrode bonding jumpers shall not be required to comply with 300.5.” Section 300.5 contains many subsections. Some of these subsections are clearly not applicable, while (F) Backfill contains requirements for proper underground raceway and cable installations.

Cover requirements in 300.5 are not applicable.

Physical protection for GECs

Grounding electrode conductors Bonding jumper Soil 250.52(A)(8) “Other local metal underground systems or structures”

Summary Grounding electrode conductors and grounding electrode bonding jumpers are not required to comply with Section 300.5. Application Question Section 300.5(D)(1) Emerging from Grade requires protective enclosures or raceways down to the minimum cover depth in Table 300.5 for direct-buried conductors emerging from grade. Does this provision apply to GECs? Answer No. Since the depth requirement is not applicable, neither is the protective enclosure required to extend down to the Table 300.5 depth. This is one of the items that the Code panel is attempting to clarify. Section 250.64(B) provides for protection against physical damage for GECs.


38

250.66(A) and (B)


2014 NEC

Size of Alternating-Current Grounding Electrode Conductor – Connections to a Rod, Pipe, or Plate Electrode(s) – Connections to Co ncrete-Encased Electrodes Significance This revision seeks to clarify the meaning of “sole connection” to a grounding electrode. Analysis The size of the ac grounding electrode conductor (GEC) is based on the size of the serviceentrance conductors, or equivalent area for parallel conductors, and the effectiveness of the grounding electrode(s) the electrical system is connected to. The resistance to earth of a ground

rod is generally thatonly for underground Consequently, a ground rod, or pair of groundhigher rods, than requires a 6 AWG Cumetal GEC,water whilepiping. the GEC that connects to underground metal water piping could be required to be as large as 3/0 Cu, depending on the size of the service-entrance conductors. Generally, the “sole connection” to an electrode is the only connection to the electrode—the electrode is not used to interconnect electrodes. The GEC connection to the ground ring, concrete-encased electrode, and ground rods in the diagram below is the sole connection to these electrodes. Connection to a single or multiple rod, pipe, or plate electrode(s) still only requires a 6 AWG Cu GEC to the first electrode in the sequence or between electrodes. The same is true where more than one concrete-encased electrode is used—4 AWG to the first electrode and between electrodes. Sole connection has a different meaning for these electrodes. 2 Cu (size of gr. ring)

800-A service equipment – parallel 500 kcmil copper conductors, 75°C rated

20 ft min., 2 AWG Cu min.

Ground ring

2/0 Cu

Metal underground water pipe

N 10 ft min.

6 Cu

2/0 Cu

6 Cu

4 Cu

8 ft min. rods

At least 20 ft of ½ in. min. re-bar or 4 AWG min. Cu

Summary Connection to a single or multiple rod, pipe, or plate electrode(s), or to a single or multiple concrete-encased electrode(s) does not increase the size of the minimum required GEC specified

for these electrodes. The “sole connection” sizing provisions are not forfeited. Application Question: In the above diagram, is the 6 AWG Cu that connects from the water pipe to the ground rod the sole connection to the rod? Answer: Yes. For the purpose of sizing GECs in 250.66, it is considered the sole connection. Copyright 2013 by Patrick S. Ouillette, P.E.

39

250.68(C)(2)


2014 NEC

Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes – Grounding Electrode Connections Significance The structural metal frame of a building can serve several grounding and bonding functions. Analysis The structural metal frame of a building is permitted to be used as a conductor to interconnect electrodes of the grounding electrode system or as a grounding electrode conductor (GEC), regardless of whether the metal frame itself qualifies as a grounding electrode. In the 2011 Code,

the building frame had to qualify as a grounding electrode, by connection to a grounding electrode, in order to be used to interconnect electrodes or as a GEC. The change seems inconsequential, though, since using building steel to connect to a grounding electrode or to interconnect electrodes qualifies the building as an electrode according to the 2011 NEC. Remember that the NEC is not a design manual [90.1(A)]. The effectiveness of the building steel fault path must be considered, e.g., joints between steel members, length of fault path, etc.

Service equipment

. R G . P I U Q E

L A R T U E N

The structural metal frame of a building is permitted to be used as a conductor to interconnect electrodes of the grounding electrode system or as a grounding electrode conductor.

Metal underground water pipe

Grounding electrode

Summary The structural metal frame of a building is permitted to be used as a conductor to interconnect electrodes of the grounding electrode system or as a grounding electrode conductor, regardless of whether the metal frame itself qualifies as a grounding electrode. Application Question Does the first 5 ft of metal water piping, from the point of entrance into a building, have to qualify as a grounding electrode in order to be used to interconnect grounding electrodes? Answer No. The underground water service piping could be non-conductive and the rule will still apply. The rule is the same for the structural metal frame of a building. Code Refresher  In other than dwelling occupancies, exposed metal water piping can be used to interconnect electrodes or as a GEC. The 5 ft limitation does not apply. [250.68(C)(1), Exc.] Copyright 2013 by Patrick S. Ouillette, P.E.

40

250.68(C)(3)


2014 NEC

Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes – Grounding Electrode Connections – A concrete-encased electrode… Significance This change provides guidance and clarification concerning a permitted method for connecting to a concrete-encased electrode. Analysis The lack of bonding an available concrete-encased electrode to the grounding electrode system is a common NEC violation in some jurisdictions. If the wireman does not expect to be on site

before concrete pouring, he should make arrangements with the general contractor or concrete contractor to provide a means for connecting the service neutral to the concrete-encased electrode. This Code change clarifies that a reinforcing bar or copper wire type concrete-encased electrode installed in accordance with 250.52(A)(3) can be extended from the location within the concrete to an accessible location above the concrete to accommodate connection to the service.

The reinforcing bar extension (or “stub-up”) or copper conductor should exit the concrete in a location protected from the weather. The American Concrete Institute Standard 318 (ACI 318), Building Code Requirements for Reinforced Concrete , requires a certain thickness of concrete protection over structural reinforcing bars for reinforced concrete surfaces exposed to weather or in direct contact with earth. The portion of a structural reinforcing bar protruding from the concrete wall to facilitate connection to the electrical service neutral is not performing a structural function, but should be protected from corrosion to ensure the integrity of the electrical connection.

This 4 AWG copper grounding electrode conductor is connected to reinforcing bars in the concrete footing and emerges at the top of the concrete foundation wall through the hole in the wood sill plate.

This 4 AWG copper grounding electrode conductor connects to the neutral bus in the service panel directly above, passes through the clamp in the box out at the top of the concrete wall, then connects to ground rods.


41

250.68(C)(3)


2014 NEC

Summary A concrete-encased electrode of either the conductor type or reinforcing bar, extended from the location within the concrete to an accessible location above the concrete wall, is a permitted method for facilitating the grounding of the service neutral to the concrete-encased electrode. Application Question Where a concrete-encased electrode consists of a minimum of 20 ft of copper conductor, or where a copper conductor is connected to reinforcing bars in a concrete footing and run to a location above the concrete wall, what minimum conductor size is required? Answer The minimum required size is 4 AWG copper. More on Concrete-Encased Electrodes (Ufer ground) The National Electrical Code permits grounding electrodes consisting of concrete-encased reinforcing bars or at least 20 ft of bare copper not smaller than 4 AWG placed near the bottom of a foundation footing, or placed horizontally or vertically in a foundation wall. The concrete wall must be in contact with earth for the encased steel or copper to be an effective grounding means. This rules out any portion of the concrete electrode that is above grade. Also, that area of the concrete-encased electrode in contact with frozen ground or dry ground is less effective for grounding. Hence, the preferred location of reinforcing steel or bare copper is near the bottom of a support foundation footing. When a foam or plastic barrier is placed between the concrete-encased steel or copper and earth, the installation does not qualify as a concrete-encased electrode. Other barriers and coatings may also prevent direct contact between concrete and earth. Code Refresher  The NEC permits a 6 AWG copper grounding electrode conductor for connection to a rod, pipe, or plate electrode regardless of the size of the ungrounded service conductors. This is due to the fact that the rod-to-earth contact resistance and the earth resistance will limit any current to earth to a level that can be safely carried by the 6 AWG copper. For certain size services, the minimum required size for GECs that are the sole connection to rod, pipe, or plate electrodes, concrete-encased electrodes, and ground rings is smaller than specified in Table 250.66. The GEC size specified in Table 250.66 shall not be reduced when the grounding electrode is a metal underground water pipe, the metal frame of a building, other listed electrodes (see the listing requirements), and other local metal underground systems or structures (e.g., a well casing). The largest GEC required by the Code for any size service is 3/0 copper.

Even though a 3/0 copper conductor is the largest GEC required by Code, there is no upper limit on the required size of the equipment grounding conductor. An equipment grounding conductor performs a different function than a grounding electrode conductor. Note that a 3/0 copper equipment grounding conductor is suitable for equipment supplied by a 1200-amp overcurrent device. For circuits of higher rating, a larger equipment grounding conductor is required in accordance with Table 250.122.


42

Table 250.102(C)


2014 NEC

Bonding Conductors and Jumpers – Size – Supply-Side Bonding Jumper Significance Instead of using Table 250.66 for sizing supply-side bonding jumpers and certain grounded conductors, new Table 250.102(C) has been added to the NEC for this purpose. Analysis In the 2011 and previous Code editions, several sections referenced Table 260.66 for sizing jumpers and grounded conductors on the supply side of a service disconnecting means or the first disconnecting means for a separately derived system. These conductors and jumpers form the link

between the equipment grounding conductors and the neutral/grounded conductor for the faultclearing path. Correct sizing is important, since these conductors may be called upon to carry significant fault current. The reference to “supply side” means that there is no overcurrent device upstream except for the utility’s overcurrent device. In the case of separately derived systems, however, there may be an overcurrent device installed upstream that is within the purview of the NEC, e.g., the primary OCPD for a transformer- supplied separately derived system. Revised Section 250.28(D)(1) now refers the Code user to Table 250.102(C) for sizing the main bonding jumper and system bonding jumper. Section 250.24(C)(1) refers the user to the new table for the minimum size of the grounded conductor required to be run to the first disconnecting means. Section 250.30(A)(3)(a) contains a similar requirement that applies to separately derived systems. Sections 250.102(C)(1) and (C)(2) have been revised to reflect the change, and Section 250.102(C)(3) has been deleted and replaced by Note 2 to the new table. Note 1 to Table 250.102(C) specifies a multiplier of 0.125 (12½%) for sizing grounded conductors and bonding jumpers for supply conductors over 1100 kcmil copper and 1750 kcmil aluminum. Note 2 provides requirements for sizing conductors and jumpers where the ungrounded supply conductors are of different materials (copper, aluminum, or copper-clad aluminum) than the jumpers. Notes 3 and 4 explain how to perform the sizing where there are multiple sets of ungrounded supply conductors or no supply conductors, e.g., busway. The change is appropriate, since the title of Table 250.66 is “Grounding Electrode Conductor for Alternating-Current Systems.” The grounding electrode conductor (GEC) connects to earth and performs a very different function that the conductors and jumpers addressed in the new table. A GEC is not intended to serve as a fault-clearing conductor. Also, the largest size copper and aluminum GECs required by Table 250.66 are 3/0 and 250 kcmil respectively, which is smaller than what is required for some supply-side jumpers and grounded conductors. Summary Previous Code references to Table 250.66 for sizing supply-side bonding jumpers and certain grounded conductors now refer to new Table 250.102(C). These include sizing for grounded conductors run to the first disconnecting means for utility services and separately derived systems (even when no neutral loads are supplied), and for the main bonding jumper and system bonding jumper.


43

Table 250.102(C)


2014 NEC

Application Question: What minimum size copper main bonding jumper is required to connect the neutral bar to the equipment grounding bar of a switchboard rated 1600 A? The switchboard is supplied with four sets of 600 kcmil copper conductors in parallel. Answer: 300 kcmil copper (4 x 600 kcmil = 2400 kcmil; 2400 x 0.125 = 300) Table 250.102(C) Grounded Conductor, MainBonding Jumper, System Bonding Jumper, and Supply-Side Bonding Jumper for Alternating-Current Systems a

For the purposes of this table, the term bonding jumper refers to main bonding jumpers, system bonding jumpers, and supply-side bonding jumpers.

Size of Largest Ungrounded Conductor or Equivalent Area for Parallel Conductors (AWG/kcmil) Copper Aluminum or Copper-Clad Aluminum 2 or smaller 1 or 1/0 2/0 or 3/0 Over 3/0 through 350 Over 350 through 600 Over 600 through 1100 Over 1100

Size of Grounded Conductor or Bonding Jumpera (AWG/kcmil) Copper

1/0 or smaller 2/0 or 3/0 4/0 or 250 Over 250 through 500 Over 500 through 900 Over 900 through 1750 Over 1750

8 6 4 2 1/0 2/0

Aluminum or Copper-Clad Aluminum 6 4 2 1/0 3/0 4/0

See Notes

Code Refresher  250.28(A) and (B) The purpose of the green-colored machine screw supplied with many





panelboards that are listed for use as service equipment is to function as the main bonding jumper. It is sized to be Code compliant. If the enclosure accidentally becomes energized by contact with an ungrounded (hot) service conductor, this green screw (main bonding jumper) will be the link in the fault-clearing path that connects the enclosure to the neutral of the supply. 250.24(A)(4) The grounding electrode conductor is not permitted to be connected to the equipment grounding bar unless the equipment bar is connected to the neutral bar with a wire or busbar (not where the main bonding jumper is a green-colored screw). Article 100 – Definitions: Bonding Jumper, System A system bonding jumper applies only to separately derived systems. It serves the same purpose as a main bonding jumper at a service supplied by a utility.


44

250.130(C)(4)


2014 NEC

Part VII. Methods of Equipment Grounding – Equipment Grounding Conductor Connections – Nongrounding Receptacle Replacement or Branch Circuit Extensions Significance The new Code introduces an additional method for providing an equipment grounding conductor to enhance the safety of older ungrounded wiring. Analysis The existing Code lists several methods for providing an equipment grounding conductor (EGC)

when extending existing ungrounded circuits or when replacing nongrounding receptacles with grounding-type receptacles. For extending existing ungrounded circuits or replacing nongrounding receptacles, an EGC can be connected to: an accessible point on the grounding electrode system, an accessible point on the grounding electrode conductor, the grounded service conductor within the service equipment enclosure, or the equipment grounding terminal bar in the enclosure where the ungrounded branch circuit srcinates. The 2014 NEC introduces an additional means for providing ungrounded circuits or receptacles with an EGC. The method is illustrated below. The change permits an EGC to be extended/connected from an outlet box on a different circuit that contains an EGC. That outlet box can be supplied with an EGC integral with the circuit wiring (right) or a separate EGC run back to the panel to provide grounding for ungrounded wiring (center). Branch circuit extension – modern NM cable with ground

Grounded duplex receptacles with USB charging ports

NM with ground Existing ungrounded NM cable Or

Separate branch circuits

To equipment grounding terminal in panel

Summary An EGC may be extended/connected from an outlet box on a different circuit that contains an EGC. That outlet box can be supplied with an EGC integral with the circuit wiring or a separate

EGC run back to the panel to provide grounding for ungrounded wiring. Application Question: What method of providing a separate EGC for ungrounded wiring provides the lowest impedance for fault current? Answer: Where the EGC is run in close proximity to the current-carrying conductors of the ct. Copyright 2013 by Patrick S. Ouillette, P.E.

45

250.167


2014 NEC

Part VIII. Direct-Current Systems – Direct-Current Ground-Fault Detection Significance A new section requires ground-fault detection systems for ungrounded dc systems. Analysis Dc systems operate either ungrounded or grounded. Grounded systems connect either the positive or negative polarity directly to ground (solidly grounded) or through a resistor to ground. A third type of grounding connects the midpoint, or other point on the system that suits the load, to ground (solidly grounded). Ground-fault detection is typically not used on solidly grounded dc

systems. New Section 250.167 requires direct-current ground-fault detection on ungrounded systems and permits detection on grounded systems. Subsection (C) of this new section requires legible, durable marking at the dc source or the first disconnecting means to indicate the grounding type employed. Section 320.3(C)(2) of NFPA 70E-2012, Standard for Electrical Safety in the Workplace, lists four types of dc grounding systems. Employing ground-fault equipment in ungrounded dc systems limits fault current to very low values, thus preventing the possibility of fires resulting from high fault currents. The Bender Model IRDH375 digital ground-fault monitor/ground detector pictured is suitable for use on ungrounded (floating) ac and dc systems. It meets or exceeds the existing requirement in 250.21(B) for ground detectors in ungrounded ac systems and the new requirement in 250.167(A) for detectors in ungrounded dc systems. The IRDH375 monitors for ground faults in ungrounded single-phase ac, three-phase ac, and dc systems by monitoring the system's insulation resistance. It can be connected to systems of up to 793 volts ac and 650 volts dc.

Model IRDH375 ground-fault monitor/ground detector

Courtesy of Bender Inc.

Summary Ungrounded dc systems shall be equipped with ground-fault detection systems. Grounded dc systems are permitted to have ground-fault detection systems. Dc systems shall be marked at the source or the first disconnecting means to indicate the grounding type employed. Application Question Is the dc ground-fault detection requirement in 250.167 applicable to PV systems? Answer The requirement is general and similar to the existing requirement for ground detectors for ungrounded ac systems in 250.21. Article 250 applies unless amended by Article 690, PV Systems. Every Code user needs to understand 90.3, Code Arrangement. Copyright 2013 by Patrick S. Ouillette, P.E.

46

250.186


2014 NEC

Part X. Grounding of Systems and Circuits of over 1000 Volts – Ground-Fault Circuit Conductor Brought to Service Equipment Significance A grounded conductor must be brought to service equipment over 1000 volts for fault clearing. Analysis This new section pertaining to over 1000 volts is similar in its requirements to 250.24(C), which requires the grounded conductor of systems 1000 volts or less to be run to the service equipment enclosure(s) for fault clearing purposes. This is true even where the grounded (neutral) conductor

is not used for circuits downstream from the service equipment (no neutral loads). Section 250.186 requires the same for systems and circuits over 1000 volts. The intent is to provide a low impedance ground return path back to the source to facilitate operation of overcurrent devices. The NEC is applicable only downstream from the service point. Subsection (A) applies to systems where the utility provides a grounded conductor to the service point. Subsection (B) applies where no grounded conductor is available at the service point. Generally, the grounded conductor brought to the service equipment, or the supply-side bonding jumper in subsection (B), is sized according to Table 250.66, but other factors apply including 250.184. Utility service over 1000 V Utility service over 1000 V

Service point Supply-side bonding jumper for connection to metal enclosures

E q u ip . g r n d .

Grounded conductor brought to grounded (neutral) bus N e u tr a l

No grounded conductor at service point

E q u ip . g r n d .

Summary For utility services over 1000 V, where a grounded conductor is provided at the service point, the grounded conductor shall be brought to the neutral bus in the service disconnect enclosure to provide a low impedance path for fault clearing. Where no grounded conductor is available at the service point, a supply-side bonding jumper shall be used to connect metal enclosures. Application Question If the enclosure in the grounded system diagram at the left above becomes accidentally energized, what is the fault return path? Answer The path is from the fault (one side of a phase winding) through the main bonding jumper, and back to the supply transformer winding through the grounded service conductor. Copyright 2013 by Patrick S. Ouillette, P.E.

47

250.194


2014 NEC

Part X. Grounding of Systems and Circuits of over 1000 Volts – Grounding and Bonding of Fences and Other Metal Structures Significance The 2014 NEC contains rules for grounding metal fences and other metal structures at ac substations. Analysis Most ac substations are not within the jurisdiction of the NEC. However, for installations that are within the scope of the NEC (see 90.2), like substations for industrial or institutional complexes or

non-utility owned wind generation substations, new rules require grounding and bonding of metal fencing and other metal structures at substations to limit step, touch, and transfer voltages. Where metal fences are located within 16 ft of exposed electrical conductors or equipment, the fence shall be bonded to the grounding electrode system with wire-type bonding jumpers as follows: (1) Bonding jumpers shall be installed at each fence corner and at maximum 160 ft intervals along the fence. (2) Where bare overhead conductors cross the fence, bonding jumpers shall be installed on each side of the crossing. (3) Gates shall be bonded to the gate support post, which shall be bonded to the grounding electrode system. (4) Any gate or opening in the fence shall be bonded across the opening by a buried bonding jumper. (5) The grounding grid or grounding electrode system shall be extended to cover the swing of all gates. (6) Barbed wire strands above the fence shall be bonded to the grounding electrode system. Alternative designs performed under engineering supervision are permitted for grounding and bonding of metal fences. Fence grounding is covered in IEEE 80-2000, IEEE Guide for Safety in AC Substation Grounding. Exposed conductive metal structures, including guy wires within 8 ft vertically or 16 ft horizontally of exposed conductors or equipment and subject to contact by persons, shall be bonded to the grounding electrode system(s) in the area. The grounding electrode system shall be in accordance with Part III of Article 250 (see 250.191). Summary New Section 250.194 contains prescriptive requirements for grounding metal fencing and other

metal structures at ac substations to limit step, touch, and transfer voltages. The provisions are applicable where electrical conductors and equipment are exposed.


48

250.194


2014 NEC

This substation serves to connect the wind farm turbines to the utility grid.

Application Question What size(s) grounding and bonding conductors are required for the grounding and bonding

required by this section? Answer Per 250.191, the grounding system at ac substations shall be in accordance with Part III of Article 250. The title of Part III of Article 250 is “Grounding Electrode System and Grounding Electrode Conductor.” Part III will provide guidance, but IEEE-80 should also be consulted.


49

300.22(C)(1)

General Requirements for Wiring Methods and Materials

2014 NEC

Wiring in Ducts Not Used for Air Handling, Fabricated Ducts for Environmental Air, and Other Spaces for Environmental Air (Plenums) – Other Spaces Used for Environmental Air (Plenums) – Wiring Methods Significance Cable ties used with plenum grade cables must also be plenum grade. Analysis This new requirement correlates with NFPA 90A, Standard for the Installation of AirConditioning and Ventilating Systems. NFPA 90A-2012 contains requirements for equipment,

including cable ties and other discrete products, in ceiling cavity plenums and raised floor plenums. The requirements include a provision for low smoke and heat release properties in accordance with ANSI/UL 2043, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces. This is now the standard for nonmetallic cable ties and other cable accessories used to secure and support cables in other spaces used for environmental air (plenums). The nonmetallic cable ties and accessories shall be listed as having low smoke and heat release properties. The burgundy cable ties pictured below meet UL 2043 standards. Generally, maroon/burgundy cable ties that have been manufactured over the past several years have been designed to meet this standard. This standard is not the same as that for nonmetallic cables and raceways in air-handling spaces, which must meet flame travel and smoke tests, since their area of exposure is much greater than that of cable fastening devices. This change has also been made in 770.24, 800.24, 820.24, and 830.24, Mechanical Execution of Work, and in new Section 800.170(C) addressing listing requirements for plenum grade cable ties. Note also that the title of Article 300 has been changed to better reflect its contents. Added language to the title is underlined in the header of this page. The former title was Wiring Methods. Summary Nonmetallic cable ties and other nonmetallic cable accessories used for securing and supporting cables installed in air-handling spaces shall be listed as having low smoke and heat release properties. Application Question Are communications cables installed in a space used for environmental air subject to this requirement? Answer Yes. See 800.24, Mechanical Execution of Work. Nonmetallic cable ties listed as having low smoke a nd heat release properties are generally identified by a maroon/burgundy color. Courtesy of Morris Products Inc.

Code Refresher  Chapter 8 (Art. 800, 810, 820, 830, and 840) is a stand-alone chapter and is not subject to the requirements of Chapters 1 through 7 unless specifically referenced in Chapter 8.


50

310.15(B)(3)(c) and Table

Conductors for General Wiring

2014 NEC

Ampacities for Conductors Rated 0-2000 Volts – T ables – Adjustment Factors – Raceways and Cables Exposed to Sunlight on Rooftops Significance An exception for Type XHHW-2 insulated conductors has been added to this subsection. Analysis The NEC requirement in 310.15(B)(3)(c) is slightly modified from the 2011 version. The title of the subsection now refers to all raceways and cables exposed to sunlight, rather than to circular raceways only. Research performed on several wiring methods since the previous Code cycle

concluded that all conductors in all wiring methods experienced significant ambient temperature increases above outdoor temperature when exposed to direct sunlight. Where raceways or cables are exposed to direct sunlight on or above rooftops, the adjustments shown in Table 310.15(B)(3)(c) shall be added to the outdoor temperature to determine the applicable ambient temperature to be used in applying the correction factors in Table 310.15(B)(2)(a) or Table 310.15(B)(2)(b). The adders in Table 310.15(B)(3)(c) have not changed, although there was much discussion about whether or not the adders needed to be increased. A new exception states that Type XHHW-2 insulated conductors shall not be subject to this ampacity adjustment. The exception recognizes the heat resisting capability of thermoset insulation, which does not soften when exposed to heat. The Informational Notes are more accurately stated in this revision. The accepted ambient temperature of a conductor is the temperature of the surrounding air. For conductors in conduits the ambient temperature is the temperature of the air inside the conduit. Tests have shown that the temperature of the air inside of conduits lying directly on a dark roof can exceed the outside air temperature by 70°F or more. The temperatures inside conduits on dark-colored roofs are higher than those for light-colored roofs where conduits are on or very near the surface of the roof. Where conduits are about 1 in. or more above the surface of the roof the temperature rise is greater for light-colored roof s because of the reflected heat from light-colored surfaces. Cables and other wiring methods/systems are similarly affected. Despite the differing test results for different wiring methods and roof colors, the ambient temperature adjustment can be adequately addressed by considering the distance of the conduit from the surface of the roof. For application of this subsection, the outdoor temperature value used must be meaningful. The 2 percentile monthly design dry-bulb temperature is a good indicator of the warm-season temperature. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Handbook of Fundamentals, 2009 edition, contains climatic design information in Chapter 14, which can be referenced concerning design temperatures for various locations. Another source for design temperatures is the Copper Development Association (www.copper.org, search under Applications – Electrical – Building Wire – Outdoor and Rooftop Temperatures for Selected U.S. and Canadian Locations). According to their data for ten Maine cities/locations, except for island locations in Maine, the 2% design temperatures range from 80°F to 86°F, depending on the city/area within the state. In reality, these temperatures will be exceeded 2% of the time, e.g., 14.88 hours in the month of July. Nevertheless, the 2% values are


51

310.15(B)(3)(c) and Table


2014 NEC

generally acceptable values for this purpose. Other data sources may suggest slightly higher design temperatures. The site www. EngineeringToolBox.com (search for “outdoor temperature and relative humidity”) lists a design temperature of 90°F for Maine. For Phoenix Arizona, the design temperature listed is 105 °F. Summary Where raceways or cables are exposed to direct sunlight on or above rooftops, the adjustments shown in Table 310.15(B)(3)(c) shall be added to the outdoor temperature to determine the applicable ambient temperature to be used in applying the correction factors in Table 310.15(B)(2)(a) or Table 310.15(B)(2)(b). Type XHHW-2 insulated conductors shall not be

subject to this ampacity adjustment. Table 310.15(B)(3)(c) Ambient Temperature Adjustment for Raceways or Cables Exposed to Sunlight on or Above Rooftops ______________________________________________________ Temperature Adder Distance Above Roof to Bottom of Raceway or Cable °C °F On roof 0 – 13 mm (0 – ½ in.)

33

60

Above roof 13 mm (½ in.)

22

40

Above roof 90 mm – 300 mm (3½ in. – 12 in.)

17

30

Above roof 300 mm – 900 mm (12 in. – 36 in.)

14

25

Example: A 3.5 ton gas/electric central air system is installed on a flat rooftop. The manufacturer specifies the minimum circuit ampacity as 26.8 amps and recommends a breaker size of 40 amps. Supply conductors are run inside 75′ of conduit which is supported by clamps that maintain a distance of ¾″ between the surface of the roof and the bottom of the conduit. Using an outside design temperature of 90°F, what minimum size THHW copper conductors can be used to supply the equipment? (Equipment terminals are rated 75°C.) Answer: The electric load consists of a motor-compressor and a fan motor. The manufacturer has already applied the requirements in 440.22(B)(1) in determining the recommended circuit breaker size, and 440.33 to arrive at the minimum circuit ampacity for sizing conductors. 110.14(C): The 90°C column in Table 310.15(B)(16) can be used as the starting point for ambient temperature correction; however, the corrected ampacity is not permitted to exceed the 75°C rating of the conductor due to the 75° equipment terminal rating. The adjusted ambient temperature from Table 310.15(B)(3)(c) is 130°F (90 + 40). The ambient temperature correction factor in Table 310.15(B)(2)(a) for the temperature range 123°F -131°F = 0.76. The final adjusted ampacity = 30.4 A (40 x 0.76). The adjusted ampacity does not exceed the 75°C ampacity (30.4 is less than 35). Overcurrent protection for 10 AWG copper is permitted to exceed 30 A, since the circuit rating is not the basis for conductor overload protection for this motor-compressor circuit. Section 240.4(D) does not apply to Article 440 (or to several other articles). A 40-A circuit breaker protecting 10 AWG copper THHW conductors is permitted.


52

310.15(B)(7)


2014 NEC

Ampacities for Conductors Rated 0-2000 Volts – 1 20/240-Volt, Single-Phase Dwelling Services and Feeders Significance A familiar table that permits reduced service and feeder conductor sizes for certain residential applications has been deleted. Analysis Most Code users are familiar with Table 310.15(B)(7). The first version of this table appeared in the 1978 NEC; however, for several preceding Code cycles, notes to ampacity tables and a

Simplified Wiring Table permitted reduced conductor sizes for services, feeders, and branch circuits where a low demand factor or diversified load existed. Modern Table 310.15(B)(7) is often used to size service and feeder conductors for residential applications through 400 A. The table is based on a demand of 83% (adjustment factor of 0.83) for certain residential services and feeders. It does not modify the ampacities of conductors as stated in the ampacity tables. Residential electricians know that for certain conductor types they are permitted to use AWG 2 aluminum (4 copper) and AWG 4/0 aluminum (2/0 copper) for 100- and 200-A services respectively. The reduced wire size also applies to feeders, where the feeder conductors carry the entire service load. Without Table 310.15(B)(7), residential service and feeder conductors are required to be AWG 1 aluminum (3 copper) for 100 A and AWG 4/0 aluminum (3/0 copper) for 200 A. The table has caused confusion and has been misapplied. In some instances, the table has been applied directly without regard to ampacity adjustment and ambient temperature correction that was required for an installation. You can understand the confusion when attempting to derate a conductor’s ampacity from a table that does not list ampacities, but matches service and feeder ratings to conductor sizes. In the 2014 NEC, Table 310.15(B)(7) is deleted and replaced with modified text in Section 310.15(B)(7). As in previous Code editions, the revised section applies to 120/240 volt, singlephase residential services through 400 amperes. It applies to service conductors of single-family dwellings and to service conductors supplying individual units of two-family and multifamily dwellings. Remember that service conductors is a broad term. The service conductors supplying individual units of two-family and multifamily dwellings is referring to the multiple sets of service-entrance conductors permitted by 230.40, Exceptions No. 1 and 2. Underground service conductors could also qualify for this size reduction. The section also applies to feeders in these same residential applications, where the feeder carries all of the service current. However, the conductor size reduction does not apply to service conductors that supply two-family or multifamily dwelling buildings, only to service conductors that supply the entire load for an individual dwelling unit within these buildings. To use Section 310.15(B)(7), simply select the desired service or feeder rating, multiply that rating by 0.83, apply any additional factors required depending on the number of current-carrying conductors and the ambient temperature, then select a conductor with the required ampacity from the appropriate ampacity table. See new Example D7 in Informative Annex D. As in previous


53

310.15(B)(7)


2014 NEC

editions, the grounded (neutral) conductor is permitted to be sized smaller than the ungrounded conductors, provided the requirements of 220.61 and 230.42 for services and the requirements of 215.2 and 220.61 for feeder conductors are met. Summary Table 310.15(B)(7) has been deleted. The reduced conductor size permitted for certain residential services and feeders is still permitted by applying a factor of 0.83 to the rating of the service or feeder. Additionally, any ampacity adjustment (derating) for more than three current-carrying conductors in a raceway or cable, or any ampacity correction for ambient temperature must be applied. If no derating or ambient temperature correction factors are applied, conductors sized

according to 310.15(B)(7) will be the same as obtained by use of deleted Table 310.15(B)(7). Example 1 What size aluminum XHHW service-entrance conductors are required for a 200-A, 120/240-V, single-phase service for a one-family dwelling?

Service rating = 200 amps. Multiply by 0.83: 200 A x 0.83 = 166 A. Select an aluminum conductor from the 75°C column in Table 310.15(B)(16). Select 4/0 Al XHHW conductors with an ampacity of 180 A, which is at least 166 A. Example 2 What size aluminum SER cable containing XHHW conductors is required for a 200-A rated feeder that carries all of the service load for a one-family dwelling supplied by a 120/240-V, single-phase service? The feeder cable is embedded in thermal insulation.

Feeder rating = 200 amps. Multiply by 0.83: 200 A x 0.83 = 166 A. Section 338.10(B)(4)(a) states that where used in thermal insulation the ampacity shall be in accordance with the conductor’s 60°C rating. Select an aluminum conductor size from the 60°C column in Table 310.15(B)(16) that has an ampacity of at least 166 amps. 250 kcmil aluminum XHHW conductors with a 60°C ampacity of 170 A can be used. Application Question A 4-gang meter pack contains 100-A service disconnects for three dwelling units and an owner’s panel [common area metering required by 210.25(B)]. What minimum size aluminum SER feeder cables are required to be run to the four panels? The cables are embedded in thermal insulation in the exterior wall where the meter pack is mounted. Answer

If the feeders are not embedded in insulation, AWG 2 aluminum can be used (100 A x 0.83 = 83 A → AWG 2 aluminum with a 75°C ampacity of 90 A). If the feeders are embedded in insulation, AWG 1 aluminum can be used, since it’s 60°C ampacity of 85 amps is equal to or greater than 83 A. There are two different ampacities that apply to adjacent portions of the same circuit. Generally, the lower ampacity must be used. However, if the cable length within the insulation is Copyright 2013 by Patrick S. Ouillette, P.E.

54

310.15(B)(7)


2014 NEC

not more than 10′ or 10% of the cable length not embedded in insulation, whichever is less, then the 75°C ampacity applies to the overall cable and AWG 2 aluminum is permitted. See Section 310.15(A)(2), Exception and the Code Refresher below. Code Refresher  Section 310.15(A)(2) This section is used to compute the overall ampacity of circuit conductors, where different ampacities are permitted for adjacent portions of a circuit. The general Code requirement is that the lower ampacity must be used for the entire circuit length. By exception, the higher ampacity can be used if the lower ampacity circuit length is not more than 10′ and

not more than 10% of the circuit length of the higher ampacity portion of the circuit. Different ampacities for the same circuit could exist where a portion of a circuit is underground, embedded in thermal insulation, bundled, or exposed to a different ambient temperature. The exception does not apply if conductor ampacity is limited by the rating of terminations, as specified in 110.14(C). See the diagram below for further explanation.

10

100

′

′

60°Campacity

75°Campacity

Circuit conductor can be used at its 75°C ampacity. 10/100 = 10%

The circuit length corresponding to the 60°C ampacity is not more than 10% of the circuit length corresponding to the 75°C ampacity.

′

′

8 Ambient temp. of 100°F

65

Ambient temperature of 78-86 (°F)

Circuit conductor ampacity must be based on ambient temp. of 100°F. 8/65 = 12.3%

The circuit length corresponding to the 100°F ambient temp. is more than 10% of the circuit length corresponding to the 78-86°F ambient temp.

Example Applications of 310.15(A)(2)


55

330.30(D)(3)

Metal-Clad Cable: Type MC

2014 NEC

Securing and Supporting – Unsupported Cables Significance An additional permission for unsupported Type MC cable is included in the new Code. Analysis Unless otherwise provided, Type MC cable shall be secured and supported at intervals not exceeding 6 ft. Cables containing four or fewer conductors size 10 AWG or smaller shall be secured within 12 in. of every box, cabinet, fitting, or other cable termination. MC cable run horizontally in wood or metal framing members, or that has similar supporting means, shall be considered secured and supported. Type MC cable shall be permitted to be unsupported where: (1) the cable is fished in finished buildings and supporting is impractical, or (2) the cable is installed in lengths not exceeding 6 ft from the last cable support to the point of connection to luminaires or other electrical equipment above an accessible ceiling. Subsection (3) is new in the 2014 NEC and permits Type MC cable with interlocked armor to be unsupported in lengths up to 3 ft from the last secure support to provide flexibility at equipment. The construction of interlocked armor Type MC makes it suitable for use where flexibility is necessary. The permission applies where flexibility is necessary to minimize the transmission of vibration from equipment or where providing flexibility for equipment that requires movement after installation. OR Clamp securing MC cable

?

d e rt o p p u s n u

Connector securing MC cable

m u m i x a m tf 3

Type MC cable

Supply to ceiling-suspended fan requires flexibility.

Summary Type MC cable of the interlocked armor type is permitted to be unsupported in lengths not exceeding 3 ft from the last point where the cable is securely fastened, where used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to facilitate movement of equipment after installation. Application Question Does an MC cable connector provide the secure fastening that is required in 330.30(D)(3)? Answer In 330.30(D)(2), it states that Type MC cable fittings are permitted as a means of cable support for the purpose of this section. New (3) uses the words securely fastened. Supported and secured have different meanings. Secured means fastened in place. The AHJ will decide.


56

338.10(B)(4)(b)

Service-Entrance Cable: Types SE and USE

2014 NEC

Uses Permitted – Branch Circuits or Feeders – Installation Methods for Branch Circuits and Feeders – Exterior Installations Significance The ampacity of Types USE and USE-2 conductors has been clarified. Analysis Types USE (underground service-entrance) and USE-2 cables are designed and listed for underground installations, including direct burial in earth. They are available as single conductors and multiconductor cables. In addition to Types USE and USE-2, some conductors are “triple-

rated,” such as Type RHH/RHW-2/USE-2 shown below.

Type RHH or RHW-2 or USE-2

Courtesy of Southwire Company

A new exception has been added to 338.10(B)(4)(b), which states that single-conductor Type USE and multi-rated USE conductors are not subject to the ampacity limitations of Part II of Article 340. Section 340.80 limits the ampacity to that of 60°C conductors. Type USE conductors are rated 60°C; Type USE-2 conductors are rated 90°C. It may have been the intent in the existing Code that Types USE and USE-2 conductors were not subject to the 60°C ampacity, but the exception provides clarification. It is important to remember Types USE andused USE-2 conductors are limited to exterior use, primarily underground. The that conductors can be above ground only as multiconductor, messenger-supported aerial cable or where they emerge from the ground and terminate in outdoor service or metering equipment. Additional usage information can be found in the UL White Book, Category (TYLZ), Service-Entrance Cable. Type USE conductors do not have a flame-retardant covering; hence, the prohibition of their use for interior wiring. The triple-rated conductors are permitted for aboveground use (used as RHW) and interior wiring, since both the RHH and RHW conductor types have flame-retardant coverings. Summary Single-conductor Type USE and multi-rated USE conductors are not subject to the ampacity limitations of Part II of Article 340, i.e., the ampacity corresponding to a 60°C temperature rating for the conductor. Application Question What is the ampacity of 4/0 AWG aluminum Type USE-2 conductors installed as an underground feeder to supply 120/240-volt, single-phase power to a structure? Answer From Table 310.15(B)(16), the 90°C ampacity is 205 amperes. Unless all circuit terminations are rated for 90°C, the 75°C ampacity of 180 amperes must be used. See 110.14(C). Copyright 2013 by Patrick S. Ouillette, P.E.

57

348.30(A), Ex. No. 4 (and others)

Flexible Metal Conduit: Type FMC (and others)

2014 NEC

Securing and Supporting – Securely Fastened Significance Fittings are a recognized means of support for three flexible raceway types for lengths up to 6 ft. Analysis Existing Code permits Types AC [320.30(D)(3)] and MC [330.30(D)(2)] cables to be unsupported within an accessible ceiling to supply luminaires or other electrical equipment. The unsupported cable is limited to 6 ft in length between the last support and the connection to the luminaire or other equipment. For the purpose of these sections, AC and MC cable fittings are permitted as a

means of cable support. The change in the 2014 NEC harmonizes with these unsupported cable permissions. The change applies to three raceway types: flexible metal conduit (Type FMC), 348.30(A), Exception No. 4; liquidtight flexible metal conduit (Type LFMC), 350.30(A), Exception No. 4; and liquidtight flexible nonmetallic conduit (Type LFNC-B), 356.30(4). Type LFNC-B is the only type of LFNC permitted in lengths over 6 ft. For the purpose described, the raceway fittings are considered a means of support.

a 6

ft m

. x

g n le

th

6 ft max.

support length to

FMC Support here may be permitted by exceptions to 300.11 in existing Code.

LFMC LFNC-B Courtesy of Southwire Company

FMC, LFMC, and LFNC-B fittings are considered a means of support for up to 6 ft lengths of flexible conduit used to supply luminaires or other equipment within accessible ceilings.

Summary Types FMC, LFMC, and LFNC-B raceways shall be permitted to be unsupported for up to 6 ft in length from the last point of support to the connection to a luminaire or other equipment within an accessible ceiling. For this purpose, the raceway fittings are considered a means of support. Application Question For wiring from the J-box to the luminaire in the diagram above, are FMC and LFMC in 6 ft

lengths or less permitted to serve as the equipment ground? Answer Yes, with conditions, and since flexibility is not required. The flexible conduit must be terminated in listed fittings and overcurrent protection is limited to 20 A. See 250.118(5) and (6).


58

376.22(B)

Metal Wireways

2014 NEC

Part II. Installation – Number of Conductors and Ampacity – Adjustment Factors Significance The often misunderstood application of adjustment factors (derating) for over 30 current-carrying conductors in metal wireways has been clarified. Analysis Metal wireways installed above panels are a convenient way to transition from horizontally run branch circuits to vertical raceways between the wireways and panels, or for routing incoming circuits to a specific panel among a group of panels. Depending on where the branch circuit

wiring leaves the wireway relative to where the circuit conductors enter the wireway, the number of current-carrying conductors at a cross section of the wireway could exceed 30 conductors. The 30-conductor threshold does not relate to a total of 30 current-carrying conductors in the wireway, but to 30 current-carrying conductors at any cross section. This is clarified in Section 376.22(B) of the 2014 NEC. Where the number of current-carrying conductors at any cross section exceeds 30, the adjustment factors in 310.15(B)(3)(a) must be applied. If 31-40 conductors are installed at any cross section, all conductors have to be adjusted to 40% of their initial ampacity, 35% for 41 or more conductors. These are deep reductions in ampacity that apply to all current-carrying conductors, not just to the number of current-carrying conductors over 30.

The raceway entries at the bottom of this wireway (not shown) are such that not more than 30 conductors travel horizontally through any cross section of the wireway. No ampacity reduction is required.

Summary Where the number of current-carrying conductors at any cross section of a metal wireway exceeds 30, the adjustment factors in 310.15(B)(3)(a) must be applied to all current-carrying conductors, not just to the number of current-carrying conductors over 30. Application Question Thirty-five current-carrying conductors pass through a cross section of a metal wireway. The conductors vary in size, but most conductors are 12 AWG with an insulation rating of 90°C and an ampacity of 30 amps from Table 310.15(B)(16). What is their adjusted ampacity? Answer 12 A [From Table 310.15(B)(3)(a): 30 amps x 40% = 12 A] Code Refresher  The sum of the cross-sectional areas of all conductors at any cross section of a metal wireway cannot exceed 20% of the interior cross-sectional area of the wireway. [376.22(A)]


59

392.10(A) and Table 392.10(A)

Cable Trays

2014 NEC

Uses Permitted – Wiring Methods Significance Table 392.10(A) has been revised to clarify the wiring methods permitted in cable trays. Analysis Nearly all wiring methods that are permitted for use above ground or inside buildings, and that consist of cables or circular raceways, are permitted to be installed in cable trays. The wiring methods permitted in cable tray systems in 392.10(A) are subject to the conditions described in their respective articles and sections. Cable tray is a mechanical support system for service

conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. Trays are available in a variety of types and styles to meet various wiring support needs. Trays have become popular cable management systems for data and other low-energy cabling. Wire mesh basket trays are included in the scope of Article 392. Trays are not limited to industrial applications, except that single-conductor cables, welding cables, and medium voltage (Type MV) cables can only be installed in trays in industrial settings. Where appropriate, this revision has added the wiring Type abbreviation, e.g., Type ITC (instrumentation tray cable), in Table 392.10(A) after the title of the article/wiring method. The wiring methods are listed in the table in alphabetical order. Communications raceways now include optical fiber raceways and signaling raceway. Table 392.10(A) does not list all of the wiring methods that are permitted in trays. The table contains an entry for “Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays.”

Ladder cable tray Nearly all wiring methods that are permitted for use above ground or inside buildings, and that consist of cables or circular raceways, are permitted to be installed in cable trays.

Summary Table 392.10(A) has been revised to clarify the wiring methods permitted in cable trays. Where appropriate, the wiring Type abbreviation, e.g., Type ITC (instrumentation tray cable), has been added in Table 392.10(A) after the title of the article/wiring method. Application Question Is a cable tray system a raceway-type wiring method? Answer Cable tray does not meet the definition of raceway. It can be considered a wiring method, but is probably more accurately described as a support system for wiring methods. Note that the title of Chapter 3 is Wiring Methods and Materials.


60

392.18(H) and Exception

Cable Trays

2014 NEC

Cable Tray Installation – Marking Significance An exception to cable tray marking has been added for industrial establishments. Analysis Cable trays containing conductors rated over 600 volts shall be marked with a permanent, legible warning notice with the words “DANGER – HIGH VOLTAGE – KEEP AWAY.” The warning shall be placed in readily visible positions along the tray at intervals not exceeding 10 ft. New for this Code, the warning marking(s) or labels shall comply with 110.21(B). Section 110.21(B) is

itself a new section in the 2014 markings and labels.

NEC

that contains specific requirements for field-applied hazard

The new exception is for industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons will service the installation. The exception applies to installations of tray that are not accessible (as applied to equipment), and permits the warning notices to be located where necessary to ensure safe maintenance and operation of the installation. Note that the Over 1000 Volts conversion from Over 600 volts has not been implemented in this section. Exception where serviced only by qualified persons: Warning notices shall be located where necessary to ensure safe maintenance and operation. 10 ft max. spacing by general rule

DANGER-HIGHVOLTAGE-KEEP AWAY

DANGER-HIGHVOLTAGE-KEEP AWAY

Cable tray containing conductors rated over 600 volts DANGER – HIGH VOLTAGE – KEEP AWAY

Red background and exclamation point

Summary Cable trays containing conductors rated over 600 volts shall be marked with a permanent, legible warning notice with the words “DANGER – HIGH VOLTAGE – KEEP AWAY.” Where the tray is not accessible, in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons will service the installation, warning notices shall be located where necessary to ensure safe maintenance and operation of the installation. Application Question What does accessible (as applied to equipment) mean? Answer Admitting close approach: not guarded by locked doors, elevation, or other effective means.


61

ARTICLE 393 – Low-Voltage Suspended Ceiling Power Dist. Sys.

2014 NEC

Low-Voltage Suspended Ceiling Power Distribution Systems Significance The increasing availability and use of low-voltage, low-power equipment such as lighting, sensors, information technology equipment, and audio visual equipment necessitates updated rules for installation of low-voltage systems and equipment. Analysis With the increasing popularity of alternative energy systems providing dc outputs and the low power needs of energy efficient lighting and other loads, powered ceiling grid offers an innovative

wiring method. Many modern devices use dc power at low voltage and current levels. Cell phones, computers, LED luminaires, electronically ballasted fluorescent luminaires, sensors, controls, etc. use dc power at low levels. A ceiling support grid that doubles as a dc distribution system can be efficiently powered from on-site dc generation (PV, wind, fuel cells) without the need for DC to AC to DC conversion costs and power losses. Where the ceiling power distribution grid is supplied by an ac branch circuit, a power server module is used to convert ac to dc (bulk, rather than multiple separate rectifiers) and provides multiple channels for the connection of Class 2 output circuits. Low-voltage suspended ceiling power distribution systems operate at “touch-safe” power levels. Its plug-and-play design permits room or area repurposing and reconfiguration without rewiring. While the current NEC Article 411 limits its coverage to lighting systems operating at 30 volts or less, Article 393 covers lighting and other loads supplied through powered suspended ceiling grid. Many of the requirements for the new article are similar to the requirements in Articles 411 and 725. The low-voltage suspended ceiling power distribution system shall be listed as a complete system or be assembled from only listed parts approved for the function. Circuits powered by the system shall be limited to 30 volts AC or 60 volts DC and limited to Class 2 power levels in Tables 11(A) and 11(B) in Chapter 9 of the NEC. The power distribution systems are permitted in indoor dry locations for residential, commercial, and industrial installations, and in other spaces used for environmental air in accordance with 300.22(C). They are prohibited in damp or wet locations, classified (hazardous) locations, concealed locations, for lighting in general or critical patient care areas, and where subject to corrosive fumes or vapors or physical damage. Unless specifically listed as part of the assembly, low-voltage suspended ceiling power distribution systems may not be used as part of a fire-rated floor–ceiling or roof–ceiling assembly. Only the main support rails (defined as grid bus rail in the NEC) of a suspended ceiling are powered. Power feed connectors connect cables from the power supply to the power distribution busbar, and rail-to-rail connectors interconnect busbars from one ceiling grid rail to another grid rail. Power supplies shall be protected at a maximum of 20 amperes. Reverse polarity (back feed) protection of DC circuits shall be provided with the power supply, or, where the power supply is not provided as a part of the system, shall be provided as part of the grid rail busbar or as a part of


62


2014 NEC

the power feed connector. Generally, Class 2 conductors shall be minimum 18 AWG copper. The Class 2 circuits shall not be grounded. The disconnecting means for the Class 2 power supply shall be accessible and within sight of the Class 2 power source for servicing and maintenance of the power distribution system. Summary New Article 393 provides rules for distribution of low voltage current through suspended ceiling grid designed for power distribution for the supply of luminaires, sensors, and other low-power devices and equipment located within, on, or suspended below the ceiling grid. Equipment is supplied by Class 2 circuits using approved cables and connectors.

Application Question T F The power limitation for an inherently limited Class 2 DC power supply that supplies a single circuit to a dc power distribution grid is 100 VA. Answer True. See Table 11(B) in Chapter 9 of the NEC.


63


2014 NEC

Power server module mounted above ceiling grid

16-channel power module with Class 2 output circuits

Courtesy of Nextek Power Systems

Cable connectors connecting to dc power grid

Courtesy of Tyco Electronics Corporation, a TE Connectivity Ltd. company


64

404.2(C)

Switches

2014 NEC

Switch Connections – Switches Controlling Lighting Loads Significance Five more exceptions have been added to the rule for providing a neutral conductor at a switch used for the control of lighting. Analysis This rule was introduced in the 2011 NEC and requires that the grounded circuit conductor of a general-purpose circuit that supplies lighting be provided at switch locations for the future connection of electronic lighting controls such as occupancy sensors. This action was designed to halt the use of equipment grounding conductors being used as current-carrying conductors for electronic lighting controls. The Code change addresses those instances where an occupancy sensor or other electronic lighting control would be redundant, excessive, or impossible to install. There are seven conditions in which the grounded conductor is not required to be provided:

(1)

2011

(2)

2011

(3)

2014

(4)

2014

(5)

2014

(6) (7)

2014

2014

Where conductors enter the box enclosing a switch through a raceway, provided the raceway is large enough to include a grounded conductor Where the box enclosing the switch is accessible for the installation of an additional or replacement cable without removing finish materials Where snap switches with integral enclosures comply with 300.15(E) – e.g., boxless switches in 334.40(B) and in manufactured homes Where a switch does not serve a habitable room or bathroom – e.g., closets (wall switches and door-jamb switches), hallways, storage and utility spaces, garages, etc. – Habitable rooms are rooms for living, sleeping, eating, or cooking. Where multiple switch locations control the same lighting load such

that the entire floor area of a room is “seen” from a single location or combined switch locations – It may be that more than one sensor is needed to “see” the entire room or space. Where lighting in the area is controlled by automatic means Where a switch controls a receptacle load – unknown load – listing of sensor will not include a receptacle load – See 210.70(A)(1), Exc. 1.

Summary The grounded circuit conductor of a general-purpose circuit that supplies lighting shall be provided at switch locations for the future connection of electronic lighting controls such as occupancy sensors. There are seven conditions where the rule does not apply—where an occupancy sensor or other electronic lighting control would be redundant, excessive, or impossible to install. Application Question Does the requirement apply to switch locations not in the illuminated area? Outdoor areas? Answer Code panel members agreed that switch locations not in the illuminated area should have a grounded connection to accommodate some dimmers. It does not appear that the rule applies to switches for outdoor lighting outlets (habitable area?). A level of illumination is required at entrances and exits. See 210.70(A)(2)(b) for required lighting at dwelling unit entrances or exits. Copyright 2013 by Patrick S. Ouillette, P.E.

65

404.8(C)

Switches

2014 NEC

Accessibility and Grouping – Multipole Snap Switches Significance The permission for multipole switches to switch more than a single circuit is now more restrictive. Analysis In previous Codes a multipole, general-use snap switch was permitted to control more than one circuit if the voltage rating of the switch was not less than the nominal line-to-line voltage of the system supplying the circuits. Alternatively, the switch was permitted to control more than one circuit if the switch was listed and marked as a two-circuit or three-circuit switch. The latter

permission has been brought forward to the 2014 NEC, but the former has been deleted. This is consistent with the UL Guide Information for Electrical Equipment (the White Book), which states that “Multi-pole, general-use snap switches have not been investigated for more than singlecircuit operation unless marked ‘2-circuit’ or ‘3-circuit.’” A line-to-line circuit, such as a 240-volt circuit supplying a 240-volt load, is a single circuit, but a multiwire circuit is not a single circuit. Double-pole toggle switch

Must be listed and marked as a two-circuit switch

Summary A multipole, general-use snap switch cannot be fed from (used to control) more than a single circuit unless the switch is listed and marked as a two-circuit or three-circuit switch. Application Question If the switch in the diagram above is listed and marked as a two-circuit switch and used as such, serving single-phase line-to-neutral loads, how will the circuit breakers need to be arranged in the panel? Is this a multiwire branch circuit? Answer The breakers will have to be vertically adjacent and tied with an identified handle tie, or a 2-pole breaker could be used. This is to satisfy 210.7. A multiwire branch circuit has one neutral. Code Refresher  210.7 – Where two or more branch circuits supply devices or equipment on the same mounting strap, a means to simultaneously disconnect the ungrounded conductors supplying these devices shall be provided at the point of srcin of the branch circuits.


66

406.3(E)

Receptacles, Cord Connectors, and Attachment Plugs

2014 NEC

Receptacle Rating and Type – Controlled Receptacle Marking Significance This new section requires specific marking on receptacles that are energized and de-energized automatically in conjunction with energy management or building automation. Analysis Energy standards currently address building envelope requirements and mechanical equipment efficiencies such as HVAC (heating ,ventilating, and air conditioning) systems. Standards for lighting power densities, occupant-sensing controls, daylighting requirements, and equipment like variable speed fans, etc. have been successfully used to reduce energy consumption. ASHRAE 90.1-2010, Energy Standard for Buildings, Except Low-Rise Residential Buildings, is the basis for the International Energy Conservation Code. This popular ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standard establishes a baseline for the Leadership in Energy and Environmental Design (LEED) program. Section 8.4.2 of ASHRAE 90.1-2010 requires that at least 50% of 125-volt, 15- and 20-amp receptacles installed in private offices, open offices (including those installed in modular petitions), and computer classrooms be automatically controlled. The control can be by time-of-day systems, occupancy control, or other automatic control based on occupancy. This load is commonly referred to as “plug load.” The rule does not apply to dwelling occupancies that are not more than three stories above grade.

New Section 410.3(E) of the NEC requires that all nonlocking-type 125-volt, 15- and 20-amp receptacles that are controlled by an automatic control device or incorporate control features that de-energize the outlet for the purpose of energy management or building automation be marked to indicate that they are a controlled receptacle. They shall be marked with the symbol shown below. The marking shall be visible after installation. The marking is not required for receptacles controlled by a wall switch as permitted by 210.70 to provide the required room lighting outlets. The Code allows for either manufacturer marking or a field marking that is acceptable to the authority having jurisdiction (AHJ). There are receptacles currently on the market that operate on “Z-Wave” technology (automatically controlled). The receptacle shown below is one such receptacle. At least one of the receptacle brands currently available is marked to indicate that it is a controlled receptacle. However, the marking does not conform to the specifics of this new NEC requirement. Summary Nonlocking-type 125-volt, 15- and 20-amp receptacles that are controlled by an automatic control device or incorporate control features that de-energize the outlet for the purpose of energy management or building automation shall be marked by the prescribed symbol. The marking is not required for receptacles controlled by a wall switch as permitted by 210.70 to provide the required room lighting outlets.


67

406.3(E)


2014 NEC

Automatically controlled receptacle indicated by symbol on receptacle face

Application Question T F The symbol that is required to be placed on automatically controlled receptacles is permitted to be on the faceplate. Answer False. The symbol must be on the receptacle face such that it is visible after installation. For splitwired receptacles, it should be clear which receptacle is automatically controlled. For a typical duplex receptacle (not decora style), it may be difficult to locate the symbol such that it can be seen while an attachment plug is inserted. It is not clear if the “visible after installation” requirement means visible after a plug is inserted. Code Refresher/Revision 

406.3(D) Isolated ground receptacles shall be identified by an orange triangle located on the face of the receptacle. In addition to the marking, some isolated ground receptacles are orange.



517.18(B) (and other sections) “Hospital grade” receptacles are identified by a green dot on the face of the receptacle. Although the Code does not address specifics of the identification, the green dot is specified in the UL listing. The phrase “Hospital Grade” or “Hosp. Grade” are marked on the back of qualifying receptacles (“Hospital Only” for 20A, 125-V locking receptacles with no green dot).



517.30(E) The cover plates for receptacles or the receptacles themselves supplied from the essential electrical system shall have a distinctive color or marking so as to be readily identifiable. The color red is commonly used as the identifier. Code Revision: The 2014 NEC requires these nonlocking-type, 125-volt, 15- and 20ampere receptacles to have an illuminated face or an indicator light to indicate there is

power to the receptacle.


68

406.4(D)(4) Receptacles, Cord Connectors, and Attachment Plugs

2014 NEC

General Installation Requirements – Replacements – Arc-Fault Circuit-Interrupter Protection Significance This very important requirement was introduced in the 2011 NEC as a new subsection, with an effective date of January 1, 2014. Analysis Since this rule becomes effective with adoption of the 2014 NEC, it is beneficial to review this section anew. The rule is similar to the rule requiring GFCI-protected receptacles to be installed

where replacements are made at receptacle outlets that are required to be GFCI-protected elsewhere in the Code. Where a receptacle outlet is supplied by a branch circuit that requires arcfault circuit-interrupter protection elsewhere in the Code, a replacement receptacle at this outlet shall be one of the following: 1) A listed outlet branch-circuit type AFCI receptacle, 2) A receptacle protected by a listed outlet branch-circuit type AFCI receptacle, or 3) A receptacle protected by a listed combination-type AFCI circuit breaker. The options permit the use of AFCI circuit breakers or AFCI receptacles. This requirement is related to, but should not be confused with, 210.12(B), Branch Circuit Extensions or Modifications – Dwelling Units. Section 210.12(B) has an effective date of January 1, 2011, or whenever the 2011 NEC is adopted, and requires AFCI protection for specific branch circuits that are modified, extended, or replaced in existing dwellings. Section 406.4(D)(4) requires AFCIprotected replacement receptacles for circuits in existing dwellings that require AFCI protection. Option 2: Install outlet branch-circuit type AFCI receptacle here and a standard receptacle at the location of the defective receptacle.

Receptacle in need of replacement

120-V, 15- or 20-A existing branch circuit in dwelling unit panelboard. Option 3: Install combination-type AFCI circuit breaker and standard receptacle at the location of the defective device.

R

X

Option 1: Install outlet branchcircuit type AFCI receptacle.

Existing wiring

Summary Where existing wiring supplies a receptacle from a branch circuit that requires arc-fault circuitinterrupter protection by new NEC rules, a replacement receptacle at this outlet shall be a listed outlet branch-circuit type AFCI receptacle, a receptacle protected by a listed outlet branch-circuit type AFCI receptacle, or a receptacle protected by a listed combination-type AFCI circuit breaker. Application Question What rooms and occupancy type(s) does this requirement for replacing a defective receptacle with an AFCI-protected receptacle apply to? Answer When replacing a receptacle located in any of the rooms or areas that require AFCI protection for branch circuits supplying the room or area, AFCI protection for the receptacle shall be provided. The rule applies to dwelling units and dormitories.


69

406.9(B)(1) Receptacles, Cord Connectors, and Attachment Plugs

2014 NEC

Receptacles in Damp or Wet Locations – Wet Locations – Receptacles of 15 and 20 Amperes in a Wet Location Significance The requirement for “extra-duty” outlet box hoods has been broadened in its application. Analysis There have been many failures of in-use covers. The hinges for some types of covers are not durable, sometimes leaving the receptacle uncovered. The so-called “extra-duty” cover/hood was introduced in the 2011 NEC and was required for receptacles installed in wet locations on

enclosures supported from grade at other than one- or two-family dwellings. The 2014 NEC requires these extra-duty covers on all 15- and 20-ampere, 125- through 250-volt receptacles installed in wet locations. Hoods installed for this purpose shall be listed and identified as “extraduty.” Section 590.4(D)(2) applies the same new requirement to temporary installations. The more durable hoods will be beneficial for harsh work environments such as outdoor receptacles at construction sites and will help to alleviate the problem of broken in-use covers in all applications and occupancy types. It may be difficult to identify an extra-duty hood. Generally, they are constructed of metal. Requirements for extra-duty outlet box hoods are found in ANSI/UL 514D-2000, Cover Plates for Flush-Mounted Wiring Devices.

Red·Dot® Code Keeper® Universal While-In-Use Cover Thomas & Betts Corp.

Summary Extra-duty hoods are required on all 15- and 20-ampere, 125- through 250-volt receptacles installed in wet locations. Application Question What is a wet location? Answer For the purpose of this section, a wet location is an unprotected location exposed to weather. Since the receptacle is exposed to weather, the receptacle must be weatherproof, constructed or protected so that exposure to the weather will not interfere with successful operation.


70

406.15


2014 NEC

Dimmer-Controlled Receptacles Significance This change permits, with limitations, the use of dimmers for the control of receptacles used for lighting. Analysis Section 404.14(E) permits general-use dimmer switches to be used only to control permanently installed incandescent luminaires unless listed for the control of other loads and installed accordingly. Dimmers have been misapplied for control of low-voltage, under-cabinet lighting

and other cord-and-plug-connected lighting to achieve desired lighting levels or ambience. New Section 406.15 permits dimmer control of receptacles used for lighting purposes, so long as the plug/receptacle combination is a nonstandard configuration type that is specifically listed and identified for each such unique combination. One such nonstandard configuration is pictured below. The duplex receptacle marked “CAUTION LAMP LOADS ONLY ” will not accept plugs that are not intended to be used with this receptacle. The plug shown is listed for this combination.

Summary Dimmer control of receptacles used for lighting purposes is permissible, so long as the plug/receptacle combination is a nonstandard configuration type that is specifically listed and identified for each such unique combination. Application Question Is the receptacle pictured above a 15-A or a 20-A receptacle? Answer

The protrusion between the receptacle slots is not all that’s nonstandard. The neutral T-slot appears the same as that of a 20-A receptacle, but the slot on the “hot” side is shorter than that of a typical receptacle. Note the nonstandard blade width on the plug. Actually, it is a 20-A, Lutron Nova T receptacle, model #NTR-20-DFDU-IV.


71

408.55(C)

Switchboards, Switchgear, and Panelboards

2014 NEC

Part IV. Construction Specifications – Wire-Bending Space Within an Enclosure Containing a Panelboard – Back Wire-Bending Space Significance The new Code addresses wire-bending space for conductors entering the back of an enclosure. Analysis Existing requirements for wire-bending space at the top, bottom, and sides of panelboard enclosures are specified in Tables 312.6(A) and (B). Top and bottom wire-bending space is described in Table 312.6(B), with exceptions, and side wire-bending space is described in Table

312.6(A). These rules in 408.55 have been reorganized in subsections (A) and (B) in the 2014 NEC. In the new rules in subsection (C), where a raceway or cable entry is in the wall of an enclosure opposite a removable cover, the depth of the enclosure (distance from the wall to the cover) shall be permitted to be the distance required in Table 312.6(A) for one wire per terminal. In the panelboard below, for a 4/0 AWG conductor entry in the back wall of the panel, the enclosure is required to be a minimum of 4 in. deep. This is the approximate depth of many residential loadcenters. Also, the distance from the center of the rear entry to the nearest termination for the entering conductors shall not be less than the distance required in Table 312.6(B). From that table, the distance from the center of the cable or raceway entry (for a 4/0 AWG conductor, other than compact Alum.) to the nearest termination for the entering conductors shall not be less than 7 in. Existing Section 312.6 contains requirements for minimum width of wiring gutters and minimum wire-bending space at terminals for conductors entering or leaving cabinets, cutout boxes, and meter socket enclosures. Panelboards are placed in cabinets or cutout boxes (enclosures). 4/0 AWG

7″ min.

Summary Where a raceway or cable entry is in the wall of an enclosure opposite a removable cover, the distance from that enclosure wall to the cover shall be permitted to be the distance required in Table 312.6(A) for one wire per terminal. Also, the distance from the center of the rear entry to the nearest termination for the entering conductors shall not be less than the distance given in Table 312.6(B). Application Question Is it permissible for a 4/0 Al SEU cable to enter the rear of the panelboard pictured, on either side of, and adjacent to, the panelboard frame? Answer From Table 312.6(A), for one 4/0 conductor per terminal, the minimum depth required for the panel is 4 in. From Table 312.6(B), the minimum wire-bending space required is 7 in. Since the gutter is narrow, the 4/0 conductors would have to run vertically up or down inside the panel a distance of 7 in. after entering the panel before bending to terminate on a circuit breaker. Copyright 2013 by Patrick S. Ouillette, P.E.

72

422.23

Appliances

2014 NEC

Tire Inflation and Automotive Vacuum Machines Significance Not all ground-fault circuit-interrupter (GFCI) requirements are located in Article 210. This expansion of GFCI requirements is in Article 422 and applies to specific appliances. Analysis GFCI protection for personnel (5 mA) is required by the 2014 Code for tire inflation and automotive vacuum machines provided for public use. Much of this equipment is hard-wired and will be protected by GFCI circuit breakers, but GFCI receptacle protection is permitted. Where

this equipment is outdoors and is cord-and-plug connected, this is not a Code change, since outdoor convenience receptacles in public spaces have been required to be GFCI protected since the 2005 NEC. Most of this equipment is located outdoors subject to the elements and used by persons standing on conductive, sometimes wet, surfaces. Deteriorated electrical equipment expected to experience severe use is a good reason for requiring life-saving GFCI protection. All tire inflation equipment, but only automotive vacuum machines are covered by this requirement.

GFCI protection required

Tire inflation and automotive vacuum equipment

Summary The electrical supply for tire inflation and automotive vacuum machines provided for public use shall have GFCI protection for personnel. Application Question T F Only tire inflation and automotive vacuum machines supplied by 120-volt, 15- and 20-amp circuits are required to be GFCI protected. Answer False. The GFCI requirement is broadly stated and applies to any voltage and current rating, and

to both receptacle supplied and hard-wired (protected by a GFCI circuit breaker) equipment.


73

424.66(A) 210.12(A)and (B)

Fixed Electric Space-Heating Equipment

2014 NEC

Part VI. Duct Heaters – Installation – General – Limited Access Significance Specific requirements have been added for access to and working space about electric duct heaters installed in a space above a ceiling. Analysis Existing Code requires access to duct heaters and sufficient clearance to permit replacement of controls and heating elements and for adjusting and cleaning. Existing Code also states in the last sentence in 424.66: “See 110.26.” This is not mandatory language requiring compliance with the

working space rules in 110.26. Working space about electrical enclosures for resistance heating element-type duct heaters that are mounted on duct systems and contain equipment that requires adjustment, servicing, or maintenance while energized shall comply with the requirements of new subsection (B), Limited Access. Where the heating enclosure is located in a space above a ceiling, the following rules apply: (1) The enclosure shall be accessible through a lay-in type ceiling or an access panel(s). (2) The width of the working space shall be the width of the enclosure or a minimum of 30 in., whichever is greater. (3) All doors or hinged panels shall open to at least 90 degrees. (4) The space in front of the enclosure shall comply with the depth requirements in Table 110.26(A)(1). Ceiling grid T-bar shall be permitted in this space. This will make for a much safer work zone for service personnel working on ladders and around grounded metal objects above a suspended ceiling—metal building structure, metal piping, etc. Summary Installations of electric heaters in ducts above accessible ceilings shall have a working space width the greater of 30 in. or the width of the equipment, shall permit hinged panels to open at least 90°, and shall have a front working space depth in accordance with Table 110.26(A)(1). Application Question What is the depth of the front working space required by 424.66(B) for a 480-volt duct heater? (Assume no grounded parts opposite the heater.) Electric duct heaters

Courtesy of Rapid Cool

Answer From Table 110.26(A)(1): For the nominal voltage to ground range of 151–600 volts and Condition 1(no live or grounded parts on the other side of the working space), the required depth of the working space is 3 ft.


74

445.11

Generators

2014 NEC

Marking Significance For safe utilization of generators, it is necessary to know whether or not the generator neutral is connected to the frame of the generator. A new section requires that this information be marked on the generator. Analysis Generators can be connected for use as separately derived systems or as non-separately derived systems. Generators are used as stand-alone systems for recreational and other purposes, for

temporary power at construction sites, and for backup power supplying premises wiring for residences and small commercial properties. Different uses require different wiring connections, sometimes requiring the generator neutral to be bonded to the frame and sometimes requiring isolation between the generator neutral and generator frame. Often, generators are connected by persons not trained in electrical wiring. This is especially true of portable generators. Adverse weather conditions, standing water, and flexible power cords that may be subject to physical damage are all potential hazards related to the use of small portable generators. GFCI protection is required in most instances and is critical to the safe utilization of electricity supplied by portable generators. (See new Section 445.20 and existing Section 590.6(A)(3) for GFCI requirements on portable generators 15 kW or smaller.) In order for GFCI receptacles to operate properly, the neutral of the generator must be connected (bonded) to the generator frame. However, it cannot be readily determined whether or not the generator neutral is connected to the frame of the generator, nor can the bonding or lack thereof be necessarily modified in the field. Generators that employ a floating neutral are inherently safe, since the neutral point of the generator winding is not connected to the generator frame or to earth. Thus, there is no conductive path through earth for current supplied from the generator. Section 445.11 of the 2014 NEC requires the manufacturer to mark the generator denoting whether or not the generator neutral is bonded to the generator frame. If this connection is modified in the field, updated field marking is required that denotes whether or not the generator neutral is bonded to the frame of the generator. The location of any bonding connection is not required to be marked. In some cases, this connection is not accessible for field modification, nor is it required to be accessible. This Code change seeks to address safety concerns mainly associated with the use of portable generators, but the change also applies to stationary generators. Summary Generator manufacturers are required to mark the generator to denote whether or not the neutral of the generator winding is connected to the frame of the generator. If this connection is modified in the field, updated field marking is required that denotes whether or not the generator neutral is bonded to the frame of the generator.


75

445.11

Generators

2014 NEC

Application Question T F The manufacturer’s marking denoting whether or not the generator neutral is connected to the generator frame must include the location of any bonding connection. Answer False. The location of the bonding connection is not required to be marked. On some generators, the bonding connection is not intended to be accessible.

Required factory marking

Courtesy of Robin America Inc. Output panel of a Robin Subaru portable generator


76

445.20

Generators

2014 NEC

Ground-Fault Circuit-Interrupter Protection for Receptacles on 15-k W or Smaller Portable Generators Significance A new rule addressing ground-fault circuit-interrupter (GFCI) protection for personnel on small portable generators differentiates between stand-alone generators and those that will be connected to grounded premises wiring systems. Analysis The 2014 NEC requires that all 125-volt, single-phase, 15- and 20-amp receptacles that are part of

a 15-kW or smaller portable generator be provided with GFCI protection for personnel integral to the generator or receptacle, unless these receptacles are not available (switched off) when the generator’s 125/250-volt receptacle is being used. If the generator does not have a 125/250-volt locking-type receptacle, this requirement shall not apply. [If the generator was manufactured or remanufactured prior to January 1, 2015, listed cord sets or devices incorporating listed ground-fault circuit-interrupter protection for personnel identified for portable use shall be permitted.] The text in brackets is the essence of a Tentative Interim Amendment (TIA) 14-2, effective November 11, 2013. This action/section will be reevaluated as a proposal (public input) during the next Code cycle.

This new rule seeks to provide optimal safety by permitting, in some cases, the inherently safe “floating neutral” configuration frequently used for stand-alone systems. Where a generator is supplying 125/250-volt power to a building wiring system, the 125-volt, single-phase, 15- and 20amp receptacles must be made unavailable or equipped with GFCI protection. Many small portable generators are used by homeowners when utility power is lost, most commonly for outages due to storms. Often a flexible power cord is used as a patch cord to supply 120/240-volt power to the residence through a transfer switch that does not switch/break the neutral conductor. With this connection the generator neutral is now grounded (earthed) through the grounding electrode system of the utility service. Use of other receptacles on the generator without GFCI protection poses a hazard, since now a conductive path through earth has been established. The path can be traced from a point of contact with earth, to the grounding electrode system of the utility supplied service, to the service neutral, then back to the generator winding through the neutral conductor of the generator supply cord. The point of contact with earth could be a person standing on the ground operating a power tool where the metal frame of the tool has become accidentally energized. This makes a good case for the Code change. The inherent safety of the floating neural system is based on the fact that the neutral point of the generator winding (or one side of a winding that is not center-tapped) is isolated from the frame of the generator and earth ground. Thus, if a person standing on the ground contacts an energized metal part of equipment supplied from the generator, there is no shock hazard due to the lack of a current path through earth back to the power source. It is important to know whether or not the neutral is connected to the frame of the generator so that the generator can be connected correctly for safe operation. A related change in Section 445.11 of the 2014 NEC requires the manufacturer to mark the generator denoting whether the generator winding is bonded to the generator frame.


77

445.20

Generators

2014 NEC

This expands the 2011 Code change that required GFCI protection where these portable generators were used for temporary wiring, except that the GFCI requirements in 590.6(A)(3) also include 125-volt, 30-amp receptacles and 125/250-volt receptacles. Summary For generators manufactured beginning January 1, 2015, all 125-volt, single-phase, 15- and 20amp receptacles that are part of 15-kW or smaller portable generators shall be provided with GFCI protection for personnel integral to the generator or receptacle, unless these receptacles are not available (switched off) when the generator’s 125/250-volt receptacle is being used. This requirement shall not apply if the generator does not have a 125/250-volt locking-type receptacle.

125/250-volt lockingtype receptacle No GFCI protection is provided. Receptacles cannot be switched off. This generator is exempt from these new requirements (“grandfathered”) because of the date of manufacture.

Application Question T F Where a portable generator less than 15-kW is used for temporary power on a construction site, 125-volt, single-phase, 15- and 20-amp receptacles on the generator are not required to be GFCI protected. (The generator is not equipped with a 125/250-volt receptacle. The generator was manufactured after January 1, 2011.) Answer False. All 125-volt, single-phase, 15- and 20-amp receptacles that are part of 15-kW or smaller portable generators used for temporary power are required to be GFCI protected by Section 590.6(A)(3). Listed cord sets or devices incorporating listed GFCI protection identified for portable use are permitted for use with 15-kW or smaller portable generators manufactured or remanufactured prior to January 1, 2011. This section has not changed in the 2014 NEC. It is noteworthy that where the frame of a generator is bonded to the neutral and earthed with a suitable ground rod, a malfunctioning/failed GFCI receptacle on the generator will pose more of a

safety hazard to persons than a floating neutral generator with non-GFCI receptacles. With a floating neutral generator, two faults (a fault on each side of the winding with one side faulted to the frame) are necessary for a shock hazard to be present, but the voltage might be 240 volts.


78

450.10(A)

Transformers and Transformer Vaults

2014 NEC

Grounding – Dry-Type Transformer Enclosures Significance The Code contains new requirements and guidance for the connection of grounding and bonding conductors within transformer enclosures. Analysis Occasionally, inspectors will see electrical connections made to the metal grille or grating at the bottom of transformer enclosures. The grille shown in the photograph below will not easily accommodate connections, but other grilles might. The Code change states that where separate

equipment grounding conductors and supply-side bonding jumpers are installed, a terminal bar for the connection of all grounding and bonding conductors shall be secured inside the transformer enclosure. The terminal bar shall be bonded to the enclosure in accordance with 250.12 and shall not be installed on or over any vented portion of the enclosure. This will help to ensure proper transformer ventilation. Also, these metal grilles have not been evaluated as grounding and bonding equipment and are not suitable as a fault current path. The connections within the base of the transformer pictured are acceptable, since the metal grille is not used for connections and the connections are located suitably above the grille. Lug kits are available for these grounding and bonding connections. There is an exception for transformers with leads rather than terminals.

There are no electrical connections made to or on the metal grille, and ventilation is not hindered by electrical connections.

Bottom view of a dry-type transformer mounted on a wall and supported by brackets

OK

Summary Where separate equipment grounding conductors and supply-side bonding jumpers are installed, a terminal bar for the connection of all grounding and bonding conductors shall be secured inside the transformer enclosure. The terminal bar shall be bonded to the enclosure in accordance with 250.12 and shall not be installed on or over any vented portion of the enclosure. Application Question: What are the requirements of 250.12? Answer: Section 250.12, Clean Surfaces, requires nonconductive coatings (such as paint, lacquer, and enamel) to be removed from threads and other contact surfaces of equipment to be grounded to ensure good electrical continuity, unless the means of connection make it unnecessary to remove such coatings. Copyright 2013 by Patrick S. Ouillette, P.E.

79

450.11(B)

Transformers and Transformer Vaults

2014 NEC

Marking – Source Marking Significance A new subsection has been added to 450.11clarifying that it may be permissible to reverse feed (or back feed) a transformer. Analysis Perhaps the most common polyphase transformer in use is a step-down, 480-volt, delta-connected primary to a 208/120-volt, wye-connected secondary. A 3-phase transformer that steps up from 208-V to 480-V may not be as readily available as the common step-down transformer. Section

450.11(B) permits a transformer to be supplied at the marked secondary voltage provided the installation is in accordance with the manufacturer’s instructions. When a transformer is reverse fed, there are several factors that must be considered. A transformer is constructed for either a step-up or step-down function, having its primary and secondary winding impedances specifically designed for the purpose. When a secondary winding is supplied (becomes the primary), the value of the magnetizing inrush current will be very high, and an overcurrent protective device that will not trip upon energization must be sized in accordance with 450.3. Where primary taps and compensating windings are present, tap adjustments must be considered. Transformer grounding is also a concern. The neutral point of the wye-connected primary must not be grounded and must not be bonded to the transformer enclosure. A fan cooled transformer (general-purpose specialty transformer) cannot be reverse fed due to UL regulations. Designed as step-down transformer 480Δ – 208Y/120

H1

X1 X2

P2

P1

Load side

Supply side

S2

S1

X0

H2

S3

P3 H3

Connected reverse feed X3

Summary A transformer is permitted to be supplied at the marked secondary voltage (reverse fed) provided the installation is in accordance with the manufacturer’s instructions. Application Question Should the neutral point of the wye connection for the reverse fed transformer in the diagram above be grounded as a separately derived system? Answer No. The wye-connected supply side is not a separately derived system. The delta-connected side does constitute a separately derived system. The delta should be corner grounded (B phase).


80

Article 480

Storage Batteries

2014 NEC

Article 480 – Storage Batteries Significance Changes to this article involve accessibility to battery terminals, working space about battery systems, egress from battery rooms, and illumination of spaces containing battery systems. Analysis New subsection 480.8(C) requires that the terminals of all cells or multi-cell units be readily accessible for readings, inspection, and cleaning where required by the equipment design. One side of transparent battery containers shall be readily accessible for inspection of the internal

components. Subsection 480.9(C) has been expanded to provide side clearance for cell containers. For battery racks, a minimum clearance of 1 in. is required between containers and any wall or structure on the side not requiring maintenance. New subsection (D) has been added to address working space around top terminal batteries. Where top terminal batteries are installed on tiered racks, working space in accordance with the battery manufacturer’s instructions shall be provided between the highest point on a cell and the ceiling or battery row above. As in the previous Code, working spaces about battery systems shall also comply with 110.26. Courtesy of ACRAN Spill Containment Inc.

New subsection 480.9(E) requires that personnel doors intended for entrance to, and egress from, designated battery rooms open in the direction of egress and be equipped with listed panic hardware. Illumination requirements are set forth in new subsection 480.9(G). Illumination shall be provided for working spaces containing battery systems. The lighting outlets are not permitted to be controlled by automatic means only. If the work space is illuminated by an adjacent light source, additional lighting outlets shall not be required. The location of luminaires shall not: (1) Expose personnel to energized battery components while performing maintenance on the luminaires in the battery space; or (2) Create a hazard to the battery upon failure of a luminaire. Summary The terminals of all cells shall be readily accessible. A minimum side clearance of 1 in. shall be maintained between a cell container and any wall or structure. Top terminal batteries require

vertical working space in accordance with the battery manufacturer’s instructions. Doors in battery rooms shall open in the direction of egress and be equipped with listed panic hardware. Illumination shall be provided for working spaces containing battery systems, with specific rules for locating luminaires.


81

517.18

Health Care Facilities

2014 NEC

General Care Areas – Patient Bed Location – Patient Bed Location Receptacles Significance Several changes have been made in the 2014 NEC to harmonize with NFPA 99, Health Care Facilities Code. One significant change is the increase in required receptacles at patient bed locations. Analysis The number of required receptacles at patient bed locations in general care areas has increased from four to eight “hospital grade” receptacles. As in the previous Code, the receptacles are

permitted to be of the single, duplex, or quadruplex type, or any combination of the three. Also, to harmonize with NFPA 99, the term emergency system is no longer used in Article 517. Instead of being considered branches of the emergency system, the life safety branch and the critical branch are branches of the essential electrical system. One or more branch circuits supplying patient bed locations in general care areas shall be from the normal system and one or more branch circuits shall be from the critical branch (rather than from the emergency system). The receptacles or cover plates of receptacles supplied from the critical branch(s) shall have a distinctive color or marking so as to be readily identifiable and shall also indicate the panelboard and branch circuit number supplying them. This is an existing requirement for patient bed locations in critical care areas. Summary The minimum number of receptacles required at patient bed locations in general care areas has been increased from four to eight. Application Question T F A patient bed location with four duplex receptacles satisfies the NEC requirement in 517.18 for the minimum number of required receptacles. Answer True. A receptacle is a contact device. A duplex receptacle consists of two contact devices. See the definition of receptacle in Article 100. Code Refresher  517.13 – Redundant grounding is required in patient care areas of health care facilities. To accomplish this, the wiring method must be a metal raceway system or a cable having a metallic armor or sheath that qualifies as an equipment grounding conductor in accordance with 250.118. The redundant grounding requirement applies also to patient care areas in nursing homes, clinics, medical and dental exam rooms, therapy areas, and similar rooms or areas where electrical equipment is used in the treatment of patients. An example of where the requirement does not apply is a physiologist’s office where counseling is given.


82

517.18 and 517.19


2014 NEC

Patient Bed Locatio n

General Care Areas: Minimum of eight receptacles required Critical Care Areas: Minimum of fourteen receptacles required

Critical branch

Normal system

For patient bed locations in general care areas, the receptacles or cover plates of receptacles supplied from the critical branch(s) shall have a distinctive color or marking so as to be readily identifiable and shall also indicate the panelboard and branch circuit number supplying them. This is an existing requirement for patient bed locations in critical care areas.


83

517.19


2014 NEC

Critical Care Areas – Patient Bed Location Branch Circuits – Patient Bed Location Receptacles Significance In order to harmonize with NFPA 99,Health Care Facilities Code, the number of required receptacles at patient bed locations in critical care areas has been increased from eight to fourteen. Analysis As stated in the analysis of changes to 517.18, the term emergency system is no longer used in Article 517. The three branches of the essential electrical system are the equipment branch, the

life safety branch, and the critical branch. One or more branch circuits supplying patient bed locations in critical care areas shall be from the normal system and one or more branch circuits shall be from the critical branch. The receptacles must be listed “hospital grade” and so identified. The minimum number of receptacles required at patient bed locations in critical care areas has increased from eight to fourteen. At least one of the receptacles shall be connected to either: 1) a normal system branch circuit, or 2) a critical branch circuit supplied by a different transfer switch than the other receptacles at the same patient bed location. The receptacles are permitted to be of the single, duplex, or quadruplex type, or any combination of the three. Summary

The minimum number of receptacles required at patient bed locations in critical care areas has increased from eight to fourteen. Application Question T F All receptacles at a patient bed location in a critical care area are permitted to be supplied from the critical branch to enhance reliability of electric supply. Answer True, with conditions. All receptacles are permitted to be supplied from the critical branch, provided that at least one circuit is supplied from a different transfer switch than the other receptacles. If all circuits are supplied from the same transfer switch, there is more potential hazard than where the circuits are supplied from the normal system and the critical branch. If all receptacles are supplied from the critical branch and connected to the same transfer switch, a malfunction of the transfer switch (e.g., not reconnecting to normal power after a generator test) will leave the bed location with no power.


84

517.19(C)


2014 NEC

Critical Care Areas – Operating Room Receptacles Significance This is a new subsection that contains requirements for operating room receptacles. It is intended to coordinate NEC requirements with requirements of NFPA 99. Analysis This new section requires that there be a minimum of thirty-six receptacles in operating rooms of health care facilities. As is the case for patient bed locations, the receptacles are permitted to be of the single, duplex, or quadruplex type, or any combination of the three.

At least twelve of the receptacles shall be supplied from either: 1) The normal system branch circuit required in 517.19(A), or 2) A critical branch circuit supplied from a different transfer switch than the other receptacles at the same location. The receptacles shall be listed “hospital grade” and be so identified. The grounding terminal of each receptacle shall be connected to the reference grounding point by an insulated copper equipment grounding conductor. The reference grounding point is the ground bus of the panelboard or isolated power system panel supplying the patient care area. Summary Each operating room shall be equipped with a minimum of thirty-six receptacles, at least twelve of which shall be supplied from a normal circuit or a critical circuit connected to a different transfer switch than the other receptacles at the same location. Application Question T F At least twelve operating room receptacles must be connected to a normal circuit. Answer False. In lieu of one or more normal circuits, all operating room receptacles are permitted to be connected to the critical branch, provided that at least twelve are supplied from a separate transfer switch than the other receptacles at the same location. Code Refresher  The requirement for “hospital grade” receptacles in general care and critical care areas is not retroactive. They are required to be installed when receptacles are being replaced in locations where the present Code mandates hospital grade receptacles, and where there is a modification of building use or renovation of a health care facility.


85

517.19(C)


2014 NEC

Receptacles on equipment are included in the minimum 36 required receptacles.

Hospital operating room

More on Health Care Facilities

In addition to the NEC, some of the other standards that designers of health care facilities will need to consult are NFPA 72, National Fire Alarm Code; NFPA 99, Health Care Facilities Code; NFPA 101, Life Safety Code; and NFPA 110, Standard for Emergency and Standby Power Systems. Important design information concerning classification of essential electrical systems can be found in NFPA 99 and NFPA 110.


86

517.30(G)


2014 NEC

Essential Electrical Systems for Hospitals – Coordination Significance Selective coordination of overcurrent protective devices serving essential electrical systems in hospitals is no longer required. Instead, coordination is required. Analysis Selective coordination involves the selection and application of overcurrent protective devices, for the full range of overcurrents and opening times, such that only the upstream overcurrent device closest to a fault or overload condition will open. This minimizes interruption of power and

localizes the outage. Section 517.26 requires that the life safety branch meet the requirements of Article 700 – Emergency Systems, except as amended by Article 517. Section 700.28 requires that emergency system overcurrent devices be selectively coordinated with all supply side overcurrent protective devices. Section 517.30(G) effectively amends this requirement. As a result of the Task Group 2014 NEC/2012 NFPA 99 Correlation efforts, selective coordination of overcurrent devices for hospital essential electrical systems has undergone a significant change. Rather than a fully coordinated system, overcurrent protective devices serving the essential electrical system shall be coordinated for the period of time that a fault’s duration extends beyond 0.1 second. This coordination does not cover the full range of overcurrent conditions. The 0.1 second at 60 Hz is equivalent to six cycles. Faster clearing times can be accomplished, particularly with the use of fuses. This could be seen as a relaxation of standards, since many systems have been successfully coordinated at 100% (total coordination). Total coordination is synonymous with selective coordination. Other systems in the Code still require selective coordination rather than coordination. By exception, coordination is not required between transformer primary and secondary overcurrent protective devices, where there is only one overcurrent device or set of overcurrent protective devices on the transformer secondary. A second exception to the rule is where overcurrent devices of the same ampere rating are connected in series. In the 2014 NEC, the essential electrical system does not consist of an emergency system and an equipment system. Instead, the essential electrical system consists of three branches: the life safety branch, the critical branch, and the equipment branch (equipment system in the 2011 NEC). The life safety branch and the critical branch are no longer referred to as components of an emergency system. Since the equipment branch is part of the essential electrical system, this new Code section requires coordination of the overcurrent protection for the equipment branch also. Summary Overcurrent protective devices serving the essential electrical system in hospitals shall be coordinated for the period of time that a fault’s duration extends beyond 0.1 second. Application Question T F The coordination of overcurrent protective devices required in this section is applicable to essential circuits only when supplied by the emergency source. Copyright 2013 by Patrick S. Ouillette, P.E.

87

517.30(G)


2014 NEC

Answer False. Coordination between overcurrent protective devices must be accomplished for both the normal and emergency power sources. The essential branches for which coordination is required are supplied by both the normal and emergency sources. Normal source

Emergency source

N

Note that the system must be coordinated for both the normal and emergency sources.

EM

In the event of an overcurrent, only the OCPD immediately upstream opens in a coordinated system.

ATS

Location of overcurrent event

X

For essential electrical systems in hospitals, coordination of overcurrent protective devices is required after 0.1 second of the onset of an overcurrent.

Code Refresher  517.17 – Where a second level of ground-fault protection of equipment (GFPE) is applied as required in 517.17(B), the selectivity required by 517.17(C) must be considered in the overall coordination of overcurrent protective devices for essential electrical systems. The GFPE coordination must be fully selective. The requirement for the next level of GFPE protection is not based on the feeder circuit rating, since the function of the device is to provide selectivity between the feeder and service overcurrent protective devices.


88

547.5(F) Agricultural Buildings

555.15(B) Marinas and Boatyards

2014 NEC

547.5(F) Wiring Methods – Separate Equipment Grounding Conductor 555.15(B) Grounding – Type of Equipment Grounding Conductor Significance The long-standing prohibition against aluminum equipment grounding conductors for wiring in and about agricultural buildings and marinas and boatyards has been lifted. Analysis The requirement for a copper equipment grounding conductor (EGC) for wiring in and about agricultural buildings first appeared in the 1987 NEC. The intent was to improve the longevity of EGCs in the harsh, corrosive, and often wet locations associated with many agricultural buildings. Metal raceways were not permitted to serve as the required EGC. Interestingly, in Section 310.14 of the same Code edition, the NEC first r equired aluminum conductors to be constructed of an AA-8000 series electrical grade aluminum alloy. Along with improved testing of termination equipment for aluminum conductors, the modified properties of aluminum building wire have enabled good performance of aluminum wiring in agricultural settings. Analysis of the conductor’s exposure to common corrosive gases found in agricultural settings has shown that aluminum conductors generally perform well and are suitable for these environments.

Note: Aluminum EGCs shall not be terminated within 18

″

of the earth [250.120(B)].

Both copper and aluminum equipment grounding conductors are permitted for agricultural buildings and marinas.

Article 555 covers wiring and equipment in and about public and private facilities for docking, repair, storage, and fueling of small watercraft (not exceeding 300 tons). Private facilities associated with a single-family dwelling are not within the scope of this article. For about a half century, copper EGCs have been required for circuits in and about marinas and boatyards. However, decades of aluminum wire use for phase and neutral conductors, exposed to the corrosive conditions associated with these locations, has shown satisfactory operation in both fresh and salt water environments. An aluminum conductor exposed to air will become coated with a nonconductive film of aluminum oxide that will serve to slow or inhibit corrosion. Terminations are important, particularly where cables are attached to floating (movable) piers. Summary Aluminum EGCs are now permitted for wiring in and about agricultural buildings and marinas

and boatyards. Where installed underground in agricultural locations, the EGC shall be insulated or covered. In marinas and boatyards, the EGC shall be insulated. Application Question: Are aluminum or other metal raceways now permitted as EGCs? Answer: No. For Article 547 and Article 555 locations, wire-type EGCs are required.


89

551.71

Recreational Vehicles and Recreational Vehicle Parks

2014 NEC

Part VI. Recreational Vehicle Parks – Type Receptacles Provided Significance Additional 30-ampere, 125-volt receptacles at recreational vehicle sites are now required. This change will enhance safety by reducing the use of adapter cords. Analysis Existing Code requires at least 20% of electrified sites to be equipped with a 50-ampere, 125/250volt receptacle. The 2014 NEC requires that these 50-A sites also be equipped with a 30-ampere, 125-volt receptacle. The revised receptacle provisions/distribution can be summarized as follows: • •

•

• •

All sites with electric power shall be equipped with at least one 20-A, 125-V receptacle. At least 70% of sites with electric power shall be equipped with a 20-A, 125-V receptacle and a 30-A, 125-V receptacle. At least 20% of sites with electric power shall be equipped with a 20-A, 125-V receptacle; a 30-A, 125-V receptacle; and a 50-A, 125/250-V receptacle. Any electrified site may provide additional receptacles of any of the three types specified. Tent sites with 15- or 20-A receptacles need not be included in the percentage distribution.

The recreational vehicle (RV) power panel below meets the requirements for the minimum 20% of sites equipped with 30- and 50-A receptacles—and the requirements for any site. Note the 30-A, 125-V configuration is a specific purpose configuration for travel trailers (NEMA TT-30R). Summary Every RV site equipped with a 50-A, 125/250-V receptacle shall also provide a 30-A, 125-V receptacle. Application Question Plans for a new RV park include 25 dedicated tent sites, 10 sites with a 20-A, 125-V receptacle. There will be 100 additional RV sites, 90 of which will be electrified. What are the minimum requirements in terms of receptacle types at the sites? Answer The dedicated tent sites are not considered in the percentage distribution of receptacle types. All 90 electrified sites shall have a 20-A, 125-V receptacle. At least 18 sites shall be provided with a 20-A and a 30-A 125-V receptacle, along with a 50-A, 125/250-V receptacle. At least 63 sites shall be provided with a 20-A and a 30-A, 125-volt receptacle. These 63 sites may or may not also provide a 50-A receptacle. So, only 45 more sites equipped with 30-A are required (63 – 18 = 45). Code Refresher 



551.73 – Electrical service and feeder loads shall be based on 9600 VA per site equipped with a 50-A receptacle, 3600 VA for sites with both 20- and 30-A receptacles, and 2400 VA for sites with only a 20-A receptacle. The load for tent sites equipped with only a 20-A receptacle shall be 600 VA/site. The demand factors in Table 551.73(A) shall apply. 551.73(D) – The minimum ampacity for feeder conductors for RV sites is 30 A.


90

590.4(I) and (J)

Temporary Installations

2014 NEC

General – Termination(s) at Devices – Support Significance This change seeks to align with OSHA regulations. It will afford a greater level of safety in the construction environment where temporary electrical power is used. Analysis It is not uncommon to find feeder and branch-circuit cables on the ground or on the floor at constructions sites. These environments are often wet. Cables on walking surfaces pose a tripping hazard and are not afforded suitable protection from damage. Language added to 590.4(J) states

that cable assemblies and flexible cords and cables installed as branch circuits or feeders shall not be installed on the floor or on the ground. Extensions cords are exempt from this requirement, since these cords are designed and suitable for this purpose. GFCI protection is provided where extension cords are used. A separate change in subsection (I) pertains to flexible cords and cables entering enclosures containing devices that require termination. The cords and cables shall be secured to boxes with fittings “listed for connecting flexible cords and cables to boxes….” The previous language was “fittings designed for the purpose,” which is essentially the definition of identified. A listed fitting will provide a higher degree of suitability. This will help to prevent any connector that will “fit” on a cable from being used. The connector/fitting should keep the cable secured and protected. This will keep terminations tight and reduce the possibility of having exposed conductors or short circuits caused by damaged conductors.

Temporary Power Distribution System OSHA-Approved Lighti ng String Feeder and branch-circuit cables used for Courtesy of Hubbell Incorporated Courtesy of Precision Lighting temporary wiring are not permittedon Hubbell Wiring Device – Kellems floors or on the ground.

Summary For temporary wiring installations, cable assemblies and flexible cords and cables installed as branch circuits or feeders shall not be installed on the floor or on the ground. Flexible cords and cables entering enclosures containing devices that require termination shall be secured to the boxes with fittings listed for connecting flexible cords and cables to boxes. Application Question Is a remodeling project where temporary wiring is used subject to the rules in Article 590? Answer Yes. This article applies to temporary electrical installations used during the period of construction, remodeling, maintenance, repair, or demolition of buildings, structures, equipment, or similar activities. Copyright 2013 by Patrick S. Ouillette, P.E.

91

600.6(A)(1)

Electric Signs and Outline Lighting

2014 NEC

Disconnects – Location – At Point of Entry to a Sign Enclosure Significance This change will reduce the risk of persons contacting energized conductors within a sign. Analysis As with the existing Code, the 2014 NEC permits the disconnecting means for a sign (or outline lighting) to be at the sign, within sight of the sign, or out of sight of the sign if lockable in the off position. Some signs have the disconnecting means mounted on the sign enclosure or support pole. Where the disconnecting means is at the sign, a new subsection requires the disconnect to be located at the point where the supply circuit(s) enters the sign enclosure or pole. Conductors on the line side of the disconnecting means are not permitted to enter the sign enclosure or pole to run to an internal disconnect switch or to an externally operable switch. An exception allows circuit conductors to pass through a sign without complying with the disconnect requirement, where the circuit conductors are enclosed in a Chapter 3 listed raceway.

This rule applies to all types of electric sign and outline lighting installations (conductors, equipment, and field wiring) within the scope of Article 600. Article 600 covers the use of traditional lighting sources, neon tubing, and light-emitting diodes (LEDs). The rule applies to signs installed on buildings, poles, and other structures, and includes portable signs.

Papers, etc. Office Supply

Books - R-Us

Energized conductors are not permitted to enter a sign enclosure or pole. Energized conductors are permitted to pass through a sign, where the circuit conductors are enclosed in a Ch. 3 listed raceway.

Fashion Mart

Disconnect is permitted to be “out of sight of” sign if capable of being locked open.

Circuit breaker(s) as disconnecting means

Feeder or branch circuit(s)

Disconnecting means must comply with 110.25.

Summary Where a sign disconnecting means is at the sign, the disconnect shall be located at the point where the feeder or branch circuit(s) enters the sign enclosure or pole and shall disconnect all wiring where it enters the enclosure of the sign or pole. A disconnect at the point conductors enter a sign

is not required for conductors enclosed in a Chapter 3 listed raceway that passes through the sign. Application Question: Are the supply conductors for a sign permitted to emerge from the ground inside of the sign pole? Answer: This is permissible only where the required disconnect is located other than at the sign.


92

ARTICLE 646 – Modular Data Centers

2014 NEC

Modular Data Centers Significance Existing Article 645 – Information Technology Equipment is not applicable to equipment that does not meet all of the conditions listed in 645.4. Generally, Modular Data Centers (MDCs) are factory wired. The unique construction and broad range of sizes and types of MDCs requires clear direction for the application of existing Code rules and new requirements for safe electrical installation of MDCs. Analysis

Many MDCs are not considered ITE rooms, which, among other reasons, set these data centers outside the scope of Article 645. Modular Data Centers, sometimes referred to as Containerized Data Centers, are prefabricated equipment enclosures or structures that contain information technology equipment (ITE) and related power, UPS (uninterruptible power supply) systems, HVAC (heating, ventilation, and air-conditioning) systems, monitoring equipment, etc. All equipment can be located within the same module or related equipment may be located in an adjacent separate module or structure. MDCs are intended for fixed installation either indoors or outdoors. An approved disconnecting means in accordance with 645.10 is required for disconnection of the IT equipment. A similar approved disconnecting means is required to disconnect HVAC equipment serving the MDC, which shall also cause all required fire/smoke dampers to close. For MDCs that are listed and labeled, only compliance with Sections 646.5 through 646.9 is required, in addition to the requirement for disconnecting means (see 646.4). Otherwise, all provisions of the article must be complied with, including specific requirements for illumination, emergency illumination, receptacles, work space, egress, and other requirements. Much of the article directs the Code user to applicable sections of existing articles for application in MDCs. Flexible power cords are not permitted for connection to external power sources but may be used for connection between modules. Generally, working space requirements must be in accordance with 110.27 (110.26 in the 2011 NEC), with some less restrictive rules for working space about IT equipment where the voltage of live parts exposed for servicing is limited to 30 volts rms or 60 volts dc. Summary New Article 646 – Modular Data Centers contains requirements for prefabricated structures or enclosures that house IT equipment and related systems such as power, back-up power, HVAC, and others. The article contains specific new requirements and directs Code uses to applicable existing requirements in other articles.

Application Question T F The portability of MDCs requires that flexible power cables be used for service or feeder conductors to supply MDCs from external power sources.


93

ARTICLE 646 – Modular Data Centers

2014 NEC

Answer False. Flexible power cables are not permitted for this use. However, where not subject to physical damage, extra-hard usage cords may be run between MDC enclosures, e.g., from an ITE enclosure to an adjacent enclosure housing HVAC equipment for the ITE. MDCs are intended for fixed installation rather than as portable equipment.

Indoor MDC

Courtesy of Mainline Computer Products, Inc.

Cut view of portable data center inside shipping container •

•

20’ x 8’ shipping container 7 racks (6 racks with a total of 240 rack units available for servers)

Courtesy of Sun Microsystems, Inc. and Data Center Professionals.net

Electric service for outdoor (container) MDC

Courtesy of Sun Microsystems, Inc. and PRWeb


94

680.22(B)(6) Swimming Pools, Fountains, and Similar Installations

2014 NEC

Part II. Permanently Installed Pools – Lighting, Receptacles, and Equipment – Luminaires, Lighting Outlets, and Ceiling-Suspended (Paddle) Fans – LowVoltage Luminaires Significance This new subsection permits qualifying low-voltage luminaires (e.g., site lighting) to be installed around pools less than 5 ft from the inside walls of the pool. Analysis In previous Codes, no luminaire could be installed within 5 ft horizontally of the inside walls of a

pool unless luminaire waslevel, located significantly above the surface of the maximum level (5 ft to 12 ftthe above the water depending on the installation). Article 411 lighting water systems (30 volts maximum or connected to a Class 2 power source) could not be installed within 10 ft of pools, unless permitted by Article 680 [see 411.4(B)]. The low voltage contact limit introduced in the 2011 NEC in 680.2 is key to this new permission. The contact limit replaced the long standing 15-volt AC threshold because of the need to address new technology luminaires operating on DC and nonsinusoidal wave forms. The AC and DC voltage limits establish a safe voltage level for circuit operation. Qualifying luminaires must have a voltage rating in accordance with the low voltage contact limit in 680.2 and be supplied from a power source meeting the isolation requirements for swimming pool lighting in 680.23(A)(2). Low-voltage landscape lighting power units complying with UL 1838 that are marked “For Use with Submersible Fixtures” meet the isolation requirements in 680.23(A)(2) and comply with the low voltage contact limit. Summary Listed low-voltage luminaires not requiring grounding and not

exceeding the low-voltage contact limit shall be permitted to be located less than 5 ft from the inside walls of a pool. The luminaires shall be supplied by a listed transformer or power supply of the isolated winding type or that incorporates a system of double insulation between the primary and secondary windings in accordance with 680.23(A)(2). Qualifying low-voltage lighting is permitted to be located within 5 ft of the inside walls of a pool.

Application Question: What is the low voltage contact limit set forth in 680.2? Answer: A voltage not exceeding the following values: (1) 15 volts (RMS) for sinusoidal ac (2) 21.2 volts peak for nonsinusoidal ac (3) 30 volts for continuous dc (4) 12.4 volts peak for dc that is interrupted at a rate of 10 to 200 Hz


95

680.42(B) and (C) Swimming Pools, Fountains, and Similar Installations

2014 NEC

Part IV. Spas and Hot Tubs – Outdoor Installations – (B) Bonding – (C) Interior Wiring to Outdoor Installations Significance This change appropriately exempts certain outdoor spas and hot tubs from the perimeter bonding requirement. The change began as a Tentative Interim Amendment (TIA 11-1) to the 2011 NEC issued by the Standards Council on March 1, 2011 with an effective date of March 21, 2011. Analysis A TIA is tentative because it has not been processed through the entire standards-making process. It is interim because it is only effective until the next edition of the Code (2014). It automatically

becomes a proposal for the 2014 NEC. The interim amendment exempted outdoor installations of listed self-contained hot tubs and spas from the requirement for equipotential bonding of perimeter surfaces in 680.26(B)(2), provided the installation met certain requirements. The amendment has been revised and accepted into the 2014 NEC. Equipotential bonding of perimeter surfaces shall not be required where all of the following conditions apply: (1) The spa or hot tub shall be listed as a self-contained spa for aboveground use. (2) The spa or hot tub shall not be identified as suitable only for indoor use. (3) The installation shall be located on or above grade and comply with the manufacturer’s instructions. (4) The top rim of the spa or hot tub shall be at least 28 in. above all perimeter surfaces that are within 30 in. horizontally from the spa or hot tub. The height of nonconductive external steps for access to the spa or tub shall not affect the rim height measurement. The revision will provide relief for homeowners and guidance for contactors and inspectors where a spa or hot tub is intended to be installed at an outdoor location, such as on a stone patio or other finished surface, where it is not feasible to install perimeter bonding. The change recognizes the different safety needs of permanently installed, custom in-ground spas or hot tubs and listed selfcontained portable units. This is in harmony with existing Code that exempts storable pools and listed self-contained spas or hot tubs installed indoors from the perimeter bonding requirement. Summary Perimeter equipotential bonding is not required for self-contained spas or hot tubs that are indoor/outdoor rated and listed according to UL 1563 standards. Outdoor installations of self-contained spas or hot tubs where perimeter bonding is not required for listed units

Also, 680.42(C) now permits any Chapter 3 wiring method (with a min. 12 AWG copper EGC that is insulated or within an overall jacket) to be used in the interior of any dwelling unit or associated building for the supply to an outdoor spa or hot tub. Previously, this was only permitted for one-family dwellings. Specific wiring methods are still required for underwater luminaires. Application Question: Is equipot. bonding of perimeter surfaces required for in-ground spas? Answer: Yes. An in-ground spa does not meet the conditions in 680.42(B).


96

690.12 and 690.56(C)

Solar Photovoltaic (PV) Systems

2014 NEC

Rapid Shutdown of PV S ystems on Buildings Significance Provisions are now required for the rapid shutdown of PV circuits for the safety of first responders/firefighters. Analysis The Code seeks to establish safe circuits (“controlled conductors” that are touch safe) for the portion of conductors more than 10 ft from a PV array and for conductors that are more than 5 ft in length installed inside of buildings and associated with PV systems. This applies to all PV

output conductors, inverter inputs, inverter outputs, and energy storage (battery) circuits. The controlled conductors shall be limited to not more than 30 volts and 240 volt-amperes within 10 seconds of rapid shutdown initiation. The 10 seconds will allow dc-side capacitor banks to discharge by means other than contactors and shunt-trip devices. The rapid shutdown equipment/hardware shall be listed and identified as suitable for the purpose. Voltage and power shall be measured between any two conductors and between any conductor and ground. The rapid shutdown initiation methods shall be labeled in accordance with 690.56(B), which requires a permanent plaque or directory showing the location of the service disconnect and the PV system disconnect if not installed at the same location. Ideally, the service disconnect and the required PV system disconnect would be located outdoors adjacent to one another. Building wall

Rooftop PV modules 10 ft max.

Inverter output “controlled conductors”

10 ft max.

Rapid shutdown equipment Combiner box

More than 5 ft

Inverter DC

AC

“Controlled conductors” 10 ft max.

Zone of energized conductors (more than 30 V and 240 VA)

Outdoor “controlled conductors”

PV inverter input “controlled conductors”

Indoor PV conductors, including battery conductors, more than 5 ft in length must be “controlled conductors.”

This new NEC section does not contain prescriptive requirements. Existing section 690.13 requires the PV disconnecting means to be installed at a readily accessible location on the outside of a building or inside nearest the point of entrance of the system conductors. The diagram below shows the required PV system disconnect adjacent to the service disconnect. Some methods of accomplishing the emergency shutdown currently exist and other solutions will evolve within the solar industry. Modules with micro-inverters are an easy solution, since modules will shut down on loss of utility power. For systems that use an inverter for a string or array, loss of utility power will shut down the inverter output, but source circuits will remain


97

690.12 and 690.56(C)

Solar Photovoltaic (PV) Systems

2014 NEC

energized. The required readily accessible PV system disconnect will not shut down dc output circuits on roofs; rather, the modules will continue to generate power during daylight hours. “Power optimizers” could be used on each module and would limit module output to 1 volt upon loss of a signal from the inverter. Also, tenKsolar’s RAIS® Wave system can electronically control output at the module level when a disconnect is opened. New section 690.56(C) requires that buildings with both a utility service and a PV system have a permanent plaque or directory including the following wording: PHOTOVOLTAIC SYSTEM EQUIPPED WITH RAPID SHUTDOWN. The plaque or directory shall be reflective, with all letters capitalized and a minimum of 3/8 in. high, in white on red background. Rapid shutdown equipment using control signal Roof Signal over power conductors

Photovoltaic System Disconnect

Plaque or directory shall be reflective, with all letters capitalized and having a minimum height of 3/8 , in white on red background. ″

PHOTOVOLTAIC SYSTEM EQUIPPED WITH RAPID

Service Disconnect

SHUTDOWN

PHOTOVOLTAIC SYSTEM EQUIPPED WITH RAPID SHUTDOWN

Summary Rapid shutdown of PV circuits is required for the portion of conductors more than 10 ft from a PV array and for conductors that are more than 5 ft in length installed inside of buildings and associated with PV systems. This applies to all PV output conductors, inverter inputs, inverter outputs, and energy storage (battery) circuits. The “controlled conductors” shall be limited to not more than 30 volts and 240 volt-amperes within 10 seconds of rapid shutdown initiation. The rapid shutdown equipment/hardware shall be listed and identified as suitable for the purpose. Application Question T F PV system conductors within a building must be controlled conductors via rapid shutdown equipment if the conductors are longer than 5 ft from the point where the conductors penetrate the exterior wall. Answer True. However, the point of penetration of the outside wall is not significant. All indoor PV system related conductors more than 5 ft in length must be controlled conductors. This includes PV related conductors srcinating and terminating within the building, e.g., battery conductors.


98

Article 694

Small Wind Electric Systems

2014 NEC

Wind Electric Systems Significance The scope of Article 694 has changed and a new section has been added containing requirements for turbine shutdown. Analysis Article 694, Small Wind Electric Systems, was introduced in the 2011 NEC and contained installation requirements for wind generators up to and including 100 kW. This article now covers wind generators of any size that are within the scope of the NEC in 90.2, hence the change in the

title of the article. New Section 694.23 requires wind turbines to have a readily accessible manual shutdown button or switch. Operation of the switch shall result in a parked turbine state that shall either stop the turbine rotor or allow limited rotor speed combined with a means to de-energize the turbine output. A manual shutdown button or switch is not required for turbines with a swept area of less than 538 ft2. The shutdown procedure shall be defined and posted at the location of a shutdown means and at the location of the turbine controller or disconnect, if the location is different. All 125-V, 15- or 20-A receptacles installed for maintenance of a wind turbine are required to have 5-mA GFCI protection. Outdoor receptacles already require GFCI protection by 210.8(B), but this requirement will cover receptacles in towers and accessory buildings related to wind generators.

Portion of foundation, and structure grounding for a

A turbine support pole or tower is permitted to be used as a raceway if evaluated as part of the listing of the wind turbine or otherwise listed or evaluated for the purpose.

3 MW wind turbine

Summary Article 694 now covers all wind generators within the scope of the NEC—no longer limited to 100 kW or smaller. Provisions for manual shutdown are now required. Application Question A privately owned wind farm consisting of 1.6 MW turbines connects to the grid and sells energy to electric utilities. Is the installation covered by the NEC View of climbing tower inside a 3 MW wind turbine structure

?

Answer The field wiring for the turbines/structures, and perhaps the substation, is within the jurisdiction of the NEC. There will be an agreed to point of demarcation where the utility jurisdiction begins. Copyright 2013 by Patrick S. Ouillette, P.E.

99

700.8

Emergency Systems

2014 NEC

Surge Protection Significance Implementation of this rule could prevent damage to emergency power controls and critical electronic loads, thereby enhancing the reliability of emergency systems. Analysis This new section applies to emergency systems, which are legally required systems that automatically supply power to designated loads upon loss of normal power. The rule requires a listed surge-protective device (SPD) to be installed in or on all switchboards and panelboards supplying emergency systems. The intent of this rule is to enhance the reliability of emergency systems by mitigating potential damage from surges to electronic control and communications systems and sensitive loads. SPDs are currently required for power sources of Critical Operations Power Systems (COPS) in 708.20(D). Photo shows SPD mounted directly to the p anelboard’s busbars. SPD Series, Courtesy of Eaton Corporation www.eaton.com/consultants

Section 700.8 does not specify the level of protection required, but guidelines for protection are available through several sources. One source is ANSI/IEEE C62.41, IEEE Recommended Practice for Surge Voltages in Low-Voltage AC Power Circuits. The consulting and specifying engineering community through the American Institute of Architects (AIA) has produced a MasterSpec document related to SPDs for low-voltage electrical power circuits. It references a protection level of 250 kA at service entrance locations. Section 4.18 of NFPA 780, Standard for the Installation of Lightning Protection Systems, contains prescriptive requirements for surge protection systems installed for electrical and communications systems, including protection levels. According to Section 4.18.3.1.2 of NFPA 780, SPDs at the service entrance shall have an Imax rating of at least 40 kA 8/20 μs per phase or a nominal discharge current (In) rating of at least 20 kA 8/20 μs per phase for the protection of electrical power circuits. The 8/20 μs terminology is a reference to the Combination Wave generator described in IEEE C62.41.2 used to simulate lightning induced transient activity. The combination wave is characterized by short duration, high-frequency 8-by-20 μs (maximum current in 8 μs and 50% of maximum after 20 μs) current and 1.2-by-50 μs voltage waveforms. Summary A listed SPD shall be installed in or on all emergency systems switchboards and panelboards. Application Question What Type of SPD is required for protection? Answer Section 700.8 does not specify the Type or level of protection. Consult Article 285, SurgeProtective Devices (SPDs), 1000 Volts or Less, for requirements on the use and installation of SPDs. The article contains rules for Type 1, Type 2, Type 3, and Type 4 SPDs, based on UL 1449. Copyright 2013 by Patrick S. Ouillette, P.E.

100

700.16

Emergency Systems

2014 NEC

Part IV. Emergency System Circuits for Lighting and Power – Emergency Illumination Significance Emergency illumination is now required in certain electrical rooms. Analysis Emergency systems are installed where electrical systems are essential for the safety of human life. They are required in certain occupancies to illuminate means of egress or critical task areas and to supply power for life-support equipment, critical alarm systems, fire pumps, elevators, etc. Emergency systems are installed in high occupant load buildings such as places of assembly,

shopping malls, institutional facilities, and where life-support equipment is used such as in hospitals. Where an emergency system is installed, emergency illumination must be provided in the area of the disconnecting means required in 225.31 (a main disconnect in a separate building supplied by a feeder or branch circuit) and 230.70 (a service disconnect). The rule is applicable where the service disconnect or main disconnecting means is installed indoors. The purpose of the change is to enhance the safety of persons working on electrical equipment and to aid first responders in disconnecting building power. Unit equipment (rechargeable battery and lamps) is limited to the supply of power for illumination, including back-up power for exit lighting. The Code does not appear to consider unit equipment a “system.” Section 700.12 states that “...The supply system for emergency purposes...shall be one or more of the types of systems described in 700.12(A) through (E).” Unit equipment is addressed in 700.12(F). Frequently, unit equipment supplies the entire emergency load. The AHJ will determine where this requirement is applicable.

EM

EM

Emergency lighting symbols

Electrical service equipment room

Summary Where an emergency system is installed, emergency illumination must be provided in the area of the disconnecting means required in 225.31 (a main disconnect in a separate building supplied by a feeder or branch circuit) and 230.70 (a service disconnect). The rule is applicable where the service disconnect or main disconnecting means is installed indoors. Application Question

Does the requirement apply to each of multiple electrical rooms in a large facility? Answer No. The rule only applies to the electrical room where the service (or main) disconnect for the normal supply is located.


101

ARTICLE 728 – Fire-Resistive Cable Systems

2014 NEC

Fire-Resistive Cable Systems Significance This new article provides details for the installation of fire-resistive cable systems. Proper installation of these systems is necessary to ensure continued operation of critical circuits during a fire. Analysis Article 728 covers the installation of fire-resistive conductors and cables (e.g., circuit integrity [CI] cable) and other components of fire-resistive cable systems. The purpose of the new rules is

to enhance the survivability of critical circuits to ensure continued operation for a specified period of time under specified fire conditions. Fire-resistive cable systems are part of Electrical Circuit Protective Systems, UL Category FHIT. The components of fire-resistive cable systems are tested and listed as a system and shall not be interchangeable between systems. Installation of these systems is very detailed and must follow the instructions provided in the listing as well as applicable NEC provisions. Installation requirements in this article and in the listing apply to systems installed outside the fire-rated rooms that they serve, such as electrical or fire pump rooms. Fire-resistive cable systems shall be secured to the structure in accordance with the listing and manufacturer’s installation instructions. The fire rating of the wall or ceiling on which the system is installed shall be equal to or greater than the fire rating of the system. Where a fire-resistive system is listed for installation in a raceway, the raceway, couplings, and connectors must be listed as part of the fire-resistive system. Pulling lubricants used in the installation of fire-resistive cables within raceways shall be listed for the system. Unless specifically stated in the design, all components of Electrical Circuit Protective Systems (UL Category FHIT) such as raceways, couplings, connectors, boxes, conduit bodies, etc. that come in contact with fire- resistive cables shall have an interior coating free of zinc. Support for fire-resistive cable systems is important to the survivability of the systems and is more robust than NEC support requirements for other wiring methods. Fire-resistive systems shall be supported in accordance with the listing and manufacturer’s installation instructions. If an equipment grounding conductor is required within a raceway system, it shall consist of the same fire-rated cable described in the system, unless alternative equipment grounding conductors are listed for use with the system. An alternative equipment grounding conductor shall be marked with the system number. System cables and conductors shall be marked with the suffix “–FRR” (Fire-Resistive Rating), along with the circuit integrity duration in hours and the system identifier. Summary New Article 728 – Fire-Resistive Cable Systems contains detailed requirements for installation of

fire-resistive cable systems. Its purpose is to enhance the survivability of critical circuits to ensure continued operation for a specified period of time under fire conditions. The components of fireresistive cable systems are tested and listed as a system and shall not be interchangeable between systems.


102

ARTICLE 728 – Fire-Resistive Cable Systems

2014 NEC

The systems must be installed in accordance with this Code and all instructions included in the listing. Robust securing and supporting of fire-resistive cable systems shall be in accordance with the listing and manufacturer’s instructions. Fire-resistive cable systems are part of Electrical Circuit Protective Systems, UL Category FHIT.

Support fire-resistive cable systems according to the listing and manufacturer’s installation instructions.

X′

ma

x

.

Approved clamps Fire-resistive cable in rigid steel conduit or other raceway listed as a component of the system

Concrete or masonry surface

Note: Systems may be listed for mounting on other than concrete or masonry.

1½″ steel channel secured to firerated structure with approved fasteners, or other securing method listed for the system

Electrical Circuit Integrity System (constructed with fire-resistive cable) System No. XXXX

Fire Rating – X Hr.

Application Question T F Rigid steel conduit is the only acceptable raceway for use as a component of a fireresistive cable system. Answer False. Generally, raceways of a listed system are rigid steel. However, other conduit or raceways might be listed as part of the system. Remember that all components of a system must be listed as part of that system and be installed according to the listing and manufacturer’s instructions. The steel channel and rigid steel conduit in the drawing above must be listed as components of the electrical circuit integrity system.


103

ARTICLE 750 – Energy Management Systems

2014 NEC

Energy Management Systems Significance With widespread use of energy management systems (EMS) for monitoring and controlling loads, it is important that the NEC restrict automatic control of loads where shutdown could cause personal injury, or property damage or loss. Analysis Smart Grid and other load monitoring and control technologies are increasingly being used to improve energy efficiency, reliability, and economics of electricity use. The purpose of new

Article 750 – Energy Management Systems is to restrict the use of automatic control of loads where injury could result, e.g., stopping a fan that is exhausting air from a hazardous (classified) area, or shutting down a moving walkway while in use. Load shedding is already permitted in existing Code language for ensuring reliable operation of fire pumps and emergency systems, Articles 695 and 700 respectively. New Section 750.20 prohibits an energy management system from overriding any control necessary for ensuring continuity of alternate power sources for fire pumps, health care facilities, emergency systems, legally required standby systems, and critical operations power systems (COPS). Section 750.30 further restricts operations of energy management systems as follows: (A) Load Shedding Controls. An energy management system shall not override load shedding controls that ensure the minimum electrical capacity for: (1) Fire pumps (2) Emergency Systems

(3) Legally required standby systems (4) Critical operations power systems (COPS) (B) Disconnection of Power. An energy management system shall not be permitted to cause disconnection of power to: (1) Elevators, escalators, moving walks, or stairway lift chairs (2) Positive mechanical ventilation for hazardous (classified) locations (3) Ventilation used to exhaust hazardous gas or reclassify an area (4) Circuits supplying emergency lighting (5) Essential electrical systems in health care facilities (C) Capacity of Branch Circuit, Feeder, or Service. An energy management system shall not cause a branch circuit, feeder, or service to be overloaded at any time.

When an energy management system is used to control power through a remote means, a directory identifying the controlled device(s) or circuit(s) shall be posted on the enclosure of the controller, disconnect, or branch circuit overcurrent device.


104

ARTICLE 750 – Energy Management Systems

2014 NEC

Summary Article 750 – Energy Management Systems contains rules that prohibit energy management systems from overriding load shedding controls that are in place to ensure minimum capacity requirements for fire pumps, emergency systems, and other required standby and critical power systems. An EMS shall not be permitted to disconnect power to circuits supplying emergency lighting, essential electrical systems in health care facilities, ventilation exhausting hazardous gas, or power to elevators, moving walks and similar equipment. An EMS may not cause any service, feeder, or branch circuit to become overloaded. Also, an EMS is prohibited from overriding any control necessary for ensuring continuity of alternate power sources for critical loads.

Application Question Is an energy management system permitted to monitor and control indoor temperature, ventilation fan speeds, and lighting levels and modes for general lighting at multiple campuses of a university system? Answer Yes. This is an application of SCADA (supervisory control and data acquisition), computer monitoring and controlling of heating, ventilation, and air conditioning (HVAC) systems, and

energy consumption. None of these functions is restricted by Article 750, assuming no hazards are introduced.


105

770.110

Optical Fiber Cables and Raceways

2014 NEC

Part V. Installation Methods Within Buildings – Raceways and Cable Routing Assemblies for Optical Fiber Cables Significance Additional rules for the installation of Cable Routing Assemblies have been included in the 2014 NEC. Analysis Cable Routing Assemblies are widely used for cable support/management in data centers. They are commonly used for optical fiber, data, and communications cables. The definition for cable routing assembly has been relocated from 770.2 to Article 100, since the term is used in more than one Code article. Use of theses assemblies has been expanded to include Class 2 and Class 3 circuit cables in Article 725, and power-limited fire alarm (PLFA) cables in Article 760. Its definition has been revised to reflect the extended application. A Cable Routing Assembly is a single channel or connected multiple channels, as well as associated fittings, forming a structural system used to support and route communications cables, optical fiber cables, data cables associated with information technology and communications equipment, Class 2 and Class 3 cables, and power-limited fire alarm cables.

Subsections 770.110(C)(1) and (2) contain requirements for horizontal and vertical support for cable routing assemblies. Generally, horizontal support is required at intervals not exceeding 3 ft; vertical support is required at intervals not exceeding 4 ft. See also .110(C) in 800, 820, and 830. Listing requirements have been included in the new Code for plenum cable routing assemblies in 800.182(A). New Table 800.154(c) matches the application of listed cable routing assemblies in buildings with the cable routing assembly type: plenum, riser, and general-purpose. Courtesy of Leviton Manufacturing Co., Inc.

Fiber Raceway System is UL 2024A listed for riser-rated telecommunications applications.

Summary Cable routing assemblies are permitted to be used to support and route communications cables, optical fiber cables, data cables associated with information technology and communications equipment, Class 2 and Class 3 cables, and power-limited fire alarm cables. New Table 800.154(c) matches the application of cable routing assemblies in buildings with the cable routing assembly type: plenum, riser, and general-purpose. Installations must comply with horizontal and vertical support requirements. Application Question

Does the NEC consider a cable routing assembly a raceway? Answer A raceway is an enclosed channel of metallic or nonmetallic material designed for holding wires, cables, or busbars. Cable routing assemblies that are enclosed could be considered raceways.


106

Article 800

Communications Circuits

2014 NEC

Article 800 – Communications Circuits Significance There are several changes to Article 800 that are important for those who work with low-energy circuits. Other changes within this article have been addressed in the analysis of other sections in this book. Communications raceways as innerduct Courtesy of Innerduct.com

800.12 Innerduct. Definition: “A nonmetallic raceway placed within a larger raceway.” Listed plenum communications raceway, riser communications raceway, and general-purpose communications raceway are permitted to be installed as innerduct in any type of listed raceway permitted in Chapter 3. The communications raceway shall be selected in accordance with the provisions of Table 800.154(b). Communications Raceways Signaling raceways and optical fiber raceways are no longer mentioned in the NEC, as these raceways are now communications raceways. Applications of communications raceways in buildings is located in Table 800.154(b). The table lists the applications that are permitted for each of the raceway types: plenum communications raceway, riser communications raceway, and general-purpose communications raceway. This change is reflected in the revised definition of communications raceway, relocated to Article 100. Signaling Raceway, Art. 725 Optical Fiber Raceway, Art. 770

Communications Raceway, Table 800.154(b)

2014 NEC

Communications Raceway, Art. 800

800.179(G) Circuit Integrity (CI) Cable or Electrical Circuit Protective Systems Cables that are used for survivability of critical circuits under fire conductions can be tested and listed as “CI” cable or they can be tested as part of an electrical circuit protective system (UL Category FHIT) as outlined in new Article 728. Circuit integrity (CI) cables shall only be installed in free air. Fire-resistive cables that are a part of an electrical circuit protective system shall be identified with the protective system number on the product and installed in accordance with the listing of the protective system. A similar change has been made in Article 725.179(F) and Article 760.179(G). Type FPLR-CI (Power-limited fire alarm riser cable – Circuit Integrity) For use without conduit in fire alarm systems Courtesy of Draka Cableteq USA


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Informative Annex J

ADA Standards for Accessible Design

2014 NEC

Informative Annex J – ADA Stand ards for Accessible Design Significance Selected provisions of the 2010 ADA Standards for Accessible Design are included in new Informative Annex J to assist Code users in considering electrical design constraints in buildings required to comply with the ADA Standard. Analysis The 2010 ADA Standards set minimum requirements for newly designed and constructed or altered State and local government facilities, public accommodations, and commercial facilities to

be readily accessible to and usable by individuals with disabilities. Annex J includes provisions from Section 307, Protruding Objects (protruding into the circulation path), and Section 308, Reach Ranges. For placement of switches, receptacles, and other operable parts, consult Section 309 of the Standard, Operable Parts. According to Section 309.3 – Height, operable parts shall be placed within one or more of the reach ranges specified in 308. Where forward reach is unobstructed, high forward reach shall be 48 in. maximum and low forward reach shall be 15 in. minimum above finish floor or ground. Where the high forward reach is obstructed by an intrusion of more than 20 in., such as over a bathroom sink, the high forward reach shall be 44 in. max. Where a clear floor space allows side approach to an element, and the reach is unobstructed, the high reach shall be 48 in. maximum and the low reach shall be 15 in. minimum. If the side reach is obstructed, the high reach maximum is either 46 in. or 48 in., depending on the depth of the obstruction. Remember that an Informational Annex is not a mandatory part of the NEC, but is included for informational purposes only. The ADA Standard in its entirety should always be consulted. It can be viewed at: http://www.ada.gov/2010ADAstandards_index.htm Summary The 2014 NEC includes Informational Annex J, ADA Standards for Accessible Design, to assist Code users in considering electrical design constraints for electrical and other building systems in buildings required to comply with ADA, e.g., requirements for switch and receptacle heights. Application Question To be ADA compliant a wall receptacle should be located not lower than __________ inches above finish floor or ground to the lowest part of a duplex receptacle. A. 12 B. 15

C. 18 D. 24 Answer: B. The 15 in. lower limit for the receptacle height applies to both unobstructed front approach and unobstructed side approach.


108

Other Important Changes 210.12(A)

2014 NEC

110.24(A) Available Fault Current – Field Marking A new Informational Note has been added to remind Code users that the required available fault current marking is related to compliance with Sections 110.9 and 110.10 to ensure suitable interrupting ratings and fault clearing ability of equipment. This fault current value is not intended to be used for arc lash hazard analysis as required in NFPA 70E-2012, Standard for Electrical Safety in the Workplace. 210.4(D) Multiwire Branch Circuits – Grouping The general rule requires that the ungrounded and grounded circuit conductors of each multiwire

branch circuit be grouped using cable ties or similar means in at least one location within the panelboard or other point of srcin of the circuit. The requirement does not apply where the conductors enter the panel through a cable or raceway unique to the circuit so that the conductor association is obvious. The exception to the grouping requirement has been expanded to exempt the requirement where conductors are identified at their terminations with numbered wire markers corresponding to the appropriate circuit number. 210.8(A)(7) Ground-Fault Circuit-Interrupter Protection for Personnel – Dwelling Units – Sinks A receptacle located within 6 ft of the outside edge of a kitchen sink (or any other sink) in a dwelling unit must have GFCI protection. A Code clarification calls attention to the fact that this includes a receptacle within a cabinet, perhaps for the supply of a waste disposer. This undercabinet receptacle also requires AFCI protection of its supply circuit because of a 2014 change in 210.12(A). 314.15 Boxes and Conduit Bodies – Damp or Wet Locations This change will help to prevent degradation over time of metal boxes in outdoor locations from moisture condensation. Approved drainage openings not larger than ¼ in. shall be permitted to be installed in the field in boxes or conduit bodies listed for use in damp or wet locations. Larger opening are permitted for field installation of listed drain fittings in accordance with the manufacturer’s instructions. The provision also applies to nonmetallic boxes and conduit bodies. A vague version of this new permission is in Section 110.12(A) of the existing Code, where unused openings in equipment enclosures are permitted where “intended for the operation of the equipment.” 314.25 Covers and Canopies A new sentence has been added to this section. Screws used for the purpose of attaching covers, faceplates, lampholders, luminaire canopies, or other equipment to boxes shall be machine screws matching the thread gauge or size that is integral to the box or be in accordance with the

manufacturer’s instructions. Use of screws not designed for the purpose, such as drywall screws, is prohibited.


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2014 NEC

330.30(B) Metal-Clad Cable: Type MC– Securing and Supporting – Securing A provision has been added to this section to address securing of vertical installations of listed MC cable of sizes 250 kcmil and larger. In vertical installations, listed MC cables with ungrounded conductors of 250 kcmil and larger shall be permitted to be secured at intervals not exceeding 10 ft. This provision recognizes the internal integral conductor support for large-size MC cables that are used for vertical runs in high rise construction. The general rule requires the securing of MC cables at intervals not exceeding 6 ft. 376.56(B)(1) and (B)(5) Metal Wireways – Power Distribution Blocks – Installation and Conductors This change pertains to listed power distribution blocks installed in metal wireways on the line side of service equipment. Distribution blocks installed ahead of service equipment shall be listed for the purpose. A new subsection (5) requires conductors in wireways to be arranged so that the terminals of power distribution blocks remain unobstructed after installation. 400.7(A)(11) Flexible Cords and Cables – Uses Permitted This new permission for flexible cord and cable usage in subsection (11) is primarily intended to address listed equipment assemblies for wall installation of flat-screen televisions. A flush wall inlet is installed on a wall at typical receptacle height. A chapter 3 wiring method in the wall connects this inlet to a single receptacle outlet above and higher up on the wall located behind the television. The new permission allows a flexible cord listed as part of the assembly to connect the inlet to an adjacent existing wall receptacle (used like a patch cord).

406.4(D) Replacements Where receptacles are replaced in locations that require GFCI protection or AFCI protection for the branch circuit according to current Code, GFCI or AFCI receptacles installed must be readily accessible. 406.5(E) and (F) Receptacle Mounting – Receptacles in Countertops and Similar Work Surfaces – Receptacles in Seating Areas and Other Similar Surfaces Receptacles in countertop surfaces are not permitted to be installed in a face-up position unless listed for the propose. This rule now applies to all occupancies, not just to dwelling units. New subsection (F) prohibits mounting of receptacles in a face-up position in seating areas and other similar surfaces unless the receptacle is any of the following:

(1) Part of an assembly listed as a furniture power distribution unit, if cord-and-plug connected (2) Part of an assembly listed either as household furnishings or as commercial furnishings (3) Listed either as a receptacle assembly for countertop applications or as a GFCI receptacle assembly for countertop applications (4) Installed in a listed floor box This change is intended to prohibit the practice of installing receptacles face-up in benches and seating areas in public locations such as airports for laptop or electronic device charging. The


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2014 NEC

change should prevent equipment damage from spillage and prevent physical damage to the receptacle that could expose persons to live parts. 408.3(F) Switchboard, Switchgear, or Panelboard Identification Three new subsections have been added that require field marking for: high-impedance grounded neutral AC systems, ungrounded DC systems, and resistively grounded DC systems. Marking for each system shall include the word “CAUTION” followed by the type of system and the voltage between conductors and, where applicable, the voltage to ground. 422.5 Appliances – Ground-Fault Circuit-Interrupter (GFCI) Protection This is a new section that requires all devices that provide GFCI protection (5 mA) required in this article, 422 – Appliances, to be readily accessible. Article 422 requires GFCI protection for tire inflation and automotive vacuum machines, high-pressure spray washers (integral, factory installed), vending machines, and electric drinking fountains. Dishwashers installed in dwelling unit locations are required by 210.8(D) in the 2014 NEC to be provided with GFCI protection. A receptacle in a dwelling unit serving a waste disposer shall be GFCI protected if installed within 6 ft of the outside edge of a sink, even where located below the sink in a cabinet. 514.3(C) Motor Fuel Dispensing Stations in Boatyards and Marinas Rules for wiring motor fuel dispensing stations at marinas and boatyards, formerly located in Section 555.21, is relocated to new Section 514.3(C). There are no changes to the rules. Class I, Division 1 or 2 locations are specified for closed construction (floating piers) and open construction (fixed piers). Exceptions apply to the classification for closed construction where

documentation is provided in accordance with 500.4(A). Both exceptions require “documented air space.” 

Code Refresher 500.4(A) Documentation – “All areas designated as hazardous (classified) locations shall be properly documented. This documentation shall be available to those authorized to design, install, inspect, maintain, or operate electrical equipment at the location.” The best documentation is a plan/drawing prepared by a qualified design professional showing the details, dimensions, boundaries, etc. of the classified areas.

Article 516 – Spray Application, Dipping, Coating, and Printing Processes This article has undergone a substantial rewrite in order to correlate the article with the 2011 editions of NFPA 33, Standard for Spray Application Using Flammable and Combustible Materials and NFPA 34, Standard for Dipping, Coating, and Printing Processes Using Flammable or Combustible Liquids. Several new figures are included within the article to aid in

the understanding of the rules. All of the existing definitions have been revised and new definitions have been added for flash-off area, limited finishing workstation, resin application area, and unenclosed spray area. There is revised language for enclosed spray booths or rooms to clarify the area classification of any


111


2014 NEC

recirculation path in a recirculating spray booth, and to clarify that the interior of a fresh air supply plenum in a non-recirculating spray booth is an unclassified area. Rules concerning illumination of classified spray areas have been updated with detailed requirements extracted from NFPA 33. 690.47(D) Additional Auxiliary Electrodes for Array Grounding New Section 690.47(D) was inadvertently removed from the 2011 NEC. It has been included in the 2014 NEC as it appeared in the 2008 Code. The only changes from the 2008 language is the inclusion of the term auxiliary in the title of the subsection and the requirement for the grounding

electrode to be installed in accordance with 250.52 and 250.54. A grounding electrode shall be installed at the location of all ground- and pole-mounted PV arrays and as close as practicable to the location of roof-mounted arrays. The electrode(s) shall be connected directly to the array frame(s) or structure. The structure of a pole- or ground-mounted array is permitted to serve as the required auxiliary electrode if it qualifies as a grounding electrode in accordance with 250.52. The purpose of the auxiliary electrode(s) is to provide a degree of protection from surges caused by indirect lightning strikes. NFPA 780, Standard for the Installation of Lightning Protection Systems, should be consulted where lightning protection is required. 700.19 Emergency System Circuits for Lighting and Power – Multiwire Branch Circuits This is a new section in the 2014 Code that is intended to enhance the reliability of critical circuits. In the new Code, a branch circuit that serves emergency lighting and power loads shall not be part of a multiwire branch circuit.

702.7(C) Optional Standby Systems – Signs – Power Inlet This new subsection requires a warning sign where a power inlet is available for temporary connection to a portable generator. The sign shall be placed near the inlet and shall indicate the configuration of the transfer switch of the premises wiring. The sign shall display one of the following:

WARNING: FOR CONNECTION OF A SEPARATELY DERIVED (BONDED NEUTRAL) SYETEM ONLY WARNING: FOR CONNECTION OF A NONSEPARATELY DERIVED (FLOATING NEUTRAL) SYETEM ONLY


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2014 NEC

Appendix A Common 2011 National Electrical Code® Violations Noted by Maine Electricians’ Examining Board staff in 2011-2013

And Bonding of CSST

1. A metal raceway emerging from grade at a pole and enclosing service conductors is not bonded to the grounded system conductor. [250.80]

Often an underground service supplied from a pole requires protection from physical damage for service conductors up to 8′ above grade at the pole. Where rigid metal conduit or intermediate metal conduit is used for protection, the raceway must be connected (bonded) to the service neutral. The underground service conductors from the pole to the building or structure are usually direct buried or enclosed in PVC or other nonmetallic raceway. The isolated metal conduit on the pole is bonded to the utility’s “down ground,” the conductor installed to ground the neutral tap of the transformer to a ground rod at the base of the pole. The common violation that staff has encountered occurs in instances where the pole is a point pole (no transformer on the pole). In the event that insulation failure of an ungrounded conductor energizes the conduit, connection of the steel conduit to a ground rod alone will not clear the fault. Generally, the best option is to coordinate with the utility so that a conductor connected to the utility neutral is run down the pole for connection to the service conduit. If steel conduit is installed all the way up the pole, the connection to the grounded system conductor could be made at the top of the pole by utility workers. Electrical metallic tubing (EMT) could be used on the pole above 8′ above grade if acceptable to the utility. The relevant NEC® sections are: 250.80; 250.102 [except 250.102(D) and particularly 250.102(E)(2), Exception]; 250.8; Table 250.66; and 300.5(D)(1) and (D)(4). Utility company standards also apply. See Rules 360C and 314B of the National Electrical Safety Code® (NESC®), C2-2007. 2. A commercial service supplied with 2 AWG aluminum service-entrance conductors is protected at 100 a mperes. [Table 310.15(B)(16)]

For conductor types rated at 75°C, Table 310.15(B)(16) lists the ampacity of AWG 2 aluminum as 90 amperes. According to 240.6(A), a 90-A overcurrent device is a standard size. It is rare that the ampacity in the 90°C column can be used, since all circuit terminations, conductors, and equipment would have to be rated for 90°C [see 110.14(C)]. For a residential service, Section 310.15(B)(7) permits 2 AWG aluminum to be protected at 100 amps. 3. The grounding electrode conductor (GEC) is not secured to the meter socket enclosure. [110.3(B)]

Section 312.5(C) requires that cables be secured to cabinets, cutout boxes, and meter socket enclosures. True, the GEC is technically a conductor rather than a cable. The State Electrical Inspectors often encounter installations where the GEC is run through a small factory supplied knock-out (KO) in the bottom of the meter socket. These KOs (often ¼″) are either single KOs or are the center of a concentric set of KOs. These small KOs are Common 2011 National Electrical Code® Violations Noted by Maine Electricians’ Examining Board staff in 2011-2013

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Appendix A not intended for passage of grounding electrode conductors. A connector is required to help prevent stress on the cable/conductor from being transmitted to the GEC termination in the socket. It also prevents the GEC from being pushed into the enclosure, possibly contacting live parts. Additionally, the GEC must be securely fastened to the surface on which it is carried [250.64(B)]. 4. A concrete-encased electrode is not bonded to the grounding electrode system. [250.50]

Section 250.50 states that all grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. A concrete-encased electrode as specified in 250.52(A)(3)(1) is almost always available for new construction. However, arrangements must be made to make the grounding electrode (reinforcing steel) available after concrete is poured or to connect a conductor to the reinforcing steel prior to concrete pouring. A copper grounding electrode conductor connected to reinforcing bar and exiting the concrete structure in the area where the electrical service is to be located is ideal. A box out near the top of a concrete wall allowing access to re-bar after the pour also works well. A concrete-encased electrode, particular in a footing, is usually a very effective grounding electrode. The electrode remains below the frost line, and, where there is a full basement or living space below grade, the electrode in the footing is relatively deep for its entire length (as opposed to a driven rod). If concrete walls are not covered with insulating foam or other material preventing direct contact with the earth, the concrete surface in direct contact with the earth is substantial and a very effective grounding electrode. If a concrete footing does not include reinforcing bars, placement of 20′ minimum of 4 AWG copper minimum as described in 250.52(A)(3)(2) is worth the effort in terms of service grounding. 5. Conductor ampacity is not adjusted (or correctly adjusted), where there are more than 30 current-carrying conductors at any cross section in a metal wireway. [376.22(B)]

Metal wireways installed above panels are a convenient way to transition from horizontally run branch circuits to vertical raceways between the wireways and panels. Depending on where the horizontally run branch circuit wiring leaves the wireway relative to where the circuit conductors enter the wireway, the number of current-carrying conductors at a cross section of the wireway could exceed 30 conductors. The 30conductor threshold does not relate to a total of 30 current-carrying conductors in the wireway, but to 30 current-carrying conductors at any cross section. This is clarified in Section 376.22(B) of the 2014 NEC. Where the number of current-carrying conductors at any cross section exceeds 30, the adjustment factors in 310.15(B)(3)(a) must be applied. If 31-40 conductors are installed at any cross section, all conductors have to be adjusted to 40% of their initial ampacity, 35% for 41 or more conductors. These are deep reductions in ampacity that apply to all current-carrying conductors, not just to the number of current-carrying conductors over 30.

Common 2011 National Electrical Code® Violations Noted by Maine Electricians’ Examining Board staff in 2011-2013

Page 2

Appendix A 6. Type TC-ER cable and Type CL3R cable is used for mini-split heat pump wiring between the outdoor and indoor units. [336.12(2)] and [Chapter 9, Table 11(A)]

Type TC-ER cable is not permitted to be installed outside of a raceway or cable tray, except for extended runs in supervised industrial settings as permitted in 336.10(7), or when installed outdoors supported by a messenger as permitted in 336.10(4). TC-ER cable has been used extensively in Maine to interconnect the outdoor and indoor units of mini-split heat pump systems. Usually the outdoor unit is secured to an outside wall with the indoor unit mounted back-to-back from the outdoor unit, except higher. For some installations, the indoor unit is located on an interior wall, and the TC-ER has been run as interior wiring similar to NM wiring. Also, the Maine State Electrical Inspectors have cited Type CL3R for this same use. Most of the indoor mini-split heat pump units that have been inspected in Maine are rated 240-V, but occasionally 120-V units are encountered. Even though CL3R is rated for 300 volts and the indoor heat pump units have a low current draw, permitted power sources for this and similar cables is limited to 150 volts and low power as prescribed in Table 11(B) of Chapter 9. Since a portion of the cabling is in a wet location, the only permitted application is a Class 3 non-inherently limited power source, applicable for 120-V units only. In addition to using the correct cable, be sure that the proper overcurrent protection is provided for the interconnecting cable. One more thing: Section 210.63 applies—a convenience receptacle for servicing HVAC equipment, located within 25′ of the equipment. 7. Recessed luminaires are not fastened to the suspended ceiling grid. [410.36(B)]

Recessed luminaires (troffers) must be securely fastened to the suspended ceiling grid by mechanical means such as bolts, screws, rivets, or listed clips identified for use with the type of grid and luminaire. Many troffers are constructed with integral clips for this purpose. Some installers are under the impression that this requirement is not applicable where the luminaires are supported by separate wires in addition to the ceiling support wires. Section 300.11(A) addresses independent support wires for the support of wiring, but not for the support of luminaires. 8. Arc-fault circuit-interrupter (AFCI) protection of branch circuits is not installed as required. [210.12(A)]

The Electricians’ Examining Board voted to amend Section 210.12(A) in the 2008 NEC and in previous editions. It was thought that an amended AFCI requirement was forthcoming with the adoption of the 2011 NEC. However, the Board ultimately voted to adopt 210.12 unamended in the 2011 NEC. This is likely part of the reason that the State Electrical Inspectors found so many violations of the AFCI requirements. All 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed combination-type AFCI device. This rule applies also to two-family and multifamily dwellings. This requirement is expanded in the 2014 Code.


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Appendix A 9. No intersystem bonding has been installed. [250.94]

For new buildings or structures, specific rules apply for providing a means for interconnecting bonding conductors of other systems such as TV and communications services with the electric utility service grounding electrode system. There are several options and a variety of products available to meet the provisions of this section. If the service equipment is located inside of the building, the intersystem bonding provision can be located either inside or outside. Intersystem bonding provisions shall also be provided at the required disconnecting means for a separate building. 10. The ends of a ferrous metal raceway enclosing a grounding electrode conductor are not bonded to the GEC, or the raceway is not otherwise made continuous between the metal cabinet and the electrode. [250.64(E)]

Ferrous raceways enclosing GECs must be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode, or be made continuous by bonding each end of the raceway to the GEC. The bonding jumper for the raceway shall be the same size as, or larger than, the enclosed GEC. Where steel raceway enclosing a GEC is electrically continuous, the majority of current actually flows through the raceway. Some wireman only bond one end of the ferrous raceway. The purpose for bonding is not accomplished by bonding only one end. Bonding of only one end will set up an inductive choke effect that will impede the flow of current. Beyond the Code: A GEC should not be installed in a ferrous raceway if it can be avoided. When a GEC is installed in a continuous ferrous raceway, the impedance of the grounding electrode conductor path is increased significantly over that of using the copper conductor alone. The increase in impedance when a steel conduit is used is about

40% forconductor a 6 AWGenclosed copper conductor enclosedSince in a ¾″ conduit,conduit to aboutis500% for a 3/0 it copper in a 1¼″ conduit. aluminum nonmagnetic, will not adversely affect the impedance of the GEC path. An aluminum conduit enclosing a GEC is not required to be electrically continuous. Schedule 80 PVC conduit is a good choice when physical protection is needed for a grounding electrode conductor. 11. Circuit breakers installed in a panel are not specified by the manufacturer as suitable for use in the panel, an d the breakers are not UL Classified breakers suitable for use in the panel. [110.3(B)]

In addition to a panel manufacturer’s own brand of Listed circuit breakers, Specified breakers (manufactured by others) are listed by the panel manufacturer as suitable for use in their panels. Additionally, Classified breakers are manufactured that are suitable for use in several panel brands, in accordance with the instructions for the Classified breaker. Classified breakers are limited to applications where the available fault current is not more than 10,000 amperes, since they are not tested in a specific series rated system. The fact that a breaker “fits” (is interchangeable) in another manufacturer’s panel does not necessarily constitute a Code-compliant installation.


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Appendix A Bonding of corrugated stainless steel tubing (CSST)

Section 7.13.2 of NFPA 54-2012, National Fuel Gas Code, requires bonding of corrugated stainless steel tubing in an effort to protect the tubing against the potentially harmful effects of an indirect lighting strike. All manufacturers’ instructions for this product require bonding using 6 AWG copper connecting to the electrical service grounding electrode system. The boding jumper shall connect to a metallic pipe or fitting between the point of delivery and the first downstream CSST fitting. The bonding clamp may be installed on a steel pipe component of the system (black pipe) or on a CSST fitting. Newer black-jacketed CSST may not require bonding. This requirement is beyond the NEC rule in 250.104(B) that permits the equipment grounding conductor of the branch circuit supplying a gas appliance to bond the gas piping. Even though 110.3(B) requires electrical equipment to be installed in accordance with all manufacturer’s instructions, bonding of gas piping for lightning protection is beyond the purview of the NEC. However, licensed electricians are the most qualified trade technicians to perform this work, especially if the bonding connection is made within the service equipment enclosure. Another good reason for involvement of an electrician is the fact that this piping is not permitted to be used as a grounding electrode [250.52(B)(1)]. An isolating fitting in the piping system should be used where necessary to prevent this.


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Maine Amendments to the 2011 National Electrical Code

02

DEPARTMENT OF PROFESSIONAL AND FINANCIAL REGULATION

318

ELECTRICIANS’ EXAMINING BOARD

Chapter 120:

ELECTRICAL INSTALLATION STANDARDS

SUMMARY: This chapter establishes the effective dates of the currentedition of the National Electrical Code to which all installations must conform.

1.

All installations of electrical equipment commencing on or after July 1, 2011 must comply withthe 2011 edition of the National Electrical Code, National Fire Protection standard #70, as well as with all applicable statutes or rules of theState and all applicable ordinances, orders, rules and regulations of local municipalities.

2.

The Board hereby adopts and incorporates into this chapter by reference The National Electrical Code, National Fire Protection Association standard #70, (2011 edition) with the following exceptions: A.

The Board adopts Article 200.6(D) with the following amendment: 200.6

Means of Identifying Grounded Conductors (D)

Grounded Conductors of Different Systems.Where grounded conductors of different systems are installed in the same raceway, cable, box, auxiliary gutter, or other type of enclosure, each grounded conductor shall be identified by system. Identification that distinguishes each system grounded conductor shall be permitted byone of the following means:

(1) One system grounded conductor shall have an outer covering conforming to 200.6(A) or (B). (2) The grounded conductor(s) of other systems shall have a different outer covering conforming to 200.6(A) or 200.6(B) or by an outer covering of white or gray with a readily distinguishable colored strip other than green running along the insulation. (3) Other and different means of identification as allowed by 200.6(A) or (B) that will distinguish each system grounded conductor. The means of identification shall be documented in a manner that is readily available or shall be permanently posted where the conductors of different systems srcinate.

1


Explanation: The method used for conductor identification shall be permanently posted where the conductors of different systems srcinate. Documentation in a manner that is readily available shall not be permitted as an identification means.

B.

The Board adopts Article 210.5(C)(3) with the following amendment: 210.5

Identification for Branch Circuits (C)

Identification of Ungrounded Conductors.Ungrounded conductors shall be identified in accordance with 210.5(C)(1), (2) and (3). (3) Posting of Identification Means.The method utilized for conductors srcinating within each branch-circuit panelboard or similar br anch-circuit distribution equipment shall be documented in amanner that is readily available or shall be permanently posted ateach branch-circuit panelboard or similar branch-circuit distribution equipment.

Explanation: The method used for conductor identification shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. Documentation in a manner that is readily available shall not be permitted as an identification means.

C.

The Board adopts Article 215.12(C) with the following amendment: 215.12 Identification for Feeders (C)

Ungrounded Conductors.Where the premises wiring system has feeders supplied from more than onenominal voltage system, each ungrounde d conductor of a feeder shall be identified by phase orline and system at all termination, connection, and splice points. The means ofidentification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means. The method utilized forconductors srcinating 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.

Explanation: This amendment is identical to the amendment to 210.5(C)(3), except applied to feeders.

D.

The Board adopts Article 334.10(3) with the following amendment: 334.10 Uses Permitted

(3)

Other structures permitted to be of Types III, IV, and V construction except as prohibited in 334.12. Cables shall be concealed within walls, floors, or ceilings that provide a thermal

2


barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies. Explanation: Type NM, NMC, and NMS cables are permitted to be run concealed or exposed. For concealed cables, a thermal barrier that has at least a 15-minute finish rating shall not be required.

E.

The Board does not adopt Article 334.12(A)(2),Uses Not Permitted.

Explanation: This section is not adopted in Maine. Types NM, NMC, and NMS cables are in fact permitted to be installed exposed in dropped or suspended ceilings in dwelling units and in other occupancy types including commercial occupancies.

F.

The Board adopts Article 338.12(B) (1) and (2) with the following amendment: 338.12 Uses Not Permitted (B)

Underground Service-Entrance Cable.

(1)

For interior wiring of branch circuits and feeders srcinating and terminating within the same building.

(2)

For aboveground installations except where USE cable emerges from the ground and is terminated in an enclosure at an outdoor a location acceptable to the Authority Having Jurisdictionand the cable is protected in accordance with 300.5(D).

Explanation: Type USE (URD) cable is not permitted for interior wiring of branch circuits and feeders srcinating and terminating within the same building. However, Type USE cable is permitted for aboveground installations where USE cable emerges from the ground and is terminated in an enclosure at a location acceptable to the Authority Having Jurisdiction, either inside or outside, and the cable is protected in accordance with 300.5(D). This amendment will continue to allow the generally accepted practice of installing continuous runs of USE cable without splicing, terminating in the first enclosure either outside or inside of a building, when the cable is enclosed in a suitable raceway. This also applies to the indoor portion of an underground run of USE cable that srcinates at an indoor panelboard near an outside wall of a structure.

G.

The Board adopts Article 702.4(B)(2) with the following amendment: 702.4

Capacity and Rating (B)

System Capacity. (2)

Automatic Transfer Equipment.For other than single-family dwellings, where automatic transfer equipment is used, an optional standby system shall comply with (2)(a) or (2)(b).

3


Explanation: For optional standby systems that supply single-family dwellings, the standby source shall not be required to be capable of supplying the full load that is transferred by the automatic transfer equipment.

3.

Copies of the National Electrical Code, National Fire Protection Association standard #70 may be purchased from: National Fire Protection Association 1 Batterymarch Park, P.O. Box 9101 Quincy, MA 02269-9101 Telephone: 1-800-344-3555

4

Maine Electricians’ Examini ng Board Important Statute Changes §1101. Definit ion s 4-A. Supervision. Two apprentice electricians, one helper electrician or 2 helper electricians who are both currently enrolled in, or have completed, a program of study consisting of 576 hours of education as approved by the Electricians' Examining Board or from an accredited institution may work with and under the direct supervision of a master electrician, limited electrician or journeyman electrician. A master electrician who teaches an electrical course at a Maine career and technical education center, a Maine career and technical education

region, a Maine community college or an apprenticeship program registered by the Department of Labor may have a maximum of 12 helper or apprentice electricians under direct supervision while making electrical installations that are a part of the instructional program of the school or apprenticeship program, as long as the total value of each installation does not exceed $5,000. An electrical installation may not be commenced pursuant to this subsection without the prior approval of the director or president of the school or apprenticeship program at which the master electrician is an instructor. These installations are limited to those done in buildings or facilities owned or controlled by: A. School administrative units; and [2005, c. 347, Pt. B, §1 (AMD).] B. Nonprofit organizations. [2005, c. 347, Pt. B, §1 (AMD).] The Electricians' Examining Board and the municipal electrical inspector of the municipality in which the installation is to be made, if the municipality has an inspector, must be notified of all of installation projects entered into pursuantbytoa state this electrical subsectioninspector prior toor the commencement the project. There must be an inspection by the municipal electrical inspector of the municipality in which the installation has been made, if the municipality has an inspector, before any wiring on the project is concealed. [ 2011, c. 650, §1 (AMD) .] Comment: In order for a master, journeyman, or limited electrician to supervise two helpers, both helpers must be enrolled in a Board approved 576-hour program of study or have completed such training. All apprenticelicensees are enrolled in approved training. 8. Utility corporation. "Utility corporation" means a utility that is not a public utility, as defined in Title 35-A, section 102, or a person, firm or corporation subject to the jurisdiction of the Federal Communications Commission.

[ 2011, c. 290, §2 (RPR) .]

Appendix C

Maine Electricians’ Examini ng Board Important Statute Changes §1102. Exceptions The provisions of this chapter shall not apply to the following:

[1973, c. 363, ( RPR) . ]

1. Commissions. [ 1997, c. 119, §2 ( RP) . ]

1-A. Public utility. An entity subject to the jurisdiction of the Public Utilities Commission, the Federal Energy Regulatory Commission or the Federal Communications Commission, including all employees of such an entity, but only to the extent the entity or its employees are making electrical installations in furtherance of providing its authorized service or activities incidental to that authorized service. This exception does not apply to: A. Installations, other than installation of a meter, inside a customer's building; [2011, c. 290, §3 ( NEW) . ]

B. Installations of mobile home service equipment; and [ 2011, c. 290, §3 ( NEW) . ] C. Installations at any business office of a utility corporation that is not physically located adjacent to the utility's generation or transmission and distribution plant; [2011, c. 290, §3 ( NEW) . ] [ 2011, c. 290, §3 ( RPR) . ]

1-B. Aboveground electric lines. Electrical work in connection with the construction, installation, operation, repair or maintenance of any aboveground electric line capable of operating at one kilovolt or more. [ 2011, c. 290, §4 ( NEW) . ]

1-C. Contractor. An entity, including all employees of such an entity, to the extent the

entity has contracted with a public utility, as described in this section, to perform services for the public utility, but only to the extent the public utility would be exempt from this chapter if it were performing the services directly through its employees; or [ 2011, c. 290, §5 ( NEW) . ]

2. Utility corporations. [ 2011, c. 290, §6 ( RP) . ]

Comment: Aboveground electric lines in 1-B is intended to address non-utility-owned, highvoltage collection lines associated with wind electric generation farms. There may be an error in 1-A(C)in that electrical installations in business offices of a public utility are within the jurisdiction of the NEC regardless of their proximity to generation or distribution facilities. Also, the term “utility corporation” is used in 1-A(C) under the heading “Public utility” in 1-A.

Appendix C

Maine Electricians’ Examini ng Board Important Statute Changes §1102-B. Permi ts and i nsp ection s 3. Inspection required. An inspection is required before the electrical wiring is enclosed by the building construction. The electrician making the installation or alteration shall notify the state electrical inspector when the installation is ready for inspection. The inspector shall inspect the installation within a reasonable time so as not to cause undue delay in the progress of the construction contract or installation. The inspector shall determine whether the installation complies with all applicable statutes, ordinances and rules. If the inspector determines that the

installation does require not so proof comply, the procedures set forth power in section apply. Any utility corporation must of permit prior to connecting to the1104 installation. [ 2011, c. 286, Pt . F, §8 ( AMD) . ]

Comment: The inspector needs to be contacted for an inspection before the wiring in enclosed by wallboard or other construction

§1201-A. Exceptions to licensing requirements 12. Incidental work. Regular employees of an owner or a lessee of real property doing incidental electrical work on that property or incidental electrical work by a person whose occupation involves miscellaneous jobs of manual labor. For purposes of this subsection, "incidental electrical work'' means minor electrical work, limited to light fixtures and switches, that occurs by chance and that does not require electrical installation calculations. [ 2011, c. 691, Pt . A, §35 ( NEW) . ]

Comment: An application of this exception is that a custodian in a school is permitted to replace a luminaire ballast and/or a light switch. It does not permit an unlicensed person to replace all ballasts in an area as part of scheduled maintenance. The exception to licensing permits a so-called handy man to replace or move a luminaire or light switch while in the course of a remodel project or the like. Any person that performs electrical work under this exception must understand that the permission to work does not qualify a person for the work. Any wireman must be familiar with basic electricity and installation practices.

§1202. Issuance of l icens es 5. Electrical company. [ 2011, c. 420, Pt . M, §7 ( AFF) ; 2011, c. 420, Pt . M, §6 ( RP) . ]

5. Electrical company. The board shall issue a license to operate an electrical company to a person who files an application validated by a master or limited electrician licensee. Comment: The previous language has been deleted. The company license no longer exists. All permits must be applied for by a licensed master or limited electrician. The permit holder is responsible for compliance with all Board laws and rules. Appendix C

Maine Electricians’ Examining Board Import ant Rule C hanges 02

DEPARTMENT OF PROFESSIONAL AND FINANCIAL REGULATION

318

ELECTRICIANS' EXAMINING BOARD

Chapter 135: ELECTRICAL PERMITS

Summary: This chapter identifies the types of licensee who may apply for an electrical permit, requires that the licensee applying for a permit must personally sign the application, prohibits a licensee from

signing a permit application on behalf of or in the name of another licensee, requires that the permit fee be paid at time of application, and states that a person who applies for a permit is legally and professionally responsible for compliance with the electrical laws and rules relating to the installation for which the permit was requested.

1.

Application for Electrical Permit

Application for an electrical permit pursuant to 32 M.R.S.A. §1102-B may be made only by: 1.

An individual master electrician; or

2.

An individual limited electrician, for an installation within the scope of the licensee’s limited practice.

The application must be personally signed by the master electrician or limited electrician applying for the permit. A licensee may not sign an application on behalf of or in the name of another licensee, even if authorized to do so by the other licensee. 2.

Fees

An application for an electrical permit must be accompanied by the fees required by Chapter 10, Section 5(15) of the rules of the Department of Professional and Financial Regulation, Office of Licensing and Registration entitled “Establishment of License Fees.” 3.

Responsibility

A master electrician or limited electrician who applies for an electrical permit is legally and professionally responsible for compliance with all laws and rules enforceable by the board with respect to the installation for which the permit was requested.

STATUTORY AUTHORITY: 32 M.R.S.A. §1102-B(2) and (4), §1153, §1153-A EFFECTIVE DATE: July 19, 2011 – filing 2011-240 Appendix D


2014 NEC

Revisions for the 2014 NEC, With Cover, First Printing

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