Introduction to the National Electrical Code

AR A RTICLE

90

Introduction to the National Electrical Code

NATIONAL TIONAL ELECTRICAL CODE INTRODUCTION TO ARTICLE 90—INTRODUCTION TO THE NA Many NEC violations and misunderstandings wouldn’t occur i people doing the work simply understood Article 90. For example, many people see Code requirements as perormance standards. In act, the NEC requirements are bare minimums or saety. This is exactly the stance electrical inspectors, insurance companies, and courts take when making a decision regarding electrical design or installation. Article 90 opens by saying the NEC isn’t intended as a design specication or instruction manual. The National Electrical Code has one purpose only, and that’s the “practical saeguarding o persons and property rom hazards arising rom the use o electricity.” It goes on to indicate that the Code isn’t intended as a design specication or instruction manual. The necessity to careully study the NEC rules can’t be overemphasized, and the role o textbooks such as this one is to help in that undertaking. Understanding where to nd the rules in the Code that apply to the installation is invaluable. Rules in several dierent articles oten apply to even a simple installation. Article 90 then describes the scope and arrangement o the NEC . The balance o Article 90 provides the reader with inormation essential to understanding those items you do nd in the NEC . Typically, electrical work requires you to understand the rst our chapters o the Code which apply generally, plus have a working knowledge o the Chapter 9 tables. That knowledge begins with Article 90. Chapters 5, 6, and 7 make up a l arge portion o the NEC , but they apply to special occupancies, special equipment, or other special conditions. They build on, modiy, or amend the rules in the rst our chapters. Chapter 8 contains the requirements or communications systems, such as telephone systems, antenna wiring, CATV, and network-powered broadband systems. Communications systems aren’t subject to the general requirements o Chapters 1 through 4, or the special requirements o Chapters 5 through 7, unless there’s a specic reerence in Chapter 8 to a rule in Chapters 1 through 7.

90.1 Purpose of the NEC . (A) Practical Safeguarding. The purpose o the NEC is to ensure that electrical systems are installed in a manner that protects people and property by minimizing the risks associated with the use o electricity. (B) Adequacy. The Code contains requirements considered necessary or a sae electrical installation. I an electrical installation is installed in compliance with the NEC , it will be essentially ree rom electrical hazards. The Code is a saety standard, not a design guide. NEC requirements

aren’t intended to ensure the electrical installation

will be ecient, convenient, adequate or g ood service, or suitable or uture expansion. Specic items o concern, such as electrical energy management, maintenance, and power quality issues aren’t within the scope o the Code . Figure 90–1

Figure 90–1

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 888.NEC.CODE (632.2633)

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90.2


Note: Hazards in electrical systems oten occur because circuits are overloaded or not properly installed in accordance with the NEC . These oten occur i the initial wiring didn’t provide reasonable provisions or system changes or or t he increase in the use o electricity.

Author’s Comments: • Seethedefinitionof“Overload”inArticle100. • The NEC doesn’trequireelectricalsystemstobedesignedor installedtoaccommodatefutureloads.However,theelectri caldesigner,typicallyanelectricalengineer,isconcernedwith notonlyensuringelectricalsafety( Code compliance),butalso withensuringthesystemmeetsthecustomers’needs,both oftodayandinthenearfuture.Tosatisfycustomers’needs, electricalsystemsareoftendesignedandinstalledabovethe minimumrequirementscontainedintheNEC .Butjustremem ber,ifyou’retakingan exam, licensingexamsare basedon yourunderstandingoftheminimumCoderequirements.

Author’s Comments: • Seethedefinitionof“Overcurrent”inArticle100. • The NEC isusedinChile,Ecuador,Peru,andthePhilippines. It’salsotheelectricalcodeforColombia,CostaRica,Mexico, Panama,PuertoRico,andVenezuela.Becauseoftheseadop tions,the NEC isavailableinSpanishfromtheNationalFire ProtectionAssociation,617.770.3000,orwww.NFPA.Org.

90.2 Scope of the NEC . (A) What is Covered. The NEC contains requirements necessary or the proper installation o electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; as well as optical ber cables and raceways or the ollowing locations: Figure 90–3

(C) Intention. The Code is intended to be used by those skilled and knowledgeable in electrical theory, electrical systems, construction, and the installation and operation o electrical equipment. It isn’t a design specication standard or instruction manual or the untrained and unqualied. (D) Relation to International Standards. The requirements o the NEC

address the undamental saety principles contained in the

International Electrotechnical Commission (IEC) standards, including protection against electric shock, adverse thermal eects, overcurrent, ault currents, and overvoltage. Figure 90–2

Figure 90–3

(1) Public and private premises, including buildings or structures, mobile homes, recreational vehicles, and foating buildings. (2) Yards, lots, parking lots, carnivals, and industrial substations. (3) Conductors and equipment connected to the utility supply. (4) Installations used by an electric utility, such as oce buildings, warehouses, garages, machine shops, recreational buildings, and other electric utility buildings that aren’t an integral part o a utility’s generating plant, substation, or control center. Figure 90–4 Figure 90–2

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Mike Holt’s Illustrated Guide to Understanding the 2011 National Electrical Code, Volume 1

90.2


Figure 90–4

(B) What Isn’t Covered. The NEC doesn’t apply to: (1) Transportation Vehicles. Installations in cars, trucks, boats, ships

Figure 90–5

and watercrat, planes, electric trains, or underground mines. (2) Mining Equipment. Installations underground in mines and selpropelled mobile surace mining machinery and its attendant electrical trailing cables. (3) Railways. Railway power, signaling, and communications wiring. (4) Communications Utilities. The installation requirements o the NEC don’t

apply to communications (telephone), Community Antenna

Television (CATV), or network-powered broadband utility equipment located in building spaces used exclusively or th ese purposes, or outdoors i the installation is under the exclusive control o the communications utility. Figures 90–5 and 90–6 Author’s Comment: Interior wiring for communications systems,notinbuildingspacesusedexclusivelyforthesepurposes, mustbe installedin accordance with the following Chapter 8 Articles: • TelephoneandData,Article800 • CATV,Article820 • Network-PoweredBroadband,Article830

Figure 90–6

(5) Electric Utilities. The NEC doesn’t apply to installations under the exclusive control o an electric utility where such installations: a. Consist o service drops or service laterals and associated metering. Figure 90–7 b. Are on property owned or leased by the electric utility or the purpose o generation, transormation, transmission, distribution, or metering o electric energy. Figure 90–8


3

90.3


Figure 90–7

Figure 90–9

d. Are located by other written agreements either designated by or recognized by public service commissions, utility commissions, or other regulatory agencies having jurisdiction or such installations; limited to installations or the purpose o communications, metering, generation, control, transormation, transmission, or distribution o electric energy where legally established easements or rights-o-way can’t be obtained. These installations are limited to ederal lands, Native American reservations through the U.S. Department o the Interior Bureau o Indian Aairs, military bases, lands controlled by port authorities and state agencies and departments, and lands owned by railroads.

Figure 90–8

Author’s Comment:Luminaireslocatedinlegallyestablished easements,orrights-of-way,suchasatpolessupportingtrans missionordistributionlines,areexemptfromtheNEC .However, if the electric utility provides site and public lighting on privateproperty,thentheinstallationmustcomplywiththeCode [90.2(A)(4)].

Note to 90.2(B)(4) and (5): Utilities include entities that install, operate, and maintain communications systems (telephone, CATV, Internet, satellite, or data services) or electric supply (generation, transmission, or distribution systems) and are designated or recognized by governmental law or regulation by public service/utility commissions. Utilities may be subject to compliance with codes and standards covering their regulated activities as adopted under governmental law or regulation.

90.3 Code Arrangement. The

Code is

divided into an intro-

duction and nine chapters. Figure 90–10 General Requirements. The requirements contained in Chapters 1, 2, 3, and 4 apply to all installations.

c. Are located on legally established easements, or rights-oway. Figure 90–9

4

Author’s Comment:Thesefirstfourchaptersmaybethought ofasthefoundationfortherestoftheCode ,andarethemain focusofthistextbook.


90.4


• AnnexC.RacewayFillTablesforConductorsandFixture WiresoftheSameSize • AnnexD.Examples • AnnexE.TypesofConstruction • AnnexF.CriticalOperationsPowerSystems(COPS) • AnnexG.SupervisoryControlandDataAcquisition(SCADA) • AnnexH.AdministrationandEnforcement

90.4 Enforcement. The

Code is

intended to be suitable or

enorcement by governmental bodies that exercise legal jurisdiction over electrical installations or power, lighting, signaling circuits, and communications systems, such as: Figure 90–11

Figure 90–10

Special Requirements. The requirements contained in Chapters 5, 6, and 7 apply to special occupancies, special equipment, or other special conditions. These chapters can supplement or modiy the requirements in Chapters 1 through 4. Communications Systems. Chapter 8 contains the requirements or communications systems, such as telephone systems, antenna wiring, CATV, and network-powered broadband systems. Communications systems aren’t subject to the general requirements o

Figure 90–11

Chapters 1 through 4, or the special requirements o Chapters 5 through 7, unless there’s a specic reerence in Chapter 8 to a rule in Chapters 1 through 7. Author’s Comment:AnexampleofhowChapter8worksisin therulesforworkingspaceaboutequipment.Thetypical3ft workingspaceisn’trequiredinfrontofcommunicationsequip ment,becauseTable110.26(A)(1)isn’treferencedinChapter8. Tables. Chapter 9 consists o tables applicable as reerenced in the NEC .

The tables are used to calculate raceway sizing, conductor ll,

the radius o raceway bends, and conductor voltage drop.

Signaling circuits which include: • Article725Class1,Class2,andClass3Remote-Control, Signaling, and Power-Limited Circuits • Article760FireAlarmSystems • Article770OpticalFiberCablesandRaceways Communications systems which include: • Article800CommunicationsCircuits(twisted-pair conductors) • Article810RadioandTelevisionEquipment(satellitedish and antenna)

Annexes. Annexes aren’t part o the Code , but are included or inormational purposes. There are eight Annexes: • AnnexA.ProductSafetyStandards • AnnexB.ApplicationInformationforAmpacityCalculation

• Article820CommunityAntennaTelevisionandRadio Distribution Systems (coaxial cable) • Article830Network-PoweredBroadbandCommunications Systems


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90.5


Author’s Comment:Theinstallationrequirementsforsignaling circuitsandcommunicationscircuitsarecoveredinMikeHolt’s Understanding the National Electrical Code, Volume 2 textbook. The enorcement o the NEC is the responsibility o the authority having jurisdiction (AHJ), who is responsible or interpreting requirements, approving equipment and materials, waiving Code requirements, and ensuring equipment is installed in accordance with listing instructions. Author’s Comment: See the definition of “Authority Having Jurisdiction”inArticle100. Interpretation of the Requirements. The authority having jurisdiction is responsible or interpreting the NEC , but his or her decisions must be based on a specic Code requirement. I an installation is rejected,

Figure 90–12

the authority having jurisdiction is legally responsible or inorming the installer o which specic NEC rule was violated.

Waiver of New Product Requirements. I the 2011 NEC requires products that aren’t yet available at the time the Code is adopted, the

Author’s Comment:Theartofgettingalongwiththeauthor ityhavingjurisdictionconsistsofdoinggoodworkandknowing whattheCode actuallysays(asopposedtowhatyouonlythink itsays).It’salsousefultoknowhowtochooseyourbattleswhen theinevitabledisagreementdoesoccur. Approval of Equipment and Materials.Onlytheauthorityhavingjuris-

authority having jurisdiction can allow products that were acceptable in the previous Code to continue to be used. Author’s Comment: Sometimes it takes years before testing laboratoriesestablishproduct standardsfor new NEC requirements,andthenittakestimebeforemanufacturerscandesign, manufacture,anddistributetheseproductstothemarketplace.

diction has authority to approve the installation o equipment and materials. Typically, the authority having jurisdiction will approve equipment listed by a product testing organization, such as Underwriters Laboratories Inc. (UL). The NEC doesn’t require all equipment to be

90.5 Mandatory Requirements and Explanatory Material.

listed, but many state and local AHJs do. See 90.7, 110.2, 110.3, and

(A) Mandatory Requirements. In the NEC the words “shall” or “shall

the denitions or “Approved,” “Identied,” “Labeled,” and “Listed” in

not,” indicate a mandatory requirement.

Article 100. Figure 90–12 Author’s Comment:AccordingtotheNEC ,theauthorityhaving jurisdictiondetermines the approvalof equipment.This means heorshecanrejectaninstallationoflistedequipmentandcan approvetheuseofunlistedequipment.Givenourhighlylitigious society,approvalofunlistedequipmentisbecomingincreasingly difficulttoobtain.

Author’s Comment: For the ease of reading this textbook, theword“shall”hasbeenreplaced withtheword“must,”and the words “shall not” have been replaced with “must not.” Rememberthat in manyplaces, we willparaphrasethe Code insteadofprovidingexactquotes,tomakeiteasiertoreadand understand. (B) Permissive Requirements. When the Code uses “shall be per-

Waiver of Requirements. By special permission, the authority having

mitted” it means the identied actions are permitted but not required,

jurisdiction can waive specic requirements in the Code or permit

and the authority having jurisdiction isn’t permitted to restrict an

alternative methods where it’s assured equivalent saety can be

installation rom being done in that manner. A permissive rule is oten

achieved and maintained.

an exception to the general requirement.

Author’s Comment: Special permission is defined inArticle 100asthewrittenconsentoftheauthorityhavingjurisdiction.

6


90.9


Author’s Comment:Foreaseofreading,thephrase“shallbe permitted,”asusedintheCode ,hasbeenreplacedinthistext bookwiththephrase“ispermitted”or“arepermitted.” (C) Explanatory Material. Reerences to other standards or sections o the NEC , or inormation related to a Code rule, are included in the orm o Inormational Notes. Such notes are or inormation only and aren’t enorceable as a requirement o the NEC . For example, Inormational Note 4 in 210.19(A)(1) recommends that the voltage drop o a circuit not exceed 3 percent. This isn’t a requirement; it’s just a recommendation. Author’s Comment:Forconvenienceandeaseofreadingin thistextbook,IwillidentifyInformationalNotessimplyas“Note.” Figure 90–13 (D) Informative Annexes. Nonmandatory inormation annexes contained in the back o the Code book are or inormation only and aren’t enorceable as a requirement o the NEC .

90.9 Units of Measurement. (B) Dual Systems of Units. Both the metric and inch-pound mea-

90.6 Formal Interpretations. To promote uniormity o inter-

surement systems are shown in the NEC , with the metric units

pretation and application o the provisions o the NEC , ormal interpre-

appearing rst and the inch-pound system immediately ollowing in

tation procedures have been established and are ound in the NFPA

parentheses.

Regulations Governing Committee Projects. Author’s Comment: This is rarely done because it’s a very time-consuming process, and formal interpretations from the NFPAaren’tbindingontheauthorityhavingjurisdiction.

90.7 Examination of Equipment for Product Safety. Product evaluation or saety is typically perormed by a testing laboratory, which publishes a list o equipment that meets a nationally recognized test standard. Products and materials that are listed, labeled, or identied by a testing laboratory are generally approved by the authority having jurisdiction. Author’s Comment: See Article 100 for the definition of “Approved.”

Author’s Comment:ThisisthestandardpracticeinallNFPA standards,eventhoughtheU.S.constructionindustryusesinchpoundunitsofmeasurement.Youwillneedtobecautiouswhen usingthetablesinthe Code becausetheadditionalunitscan makethetablesmorecomplexandmoredifficulttoread. (D) Compliance. Installing electrical systems in accordance with the metric system or the inch-pound system is considered to comply with the Code . Author’s Comment:Sincecompliancewitheitherthemetricor theinch-poundsystemofmeasurementconstitutescompliance withtheNEC ,thistextbookusesonlyinch-poundunits.

Listed, actory-installed, internal wiring and construction o equipment need not be inspected at the time o installation, except to detect alterations or damage [300.1(B)]. Figure 90–13


7

ARTICLE

90

Practice Questions

These questions are based on the 2011 National Electrical Code . Please use the 2011 NEC Code book to answer the following questions.

5.

Utilities may be subject to compliance with codes and standards covering their regulated activities as adopted under governmental law or regulation. (a) True

Article 90. Introduction—Practice Questions 1.

(b) False

The NEC is _____. 6.

Communications wiring such as telephone, antenna, and CATV

(a) intended to be a design manual

wiring within a building shall not be required to comply with

(b) meant to be used as an instruction guide or untrained

the installation requirements o Chapters 1 through 7, except

persons

where speciically reerenced in Chapter 8.

(c) or the practical saeguarding o persons and property (a) True

(d) published by the Bureau o Standards

(b) False 2.

Hazards oten occur because o _____. 7. (a) overloading o wiring systems by methods or usage not in

The _____ has the responsibility or deciding on the approval o equipment and materials.

conormity with the NEC (a) manuacturer

(b) initial wiring not providing or increases in the use o elec-

(b) authority having jurisdiction

tricity

3.

(c) a and b

(c) testing agency

(d) none o these

(d) none o these

This Code covers the installation o _____ or public and

8.

private premises, including buildings, structures, mobile

_____.

homes, recreational vehicles, and loating buildings.

(a) making interpretations o rules

(a) optical iber cables

(b) deciding upon the approval o equipment and materials

(b) electrical equipment

(c) waiving speciic requirements in the Code and permitting alternate methods and material i saety is maintained

(c) raceways

(d) all o these

(d) all o these

4.

The authority having jurisdiction has the responsibility or

Installations o communications equipment that are under

9.

When the Code uses “_____,” it means the identiied actions

the exclusive control o communications utilities, and located

are allowed but not required, and they may be options or alter-

outdoors or in building spaces used exclusively or such instal-

native methods.

lations _____ covered by the NEC .

(a) shall

(a) are

(b) shall not

(b) are sometimes

(c) shall be permitted

(c) are not

(d) a or b

(d) may be

8


Practice Questions

10.

Article 90

Explanatory material, such as reerences to other standards, reerences to related sections o the NEC , or inormation related to a Code rule, are included in the orm o Inormational Notes. (a) True (b) False


9

Notes

10


Introduction to the National Electrical Code

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