xvii The second type is the permissive rule as defined in NEC 90.5(B). Permissive rules allow discre- tionary compliance, where optional or alternative methods are permitted. They are identified by the terms “shall be permitted” or “shall not be required.” Examples of permissive rules are NEC 210.4(A), 220.52(B), 225.7(D), and 240.4(B). 8. Exceptions. Exceptions provide alternatives to specific rules. They are distinctively written in italics. Consider the following: Example (the rule): NEC 210.3 states that the ratings for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes. Statement: Multioutlet branch circuits shall not exceed a 50 amperes rating. Answer: The statement is true based on the rule. Only individual (separate) branch circuits are allowed to have a rating of 50 amperes or higher. Statement: A No. 10 conductor having an ampacity of 30 amperes supplies a branch circuit that is protected by a 20-ampere circuit breaker. The branch circuit is rated for 30 amperes. Answer: The statement is false based on the rule. The rating of a branch circuit is based on the ampere rating or setting of the specified overcurrent device. Therefore, the branch circuit is rated for 20 amperes. Example (the exception to the rule): The exception to NEC 210.3 states that a multioutlet branch circuit greater than 50 amperes is permitted to supply nonlighting outlet loads on industrial premises where conditions of maintenance and supervision ensure that only qualified persons service the equipment. Statement: Two 100 amps multioutlet branch circuits supplying several single receptacle outlets in a steel manufacturing plant are permitted as long as the plant is maintained and supervised by individuals who are qualified to service these type circuits. Answer: The statement is true based on the condition of the exception to the rule. 9. Informational Notes. What was referred to in previous editions of the code as a fine print note is now called an informational note in the 2011 NEC. Informational notes identify explanatory material [90.5(C)]. Informational notes are only used to provide information such as references to other standards, references to related sections of the code, or information related to a code rule. Informational notes are not enforceable requirements of the code. Examples of informational notes include those listed with NEC 110.5, 200.7(C)(2), 250.116(3), and 406.9(A). 10. Definitions. Part I of Article 100 provides the definition of terms that are used in two or more articles of the NEC. Terms that are common to an article or a particular part of an article of the
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The second type is the permissive rule as defined in NEC 90.5(B). Permissive rules allow discre-tionary compliance, where optional or alternative methods are permitted. They are identified by the terms “shall be permitted” or “shall not be required.” Examples of permissive rules are NEC 210.4(A), 220.52(B), 225.7(D), and 240.4(B).
8. Exceptions. Exceptions provide alternatives to specific rules. They are distinctively written in italics. Consider the following:
Example (the rule): NEC 210.3 states that the ratings for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes.
Statement: Multioutlet branch circuits shall not exceed a 50 amperes rating.
Answer: The statement is true based on the rule. Only individual (separate) branch circuits are allowed to have a rating of 50 amperes or higher.
Statement: A No. 10 conductor having an ampacity of 30 amperes supplies a branch circuit that is protected by a 20-ampere circuit breaker. The branch circuit is rated for 30 amperes.
Answer: The statement is false based on the rule. The rating of a branch circuit is based on the ampere rating or setting of the specified overcurrent device. Therefore, the branch circuit is rated for 20 amperes.
Example (the exception to the rule): The exception to NEC 210.3 states that a multioutlet branch circuit greater than 50 amperes is permitted to supply nonlighting outlet loads on industrial premises where conditions of maintenance and supervision ensure that only qualified persons service the equipment.
Statement: Two 100 amps multioutlet branch circuits supplying several single receptacle outlets in a steel manufacturing plant are permitted as long as the plant is maintained and supervised by individuals who are qualified to service these type circuits.
Answer: The statement is true based on the condition of the exception to the rule.
9. Informational Notes. What was referred to in previous editions of the code as a fine print note is now called an informational note in the 2011 NEC. Informational notes identify explanatory material [90.5(C)]. Informational notes are only used to provide information such as references to other standards, references to related sections of the code, or information related to a code rule. Informational notes are not enforceable requirements of the code. Examples of informational notes include those listed with NEC 110.5, 200.7(C)(2), 250.116(3), and 406.9(A).
10. Definitions. Part I of Article 100 provides the definition of terms that are used in two or more articles of the NEC. Terms that are common to an article or a particular part of an article of the
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NEC only apply to that particular reference. Terms that are common to an article are, for the most part, found in the second section (indicated by “.2”) of that particular article (e.g., the definitions found in NEC 240.2, 250.2, 366.2, and 440.2). Terms that are common to a particular part of an article are listed according to applicable sections (e.g., Part IX of Article 424). The definitions listed in NEC 424.91 are only applicable to Part IX.
As an example of how a term is actually introduced and gradually integrated within the code book based on the effects of year-to-year changes in the electrical field, let’s take a look at the origin of the term arc fault circuit interrupter.
In the 1999 edition of the NEC, the term arc fault circuit interrupter was first introduced by the initia-tion of section 210.12, with subsection 210.12(a) providing a definition of the term. From the 1999 edition and up to the 2008 edition, the term and definition were only applicable to section 210.12.
In the 2011 edition of the NEC, the definition [subsection 210.12(A)] has now been removed from section 210.12 and placed in Article 100, which implies that the term is used in at least two or more articles of the NEC. As a result, the term arc fault circuit interrupter is not only found in Article 210 [section 210.12(A)] but also in Articles 406 [406.4(D)(4)], 550 [section 550.25], and 690 [690.11], as referenced in the index of the 2011 edition. However, section 440.65 also appears in the index, as the mentioned arc fault circuit interrupter requirement applies to the attachment plug of a room air conditioner and not the protection of a circuit.
Part II of Article 100 provides the definition of terms specifically covering installations and equip-ment operating over 600 volts, nominal.
11. Changes, Deletions, Extracted Text. Any information listed in the current 2011 NEC that differs from the 2008 NEC is identified as follows:
Changes. Prior to the 2008 NEC, a vertical line or bar ( ) appearing in the margins of the NEC was used exclusively to identify a section or sections that had been changed (revised). Changes other than editorial are highlighted with gray shading within the applicable section of interest. Vertical lines or bars are used to identify large blocks of changed or new text and for new tables and changed or new figures.
Deletions. A bullet (•) appearing in the margins of the NEC identifies an area in which contents have been deleted (removed). A deletion does not mean the deleted contents have been totally removed from the NEC, as they could possibly be located elsewhere in the NEC.
Extracted Text. Prior to the 2002 NEC, a superscript (x) was used to identify material extracted from other NFPA documents. Such extracted (taken from another source) material now appears between brackets ([ ]) in the NEC. For example, 517.34 was extracted from NFPA 99, Section 4-4.2.2.3.2.
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**Section only applicable to flexible metallic Tubing, Type FMT
*** Section only applicable to Types PVC and RTRC nonmetallic conduit
As you can see, the formatting and structure is practically the same (with the exception of section topics) and so is the approach for finding answers and information promptly as applied to these articles. Now, if a question or needed information arises pertaining to raceway sizes and ground-ing, simply refer to sections .20 and .60 of the applicable article.
Finally, because of the difficulties often found with hazardous (classified) areas, we’ll conclude this section by reviewing Articles 501, 502, and 503. These three articles are perhaps the most frequently used articles of Chapter 5, pertaining to classified areas.
Now, observe the format on the following page. Close attention should be made to each particular hazard of concern that’s associated with each classified area. If a question were asked or if one had a need to know about the classification of an area containing “flammable liquids,” chances are the first thing a user would have the tendency to do is began searching each article of the NEC pertaining to classified areas. With the help of the given format and the further familiarization of it, the user can easily identify “flammable liquids” with Class I areas of Article 501. For clearly, the format (Hazard of Concern) shows, and is further stated in each respective article, that Article 501 covers Class I Locations where the presence of flammable gases or vapors or liquids may exist, that Article 502 covers Class II Locations where the presence of combustible dust may exist, and that Article 503 covers Class III Locations where ignitable fibers/flyings may exist. With the given format, the user is allowed to visualize and connect the three articles and classi-fied areas per locations simultaneously, without having to become familiar with them in a “not so otherwise” manner.
For another example, each classified area per hazard of concern features sections pertaining to “Wiring Methods” in both Division 1 [501. – 503.10(A)] and 2 [501. – 503.10(B)] locations.
Now, consider “Sealing and Drainage.” Observe how the referenced information only applies to Class I areas [501.15], while the reference “Sealing” only applies to Class II areas, where refer-enced information pertaining to both Division 1 and 2 locations [502.15] is combined, opposed to being presented in two separate sections.
A final example is found with the reference “Surge Protection.” Here, this reference features infor-mation that is separate for Division 1 and 2 locations for Class I areas [501.35(A) and 501.35(B)] compared to Class II areas, in which the same section is used for both Division 1 and 2 locations [502.35]. Notice that the reference “Surge Protection” does not apply to Class III locations.
With the examples and further study, the given format of the three classified locations can cer-tainly lead to an understanding or better comprehension of Articles 501, 502, 503, and other similar articles and related subject matters.
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Hazardous (Classified) Areas
Article 501 Article 502 Article 503 Class I Locations Class II Locations Class III Locations
Hazard of concern flammable gases combustible dust ignitable fibers/flyings or vapors or liquids
Number of Multiconductor Cables, Rated 2000 Volts or Less, in Cable Trays 392.9 392.22(A)
Table (Allowable Cable Fill Area for Multiconductor Cables in Ladder, Ventilated Trough, or Solid Bottom Cable Trays for Cables Rated 2000 Volts or Less 392.9 392.22(A)
Table (Allowable Cable Fill Area for Multiconductor Cables in Ventilated Channel Cable Trays for Cables Rated 2000 Volts or Less 392.9(E) 392.22(A)(5)
Table (Allowable Cable Fill Area for Multiconductor Cables in Solid Channel Cable Trays for Cables Rated 2000 Volts or Less 392.9(F) 392.22(A)(6)
Number of Single-Conductor Cables, Rated 2000 Volts or Less, in Cable Trays 392.10 392.22(B)
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Chapter 3—Wiring Methods and Material
artiCle 398–open WirinG on insulators==================================================================
1. Conductors smaller than No. 8 AWG shall be rigidly supported within __________ of a dead-end connection to a receptacle.a. 8" b. 10" c. 6" d. 12"
2. Open wiring on insulators is permitted inside agricultural establishments if rated for 600 volts nominal or less.a. True b. False
3. Where nails are used to mount knobs, they shall not be smaller than ten penny.a. True b. False
4. No. 8 and larger conductors installed across open spaces are permitted to be supported up to 15 feet apart if noncombustible, nonabsorbent insulating spacers are used at least every __________ feet to maintain at least 2.5 inches between conductors.a. 4.5 b. 7 c. 9 d. 6.5
5. Conductors used for open wiring shall be separated at least __________ from metal race-ways, piping, or other conducting material.a. 4" b. 1" c. 3" d. 2"
artiCle 399–outdoor overhead ConduCtors over 600 volts==================================================================
1. Only a licensed professional engineer engaged primarily in the design of structures and sup-ports for outdoor overhead conductors can produce documentation of the engineered design. a. True b. False
2. Insulated 2.4kV overhead conductor enclosed in metal conduit are permitted to be installed indoors.a. True b. False
3. Insulated, covered, or bare single conductors installed outdoors on support structures are defined as __________ conductors.
a. insulated b. high-voltage c. outdoor overhead d. transmission
1. Only interactive fuel cell systems listed and marked as interactive shall be permitted in interactive systems.a. True b. False
2. A fuel cell system that supplies power independently of an electrical production and distri-bution network is called a(n) __________.a. independent fuel cell system b. fuel cell system c. stand-alone system d. primary power source
3. The manual fuel shut-off valve shall be at the location of the __________ disconnecting means of the building or circuits applied.a. service b. primary c. main d. power supply
4. The highest fuel cell inverter output voltage between any ungrounded conductors present at accessible output terminals is called the peak system voltage.a. True b. False
artiCle 694–sMall Wind eleCtriC systeMs==================================================================
1. For battery circuits rated over 600 volts, the voltage used shall be the highest voltage experienced under charging or equalizing conditions.a. True b. False
2. Inverters used in small wind electric systems shall be approved by the authority having jurisdiction prior to their application.
a. True b. False
3. Where used in highly conductive soils, copper and copper-clad grounding electrodes can cause ___________ corrosion of galvanized foundation and tower anchor components.a. extensive b. repeated c. electrolytic d. depleting
4. An enclosure housing the alternator and other parts of a wind turbine refers to which one of the following terms?a. tower b. nacelle c. cabinet d. compartment
1. Communications circuits shall not be required to be grounded.a. True b. False
2. Applicable grounding means shall be _______ for application with premises-powered broadband communications systems.a. approved b. readily accessible c. listed d. marked
3. The outside plant optical fiber cables shall be located below the electric light or power conductors, where practicable.a. True b. False
4. Per NEC 840.93, premises communications circuits and premises CATV circuits shall not be grounded.a. True b. False
5. An aerial non-conductive optical cable that is terminated at an optical network terminal and that establishes a communications network is defined as __________________.a. a communication system b. fiber-to-the-premises c. an optical network terminal d. a premises communications circuit
6. Optical fiber cables, where direct-buried, shall be installed to have a minimum cover of _________. a. 150 cm b. 6 in. c. 6 ft. d. 15 mm
