TECHNICAL LICENSING STUDIES INC.

2. The authority having jurisdiction (i.e. electrical inspectors, etc.) has the responsibility for making interpretations of the rules, approving materials or granting special permission. 90.4 By special permission the authority may waive specific requirements and permit alternative methods. *You have the right to appeal a judgment by an official with the state construction licensing board, or the NFPA Regulations Governing Committee. 90.6

4. Fine print notes (FPN) are informational and are not enforceable as requirements. 90.(5)(c)

*Make note of paragraph 5 of History and Development of the NEC on page one of the 2002 NEC that gives an explanation of the vertical lines next to some of the text in the book. These notations indicate the location of the changes to this edition and sources of other text extracted from other NFPA publications. The number 70 in the top right corner of the page next to the page number indicates the book number, the NEC being NFPA 70. The fire code book is NFPA 72 and so on. So be aware that there are other publications that govern electrical safety, far to many to print in one book. These laws are subject to change and be enforced on a local level. *See 90.4

6. CONTINUOUS LOAD: a load where the maximum current is expected to continue for three hours or more.

8. GROUND, GROUNDED, GROUNDED EFFECTIVELY, GROUNDED CONDUCTOR (NEUTRAL), GROUNDING CONDUCTOR, GROUNDING CONDUCTOR EQUIPMENT, GROUNDING ELECTRODE CONDUCTOR: article 250 is understandably one of the most important chapters in the NEC and a large part in any licensing exam, know their differences.

13. NON-LINEAR-LOAD: a load where the wave shape of the steady-state current does not follow the wave shape of the applied voltage. *See FPN.

19. QUALIFIED PERSON: Qualified Person. One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved.

5. ELECTRICAL EQUIPMENT MOUNTED ABOVE OR BELOW ONE ANOTHER? permitted to extend not more than 6 in. beyond associated equipment of that installation. 110.26(A)(3) *the most common violation is a 277/480 to 120/208 step down transformer mounted below an electrical panel in a building’s electrical closet.

10. Foreign systems (i.e. plumbing piping) is permitted in the dedicated 6 ft. space above electrical equipment providing there is protection from spillage of liquids (i.e. drip pans). 110.26(F)(1)(b)

27. Arc-fault protection required for all 15 and 20 amp receptacle circuits in dwelling bedrooms. 210.12(B)

36. Receptacles shall not be located more than 20 inches above a counter top. 210.52(C)(5)
*receptacle requirements for counter tops and wall outlets are established because of the length of the appliance cords used in those areas, so that there would never be a need for an extension cord. Wall outlets are 12 ft. apart because appliance cords for those areas are 6 ft. An appliance in between two receptacles 12 ft. apart would not require and extension cord. Cords for counter appliances are 2 ft., therefore the dimensions of 4 ft. between receptacles was established.

79. What is the minimum size thwn-2 (90) conductor needed to supply a motor with a 24 ampere load? #12. 240.4(D), 240.4(G) *This article was added to the 1999 NEC replacing the obelisk at the bottom of the table 310.16 which stated that "unless otherwise specifically permitted elsewhere in this code, the overcurrent protection for conductor types marked with an obelisk shall not exceed 15 amperes for #14, 20 amperes for #12 and 30 amperes for #10 copper......and so on. This was a bit confusing because it never really specified when was "elsewhere permitted in this code". Article 240.4(D) specifies

82. Conductors shall be permitted to be tapped without overcurrent protection at the tap up to 25 ft. away providing the ampacity of the conductors is rated at what percent of the feeder conductors? 1/3. 240.21(B)(2) *read all of the tap rules, they are often asked on exams.

106. Enclosures for grounding electrode conductors? electrically continuous (bonded at both ends) 250.64(E)

125. Penetrations through floors and fire rated walls shall be sealed in accordance with article 300.21 Openings to be firestopped with approved methods. *see the fine print note (FPN) where it uses an example of boxes on opposite sides of a wall with a minimum of 24 inch horizontal spacing.

135. WHAT IS THE MINIMUM WIRE BENDING SPACE NEEDED FOR THE DEFLECTION AND CONNECTION OF PARALLELED PAIRS OF 4/0 CONDUCTORS IN A PANELBOARD? O.K., I worded this one just as it may be asked on an exam. The key word here is deflection. This means that the conductors will not be entering the cabinet directly opposite the lugs. The lugs meaning either the main lugs or the lugs of a circuit breaker. This dimension is measured directly across in a straight line from lug to cabinet wall.*Read the fine print at the bottom of the table.

168. Supports for and rigid metal conduit? maximum 3 ft. from a box or conduit body and every 10 ft. thereafter. 344.30(A) & (B) Dimensions for larger size conduits are on Table 344.30.(B)(2)

190. Can a junction box without devices be supported solely by two or more emt conduits? No. Boxes must have threaded entries or hubs identified for use and have their conduits two or more, threaded, wrenchtight and be supported within the dimensions of 370-23e. Conduit bodies (i.e. condulets, lb’s etc.) however are permitted. *see article 100 for a definition of a conduit body where box types FS and FD although having threaded hubs are not considered conduit bodies.

202. Concealed knob an tube permitted to be installed to existing installations. 394.10

223. Smallest size fixture wire for pendant incandescent lamps? #14 for mogul or medium base, #18 for candelabra base. 410.27

235. When may a switch or circuit breaker be used as a disconnect for permanently
connected appliances rated over 300 va or 1/8 hp? must be in sight and capable of being locked in the open position. 422.31(B)

259. How many amps does a 1 hp single phase ac motor draw at 208 volts? 11. table 430.148

283. Class 1 locations that an electrical malfunction could cause ignitable concentrations of flammable gases or vapors shall be considered? Class 1, Division 1. 500.5(B)(1)(3)

307. Where shall the sealing fitting at a dispensing pump be located? the first fitting after the conduit emerges from the earth or ground. 514.9(A)

315. Receptacles for general care patient bed locations? four or more, hospital grade, grounded with insulated copper conductor 517.18(B) *See exceptions

339. Fire pump disconnecting means marking to be visible without opening enclosures, have their letters at least 1 inch in height and shall be marked "Fire Pump Disconnecting Means". 695.4(B)(3)

357. Grounding communications systems to buildings with no ground? ground rod or pipe not less than 5 ft. in length and 1/2 in. in diameter driven in damp earth and separated from lightning conductors or electrodes of other systems by at least 6 ft. 800.40(B)(2)(2)

2. How many #8 thwn conductors can be added to an 1 1/4” emt conduit containing 2 #8 thwn conductors and 3 #6 THWN conductors? (*again no mention of ampacity, no derating)

Answer:
	step 1 -	Turn to chapter 9, table 5, pg. 622, column 1 in extended table on the right and find #8 THWN
	step 2 -	Read across to column 6, #8 THWN has an area of .0366
	step 3 -	0366 x 2 conductors = .0732
	step 4 -	Find #6 THWN in column 1 of the same table and read across to column 6, #6 THWN has an area of .0507
	step 5 -	.0507 x 3 conductors = .1521
	step 6 -	Add all conductor areas, .1521 (3 #6’s) + .0732 (2 #8’s) = .2253
	step 7 -	Turn to table 4 pg. 617, EMT table, column 2 and find 1 1/4”, then read across to column 10, 40% fill. 1 1/4” has an area of .598
	step 8 -	Subtract the area of the conduit by the total area of the conductors to find the remaining area of unused conduit. .598 - .2253 = 5.75. 5.75 is the area remaining not exceeding 40% fill.
	step 9 -	Go back to table 5 pg. 622 and read across to column 6 again, #8 THWN as shown in step 2 has an area of .0366
	step 10 -	Divide the remaining area of conduit by the area of #8 THWN .3727 / .0366 = 10.1 10 - #8 THWN conductors can be added without exceeding the conduit’s 40% fill.

1. HOW MANY #12 THWN-2 CONDUCTORS CAN BE INSTALLED IN A 1/2” CONDUIT, AND STILL HAVE THE AMPACITY OF THE WIRE RATED AT 20 AMPS? ***Most #12 stranded wire used in common electrical installations are now 90oC (194oF) dual rated as THHN or THWN-2, the “w” meaning suitable for wet locations.

step 1 -	Turn to page 144 in the NEC, table 310.16. The table is split into 2 sides, Copper on the left, Aluminum on the right. Find THWN-2 in the 90oC column (col. 4), then find #12 in the size column (col. 1). The ampacity of #12 is 30 amps. ***Note the asterisk along side of the #12, and read the note at the bottom left of the page where it refers you to section 240.4(D). “Small Conductors” explains unless specifically permitted in (E) through (G) the conductors will have the maximum overcurrent protection listed for those conductors in (D). Example: A 20 amp circuit breaker for #12 wire used for lighting, but a 30 amp (100% of Table 310.16) circuit breaker used for a/c & refrigeration, motors, etc. as permitted in (G).
step 2 -	Turn to page 142, 310.15(B)(2)(a) states, in short, current carrying conductors exceeding 3 in a cable or raceway shall have their ampacities reduced, or most commonly referred to as “derated”. See 310.15(4)(a) through (c) for a definition of neutral conductors considered current carrying. 310.15(5) states grounding or bonding conductors do not apply to adjustment factors. Remember that they do count towards the conduit’s maximum 40% fill though as stated in Chapter 9, Table 1 “over 2” conductors. Pg. 617
step 3 -	Column 1 “Number of current carrying conductors” 7 thru 9 conductors derated by 70%. #12 THWN-2 is good for 30 amps. 30 amps x 70% or 30 x .70 = 21 amps. answer - 9. 10 thru 20 conductors would be derated 50% bringing the conductor’s rated ampacity down to 15 amps. Remember, when derating, there is no mention of conduit size. 9 current carrying conductors is the maximum number of #12 conductors permitted in a conduit and the conductor still be rated for 20 amps, whether it be 1/2” EMT or 6” galvanized! Table 4 in Chapter 9, pg. 617 thru 621 column 10 is based on 40% fill when using 3 or more conductors. 40% is the maximum allowable fill for conduits over 24” in length for standard electrical installations. An easy way to remember the maximum allowable fills for conduits and raceways is to remember, 20, 40, 60. 20% for gutters or troughs, 40% for conduit, and 60% for nipples (conduits 24 in. or less).