MI Journeyman Electrician cheat sheet

The NEC is arranged in nine chapters: Chapters 1-4 contain general rules, Chapters 5-7 supplement or modify them for special occupancies, conditions, and equipment, Chapter 8 covers communications systems, and Chapter 9 contains reference tables.

Informational Notes are explanatory only and are not enforceable; mandatory requirements are stated with 'shall' (Article 90).

Ampacities in Table 310.16 assume a 30 degrees C ambient temperature and no more than three current-carrying conductors in the raceway or cable.

Terminations for circuits rated 100 A or less are limited to the 60 degrees C ampacity column unless the equipment is listed and marked for a higher termination temperature (110.14(C)).

Table 110.26(A)(1) working-space depth: 3 ft for 0-150 V to ground, 3.5 ft for 151-600 V, 4 ft for 601-2500 V; minimum width 30 in.; minimum height 6 ft 6 in.

The working space in front of electrical equipment must be clear and the footprint must be dedicated exclusively to electrical equipment (110.26(E)).

Section 90.4 gives the authority having jurisdiction responsibility for interpreting the code, approving listed materials and methods, and granting written approval of alternate installations.

In Michigan, electrical contractors, master and journeyman electricians, and apprentices are licensed under the Electrical Administrative Act, Public Act 217 of 1956, administered through the Bureau of Construction Codes.

Michigan adopts the NEC by reference with state amendments as the Michigan Electrical Code; the edition currently in effect governs plan review and field inspection.

230.79(C): the service disconnecting means for a one-family dwelling must have a rating of not less than 100 A.

230.71: service disconnecting means must be grouped in one location, and where multiple means are permitted no more than six are allowed.

310.12: 120/240 V single-phase service and feeder conductors supplying a dwelling unit may be sized at 83 percent of the service rating, with a 100 A minimum service.

220.12: the general lighting load for a dwelling unit is calculated at 3 VA per square foot of floor area.

210.11(C)(1): at least two 20 A small-appliance branch circuits are required for kitchen, dining, pantry, and similar receptacle outlets, and no other outlets may be supplied from them (210.52(B)(2)).

210.52(A)(1): in dwelling units, no point along the floor line of any wall space may be more than 6 ft from a receptacle outlet (the 6 ft / 12 ft rule).

210.52(C)(1): no point along a kitchen countertop wall line may be more than 24 in. from a receptacle outlet; islands and peninsulas require at least one receptacle.

Informational Notes to 210.19(A) and 215.2(A): voltage drop should not exceed 3 percent on a branch circuit or 5 percent total for feeder plus branch circuit.

210.20(A): the branch-circuit overcurrent device rating must not be less than the branch-circuit conductor ampacity, and the conductors must have an ampacity not less than the load.

Chapter 9 Table 1 raceway fill: 53 percent for one conductor, 31 percent for two conductors, and 40 percent for three or more conductors of the interior cross-sectional area.

358.30: electrical metallic tubing must be fastened within 3 ft of each box or termination and supported at intervals not exceeding 10 ft.

334.30: nonmetallic-sheathed cable must be secured within 12 in. of each box and supported at intervals not exceeding 4.5 ft.

300.4(A): cable or raceway through bored framing members must be at least 1-1/4 in. from the nearest edge, or protected by a steel plate at least 1/16 in. thick.

314.16(B) box-fill volume per conductor: 14 AWG = 2.00 cu in., 12 AWG = 2.25 cu in., 10 AWG = 2.50 cu in.; each yoke or device counts as one conductor, and all equipment grounding conductors count together as one.

314.28(A): pull-box length must be at least 8 times the trade size of the largest raceway for straight pulls, and 6 times for angle or U pulls measured between raceway entries.

200.6: grounded conductors 6 AWG and smaller must be white or gray, or identified with white or gray marking at terminations.

250.119: equipment grounding conductors must be bare, green, or green with one or more yellow stripes; white and gray are not permitted.

310.15(B)(3)(a) ampacity adjustment for more than three current-carrying conductors in a raceway or cable: 4-6 conductors 80 percent, 7-9 conductors 70 percent, 10-20 conductors 50 percent.

430.22: motor branch-circuit conductors must have an ampacity of at least 125 percent of the motor full-load current from Table 430.248 or 430.250.

Table 430.52 maximum branch-circuit short-circuit protection for motors: inverse-time breaker 250 percent, dual-element fuse 175 percent, non-time-delay fuse 300 percent of full-load current.

430.32: motor overload protection is sized from the nameplate service factor and temperature rise, generally 115 to 125 percent of full-load current.

440.6 and 440.32: air-conditioning equipment is wired using the nameplate minimum circuit ampacity for conductors and the nameplate maximum overcurrent rating for the protective device.

404.8(A): switches and circuit breakers used as switches must not be located more than 6 ft 7 in. above the floor or working platform.

406.12: listed tamper-resistant receptacles are required in dwelling units, guest rooms, and specified child-care and educational occupancies.

410.8: luminaires in clothes closets require 12 in. of clearance from storage space for surface-mounted incandescent types and 6 in. for recessed incandescent types.

450.3(B): where only primary protection is provided for a transformer rated 1000 V or less, the primary overcurrent device may not exceed 125 percent of primary current when primary current is 9 A or more.

210.21(B)(1): a single receptacle on an individual branch circuit must have a rating not less than the rating of the branch circuit.

250.52(A): grounding electrodes include metal underground water pipe (10 ft or more of contact), metal building frame, concrete-encased electrode (20 ft of 1/2 in. rebar), ground ring (20 ft), rod or pipe electrode (8 ft), and plate electrodes.

250.53(A)(2): a single rod, pipe, or plate electrode must have a resistance to earth of 25 ohms or less, or a supplemental electrode must be added.

Table 250.66 copper grounding electrode conductor: 2 AWG or smaller service conductors = 8 AWG; 2/0-3/0 = 4 AWG; over 350 through 600 kcmil = 1/0; over 1100 kcmil = 3/0.

Table 250.122 copper equipment grounding conductor: 15 A = 14 AWG, 20 A = 12 AWG, 30-60 A = 10 AWG, 100 A = 8 AWG, 200 A = 6 AWG, 300 A = 4 AWG, 400 A = 3 AWG, 600 A = 1 AWG.

250.122(B): where phase conductors are increased in size above the code minimum, the equipment grounding conductor must be increased proportionally by circular mil area.

240.4(D): small conductor overcurrent limits are 15 A for 14 AWG copper, 20 A for 12 AWG copper, and 30 A for 10 AWG copper, unless specifically permitted elsewhere.

240.4(B): the next higher standard overcurrent device is permitted where conductor ampacity does not exceed 800 A, the device rating does not exceed 800 A, and the circuit is not a multioutlet receptacle branch circuit.

Class I Division 1 locations are those where ignitable concentrations of flammable gases, vapors, or liquids exist under normal operating conditions; Division 2 locations have them only in abnormal conditions (500.5).

501.15: in Class I locations, a sealing fitting must be installed within 18 in. of the enclosure boundary on raceways leaving the classified area.