ID Electrician cheat sheet

Ohm's law: E = I × R. Power: P = E × I = I²R = E²/R, with E in volts, I in amperes, R in ohms.

NEC Chapters 1 through 4 apply generally; Chapters 5, 6, and 7 modify or supplement them; Chapter 8 (communications systems) is independent except where specifically referenced.

Articles 100 through 110 hold the definitions and general installation requirements, while Article 90 states the Code's scope and purpose.

The NEC is a minimum installation standard, not a design manual or instruction guide; the annexes are informational and are not enforceable unless adopted.

Balanced three-phase power: P = 1.732 × E(line) × I(line) × power factor.

Series resistances add directly; for parallel circuits 1/R_total = 1/R1 + 1/R2 + …, and the total is always less than the smallest branch resistance.

Conductor ampacities come from Table 310.16 with 60 °C, 75 °C, and 90 °C columns; the termination temperature rating limits the column that may be used, per 110.14(C).

Single-phase voltage drop: VD = (2 × K × I × L) ÷ circular mils, where K is about 12.9 for copper and 21.2 for aluminum.

Conductors installed in parallel must be 1/0 AWG or larger and identical in length, conductor material, size, and insulation characteristics (310.10(H)).

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

Box volume allowances from Table 314.16(B): 2.0 cubic inches per 14 AWG, 2.25 per 12 AWG, and 2.5 per 10 AWG conductor, with additional allowances for devices, clamps, and equipment grounds.

Section 110.26 requires a clear working space 3 feet deep, 30 inches wide, and 6.5 feet high in front of equipment likely to be examined while energized.

Nonmetallic-sheathed cable must be secured within 12 inches of each box and at intervals not exceeding 4.5 feet, and is not permitted in wet locations.

Dwelling receptacle spacing (210.52(A)): no point along a floorline may be more than 6 feet from a receptacle outlet, and wall spaces 2 feet or wider are counted.

The grounded conductor is identified by white, gray, or three continuous white stripes; the equipment grounding conductor is green, green with yellow stripes, or bare.

Support intervals: EMT within 3 feet of a box and at least every 10 feet; rigid metal and intermediate metal conduit at least every 10 feet.

Table 300.5 minimum cover: 24 inches for direct-buried cable generally, 18 inches for nonmetallic raceway, 12 inches for a 120-volt, 20-ampere GFCI-protected residential branch circuit.

Penetrations of fire-rated assemblies by cable or raceway must be sealed with a listed firestop method rated for the assembly.

Standard overcurrent device ratings (240.6(A)) include 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, and 200 amperes.

Small-conductor limits (240.4(D)): 14 AWG copper is protected at 15 amperes, 12 AWG at 20 amperes, and 10 AWG at 30 amperes unless a specific permission applies.

Next-size-up rule (240.4(B)): where conductor ampacity does not match a standard rating, the next higher standard device may be used up to 800 amperes, provided the load does not exceed the conductor ampacity.

Continuous loads: conductors and overcurrent devices are sized at not less than 125 percent of the continuous load plus 100 percent of the noncontinuous load (210.20(A), 215.3).

A feeder runs from the service equipment or a separately derived source to the final branch-circuit overcurrent device; the branch circuit runs from that device to the outlets.

GFCI protection is required for dwelling bathrooms, kitchens, garages, outdoors, unfinished basements, crawl spaces, and receptacles within 6 feet of sinks and laundry basins.

AFCI protection is required for 120-volt, 15- and 20-ampere branch circuits in dwelling units, including bedrooms, under 210.12.

Recommended voltage drop limits are 3 percent on a branch circuit and 5 percent total for feeder plus branch, per the informational notes to 210.19(A).

A multiwire branch circuit must have a means that simultaneously disconnects all ungrounded conductors at the point where it originates (210.4(B)).

Section 250.50 requires all grounding electrodes present at a building to be bonded together into a single grounding electrode system.

A driven ground rod must be at least 8 feet long and driven the full 8 feet; if it does not measure 25 ohms or less to earth, one additional electrode must be added.

The main bonding jumper is installed only at the service or at a separately derived system; neutral-to-ground connections downstream of the service are prohibited.

Table 250.66 sizes the grounding electrode conductor from the largest ungrounded service-entrance conductor.

Table 250.122 sizes the equipment grounding conductor from the rating or setting of the overcurrent device protecting the circuit, not from conductor ampacity.

A Class A ground-fault circuit interrupter trips at 5 milliamperes plus or minus 1 milliampere and is used for personnel protection.

Metal water piping must be bonded, and a bonding jumper around removable fittings such as water meters maintains electrical continuity.

The equipment grounding conductor must form a permanent, low-impedance path capable of carrying fault current that will open the overcurrent device.

Branch-circuit conductors for a single motor must have an ampacity of at least 125 percent of the motor full-load current taken from Table 430.248 (single-phase) or 430.250 (three-phase).

Motor overload protection is generally sized at no more than 125 percent of the motor nameplate full-load amperes (430.32); up to 140 percent is permitted where the motor will not start.

Short-circuit and ground-fault protection sizing from Table 430.52: 250 percent of full-load current for an inverse-time breaker, 175 percent for a dual-element fuse, 300 percent for a nontime-delay fuse.

Each motor requires a disconnecting means within sight of and within 50 feet of the motor, or one that is capable of being locked in the open position (430.102).

Table 430.250 full-load current values are used for sizing conductors and short-circuit protection; the nameplate current is used for overload sizing.

A motor controller must have a horsepower rating not less than the motor it serves and must be capable of starting and stopping the motor.

Article 440 equipment uses rated-load current and branch-circuit selection current for hermetic refrigerant motor-compressors rather than the standard motor tables.

Motor control circuits tapped from the branch circuit require overcurrent protection sized per 430.72.

Idaho's electrical licensing statutes are codified in Title 54, Chapter 10 of the Idaho Code, which establishes the Electrical Board and licensing requirements.

The Idaho Electrical Board operates within the Idaho Division of Occupational and Professional Licenses (DOPL), which processes applications, examinations, and renewals.

License categories include apprentice, journeyman, master, and limited or specialty electrician licenses, each with distinct scope and qualifications.

Idaho adopts the National Electrical Code by Board rule with state amendments; local authorities having jurisdiction issue permits and perform inspections.

Journeyman and master applicants must document qualifying work experience and pass a licensing examination.

Continuing education hours are required for license renewal, with the specific hours and cycle set by Board rule.

Apprentices must be registered with the state and work under the supervision of a licensed journeyman or master electrician.

Performing electrical work without a required license or permit is subject to civil and criminal penalties under Idaho law.