NE Journeyman Electrician cheat sheet

Ohm's law: E = I × R; power P = E × I = I²R = E²/R. In AC circuits use impedance Z in place of R.

Single-phase power: P = E × I × PF. Balanced three-phase power: P = √3 × E_line × I_line × PF.

Series circuit: R_total = R1 + R2 + …; current is the same everywhere; voltage divides in proportion to resistance.

Parallel circuit: 1/R_total = 1/R1 + 1/R2 + …; voltage is the same across each branch; branch currents add.

Conductor resistance: R = K × L / CM (K = 12.9 Ω·cmil/ft for copper, 21.2 for aluminum); CM = mils² for solid, sum of strand CM for stranded.

Voltage drop, single phase: VD = 2 × K × I × L / CM. Three phase: VD = √3 × K × I × L / CM.

A 1 hp motor = 746 W output. Efficiency η = output watts / input watts, so input current = 746 × hp / (E × η × PF).

Temperature coefficient: resistance rises with temperature for copper and aluminum; ampacities are corrected using the ambient-temperature correction factors in the ampacity tables.

NM-B cable may be used in one- and two-family dwellings and normally dry locations; it must be protected where subject to physical damage and cannot be embedded in masonry or poured concrete.

AC (armored) cable and MC (metal-clad) cable both use a metallic armor; MC cable with a combined insulated grounding conductor is permitted in more locations, and fittings must be listed for the cable type.

EMT must be supported within 3 ft of each box and at intervals not exceeding 10 ft; IMC and RMC support intervals are also 10 ft.

Rigid metal conduit installed in concrete or in direct contact with the earth requires corrosion protection; PVC Schedule 80 is used where subject to physical damage.

Liquidtight flexible metal conduit is limited to 6 ft between a box or fitting and the equipment it supplies unless the circuit is protected per the tap rules.

Type UF cable is suitable for direct burial but must be buried at the depths in the burial table, and it requires supplemental protection where emerging from the ground.

Expansion fittings are required where raceways cross building expansion joints and where PVC is exposed to large temperature swings.

Boxes, conduit bodies, and fittings must be accessible; junction splices cannot be buried in walls or ceilings without an accessible cover.

The service grounding electrode system must be bonded together; if a metal underground water pipe is used it must be supplemented by another electrode such as a ground rod, concrete-encased electrode, or ground ring.

The grounding electrode conductor to a rod, pipe, or plate electrode is not required to be larger than 6 AWG copper or 4 AWG aluminum.

Equipment grounding conductors must be sized from the EGC table based on the rating of the overcurrent device protecting the circuit, not the conductor ampacity alone.

Bonding jumpers around water meters, gas piping, and removable sections of the grounding electrode conductor must be sized per the bonding jumper table and be of an approved material.

Separately derived systems require a system bonding jumper and a grounding electrode conductor connected to a grounding electrode at the source.

A main bonding jumper must be installed at the service disconnect and must be sized per the service conductor table; it is the connection between the grounded conductor and the equipment grounding conductor.

Receptacles must be grounded; where an EGC is not available, replacement receptacles may be GFCI protected and marked 'no equipment ground' only under the specific conditions of the Code.

Bonding of metal water piping and structural steel is required; the bonding conductor is sized per the bonding jumper table and must be accessible.

Standard OCPD ratings include 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400 A.

The next-higher-standard-size rule applies only where the ampacity of the conductor does not correspond to a standard rating and the next higher rating does not exceed 800 A.

Fuses and circuit breakers must be sized to protect conductors; the continuous-load rule requires the OCPD to be at least 125% of continuous load plus 100% of noncontinuous load.

Series-rated systems require the downstream OCPD to be listed and marked for use with the specific upstream device; the combination rating is the equipment short-circuit current rating.

The available fault current at the service must not exceed the interrupting rating of the service equipment; the calculated fault current must be documented and available to the inspector.

A circuit breaker used as a switch must be marked SWD or HID for the application; general-use breakers are not listed for switching duty.

Motor branch-circuit short-circuit and ground-fault protection is sized from the motor tables using percentages of full-load current, not from the conductor ampacity.

Supplementary protectors are not branch-circuit protective devices and cannot replace a branch breaker unless listed and marked for the purpose.

Standard 120 V receptacle branch circuits: 15 A or 20 A; a 20 A circuit may supply multiple outlets, and the receptacle rating must not be less than the branch-circuit rating.

Small-appliance branch circuits in a dwelling: at least two 20 A circuits for the kitchen, and these may not supply lighting outlets.

Laundry branch circuit: at least one 20 A circuit for the laundry area; it may not supply other outlets.

General lighting load for a dwelling: 3 VA per square foot; demand factors are applied to the general lighting load above 3,000 VA.

Service calculation steps: compute general lighting, small appliance, laundry, and fixed appliance loads; apply demand factors; add the largest motor at 25%; size the service and feeder conductors from the resulting load.

Feeder and service conductor sizing uses the ampacity tables, and the neutral load is calculated separately with the demand factors permitted for unbalanced loads.

Voltage drop is not a Code requirement but is recommended to be limited to 3% on branch circuits and 5% total; larger conductors may be required for long runs.

Receptacle outlet spacing in dwelling units: no point along the floor line may be more than 6 ft from a receptacle, and any wall space 2 ft or wider requires a receptacle.

Motor full-load current comes from the motor tables based on horsepower and voltage; nameplate current is used for overload protection, table current for conductor and short-circuit protection.

Motor branch-circuit conductors must have an ampacity of at least 125% of the motor full-load current from the table.

The motor disconnecting means must be within sight of the motor and controller and must be capable of being locked open; the disconnect rating must be at least 115% of the motor full-load current.

Overload protection is sized from the motor nameplate current; the overload device protects the motor from overload, while the branch-circuit breaker protects the conductors from short circuits.

A motor controller must be capable of starting and stopping the motor and must be rated for the horsepower and voltage; the controller must be located within sight of the motor unless the disconnect is lockable.

HVAC equipment requires a disconnecting means within sight; the nameplate minimum circuit ampacity (MCA) and maximum overcurrent protection (MOP) govern the conductor and breaker sizing.

Motor control circuits are classified as Class 1 or Class 2; Class 2 circuits are limited in power and must be separated from power conductors per the Code.

The motor overload relay must be selected so the motor is protected against overload but not tripped during normal starting; the Code permits a range of overload sizes and requires the manufacturer's instructions to be followed.

Transformer primary and secondary conductor protection: the primary OCPD is sized per the transformer table (typically 125% of primary current) and the secondary per the secondary table (typically 125% of secondary current).

The transformer secondary conductors must be protected by an OCPD; the secondary OCPD may be located at the transformer or at the first panelboard if the conductors are protected per the tap rules.

A transformer must be grounded per the system grounding requirements; a separately derived system requires a system bonding jumper and a grounding electrode conductor.

Transformers installed indoors must have adequate ventilation and clearances; dry-type transformers require working space per the Code.

Hazardous (classified) locations are classified by Class, Division, and Group; equipment must be listed and marked for the specific class, division, and group.

In Class I locations, wiring methods include threaded rigid metal conduit, IMC, and Type MC cable with listed fittings; seals are required at boundaries and within specified distances.

Bathroom, kitchen, and outdoor receptacles require GFCI protection; the specific distances and exceptions are given in the Code article for each location.

Swimming pool and spa installations require equipotential bonding of metal parts, and the bonding conductor must be sized per the pool bonding table.

Box fill is calculated from the volume of the box in cubic inches; each conductor counts based on its size, and the box fill table gives the volume allowance per conductor.

Conductors that originate outside the box and pass through without splice or termination count as one conductor; grounding conductors count as one conductor based on the largest EGC.

Raceway fill: the sum of the cross-sectional areas of all conductors must not exceed 40% of the raceway internal area for three or more conductors.

Conduit bending: the minimum radius and the number of bends between pull points (not more than 360° total) are specified in the Code; bends must not damage conductors.

Conductor ampacity is adjusted for ambient temperature and for the number of current-carrying conductors in a raceway or cable; the adjustment factors are applied to the table ampacity.

Cable trays, wireways, and gutters have their own fill rules; the fill percentage and the ampacity adjustment depend on the number of conductors and the installation method.

Boxes must be of sufficient size to accommodate all conductors, devices, and fittings; the minimum box size is determined by the box fill calculation, not by the number of devices alone.

Support of raceways and cables is required at intervals and within specified distances of boxes; the support distances vary by wiring method and are given in the Code tables.

Nebraska electrical licensing is administered by the State Electrical Division; the State Electrical Board adopts and enforces the electrical code and licensing rules.

The Nebraska Electrical Code is based on the National Electrical Code (NFPA 70) as adopted by the State Electrical Board, with Nebraska amendments.

Licensing categories include Journeyman Electrician, Master Electrician, and Contractor; each has specific experience and examination requirements.

A journeyman electrician must work under the supervision of a licensed master electrician or contractor; a contractor license is required to engage in the business of electrical contracting.

Continuing education is required for license renewal; the number of hours and the approved topics are set by the State Electrical Board.

Permits and inspections are required for electrical work; the local authority having jurisdiction may have additional requirements beyond the state code.

Violations of the electrical statutes and rules may result in license suspension, revocation, or civil penalties; the Board has authority to investigate complaints and hold hearings.

License reciprocity and examination requirements are governed by state statute and Board rules; candidates should verify current requirements with the State Electrical Division.