HI Electrician cheat sheet

Ohm's Law: V = I × R; power P = V × I = I²R = V²/R. For three-phase, P = √3 × V_LL × I × 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 all branches; current divides inversely with resistance.

AC impedance: Z = √(R² + (X_L − X_C)²); X_L = 2πfL, X_C = 1/(2πfC). Power factor = R/Z = cos θ.

Conductor resistance: R = ρL/A; for copper use K = 12.9 Ω·cmil/ft at 75°C (NEC Chapter 9 Table 8 values).

Voltage drop single-phase: VD = 2 × K × I × L / cmil; three-phase: VD = √3 × K × I × L / cmil.

Ampacity adjustment: ambient temperature correction and conduit fill adjustment factors multiply the table ampacity (NEC 310.15).

Box fill: count each current-carrying conductor once, each device yoke twice, each grounding conductor once, and each clamp or support once (NEC 314.16).

NEC Article 90 covers purpose and scope; Chapter 1–4 rules apply generally, Chapters 5–7 supplement or modify, Chapter 8 is independent, and Chapter 9 tables are mandatory when referenced.

Branch-circuit continuous loads must be sized at 125% of the continuous load plus 100% of noncontinuous load (NEC 210.19(A)).

Receptacle outlet spacing in dwelling units: no point along the floor line more than 6 ft from a receptacle, and any wall space 2 ft or wider needs one (NEC 210.52).

GFCI protection is required for 125V 15/20A receptacles in bathrooms, garages, outdoors, kitchens, laundry, and within 6 ft of sinks (NEC 210.8).

AFCI protection is required for 120V 15/20A branch circuits supplying outlets in dwelling unit bedrooms, living rooms, and similar areas (NEC 210.12).

Working space in front of electrical equipment: depth 3 ft for 0–150V to ground, 3.5 ft for 151–300V, 4 ft for 301–600V; width 30 in or equipment width, whichever is greater (NEC 110.26).

Overcurrent protection: standard ratings per NEC 240.6; next-higher-rated device may be used only when the conductor ampacity does not correspond to a standard rating and does not exceed 800A (NEC 240.4(B)).

Service disconnecting means must be installed at a readily accessible location nearest the point of entrance of service conductors, and the service disconnect must be marked with its rating (NEC 230.70, 230.79).

NM-B cable is permitted in dry, concealed, and exposed locations in dwellings but not in damp/wet locations, embedded in masonry, or as service-entrance cable (NEC 334.10, 334.12).

EMT support: within 3 ft of each box and every 10 ft thereafter; running threads are not permitted for support (NEC 358.30).

RMC support: within 3 ft of each box and every 10 ft; threaded couplings must be wrench-tight (NEC 344.30).

PVC Schedule 40 support: within 3 ft of each box and every 3 ft thereafter; expansion fittings are required where thermal expansion is expected (NEC 352.30, 352.44).

Boxes must be supported; a box may be supported by the raceway if the raceway is supported within 18 in of the box (NEC 314.23).

Conductor bending radius: for exposed conductors, not less than 4 times the overall diameter for sizes 1/0 and smaller, and 5 times for larger (NEC 300.34).

Cable and raceway entries into boxes require bushings or fittings listed for the purpose; conductors must be protected from abrasion (NEC 300.15, 300.17).

Underground feeder (UF) cable requires 24 in minimum cover for 120/240V residential branch circuits, and 18 in where GFCI-protected and 120V or less (NEC 300.5).

Motor branch-circuit conductor ampacity must be at least 125% of the motor full-load current from NEC Tables 430.248–430.250 (NEC 430.22).

Motor overload protection is sized per NEC 430.32; the overload device is intended to protect the motor, while the branch-circuit short-circuit and ground-fault device protects the circuit.

Motor disconnecting means must be within sight of the motor and controller, or capable of being locked open (NEC 430.102).

A controller must have a horsepower rating not less than the motor it controls (NEC 430.83).

Motor control circuits derived from the motor branch circuit are protected per NEC 430.72; control transformers require primary and secondary overcurrent protection.

For a wye-delta or part-winding starter, the branch-circuit short-circuit and ground-fault protection is sized from the motor nameplate current and NEC Table 430.52.

Special equipment: elevators per Article 620, cranes and hoists per Article 610, and air-conditioning equipment per Article 440 use nameplate-rated branch-circuit selection.

Arc welders are covered by Article 630; the supply conductors and overcurrent protection are based on the welder nameplate primary current and duty cycle.

Hawaii electrical licensing is administered by the Department of Commerce and Consumer Affairs (DCCA) through the Professional and Vocational Licensing Division (PVL).

Hawaii Revised Statutes Chapter 448E governs electricians and electrical contractors; it establishes license categories and the electrical examining board.

Hawaii Administrative Rules Title 16, Chapter 115 contains the rules for electricians and electrical contractors, including application, examination, and renewal requirements.

License categories include journey worker electrician, supervising electrician, and electrical contractor; each has distinct experience and examination requirements.

Continuing education and renewal cycles are set by the board and DCCA; licensees must track their own renewal dates and required hours.

Unlicensed electrical work is prohibited except for work exempt by statute, such as certain minor repairs or work by the owner on a single-family residence occupied by the owner.

Advertising and business practices are regulated; an electrical contractor must hold a valid contractor license and may be required to post a bond and maintain insurance.

Violations may result in fines, license suspension, or revocation; the board may also require restitution or additional education as a condition of reinstatement.

Lockout/tagout (LOTO) requires de-energizing, isolating, locking, tagging, and verifying absence of voltage before work on electrical equipment (OSHA 1910.147).

Personal protective equipment: use voltage-rated gloves with leather protectors, arc-rated clothing, and face shields matched to the incident energy level (NFPA 70E).

Approach boundaries: shock protection boundaries depend on voltage; the limited approach boundary for 120V is 10 ft for unqualified persons and 3 ft 6 in for qualified persons.

Grounding electrode system: a grounding electrode conductor connects the service neutral/grounded conductor to the grounding electrode; the neutral must not be bonded downstream of the service disconnect (NEC 250.24, 250.142).

Equipment grounding conductor sizing is based on the overcurrent device rating per NEC Table 250.122; it must be run with the circuit conductors and bonded to all metal enclosures.

Bonding jumpers around water meters and gas piping are required where continuity is interrupted; bonding to gas piping must be by a listed clamp and must not rely on the gas connector (NEC 250.104).

Test instruments: verify a voltmeter on a known live source before and after checking for absence of voltage (live-dead-live test).

Temporary power and GFCI protection: all 125V 15/20A receptacles on construction sites must have GFCI protection (NEC 590.6).