GER Licensed Electrical Inspector 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 for the full relationship.

Series circuit: current is common, resistances add (R_T = R1 + R2 + ...), and voltage divides in proportion to resistance.

Parallel circuit: voltage is common, conductances add (1/R_T = 1/R1 + 1/R2 + ...), and current divides inversely with resistance.

Effective (RMS) AC voltage of a sine wave = peak ÷ √2; average voltage of a full-wave rectified sine = 0.637 × peak.

Three-phase power: P = √3 × E_line × I_line × power factor for a balanced load; single-phase P = E × I × PF.

Conductor resistance rises with temperature for copper and aluminum; ampacity tables assume an ambient of 30°C (86°F) for conductors and 40°C for some equipment ratings.

Power factor = true power (watts) ÷ apparent power (volt-amperes); a lagging power factor indicates inductive load such as motors.

Skin effect and proximity effect increase AC resistance at higher frequencies and in large conductors, which is why large sizes are paralleled.

Conductors in parallel must be 1/0 AWG or larger, of the same material, same length, same insulation type, and terminated alike; each raceway may contain only one set unless otherwise permitted.

NM-B cable is limited to normally dry locations and must be protected where passing through framing; it cannot be installed in wet locations or embedded in masonry.

RMC and IMC require threaded connections or listed fittings; PVC conduit requires expansion fittings where thermal expansion exceeds 1/4 in. per 100 ft of run.

Box fill is calculated by counting each conductor, each yoke device, each clamp, and equipment grounding conductors, then comparing to the box's marked volume in cubic inches.

Support intervals: NM cable every 4.5 ft and within 12 in. of boxes; RMC/IMC every 10 ft; EMT every 10 ft with a maximum of 5 ft between a coupling and a box.

Conductor ampacity is adjusted for ambient temperature and for more than three current-carrying conductors in a raceway or cable, per the adjustment tables.

Minimum burial depth for direct-buried cable is typically 24 in.; for rigid metal conduit it is 6 in. under a building or 18 in. elsewhere, per the applicable table.

Continuous loads are calculated at 125% of the load for branch-circuit and feeder sizing; noncontinuous loads at 100%.

Standard general lighting load for dwellings is 3 VA per square foot; small-appliance branch circuits are 1,500 VA each and laundry is 1,500 VA.

Dwelling service demand factors: first 3,000 VA at 100%, then 35% of the remainder from 3,001 to 120,000 VA, then 25% above 120,000 VA.

A 20 A small-appliance branch circuit may supply receptacles in kitchen, dining, pantry, and similar areas; at least two such circuits are required in a dwelling.

Receptacle spacing in dwelling habitable rooms: no point along the floor line is more than 6 ft from a receptacle, and any wall space 2 ft or wider needs one.

Feeder and service neutral load is the maximum unbalanced load; it may be reduced to 70% of the load exceeding 200 A for dwellings, with restrictions on nonlinear loads.

Voltage drop is not a code-mandated limit but a recommended practice: keep branch circuits under 3% and the total feeder plus branch under 5%.

The service neutral (grounded conductor) is bonded to the equipment grounding system only at the service disconnecting means; downstream panels use separate neutral and ground bars.

Standard overcurrent device ratings: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100 A, then in 50 A increments above 100 A.

The next-higher standard rating may be used where the conductor ampacity does not correspond to a standard rating, provided the load does not exceed the conductor ampacity.

Equipment grounding conductor sizing follows the table keyed to the rating of the overcurrent device protecting the circuit, not to the phase conductor size alone.

Grounding electrode conductor sizing is based on the largest ungrounded service conductor; bonding jumpers around water meters and at fittings must be sized accordingly.

GFCI protection is required for dwelling bathroom receptacles, kitchen countertop receptacles, garages, outdoors, and unfinished basements.

AFCI protection is required for most 120 V branch circuits in dwelling living areas, including bedrooms, and must be listed for the circuit.

A grounded conductor may not be used as an equipment grounding conductor on the load side of the service disconnecting means.

A typical inspection sequence is rough-in (before cover), then final; concealed work cannot be approved after it is covered without verification.

The inspection record should identify the permit number, the code edition adopted, the circuits or equipment inspected, and the result as approved, approved with corrections, or rejected.

Correction notices should cite the specific code section, the location, and the corrective action required, so the contractor can respond without ambiguity.

Continuity and polarity tests verify grounding conductor continuity, correct neutral-to-ground separation, and that the grounded conductor is not switched.

Insulation resistance testing with a megohmmeter is a diagnostic tool; results below 1 megohm per 1,000 V of test voltage warrant investigation.

Field-testing records should note the instrument, its calibration date, the test method, and the readings, because the record may be needed if a dispute arises.

A reinspection should confirm each cited correction was completed; new deficiencies observed during reinspection should be documented as separate items.

Plan review verifies service and feeder calculations, conductor and overcurrent sizing, grounding, and working clearances before construction begins.

The adopted code edition and any local amendments govern; where editions conflict, the locally adopted version controls the permit.

Working clearance in front of electrical equipment is at least 36 in. deep, 30 in. wide, and 6 ft 6 in. high, with the depth increased for higher voltages.

A dedicated equipment space above and in front of switchboards and panelboards must be kept clear of piping, ducts, and foreign systems.

Service disconnecting means must be installed at a readily accessible location nearest the point of entry of the service conductors, with the number of disconnects limited.

Plan review should confirm that the available fault current does not exceed the interrupting rating of the overcurrent devices installed.

Where a code requirement is ambiguous, a written interpretation should be issued and retained so enforcement is consistent across inspectors.

Class I locations involve flammable gases or vapors; Class II involves combustible dust; Class III involves ignitable fibers or flyings.

Divisions: Division 1 is where the hazard exists under normal conditions; Division 2 is where it exists only under abnormal conditions.

Zones 0, 1, and 2 correspond to Class I continuous, intermittent, and abnormal presence of gas; Zones 20, 21, and 22 correspond to dust.

Equipment in hazardous locations must be marked with its class, division or zone, and group; the marking must match the area classification.

Seals are required in conduit systems entering hazardous locations to prevent the passage of gases or vapors, and at specified distances from the enclosure.

Bathroom and wet-location receptacles require GFCI protection; swimming pool equipment requires equipotential bonding of metal parts and the water.

Health care facility critical branch circuits must be kept separate from other circuits and must not be connected to the general care branch.

The inspector's authority derives from the adopted code and local ordinance; the inspector does not design the installation or direct the contractor's means and methods.

Approval of a portion of an installation does not relieve the installer of responsibility for code compliance of the entire installation.

An inspector should disclose any financial interest in the work being inspected and should decline the assignment where a conflict exists.

Inspection findings should be factual and specific; opinions about the contractor's competence belong in a separate record, not in the correction notice.

Personal protective equipment for electrical inspection includes arc-rated clothing and face protection when working near energized equipment.

Liability exposure is reduced by documenting the code basis for each decision and by retaining inspection records for the period required by the jurisdiction.

An inspector must not accept gifts or favors that could reasonably influence an enforcement decision.