Licensed Electrical Inspector (LEI) G Class Theory common mistakes
Licensed Electrical Inspector (LEI) G Class Theory · Understand the traps and how to avoid them.
Computing ampacity, voltage drop, or conduit fill from memory and writing the number straight onto the answer sheet without opening the applicable table or formula in the provided reference material.
Candidates who have done field work for years trust rule-of-thumb values (for example, treating 12 AWG as always good for 20 A) and underestimate how often exam items hinge on a specific table row, ambient-temperature correction, or conductor-count adjustment factor that changes the answer.
What to do instead
Before the exam, drill a fixed lookup routine: identify the conductor material, insulation type, terminal rating, ambient temperature, and number of current-carrying conductors, then read each value from the table in sequence. Practice 20 calculation items with the reference open every time so the lookup becomes automatic rather than optional.
Solving series-parallel combination circuits by collapsing the whole network in one mental step, then reporting a single current or voltage for the entire circuit instead of per-branch values.
Classroom problems often use simple series strings, so candidates never build the habit of redrawing the circuit and reducing it in stages; under time pressure they jump to a total and misassign branch currents.
What to do instead
Redraw the circuit on scratch paper, label every node, and reduce one series or parallel group at a time, writing the intermediate equivalent resistance. Then work backward from the source to find branch currents and voltage drops, checking that branch currents sum to the total at each node and that voltage drops around each loop sum to the source voltage.
Applying a wiring-method rule without first classifying the location and construction, for example citing a general cable-installation allowance where the item describes a hazardous location, a wet location, or a plenum.
The code text for general installations is familiar and gets recalled first, while the location-specific article is longer and less frequently used in daily work; candidates answer the rule they know rather than the rule that governs the described condition.
What to do instead
Read each stem and explicitly write down the occupancy, location classification, and wiring method before selecting an answer. Build a one-page matrix of permitted wiring methods by location type and review it until the classification step happens before any code citation.
Confusing the grounding electrode conductor, the equipment grounding conductor, and the main bonding jumper, and sizing or terminating one as if it were another.
All three are green or bare conductors associated with grounding, and field terminology blurs them; candidates memorize a single size table without tying each conductor to its function and its termination point.
What to do instead
Draw a service diagram showing the grounding electrode conductor from the neutral point to the electrode, the main bonding jumper between neutral and equipment ground at the service, and the equipment grounding conductor running with each branch circuit. Label the sizing basis for each and practice sizing all three for the same service until the distinctions are automatic.
Selecting an overcurrent device from the calculated load current alone, skipping the checks for conductor ampacity after adjustment, terminal temperature limitations, and the permitted next-standard-size rule.
The load calculation feels like the hard part, so candidates stop there; the layered constraints of adjusted ampacity, termination rating, and rounding rules are where most items actually discriminate.
What to do instead
Adopt a fixed four-step sequence for every overcurrent item: calculate load, determine adjusted and corrected conductor ampacity, apply the terminal limitation, then apply the next-standard-size allowance only where it is permitted. Write the four steps on scratch paper and fill each one in before choosing an answer.
Answering permit and inspection-process items from local habit rather than from the administrative provisions described in the stem, such as who may request an inspection or when a permit expires.
Candidates with field experience have absorbed one jurisdiction's practice and assume it is universal; administrative items feel like common sense and receive no study time.
What to do instead
Study the administrative chapter as a distinct topic: permit issuance, fees, expiration and renewal, inspection requests, stop-work authority, and certificate of occupancy. For each item, locate the exact provision in the reference before answering, and treat any answer justified only by 'that is how we do it back home' as a warning sign.
Performing a plan review or describing an inspection sequence without a documented checklist, so items about what must be verified before concealment or before energization are answered from vague recollection.
Inspectors in training often observe inspections rather than lead them, so the ordered stages of rough-in, concealment, and final are not firmly internalized, and documentation requirements are treated as paperwork rather than procedure.
What to do instead
Write out the inspection sequence for a typical residential and a typical commercial project from memory, then compare against the reference and correct gaps. Practice stating, for each stage, what must be visible, what must be tested, and what record must exist before the next stage is approved.
Treating shock protection as a single concept and answering arc-flash or approach-boundary items with the same reasoning, or overlooking lockout and verification steps in a described work procedure.
Both hazards involve electricity, so candidates conflate them; shock protection concerns boundary distances and insulation, while arc flash concerns incident energy, clothing, and equipment labeling, and mixing them produces plausible but wrong answers.
What to do instead
Build two separate study sheets, one for shock protection and one for arc-flash protection, listing the governing quantity, the protective measures, and the labeling requirements for each. For procedure items, verify that de-energization, lockout, test for absence of voltage, and temporary grounding appear in the correct order.
Applying general-location wiring and equipment rules to special occupancies and systems such as health care facilities, places of assembly, motor installations, or emergency power, without invoking the special article.
These occupancies are encountered less often, and the general rules still appear to fit; candidates do not recognize the trigger words in the stem that signal a special article applies.
What to do instead
Create a trigger-word list for each special occupancy and system and rehearse it, for example patient care area, critical branch, assembly occupancy with fixed seating, motor branch circuit, and classified location. When a trigger appears, go directly to the special article and confirm that its requirements override the general rule.
Answering ethics and liability items by choosing the option that protects the inspector or the contractor rather than the option that follows the stated duty, such as approving work under pressure or accepting a gift that creates a conflict.
These items have no calculation to anchor them, and candidates reason about consequences, reputation, or workplace harmony instead of the professional obligation described in the stem.
What to do instead
Study the duty framework explicitly: independence, disclosure of conflicts, accurate reporting, confidentiality, and refusal to certify work not personally verified. For each ethics item, identify the specific duty at stake and choose the response that satisfies it even when that response is uncomfortable or costly.