MT Journeyman Electrician common mistakes
MT Journeyman Electrician · Understand the traps and how to avoid them.
Calculating box fill by counting only the current-carrying conductors and ignoring clamps, support fittings, receptacles, and equipment grounding conductors, then selecting a box that is actually undersized.
Candidates memorize 'one count per conductor' and forget that each yoke or strap counts as two conductors based on the largest conductor attached, that internal cable clamps count as one, and that all EGCs together count as one. They also skip the volume allowance table and guess at cubic inches per conductor size.
What to do instead
Build a written tally every time: conductors by size, plus one for clamps, plus two per yoke, plus one for all EGCs, then multiply by the table volume for the largest conductor size and compare to the marked box volume. Practice ten mixed boxes with cable clamps and duplex receptacles until the tally is automatic.
Sizing branch-circuit and feeder conductors from the connected load instead of the calculated load, and failing to apply the continuous-load 125 percent factor to the non-motor portions of a feeder or service.
Candidates treat the nameplate sum as the answer, or apply the 125 percent multiplier to the entire feeder including the largest motor, double-counting. They also confuse the 125 percent continuous-load rule with the 125 percent largest-motor adder.
What to do instead
Work a fixed sequence: general lighting and receptacles, then appliance loads with demand factors, then the largest motor at 125 percent, then add the continuous non-motor load at 125 percent. Write the sequence on scratch paper before touching the calculator and check each line against the applicable article.
Choosing an overcurrent device from the conductor ampacity alone without checking the motor branch-circuit short-circuit and ground-fault protection rules, then tripping on startup or failing the question when the answer key uses the table maximum.
Candidates apply the general ampacity rule to motor circuits, where overload protection and short-circuit protection are separate devices with separate sizing rules. They also forget that the table value may be increased when starting current causes nuisance tripping.
What to do instead
Separate the two protections explicitly: overload sized to the nameplate current, short-circuit and ground-fault protection sized from the motor branch-circuit table with the permitted increase noted. Practice reading a motor nameplate and producing both numbers plus the conductor and disconnect sizing in one pass.
Confusing grounding and bonding, treating the equipment grounding conductor and the grounded conductor as interchangeable, and bonding the neutral at a subpanel.
The two words sound similar and both involve green or white wires, and residential experience with a combined service panel reinforces the habit of landing neutrals and grounds on the same bar everywhere.
What to do instead
State the function aloud before answering: the grounded conductor carries current, the equipment grounding conductor carries fault current and no normal current, and the main bonding jumper exists only at the service or separately derived source. For every question, ask where the system bonding point is before deciding where a conductor lands.
Applying ampacity tables without the adjustment and correction steps, using the 60-degree column by default, or ignoring termination temperature limitations.
Candidates grab the first ampacity number they see, forget that ambient temperature correction and conductor-count adjustment both apply, and do not check that the selected ampacity does not exceed the termination rating of the device or equipment.
What to do instead
Use a fixed three-step routine: base ampacity from the correct table and column, apply correction and adjustment factors, then cap the result at the termination temperature limit. Do five problems that require all three steps so the cap is never forgotten.
Answering Montana licensing and statute questions from general trade knowledge rather than from the specific administrative rules, and assuming reciprocity or license categories work the way they do in a neighboring state.
Most study time goes to the code book, so candidates never read the state statutes and rules that define license classes, continuing education, renewal, supervision ratios, and enforcement. They then guess using out-of-state assumptions.
What to do instead
Read the Montana electrical statutes and the board's administrative rules directly, and build a one-page summary of license categories, renewal and continuing education requirements, supervision and permitting rules, and grounds for discipline. Rehearse the summary until the numbers and definitions are exact.
Treating NFPA 70E as a general safety appendix and answering arc-flash questions from instinct instead of using the incident energy analysis, the arc-flash boundary, and the PPE category tables.
Candidates have field habits that feel safe but do not match the standard's defined terms, and they confuse approach boundaries with the arc-flash boundary or assume PPE categories apply without an incident energy analysis.
What to do instead
Learn the defined terms as a set: shock approach boundaries, arc-flash boundary, incident energy, and PPE category. Practice reading a sample label and stating the required PPE, then compare against the tables in the standard so the difference between table-based and analysis-based selection is clear.
Missing the extra requirements for special occupancies and locations, applying the general wiring method in a hazardous classified area, a commercial garage, a health care facility, or around a pool, spa, or hot tub.
The general chapters are studied first and most thoroughly, so candidates default to them and never check whether the location triggers a modifying article. They also misclassify the location itself.
What to do instead
Before answering any installation question, name the occupancy or location out loud and ask whether a special article applies. Build a location-to-article index covering hazardous classified locations, health care facilities, assembly occupancies, agricultural buildings, pools and spas, and similar special areas, and review it weekly.
Sizing conduit and raceway fill from conductor count alone, ignoring insulation type, conductor size, and the permitted fill percentages for different raceway types and lengths.
Candidates count wires and divide by a remembered fraction, forgetting that compact and non-compact conductors, THHN versus XHHW dimensions, and the nipple and short-run exceptions change the answer.
What to do instead
Always use the raceway fill tables and the conductor dimension tables together, identify the exact insulation and size first, then apply the correct fill percentage for the raceway type and run length. Practice a mixed pull with different insulation types in the same raceway.
Reading the question's units and conditions too quickly, answering the question that was expected rather than the one asked, and failing to notice qualifiers such as 'minimum', 'not required', or 'within sight'.
Exam pressure and familiarity with the topic cause candidates to pattern-match to a remembered problem, and negative or exception-based questions are the ones most often misread.
What to do instead
Slow down at the end of each question, underline the qualifier and the unit, and restate the question in your own words before choosing. Flag and return to any question containing 'not', 'except', or 'minimum' rather than answering it on the first pass.