NE Journeyman Electrician common mistakes
NE Journeyman Electrician · Understand the traps and how to avoid them.
Sizing the service or feeder by adding up connected loads and selecting a conductor from the ampacity table without applying the Article 220 demand factors, then checking the result against a standard service size.
Candidates memorize ampacity tables and treat the calculation as a lookup exercise, so they skip the optional versus standard method decision, the 220.42 lighting demand factors, and the 220.55 range/dryer provisions. The arithmetic feels finished before the demand step is reached.
What to do instead
Work every service calculation on a fixed worksheet: general lighting VA by occupancy, small appliance and laundry circuits, then apply Table 220.42 demand factors, then add the largest motor at 25 percent, ranges and dryers by Table 220.55, and HVAC at 100 percent of the larger of heating or cooling. Do ten practice calculations end to end and compare against the standard service sizes in 240.6.
Choosing a conductor from the 60°C column because the insulation is THHN/THWN-2, ignoring that the termination temperature rating limits the usable ampacity.
The 90°C column shows a bigger number, so candidates grab it without checking 110.14(C) and the equipment listing. They also forget the separate rule that NM cable ampacity is limited to the 60°C column per 334.80.
What to do instead
Before selecting any conductor, identify the termination rating of the breaker and the equipment, apply the lowest of the termination and insulation ratings, then apply any adjustment or correction factors on top. Practice problems where the answer changes depending on whether the load is a 75°C lug or a 60°C assembly.
Applying Table 310.15(B)(3)(a) adjustment factors to a raceway or cable without first counting current-carrying conductors correctly, including neutrals of nonlinear loads and the spare conductor rules.
Candidates count every wire in the raceway and then still apply the factor, or they count only hots and miss the neutral that carries harmonic current. The interaction between derating and 240.4(D) small-conductor limits is also frequently missed.
What to do instead
Count current-carrying conductors per 310.15(B)(5) and (6): grounded conductors of multiwire branch circuits and balanced wye systems do not count, but neutrals of nonlinear loads do. Then apply the table factor, and remember 240.4(D) caps 14, 12, and 10 AWG regardless of derated ampacity unless a specific exception applies.
Treating equipment grounding conductor sizing as a single table lookup without matching it to the overcurrent device rating and the conductor size actually installed.
Candidates memorize 250.122 as a fixed rule and forget that the EGC is sized to the OCPD, not the phase conductor, and that 250.122(B) requires proportional upsizing when the phase conductors are increased for voltage drop.
What to do instead
For each problem, write down the OCPD rating, look up Table 250.122, then check whether the ungrounded conductors were upsized for any reason. If so, apply the proportional increase in 250.122(B). Also confirm the EGC material and the 250.118 permitted types before finalizing.
Sizing a box by counting only the current-carrying conductors and ignoring devices, clamps, support fittings, and equipment grounding conductors in the volume calculation.
The box fill tables look like simple wire counts, so candidates tally hots and neutrals and stop. They miss that each yoke counts as two conductors, that EGCs are counted as one or more based on the largest, and that 314.16(B)(1) counts clamps and fittings.
What to do instead
Use a five-line tally: conductors by size, EGCs as one entry based on the largest, devices at two per yoke, clamps and support fittings, and any equipment grounding conductor or isolated ground contributions. Compare the total to Table 314.16(A) or the marked volume, and confirm the minimum box size before moving on.
Selecting a branch-circuit overcurrent device at the conductor ampacity instead of at the load's listed maximum protection, particularly for HVAC and motor circuits.
The general 240.4 rule dominates study time, so candidates apply it uniformly and miss that 440.22 permits or requires protection at the nameplate marked maximum, and that 430.52 allows the next standard size up for motor short-circuit protection.
What to do instead
For HVAC equipment, read the nameplate minimum circuit ampacity and maximum overcurrent protection and size the conductor to the MCA and the breaker to the MCA or marked maximum per 440.22. For motors, apply Table 430.52, then 430.52(C)(1) Exception 1 for the next standard size, and keep the overload sizing separate.
Sizing motor overload protection using the branch-circuit short-circuit device table, or vice versa, so the two protections are confused.
Both use tables with percentages and both are called 'protection.' Candidates memorize one percentage set and apply it to whichever device appears in the question.
What to do instead
Separate the two in every problem: branch-circuit short-circuit and ground-fault protection comes from Table 430.52 based on full-load current, while overload protection comes from 430.32 based on the nameplate service factor or temperature rise. Write both on the scratch paper before answering.
Ignoring the Nebraska licensing and statute layer, answering electrical code questions correctly but missing questions about license classes, continuing education, or the board's authority.
Candidates spend all study time in the NEC and treat state law as common sense. The Nebraska Electrical Division rules on licensure, apprentice ratios, and permit requirements are specific and are tested directly.
What to do instead
Build a one-page summary of the Nebraska statutes and rules: license classifications, renewal and continuing education hours, permit and inspection requirements, and the Board's disciplinary authority. Review it in the last week, and note which questions are code versus statute so you do not apply code logic to a legal question.
Applying the general 80 percent or 125 percent rule to every load instead of identifying which loads are continuous, which are the largest motor, and which are already covered by a specific article.
The 125 percent continuous-load rule in 210.19 and 215.2 gets over-applied to receptacles, dryers, and ranges that already have their own demand provisions, inflating answers and causing second-guessing.
What to do instead
Classify each load first: continuous or noncontinuous, then whether Article 220 or a specific article governs it. Apply 125 percent only to continuous loads and to the largest motor per 430.24, and do not stack it on loads already covered by Table 220.55 or 220.54.
Sizing transformers and their overcurrent protection from the kVA rating without distinguishing primary and secondary protection rules and the 125 percent / 250 percent allowances.
Candidates treat transformer protection as one calculation and miss 450.3's separate primary and secondary tables, the conditions for primary-only protection, and the inrush allowance that lets the primary device be larger.
What to do instead
For each transformer problem, state the kVA, the primary and secondary voltages, and the resulting full-load currents. Then apply Table 450.3(A) or (B) depending on the voltage class, check whether secondary protection is required, and verify the primary device against the next standard size in 240.6.