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2. Know the conductor names
2020 NEC · Article 100 · 15 min
Compare neutral, grounded and equipment grounding conductors. These terms are not interchangeable. A voltage reading alone cannot show the percentage of a failed neutral; this clip is not an energized-testing procedure.
Try it in your codebook: Compare Neutral Conductor and Equipment Grounding Conductor in Article 100. Which is intended to carry normal load current?
Check your answer
The neutral conductor. The equipment grounding conductor connects normally non-current-carrying metal parts as part of the fault-current path.
3. Check terminal ratings
2020 NEC · 110.14(C) · 10 min
Check conductor insulation and equipment markings separately. A 90°C wire rating does not make a terminal 90°C or remove required ampacity adjustments.
Try it in your codebook: With 90°C wire and equipment listed and marked for 75°C terminations at both ends, can 90°C ampacity be the final termination limit?
Check your answer
No. The termination limit is based on 75°C ampacity. The 90°C rating may be used for permitted adjustments or corrections; the result must still meet the termination limit and other applicable rules.
4. Trace the ground-fault path
2020 NEC · 250.4(A)(5) · 15 min
Read 250.4(A)(5) with the opening of this lesson. A low-impedance path back to the source helps the protective device operate. It does not dispose of unused current.
Try it in your codebook: Under 250.4(A)(5), can earth serve as the effective ground-fault current path?
Check your answer
No. The path must return fault current to the electrical supply source and help the overcurrent device—or ground detector on an impedance-grounded system—operate.
5. Read the grounding tables
2020 NEC · 250.122 and 250.102(C)(1) · 19 min
Choose the table for the conductor: 250.122 uses the overcurrent-device rating; 250.102(C)(1) uses supply-conductor size. Check the row limit and copper or aluminum column.
Try it in your codebook: Using Table 250.122 only, what is the minimum copper equipment grounding conductor for a 60A overcurrent device?
Check your answer
10 AWG copper. That is the table minimum; other applicable rules or installation conditions may require a larger conductor.
6. Protect wiring in framing
2020 NEC · 300.4(A)(1) · 10 min
Find the wiring-protection rule in 300.4(A)(1). Structural drilling limits are a separate check; there is no universal 30% limit for every wood member.
Try it in your codebook: In 300.4(A)(1), what clearance is measured from the edge of a bored hole to the nearest edge of the wood member?
Check your answer
At least 1¼ inches (32 mm). If that clearance cannot be maintained, apply the protection requirements and exceptions in the same subsection. Structural drilling limits still apply.