What these problems are based on
Every problem is generated by this site's own calculators from the published tables they already use. No question is taken from an exam, a code book or a prep book, and no code text is quoted.
Worked to the 2023 edition as used by this site's calculators; your exam may use another edition. The 2026 edition renumbered some articles, so check any number against the edition your exam uses.
Assumptions
- Voltage drop only: the ampacity check is separate, and on these runs it needs a smaller conductor.
- Circular-mil method with the one-way length; reactance and power factor are ignored.
- Upsizing for voltage drop would also upsize the equipment grounding conductor in proportion; that step is not asked here.
Rounding and grading
- Factors are decimals to two places (0.82). A factor typed as a percent (82%) is read as 0.82.
- Amperes are rounded to one decimal place, volts and percents to two, areas to four (square inches).
- Table lookups and choices must match exactly. Calculated lines are accepted within the tolerance shown beside them, the same amount above or below the key.
Exam practice only. AmpSizer is not affiliated with, endorsed by or connected to any code publisher, testing company or licensing board. A real installation is sized by a licensed electrician to the locally adopted code.