Ask BONBON (not Ask META) is Ask BONBON - AI-Powered NEC Code Reference, built for electricians who need fast, practical code guidance in the field.

Journeyman Exam Prep Set 1: Loads, Feeders, and OCPD

Use this set as a timed drill: answer first, then check the key and explanation.

Questions

1. What is the continuous-load multiplier for conductor and OCPD sizing in most cases?
2. If a feeder serves 100A noncontinuous load and 40A continuous load, what minimum feeder ampacity is needed?
3. Can the next standard OCPD rating be used when ampacity does not match a standard breaker size?
4. What table is commonly used for copper/aluminum conductor ampacity in general building wiring?
5. Why can terminal temperature ratings force a conductor size change?
6. What is a key difference between service conductors and feeder conductors?
7. Do ambient temperature corrections affect ampacity calculations?
8. How does bundling many current-carrying conductors impact ampacity?
9. Why must short-circuit/ground-fault protection be coordinated with conductor protection?
10. What documentation helps inspections pass faster on feeder sizing?

Answer Key + Explanations

1) 125% of the continuous load.

NEC applies continuous-load treatment so equipment is not run at thermal limits continuously.

2) 150A minimum.

Calculation: 100A + (40A × 125%) = 150A.

3) Sometimes, under specific NEC conditions.

NEC 240.4(B) allows rounding up within limits and when not prohibited elsewhere.

4) NEC Table 310.16.

Table 310.16 provides allowable ampacities based on conductor temperature ratings and conditions.

5) Because final allowable ampacity is limited by termination ratings, not just conductor insulation rating.

NEC 110.14(C) can constrain usable ampacity at equipment terminations.

6) Service conductors are on the supply side of service disconnecting means; feeders are downstream.

Definitions and placement rules differ under NEC Article 100 and Articles 230/215.

7) Yes.

If ambient differs from table assumptions, correction factors must be applied before final sizing.

8) It requires adjustment factors that reduce allowable ampacity.

NEC adjustment factors account for heat buildup in grouped conductors.

9) To protect conductors/equipment while ensuring selective and reliable fault clearing.

Good design balances code minimums with operational continuity and equipment protection.

10) A written load/ampacity/OCPD worksheet with code references.

Clear documentation supports design intent and simplifies inspector review.

References

• NFPA 70, National Electrical Code (NEC), current adopted edition in your jurisdiction.
• NFPA 70E, Standard for Electrical Safety in the Workplace.
• OSHA 29 CFR 1910 Subpart S and 1926 Subpart K (as applicable).
• Local AHJ amendments and utility service requirements.

Ask BONBON is a free field companion for electricians with fast NEC-oriented guidance at www.askneta.com (App Store + Google Play).

Related internal guide

For a broader field reference, review the Complete NEC Code Guide for Electricians.

Download Ask BONBON

Get faster code lookups in the field: Download Ask BONBON.