Code Hunter — Ampacity (2017 NEC)


To play this game, you need a sharp eye, a quick mind, and a 2017 National Electrical Code book.

(Fill-in-the-blank questions are looking for the exact words) used in the NEC).

1. For motors marked with design letters B, C, or D, conductors having an insulation rating of __________ or higher shall be permitted to be used, provided the ampacity of such conductors does not exceed the __________ ampacity.
2. The ampacity of the neutral conductor shall __________ the maximum net calculated load current between the neutral conductor and all ungrounded conductors connected to any one phase of the circuit.
3. Flexible cord used in extension cords made with separately listed and installed components shall be permitted to be supplied by a branch circuit in accordance with the following:
4. Separately installed pressure connectors shall be used with conductors at the ampacities not exceeding the ampacity at the listed and __________ temperature rating of the connector.
5. Conductors of branch circuits supplying more than one receptacle for cord-and-plug connected portable loads shall have an ampacity __________ the rating of the branch circuit.
6. Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be ________ the rating of the overcurrent device defined in 240.6.
7. Where simultaneous biplane examinations are undertaken with the X-ray units, the supply conductors and overcurrent protective devices shall be 100 percent of the __________ demand rating of each X-ray unit.
8. The grounded conductor of a 3-phase, 3-wire delta service shall have an ampacity not less than that of the ungrounded conductors.
9. Ampacity is the average current, in watts, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
10. The ampacity of branch-circuit conductors over 600 volts shall not be less than 50 percent of the designed potential load of utilization equipment that will be operated simultaneously.

Bonus Question

For central vacuum outlet assemblies, the ampacity of the connecting conductors shall not be less than the ampacity of the branch circuit conductors to which they are connected.


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Christel Hunter is director of codes and standards for Cerro Wire. Chris is a senior associate member of IAEI and serves as a board member for the Southern Nevada Chapter of IAEI, the IEEE Standards Association Standards Board, and the Las Vegas Section of IEEE. Chris also serves on NEC CMP-6 and CMP-13 and NFPA 921. Chris is a Certified Standards Professional, Master Electrician, and LEED Accredited Professional. Randy Hunter is an instructor and consultant specializing in electrical code and installations, and co-owner of Hunter Technical Services. He holds ten inspections certifications from IAEI and ICC. He is the IAEI Southern Nevada IAEI Chapter president and has been a master electrician since 1988.