NEC · Reference tables

The NEC tables the exam makes you find fast.

Open-book doesn't mean easy — the journeyman exam is a race to the right table. These are the lookups it leans on most, with how to read and apply each one.

NEC 2017 2020 2023

Key NEC tables

Ampacity, conduit fill, grounding, motor and transformer lookups.

Table
Table 310.16
Conductor ampacity at 60/75/90°C for copper and aluminum in raceway, cable, or earth
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Table 250.122
Equipment grounding conductor sizing based on OCPD rating
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Table 250.66
Grounding electrode conductor sizing based on largest service-entrance conductor
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Table 300.5
Minimum burial depth for cables and conduit by wiring method and location
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Chapter 9, Table 1
Maximum conduit fill percentages: 53% (1 conductor), 31% (2 conductors), 40% (3+ conductors)
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Chapter 9, Table 4
Conduit and tubing internal dimensions and total cross-sectional areas by trade size
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Chapter 9, Table 5
Conductor cross-sectional areas including insulation for fill calculations
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Chapter 9, Table 8
Conductor properties: circular mils, resistance per 1,000 ft, used for voltage drop
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Chapter 9, Table 9
AC resistance and reactance values used in precise voltage drop calculations
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Table 314.16(A/B)
Outlet box cubic-inch capacity and per-conductor box fill allowances
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Tables 430.248 / 430.250
Single-phase and three-phase motor full-load current for circuit sizing
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Table 430.52
Maximum rating of motor branch-circuit short-circuit and ground-fault protection by motor type
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Table 450.3(B)
Maximum overcurrent protection for dry-type transformers (secondary 600V or less)
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Table 220.12
General lighting load in volt-amperes per square foot by occupancy type
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Table 220.55
Demand factors for household electric ranges and cooking appliances
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Table 240.6(A)
Standard ampere ratings for fuses and fixed-trip circuit breakers (next-size-up rule)
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Most journeyman calculation questions resolve to a table: conductor ampacity in 310.16, conduit fill in the Chapter 9 tables, equipment grounding conductor sizing in 250.122, grounding electrode conductor sizing in 250.66, and motor full-load current in 430.248/430.250. The candidates who pass aren't the ones who memorize them — they're the ones who can find and read them in seconds.

Loomi's lookup-speed drills are built around exactly these tables, so finding the right value under time pressure becomes automatic before exam day.

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